US 3570835 A
Description (OCR text may contain errors)
March 16, 1971 MC H N 3,570,835
POWER OPERATED CLAMPING DEVICE Filed Oct. 8, 1968 2 Sheets-Sheet 1 A TTORNE VS Files; Oct.
A. W. M PHERSON POWER OPERATED CLAMPING DEVICE Z2 'lll 2 Sheets-Sheet 2 IN VEN TOR AZfX/M/Df/F 14 A4 P/A'RSO/V ZZ /,MY/
A TTORNEVS United States Patent 3,570,835 POWER OPERATED CLAMPING DEVICE Alexander W. McPherson, Farmington, Mich, assignor to Dover Corporation (De Sta-Co Division) Filed Oct. 8, 1968, Ser. No. 765,802 Int. Cl. 1325b 1/18, /04
US. Cl. 269-32 9 Claims ABSTRACT OF THE DISCLOSURE A power operated clamping device having a multiple mounting face base, a pivotally mounted clamping arm cam actuated to provide high pressure clamping and rapid wide angle opening, and a lost motion impact producing connection for clamp releasing actuation.
BACKGROUND OF THE INVENTION There are many uses for power operated clamps and work holders which are small and compact in size, will provide a wide jaw opening and enable maximum clamping pressures to be obtained and released quickly. However, this combination is difficult to attain with such devices as they are presently known.
Most hydraulic and air actuated piston cylinder arrangements, which are preferred for in-plant uses, require oversized piston cylinders to obtain a sufficient pressure build-up for clamping purposes, or to effect a release of the jaw mechanism, or to enable a work stroke capable of providing a reasonably wide jaw opening. When bell crank or other lever arm arrangements are used, to obtain a greater mechanical advantage, there are added parts subject to fatigue and failure and jaw openings are limited and usually provide restricted access.
In all clamping devices, considerations are also necessary as to how to mount the fixture for best use; particularly where there is an angle block application of the locking arm or jaw member. Friction and wear must be minimal, bottoming out in the cylinder must be avoided, rugged construction is necessary without appreciable added weight, and a simplicity of design is essential for ease of maintenance and a minimum of service problems.
SUMMARY OF THE INVENTION The present invention relates to power operated clamps and like devices, for work holding and other purposes, and in particular to a cam operated mechanism with a Wedge locking feature that has many advantages.
A piston cylinder member is used to actuate a roller mounted cross-pin which extends through a cam slot in an actuating extension arm that serves as a work clamping member. The reciprocable stroke of the cross-pin causes cam actuation of the clamping member and provides an unusually wide jaw opening for a relatively short work stroke.
The cam slot is so provided as to cause the cross-pin to wedge with a locking angle in the slot near the end of its work stroke and to assure clamping pressure before the final lock-up. The wedge stroke variance automatically compensates for wear by allowing an extra travel allowance. A pre-load stop is provided at the extremity of the clamping stroke which enables use of different clamping arms with clamping surfaces that can be accurately machined to the mounting surfaces of the unit.
Upon release, an initial freedom of travel provided for the actuator, before dislodging the wedged cross-pin, provides a high inertial impact that facilitates release and a rapid jaw opening.
These and other abjects and advantages obtained in the practice of this invention will be best understood and 3,57%,835 Patented Mar. 16, I971 appreciated in the detailed description of a working embodiment which follows a brief description of the accompanying drawings.
DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a power operated clamp including the features of this invention and having certain parts shown in dotted and phantom outline, as will be described later.
FIG. 2 is an enlarged fragmentary plan view of the front end of the power operated clamp as seen in the plane of line 2-2 in the first drawing figure and looking in the direction of the arrows.
FIG. 3 is a front end view of the power operated clamp as seen in the plane of line 33 in FIG. 1.
FIG. 4 is a sectional view of the operating mechanism in the power operated clamp as seen in the plane of line 4-4 in FIG. 2.
FIG. 5 is similar to FIG. 4 with parts shown in a different position.
FIG. 6 is a cross-sectional view as seen in the plane of line 6-6 in FIG. 4.
FIG. 7 is a cross-sectional view as seen in the plane of the offset line 77 in FIG. 4.
DETAILED DESCRIPTION OF THE INVENTION The power operated clamping device 10 shown in the drawing figures includes a piston cylinder actuator 12 which includes a mounting head 14 and has a clamping jaw or arm member 16 pivotally attached to the mounting head as at 18. An actuating extension 20, which includes a cam slot 22, is used in swinging the clamping arm to and from the solid line clamping position shown in FIG. 1 to that of the phantom line release position 16'.
