US3554529A

US3554529A - Retractable and swingable clamps

Info

Publication number: US3554529A
Application number: US735352A
Authority: US
Inventors: Vitas T Thomas; Robert A Lovdahl
Original assignee: Tomco Inc
Current assignee: Tomco Inc
Priority date: 1968-06-07
Filing date: 1968-06-07
Publication date: 1971-01-12
Anticipated expiration: 1988-01-12

Abstract

Disclosed herein is a force transmitting device comprising a base adapted to be mounted on a work surface, a clamp arm mounted on said base for movement from an inoperative to an operative position, a force ram to pivot the clamp arm when in the operative position and a hydraulic circuit to move the arm and force ram in sequence.

Description

United States Patent 1111 ,55 ,5

[72] Inventors Vitas T. Thomas [56] References Cited Robert A. Lovdahl, Racine, Wis. UNITED STATES PATENTS [211 PP 735,352 2,967,464 1/1961 Marmillon 269/34x Filed June 7,1968 3,104,589 9/1963 Rudd 92/136X 1 W Jan-1211971 3,173,673 3/1965 Northern et al. 269/32 Asslgnee P '"F- 3,281,140 10/1966 Smierciak 269/24 f 3,336,022 8/1967 Tridgell.... 269/32 3,362,301 1/1968 K0hlit2..... 269/24X 2,620,698 12/ 1952 Warner 74/422X Primary Examiner-Robert C. Riordon Attorneys-Ronald E. Barry and James E. Nilles [54] :WINGABLE CLAMPS ABSTRACT: Disclosed herein is a force transmitting device g lg comprising a base adapted to be mounted on a work surface, a [52] U.S. Cl....; 269/32 clamp arm mounted on said base for movement from an in- [51] Int. Cl B25b 5/06 operative to an operative position, a force ram to pivot the [50] Field of Search 269/24, 20, clamp arm when in the operative position and a hydraulic circuit to move the arm and force ram in sequence.

RETRACTABLE AND SWINGABLE CLAMPS BACKGROUND OF THE INVENTION This invention relates to force transmitting devices for engaging and holding a work piece securely in position during a machining operation. The work piece is normally held in position on the work surface by a mechanical clamp or fixture which is attached to the work surface. The work area available on the work surface has made it difficult to use hydraulic or automatic securing devices to hold the work piece in position.

SUMMARY OF THE INVENTION The invention disclosed herein provides a force transmitting device for holding an object in a fixed position on a work surface or for performing a working function on a work piece. More specifically, the force transmitting device includes a base having an arm pivotally connected to a shaft which is rotatably mounted in the base with a hydraulic ram operatively positioned for movement into engagement with one end of the arm. A hydraulic circuit assembly is provided in the base to rotate the shaft and actuate the ram in sequence to thereby move the clamp arm from an inoperative to an operative position and apply force to the arm when in the operative position. This arrangement in the sequence of movement of the ram and arm makes it possible to mount the device in a number of positions on the work surface without obstructing the work surface area and to automatically move the arm to the operative position before any force is applied.

Other objects and advantages will become apparent from the following detailed description when read in connection with the accompanying drawings in which:

FIG. 1 is a perspective view of the force transmitting device.

FIG. 2 is a right side view in section of the hydraulic pressure circuit for a retractable type clamp arm.

FIG. 3 is a left side view in section of the hydraulic retracting circuit for a retractable type clamp.

FIG. 4 is a front view partly in section of the retractable type clamp.

FIG. 5 is a side view in section of the hydraulic pressure circuit for a swing-type clamp.

FIG. 6 is a front view in section of the swing-type clamp.

FIG. 7 is a view in section of a part of the base showing the power ram assembly.

DETAILED DESCRIPTION OF THE INVENTION Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structure. The scope of the invention is defined in the claims appended hereto.

The force transmitting device of this invention as shown in FIG. 1 includes a base 10 having a clamp arm 12 pivotally mounted on the base 10 for movement from an inoperative position, to an operative position in either a swinging or advancing motion. Once the arm 12 has been moved to the operative position, it is pivoted by means of a force ram assembly 14 located in the base 10 to hold an object 16 securely in position between the toe 18 of the clamp arm 12 and a work surface 15.

