US3807719A

US3807719A - Clamp

Info

Publication number: US3807719A
Application number: US00215724A
Authority: US
Inventors: R Williamson
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-01-06
Filing date: 1972-01-06
Publication date: 1974-04-30
Anticipated expiration: 1991-04-30

Abstract

A clamp or the like having a pair of pivotally movable jaws that are adapted to engage a workpiece. A cylinder is provided for actuating the jaws and operating means interconnect the cylinder with the jaws. The operating means includes means for amplifying the force applied by the cylinder and for balancing the load applied to the workpiece by the jaws.

Description

[451 Apr. 30, 1974 United States Patent [191 Williamson 2,929 422 3/1960 Tyler et a1. 2,941,432 6/1960 Williamson 1,075,506 10/1913 Smith [22] Filed: Jan. 6, 1972 Primary ExaminerRoy Lake [21] Appl. No.: 215,724

Assistant ExaminerNeil Abrams Attorney, Agent, or Firm-l-lamess, Dickey & Pierce ABSTRACT A clamp or the like having a pair of pivotally movable jaws that are adapted to engage a workpiece. A cylinder is provided for actuating the jaws and operating means interconnect the cylinder with the jaws. The operating means includes means for amplifying the force applied by the cylinder and for balancing the load applied to the workpiece by the jaws.

m ma nm l B m S u 7 W8 m 2 b E 4 x m mm B B m HP 6 "a E 2 "u 5 u" mT H R h eD U R u E m H H u N l C lo U .M

U mm

11 l] l 2 00 6 5 55 5 .l [.l.

2,633,879 4/1953 Andrus 269/31 7 Claims, 4 Drawing Figures CLAMP BACKGROUND OF THE INVENTION This invention relates to a clamp and more particularly to an improved and simplified clamp.

Clamps are used for a variety of functions and purposes. In addition to holding workpieces, they may be employed for forming or sizing operations. It is not uncommon to have a power actuator for operating the clamp jaw or jaws. Furthermore, it has been proposed to incorporate force amplifiers between the power actuator and the clamp jaws. My US. Pat. No. 2,941,432 issued June 2l, 1960 shows such a clamp. The clamp shown in that patent, however, is relatively large and thus has certain limitations.

It is, therefore, a principal object of this invention to provide an improved compact clamp assembly.

It is another object of the invention to provide a clamp assembly that has a force amplification built into it.

Frequently clamps are employed that have a plurality of jaws that engage the clamped member at different angles relative to each other. Previously proposed clamps of this type have not incorporated any mechanism for balancing the force applied by the respective jaws to the workpiece. As a result, with these previously proposed clamps it would be possible for one jaw to be out of engagement with the workpiece while another jaw applied an excessive force to the workpiece.

It is, therefore, a further feature of this invention to provide a clamp mechanism having a plurality of jaws in which the load applied to the workpiece by the respective jaws is accurately proportioned.

BRIEF SUMMARY OF THE INVENTION This invention is adapted to be embodied in a clamp or the like that is adapted to engage a workpiece. The clamp includes a jaw that is supported for movement between an open position and a clamping position. A pivotally supported lever is provided that is adapted to receive a force for operating the clamp jaw. This lever is connected to the clamp jaws by a cam and follower for amplifying the force applied by the lever to the clamp jaw.

Another feature of the invention is adapted to be embodied in a clamp that is adapted to engage angularly related surfaces of a workpiece with predetermined forces. The clamp comprises first and second jaws that are supported for movement between an opened position and a clamping position. Operating means move the jaws between their positions. The operating means includes force amplifying means operatively connected to one of the jaws for amplifying the force applied by the one jaw to the workpiece and means responsive to the engagement of the one jaw .with a workpiece for transmitting motion into movement of the other ofthe aws.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a clamp embodying this invention showing the clamp jaws in their closed or clamping positions.

FIG. 2 is a side elevational view, on a smaller scale, of the clamp shown in FIG. 1 illustrating the clamp jaws in their opened position.

FIG. 3 is a cross sectional view taken along the line 3-3 of FIG. 1.

