Parallel gripper with roller supported gripper arms

A gripping apparatus which includes a housing in which is slidably mounted a longitudinally movable gripper operator. A pair of gripper arms are rollably mounted on the gripper operator. Each gripper arm carries a gripper jaw engageable with a workpiece. The gripper jaws are moved along straight line travel paths into gripping engagement with a workpiece when the gripper operator is moved in one longitudinal direction, and they are disengaged correspondingly from the workpiece when the gripper operator is moved in the other longitudinal direction.

BACKGROUND OF THE INVENTION 
1. Technical Field 
The field of art to which this invention pertains may be generally located 
in the class of devices relating to grippers or gripping devices. 
2. Background Information 
It is known in the robot gripper art to provide parallel motion gripping 
devices or grippers for gripping workpieces to move the workpiece between 
selected positions. A disadvantage of some of the prior art grippers is 
that, although it is advertised that they provide a parallel motion, the 
gripper arms for such grippers move in an arc. Accordingly, if the gripper 
arms on such grippers have a V-shaped gripping jaw or finger, then it is 
necessary to reprogram the controls for the gripping apparatus for each 
size workpiece, since with different diameters, the V-shaped jaws will be 
at different positions along the arcuate path through which the gripper 
jaws are moved. There are some true parallel motion grippers on the 
market, but a disadvantage of the last mentioned grippers is that they 
basically work off a wedge means, which provides only a very short stroke 
or movement for the gripping jaws. A disadvantage of the last mentioned 
prior art true parallel grippers is that they cannot be used for a wide 
range of different diameter workpieces, and accordingly, they lack 
versatility. It is also known in the prior art to provide a true centering 
steady rest, having a center wear pad and two side wear pads for movement 
into supporting engagement with a workpiece, as shown in U.S. Pat. No. 
4,399,639. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, a true parallel gripping 
apparatus or gripper is provided which includes two gripper arms, which 
may be provided with either inner or outer diameter gripping jaws or 
fingers for gripping a workpiece, and moving it between selected locations 
or work positions. The gripper of the present invention is adapted to hold 
various size diameter workpieces, without the need for readjusting or 
reprogramming the controls for the gripping apparatus, and without having 
to repeatedly find the longitudinal center of a workpiece. The gripping 
apparatus of the present invention provides true parallel movement of the 
gripping jaws for engaging a workpiece, and it also provides high gripping 
forces for holding a workpiece while it is moved between work positions. 
The gripping apparatus of the present invention is also constructed and 
arranged so that a plurality of the same can be used in a stacked 
arrangement, so that the number of movements of a robot necessary to load 
and unload a workpiece can be reduced. The gripping apparatus of the 
present invention is compact in structure. It can be rotated about its 
longitudinal axis in a minimum of space, and it also has a flat 
configuration so that it can be moved down onto a workpiece carrying 
device, such as a pallet, and pick up a workpiece laying on a pallet, in 
an efficient manner. The present invention is adaptable to many uses and 
applications involving the handling, holding or manipulating of 
workpieces. Particular examples are robot arm grippers, pick and place 
units, work holding fixtures or steady rests and gauging heads. 
The gripping apparatus of the present invention comprises a housing which 
includes a front cover plate, and a rear cover plate, and said cover 
plates include integral side, bottom and top plates. A gripper operator is 
rollably mounted inside of the housing, and it is operatively attached at 
its bottom end to a power means for moving the gripper operator 
longitudinally in the housing. A pair of gripper arms are rollably mounted 
on the gripper operator, and they are operatively connected to a cam 
means, whereby when the gripper operator is moved longitudinally in one 
direction in the housing, toward a workpiece, the gripper arms are moved 
toward each other in a linear or parallel path into gripping engagement 
with the outer diameter or surface of a workpiece, and when the gripper 
operator is moved longitudinally in the other direction in the housing, or 
away from the workpiece, the gripper arms are retracted along their 
respective linear or parallel travel paths from the workpiece to release 
the same. The movements of the gripper operator and the gripper arms are 
reversible to provide selective inner diameter or outer surface gripping 
actions on a workpiece.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, and in particular to FIG. 1, the numeral 10 
generally designates an outer diameter, parallel gripper or gripping 
apparatus made in accordance with the principles of the present invention. 