The piston cylinder actuator 12 includes a fluid pres sure chamber member 24 with closures 26 and 28 at opposite ends and suitable connections (not shown) for fluid pressure application and release. The mounting head 14 is attached to the operative end of the actuator and includes a through passage 32 for the piston rod 30 that extends from within the cylinder into the mounting head member.
The mounting head 14 is square in cross-section and includes mounting slots 34 across its top and bottom walls, as best seen in FIG. 1. Relatively offset mounting slots 36 are also provided along its opposite sidewalls, as best seen in FIG. 2. These enable a 4-way mounting without modification of the standard mounting hole pattern and eliminates the need of angle block applications with respect to the clamping face 38 of the clamping arm member 16.
The outwardly extending end of the mounting head 14 is slotted, as at 40, to receive the actuating extension 20 of the clamping arm 16 therewithin, and it is also formed to include a pair of internal roller tracks 42 and 44 which extend the full length of the mounting head on each side of the slotted access for the clamping arm and back into the through passage 32 for the piston rod 30.
The clamping arm 16 is angular in shape with a short leg 46 pivotally connected to the mounting head, as best shown in FIG. 7, by a pivot pin 48 through a close but not tight fitting bore hole 50 near its terminal end. The ends of the pivot pin extend into recesses in the sides of the mounting head, as best shown at 52 and 54, and a similar hex headed end and fastener 56 on opposite ends of the pivot pin enable the arm to be changed if and when desired.
In this latter respect, although the clamping member 16 is shown as angular, with a depending clamping arm, it may have a different shape for disposing its clamping arm and work face in another work plane. For example, a phantom view of a clamping arm 116 is shown and identified in FIG. 1 in its work holding position, and in its retracted position as at 116'.
The actuating extension 20 of the clamping arm 16 (and of clamp arm .116 as well as other variations) extends into the slotted opening 40 in the mounting head.
The cam slot 22 in the actuating extension of the arm is angular in shape and includes a dog leg opening 58 that extends radially toward the pivotal axis of the arm, but is offset ahead of the radial line, so that it is more on a tangential line relative to the pivot pin. The other leg opening 60 of the cam slot is on a tangential line on the other side of the pin and such that it is more axially aligned with the actuator cylinder, when the arm is in clamping position. The cam slot opening 60 is an angular extension of the slot leg 58 and is actually formed to include about a ramp angle relative to the axial line of the actuator stroke so that the lower edge 62 of the opening serves as an inclined plane for wedge locking purposes.
The clamping arm 16 is operated by the piston cylinder actuator through a yoke 62 fastened to the end of the piston rod and bifurcated to provide a slot opening 64 in its end receptive of the actuating extension of the clamping arm and to support a cross pin 66 that extends through the cam slot 22, as best shown in FIGS. 6 and 7. The piston rod 30 has its terminal end reduced in crosssection to provide a bearing shoulder 70 that bears against and will push the connecting part forward in its actuating stroke. A pin 72 is press fitted in the smaller extended end 68, which is received within the slot opening 64 of the connecting part, at a spaced distance from the end wall of the slot, to provide shoulder means for a lost motion retracting stroke before the connecting part is engaged and drawn back to release the clamp.
The cross-pin 66, that is in the cam slot, is provided with rollers 74 and 76 at its opposite ends, which are received and guided in the roller tracks 42 and 44 in the mounting head, and laterally disposed ears 78 and 80 near the piston rod end of the connecting part, for like guide purposes in the guideways.
The power operated clamping device is used as follows:
The mounting head 14 provides the means for fastening the unit to a supporting structure, by use of the mounting slots 34 or 36, with the clamping arm 16 positioned for work clamping and holding purposes, as in the position shown in FIG. 1. Suitable connections (not shown) are made to the piston cylinder actuator for fiuid pressure control for advancing and retracting the piston rod 30 to perform its intended function.
The operating sequence is best described with reference to the accompanying drawings from the retracting stroke of the piston rod, to open the clamp arm, and then back through its actuating stroke and subsequent release.
Referring to FIGS. 1 and 4, most particularly, as the piston rod 30 is retracted, it moves freely initially and until the shoulder pin 72 engages the end wall of the slot 64 in the yoke 62 at which time it pulls the latter back and, in turn, the roller mounted cross-pin 66 rearwardly out of the extended end of the cam slot 22. As the cross-pin 66 is retracted in the cam slot leg 60 there is a release of clamping pressure and slight opening movement of the clamping arm member.
When the cross-pin 66 enters the slot opening leg 58, the rapid action commences which swings the clamping arm up and into its full 120 open position limited by registration of the yoke 62 with the piston packing gland 63. A sleeve spacer, not shown, may be installed on the piston rod 30 between the yoke 62 and gland 63 to limit the retraction stroke if desired, as shown in FIG. 5 and in the dotted line position 16 in FIG. 1. The pin bears against the back wall of the slot opening leg 58 and moves relatively down into the slot, as it is pulled straight back, and then moves up the same slot wall surface and beyond into the extended slot leg 60, as shown in FIG. 5, where it will hold the clamping arm open in the fully retracted position.
