Universal gripper

A universal gripper has a movable arm locked in a gripping position by abutting against a movable blocking member. A pair of pivoting arms are maintained in their gripping positions by a blocking member being linearly slid between ends of the arms. Varying movable arm configurations can be easily interchanged with each other and mounted to a body by way of a single fixed pivot pin. The opening angle of a gripper arm can be mechanically limited to various positions by selective positioning of an adjustment member.

BACKGROUND AND SUMMARY OF THE INVENTION 
This invention relates generally to grippers and specifically to a powered 
gripper having a moving arm and a blocking member. 
Automated or powered grippers have been commonly used to grip or retain 
work pieces, such as sheet metal, polymeric parts and the like in checking 
fixtures, gauging stations, welding stations and punching machines. Such 
grippers have also been used to transfer work pieces between stations when 
mounted to a robotic arm. 
Many existing grippers are powered by hydraulic or pneumatic fluid devices. 
Furthermore, known grippers often employ one or more moving arms which 
move in response to piston-type actuation. Examples of such grippers are 
disclosed in U.S. Pat. No. 5,516,173 entitled "Gripper" which issued to 
Sawdon on May 14, 1996 (the disclosure of which is hereby incorporated 
herein by reference); as well as in U.S. Pat. No. 5,072,652 entitled 
"Gripping Device Having Impact Cushioning Means" which issued to Blatt on 
Dec. 17, 1991; U.S. Pat. No. 3,635,514 entitled "Dual Grip Automation Jaw 
Swivel Assembly" which issued to Blatt on Jan. 18, 1972; and U.S. Pat. No. 
3,013,835 entitled "Power Operated Jaw Assembly" which issued to Blatt on 
Dec. 19, 1961. 
It has recently become desirable to prevent the gripper arms from opening 
if there is a loss of fluid pressure. It would also be desirable to 
mechanically limit the movement of the gripping arms in various positions 
independent of the inaccuracies of fluid pressure upon the piston. It 
would further be desirable to easily interchange differing gripper pad 
configurations. However, many traditional grippers fail to fully achieve 
these desired features. 
In accordance with the present invention, a preferred embodiment of a 
universal gripper has a movable arm locked in a gripping position by 
abutting against a movable blocking member. In another aspect of the 
present invention, a pair of pivoting arms are maintained in their 
gripping positions by a blocking member being linearly slid between ends 
of the arms. In a further aspect of the present invention, varying movable 
arm configurations can be easily interchanged with each other and mounted 
to a body by way of a single fixed pivot pin. In yet a further aspect of 
the present invention, the opening angle of a gripper arm can be 
mechanically limited to various positions by selective positioning of an 
adjustment member. Moreover, another aspect of the present invention 
adjustably mounts a stop onto an external surface of a body for protecting 
a gripper arm from damage. An additional aspect of the present invention 
employs a partially cylindrical gripping pad shape for achieving easy 
interchangeability of differently configured pads. 
The universal gripper of the present invention is highly advantageous over 
traditional grippers in that the moving gripper arms can be maintained in 
their gripping positions even during loss of piston fluid pressure. This 
eliminates undesired opening of the gripper arms which can lead to 
inadvertent dropping and damage of the workpiece. The specific shapes of 
the arms as well as the ability to move the blocking member relative to 
the body and arms allow for improved precision and control of the arm 
movements, smoother and less "jerking" movement of the components so as to 
reduce stress and premature failure. The present invention further 
provides for a more compact assembly, reduced manufacturing and raw 
material costs by eliminating component parts, while insuring precise and 
repeatable gripping pressure on the workpiece whether or not fluid 
pressure is applied to the piston. 
The present invention is also advantageous by maximizing linear and 
pivoting mechanical advantages to supply superior gripping force; for 
example, 80 pounds per square inch of pneumatic force at the piston has 
been found to produce between 300 and 500 pounds of gripping force. 