The force ram assembly 14 as shown in FIG. 8 can be used with a force transmitting device having either a swinging or an advancing-type movement for the arm 12 and includes a ram 20 having a piston head 22 positioned in a cylindrical opening 24 in the base 10. The piston head 22 is sealed in the cylindrical opening 24 by means of a seal ring 26 provided in a groove 28 in the piston head 22 with a retainer or backup ring 30 positioned in the groove 28 to prevent extrusion of the seal ring 26. The ram 20 is biased into the opening 24 by a return spring 32 positioned between the piston head 22 and a retainer cap 34 screwed into a threaded section 36 in the opening 24. O-ring seals 38 are provided between the retainer cap 34, base 10 and ram 20 to prevent foreign matter from entering the space 40 between the retainer cap 34 and the piston head 22. v

The ram 20 is moved out of theopening 24 and into engagement with the arm 12 by admitting hydraulic fluid under pressure through a passage 44 into a space 46 provided between the piston head 22 and the base 10 by a button 48 located on the piston head 22. The force ram 20 is returned by the spring 32 or by admitting hydraulic fluid under pressure through a passage 52 into the space 40. The seals 38 are required between the retainer cap, base and ram only when the ram 20 is returned by hydraulic fluid.

The clamp arm 12 can be mounted to be moved either horizontally in a swinging motion or vertically in an advancing motion from an inoperative position to an operative position for engagement with the work piece 16. Referring to FIGS. 2 through 4, a vertically moveable or advancing type clamp arm 12 is shown. More specifically, the arm 12 is pivotally secured to a link 54 by a pin 56 positioned in an aperture 58 in the link 54 and aperture 60;in arm 12. The pin 56 is retained in the

apertures

58 and 60 by a spring-type ball plunger 62 which engages a groove in pin 56 to allow for easy removal of the pin 56 from the arm. The arm 12 is biased into engagement with the force ram 20 to eliminate any play in the arm by means of a spring 55 positioned between the arm 12 and the link 54.

The link 54 is secured to a shaft 64 which is mounted for rotary motion in passage 66 in the base 10. The shaft 64 is rotated to move or swing the arm 12 between the operative and inoperative positions by the selective hydraulic movement of either cylindrical rack'68 or cylindrical rack 70 which are positioned to engage gear teeth 72 and 74, respectively, provided on each end of the shaft 64.

The arm 12 is moved from the inoperative to the operative position by the rack 68 which is mounted in a passage 76 in the base 10 in engagement with the gear teeth 72. A piston head 78 having an O-ring seal 80 provided in a groove 82 in its outer periphery is positioned in the passage 76 in abutting engagement with the cylindrical rack 68 and a cap or plug 84 is used to close the open end of the passage 76. The rack 68 is moved to rotate the shaft 64 and move the arm 12 to an operative position by admitting hydraulic fluid under pressure into passage 76 through passage 86. The force of the hydraulic fluid will act on piston head 78 moving the rack 68 to the right in FIG. 2.

The arm 12 is moved from the operative to the inoperative position by the rack 70 (FIG. 3) which is positioned in a passage 88 in the base 10 in engagement with gear teeth 74. A piston head 92 having an O-ring 94 provided in a groove 96 in its outer periphery is positioned in passage 88 in abutting engagement with the rack 70 and caps 90 and 91 are used to close the ends of passage 88. The arm 12 is biased toward the inoperative position by a spring 98 provided between the piston head 92 and cap 90. The rack 70 and piston head 92 are moved upward in FIG. 3 against the bias of spring 98 by the movement of rack 68 when the arm 12 is moved from the inoperative to the operative position. The arm 12 can be moved to the inoperative position either by the force of the compressed spring 98 or by the admission of hydraulic fluid or air under pressure into passage 88 through passage 100.

A positive stop is provided in the advancing movement of the arm 12 by means of an extension 95 provided on piston head 92 which engages the inner surface 97 of the cap 90. Retracting movement of the arm 12 is positively stopped by the engagement of rack 70 with cap 90. The racks 68 and 70 are shown as cylindrical racks having teeth along one side, however, cylindrical racks having arcuate or circumferential teeth could also be used in the passages.