The numeral 11 designates an elongated cylindrical workpiece, as for 
example, an elongated shaft which is to be gripped on the outer diameter 
thereof and moved between selective work positions or locations. The 
gripper apparatus 10 may be used for moving the workpiece 11 between 
machining operation locations, assembly operation locations, or other 
manufacturing operation locations. It will be understood that the gripper 
apparatus 10 would be carried on a conventional robot arm, which in turn 
would be moved by a conventional robotic power means. 
As shown in FIGS. 1 through 3, the gripper apparatus of the present 
invention includes a housing comprising a front cover plate, generally 
indicated by the numeral 12, and a rear cover plate, generally indicated 
by the numeral 13 (FIG. 3). The pair of front and rear cover plates 12 and 
13 are identically formed, and they are interchangeable. The cover plates 
12 and 13 are made from any suitable material as, for example, aluminum. 
As shown in FIGS. 1-3 and 10, the gripper apparatus 10 includes a gripper 
operator 14, which is rollably mounted within the aforedescribed housing, 
and which is made from any suitable material as, for example, aluminum. As 
shown in FIGS. 1 and 2, the gripper apparatus 10 includes a pair of 
gripper arms or members 15 and 16 which are identical in structure, and 
which are made from any suitable material as, for example, aluminum. As 
shown in FIGS. 1 and 2, the cover plates 12 and 13 are designated as the 
front and rear cover plates, respectfully, for purposes of describing the 
structure of the gripper apparatus 10 as it is positioned in the various 
figures in the drawings of this application. A power cylinder, generally 
indicated by the numeral 18, is operatively mounted on the lower end of 
the apparatus housing and it is operatively connected to the lower end of 
the gripper operator body 14 by a cylinder guide adaptor 17, as described 
in detail hereinafter. The power cylinder 18 may be of any suitable type 
as, for example, it may be a pneumatic or hydraulic cylinder. 
As shown in FIG. 4, the rear cover plate 13 includes a rear wall plate 21. 
The rear cover plate 13 further includes an integral top end plate 23, a 
pair of integral upper side plates 26 and 27, a pair of lower side plates 
29 and 30 which slope downwardly and converge toward each other and have 
their lower ends integral with a bottom integral plate 31. The top and 
bottom end plates 23 and 31, and the integral side plates 26, 27, 29, and 
30 extend inwardly from the rear wall plate 21, toward the front cover 
plate 12, and they form an inner recess or chamber 22. As shown in FIG. 4, 
a slot or opening is formed through the right side of the integral top end 
plate 23, and the ends of said slot are indicated by the numerals 24 and 
25. As shown in FIGS. 4 through 7, the outer surface of the top and bottom 
end plates 23 and 31, respectively, and the side plates 26, 27, 29 and 30 
have a common inner surface or face 32 for joining with a similar inner 
face 52 (FIG. 3) on the front cover plate 12. 
