GB2293127A - Apparatus for applying a compressive force to sheet material - Google Patents

Abstract

A hand-held clinching device is used for joining together two sheets (100) of material such as metal. The device has a die (2) onto which the sheets are urged by a punch (1) carried on 8 piston (4). Before punching, the sheets (100) are clamped in position on the die (2) by clamping means (66), which are at least partially accommodated in the piston (4) thereby enabling the device to be of a relatively compact construction. Such a construction may be used on other devices which apply compressive forces to sheet material, and which require clamping means in addition to a punch. <IMAGE>

Description

Title: Anoaratus for Aoplvino a Compressive Force to Sheet Material Field of the invention This invention relates to apparatus for applying a compressive force to sheet material.

The invention is particularly applicable to apparatus for fastening two or more pieces of sheet metal together by a process of clinching, but also relates to apparatus for performing other operations, such as piercing, cropping, crimping, bending, swaging and embossing.

Background to the invention The process of fastening pieces of ductile sheet material, particularlv metals. together by clinching is becoming increasingly popular since it can provide an impervious and fatigue resistant joint and does not require the use of additional fasteners. such as bolts or rivets.

Additionally. the process of clinching can be used on galvanised metals without damaging the protective coating of the metals. unlike spot welding, and can also be used to join sheets ()f dissimilar materials. such as aluminium and steel. which cannot be spot welded together.

One cxample ot a svstem for joining sheet metals by clinching is that identified by the Trade Mark TOG-L-LOC. In this system the clinching can be performed by a tool having a punch driven by a hydraulic ram which is operable to push the punch towards and into an opposed expandable die. The sheets of material to be joined are positioned between the punch and the die. and the aforesaid movement of the punch causes the two sheets to he deformed in such a way that they are mechanically locked together.

The device includes a clamping assembly, which holds the sheets of material in position relative to each other during punching and which also facilitates the withdrawal of the punch from the sheets. Another function of the assembly is the removal of scraps of material from the punch after a punching operation.

Such devices tend to be cumbersome, and unsuitable for joining sheet material, for example in a narrow flange. which cannot extend sufficiently far into the device to reach the space between the punch and the die.

Summarv of the invention According to the invention, there is provided apparatus for applying a compressive force to sheet material, the apparatus comprising a punch. a die, a piston on which the punch is amounted, the piston being movable SO as to move the punch towards and away trom the die. clamping means movabiy mounted relative to the punch and operable to clamp the sheet material in position between the die and the punch wherein the clamping means is at least partially accommodated in a cavity in the piston.

Since the clamping, means is partially accommodated in the piston, the assembly of the punch, the piston and the clamping means is relatively compact.

Preferably the punch and the clamping means are eccentrically positioned on the piston so as to facilitate access ot the sheet material to the space between the punch and the die.

The punch and the die are thus situated closer to an edge ot the apparatus than would be the case f those components were positioned on the centre line of the piston.

Accordingly it for example. the sheet materials to be joined together were in the form of a flange. the apparatus could be used on flanges of smaller width than would be the case with a centrally arranged punch and dive.

Preferably. the clamping means comprises a sleeve through which. in use, the punch is extended in oruer to apply said compressive force. and biasing means for acting between the sleeve and the cavity so as to urge the sleeve towards the die, the arrangement being such that the sleeve, in use, urges the sheets against the die.

The clamping means preferably also includes a hollow housing member for the sleeve and the biasing means, the housing member and the cavity having cooperating screw threaded portions by which the housing member is removably attached to the piston.

Thus. the housing is also partially accommodated in the cavity.

In a preferred embodiment. the punch and the die are so configured that the device is operable to fasten together pieces of sheet material bv a process of clinching, preferably in accordance with the TOG-L-LOC (Trade Mark) sheet metal joining system.

Conveniently. the apparatus comprises a hand held device, and the piston is preferably hydraulically actuated.

The invention also lies in a device for applying a compressive force on sheet material, the device comprising a dic. a punch mounted on a piston which is moveable to move the punch upwards and away from the die wherein the punch is eccentrically positioned on the piston.

