USOO8516920B2

(12) United States Patent (10) Patent No.: US 8,516,920 B2

Liu (45) Date of Patent: Aug. 27, 2013
(54) ROBOT ARMASSEMBLY (56) References Cited
(75) Inventor: Zhen-Xing Liu, Shenzhen (CN) U.S. PATENT DOCUMENTS
4,637,773 A * 1/1987 Nakashima et al. .......... 414f732
4,732,526 A * 3/1988 Nakashima et al. .......... 414,730
(73) Assignees: Hong Fu Jin Precision Industry 4,750,858 A * 6/1988 Nakashima et al. .......... 414f732
(Shenzhen) Co., Ltd., Shenzhen (CN); 4,784,010 A * 1 1/1988 Wood et al. ................ 74/490.04
Hon Hai Precision Industry Co., Ltd., 4,806,066 A * 2/1989 Rhodes et al. ................ 414,729
New Taipei (TW) 4.903,536 A * 2/1990 Salisbury et al. ............ T4/89.22
5,046.375 A * 9/1991 Salisbury et al. ............ T4/89.22
5,207,114 A * 5/1993 Salisbury et al. .......... T4/479.01
(*) Notice: Subject to any disclaimer, the term of this 8,234,949 B2 * 8/2012 Pan et al. ........... ... 74f 490.04
patent is extended or adjusted under 35 2008/0229862 A1* 9, 2008 Nakamoto . ... 74f 490.04
2010/0162846 A1* 7, 2010 Lee et al. ... ... 74f 490.04
U.S.C. 154(b) by 236 days. 2010/017.0362 A1* 7, 2010 Bennett et al. ............. 74f 490.04
2011/O126651 A1* 6, 2011 Panet al. ....................... T4,892
(21) Appl. No.: 13/109,190 2011/0206481 A1* 8, 2011 Al-Mouhamed et al. ......... 414/5
* cited by examiner
(22) Filed: May 17, 2011 Primary Examiner — David M Fenstermacher
(74) Attorney, Agent, or Firm — Altis Law Group, Inc.
(65) Prior Publication Data
(57) ABSTRACT
US 2012/O103127 A1 May 3, 2012 A wrist housing, a wrist rotatably connected to the wrist
housing, a first driver, a first transmission mechanism, a
(30) Foreign Application Priority Data rotary member, a second driver, and a second transmission
mechanism makes a robot arm assembly. The wrist housing is
Oct. 27, 2010 (CN) .......................... 2010 1 0521 540 hollow. The first driver is assembled within the wrist housing
for driving the wrist to rotate relative to the wrist housing
along a first rotary axis. The first transmission mechanism is
(51) Int. Cl. also assembled within the wrist housing and is positioned
B25, 17/00 (2006.01) between the wrist and the first driver. The rotary member is
(52) U.S. Cl. rotatably assembled to a distal end of the wrist along a second
USPC .......... 74/490.06: 74/490.05;901/28:901/29 rotary axis. The second driver is assembled within the wrist
(58) Field of Classification Search housing for driving the rotary member to rotate. The second
transmission mechanism is assembled within the wrist hous
USPC ............... 74/490.01, 490.02,490.03, 490.04,
74/490.05, 490.06; 41.4/732, 736: 901/21, ing, and is positioned between the second driver and the
901/23, 27, 28, 29 rotary member.
See application file for complete search history. 19 Claims, 4 Drawing Sheets

141
U.S. Patent US 8,516,920 B2

FIG 1.
U.S. Patent Aug. 27, 2013 Sheet 2 of 4 US 8,516,920 B2

1411 1413
141

FIG 2
U.S. Patent Aug. 27, 2013 Sheet 3 of 4 US 8,516,920 B2

2411

115 2412 242 241 13

FIG 3
U.S. Patent Aug. 27, 2013 Sheet 4 of 4 US 8,516,920 B2

2422 242
243 1213 24
24.21

2.