Addition ally, the arms can be easily interchanged between various 
fixed and pivoting configurations by removing only one otherwise fixed 
pivot pin. Moreover, a variety of gripping pads are interchangeably 
mounted upon the specifically configured arms. The arms and pads can be 
reconfigured within three minutes by pulling a single pin or by removing a 
single screw, respectively. This allows for quick changes so as to 
minimize expensive down time while being adapted for many workpieces. The 
specific shape and fastening of the universal gripper pads encourage easy 
installation and very secure mounting while being adjustment free, thereby 
further minimizing down time while improving gripper precision, which 
leads to improved workpiece positioning and processed quality. Additional 
advantages and features of the present invention will become apparent from 
the following description and appended claims, taken in conjunction with 
the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1 and 2, the first preferred embodiment of a universal 
gripper 81 includes a gripper body 83, a moving upper arm 85, a moving 
lower arm 87, a pivot pin 89, an adjustment or stop pin 91, a tube mount 
93, a swivel 95 and an extension tube 97. Extension tube 97 may be 
stationarily mounted in place to a fixture or be attached to a movable 
robotic arm. 
As can best be observed in FIGS. 8-11, body 83 has a circular cylindrical 
external surface 101 located closest to a proximal end 103 and bifurcated 
legs 105 located closest to a distal end 107. Bifurcated legs 105 are 
separated by a through-slot 109. A central bore 111, having a 
circular-cylindrical shape is internally disposed in a longitudinal 
orientation within body 83. A piston chamber 113 is also disposed within 
proximal end of body 83. A rod passageway 115 longitudinally connects bore 
111 with piston chamber 113. An air inlet/outlet 121 provides access 
between piston chamber 113 and an externally coupled pneumatic or other 
fluid pressure device (not shown). A set of lateral serrations 123 are 
disposed along flattened external surfaces of bifurcated legs 105. 
Serrations 123 have a sixty degree (60.degree.) angle between each other. 
Body 83 is preferably machined on a lathe and then milling machines and 
drill presses from round stock 6061-T651 aluminum. After machining, body 
83 is hard coated or anodized to approximately a Rockwell C hardness of 
70. 
Referring to FIGS. 3, 4, 12 and 13, an end cap 131 is secured to the distal 
end of body 83. An o-ring 133 serves to seal between a peripheral groove 
135 of end cap 131 and piston chamber 113 of body 83. An air inlet/outlet 
137 couples the pneumatic device (not shown) to piston chamber 113. End 
cap 131 is manufactured in the same manner and from the same materials as 
is body 83. 
Referring now to FIGS. 3, 4, 14 and 15, a piston 151 is coaxially disposed 
within piston chamber 113 internal to end cap 131. A peripheral groove 153 
retains an o-ring 155 which seals against the internal surface defining 
piston chamber 113. Accordingly, piston 151 longitudinally and linearly 
travels away from the proximal end of body 83 when air enters inlet 137. 
Similarly, piston 151 travels longitudinally and linearly toward the 
proximal end of body 83 when air is forced into inlet 121. Piston 151 is 
machined on a lathe and then with milling and drill machines from 
6061-T651 aluminum but is not hard coated. 
A slide 171 is shown in FIGS. 3, 4 and 16-19. Slide has a piston rod 173 
and a clevis 175. A longitudinally elongated slot 177 and an aperture 179 
are machined within each branch of clevis 175. Piston rod 173 is bolted to 
piston 151 for coincidental longitudinal and linear movement. Slide is 
machined from 4150 pre-heat treated hot rolled steel with a flash chrome 
finish. 
Referring now to FIGS. 2-5 and 7, a roller assembly 201 includes an inner 
roller 203 and two outer rollers 205, all of which are journalled about a 
roller pin 207. Roller assembly 201 also acts as a blocking member as will 
be later described. A thrust washer 208 is disposed between each adjacent 
pair of rollers. Snap rings 209 are snapped onto the laterally outboard 
ends of roller pin 207 for retaining roller pin 207 to apertures 179 of 
slide 171. Rollers 203 and 205 are made from 6150 hot rolled steel, then 
hardened and ground to a Rockwell C hardness of 54-58. Roller pin 607 is 
made from 12L14 cold finished steel that is carburized and hardened to a 
Rockwell C hardness of 46-50. 