FIG. 4 is a cross sectional view taken along the line 4-4 of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A clamp embodying this invention is identified generally by the reference numeral 1l. In the illustrated embodiment the clamp 11 is comprised of a first jaw 12 and a second jaw 13. The jaws l2 and 13 are formed froma steel plate. The

jaws

12 and 13 are supported by a base assembly, indicated generally by the reference numeral 14. The base assembly 14 includes a pair of identically shaped plates 15 that carry pivot pins 16 and 17 on which the

jaws

12 and 13 are pivotally supported. The base 14 also includes a pair of spaced plates 18 that are affixed to the plates 15 by means of bolts and nut assemblies 19 and 21.

The plates 18 have upwardly extending portions that support a trunnion 23 by means of pins 24. The trunnion 23 is affixed to a pneumatic cylinder assembly 25 that is operated in any known manner and which includes a reciprocating piston rod 26. a

The piston rod 26 is operatively connected to the jaws l2 and 13 to pivot them between their opened position (FIG. 2) and a closed or clamping position (FIG. 1) by means of an operating mechanism. The operating mechanism includes a pair of identically shaped bellcranks 27 that are connected by means of a pivot pin 28 to a clevis 29. The clevis 29 is affixed to the outer end of the piston rod 26. The opposite ends of the bellcranks 27 carry a roller follower 31 on a pivot pin 32. The roller follower 31 is received in a cam groove 33 formed in the jaw 12. Movement of the bellcranks 27, therefore, transmit movement to the jaw 12 in a relationship which will be described in a manner which will become apparent as this description proceeds.

A pivot pin 34 provides a pivotal connection between the intermediate portion of thebellcranks 27 and the jaw 13. The plates 18 are formed with enlarged apertures 35 so as to permit the pivot pin 34 to be locked in place and to permit free movement of the pivot pin.

A pin 37 is affixed to the jaws 13 adjacent to the pivot pin 34. The pin 37 extends through larger diameter apertures 38 formed in the frame 14 for a reason which will become well apparent as this description proceeds.

A leaf spring 39 is carried by the base assembly 14 and is held in place by a pair of

pins

41 and 42. The leaf spring is juxtaposed to the jaw 12. The jaw 12 will engage and deflect the leaf spring 39 when moved to its fully opened position (FIG. 2). v

The jaws l2 and l3-are provided with

attachment members

43 and 44, respectively, that permit hardened inserts to be'affixed to these jaws. These hardened inse'rts (not shown) perform the actual gripping function with the workpiece. A similar attachment device 45 is carried by the base assembly 14 so as to receive a further hardened insert for assisting in locating and holding of the workpiece.

OPERATION FIG. 2 illustrates the mechanism in its retracted or opened position. The piston rod 26 has been retracted and each of the

jaws

12 and 13 has been pivoted to its opened position. When a workpiece is in place, the cylinder assembly is actuated so as to move the piston rod 26 downwardly. When this occurs, the bellcranks 27 will pivot generally about the pivot pin 34 and the roller 31 will traverse the cam slot 33 in the jaw 12. The cam slot is shaped so that the jaw 12 will first be pivoted about the pivot pin 16 at a rapid rate of speed with a very small force amplification.

At the same time the bellcrank 27 pivots about the pivot pin 34 a force reaction will be generated on the jaw 13 through this pivot pin. This force reaction will cause the jaw 13 to begin pivotal movement toward its closed position.

The initial closing operation continues until the roller 31 reaches a second portion of the cam slot 33 which portion is configured so as to reduce the rate of movement of the jaw 12 and to increase the force amplification. The movement of the jaw 12 continues at this slower rate and the hardened inserts carried by this jaw will engage the workpiece. At this time, pivotal movement of the jaw 12 about its pivot pin is resisted and a reaction is transmitted to the jaw 13. The reaction is generated by the pivotal movement of the bell crank 27 about the roller 31 and creates a force acting through the pivot pin 34 that insures that the hardened inserts carried by' this jaw engage the workpiece. The bellcrank 27 will, in effect, float and insure that the jaws l2 and 13 apply substantially equal forces to the respective engaged sides of the workpiece. The force applied to the workpiece may be used merely to clamp it or may be used to provide both a clamping and sizing operation. 7 I