As shown in FIGS. 4 through 7, the rear cover plate 13 is provided with a 
centrally disposed, longitudinally extended cam slot 35, which is 
rectangular in cross section, and which extends from the top end plate 23 
downwardly to communicate with a similar size, aligned slot 36 which is 
formed through the bottom end plate 31. A transverse cam slot 37 is also 
formed in the inner surface of the rear wall plate 21, and its inner end 
communicates with the longitudinal cam slot 35, and the outer end thereof 
extends toward the side plates 26 and 29. The cross sectional shape of the 
cam slot 37 is also rectangular and made to the same size as the 
longitudinal cam slot 35 
As shown in FIGS. 1 and 3, the front cover plate 12 includes a front wall 
plate 42. The front cover plate 12 further includes an integral top end 
plate 44, a pair of integral upper side plates 47 and 48, and a pair of 
lower side plates 49 and 50, which slope downwardly and converge toward 
each other and have their lower ends integral with a bottom integral plate 
51. The top and bottom end plates 44 and 51, and the integral side plates 
47, 48, 49 and 50 extend inwardly from the front wall plate 42 and they 
form an inner recess or chamber 43. As shown in FIG. 1, a slot or opening 
is formed through the left side of the integral top end wall 44, and the 
ends of said slot are indicated by the numerals 45 and 46. It will be 
understood from FIG. 3, that the top and bottom end plates 44 and 51, 
respectively, and the side plates 47 through 50 have a common inner 
surface or face 52, for joining with the common inner face 32 on the rear 
cover plate 13. 
As shown in FIGS. 1 and 3, the front cover plate 12 is provided with a 
centrally disposed, longitudinally extended cam slot 40, which is 
rectangular in cross section, and which extends from the top end plate 44 
downwardly to communicate with a similar size, aligned slot 53 formed 
through the bottom end plate 51. A transverse cam slot 41 is also formed 
in the inner surface of the front cover wall plate 42, and its inner end 
communicates with the longitudinal cam slot 40, and the outer end thereof 
extends towards the side plates 48 and 50. The cross section shape of the 
transverse cam slot 41 is also rectangular, and it is made to the same 
cross section size as the longitudinal cam slot 40. 
As shown in FIGS. 1 and 2, the front cover plate 12 is secured to the rear 
cover plate 13 at the top end thereof, by a pair of suitable machine 
screws 55, which are operatively mounted in the holes 56 that extend 
through both of the cover plates 12 and 13. For example, the left machine 
screw 55, as shown in FIGS. 1 and 2, would slidably pass through the end 
of the hole 56 in the front cover plate 12 and be threadably engaged into 
the threaded other end of the hole 56 in the rear cover plate 13. It is 
also shown in FIGS. 1 and 2 that the right machine screw 55 extends 
through the rear cover plate 13 and into the threaded portion of the hole 
56 in the front cover plate 12. The front cover plate 12 is further 
secured to the rear cover plate 13 at the bottom ends thereof, by a pair 
of similar machine screws 57 which pass through suitable holes 58 in the 
bottom end walls 51 and 31, and into the opposite ends of the holes 58, 
which are threaded for threaded engagement by the threaded parts of the 
screws 57. As shown in FIGS. 1 and 2, the front cover plate 12 and the 
rear cover plate 13 are further secured together, on the sides thereof, by 
a plurality of suitable machine screws 59 which each pass through one end 
of a hole 60 in the front cover plate side walls 47 and 48 and into 
threaded engagement with the threaded ends of the holes 60 in the side 
walls 26 and 27, respectively, in the rear cover plate 13 (FIG. 4). As 
shown in FIGS. 1, 2 and 4, the gripper apparatus 10 is provided with a 
plurality of mounting holes 63 which are formed through the front cover 
side plates 47 and 48, and which are aligned with threaded mating mounting 
holes 64 that are formed through the side plates 26 and 27 in the rear 
cover plate 13 (FIG. 4). 
As shown in FIG. 10, the gripper operator 14 includes a triangular body or 
plate 65 which is adapted to be centrally mounted in the space between the 
front cover plate 12 and the rear cover plate 13. The space between said 
cover plates is formed by the chambers 43 and 22, which have been 
previously described as being formed in the front and rear cover plates 12 
and 13, respectively. The converging sides of the gripper operator body 65 
are designated by the numerals 66 and 67, and the top end is indicated by 
the numeral 68. A pair of equally spaced apart U-shaped recesses 69 and 70 
are formed in the top end 68 of the gripper operator body 65. A hole 71 is 
formed through the lower end of the gripper operator body 65, at the 
junction point of the converging sides 66 and 67. 
