19) United States US00RE38012E

ii) Reissued Patent (10) Patent Number: US RE38,012 E

Ochab et al.
(45) Date of Reissued Patent: Mar. 4, 2003

NY (US) 5,348,126 A 9/1994 Gao 192/7

5,845,546 A 12/1998 Knowles et al. . 74/650
(73) Assignee: Hilliard Corporation, Elmira, NY (US)
Primary Examiners aul Rodriguez
(21) Appl. No.: 09/757,400 (74) Attorney, Agent, or Firm—DiLik ei Biddle & Reath
LLP
(22) Filed: Jan. 5, 2001
(57) ABSTRACT
Related U.S. Patent Documents
Reissue of: A bi-directional overrunning clutch is disclosed for control-
(64) Patent No.: 5,971,123 ling torque transmission between a secondary drive shaft
Issued: Oct. 26, 1999 and secondary driven shafts. The overrunning clutch
Appl. No.: 09/169,847 includes a pinion input shaft in a differential housing that
Filed: Oct. 9, 1998 engages with a clutch housing rotatably disposed within the
differential housing. At least one race is located adjacent to
F16D 27/12 the clutch housing and is engaged with an output shaft. A
192/48.2; 192/38; 192/40; cage is located between the race and the clutch housing. The
192/50; 192/84.21; 74/650 cage is movable with respect to the clutch housing. A [first]
(58) Field of Search 192/48.2, 49, 50, coil is mounted within the differential housing adjacent to
192/51, 38, 40, 84.2, 84.21; 74/650 the cage and is adapted to produce an electromagnetic field
when energized which causes the cage to drag with respect
(56) References Cited to the clutch housing. The dragging of the cage with respect
to the clutch housing positions rolls within the cage to
U.S. PARENT DOCUMENTS engage the clutch housing with the race when wheels on a
1,823,389 A 9/1931 Lavaud primary drive shaft lose traction. [A] If desired a second
2,865,228 A 12/1958 Weismann 74/650 coil [is] may be mounted within the differential housing
3,124,972 A 3/1964 Seliger et al. . 74/650 adjacent [adjacent] to the cage. The second coil is adapted
3,262,526 A 7/1966 Kramer 192/38 to produce an electromagnetic field when energized which
3,447,396 A 6/1969 Seliger 76/650 advances cage with respect to the clutch housing causing the
3,581,597 A 6/1971 Reiersgaard 74/650 clutch housing to engage with the races. When the second
3,700,082 A 10/1972 Schwab 192/50 coil is activated, the output shaft drives the pinion input
3,935,753 A 2/1976 Williams 74/650
shaft producing engine braking. An electronic control
4,373,407 A 2/1983 Okubo 74/650
4,434,878 A 3/1984 Okubo 192/48.92 system is utilized to control the energising of the coils.
4,681,180 A 7/1987 Oyama et al. 180/76
4,782,720 A 11/1988 Teraoka et al. . 74/650 27 Claims, 8 Drawing Sheets

32
42 36

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U.S. Mar. 4, Sheet 1 of US RE38,012

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U.S. Mar. 4, Sheet 2 of US RE38,012

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U.S. Mar. 4, Sheet 3 of US RE38,012

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U.S. Mar. 4, Sheet 4 of US RE38,012

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U.S. Mar. 4, Sheet 7 of US RE38,012

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FIG.8
 US RE38,012
1 2
BI-DIRECTIONAL OVERRUNNING CLUTCH rotate faster than the inside wheel. Since the half shafts are
locked together, one wheel must scrub. Another problem
Matter enclosed in heavy brackets [ ] appears in the that occurs in locking differentials is twichiness when
original patent but forms no part of this reissue specifi- cornering due to the inability of the two shafts to turn at
cation; matter printed in italics indicates the additions different
made by reissue. 5 speeds.
The final type of differential is a center differential.
FIELD OF THE INVENTION These types of differentials are used in the transfer case of
The present invention relates to clutches and, more a four wheel drive vehicle to develop a torque split between
the front and rear drive shafts.
particularly, to a bi-directional electromechanical overrun- 10 Many differentials on the market today use some form of
ning clutch for providing four wheel drive capability. an overrunning clutch to transmit torque when needed to a
driven shaft. One successful use of an overrunning clutch
BACKGROUND OF THE INVENTION in an all terrain vehicle is disclosed in U.S. Pat. No.
The increased demand in recent years for off-road and all 5,036,939. In that patent, the vehicle incorporates
terrain
15
vehicles has led to tremendous developments in those overrunning clutches directly into the wheel hubs, thus
allowing each wheel to independently disengage when
types of vehicles. Many of the developments have centered required.
around making the vehicle more adaptable to changing
road conditions, e.g., dirt roads, pavement and gravel. As SUMMARY OF THE INVENTION
the road terrain changes, it is desirable to vary the driving A bi-directional overrunning clutch is disclosed for con-
capabilities 20 trolling torque transmission between a secondary drive
of the vehicle to more efficiently navigate the new terrain. shaft and secondary driven shafts. The present invention,
Prior four-wheel drive and all terrain vehicles were cum- when used in a vehicle, provides four wheel drive
bersome since they required the operator to manually capability in the event of traction loss on any primary drive
engage and disengage the secondary drive shaft, e.g., by shaft.
stopping the vehicle to physically lock/unlock the wheel The overrunning clutch includes a differential housing
hubs. 25 with a pinion input shaft extending outwardly from the
Improvements in vehicle drive trains, such as the develop- housing. One end of the pinion input shaft is engaged with
ment of automated systems for engaging and disengaging a the secondary drive shaft. The other end of the input shaft
driven axle, eliminated many of the problems of the prior is located within the differential housing and includes an
designs. These automated drive systems are sometimes input gear. The input gear preferably engages with a ring
referred to as “on-the-fly” four wheel drive. These systems,
30 gear rotatably disposed within the housing such that
however, require the vehicle to be in either 2-wheel or rotation of the input gear produces concomitant rotation of
4- wheel drive at all times. the ring gear.