Brief description of the drawings The invention will now be described. by way of example only. with reference to the accompanving drawings. which show a hand held clinching device having extendable punch ;rnd a dive. and in which Figure 1 is a sectional side view of part of the device. when the punch is in its retracted position:: Figure 2 is an exploded sectional side view of the device. and Figure 3 is a view corresponding to Figure 1. showing the device when the punch is in its extended position Figure 4 is an elevational view of the front of the device and Figure 5 is a view of the rear of the device, part of which is shown in section.

Detailed description The device shown n in the drawings is orterabie to fasten together two pieces of sheet metal in accordance with the TOG-L-LOC system.

With reference to Figure 1, the device, which is hydraulically operated, includes a cylindrical punch 1 mounted. in opposing relationship to an annular die an annular 2, on a cylindrical piston 4 which is slidable within a cylinder 6 provided in a body 8 of the device. The device includes a handle 34 (Figures S and 5) which. for the sake of clarity, has been omitted from Figures l to The body 8 of the device is attached at one end to an end cap 10 by means of screws 12.

14. 16 and 18 which pass through respective registering bores (not shown) in the cap 10 and body 8.

The cap 1() incudes the central recess 9(! which communicales with a vertical bore 22 in the end region of the cap 1(). One end of the bore 22 is sealed by a ball plug 24. whilst the other end of the bore 22 leads onto a connecting bore 26 wich, in turn.

communicates with a passage 'S in the bodv 8 The passage 28 inc!udes a tapped vertical end portion 30.

The handle 34 is held ir position on the body 8 by means ot a pair Of screws (not shown) which extend inrough vertical bo@es 36 and 38 in the handle. The bores 36 and 38 are countersunk at their lower ends. as indicated by reference numbers 40 and 42. to decommodate the heads of the serews.

The uppcr region of the handle 34 includes a cavity 32 which accommodates an electrical contact assembly. (not shown) connected to a push button 44 projecting from the front of the handle. The handle also includes a vertical passage 37 which is situated behind the cavity 32, is in registry with the portion 30 and accommodates a hydraulic hose (not shown) which is screwed onto the portion 30. The hydraulic hose connects the passage 28 to an external hydraulic pump (not shown).

The contact assembly in the cavity 32 is also connected to the external pump, by a control cable (not shown). In use, when the operator presses the button 44, a signal is sent to the hydraulic pump. causing it to force hydraulic fluid along the conduit defined by the passage 28, and bores 26 and 22, and into the recess 20. When the operator releases the button 44, the pump allows hydraulic fluid to travel along the conduit in the opposite direction. and hence allows the fluid to be expelled from the recess 20.

With reference to Figure 2, the piston 4 includes a cavity 50 which has a cylindrical inboard portion 52 leading onto a screw threaded cylindrical outboard portion 54 of greater diameter than the portion 52. The piston 4 includes a radial bore 55 which extends from the exterior of the piston to the inboard portion 53 of the cavity 50.

The inboard portion 52 accommodates a punch holder 56 comprising a cylindrical cup which includes a radial through-bore 58. The external diameter of the holder 56 corresponds to the diameter of the portion 52 so that the punch holder 56 is a tight fit within the cavity 50, and the internal diameter of the holder 56 corresponds to the diameter of the body of the punch 1. part of which is inserted into the holder 56.The bores 55 and 5X are in registry with each other. and the latter includes a screw thread to enable the punch 1 t() be retained in the holder 56 by means of a grub screw 6() which extends through the bore 5;3.

The body portion 8 also o has a slot 53 which is in registry with the bores 55 and 58 and which therefore enables access to be gained to the grub screw 6() when the punch 1 is to be replaced.

The punch holder 56 has an annular end surface 62 which acts as a shoulder for a compression spring 64. The compression spring 64 fits over the punch 1 and bears against an annular tlange 65 at one end of a cylindrical sleeve which constitutes a stripper tip 66. The end of the tip 66 opposite the flange 65 includes an axial aperture 68 through which, in use, the outboard end of the punch l extends.

The holder 56 the punch 1 the spring 61 and the tip 66 are held in position by a housing in the form of a stripper can 70 which includes an externally screw threaded portion by which it is attached to the portion 54 of the cavity 50. The can 7(1 also includes a central axial aperture 72 through which the punch 1 and the tip 66 extend.