FIGS. 6, 20, 20A, 21, 22 and 34 show first and fourth preferred embodiments 
of arms 85 and 87. The first and fourth preferred embodiments both employ 
pivoting upper and lower gripping arms with the only difference between 
the embodiments being in the ends closest to the gripping pads. Upper arm 
85 has a gripping end 221 and a trailing end 223. A claw 225 joins to a 
thicker lateral thickness of gripping end 221. Claw 225 is defined by a 
first finger 227 and a second off-set and opposing finger 229. An arm 
pivot hole 331 is disposed within finger 229. Finger 227 has an arcuate 
external, peripheral edge 333. A camming surface 335 is disposed along an 
internal edge of claw 225. Camming surface 335 has an arcuate portion 337, 
a five degree (5.degree.) (relative to the longitudinal axis of body 83) 
angled or tapered flat section 339 and a stepped or indented flat section 
341. An angled section 343 of camming surface 335 is disposed along finger 
229. 
In the alternate embodiment shown in FIGS. 20B and 20C, indented section 
341 of camming surface 335 is replaced by a series of radiused grooves 
oriented in a lateral direction across tapered section 339. 
Referring now to FIGS. 6 and 34, lower gripping arm 87 has a claw 361 
defined by fingers 363 and 365. Unlike the unitary claw of upper arm 85, 
claw 361 of lower arm 87 is laterally bifurcated such that claw 225 of 
upper arm 85 can movably pass between claws 361. The camming surface of 
lower arm 87 is generally identical to that of upper arm 85 (with common 
reference numbers used to denote the various sections) with the exception 
that lower arm 87 does not include indented section 341 in its preferred 
embodiment. The arms are preferably cast from 4140 hot rolled steel and 
then hardened to a Rockwell C hardness of 44-48. 
As can be observed in FIGS. 1, 3, 4, 7 and 34, pivot pin 89 pivotably 
couples upper arm 85 and lower arm 87 to body 83. A pair of snap rings 401 
serve to retain pivot pin 89 to body 83. When affixed to body 83, pivot 
pin 89 is maintained in a fixed position and prevented from longitudinal 
or lateral movement. Therefore, in the preferred embodiments, arms 85 and 
87 are only pivotably moved between various open positions (shown in 
phantom in FIG. 3) to a closed gripping position (as shown in solid 
lines). Notwithstanding, pivot pin 89 can be easily removed from body 83 
by use of a simple snap ring pliers. 
This allows for easy interchangeability of the preferred arm embodiments 
which all have a common attachment hole for receiving pivot pin 89. As can 
be further observed, trailing end 223 of each gripping arm 85 and 87 is 
disposed with internal tube body 83 within slot 109. Pivot pin 89 is 
preferably made from 12L14 cold finished steel that is carburized and 
hardened to a Rockwell C hardness of 46-50. 
Referring now to FIGS. 23-25, 28 and 29, second and third preferred 
embodiments of the universal gripper of the present invention are shown 
employing fixed lower arms 421. Each fixed lower arm 421 has bifurcated 
fingers 423 with flat camming surfaces 425 and flat external surfaces 427. 
Each trailing end 429 of lower arms 421 has slot 431 which is inserted 
within the slot of body 83 prior to insertion of pivot pin 89 for 
engagement with a laterally oriented rod 435 secured to body 83 by snap 
rings. 
The arm embodiments of FIGS. 1-5 and 20-25 all have gripping ends 221 with 
a partially circular channel 501 which receives a mating partially 
circular cylindrical external retaining surface of gripping pad 503, the 
various embodiments of which will be described in greater detail 
hereinafter. Channel 501 has a side view C-shape of approximately three 
quarters (3/4) of a circle with an opening. A counter-bore 505 extends 
from a peripheral edge of each arm to the deepest portion of channel 501. 