Generally, all four-wheel drive vehicles include a differ- A clutch housing is attached to the ring gear and includes
ential for transferring torque from a drive shaft to the driven an inner cam surface. At least one and preferably two races
shafts that are attached to the wheels. Typically, the driven 35 are located adjacent to the cam surface. Each race is
shafts (or half shafts) are independent of one another allow- engaged with an output shaft. The output shaft, in turn, is
ing differential action to occur when one wheel attempts to engaged with a secondary driven half shaft.
rotate at a different speed than the other, for example when A roll cage is located between the race and the cam
the vehicle turns. The differential action also eliminates tire surface. The roll cage has a plurality of slots which are
scrubbing, reduces transmission loads and reduces under- 40 preferably spaced equidistantly about its circumference.
steering during cornering (the tendency to go straight in a Each slot has a roll located therein. The roll cage is
corner). There are four main types of conventional differ- movable with respect to the clutch housing and the races.
entials: open, limited slip, locking, and center differentials.
A first armature plate is located adjacent to and engaged
An open differential allows differential action between the
with the roll cage so that the first armature plate rotates in
half shafts but, when one wheel loses traction, all available 45
conjunction with the roll cage. A [first] coil is mounted
torque is transferred to the wheel without traction resulting
within the differential housing adjacent the first armature
in the vehicle stopping.
plate. The [first] coil is adapted to produce an electromag-
A limited slip differential overcomes the problems with netic field when energized which hinders the rotation of the
the open differential by transferring all torque to the wheel first armature plate, thus causing the roll cage to drag with
that is not slipping. Some of the more expensive limited slip 50 respect to the clutch housing. The dragging of the roll cage
differentials use sensors and hydraulic pressure to actuate with respect to the clutch housing causes the rolls to engage
the clutch packs locking the two half shafts together. The the clutch housing and the race when the wheels on the
benefits of these hydraulic (or viscous) units are often primary drive shaft lose traction. When traction loss occurs,
overshadowed by their cost, since they require expensive the rolls become wedged between the clutch housing and
fluids and complex pumping systems. The heat generated in 55 the races so as to provide driving engagement
these systems, especially when used for prolonged periods therebetween.
of time may also require the addition of an auxiliary fluid
[A] In one embodiment, a second armature plate is
cooling source.
located adjacent the roll cage. A second coil is mounted
The third type of differential is a locking differential that within the differential housing adjacent to the second
armature plate.
uses clutches to lock the two half shafts together or incor- 60 The second coil is adapted to produce an electromagnetic
porates a mechanical link connecting the two shafts. In field when energized to hinder the rotation of the second
these types of differentials, both wheels can transmit torque armature plate. This causes the roll cage to advance with
regardless of traction. The primary drawback to these types respect to the clutch housing causing the clutch housing to
of differentials is that the two half shafts are no longer engage with the races. In this mode of operation, the
independent of each other. As such, the half shafts are 65 secondary driven half shafts and output shaft drive the
either locked or unlocked to one another. This can result in pinion input shaft and secondary drive shaft, thereby pro-
problems during turning where the outside wheel tries to ducing engine braking.
 US RE38,012
3
In another embodiment, a third armature plate is located
4
12, a primary drive shaft 14 a primary differential 16, and
adjacent to the roll cage and a third coil is mounted within first and second primary driven shafts 18, 20 which drive
the differential housing adjacent to the third armature plate. primary wheels 22.
The third coil produces an electromagnetic field when The drive system also includes a secondary drive shaft 24
energized which hinders the rotation of the third armature 5 which is rotatably connected to the bidirectional overrun-
plate. This causes the roll cage to move opposite the ning clutch 10 through any conventional means known to
direction of rotation of the clutch housing to assist in those skilled in the art, such as a splined connection. The
disengaging the rolls from between the clutch housing and overrunning clutch 10, in turn, rotatably drives two second-
the races. ary driven shafts 26, 28 which are attached to wheels 30.
The clutch housing preferably has a plurality of toggle 10
The details of the bi-directional overrunning clutch will
levers pivotally attached thereto that engage with pins now be described with respect to FIGS. 2 through 5. FIG. 2
mounted on the roll cage. The engagement between the illustrates the right cover 52 of the bi-directional overrun-
toggle levers and the pins permits the roll cage to be ning clutch 10. The secondary drive shaft 24 engages with
advanced and retarded with respect to the clutch housing. a splined end of a pinion input shaft 32. The pinion input
The second armature plate engages with the toggle lever to 15
shaft 32 extends out from and is rotatable with respect to a
advance the cage and the third armature plate engages with differential housing 34. More specifically, the pinion input
the toggle lever to retard the cage. shaft 32 is located within a bearing assembly 36 that
The foregoing and other features and advantages of the includes two roller bearings 38 within a bearing support 40.
present invention will become more apparent in light of the The pinion input shaft 32 is positioned against the inner
following detailed description of the preferred race
embodiments thereof, as illustrated in the accompanying 20
of the two roller bearings 38. The outer races of the bearings
figures. 38 lie against the bearing support 40. An oil seal 42 is also
located between the bearing support 40 and the pinion input
BRIEF DESCRIPTION OF THE DRAWINGS shaft 32. The oil seal 42 prevents oil from escaping out of
For the purpose of illustrating the invention, the the bearing assembly 36. The bearing assembly 36 is
drawings show a form of the invention which is presently mounted
25
preferred. However, it should be understood that this within the differential housing 34 by any conventional
invention is not limited to the precise arrangements and means. A rubber O-ring 44 is located between the bearing
instrumentalities shown in the drawings. assembly 36 and the differential housing 24 to provide a
FIG. 1 is a schematic representation of one drive train fluid tight seal.
embodiment in a vehicle incorporating the present inven- The pinion input shaft 32 preferably has a bevel gear 46
30 formed on or attached to the end of the shaft 32 located
tion.
within the differential housing 34. The bevel gear is prefer-
FIG. 2 is a right side view of one embodiment of the bi-
ably made from steel material with spiral bevels. The bevel
directional overrunning clutch according to the present
gear 46 engages with a ring gear 48 located within the
invention.
differential housing 34. The ring gear 48 is preferably made
35 from steel with spiral bevels. In one embodiment of the
FIG. 3 is cross-sectional view of the bidirectional over-
running clutch taken along lines 3-3 in FIG. 2. invention, the ring gear 48 and bevel gear 46 both have
FIG. 4 is a cross-sectional view of the bi-directional mating 35° spiral bevels. Those skilled in the art would
overrunning clutch taken along lines 4-4 in FIG. 3. appreciate that other angles can be used in the present
FIG. 5 is an exploded view of the bi-directional overrun- invention depending on the design of the entire clutch
40 system and the anticipated loading. Furthermore, it is con-
ning clutch shown in FIGS. 2-4.
templated that other gearing arrangements, such as a worm
FIG. 6A is a schematic cross-sectional view of a roll
gear set, may be used for engaging the pinion input shaft 32
cage in a non-activated position.
to the differential housing 34.
