A HAND OPERATED RIVETING TOOL

Abstract: The riveting tool has two pin drawing arms (l0 and ll) and a pin clamping arm (l2). Springs (20, 28) act between the arms to urge them apart. When the arms (ll) are drawn together, the arm (l2) firstly moves towards the arm (ll) because spring (28) is weaker than spring (20). A cam formation (29) on the arm (l2) bears against a cam follower (26) on a slider (22) and the slider moves to clamp a clinching pin between clamping members (24 and 25). The arm (ll) then moves towards the arm (l0) to open elongate jaws (l7, l8) and draw the clinching pin at least partly through a rivet.

Description: This invention relates to a hand operated riveting tool particularly for use with rivets of the type commonly known as "pop" rivets, i.e. hollow rivets requiring work access from one side only for placing and clinching. These rivets comprise a headed tube through which a headed mandrel or pin is drawn to clinch the rivet by upsetting the shank end (i.e. the non-headed end) on the inaccessible side of the rivet. Hand operated riveting tools are known for clinching rivets of this type but generally these known tools use a collet mechanism to grip the mandrel or pin and cannot be used in some confined spaces. In particular they are not suitable for use in certain branches of orthopaedic surgery e.g. in setting jaw fractures by attaching plates to the fractured parts. According to the invention there is provided a hand operated riveting tool comprising first and second pin drawing arms and a pin clamping arm movable relative to one another in a common plane with the second pin drawing arm interposed between the first pin drawing arm and the pin clamping arm, the first and second pin drawing arms being pivotably connected together about a pivot axis and having on one side of the pivot axis respective jaws which are urged together by first spring means and which can be moved apart against the urging force of the first spring means by moving the first and second pin drawing arms on the other side of the pivot axis together, the first pin drawing arm having therein a through hole dimensioned so as to allow a clinching pin but not a rivet to be drawn therethrough, and there being two mutually co-operating clamps for clamping therebetween a clinching pin when the clamping arm is moved towards the second pin drawing arm against the urging force of second spring means, the first and second spring means being so arranged that when in use an operator takes hold of the tool and moves the pin clamping arm towards the first pin drawing arm the first movement is that of the pin clamping arm towards the second pin drawing arm to clamp a clinching pin between the clamps and this is followed by movement of the second pin drawing arm relative to the first pin drawing arm to open the aforesaid jaws and draw the clinching pin at least partly through a rivet. Preferred and/or optional features of the invention are set forth in claims 2-l3 inclusive. The invention will now be more particularly described, by way of example, with reference to the accompanying drawing which is an exploded view of one embodiment of a hand operated riveting tool according to the invention. Referring to the drawing, the hand operated riveting tool shown therein comprises two pin drawing arms l0 and ll and a pin clamping arm l2. The pin drawing arms l0 and ll are pivotably connected together by a pivot pin l3 which extends through aligned apertures l4 and l5 in the two arms l0 and ll, respectively, and which has a threaded end engaged by a nut l6. The arms l0 and ll have respective elongate jaws l7 and l8 extending to one side of the pivot pin l3. The jaw l7 is of channel section and has a through hole l8 therein. A small cup-shaped member l9 is attached to the base of the jaw l7 and a through hole (not shown) in the bottom of the cup-shaped member l9 is aligned with the through hole l8. A spring clip (not shown) has opposed ends which extend into the cup-shaped member l9 to make frictional contact with diametrically opposed portions of a clinching pin (not shown) to hold the pin and prevent it from slipping out of the tool. The jaw l8 is disposed within the jaw l7 and is urged into contact with the base of the channel section of the jaw l7 by a bowed leaf spring 20 which is held captive in the arm l0 and which urges the arms l0 and ll apart. The jaw l8 is also of channel section and a slider 22 is mounted in the jaw l8 for slidable movement in a direction parallel to the longitudinal extent of the jaw l8. The slider 22 has an elongate slot 23 through which the pivot pin l3 extends in order to hold the slider 22 captive relative to the jaw l8 and yet allow the aforesaid movement of the slider 22. The slider 22 also has a clamping member 24 which co-operates with a clamping member 