AU647927B2 - Press tool - Google Patents

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "PRESS TOOL" The following statement is a full description of this invention, including the best method of performing it known to the Applicant:- This invention relates to presses, that is to say tools of the kind comprising a pair of spaced apart, opposed dies and means to force at least one of the dies towards the other so as to form or modify a work piece or article placed between the dies.

Both dies may be movable relative to the tool as a whole, but usually only one is movable and the other is fixed. Frequently the die shapes are such that one die is identifiable as a female die and the other as a male die. If only one die is movable it matters not whether it be male or female. Presses according to the invention may display any combination of the foregoing possibilities.

2 The invention relates more particularly, but not exclusively, to hand held, power operated presses wherein the dies are respectively mounted on spaced apart jaws of a tool body able to be held and manipulated by hand.

Typical tools of the kind in question are riveting hand guns and clinching tools. The latter are used to affix two overlapping ductile sheets together. They operate by virtue of one die pressing or punching small, registering portions of the sheets from the plane of the sheets against an anvil surface of the other die spaced from the sheets. The displaced material is not severed, or not completely severed, from the sheets and is squeezed between the pressing or punching surface of said one die and the anvil surface of the other to such an extent that it is :o plastically strained and caused to spread laterally so that it cannot return to its former position after the pressure is removed.

15 The pressure imposed upon the work piece is considerable and thus the mechanism of the press which shifts the die or dies invariably has a high mechanical advantage. That is to say, the mechanism transforms a primary motive force or pressure of relatively low intensity and large displacement into a high force or pressure of small 20 displacement applied to the moving die. Therefore in all presses the stroke of the moving die is advantageously kept to a minimum, consistent with the required deformation of the work piece being obtained, so as to keep the displacement of the primary motive force within practicable limits.

As a result, the space between the dies, even when fully retracted, is not large, and it frequently happens that the press operator has difficulty in manipulating a work piece into position between the 3 retracted dies, or, in the case of a hand held press, has difficulty in manipulating the tool into position in relation to a fixed work piece.

An object of the present invention is to provide a press which alleviates that difficulty.

The invention consists in a press tool of the kind comprising a press body structure, a pair of co-acting dies mounted on said structure and means to force at least one die towards the other, characterised in that at least one of said dies is mounted on said structure by pivotal mounting means such that said one die may be manually swung about a pivot axis to and fro between an operating position, wherein it is in opposed alignment with the other die and the gap between the dies provides a working clearance, and an open position, wherein it is not so aligned and the gap between the dies is larger than said working clearance to facilitate the positioning of a work piece between the dies, •15 and wherein said at least one die comprises a die body having a working end and an opposite end having a part cylindrical surface, wherein a part cylindrical abutment surface on said structure conforms to and is in contact with said opposite end surface, and wherein said part

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cylindrical surfaces have a common axis of curvature coinciding with 20 said pivot axis.

o.oo By way of example, an embodiment of the above described invention is described in more detail hereinafter with reference to the accompanying drawings.

Figure 1 is a side elevation of a hand held clinching tool according to the invention.

4 Figure 2 is a front elevation of the tool of figure 1.

Figure 3 is a view of that part of the tool of figure 1 within the enclosure marked 3 in that figure drawn to a larger scale and with a cover plate removed.

Figure 4 is a sectional view taken on line 4-4 of figure 3.

Figure 5 is a view similar to figure 1 of a another hand held clinching tool embodying the invention.

The clinching tool illustrated by figures 1 to 3 comprises a body structure 5 comprising a substantial, generally C shaped, metal handpiece. 6j with two forwardly projecting opposed jaws 7 and 8 respectively.

The central portion of the hand-piece 6 is sized so that it may be grasped and held in one hand.

ooooQ The jaw 7 houses a hydraulic actuating cylinder 9, or is internally machined to function as such a cylinder, housing an actuating piston S 15 (not shown), on which a movable, male die 10 is mounted.