FIG. 6B is a schematic cross-sectional view of the roll
cage in a first position. 45 The ring gear 48 is preferably bolted to a clutch housing
50 which will be described in more detail hereinafter. A
FIG. 6C is a schematic cross-sectional view of the roll right cover plate 52 is located adjacent to the ring gear
cage in an engaged position wherein the pinion input shaft 48 and
drives the output shafts. attached to the differential housing 34 though any conven-
FIG. 6D is a schematic cross-sectional view of the roll tional means, such as bolts. A thrust bearing 54 and thrust
cage in a second position wherein the output shafts drive 50 washer 56 are located between the right cover plate 52 and
the pinion input shaft. the ring gear 48. The thrust bearing 54 is in rolling contact
FIG. 7 is a cross-sectional view of a second embodiment with the ring gear 48 and, in one embodiment, is a NTA-
of the bi-directional overrunning clutch showing use of 6074 Torrington thrust bearing, sold by Torrington Co.,
toggle levers for controlling the roll cage. Torrington, Conn. The thrust washer 56 is located between
FIG. 8 is a cross-sectional view of the second 55 the thrust bearing 54 and the right cover plate 52 and is
embodiment of the bi-directional overrunning clutch preferably made from steel. One suitable thrust washer is a
shown in FIG. 7. TRB-6074 Torrington thrust washer sold by Torrington Co.
The thrust bearing 54 and washer 56 combination allow the
DETAILED DESCRIPTION OF THE ring gear 48 to freely rotate within differential housing 34.
EMBODIMENTS 60 A rubber O-ring 58 is preferably positioned between the
right cover plate and the differential housing 34 to provide
Referring now to the drawings, wherein like reference
a fluid tight seal.
numerals illustrate corresponding or similar elements
throughout the several views, FIG. 1 is a schematic repre- A bushing 60 is mounted between the clutch housing 50
sentation of one embodiment of a drive system and the differential housing 34, permitting the clutch hous-
incorporating a bidirectional overrunning clutch 10 65 ing 50 to freely rotate within the differential housing 34.
according to the present invention. The drive system The bushing 60 is preferably a self-lubricating bushing
includes a transmission made from composite material. One suitable type of
bushing is an
 US RE38,012
5 6
MB 8540DU DU bearing sold by Garlock Bearing Inc., output shaft 78 and engages with the left cover plate 94. An
Thorofare, N.J. The clutch housing 50 is preferably made oil seal 98 is preferably incorporated into the left cover
from steel material and has an inner cam surface which is plate 94 around the output shaft 78 to provide a fluid tight
discussed in more detail below. A roller assembly 62 is seal. The left cover plate 94 is attached to the differential
located within the clutch housing 50 and includes a roll housing
cage 64 which contains a plurality of rolls 66. The roll cage 5 34 by any conventional means, such as bolts. A rubber O-
64 preferably includes two independent sets of rolls 66 dis- ring 100 is preferably inserted between the left cover plate
posed within slots 68 formed in the roll cage 64 around its 94 and the differential housing 34.
circumference. In the illustrated embodiment there are six
To assist in aligning the two output shafts 78, one of the
output shafts 78 preferably includes a raised protrusion 102
rolls in each set of rolls. The roll cage 64 is preferably made 10 which mates with a recess 104 formed in the other output
from hard anodized aluminum material. Alternatively, the shaft 78. A bushing 106 can be placed on the protrusion
roll cage 64 can be made from plastic or composite 102 or in the recess 104 to facilitate relative motion
material. The rolls are preferably made from hardened steel between the two shafts.
material.
The output shafts 78 extend outward from the differential
A wire spring 70 retains the rolls 66 within the slots 68 of
the roll cage 64. The wire spring 70 is disposed within a 15 housing 34 and connect to secondary half shafts which
groove 72 formed on the inner surface of the roll cage 64 and drive the vehicle’s wheels 30. Each output shaft 78 is
within depressions 74 formed in the rolls 66. connected to a secondary half shaft through any
Each set of rolls 66 is located adjacent to the inner cam conventional means known to those skilled in the art, such
surface of the clutch housing 50. The contour of the cam as a splined connec- tion. (For the sake of simplicity, the
surface is shown in more detail in FIGS. 6A through 6D and 20 output shafts 78 and two half shafts are collectively
is configured with a plurality of peaks and valleys. When the referred to herein as the second- ary driven shafts 26, 28.)
roll cage 64 is located within the clutch housing 50, the rolls As discussed briefly above, the engagement of the rolls
66 are located within the valleys with the cam surface 66 with the clutch housing 50 and races 76 permits the
tapering toward the race on either side of the roll 66 transfer of torque from the secondary drive shaft 24 to the
(generally referred to herein as tapered portions 502). The 25 secondary driven shafts 26, 28. In order to activate the
cam surface and rolls 66 provide the bi-directional overrun- overrunning clutch, the present invention incorporates an
ning capabilities as will be discussed hereinafter. Cam electromag- netic system. More specifically, the present
surfaces and roll cages in overrunning clutches are well invention includes two and more preferably three roll cage
known in the art. See, e.g., U.S. Pat. No. 4,373,407, which adjustment devices which are electrically connected to an
is incorporated herein by reference in its entirety. Hence, a 30 electronic control system. In one preferred embodiment, the
detailed discussion of these features is not needed. roll cage adjustment devices include a plurality of coils and
At least one and preferably two races 76 are rotatably armature plates. The coils and armature plates are mounted
located in the center of the roll cage 64. Each race 76 is within the differential housing 34 to control the movement
adjacent one of the sets of rolls 66 such that the outer of the roll cage 64 with respect to the clutch housing 50.
surface A first coil 108 is located within a coil insert 110 which
of the race 76 contacts the set of rolls 66. As will become 35 is mounted to the right cover plate 52. The coil insert 110 is
evident hereinafter, the contact between the rolls 66, the preferably made from a metallic material, such as steel or
clutch housing 50 and the races 76 causes the races 76 to powdered metal, and is press fit or similarly attached to the
rotate with the clutch housing 50. The races 76 are prefer- housing. The first coil 108 is preferably annular in shape
ably made from steel material. A thrust bearing 77 is with a central axis coincident with the axis of rotation of
disposed between the two races 76 to allow the races 76 to 40 the roll cage 64. The first coil 108 is preferably a bobbin
freely rotate with respect to one another. The thrust bearing wound coil which includes a plastic base about which the
77 is preferably an NTA-1828 Torrington thrust bearing coil is wound. Suitable coils for use in the present invention
sold by Torrington Co. are well known to those skilled in the electric clutch art.