H2S,
A% 27.
Prs-A
LSSAA
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FIG, 4.
 US 8,516,920 B2
1. 2
ROBOT ARMASSEMBLY assembled within the wrist housing 11 for driving the rotary
member 22 to rotate along the rotary axis c. The second
BACKGROUND transmission mechanism 24 is assembled within the wrist
housing 11, and is positioned between the second driver 23
1. Technical Field and the rotary member 22 for transferring a rotation move
This disclosure relates to robotics, and particularly, to a ment of the second driver 23 to the rotary member 22.
robot arm assembly. In one embodiment, the robot arm assembly 100 is applied
2. Description of Related Art to a six-axis robot (not shown), the wrist housing 11, the wrist
Industrial robots are widely used in many fields such as 12 and the rotary member 22 can be respectively driven to
industrial manufacturing, repair, and testing. A commonly 10
rotate along rotary axes a, b, and c. The rotary member 22 is
used robot includes a plurality of individual robot arms, with configured for assembling an actuator Such as a cutter, or a
every two robot arms connected by a joint structure. Each fixture. The rotary axis a and the rotary axis care both per
robot arm is driven by a driving assembly to rotate along a pendicular to the rotary axis b. The rotary axes a, b and c can
corresponding rotating axis. The existing conventional driv intersect with each other to a point.
ing assembly is generally assembled within the robot arm, 15
The wrist housing 11 includes a main bracket 112, two
and includes a driving motor and a motor reducer. The con support arms 113, 115, and two covers 117, 119. The two
ventional driving assembly occupies a large amount of space
within the robot arm and is relatively heavy. Most of the support arms 113, 115 are opposite to each other, and paral
weight is positioned or exerted on an output shaft of the motor lelly extend out from one end of the main bracket 112 along a
reducer such that the integral strength of the robot arm is direction parallel to two sides of the main bracket 112. A
reduced over time. In addition, the existing robot arm assem receiving hole 1123 is defined through the two sides of the
bly occupies also a relatively large amount of space and is also main bracket 112 along a direction perpendicular to the two
heavy. support arms 113, 115, namely, a direction perpendicular to
Therefore, there is room for improvement in the art. the rotary axis a, of the main bracket 112, and is positioned
25 adjacent to the other end of the main bracket 112 opposite to
BRIEF DESCRIPTION OF THE DRAWINGS the two support arms 113, 115. A receiving space 1124 is
formed between the two support arms 113, 115 for assem
Many aspects of the embodiments can be better understood bling the wrist 12. The two covers 117, 119 are mounted on
with reference to the following drawings. The components in two opposite sides of the wrist housing 11 for covering the
the drawings are not necessarily drawn to Scale, the emphasis 30 receiving hole 1123 and the two support arms 113, 115.
instead being placed upon clearly illustrating the principles of The first driver 13 and the Second driver 23 are both
the robot arm assembly. Moreover, in the drawings like ref assembled within the receiving hole 1123 of the wrist housing
erence numerals designate corresponding parts throughout 11. Such that, a barycenter of the whole robot arm assembly
the several views. Wherever possible, the same reference 100 is located adjacent to the main bracket 112 of the wrist
numerals are used throughout the drawings to refer to the 35 housing 11, and the weight of the rotary member 22 is
same or like elements of an embodiment. decreased, and thus, facilitating precise control to the rotary
FIG. 1 is an assembled perspective view of an embodiment member 22. In addition, as the second driver 23 is assembled
of a robot arm assembly. within the receiving hole 1123 of the wrist housing 11, a
FIG. 2 is a partial assembled perspective view of the robot plurality of connecting cables (not shown) which are con
arm assembly of FIG. 1, wherein, a side cover is detached 40 nected to the second driver 23 are not needed to pass through
from the robot arm assembly. the wrist 12, such that, the connecting cables thereby avoid
FIG. 3 is another partial assembled perspective view of the being damaged during usage. In one embodiment, the first
robot arm assembly of FIG. 1 shown from another aspect, driver 13 and the second driver 23 are both servo motors, and
wherein, another side cover is detached from the robot arm are both assembled adjacent to and parallel to each other