The cylinder guide adaptor 17 for moving the gripper operator 14 
longitudinally in the gripper apparatus housing is shown in detail in FIG. 
11. The cylinder guide adaptor 17 includes a transverse base plate 78 and 
a pair of integral, spaced apart longitudinal arms 77, which are disposed 
parallel to each other, and disposed longitudinally in the gripper 
apparatus housing (FIG. 3). A transverse hole 76 is formed through the 
free end of each of the adaptor arms 77. A transverse shaft 74 is 
operatively mounted through the adaptor leg holes 76 and retained in place 
by any suitable means, as by a press fit. A pair of rollers 75 are 
rotatably mounted on the shaft 74, in spaced apart positions, with their 
outer sides in abutment with the inner faces of the adaptor arms 77. 
As shown in FIG. 3, the cylinder guide adaptor 17 is operatively attached 
to the lower end of the gripper operator body 65 by having the shaft 74 
extended through the hole 71 in the lower end of the gripper operator body 
65. The rollers 75 are thus positioned on opposite sides of the lower end 
of the gripper operator body 65. The cylinder guide adaptor 17 is 
positioned to be moved longitudinally in the gripper apparatus housing in 
the longitudinal cover plate slots 40 and 35, and the communicating lower 
end slots 53 and 36. As shown in FIGS. 1 through 3 and 11, the transverse 
base plate 78 of the cylinder guide adaptor 17 has a hole 81 formed 
therethrough, through which is mounted the upper end of a reduced diameter 
end 82 of the usual cylinder rod 83 of the power cylinder 18. The cylinder 
rod reduced diameter end 82 has formed thereon, an integral, enlarged head 
84 which seats on the upper side of the adaptor transverse plate 78, and 
with the upper end of the cylinder rod 83 in abutment against the lower 
side of the adaptor transverse plate 78. 
The power cylinder 18 is fixedly secured in place on the lower end of the 
gripper apparatus housing by a plurality of suitable cap screws 87. The 
cap screws 87 are mounted through bores 88 formed through the body of the 
housing of the power cylinder 18, and with their threaded ends mounted in 
threaded holes 89 formed in the lower end walls 51 and 31 of the front and 
rear cover plates 12 and 13, respectively. As shown in FIGS. 1 and 2, the 
power cylinder 18 is provided with the usual ports 92 and 93 for 
attachment to suitable conduits for conveying pressurized fluid, such as 
air or hydraulic oil, into the cylinder 18, for operating the cylinder rod 
83 between the positions shown in FIGS. 1 and 2. The pressurized fluid 
admitted into the upper port 92 moves the gripper operator 14 downwardly 
into the position shown in FIG. 1 to open the gripper arms 15 and 16. The 
pressurized fluid that is admitted into the lower port 93 operates the 
cylinder 18 to move the cylinder rod 83 upwardly, so as to move the 
gripper arms 15 and 16 sidewardly inward, in a linear or parallel path, to 
grip the outer diameter of the workpiece 11. 
As best seen in FIG. 10, the gripper operator body 65 has a roller 96 
operatively mounted on one side thereof, and a roller 97 operatively 
mounted on the other side thereof at the upper corner or junction between 
the side 66 and the top end 68. As illustrated in FIG. 1, the gripper body 
plate 65 has a transverse hole 95 formed therethrough at the upper left 
hand corner through which is operatively mounted a roller shaft 98, and on 
the opposite ends thereof of which are rotatably mounted the rollers 97 
and 98. As shown in FIG. 1, the upper right hand corner or termination 
point between the gripper body plate side 67 and the top end 68, is 
provided with a transverse hole 94 through which is operatively mounted a 
roller shaft 101. As shown in FIG. 10, the roller shaft 101 carries the 
rollers 99 and 100, on the opposite ends thereof, on the opposite sides of 
the gripper body plate 65. As illustrated in FIG. 1, a transverse hole 102 
is formed through the upper end of the gripper body plate 65, in a 
position parallel to the holes 94 and 95 and equally spaced therefrom, and 
on the same axial plane. As shown in FIG. 1, a roller shaft 106 is 
operatively mounted through the hole 102. As shown in FIG. 10, a pair of 
rollers 104 are rotatably mounted on one end of the shaft 106, on one side 
of the body plate 65, and a pair of rollers 105 are mounted on the other 
end of the shaft 106, on the other side of the body plate 65. As shown in 
FIG. 3, the gripper operator 14 is slidably mounted in the cover part 
recesses 43 and 22, and in sliding engagement with the inner surfaces of 
the front and rear cover wall plates 42 and 21, respectively. 