25, mounted in the jaw l8, in a manner to be described hereinafter and a cam follower 26. The clamping arm l2 is pivotably connected to the arm ll by a pin 27 and is urged apart from the arm ll by a bowed leaf spring 28 which is held captive in the arm ll. The clamping arm l2 also has an integral cam formation 29 which co-operates with the cam follower 26 when the arm l2 is pivoted against the urging force of the spring 28 to move the slider 22 and hence the clamping member 24 towards the clamping member 25. The base of the channel section of the jaw l8 has an opening (not shown) which is aligned with the clamping members 24 and 25 to allow a clinching pin to enter between the clamping members and the arms l0 and ll have aligned openings (not shown) through which the cam formation 29 and cam follower 26 project. Projections 30 on opposite sides of the cam formation 29 are disposed on that part of the cam formation 29 which is interposed between the two arms l0 and ll and these projections 30 serve as stops to limit the outward pivotal movement of the arm l2 relative to the arm ll. A latch member 3l having an inturned flange 32 is provided on the arm l0 and co-operates in a manner to be described hereinafter with a holding member 33 provided on the arm l2. The spring 20 is stronger than the spring 28 for a purpose which will become apparent and the tool is conveniently of stainless steel with the exception of the clamping members which are conveniently of tungsten carbide. In operation a clinching pin is passed through a rivet from the side thereof inaccessible to the tool, until the head of the pin makes contact with the shank end of the rivet. The assembled rivet and clinching pin are then located in appropriately drilled or otherwise formed holes in two or more parts to be fastened together The accessible end of the pin is then introduced through the hole in the cup-shaped member and the hole l8 and between the clamping members 24 and 25. An operator then takes hold of the tool and moves the arm l2 towards the arm l0. As a result of the differential force applied by the two springs 20 and 28, the arm l2 first moves towards the arm ll while the latter retains its position relative to the arm l0. The cam formation 29 thus acts on the cam follower 26 to move the slider 22 and clamp the clinching pin between clamping members 24 and 25. The arm ll then starts to move towards the arm l0 while additional pressure is applied to the clamping members 24 and 25 and the clinching pin is drawn at least partly through the rivet. As the arm l2 approaches the arm l0 the holding member 33 slides over the latch member 3l urging the flange 32 of the latter into engagement with the side of the arm ll. During the final stage of movement of the three arms the holding member 33 urges the flange 32 of the latch member 3l into latching engagement with the upper edge of the arm ll as viewed in the accompanying drawings. When the operator releases the pressure applied to the arms l0, ll and l2 the arms l0 and ll remain latched together during the initial return movement of the arm l2 and until such time as the holding member 33 separates from the latch member 3l. The jaws l7 and l8 then snap open under the influence of the spring 20, but this does not happen until the clamping members 24 and 25 have released their grip on the clinching pin. If the clinching pin is not drawn through the rivet in one operation of the riveting tool, the operation can be repeated in order to ratchet the pin through the rivet. The tool described above can be used in confined spaces not previously accessible to known riveting tools. In particular it can be used to attach metal plates to parts of a fractured jaw bone. The above embodiment could be modified in several ways without departing from the scope of the invention. For instance, the bowed leaf springs could be replaced by torsion springs. Alternatively the leaf springs need not be bowed. In this latter case, arm 11 could be shortened significantly if the leaf springs were to be attached to arms 10 and 12, respectively, rather than be supported by arms 10 and 11. One end of each spring would be attached to the arm 10, 12 and the other end of each spring would bear against the shortened arm 11. Moreover, instead of pivotably connecting the clamping arm 12 to the pin drawing arm 11, the arm 12 could be connected to the arm 11 by a link (which is shown in broken lines in the drawing) and the end of the arm 12 adjacent to the slider 22 could be guided relative to the arm 11. This would make it possible to do away with the cam formation 29 on the arm 11. The slider 22 could even be an integral part of arm 12 and when using a link between the arms 11 and 12 the link could be arranged so that the clamp movable by the arm 12 is pulled towards a clamp on the arm 11.