Referring to FIGS. 5 and 6, a clamp arm 12 is shown mounted for horizontal or swing-type movement. More particularly, the clamp arm 12 is pivotally secured to a pivot shaft 102 by means of a pin 56 positioned in an aperture 60 in the arm 12 and an aperture 104 in the pivot shaft 102. The pin 56 is retained in the

apertures

60 and 104 by a spring-type ball plunger 62 as described for the advancing-type clamp. The

pivot shaft 102 is positioned in an aperture 106 in the base 10 and is seated on a retainer ring 108 secured in a recess 109 in the base 10. A split ring 110 is positioned in a groove in the shaft 102 to hold the shaft in the base. The shaft 102 is rotated in the aperture 106 to swing the arm 12 through 90 from an inoperative position remote from the work piece to an operative position adjacent the work piece by means of a cylindrical rack 112 which engages gear teeth 114 provided on the shaft 102.

In this last regard, the cylindrical rack 112 is positioned within a passage 116 in the base 10 with the rack 112 positioned to matingly engage the gear teeth 114 provided on the shaft 102. The rack 112 is positioned for axial motion in the passage 116 which is closed at each end by plugs 124 and sealed by O-ring seals 126. Piston heads 117 and 118 are provided at the ends of the rack 112 with a seal ring 120 positioned in a groove 122 provided in the piston heads 117 and 118. The rack 112 is moved in the passage 116 to rotate the shaft 102 and arm 12 to the operative position by admitting hydraulic fluid under pressure through a passage 86 into a space 128 provided between plug 124 and the piston head 118. The shaft 102 is rotated in the opposite direction to move the arm 12 to the inoperative position by admitting hydraulic fluid under pressure through passage 100 into a space 130 provided between piston head 117 and plug 124. The direction of motion of the rack 112 in the passage 1 16 can be selected to rotate the shaft 102 clockwise or counterclockwise depending on the direction of motion required for the arm 12. Return motion of the rack 112 may also be accomplished by positioning a compression spring 132 in space 130 or by ad mitting hydraulic fluid under pressure into the space 130 in the passage 116 through a passage 100. The inoperative position may be at either side of the operative position, as required.

The extent of motion of the rack 112 in the passage 116 is limited by the elongate extensions 115 and 119 provided on piston heads 117 and 118, respectively. The extensions 115 and 119 are positioned to engage plugs 124 at each end of the passage providing both a positive stop in the movement of the rack 112, as well as the spaces 128 and 130 for the admission of hydraulic fluid.

If the initial force of the mass of the arm 12 is large, an undue stress can be imposed on the gear teeth. To minimize this stress, a blocking pin (not shown) is mounted on the top of the base 10 and extends into the space within the bottom of the arm 12. The blocking pinis positioned to engage the inside surface of either side of the arm depending on the direction of rotation.

The motion of either the swing-type arm or the advancingtype arm from the inoperative position to the operative position is accomplished by means of a basic hydraulic circuit as shown in FIGS. 2 and 7. This circuit includes the main passage 86 connected at one end to a source of hydraulic fluid under pressure (not shown) and at the other end to one of the passages 76 (H6. 2) or 116 (FIG. 5). Hydraulic fluid from the main passage 86 is fed to the passage 44 for the hydraulic ram 20 through passages 134 and 136. Hydraulic fluid in passage 86 is initially prevented from entering passages 134 and 136 by means of a ball-type check valve 138 in passage 134 until the pressure in passage 86 has built up sufficiently to open the check valve 138. The check valve 138 includes a ball 140 which is biased into engagement with a valve seat 142 in the passage 134 by a spring 144 positioned between the ball 140 and a cap 146 closing and sealing the passage 134. The check valve 138 is set to prevent hydraulic fluid from entering the passage 44 and actuating the force ram 20 until the rack 68 or 112 has moved far enough to move the arm 12 to the operative position. The check valve 138 will then open because of the rise in pressure when arm 12 stops, and hydraulic fluid will flow through

passages

134, 136 and 44 into the space 46 beneath the piston head 22 on the ram 20 to move the ram 20 into engagement with arm 12 and pivot the arm 12 into engagement with the work piece 16. Hydraulic fluid, in passage 86 is prevented from entering passage 136 through return passage 148 by means of a ball-type check valve 146 located in passage 136. Check valve 138 includes a ball biased into engagement with valve seat 137 by a spring 139 retained in passage 136 by plug 133.