On the forward or actuating stroke of the piston rod 30, the bearing shoulder pushes the yoke 62 forward and advances the roller mounted cross-pin 66 causing it to move relatively down and back up the cam slot leg 58 and to locate the clamping arm in work holding position. As the pin moves into the extended cam slot leg 60 it bears against the slot wall surface 62 which includes an incline, when the clamping face of the arm or jaw member is in work holding position, and it increases the clamping pressure until the actuating force is balanced by the resistant force built up due to the wedging of the pin against the inclined ramp wall of the slot. The final clamping position is reached at or just prior to the prestop position shown in FIG. 4 where further travel is limited by engagement of an arm stop surface with the mounting head at 47. This limit stop may be used to facilitate initial set up of the clamp arm and, if desired, to limit the clamping force applied to the work piece.
The 5 ramp portion 60 of the slot provides positive locking angle clamping within 3 of the final positioning of the clamping arm, and with a clamping pressure that is very high because of the gradual ramp angle.
An overtravel extension of the slot 60 with corresponding extra travel allowance in the cylinder also enables the unit to automatically compensate for wear.
In releasing the clamping arm 16 the procedure and operational sequence is as initially described. However, additional note should be made of the advantage of the free travel afforded the piston rod actuator in its lost motion connection with the cross-pin actuating part 62. No appreciable resistance is present in the piston cylinder at the start of the retracting stroke of the piston rod 30 since it does not have to initially overcome the wedge locking force applying full clamping pressure. Accordingly, the inertial resistance is low and a fast flying start is obtained in the retraction stroke providing an impact release action. As the piston rod continues its retracting stroke, the holding force on the roller mounted cross-pin 66 in the cam slot 22 is relieved, movement of the pin down the ramp surface meets minimum frictional resistance, and further momentum is built up to lift the clamping arm rapidly to its elevated position.
1. A work clamping device, comprising; a base having a plurality of mounting faces, a single fixed pivot on said base, a clamp arm member mounted on said pivot for rotation in a circular are about the pivot axis and having an actuating extension and an actuating cam slot provided therein, a linear power means mounted on said base, a reciprocable member disposed in said cam slot actuated by said power means, guide means in said base for said reciprocable member providing a reactive force cooperating with said cam slot for exerting clamping pressure on said arm, said cam slot including two obliquely disposed portions engageable by said reciprocable member adapted to provide said clamping pressure engagement in the clamping stroke and rapid opening engagement in the retracting stroke.
2. The work clamping device of claim 1, wherein: said power means comprises a piston cylinder actuator operatively connected to said reciprocable member, and said guide means extends parallel to the axis of said cylinder.
3. The work clamping device of claim 2, wherein: said clamping portion of said cam slot is formed with an acute angle inclination relative to said guide means to provide high pressure locking engagement.
4. The work clamping device of claim 3, wherein: said base is fixed to the head of said piston cylinder actuator and slotted for receiving the actuating extension of said arm member in axial alignment with said actuator, said reciprocable member comprising a roller mounted cross pin, and said guide means being receptive of the roller mounted ends of said cross pin.
5. The work clamping device of claim 1, including: a lost motion connection between said power means and reciprocable member for impact actuation of the latter in the retracting stroke.
6. A power operated clamping device comprising: a piston cylinder actuator having a mounting head provided on the operative end thereof, a single fixed pivot on said head, a work holding arm member mounted on said pivot for rotation in a circular are about the pivot axis and having an actuating extension including a cam slot disposed for piston actuation, a roller mounted cross pin operatively engaged by said actuator, extending through said cam slot and guided for reciprocal travel within said mounting head, said cam slot including two obliquely disposed portions engageable by said cross pin adapted to provide clamping pressure engagement in the clamping stroke and rapid opening engagement in the retracting stroke said clamping portion of said cam slot formed with an acute angle inclination relative to the reciprocal travel of said roller mounted cross pin to provide high pressure locking engagement.
7. The power operated clamping device of claim 6, said arm having a stop engagement with said mounting head at the extremity of the clamping stroke.
UNITED STATES PATENTS 2,845,847 8/1958 Blatt 269-32X 3,482,830 ,12/1969 Sendoykas 269 32 3,108,794 10/1963 Blatt 269233 FOREIGN PATENTS 1,080,424 8/1967 England 269-32 20 ANDREW R. JUHASZ, Primary Examiner D. D. EVENSON, Assistant Examiner US. Cl. X.R.