assembly. 45 within the wrist housing 11.
FIG. 4 is a cross-section of the robot arm assembly of FIG. The wrist 12 is substantially hollow T-shaped, and is rotat
1, taken along line IV-IV. ably assembled to one end of the wrist housing 11, along the
rotary axis b perpendicular to the axis a of the main bracket
DETAILED DESCRIPTION 112. The wrist 12 includes a first sleeve body 121 and a
50 second sleeve body 122 substantially perpendicularly inter
Referring to FIGS. 1 through 4, an embodiment of a robot secting with the first sleeve body 121. The first sleeve body
arm assembly 100 is shown. The robot arm assembly 100 121 is received within the receiving space 1124 formed by the
includes a wrist housing 11, a wrist 12 rotatably connected to two support arms 113, 115. Two ends of the first sleeve body
the wrist housing 11, a first driver 13, a first transmission 121 are rotatably assembled to the two supportarms 113, 115,
mechanism 14, a rotary member 22, a second driver 23, and a 55 respectively. A distal end of the second sleeve body 122 is
second transmission mechanism 24. The wrist housing 11 is exposed to the outer side of the receiving space 1124 away
hollow shaped, and the wrist housing 11 can be driven to from the main bracket 112. The rotary member 22 is rotatably
rotate along a rotary axis a. The wrist 12 is rotatably assembled to the distal end of the second sleeve body 122
assembled to one end of the wrist housing 11. The first driver along the rotary axis c perpendicular to the rotary axis b, for
13 is assembled within the wrist housing 11 for driving the 60 connecting with other tools such as cutting tool, or fixture.
wrist 12 to rotate relative to the wrist housing 11 along a In one embodiment, two ends of the first sleeve body 121
rotary axis b. The first transmission mechanism 14 is also define a first shaft hole 1212 and a second shaft hole 1213
assembled within the wrist housing 11, and is positioned along the rotary axis b direction, respectively. The second
between the wrist 12 and the first driver 13 for transferring a sleeve body 122 defines a third shaft hole 1214 along the
rotation movement of the first driver 13 to the wrist 12. The 65 rotary axis c direction. The third shaft hole 1214 is perpen
rotary member 22 is rotatably assembled to a distal end of the dicular to and communicates with the first and second shaft
wrist 12 along a rotary axis c. The second driver 23 is holes 1212, 1213.
 US 8,516,920 B2
3 4
The first transmission mechanism 14 is assembled within together with the second rotary shaft 242. The rotary member
the wrist housing 11, and is positioned between the wrist 12 22 is mounted to the other end of the third rotary shaft 244
and the first driver 13 for transferring a rotation movement of opposite to the main bracket 112. The second harmonic
the first driver 13 to the wrist 12. The first transmission reducer 246 is coupled to the third rotary shaft 244 for reduc
mechanism 14 includes a first belt transmission assembly ing a rotating speed of the third rotary shaft 244 transmitted
141, a first rotary shaft 142, and a first harmonic reducer 143. by the second belt transmission assembly 241 from the sec
The first belt transmission assembly 141 is assembled within ond driver 23.
the wrist housing 11, and positioned at a same side as the The second belt transmission assembly 241 includes an
support arm 113 for coupling the first driver 13 and the wrist input belt wheel 2411, an output belt wheel 2412, and a
12 together. The first rotary shaft 142 is assembled into the 10 transmission belt 2413. The input belt wheel 2411 is coupled
first shaft hole 1212 of the wrist 12 and the supportarm113 of to an output end of the second driver 23 and is driven by the
the wrist housing 11 by a pair of deep groove ball bearings second driver 23 to rotate. The output belt wheel 2412 is
1421. The first harmonic reducer 143 is coupled to the first secured to a distal end of the second rotary shaft 242. The
rotary shaft 142 for reducing a rotating speed of the wrist 12 transmission belt 2413 is mounted to the input belt wheel
transmitted by the first belt transmission assembly 141 from 15 2411 and the output belt wheel 2412 for connecting the input
the first driver 13. A cross roller bearing 145 is positioned belt wheel2411 and the output belt wheel2412 together. Such
between the first harmonic reducer 143 and the wrist 12 for that, the input belt wheel 2411 is driven to rotate with the
Supporting the wrist 12 and ensuring a stable movement to the second driver 23, and the output belt wheel 2412 is then