As shown in FIG. 1, the gripper arm 15 includes an angular portion 109 and 
an integral longitudinal portion 111. The angular portion 109 is disposed 
at an angle of 45 degrees from the longitudinal axis of the gripper 
operator 14, and it is rollably mounted on the front side of the gripper 
operator body 65, as viewed in FIG. 1. The gripper arm angular portion 109 
is rollably mounted between the rollers 96, 104 and 75. As shown in FIGS. 
1 and 8, the gripper arm 15 is provided with a hole 110 at the inner end 
thereof. The longitudinal portion 111 of the gripper arm 15 is provided 
with a pair of transverse threaded holes 112. As shown in FIG. 1, a shaft 
116 has one end fixed in the hole 110 and it is secured in place by any 
suitable means, as by a press fit. A suitable roller 115 is rotatably 
mounted on the portion of the shaft 116 that extends outwardly from the 
gripper arm portion 109 and toward the front cover wall plate 42. The 
roller 115 comprises a cam roller and it is rollably mounted in the 
transverse cam slot 41 formed in the inner surface of the front cover wall 
plate 42. 
As is shown in FIG. 1, the gripper arm 16 includes an angular portion 119 
which is provided at its lower inner end with a transverse hole 120. A 
shaft 122 is fixedly mounted in the hole 120 by any suitable means, as by 
a press fit, and a cam roller 121 is rotatably mounted on the shaft 122 
which extends rearwardly, as shown in FIG. 1 and toward the rear cover 
wall plate 21. The can roller 121 is rollably mounted in the transverse 
cam slot 37 which is formed in the inner surface of the rear cover wall 
plate 21. The gripper arm 16 is provided with the longitudinally extended 
portion 123 which is provided with a pair of transverse threaded holes 
124. 
As shown in FIGS. 1 and 2, the gripper arm 15 has operatively mounted 
thereon a gripper jaw 134. The gripper jaw 134 is carried on a mounting 
arm 127, which is releasably secured to the longitudinal gripper arm 
portion 111 by a pair of suitable machine screws 128. The machine screws 
128 are slidably mounted through bores 129, which are formed through the 
lower end of the mounting arm 127, and they extend into threaded 
engagement with the threaded bores 112 that are formed through the 
longitudinal gripper arm portion 111. The mounting arm 127 has an 
integral, outwardly extended, perpendicular flange 130, which rests on the 
upper end of the longitudinal gripper arm portion 111. The gripper jaw 134 
is releasably secured to the outer end of the mounting arm 127 by a pair 
of suitable machine screws 131, which pass through bores 132 formed 
through the upper end of the mounting arm 127 and into threaded engagement 
with threaded bores 133, which are formed in the outer side of the jaw 
134. The gripper jaw 134 is shown as being provided with a V-shaped seat 
135 for engagement with the rounded outer diameter or surface of a 
cylindrical workpiece, as the workpiece 11. 