Each race 76 is engaged with a corresponding output shaft One satisfactory coil is disclosed in U.S. Pat. No.
78 through any conventional means designed to transfer 45 5,036,939, which is incorporated by reference herein in its
torque from the race 76 to the output shaft 78. In the entirety. Other suitable coils are available from Endicot
illustrated embodiment, each race 76 includes internal Coil Co., Inc. Endicot, N.Y. The first coil 108 is bonded or
splines 80 which mate with external splines 82 formed on a otherwise attached to the coil insert 110.
portion of the output shaft 78. The splined arrangement A first armature plate 112 is located between the first
illustrated permits the output shaft 78 to be removed by 50 coil 108 and the roll cage 64. The first armature plate 112 is
sliding it axially out of the race 76. A shoulder 84 formed on preferably annular in shape and is free to rotate with respect
the output shaft 78 limits the axial translation of the output to the first coil 108 when the coil is not energized. The first
shaft 78 into the race 76. The output shaft is preferably made armature plate 112 includes at least one and, more
from steel material. It is contemplated that the race 76 and preferably at least three tangs or fingers 114 which protrude
output shaft 78 can be formed as an integral unit if desired. 55 from the armature plate 112 toward the roll cage 64. The
One of the output shafts 78 (i.e., the right output shaft) tangs 114 engage with slots 116 formed in the roll cage 64.
extends out of an opening 86 formed in the right cover plate The first armature plate 112 is locked to the roll cage 64
52. A roller bearing 88 surrounds a portion of the output when the tangs 114 are engaged with the slots 116. Hence,
shaft 78 and engages with the right cover plate 52. The roller when the first coil 108 is not energized, the first armature
bearing 88 supports the output shaft 78 while permitting the 60 plate 112 rotates with the roll cage 64. The first armature
plate 112 is preferably made from steel material.
output shaft 78 to rotate with respect to the right cover plate
52. An oil seal 90 is preferably incorporated into the right When the first coil 108 is energized, an electromagnetic
cover plate 52 around the output shaft 78 to provide a fluid
tight seal between the two components.
Similarly, the other output shaft 78 (i.e., the left output 65 field is generated between the first coil 108 and the first
shaft) extends out of an opening 92 formed in a left cover armature plate 112 attracting the first armature plate 112 to
plate 94. A roller bearing 96 surrounds a portion of the the first coil 108 causing it to drag. Since the first armature
 US RE38,012
7 8
plate 112 is engaged with the roll cage 64, the dragging of field is generated that inhibits or limits rotation of the third
the first armature plate 112 causes the roll cage 64 to also armature plate 136. As the clutch housing 34 continues to
drag or retard. In an alternate embodiment (not shown), the rotate, the tangs 140 on the third armature plate 136 contact
tangs 114 on the armature plate 112 do not engage with slots the forked ends of the toggle levers 120 causing the toggle
116 formed in the roll cage 64. Instead, the tangs 114 engage 5 levers 120 to pivot about the dowel pins 118 in a direction
with protrusions formed on the roll cage 64 when the first opposite from the direction of pivoting caused by the
coil 108 is energized. second coil 124. The pivoting of the toggle levers 120
Referring to FIGS. 4 and 5, the left side of the clutch result in the roll cage 64 moving in the opposite direction
housing 50 is shown with a plurality of dowel pins 118 from the direction of rotation of the clutch housing 50.
extending outward from the clutch housing 50. A toggle 10 The coils 108, 124, 126 are connected to a electronic
lever 120 is pivotally mounted to each dowel pin 118. Each control system, such as a signal processor for controlling
toggle lever 120 includes a fork at a radially inward end the energising of the coils. (The electronic control system is
120a that is designed to engage with a cage pin 122 generally identified by the numeral 142 in FIG. 5.)
mounted on the roll cage 64. Pivoting of the toggle levers The operation of the bi-directional overrunning clutch
120 about will now be discussed. Under normal operation (two-wheel
the dowel pins 118 causes the forked ends 120a to urge the 15 drive mode), the electronic control system 142 does not
roll cage 64 to move (i.e., advance or retard) with respect to send any signals to energize the coils. Accordingly, the
the clutch housing 50. As such, the engagement and disen- vehicle is propelled by the primary drive shaft 14 and
gagement of the rolls 66 can be controlled by manipulating primary driven shafts 18, 20. The secondary drive shaft 24
the toggle levers 120. The radially outward end of each rotates the pinion input shaft 32 which drives the ring gear
toggle lever 120 preferably includes an outer projection 20 48. The ring gear
120a as shown in the figure. The toggle levers 120 are 48 rotates the clutch housing 50 within the differential
preferably made from steel material and have a stepped housing 34. Since the coils are not energized, the springs
thickness that varies from approximately °/isth inch to '/isth 70 maintain the roll cage 64 in a relatively central or
inch. The dowel pins 118 are preferably made from steel unengaged position (non-activated position). This position
material. The cage pins 122 are also preferably made from 25 is best illus- trated in FIG. 6A. In this position, the rolls 66
steel material. are not wedged between the races 76 and the tapered
In order to control the pivoting of the toggle levers 120, portion 502 of the cam surface of the clutch housing 50
the present invention incorporates second and third coils and, therefore, there is no driving engagement between the
124, 126 as shown in FIGS. 4 and 5. The second coil 124 is clutch housing 50 and the races 76. Instead, the rolls 66 and
mounted within a second coil insert 128 which, in turn, is 30 roll cage 64 rotate with the clutch housing 50, independent
mounted to the left cover plate 94. The second coil 124 from the output shafts
preferably has an annular shape and is mounted to the left 78. In this mode of operation, the secondary driven shafts
cover plate 94 on a central axis which is coincident with the 26, 28 do not drive the wheels but, instead, are driven by
axis of rotation of the clutch housing 50. A second armature the wheels 30.