The die 2 comprises a number of resiliently moveable blades which define a central recess in registry with the outboard end of the punch 1. The die 2 is attached to an end piece in the form of an anvil cap 72 of the device by means of a screw 74 which passes through an aperture 73 in the cap 72 and into a screw-threaded passage 76 in the end of the die 2.

The anvil cap 72 is held in position on the hody portion 8 by means of screws 76, 78. 80 and X2 which extend through respective passages (not shown) in the anvil cap 72 and into registering serwe-theraded passages (not shown) in the body portion 8.

The anvil cap 72 includes a cylindrical recess 84 which accommodates one end region of a compression spring 86. which in turn, extends through a cylindrical passage 88 in the body 8. and engages an end face 90 of the piston 4.

The piston 6 and the end cap 10 have respective annular grooves 92 and 94 for tecommodating respective hydraulic seals 96 and 98.

With the device in the configuration shown in Figure 1. substantially no hydraulic fluid pressure is suppiied by the source to the recess '(), and as a result the spring 86 acting between the anvil cap 72 and the piston 4. urges the latter against the cap 10. The spring he also urges the flange h5 of inc stripper tip 66 against the stripper can 7(). and the punch 1 docs not protrude beyond the end of the tip 66.

When the device is to be used, the pieces of sheet metal (100 in Figure 3) are positioned in the space between the die 2 and the assembly of the punch 1 and the stripper tip 66.

The operator then presses the button 44 which causes hydraulic tluid to be forced into the chamber 20 (through passage 28 and bores 26 and 22) and thus to move the piston 4 towards the anvil cap 72. As this happens, the tip 66 makes contact with the sheets 100 which are accordingly clamped between the tip 66 and the die 2. Continued movement of the piston 1 towards the cap 72 causes the punch 1 to continue to move towards the die 2 so that the end of the punch 1 moves beyond the tip 66 and into the aperture between the die blades, thus also forcing the sheets into the aperture so as to deform the sheets and create a joint. As this happens, the holder 56 is urged towards the flange 65 on the tip 66 against the action of the spring 64.

When the operator releases the button 44, the consequent release of pressure of hydraulic fluid acting on the piston 1 enables the spring 86 to move the piston 4 back into the position shown in Figure 1. As this happens, the spring 64 pushes the tip 66 past the c,uthoard end of the punch 1. thus retracting the punch from the cavity lormed in the sheets and removing any scraps of material from the punch 1.

Claims (8)

1. Apparatus for applying a compressive force to sheet material, the apparatus comprising a punch, a die, a piston on which the punch is mounted, the piston being movable so as to move the punch towards and away from the die clamping means movably mounted relative to the punch and operable to clamp the sheet material in position between the die and the punch wherein the clamping means is at least partially accommodated in a cavity in the piston.
2. 2. Apparatus according to claim 1. in which the punch and the ciamping means are eccentrically positioned on the piston so as to facilitate access of the sheet material to the space between the punch and the die.
3. Apparatus. according to ciaim 1 or claim 2, in which the clamping means comprises a sleeve through which. in use. the punch is extended in order to apply said compressive force and biasing means for acting between the sleeve and the cavity so as to urge the sleeve towards the die. the arrangement being such that the sleeve. in use. clamps the sheets agains. the die.
4. 4. Apparatus according to claim 3. in which the clamping means also includes a hollow housing member for the sleeve and the biasing means. the housing member and the cavity having cooperatino screw threaded portions bv means of which the housing member is removably attacked to the piston.
5. Apparatus according to claim m in which th housing is also partially accommodated in the cavity.
6. 6. Apparatus according to am; of the preceding claims, in which the punch and die are so cni'igured that the apparatus is operable to fasten together pieces of sheet material bv a pr(lecss oi' clinching.
7. Apparatus according to an! of the preceding claims, in which the apparatus comprises a hand held device.
8. 8. Apparatus according to any of the preceding claims, in which the piston is hydraulically actuated.

   Apparatus substantially as described herein, with reference to, and as illustrated in, the accompanying drawings.