Work clamps
United States Patent 1191 Todd [ WORK CLAMPS [75] Inventor: Sidney Clarke Todd, Maidenhead,  
 England [73] Assignee: Pierce-A11 Manufacturing Limited,  
 &#39; Slough, England [22] Filed: Aug. 6, 1973 [21] Appl. N0.: 386,227  
 [4 Apr. 15, 1975 8/1963 Muller 279/4 9/1973 Scott 269/32 X [57] ABSTRACT A device for clamping a work piece on a machine bed has an elongate clamp body with a bore opening into the nose of the body, the nose of the bore being formed with an inclined &#39;camming face and with a clamping surface, a clamp rod movably located within the bore and having at its head an inclined or curved surface co-operating with the camming face and a clamping face disposed substantially parallel to the clamping surface of the body and a hydraulic cylinder adapted to displace the rod against the action of a return spring and produce a clamping force between the clamping surface and the clamping face.  
 4 Claims, 5 Drasr&#39;ing Figures WORK CLAMPS FIELD OF THE INVENTION This invention relates to devices for clampingwork pieces on a machine bed or the like and moreparticularly to the clamping of sheets, plates, strips or the like of metal or other material in position for piercing, drilling, notching or like operations.  
  During such operations it is frequently necessary to hold the sheet or plate against an abutment to enable the desired operation to be effected in predetermined positions relatively to the sheet or plate.  
 SUMMARY OF THE INVENTION It is an object of this invention to provide a clamping device which is efficient in operation, is readily released and rendered operative and which occupies a relatively small space on the work bed.  
  According to this invention the device comprises a clamp body adapted to be secured to a machine with one end (nose) overlapping the bed plate or like surface and having a bore opening into the nose, said bore being formed with a camming face and with a clamping surface both located in said nose, a clamp rod located within said bore and having at the nose end of the body a head which has a surface cooperating with the camming face and a clamping face disposed substantially parallel to the clamping surface of the body and means to displace the rod longitudinally of the bore so as to produce a clamping force between the clamping surface and clamping face.  
  Preferably the rod is subjected to hydraulic pressure which may be instantly applied and released.  
 BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described hereinafter by way of example with reference to a preferred embodiment thereof shown on the accompanying drawings in which:  
  FIG. I shows a longitudinal sectional elevation of the clamp body and the clamp rod thereof;  
  FIG. 2 is a plan view of the clamping device with the clamp rod removed from the body;  
  FIG. 3 is a front view of the clamp body with the clamp rod removed;  
 FIG. 4 is a side view of the clamp rod;  
 FIG. 5 is a plan view thereof.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 to 3 a clamp body of elongated form is provided at one end with spaced limbs 12 by which it may be secured in any desired manner to a machine frame (not shown) adjacent a bed plate (not shown). The body I0 is formed with a bore 14 which opens into the end 15 opposite the limbs 12 which latter end will be hereinafter termed the nose.&#34;  
  The bore 14 at the nose is formed with an inclined camming face 16 and with a flat clamping surface 18. The face 16 is slotted longitudinally as shown at 20.  
  Co-operating with the clamp body 10 is a clamp rod 22 dimensioned to fit loosely within the bore 14 of the body 10. The rod is formed at one end with a threaded portion 23 and at the other end with a part spherical head 24 which is located in the bore 14 at the nose end of the body. The lower face of the head 24 is plane to form a clamping face 28 which co-operates with the clamping surface 18 during operation. The upper curved surface 26 of the head 24 co-operates with the camming face 16 of the bore in such manner&#39;that retraction of therod 22 within the bore causes the head 24 to move downwardly and the clamping face 28 to engagea sheet, stripor the like resting on the clamping surface. 18. The &#39;curved s&#39;u&#39;rface 26 is&#39;formed with a recess 30 in which ismo&#39;unted a dowel pin 32 engaging in the slot 20 to prevent angular movement of the rod 22 during its rearward longitudinal movement.  
  The nose end ofthe&#39;body l0 is&#39;formed with a surface 34 against which thesheet or the like is pulled during the clamping action, the surface 34 thus acting as a location face for the sheet. As shown in FIGS. 1, 4 and 5 the rod 22 intermediate its ends is formed with an integral collar 36 and the rod portion adjacent the no se of the body is free of the wall of the bore to allow its depression during the clamping action. Rearwardly of the collar 36 the rod 22 is supported by a bush 38 slidable relative to the rod and forced against the collar 36 by a spring 40 having its rear end abutting against a fixed guide bush :42. g Y  
  The rod 22 passes through a hydraulic cylinder44 and its threaded portion 23 carries a slotted nut 46 engaging the thread 23 and clampable on said thread in a desired position by a screw 48 forcing the portions of the nut on opposite sides of the slot into locking engagement with the thread 23. The hydraulic cylinder 44 secured in any desired manner to the body 10 has a movable piston member 50 bearing against the front face of the nut 46 so that supply of liquid under pressure to the cylinder forces the rod rearwardly against the action of the spring 40 to produce the clamping action between the faces 18 and 28. The spring on release of the liquid pressure immediately moves the rod 22 towards the nose end of the body 10 to release the clamping action.  
  Obviously, a number of such clamping devices may be used along an edge of a sheet and may be actuated simultaneously by simultaneous increase of the hydraulic pressure in each device. Thus the clamping pressure may be instantly applied and released.  
  Preferably each of the clamping devices is provided with a set of clamp rods having heads of differing dimensions to produce effective clamping actions on sheets of different thickness.  
  Variation of the length of the longitudinal displacement of the clamp rod 22 may be produced by alteration of the position of the nut 46 on the threaded portion 23.  
 I claim:  
 1. A clamping device comprising, in combination:  
 an elongate clampbody having an axially extending bore therethrough, said body having a nose end portion provided with a clamping surface at one side of said bore which clamping surface is parallel to the axis of the bore and a camming face at the other side of said bore diametrically opposed to said clamping surface, said camming face extending axially with respect to said bore and being inclined with respect to the axis of said bore, said nose end portion also having abutment surfaces at opposite sides of said bore and contained in a plane normal to the axis of the bore and inwardly a predetermined distance from the end of said nose end portion so as to provide a datum plane for a workpiece;  
 a clamp rod reciprocable within said bore. said clamp rodhaving one endiportion dimensioned to provide clearance within said bore and terminating in a head engaged with said camming surface. saidhead having a clamp face facing but spaced from said clamping surface and said one end portion being of a length sufficien t t o permit substantial cantilever deflection thereof;  
 centering means on an intermediate portion of said clamp rod for centering said intermediate portion of the clamp rod within said bore; and  
 means for forcibly moving said &#39;c&#39;lam&#39;p rod axially of said bore to cause said head to move along said camming face and deflect said one end portion of the clamp rod in cantilever fashion from said centering means whereby said clamp face deflects to- 4 ward said clamping surface while moving axially with respect thereto so as to effect a pinching action on a workpiece while also urging it positively against said abutment surfaces.  
  2, A clamping device as defined in claim I wherein said means for forcibly moving said clamp-rod comprises&#34; a hydraulic cylinder attached to said body and a piston cooperating with said cylinder.  
  3;; A clamping device according to claim 2 which inclu&#39;gies a spring acting to return the&#39;clamp rod to its non-clamping position on release of the hydraulic pressure.  
  4, A clamping device accordingto claim 1 which iricl&#39;udes guide means preventing rotary movement of the clamp rod during its longitudinal displacement.