plate 130 is located between the second coil 124 and the 35 When it is desired to operate the vehicle such that four
toggle levers 120. The second armature plate 130 is prefer- wheel drive is available when needed (four-wheel drive
ably annular in shape and has a plurality of tangs 132 formed capability mode), the electronic control system 142 is acti-
thereon that extend toward the toggle levers 120. The tangs vated. Preferably, the activation is provided by manually
132 are designed to contact or engage with the outer actuating a button on the vehicle console, although the
projections 120a on the toggle levers 120. When the second 40 system can be automatically activated if desired. The elec-
coil 124 is energized, a magnetic field is generated that tronic control system 142 sends a signal to energize the
inhibits or limits the rotation of the second armature plate first coil 108. (The second coil 124 and third coil 126 are
130 (i.e., causing it to drag). As the clutch housing 50 not energized in this mode of operation.) The energising of
continues to rotate, the tangs 132 on the second armature the first coil 108 creates an electromagnetic field between
plate 130 contact the outer projections 120a on the toggle 45 the first coil 108 and the first armature plate 112. The
levers 120 urging the toggle levers 120 to pivot about the electro- magnetic field causes the first armature plate 112
dowel pins 118. This causes the forked ends 120a of the to drag or slow in speed. Since the first armature plate 112
toggle levers 120 to advance the roll cage 64. As will be is engaged to the roll cage 64 by the tangs 114, the
electromagnetic field causes the roll cage 64 to slow with
discussed in more detail below, the advancement of the roll
cage 64 causes the rolls 66 to wedge between the tapered 50 respect to the clutch housing 50 into a first position. In this
position (shown in FIG. 6B), the rolls 66 are located near to
portions 50a of the cam surface and the races 76. The second but not wedged between the tapered portion 50a of the cam
and third coils 124, 126 are preferably similar to the first coil surface and the races 76. Instead, the difference in
108, and the second and third coil inserts 128, 134 are rotational speed between the secondary drive shaft 24 and
preferably similar to the first coil insert 110. the output shafts 78 maintains the rolls 66 in an
Similar to the second coil 124, the third coil 126 is 55 overrunning mode. As such, the vehicle continues to
mounted within a third coil insert 134 which is concentri- operate in two-wheel drive (i.e., driven by the primary
cally disposed within the second coil insert 128 and mounted drive shaft 14).
to the left cover plate 94. The third coil 126 is preferably
When the wheels 22 driven by the primary drive shaft 14
annular in shape with a central axis that is coincident with
begin to slip, the rotational speed of the secondary drive
shaft 24 and the output shafts 78 begin to equalize relative
the axis of rotation of the clutch housing 50. A third 60 to the ground, since ground speed controls four-wheel drive
armature plate 136 is located between the third coil 126 and and overrunning engagement. As such, the clutch housing
the toggle levers 120, and is substantially concentric with 50 starts to rotate faster than the output shafts 78 and races
the second armature plate 130. The third armature plate 136 76. This change in relative speed between these
preferably has a plurality of tangs 140 formed thereon that components causes the rolls 66 to wedge between the
extend toward the toggle levers 120 and are configured to races 76 and the
contact or engage with a portion of the forked ends 120a of 65 tapered portion 502 of the cam surface (as shown in FIG.
the toggle levers 120. When the third coil 126 is energized, 6C). As a result, torque is transmitted from the clutch
a magnetic housing 50 to the races 76 and the vehicle is now operating
 US RE38,012
9 1
in four-wheel drive (i.e., the primary driven shafts 18, 20 108 inhibits or hinders the rotation of the first armature plate
and secondary driven shaft 26, 28 are driving the wheels 112. Since the tangs 114 on the first armature plate 112 are
22, 30). The drive system will stay in four-wheel drive until engaged with the slots 116 in the roll cage 64, energising
the wheels 22 on the primary drive shaft 14 stop slipping, the first coil causes the rolls 66 to disengage from between
at which point the output shaft 78 once again overruns the the
clutch housing 50 and rolls 66 disengage. The ability of the 5 races 76 and the tapered portions 502 of the cam surface.
present invention to engage and disengage the secondary
driven shafts when needed allows the system to provide It is contemplated that when in the backdriving mode,
immediate four-wheel drive capability in both forward and situations may arise where the electromagnetic field pro-
duced by the first coil 108 may not be sufficient to
disengage the rolls 66 from between the races 76 and
the tapered
rear directions. 10 portions 50a of the cam surface. In order to assist in
Another feature of the bi-directional overrunning clutch disengagement, the electronic control system 142 also ener-
10 according to the present invention is that, even when the gizes the third coil 126. This causes an electromagnetic
vehicle is operating in four-wheel drive capability mode, field to form which inhibits or limits the rotation of the
i.e., when torque is transmitted to the secondary driven third armature plate 136. The tangs 140 on the third
shafts 26, 28, the sets of rolls 66 can independently disen- 15 armature plate 136 contact the forked end 120a of the
gage (overrun) from the clutch housing 50 when needed, toggle lever 120 providing additional leverage to pivot the
such as when the vehicle enters into a turn and the wheel on toggle lever 120 around the dowel pin 118. Depending on
one secondary driven shaft 26 rotates at a different speed the configuration of the system, it may be desirable to add a
than the wheel on the other secondary driven shaft 28. As fourth coil and a second toggle system to the right side of
such, the overrunning clutch 10 provides the drive system 20 the clutch housing 50 adjacent to the first coil 108 to
with the advantages of an open differential in cornering provide additional release leverage.
without traction loss, and the advantages of a locking While one preferred embodiment of the invention has
differential when in four-wheel drive without the disadvan- been described with coils and armature plates as the roll
tages of understeering and tire scuffing when cornering. cage adjustment devices, those skilled in the art, in light of
The present invention also provides engine braking capa- 25 the teachings provided herein, would understand how to
bility (backdriving mode) for use when driving the vehicle modify the invention to incorporate other mechanical,
down steep inclines. In the backdriving mode, the secondary electrical, hydraulic or pneumatic devices in place of the
driven shafts 26, 28 are engaged with the secondary drive coils and or armature plates.