A threaded anti-rotating bolt 511 is disposed within counter-bore 505 for 
engaging with a threaded hole 513 in gripping pad 503. An enlarged head of 
bolt 511 has a blind hexagonal recess for receiving a mating wrench. 
Accordingly, bolt 511 and gripping pad 503 are allowed to rotate plus or 
minus five degrees (5.degree.) in a longitudinal direction but are 
prevented from moving laterally relative to the arms once assembled 
together. However, the various pad embodiments can be easily removed and 
interchanged with each other by disengagement of the single bolt in each 
arm. Bolt 511 is preferably made from 4150 pre-heat treated hot rolled 
steel having a Rockwell C hardness of 28-32 and with a black oxide 
coating. 
The lower arm embodiments of FIGS. 6, 29 and 30 all use a chisel point 
gripping section 531. No extra gripping pad needs to be attached to each 
arm. For the embodiments shown, one or two conical recesses 533 are 
disposed within gripping portion 531 for alignment with the conical 
projections extending from the gripping pads. The chisel points serve to 
pick up or shovel underneath a workpiece 535 to thereby assist in the 
eventual gripping. 
Stop or adjustment pin 91 can best be observed in FIG. 3, 7, 26 and 27. 
Adjustment pin 91 has a cylindrical shaft 601 with an indented flat 603 
machined within one side. A head 605 has a pair of parallel flat sides 607 
which mate in a keyhole manner with a circumferentially elongated slot 609 
machined in the external surface of body 83. An arrow head is raised or 
recessed within head 605. Adjustment pin 91 is laterally disposed internal 
to body 83 such that shaft 601 and flat 603 bridge across bore 111. A snap 
ring 621 juxtapositioned around a base 623 of adjustment pin 91 retains 
adjustment pin 91 to body 83 and must be removed to reorient or remove 
adjustment pin 91. Shaft 601 and flat 603 are circumferentially surrounded 
by slot 177 of slide 171. 
The operation of the moving arms 85 and 87 in response to linear travel of 
slide 171 and roller assembly 201 can be explained by observing FIGS. 7 
and 31-34. When adjustment pin 91 is removed, as in FIG. 31, slide is 
linearly pushed toward distal end 107 of body 83 such that roller assembly 
201 rides along angled section 343 of each camming surface 335. This 
causes each moving arm 85 (and 87, not shown) to move to a fully opened 
position. 
FIGS. 7 and 32 illustrate adjustment pin 91 oriented in a forty-five degree 
(45.degree.) open position wherein flat 603 faces away from distal end 107 
of body. Accordingly, slide 171 is longitudinally slid toward distal end 
107 until a trailing end of slot 177 abuts against flat 603. Therefore, 
roller assembly 201 only rides along camming surface 335 a predetermined 
distance. Hence, arm 805 (and arm 87, not shown) are only allowed to 
rotate to a forty-five degree (45.degree.) open position relative to a 
longitudinal center line 701. 
FIG. 33 shows adjustment pin 91 oriented in a thirty degree (30.degree.) 
open position wherein linear movement of slide 171 is limited when 
cylindrical shaft 601 abuts against the trailing end of slot 177. Thus, 
roller assembly 201 only opens arm 85 (and arm 87, not shown) to a thirty 
degree (30.degree.) open position. 
Finally, FIG. 34 shows arms 85 and 87 in a gripping or closed position 
engaging the workpiece. In this position, the piston retracts slide 171 
which in turn wedges roller assembly 201 between trailing ends 223 of arms 
85 and 87. Furthermore, center roller 203 engages indented section 341. 
This abutting and wedging action mechanically prevents gripping arms 85 
and 87 from opening up and inadvertently releasing the workpiece even when 
piston pressure is not present. For the fixed lower arm embodiments, 
roller assembly 201 rides along the upper camming surface of each lower 
arm in order to prevent undesired misalignment or lateral movement of 
roller assembly 201 or slide 171. Hence, even with the fixed arm 
embodiments, roller assembly 201 is wedged and abuts between the arms when 
the arms are in a fully gripping position. 