When it is desired to open the jaws, the piston rod 26 is retracted and movement in an opposite sense will occur. The jaw 13 will tend to open first inasmuch as the bellcrank 27 initially tends to pivot about the pivot pin 32 which carries the roller 31. This opening movement will continue until the pin 37 strikes the sides of the apertures 38 and prevents further opening movement. Continued movement of the bellcrank 27 will then occur about the pivot pin 34 and full opening of the jaw 12 will be accomplished. This jaw strikes the spring 39 as it reaches its fully opened position to cushion the final movement of this jaw. In addition, the orientation of the elements is such that the spring 39 exerts a resilient force that tends to hold the jaws in their opened position. The spring 39 tends to rotate the jaw 12 but the inclination of the cam surface 33 and its cooperation with the roller 31 cooperates with the spring force to retain the jaws l2 and 13 in their opened positions.

' propriately changing the location of the pivot points of the various elements. In addition, the angle of engagement of the jaws with the workpiece can be appropriately changed.

In some instances it may be desirable to operate only one jaw. By inserting a pin in place of the pin 37 of a diameter equal to the diameter of the aperture 38 the jaw 13 will be precluded from pivotal movement. The jaw 12 will be freely operable in the aforedescribed manner, however. The force amplification mechanism permits the use .of smaller pneumatic cylinders or, if desired, the clamp'can be manually actuated. By suitably changing the shape of the cam groove variations in the rate of closing of the jaws and of the force amplification may be effective.

Various other changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.

1 claim:

1. A clamp or the like adapted to engage a workpiece comprising a jaw, means supporting said jaw for pivotal movement between an opened position and a closed position, a bell-crank supported for pivotal movement about a pivot axis offset from the pivot axis of said jaw, cam and follower means operatively connecting one end of said bellcrank to said jaw for moving said jaw between an opened position and a closed position in response to pivotal movement of said bellcrank at a predetermined force ratio, means for applying a force to the other arm of said bellcrank and spring means engaged by said jawwhen said jaw moves to its opened position for cushioning the opening movement of said jaw and for holding said jaw in its opened position.

2. A clamp as set forth in claim 1 further including a second jaw supported for pivotal movement between an opened position and a closed position and means of interrelating the movement of said first jaw with the movement of said second jaw.

3. A clamp'as set forth in claim 2 wherein the means for interrelating the movement of the first and second jaws includes means for providing a pivotal connection between the pivot point of the bellcrank and the second aw.

4. A clamp as set forth in claim 3 further including means for selectively precluding pivotal movement of the second jaw whereby said second jaw stays ina fixed position.

5. A clamp as set forth in claim 3 wherein the bellcrank and jaws are formed from steel plates.

6. A clamp or the like adapted to engage angularly related surfaces of a workpiece at predetermined forces, said clamp comprising first and second jaws, means supporting said jaws for movement between an opened position and a clamping position, an operating means for moving said jaws between said positions, said operating means including a pivotally supported lever to which a force is applied, including a cam and follower connection between said lever and one of said jaws for amplifying the force applied by said one jaw to the workpiece and means responsive to the engagement of said one jaw with a workpiece for transmitting motion from said force amplifying means into movement of the other of said jaws.

7. A clamp as set forth in claim 6 wherein the lever has a pivotal connection to the second jaw.

Claims

1. A clamp or the like adapted to engage a workpiece comprising a jaw, means supporting said jaw for pivotal movement between an opened position and a closed position, a bell-crank supported for pivotal movement about a pivot axis offset from the pivot axis of said jaw, cam and follower means operatively connecting one end of said bellcrank to said jaw for moving said jaw between an opened position and a closed position in response to pivotal movement of said bellcrank at a predetermined force ratio, means for applying a force to the other arm of said bellcrank and spring means engaged by said jaw when said jaw moves to its opened position for cushioning the opening movement of said jaw and for holding said jaw in its opened position.

3. A clamp as set forth in claim 2 wherein the means for interrelating the movement of the first and second jaws includes means for providing a pivotal connection between the pivot point of the bellcrank and the second jaw.

4. A clamp as set forth in claim 3 further including means for selectively precluding pivotal movement of the second jaw whereby said second jaw stays in a fixed position.