shaft 24 and actually drive the secondary drive shaft 24. This
It is also contemplated that the cam surface need not be
is important since the front wheels generally have better 30
traction than the rear wheels when the vehicle is descending formed on the clutch housing but, instead, can be formed
down a steep slope in a forward direction. The present on the races. Also, the roller clutch described above can be
invention takes advantage of this occurrence and engages easily modified to use sprags instead of rolls. A person
the front wheels (via the secondary driven shafts 26, 28 and skilled in the art could readily make these substitutions in
output shafts 78) with the secondary drive shaft 24 (via the 35 light of the above teachings.
clutch housing 50 and pinion input shaft 32) such that front A second embodiment of the invention is shown in
wheels control the rotation of the secondary drive shaft 24. FIGS. 7 and 8 wherein a toggle system is incorporated into
This produces engine braking, thereby assisting in slowing the right side of the differential housing 34. In this
down the vehicle. embodiment, the tangs 114 on the first armature plate 112
The backdriving mode is controlled either by a traction 40 do not engage with slots 116 formed in the roll cage 64.
sensor (not shown) which sends a signal to the electronic Instead, at least one, and more preferably three, toggle
control system 142, or manually engaged by the operator of levers 200 which are pivotally mounted to the clutch
the vehicle depressing a button (not shown) in the vehicle housing 50 and engaged with the roll cage 64 for causing
which sends a signal to the electronic control system 142. the roll cage 64 to advance and retard.
The electronic control system 142 then energizes the second 45 More particularly, each toggle lever 200 has an inner end
coil 124. (The first and third coils 108, 126 are not 200a and an outer end 200a. The outer end 200a is pivotally
energized in this mode.) This creates a magnetic field that mounted to the clutch housing 50 via a dowel pin 202. The
causes the second armature plate 130 to slow or drag. The toggle lever 200 also has a slotted opening 204 located
tangs 132 on the second armature plate 130 contact the approximately midway along its length. The slotted
outer projections opening 204 is sized to slidingly engage with a protruding
120a on the toggle levers 120 as the clutch housing 50 50 pin 206 which extends outward from a flange 208. The
rotates causing the toggle levers 120 to pivot about the flange 208, in turn, is mounted to the roll cage 64 by pins
dowel pins 118. As the toggle levers 120 pivot, the forked 210. Since the flange 208 is pinned to the roll cage 64, it
ends 120a of the toggle lever 120 urge the roll cage 64 to rotates with it. Furthermore, since the toggle levers 200 are
advance. This results in the rolls 66 becoming wedged pivotally attached to the clutch housing 50 and slidingly
between the races 76 and the tapered portion 502 of the cam 55 engaged with the protruding pins 206, the roll cage 64
surface on the clutch housing 50 (as shown in FIG. 6D). As rotates with the clutch housing 50
such, the wheels 30 on the secondary driven shafts 26, 28 are The first armature plate 112 in this embodiment is con-
directly connected to the secondary drive shaft 24 and figured with its tangs 114 located adjacent to the inner ends
become the input to the gear box locking the entire gear train 200a of the toggle levers 200, similar to the third armature
together. In this mode, both front wheels are engaged. 60 plate 136.
When in the backdriving mode, it is necessary to disen- The operation of this embodiment of the overrunning
gage the rolls 66 from between the races 76 and the tapered clutch is similar to the first embodiment described above.
portions 50a of the cam surface when the vehicle is no When it is desired to place the vehicle in four-wheel drive
longer descending the hill. In order to accomplish the capability mode, the first coil 108 is activated causing the
disengagement, the electronic control system 142 de- 65 armature plate 112 to drag. As the armature plate 112 drags
energizes the second coil 124 while energising the first coil its tangs 114 contact the inner ends 200a of the toggle
108. The electromagnetic field generated by the first coil levers 200 causing the levers to pivot about the dowel pins
202. As
 US RE38,012
1 1
the toggle levers 200 pivot, they force the protruding pins 4. An overrunning clutch according to claim 2 wherein
206 to retard the roll cage 64. This places the rolls 66 in the clutch housing has a plurality of toggle levers pivotally
position to wedge between the clutch housing 50 and the mounted thereon, each toggle lever engaged with the roll
races 76 when the primary drive shaft loses traction. When cage, the first armature plate adapted to pivot the toggle
the first coil 108 is deactivated, the armature plate 112 is 5 levers when the first coil is energized to retard the roll cage.
once again free to move. The natural motion of the wheels 5. An overrunning clutch according to claim 2 wherein
will cause the rolls 66 to disengage from between the clutch the first armature plate includes tangs which engage with
housing 50 and the races 76. slots formed in the roll cage.
As discussed above, the first coil 108 is also activated 6. An overrunning clutch according to claim 2 further
when it is desired to disengage the rolls 66 after 10 comprising a second electromagnetic adjustment device
engagement in the back driving mode. In this situation, the mounted within the differential housing, the second electro-
activation of the first coil 108 causes the first armature magnetic adjustment device adapted to place the roller
plate 112 to drag. The tangs 114 on the armature plate 112 clutch in its second position when energized; and wherein
engage the inner ends 200a of the toggle levers 200 and the second adjustment device includes a second coil which
urge them backward,
out of their advanced position. This causes the roll cage 64 15 when energized advances the roll cage with respect to the
to pull the rolls 66 out from engagement between the clutch clutch housing.
housing 50 and the races 76. 7. An overrunning clutch according to claim 6 wherein
Other embo diments of the inve ntio n are also the second electromagnetic device further includes a
contemplated, such as mounting the three coils on the same second armature plate disposed between the coil and the
side of the differential housing 34. Hence, the exemplary roll cage,
embodiments described above should not be considered as 20 the energising of the second coil adapted to cause the
limiting the full scope of the invention set forth in the second armature plate to advance the roll cage so that the
claims below. roller clutch is in its second position.
Although the invention has been described and 8. An overrunning clutch according to claim 7 wherein
illustrated with respect to the exemplary embodiments the clutch housing has a plurality of toggle levers pivotally
thereof, it should be understood by those skilled in the art 25 mounted thereon, each toggle lever engaged with the roll
that the foregoing and various other changes, omissions and cage, the second armature plate adapted to pivot the toggle
addi- tions may be made therein and thereto, without levers when the second coil is energized to advance the roll
parting from the spirit and scope of the present invention. cage.