Referring to FIGS. 3-5, 35 and 36, two different embodiments of workpiece 
stops 800 are shown. Each stop embodiment has a central base leg 801 and a 
pair of upper legs 803 thereby defining a generally T-shape. Base leg 801 
has a series of serrations 805 for adjustably engaging with serrations 123 
of body 83. Base leg 801 further has a pair of parallel and longitudinally 
oriented slots 811 laterally off-set from each other. A threaded fastener 
813 has a shaft disposed through longitudinally oriented slots 811 for 
engaging threaded holes 815 and body 83. Accordingly, stops 800 can be 
longitudinally adjusted relative to body 83. Each stop 800 is preferably 
made from 1018CDS steel which is carburized and hardened to a Rockwell C 
hardness of 44-48. Each stop 800 is much thinner than its width. Stops 800 
are meant to protect the softer aluminum body from damage due to insertion 
and removal of the workpieces. 
FIGS. 37-44 illustrate tube mount 93, swivel 95, extension tube 97 and a 
clamp ring 901. Tube mount 93 has a gripper body opening 903 of a 
circular-cylindrical shape for receiving gripper body 83. Until 
tightening, gripper body 83 can be longitudinally moved to various 
positions relative to tube mounts 93. A through-slot 905 extends from 
opening 903. A tube receptacle 907 is also disposed within tube mount 93 
and is split in half by slot 905. Thus, tube mount 93 can be angularly or 
rotatably oriented both in a lateral rotational direction and a 
longitudinal rotational direction relative to swivel 95 and extension tube 
97 prior to tightening of bolts 909 bridging across slot 905. A pair of 
clamp ring portions 901 of tube mount 93 are located within receptacle 907 
for engaging a pair of circumferentially surrounding grooves 931 on an 
external and otherwise spherical surface of swivel 95. Swivel 95 is made 
from 4150 heat treated steel while tube mount is preferably made from 
6061-T651 aluminum which is hard coated. 
FIGS. 44A-47 illustrate a single cone point gripping pad 1001 having a 
single central conical projection 1003 coaxially aligned with a threaded 
aperture 1005. Pad 1001 is preferably made from 8620 cold finished steel 
which is carburized and hardened to a Rockwell C hardness of 58-62. FIGS. 
47A-49 illustrate a double cone point gripping pad 1011 having a pair of 
laterally off-set conical projections 1013 and angled side walls 1015. 
FIGS. 49A-52 illustrate a single standard gripping pad having five rows by 
seven columns of pyramidal projections 1021 projecting from a 
theoretically flat surface 1023 of a pad body 1025. An external retaining 
surface 1027 of pad body 1025 has a circular-cylindrical shape making up 
approximately two-thirds (2/3) of a circle when viewed from the side (see 
FIG. 50). Each angled wall of each pyramid has a ninety degree 
(90.degree.) angle relative to the adjacent wall of the next pyramid. 
FIGS. 52A-54 illustrate a double standard gripping pad similar to that of 
FIGS. 49A-52 except that a pair of pyramidal sections are employed 
laterally outboard of a central flat section containing a threaded 
aperture 1031. Furthermore, with this embodiment, a pair of angled 
outboard side walls are employed. 
FIGS. 54A-57 illustrate a single soft gripping pad 1051 having a steel body 
1053 and a urethane button 1055 fitting within a back tapered chamber 1057 
of body 1053. Button 1055 sits proud of an otherwise flat surface 1059 of 
body 1053. FIGS. 57A-59 illustrate a double soft gripping pad like that of 
the prior embodiment except that a pair of buttons 1071 are positioned 
laterally outboard of a centrally located and threaded aperture 1073. 
While the preferred embodiments of the universal gripper have been 
disclosed, it will be appreciated that various other shapes, parts and 
embodiments may be employed without departing from the spirit of the 
present invention.