wrist 12. driven to rotate together with the input belt wheel 2411 by the
In one embodiment, the first belt transmission assembly transmission belt 2413. By means of the second belt trans
141 includes an input belt wheel 1411, an output belt wheel mission assembly 241 and the second harmonic reducer 246.
1412, and a transmission belt 1413. The input belt wheel 1411 a rotating speed of the second driver 23 can be efficiently
is coupled to an output end of the first driver 13 and is driven reduced to a desired rotating speed and finally be transmitted
by the first driver 13 to rotate. The output belt wheel 1412 is to the second and third rotary shafts 242, 244.
secured to a distal end of the first rotary shaft 142. The 25 It is understood that the two covers 117, 119 of the wrist
transmission belt 1413 is mounted to the input belt wheel housing 11 can also be omitted.
1411 and the output belt wheel 1412 for connecting the input It is to be understood, however, that even through numer
belt wheel 1411 and the output belt wheel 1412 together. ous characteristics and advantages of the disclosure have
Thus, as in use, the input belt wheel 1411 is driven to rotate by been set forth in the foregoing description, together with
the first driver 13, and the output belt wheel 1412 is then 30 details of the structure and function of the invention, the
driven to rotate together with the input belt wheel 1411 by the disclosure is illustrative only, and changes may be made in
transmission belt 1413. By means of the first belt transmis detail, especially in matters of shape, size, and arrangement of
sion assembly 141 and the first harmonic reducer 143, a parts within the principles of the invention to the full extent
rotating speed of the first driver 13 can be efficiently reduced indicated by the broad general meaning of the terms in which
to a desired rotating speed and finally be transmitted to the 35 the appended claims are expressed.
first rotary shaft 142. What is claimed is:
The second transmission mechanism 24 is assembled 1. A robot arm assembly, comprising:
within the wrist housing 11, and is positioned between the a wrist housing, the wrist housing being hollow and com
wrist 12 and the second driver 23 for transferring the rotation prising a main bracket, and two Support arms parallelly
movement of the second driver 23 to the wrist 12. In one 40 extending out from an end of the main bracket along a
embodiment, the second transmission mechanism 24 direction parallel to two sides of the main bracket;
includes a second belt transmission assembly 241, a second a wrist rotatably connected to the wrist housing along a first
rotary shaft 242, a drive bevel gear 243, a third rotary shaft axis and assembled between the two support arms of the
244, a driven bevel gear 245 and a second harmonic reducer wrist housing, the wrist comprising a first sleeve body
246. 45 and a second sleeve body Substantially perpendicularly
The second belt transmission assembly 241 has a same intersecting with the first sleeve body, two ends of the
structure as the first belt transmission assembly 141. The first sleeve body being rotatably assembled to the two
second belt transmission assembly 241 is also assembled Support arms, respectively, the two ends of the first
within the wrist housing 11 and is positioned at a same side as sleeve body respectively defining a first shaft hole and a
the support arm 115 opposite to the first belt transmission 50 second shaft hole along the first axis;
assembly 141, for coupling the second driver 23 and the wrist a first driver assembled within the wrist housing for driving
12 together. One end of the second rotary shaft 242 is the wrist to rotate relative to the wrist housing:
assembled into the second shaft hole 1213 of the wrist 12 by a first transmission mechanism assembled within the wrist
a pair of angular contact bearings 2421, and the other end of housing for transferring a rotation movement of the first
the second rotary shaft 242 is assembled into the first shaft 55 driver to the wrist;
hole 1212 of the wrist 12 by a pair of deep groove ball a rotary member rotatably assembled to a distal end of the
bearings 2422. second sleeve body of the wrist;
The drive bevel gear 243 is mounted to a substantially a second driver assembled within the wrist housing for
middle portion of the second rotary shaft 242 and received driving the rotary member to rotate alonga second rotary
within the first sleeve body 121. The third rotary shaft 244 is 60 axis; and