We claim: 9. An overrunning clutch according to claim 8 wherein the
1. An overrunning clutch for controlling torque transmis- 30 third adjustment device includes a third coil which when
sion between a pinion input shaft and at least one output energized pivots the toggle levers to retard the roll cage, the
shaft, the clutch comprising retarding of the roll cage moving the roller clutch out of its
a differential housing; second position.
10. An overrunning clutch according to claim 1 wherein
a pinion input shaft having an end rotatably disposed
35 the overrunning clutch is mounted to a vehicle, the vehicle
within the differential housing;
including a drive shaft and two half shafts, each half shaft
at least one output shaft having an end rotatably having a wheel engaged therewith, the overrunning clutch
disposed within the differential housing; including two output shafts, each output shaft being rotat-
a roller clutch disposed within the differential housing ably engaged with a half shaft, the pinion input shaft being
and adapted to control torque transmission between 40 rotatably engaged with the drive shaft, and an electronic
the pinion input shaft and the at least one output shaft, control system for controlling the electromagnetic adjust-
the roller clutch having a first position wherein the ment [devices] device.
roller clutch is positioned to engage the pinion input 11. An overrunning clutch according to claim 1 further
shaft to the at least one output shaft to permit torque comprising a second electromagnetic adjustment device
transmis- sion from the pinion input shaft to the at 45 mounted within the differential housing, the second electro-
least one output shaft, and a second position wherein magnetic adjustment device adapted to place the roller
the roller clutch engages the pinion input shaft with clutch in its second position when energized; and a third
the at least one output shaft to permit torque electromagnetic adjustment device mounted within the dif-
transmission from the at least one output shaft to the ferential housing, the third electromagnetic adjustment
pinion input shaft; and 50 device adapted to disengage the roller clutch from its
a first electromagnetic adjustment device mounted second position when the third electromagnetic device is
within the differential housing, the first activated.
electromagnetic device adapted to place the roller 12. A bi-directional overrunning clutch for controlling
clutch in its first position when energized[; and torque transmission between a pinion input shaft and at
least one output shaft, the clutch comprising
a second electromagnetic adjustment device mounted 55 a differential housing;
within the differential housing, the second electromag- a pinion input shaft having an end rotatably disposed
netic adjustment device adapted to place the roller within the differential housing, the pinion input shaft
clutch in its second position when energized]. adapted to rotate an input gear located within the
2. An overrunning clutch according to claim 1 wherein the differential housing;
roller clutch includes a clutch housing and a roll cage, and 60
wherein the first adjustment device includes a first coil a ring gear disposed within the housing and rotatably
which when energized drags the roll cage with respect to the engaged with the input gear;
clutch housing. a clutch housing attached to the ring gear and rotatably
3. An overrunning clutch according to claim 2 wherein the disposed within the differential housing, the clutch
first electromagnetic device further includes a first armature 65 housing having a cam surface formed on one side;
plate for engaging the roll cage, the energising of the first at least one race disposed adjacent to the cam surface
coil adapted to cause the armature plate to drag the roll cage. and engaged with an output shaft;
 US RE38,012
1 1
a roll cage disposed between the race and the cam equidistant around the clutch housing, each toggle lever
surface, the roll cage including a plurality of slots includes an inner forked end which mates with a
formed in and spaced circumferentially about the roll correspond- ing pin formed on the roll cage, the pin being
cage, each slot having a roll located therein, the roll capable of moving within the forked end of the toggle
cage movable with respect to the clutch housing and lever.
the at least one race; 5 20. Abi-directional overrunning clutch according to claim
a first armature plate located adjacent to the roll cage; 12 further comprising a second armature plate located
and a first coil mounted within the differential housing adjacent to the roll cage; a second coil mounted within the
adja- cent to the first armature plate, the first coil differential housing adjacent to the second armature plate,
adapted to produce an electromagnetic field when the second coil adapted to produce an electromagnetic
energized which hinders the rotation of the first field
armature plate causing the roll cage to drag with respect 10 when energized which hinders the rotation of the second
to the clutch housing[; armature plate and causes the roll cage to advance with
a second armature plate located adjacent to the roll cage; respect to the clutch housing, the advancement of the roll
and
cage with respect to the clutch housing adapted to cause
a second coil mounted within the differential housing the clutch housing to drivingly engage with the at least
adjacent to the second armature plate, the second coil one
adapted to produce an electromagnetic field when
15 race; a third armature plate located adjacent to the roll cage;
ener- gized which hinders the rotation of the second
armature plate and causes the roll cage to advance and a third coil mounted within the differential housing
with respect to the clutch housing, the advancement of adjacent to the third armature plate, the third coil adapted
the roll cage with respect to the clutch housing to produce an electromagnetic field when energized which
adapted to cause the clutch housing to drivingly hinders the rotation of the third armature plate and causes
engage with the at least one race]. the
13. Abi-directional overrunning clutch according to 20 roll cage to retard with respect to the clutch housing, the
claim retarding of the roll cage with respect to the clutch housing
12 wherein the dragging of the roll cage with respect to the adapted to disengage the driving engagement between the
clutch housing positions the rolls so as to permit rotatable clutch housing and the at least one race.
engagement between the at least one race and the clutch 21. Abi-directional overrunning clutch according to claim
housing for transmitting torque from the pinion input shaft 25 20 further comprising at least one toggle lever pivotally
to the output shaft when the output shaft rotates at a speed mounted to the clutch housing, the at least one toggle lever
substantially equal to the pinion input shaft. engaged with the roll cage such that pivoting of the at least
14. Abi-directional overrunning clutch according to one toggle lever causes the roll cage to move with respect
claim 12 further comprising at least one toggle lever to the clutch housing; and wherein the third armature plate
pivotally mounted to the clutch housing, the at least one 30 retards the roll cage by urging the at least one toggle lever
toggle lever engaged with the roll cage such that pivoting to pivot.