The hand-piece 6 is connected by a pliable, high pressure, hydraulic fluid hose 11 and a pliable air hose (not shown) to a 4 conventional hydro-pneumatic intensifier, Such an intensifier may S.comprise a large diameter air cylinder in axial alignment with a much

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o 20 smaller diameter hydraulic cylinder. Pistons in the respective cylinders are joined by a piston rod extending through appropriate seals in an end wall common to both cylinders (frequently the "piston" in the hydraulic cylinder is no more than an end portion of such a rod). The admission of compressed air at a relatively low pressure (say 80 psi or approximately 550 kPa) to the pneumatic cylinder may be controlled by a spring biased, air controlled, pilot valve. The arrangement is such that each time one side of the pIlot valve is vented to atmosphere (by means of a bleed valve within the hand-piece 6 operated by a push button 12 releasing air from the said air hose extending to the intensifier), the pilot valve moves to admit compressed air to the intensifier's air cylinder.

The air cylinder's piston then moves to pump a charge of hydraulic fluid at a high pressure (say 4000 psi or ipproximately 27600 kPa) from the intensifier's hydraulic cylinder through the hose 11 and a drilling within the hand-piece 6 into the hydraulic actuating cylinder 9 within the jaw 7.

This, in turn, causes the actuating piston within that cylinder and the die 10 thereon to move downwardly (as seen in figure 1) through a predetermined distance. As soon as the bleed valve is allowed to close, the pilot valve of the intensifier moves to vent the intensifier's pneumatic cylinder. This enables a leaf spring 13 to return the actuating piston and the die 10. This, of course, pumps the charge of hydraulic fluid back to the intensifier in readiness for the next operation.

In another similar embodiment, the intensifier is housed within a .tubular housing extending directly from the hand piece and adapted to S 20 function as an extended handle for the tool.

It must be emphasised that the intensifier and control arrangements described above are well known in the art and are not essential to the invention. In other embodiments the downwards working stroke of the die 10 or its counterpart may be effected by any o:i ~25 conventional means including manually operable mechanical devices, and directly acting pneumatic, hydraulic or electrical actuators.

6 The die 10 is essentially a hardened steel tongue of rectangular section. Its bottom or working end face is chamfered to present a horizontal centre portion 14 and inclined flanks 15. It cooperates with a female die 16.

As may be best seen in figures 3 and 4, the die 16 comprises a main die body 17 and two shear plates 18 resting on shoulders formed on the die body 17. The two shear plates 18 are prevented from sliding off the ends of those shoulders by a pin 19 extending through the body and the shear plates. The clearance holes for the pin 19 in the shear plates 18 have diameters which are appreciably larger than that of the pin 19, so that the pin does not prevent the shear plates 18 from sitting flatly upon the body shoulders. Thus downwards forces applied to the shear plates 18 during a clinching operation are always transferred directly to the body 17 without being imposed on the pin 19. The shear plates 18 are further secured by a stretched, elastomeric ring encircling the plates and functioning as a garter spring. The ring 20 may be partly ensconced in grooves formed in the edge faces of the shear plates 18.

°The die 10 is a neat fit between the shear plates 18 when they are positioned as shown in figure 4. Thus, assuming two metal sheets of appropriate thickness are positioned one on top of the other between the dies 10 and 16, operation of the illustrated tool initially causes the die 10 and the plates 18 to function as shear blades producing two short, parallel slits in those sheets. The horizontal centre portion 14 of the end face of the die 10 pushes the centre part of the sheet material between those slits from the plane of the sheets into contact with an anvil surface 21 of the die 16.

Continued movement of the die 10 squeezes that centre part of the displaced sheet material against the anvil surface 21 and causes it to spread laterally, such spreading being accommodated by virtue of the shear plates 18 moving apart and further stretching the ring 20, so that the edges of the spread material then underlie the metal sheets. That spread centre part of the displaced material is still connected to the sheets as a whole by the end parts of the displaced material, which conform with the flanks 15 of the die 10, hence the two sheets are positively clinched together.

The total movement of the die 10 is quite small. Therefore it is necessary for the working clearance between the two dies at the start of a clinching operation to be only a little more than the combined thicknesses of the sheet materials being clinched.

Insofar as it is described above the illustrated clinching tool may 15 be regarded as conventional, but in a conventional tool the die 16 would i: be firmly and fixedly held in its operating position as shown in full line in figure 1 and in figures 2, 3 and 4, whereas, in accordance with the invention, die 16 may be manually swung to an open position as shown S"in broken outline in figure 1.