assembled within the third shaft hole 1214 of the second a second transmission mechanism assembled within the
sleeve body 122 of the wrist 12 with a pair of angular contact wrist housing, for transferring a rotation movement of
bearings 2441. The driven bevel gear 245 is mounted to one the second driver to the rotary member, wherein the
end of the third rotary shaft 244 and engages with the drive second transmission mechanism comprises a second
bevel gear 243 mounted to the second rotary shaft 242. Thus, 65 rotary shaft rotatably assembled into the first shaft hole
as the second rotary shaft 242 is driven to rotate with the and the second shaft hole of the first sleeve body by
second driver 23, the third rotary shaft 244 is driven to rotate opposite ends, the rotary member is connected to the
 US 8,516,920 B2
5 6
second rotary shaft, the second driver is mounted upon 11. A robot arm assembly, comprising:
the first driver, and output ends of the first driver and the a wrist housing comprising a main bracket, and two Sup
second driver extend away from each other. port arms parallelly extending out from an end of the
2. The robot arm assembly as claimed in claim 1, wherein main bracket along a direction parallel to two sides of the
main bracket;
the second rotary axis is perpendicular to the first rotary axis, a wrist rotatably connected to the wrist housing and
the first transmission mechanism is positioned between the assembled between the two support arms of the wrist
wrist and the first driver; the second transmission mechanism housing, and assembled between the two Support arms
is positioned between the second driver and the rotary mem of the wrist housing, the wrist comprising a first sleeve
ber. 10
body and a second sleeve body Substantially perpen
3. The robot arm assembly as claimed in claim 1, wherein dicularly intersecting with the first sleeve body, two ends
of the first sleeve body being rotatably assembled to the
a receiving space is defined between the two Supportarms; the two support arms, respectively, the two ends of the first
wrist is rotatably assembled to the wrist housing and received sleeve body respectively defining a first shaft hole and a
in the receiving space. second shaft hole along a rotary axis of the wrist;
15
4. The robot arm assembly as claimed in claim 3, wherein a first driver assembled within the wrist housing for
the main bracket defines a receiving hole, the first driver and driving the wrist to rotate;
a first transmission mechanism assembled within the
the second driver are both assembled within the receiving wrist housing and positioned between the wrist and
hole of the wrist housing and positioned adjacent to and the first driver for transferring a rotation movement of
parallel to each other. the first driver to the wrist;
5. The robot arm assembly as claimed in claim 4, wherein a rotary member rotatably assembled to the wrist; and
the wrist is substantially hollow T-shaped, the distal end of the a second driver assembled within the wrist housing for
second sleeve body is exposed to the outer side of the receiv driving the rotary member to rotate along a direction
ing space away from the main bracket. perpendicular to the first driver, wherein the second
25 transmission mechanism comprises a second rotary
6. The robot arm assembly as claimed in claim 5, wherein shaft rotatably assembled into the first shaft hole and
the first transmission mechanism comprises a first belt trans the second shaft hole of the first sleeve body by oppo
mission assembly, and a first rotary shaft, the first belt trans site ends, the rotary member is connected to the sec
mission assembly is assembled within the wrist housing and ond rotary shaft, the second driver is mounted upon
positioned at a same side as one Support arm for coupling the 30 the first driver, and output ends of the first driver and
first driver and the wrist together; the first rotary shaft is the second driver extend away from each other.
assembled into the first shaft hole of the wrist and the support 12. The robot arm assembly as claimed in claim 11,
arm of the wrist housing. wherein a receiving space is defined between the two Support
7. The robot arm assembly as claimed in claim 6, wherein arms; the wristis rotatably assembled to the wrist housing and
the first transmission mechanism further comprises a first 35 received within the receiving space.
harmonic reducer coupled to the first rotary shaft for reducing 13. The robot arm assembly as claimed in claim 12,
a rotating speed of the wrist transmitted by the first belt wherein the main bracket defines a receiving hole, the first