of the at least one toggle lever causes the roll cage to move 22. Abi-directional overrunning clutch according to
with respect to the clutch housing; and wherein the first claim 21 wherein there are a plurality of toggle levers
armature plate retards the roll cage by urging the at least pivotally mounted to the clutch housing, each toggle lever
one toggle lever to pivot. having a
15. Abi-directional overrunning clutch according to 35 first end which is engaged with the roll cage and an outer
claim 12 wherein the first armature plate includes tangs projection formed on an end of the toggle lever on the
which engage with slots formed in the roll cage. opposite side of the pivotal attachment from the first end,
16. Abi-directional overrunning clutch according to and wherein the second armature plate has a plurality of
claim 12 wherein the advancement of the roll cage with tangs formed thereon which project toward the roll cage,
respect to the clutch housing rotatably engages the at least the
one race to the clutch housing such that the output shaft is 40 second armature plate positioned within the differential
drivingly engaged with the pinion input shaft. housing so that the tangs are radially aligned with the outer
17. Abi-directional overrunning clutch according to projections on the toggle levers and adapted to contact the
claim outer projections when the second coil is energized, the
12 further comprising a second armature plate located contact between the tangs and the outer projections adapted
ad jacent to the roll cage; a second coil mounted within the 45 to cause the toggle lever to pivot.
differential housing ad jacent to the second armature plate, 23. A vehicle having four wheel drive capability com-
the second coil adapted to produce an electromagnetic prising:
field a transmission;
a primary drive shaft rotatably driven by the transmission;
when energized which hinders the rotation of the second 50
armature plate and causes the roll cage to advance with two primary half shafts rotatably engaged with the pri-
respect to the clutch housing, the advancement of the roll mary drive shaft, each primary half shaft engaged with
cage with respect to the clutch housing adapted to cause the a corresponding primary wheel;
clutch housing to drivingly engage with the at least one a secondary drive shaft rotatably engaged with the trans-
race; at least one toggle lever pivotally mounted to the 55 mission;
clutch housing, the at least one toggle lever engaged with the an overrunning clutch assembly engaged to the
roll cage such that pivoting of the at least one toggle lever secondary drive shaft, the overrunning clutch
causes the roll cage to move with respect to the clutch assembly including: a differential housing;
housing; and wherein the second armature plate advances a pinion input shaft rotatably disposed within the
the roll cage by urging the at least one toggle lever to pivot. claim 18 wherein there are three toggle levers spaced
18. Abi-directional overrunning clutch according to substantially
claim 17 wherein the engagement between the at least one
toggle lever and the roll cage is provided by at least one pin
formed in the roll cage, the at least one toggle lever having
an end adapted to engage the pin in the roll cage.
19. Abi-directional overrunning clutch according to
 US RE38,012
60 differential
1
housing and engaged with the
1
secondary drive shaft;
a clutch housing disposed within the differential
hous- ing and rotatably connected to the pinion
input shaft, the clutch housing having an inner
surface;
65 at least one race disposed adjacent to the inner
surface of the clutch housing, the at least one
race being engaged with an output shaft;
 US RE38,012
1 1
a cage disposed between the at least one race and the 26. An overrunning clutch assembly comprising:
inner surface of the clutch housing, the cage having a differential housing;
a plurality of slots formed in and spaced circumfer-
entially about the cage, each slot having a movable a pinion input shaft having an end rotatably disposed
member located therein, the cage being adjustable 5 within the differential housing;
with respect to the clutch housing and the at least one a clutch housing disposed within the differential housing
race; and rotatably connected to the pinion input shaft, the
a first armature plate located adjacent to and adapted to clutch housing having an inner surface;
engage with the cage;
at least one race disposed adjacent to the inner surface of
a first coil mounted within the differential housing 10
adjacent to the first armature plate, the first coil the clutch housing, the at least one race being engaged
adapted to produce an electromagnetic field when with an output shaft;
energized which hinders the rotation of the first a cage disposed between the at least one race and the
armature plate causing the cage to move to a first inner surface of the clutch housing, the cage having a
position with respect to the clutch housing, the first 15 plu- rality of slots formed in and spaced
position of the cage locating the movable members circumferentially about the cage, each slot having a
so as to wedge between the inner surface and the at movable member located therein, the cage being
least one race when one of the primary wheels loses adjustable with respect to the clutch housing and the at
traction; least one race;
[a second armature plate located adjacent to the cage; 20 a first armature plate located adjacent to and adapted to
a second coil mounted within the di8erential housing engage with the cage; and
adjacent to the second armature plate, the second coil a first coil mounted within the differential housing adja-
adapted to produce an electromagnetic field when cent the first armature plate, the first coil adapted to
ener- produce an electromagnetic field when activated
gized which hinders the rotation of the second armature which hinders the rotation of the first armature plate
25
plate and causes the cage to move to a second position causing the cage to move to a first position with
with respect to the clutch housing, the second position
respect to the clutch housing, the first position of the
of the cage adapted to wedge the movable members
cage locating the movable members so as to be
between the inner surface and the at least one race;]
and an electronic control system connected to the first adapted /o wedge between the inner surface and the at
[and least one race[;
30
second coils] coil, the electronic control system a second armature plate located adjacent to the cage; and
providing signals for controlling energising of the a second coil mounted within the differential housing
first [and second coils] coil. adjacent to the second armature plate, the second coil
24. A vehicle according to claim 23 wherein the overrun- adapted to produce an electromagnetic field when acti-
ning clutch further includes a second armature plate located vated which hinders the rotation of the second
35
ad jacent to the cage; a second coil mounted within the armature plate and causes the cage to move to a
differential housing ad jacent to the second armature plate, second position with respect to the clutch housing, the
the second coil adapted to produce an electromagnetic second position of the cage adapted to wedge the
field when energized which hinders the rotation of the
movable members between the inner surface and the at
second armature plate and causes the cage to move to a
least one race] when the inner surface is rotating
second
position with respect to the clutch housing, the second
40 faster than the at least one race.
position of the cage adapted to wedge the movable 27. An overrunning clutch according claim 26 further
members between the inner surface and the at least one comprising a second armature plate located ad jacent to
race; and a third armature plate located adjacent to the the cage; a second coil mounted within the differential
cage; and a third housing
coil mounted within the differential housing adjacent to the
third armature plate, the third coil adapted to produce an 45 adjacent to the second armature plate, the second coil
electromagnetic field when energized which hinders the adapted to produce an electromagnetic field when
rotation of the third armature plate and causes the cage to activated which hinders the rotation of the second
move out of the second position and the movable members armature plate and causes the cage to move to a second
to disengage from between the inner surface and the at least position with respect to the clutch housing, the second
one race. position of the cage adapted
25. Avehicle according to claim 23 wherein the 50 to wedge the movable members between the inner surface
electronic control system includes a manually actuated and the at least one race.
button which when activated results in the energising of the
first coil.