To that end the tip of the jaw 8 has an open fronted, parallel sided recess in it, in which the lower part of the body 17 of the die 16 is 0: ensconced. The rear surface of the recess is profiled to present a flat substantially vertical end part 22, a flat substantially horizontal end part 23 and a part cylindrical intermediate part 24. The end of the die body 17 is correspondingly profiled. It held in the recess by a pivot pin 25 which is substantially co-axial with the cylindrical parts of tne recess and die body. Thus the die 16 may be swung from one position 8 to the other. In the operating position the die body abuts the surface portion 22 of the recess, whereas in the open position it abuts portion 23.

The pin 25 is a loose fit in the die body 17 so that downward loads on the die 16 are transferred directly to the jaw 8 without being imposed on the pin For preference the die 16 is biased into each of its two positions.

This may be effected by a tension spring 26 preferably housed within a recess in one side of the jaw 8. The spring 26 extends from an anchorage pin 27 fixed in the jaw 8 to an anchorage pin 28 fixed in the die body 17 and extending through an arcuate slot in the floor of the recess housing the spring 26. The anchorage pins are positioned such that the line of action of the spring 26 lies to one side of the axis of rotation of the die 16 when the die is in the operating position and to the 0:-"0i 15 opposite side of that axis when the die is in the open position.

Therefore the die is stable in both positions.

For preference the recess housing the spring 26 is closed by a protective cover plate 29, The tool illustrated by figure 5 is functionally equivalent to that of to 20 figures 1 to 4, It differs significantly only in the shape and configuration of its body structure and its triggering arrangements. Thus the body structure includes a comfortably shaped hand grip 30 overlying a slot 31 ooo*° providing a clearance passage for the operator's fingers, Also the push button of the earlier described embodiment Is replaced by a springloaded trigger 32, which, when squeezed, operates the bleed valve 33, It will be appreciated that there may be many variations in the design of press tools, and in the dies thereof, depending on the task performed by the tool and other design imperatives, but all such come within the ambit of the invention provided at least one of the tool's coacting dies is manually pivotable from an operating position to an open position providing greater clearance between the dies.

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Claims (4)

1. A press tool of the kind comprising a press body structure, a pair of co-acting dies mounted on said structure and means to force at least one die towards the other, characterised in that at least one of said dies is mounted on said structure by pivotal mounting means such that said one die may be manually swung about a pivot axis to and fro between an operating position, wherein it is in opposed alignment with the other die and the gap between the dies provides a working clearance, and an open position, wherein it is not so aligned and t'ie gap between the dies is larger than said working clearance to facilitate the positioning of a work piece between the dies, and wherein said at least one die comprises a die body having a working end and an opposite end having a part cylindrical surface, wherein a part cylindrical abutment surface on said structure conforms to and is in contact with 15 said opposite end surface, and wherein sa'id part cylindrical surfaces i have a common axis of curvature coinciding with said pivot as.

S A pross tool according to claim 1 further comprising a loose pivot pin for said at least one die with its longitudinal axis generally coinciding with said pivot axis. 20

3. A press tool according to any one of the preceding claims wherein said operating and open positions are determined by abutment surfaces on said structure respectively contacted by said at least one die body when in the respective pos tions.

4. A press tool according to claim 3 further comprising over- centre spring means tending to hold said at least one die in whichever of said positions it is situated, A press tool substantially as described herein with reference to figures 1, 2, 3, and 4, or with reference to figure Applicant JOHN LYSAGHT (AUSTRALIA) LIMITED Date 01 June 1992 Attorney ROBEPIT G. SHELSTON F.I.P.A.A. of CARTER SMITH BEADLE 40:0 *to$ A ABSTRACT A manually held press tool comprises a C-shaped press body structure 5, a pair of co-acting dies 10 and 16 mounted on said structure and pneumatically controlled hydraulically powered means to force at least one die towards the other. The tool is characterised in thai one of said dies is mounted on said structure by pivotal mounting means such that said one die may be manually swung about a pivot axis to and fro between an operating position, wherein it is in opposed alignment with the other die and the gap between the dies provides a working clearance, and an open position, wherein it is not so aligned and the gap between the dies is larger than said working clearance to -facilitate the positioning of a work piece between the dies. The pivot means comprise mating part cylindrical surfaces on said one die and I body structure, by which die pressure is transmitted to the body structure, and a loose pivot pin 25 to keep said one die in situ. An over centre spring 26 biases said one die into the respective positions. Figure 3. a*o