Claims: 1. A hand operated riveting tool comprising first and second pin drawing arms and a pin clamping arm movable relative to one another in a common plane with the second pin drawing arm interposed between the first pin drawing arm and the pin clamping arm, the first and second pin drawing arms being pivotably connected together about a pivot axis and having on one side of the pivot axis respective jaws which are urged together by first spring means and which can be moved apart against the urging force of the first spring means by moving the first and second pin drawing arms on the other side of the pivot axis together, the first pin drawing arm having therein a through hole dimensioned so as to allow a clinching pin but not a rivet to be drawn therethrough, and there being two mutually co-operating clamps for clamping therebetween a clinching pin when the clamping arm is moved towards the second pin drawing arm against the urging force of second spring means, the first and second spring means being so arranged that when in use an operator takes hold of the tool and moves the pin clamping arm towards the first pin drawing arm the first movement is that of the pin clamping arm towards the second pin drawing arm to clamp a clinching pin between the clamps and this is followed by movement of the second pin drawing arm relative to the first pin drawing arm to open the aforesaid jaws and draw the clinching pin at least partly through a rivet. 2. The riveting tool of claim l, further comprising means for releasably holding the jaws of the pin drawing arms apart when an operator releases the pressure applied to the arms and until such time as the clamping arm has moved far enough away from the second pin drawing arm to release the grip applied by the clamps to the clinching pin. 3. The riveting tool of claim 2, wherein the releasable holding means comprise a latch member which is provided on the first pin drawing arm and which is engagable with the second pin drawing arm, and a holding member which is provided on the pin clamping arm and which co-operates with the latch member to cause the latter to engage the second pin drawing arm when the three arms are moved together and which holds the latch member in engagement with the second pin drawing arm during the initial stage of movement apart of the pin clamping arm and the second pin drawing arm. 4. The riveting tool of anyone of the preceding claims, further comprising a slider which is held captive with respect to the second pin drawing arm and which is movable along the jaw of the second pin drawing arm when the clamping arm is moved towards the second pin drawing arm, the mutually co-operating clamps being on the slider and the second pin drawing arm. 5. The riveting tool of claim 4, wherein the first and second pin drawing arms are pivotable relative to one another about a pivot pin which extends through an elongate slot in the slider. 6. The riveting tool of claim 4 or claim 5, wherein the pin clamping arm is pivoted to the second pin drawing arm and acts on the slider through a cam formation. 7. The riveting tool of anyone of claim 4 or claim 5, wherein the pin clamping arm is connected to the second pin drawing arm by a link in such a way that as the pin clamping arm and the second pin drawing arm are moved together one end of the clamping arm slides along the second pin drawing arm to move the slider therewith. 8. The riveting tool of anyone of the preceding claims, wherein the first and second spring means are supported by the first and second pin drawing arms, respectively, and wherein the first spring means is stronger than the second spring means. 9. The riveting tool of claim 8, wherein the first and second spring means are bowed leaf springs. l0. The riveting tool of claim 8, wherein the first and second spring means are torsion springs. 11. The riveting tool of anyone of the preceding claims, wherein the aforesaid jaws are elongate. 12. The riveting tool of anyone of the preceding claims, wherein the first pin drawing arm is provided with means for making frictional contact with a clinching pin inserted in said through hole. 13. The riveting tool of claim l2, wherein the contact making means comprises a spring clip.

Inventors: CLARK, ROBERT NIGEL WAKE
Applicants: CLARK, ROBERT NIGEL WAKE
Application year: 1987
Main classification: B21J15
IPC codes: B21J15