As shown in FIGS. 1 and 2, the gripper arm 16 has operatively mounted 
thereon a gripper jaw 145. The gripper jaw 145 is carried on a mounting 
arm 138, which is releasably secured to the longitudinal gripper arm 
portion 123 by a pair of suitable machine screws 139. The machine screws 
139 are slidably mounted through bores 140 which are formed through the 
lower end of the mounting arm 138, and they extend into threaded 
engagement with the threaded bores 124 that are formed through the gripper 
arm portion 123. The mounting arm 138 has an integral, outwardly extended, 
perpendicular flange 141 which rests on the upper end of the gripper arm 
longitudinal portion 123. The gripper jaw 145 is releasably secured to the 
outer end of the mounting arm 138 by a pair of suitable machine screws 
142, which pass through bores 143 formed through the upper end of the 
mounting arm 138 and into threaded engagement with threaded bores 144, 
which are formed in the outer side of the gripper jaw 145. The gripper jaw 
145 is shown as being provided with a V-shaped seat 146 for engagement 
with the rounded outer surface or outer diameter of a cylindrical 
workpiece, as the workpiece 11. 
The mounting arms 127 and 138, and the gripper jaws 134 and 145, may be 
made from any suitable material as, for example, aluminum. 
In use, the gripper apparatus 10 would be operatively mounted on a 
conventional robotic arm, or similar structure, for moving said apparatus, 
as desired. In order to grip the workpiece 11, pressurized fluid is 
admitted into the lower port 93 for operating the power cylinder 18 in an 
upward direction, so as to move the gripper operator 14 upwardly, to the 
position shown in FIG. 2, for bringing the gripper jaws 134 and 145 into 
gripping engagement with the workpiece 11. The robotic arm may then be 
moved to a desired position for putting the workpiece 11 in a selected 
position for a sequential manufacturing operation, or the like. At the new 
selected position, the pressurized fluid would be exhausted from the lower 
port 93, and pressurized fluid would be admitted into the upper port 92 
for operating the power cylinder 18 in a downward direction to move the 
gripper operator 14 downwardly, to the position shown in FIG. 1, for 
releasing the workpiece 11. 
The gripping seats or faces 135 and 146 on the gripper jaws 134 and 145, 
respectively, may be changed in accordance with the outer shape of a 
workpiece 11 to be gripped by the gripper apparatus 10. For example, if 
the workpiece 11 were to have parallel straight sides, then the gripper 
jaws 134 and 145 would be provided with straight gripping faces instead of 
the V-shaped seats or faces 135 and 146. 
The range of the linear movement of the gripper jaws 134 and 145 may be 
controlled or changed by merely adding different size gripper jaws, which 
may be shorter or longer, in the transverse direction, as desired. The 
linear or parallel inward and outward movements of the gripper jaws 134 
and 145 are effected by the 45 degree disposition of the gripper arm 
portions 109 and 119 of the gripper arms 15 and 16, respectively, and the 
mating 45 degree disposition of the aforedescribed cam rollers on the 
gripper operator 14 which also function with the cam rollers 121 and 115 
in the transverse cam slots 37 and 41, respectively. The rollers carried 
on the gripper operator 14 for retaining the gripper arm portions 109 and 
119 in a 45 degree deposition provide a rolling action relative to said 
gripper arms, with a minimum of friction between the moving internal 
moving parts in the gripper apparatus housing. The aforedescribed roller 
action of the internal parts of the gripper apparatus 10 of the present 
invention provides a low friction gripper apparatus which results in 
obtaining an optimum gripping force from the power cylinder 18. 
It will be understood that the gripper jaws 134 and 145 may be selectively 
mounted on the outer side of the mounting arms 127 and 138, to provide an 
inner diameter gripper apparatus. In an embodiment with the gripper jaws 
134 and 145 mounted on the outer side of the mounting arms 127 and 138, 
the movement of the gripper operator 14 would be reversed for releasing 
and gripping the internal diameter of a workpiece. That is, the power 
cylinder 18 would be operated so as to move the gripper jaws 134 and 145 
inwardly to a position adjacent each other, and then to grip the inner 
diameter of a workpiece the gripper arms 15 and 16 would be moved 
outwardly by the power cylinder 18, as shown by the outward positions in 
FIG. 1, until the gripper jaws 134 and 145 engage the inner diameter of 
the workpiece.