transmission from the first driver. driver and the second driver are both assembled within the
8. The robot arm assembly as claimed in claim 7, wherein receiving hole of the wrist housing and positioned adjacent to
the first transmission mechanism further comprises a cross 40 and parallel to each other.
roller bearing positioned between the first harmonic reducer 14. The robot arm assembly as claimed in claim 13,
and the wrist for Supporting the wrist. wherein the first transmission mechanism comprises a first
belt transmission assembly, and a first rotary shaft, the first
9. The robot arm assembly as claimed in claim 6, wherein belt transmission assembly is assembled within the wrist
the first belt transmission assembly comprises an input belt 45 housing and positioned at a same side as one Support arm for
wheel, an output belt wheel, and a transmission belt; the input coupling the first driver and the wrist together; the first rotary
belt wheel is coupled to the output end of the first driver and shaft is assembled into the first shaft hole of the wrist and the
is driven by the first driver to rotate; the output belt wheel is Support arm of the wrist housing by a pair of deep groove ball
secured to a distal end of the first rotary shaft; the transmis bearings.
sion belt is mounted to the input belt wheel and the output belt 50 15. The robot arm assembly as claimed in claim 14,
wheel for connecting the input belt wheel and the output belt wherein the first transmission mechanism further comprises a
wheel together. first harmonic reducer coupled to the first rotary shaft for
10. The robot arm assembly as claimed in claim 6, wherein reducing a rotating speed of the wrist transmitted by the first
the second transmission mechanism further comprises a sec belt transmission from the first driver.
ondbelt transmission assembly, a drive bevel gear mounted to 55 16. The robot arm assembly as claimed in claim 15,
the second rotary shaft, a third rotary shaft, and a driven bevel wherein the first transmission mechanism further comprises a
gear mounted to the third rotary shaft; the second belt trans cross roller bearing positioned between the first harmonic
mission assembly is positioned at a same side as the other reducer and the wrist for Supporting the wrist.
Support arm opposite to the first belt transmission assembly, 17. The robot arm assembly as claimed in claim 14,
for coupling the second driver and the wrist together; the 60 wherein the first belt transmission assembly comprises an
second rotary shaft is assembled within the first sleeve body; input belt wheel, an output belt wheel, and a transmission
the second sleeve body defines a third shaft hole perpendicu belt; the input belt wheel is coupled to the output end of the
lar to and communicates with the first and second shaft holes; first driver and is driven by the first driver to rotate; the output
the third rotary shaft is assembled within the third shaft hole belt wheel is secured to a distal end of the first rotary shaft; the
with the driven bevel gear engaging with the drive bevel gear; 65 transmission belt is mounted to the input belt wheel and the
the rotary member is mounted to a distal end of the third output belt wheel for connecting the input belt wheel and the
rotary shaft. output belt wheel together.
 US 8,516,920 B2
7
18. The robot arm assembly as claimed in claim 11,
wherein the robot arm assembly further comprises a second
transmission mechanism assembled within the wrist housing,
for transferring a rotation movement of the second driver to
the rotary member; the second transmission mechanism fur
ther comprises a second belt transmission assembly, and a
third rotary shaft; the second belt transmission assembly is
positioned at a same side as the other Support arm opposite to
the first belt transmission assembly, for coupling the second
driver and the wrist together; the second rotary shaft is 10
assembled within the first sleeve body; the second sleeve
body defines a third shaft hole perpendicular to and commu
nicates with the first and second shaft holes; the third rotary
shaft is assembled within the third shaft hole and engages
with the second rotary shaft; the rotary member is mounted to 15
a distal end of the third rotary shaft.
19. The robot arm assembly as claimed in claim 18,
wherein the second transmission mechanism further com
prises a drive bevel gear mounted to the second rotary shaft,
and a driven bevel gear mounted to the third rotary shaft; the 20
driven bevel gear engages with the drive bevel gear.
k k k k k