When the work piece 16 is to be released from the work surface 15, the hydraulic pressure on the power ram 20 is relieved first to clear the ram from the path'of movement of the arm 12. This is accomplished by thearrangement of the check valves in the hydraulic circuit. When pressure is relieved in the passage 86, the spring 32 on the power ram 20 will force the ram 20 toward the bottom of the opening 24 forcing the fluid out through the passage 44 into passage 136. The passage 134 is closed by check valve 138 and ball-type check valve 146 in passage 136 will open allowing the fluid to flow through return passage 148 back to passage 86. Once the pressure of the fluid in passages 86 and 76 or 116 starts to drop, the fluid in the passage 76 or 116 will flow into passage 86 allowing the arm 12 to swing or retract to the inoperative position.

The return motion of the swing or advancing type arm 12 is accomplished by means of a hydraulic circuit as seen in FlGS. 3 and 7. This circuit includes the main passage 100, a return passage 150, and bypass passages 152 and 154. A ball-type check valve 156 is provided in passage 100 to prevent hydraulic fluid from flowing into the passages 88 or 116 until the power ram 20 has been fully retracted into the housing. Hydraulic fluid is prevented from entering the passages 88 or 116 by means of a check valve 155 located in return passage 150. When the pressure builds up sufficiently in the return passage 150 to unseat check valve 155, the fluid will flow through passages 154 and 152 back to passage 100 and into the passage 88 or 116 to move rack 70 or 112 and rotate

shaft

64 or 102 to move the arm 12 to an inoperative position. When the arm 12 is moved to the operative position, the

shaft

66 or 102 is rotated moving rack 70 or 112. Any fluid in passage 88 or 116 will be forced out through passage 100 past ball-type check valve 156. If air return is contemplated, the passage 52 to the power ram is normally blocked and air is only used to move rack 70 or 112. The ram 20 is returned by the bias of the spring 32. I

We claim:

1. A work holding device for clamping a work piece to a work surface, said device comprising a base adapted to be mounted on the work surface, a shaft mounted in said base for movement between an operative and an inoperative position, means for rotating said shaft, an arm operatively connected to said shaft for pivotal movement between an operative and an inoperative position, a force ram mounted for movement into engagement with one end of said arm when said arm is in the operative position, means for hydraulically actuating said rotating means and said ram in sequence to move said arm to the operative position and means for hydraulically retracting said ram and said rotating means in sequence to move said arm to the inoperative position.

2. A device according to claim 1 wherein said rotating means includes a number of gear teeth on said shaft and a cylindrical rack operatively positioned to engage said gear teeth and having a piston head at each end.

3. A device according to claim 1 wherein said rotating means includes gear teeth at each end of said shaft, a first cylindrical rack positioned to engage the gear teeth at one end of said shaft to rotate said shaft to the operative position and a .second cylindrical rack positioned to engage the gear teeth at the other end of said shaft to rotate said shaft to the inoperative position.

4. A device according to claim 3 wherein said hydraulic means is operatively connected to move said first cylindrical rack before said ram is moved to the operative position.

5. A device according to claim 4 wherein said hydraulic retracting means is operatively connected to move said second rack after said ram is moved to the inoperative position.

6. The device according to claim 2 wherein said hydraulic actuating means is operatively connected to apply pressure to said piston head at one end of said rack before applying pressure to said ram and said hydraulic retracting means is connected to apply pressure to said piston head at the other end of said rack after the said ram has been retracted.

Claims

3. A device according to claim 1 wherein said rotating means includes gear teeth at each end of said shaft, a first cylindrical rack positioned to engage the gear teeth at one end of said shaft to rotate said shaft to the operative position and a second cylindrical rack positioned to engage the gear teeth at the other end of said shaft to rotate said shaft to the inoperative position.

6. The device according to claim 2 wherein said hydraulic actuating means is operatively connected to apply pressure to said piston head at one end of said rack and said hydraulic retracting means is connected to apply pressure to said piston head at the other end of said rack.

7. The device according to claim 6 wherein said hydraulic actuating means is operatively connected to apply pressure to said piston head at one end of said rack before applying pressure to said ram and said hydraulic retracting means is connected to apply pressure to said piston head at the other end of said rack after the said ram has been retracted.