GB1603232A - Locking joint machine - Google Patents

Description

(54) LOCKING JOINT MACHINE (71) I, OTTO P. HAFNER, a citizen of the United States of America, of 1321 Paddock Way, Cherry Hill, New Jersey 08034, United States of America, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed to be particularly described in and by the following statement: The present invention relates to machines for operating on workpieces comprising at least two layers to be joined, from opposite sides of the workpiece to form a locking joint therein.

The present application is related to copending British Patent No. 1,603,231, Application Serial No. 2682/78, filed January 23, 1978, (Patent Specification No: ) and is directed to a further modification and improvement of the machine described in that prior application.

In particular, the present invention is directed to a new and improved machine for making locking joints in a workpiece comprising juxtaposed layers of material, such as sheet metal, plastic sheeting or other material having somewhat ductile properties, and is particularly useful under conditions when physical access to the materials to be joined is somewhat restricted.

As explained in my above-identified prior patent application, the locking joints in question are known, per se. They are disclosed, for example, in the following U.S. Patents: Patent No. Issue Date 3,726,000 April 10, 1973 3,862,485 January 28, 1975 3,885,299 May 27, 1975 3,924,378 December 9, 1975 3,934,327 January 27, 1976 3,981,064 September 21, 1976 As taught in those prior patents, these joints are formed by partially piercing adjacent portions of the several juxtaposed layers, and then flattening or swaging the pierced portions, or at least the pierced portion of the layer or layers closest to the un- pierced portion of the material layers. These swaged portions then tend to overlap the unpierced material and lock the joint securely against separation.

A variety of fastening machines have been devised for carrying out the operations involved in making such joints, as exemplified by the patents referenced above. These machines basically function as follows: the layers to be joined are placed between two jaws of the machine. One jaw holds a piercing die, the other a piercing punch. This die and punch then cooperate to perform the partial piercing operation, displacing the pierced layers of material far enough so that they protrude to at least some degree beyond the portions of material which have remained unpierced. The jaw which holds the die also holds a swaging or flattening punch. Following the piercing, this swaging punch cooperates with the piercing punch to flatten the pierced (displaced) material portion. During this flattening, or at least during some part of the flattening stroke, the die is preferably used to confine laterally some or all of that displaced material layer which is closest to the swaging punch, while leaving unconfined that displaced material layer which is closest to the piercing punch. As a result, the swaging, or flattening effect takes place selectively in the unconfined layer closest to the piercing punch.

Various aspects of this technique were susceptible of further improvements. These included simplification of the overall mechanism, increased flexibility of adaptation to different characteristics of the materials to be joined, improved suitability for the making of multiple joints, and so forth.

Improvements in one or more of these respects are provided by the machines which are the subject of my above-identified prior Application Serial No. 1,603,231 (2682/78).

These improvements particularly feature the uses of inclined plane camming and toggle action.

A remaining matter not specifically addressed in this prior art is that of forming such joints in hard-to-reach locations.

For example, in the manufacture of automobile hoods, or trunk lids it is desirable to use such joints as being discussed to fasten an inner liner to the outer metal layer of the hood or trunk lid.

The outer perimeter of such a hood or trunk lid structure is typically formed with a downturned lip, extending at right angles to the general plane of the structure. In addition, there is typically a second, narrower lip at right angles to the first. The perimeter therefore is in the general shape of a U, open toward the interior of the structure.

Moreover, these lips are usually quite close to the inward bulge in the inner liner which, with the lips, defines a rather deep, but narrower channel, again extending along the perimeter of the structure.

The location at which the joints between inner liner an outer layer must be made is precisely in the bottom of the U. The machine for making these joints must therefore be capable of "reaching" into this hardto-reach location, and then also perform the multiple, co-ordinated movements which are necessary to produce the desire joints, with the high precision and force which are also required.

Attempts to accomplish all this have not been altogether successful. A proposed method comprises first moving a fastening machine of this general type into a position in which the rim of the structure was within the open "jaw" of the machine with the die and flattening punch on one side of the rim and the piercing punch on the other side, but with all these tool elements spaced from that rim. The whole fastening machine then had to be shifted until the die came to bear upon the materials to be joined. Only then could the joint-producing relative movements of the tool elements be carried out.

This gave rise to very undesirable machine characteristics. In particular the need to move the whole heavy and bulky fastening machine before each joint formation introduced a whole additional order of complexity.

The present invention provides a machine for operating on a workpiece comprising at least two layers to be joined, from opposite sides of the workpiece to form a locking joint therein, the machine being adapted to effect relative displacements of tool elements comprising a piercing punch, a piercing die and a flattening punch, both for locating the tool elements in an operating position in relation to a workpiece and for operating on the workpiece, the machine comprising; a machine frame adapted to remain stationary during locating and operating displacements of the tool elements; a respective means for holding each of the tool elements, each holding means being reciprocably mounted to the frame; positioning means mounted to the frame and comprising reciprocably movable means for changing the relative positions of the holding means; and toggle linkage means mounted to the frame and adapted to be reciprocably actuated so that the linkage passes through toggle alternately in opposite directions, a first link of the linkage means adapted to impart the operating displacement to one of the tool element holding means, and a second link of the linkage means adapted to impart operat ing and locating displacements to the remain ing tool element holding means including operating the positioning means.

In order that the invention may be well understood an embodiment thereof will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a side elevation view of a fastening machine taken with the jaws in their widest open position; Figure 2 is a similar view of the machine of Figure 1, but taken in its piercing position; Figure 3 is a similar view of the machine of Figure 1 and 2, but taken between its piercing and flattening positions; and Figure 4 is a cross-sectional view taken vertically through the center of the extreme left-end portion of the machine jaws when these are in the position shown in Figures 1 and 2.

The same reference numerals are used in the various figures to designate corresponding elements.

Referring to the drawings, these show a stationary main machine frame 10, which supports all of the other elements, and with respect to which any movements of these elements take place. The actuating power for the machine is supplied by a cylinder 11 which imparts reciprocating motion to a piston rod 12 extending downwardly from cylinder 11. Attached to piston rod 12 is a Y-shaped toggle linkage means consisting of links or elements 13, 14 and 15. For convenience in referring to these three elements of the toggle linkage, they will be referred to hereafter as follows. Element 13 will be spoken of as the "drive link" of the toggle linkage, element 14 as the first or "jaw link", and element 15 as the second or "positioning link". As the discussion progresses the reasons for this terminology will appear, although it is desired to emphasize that no restrictive connotation is to be attributed to this terminology.

It will be apparent that up-and-down movement of piston rod 12 in response to actuation by cylinder 11 will cause drive link 13 to also move up-and-down together with a pivoting movement about pin 16. These up-anddown movements of drive link 13 will then "translate" into spreading and folding movements between jaw link 14 and positioning link 15. In so doing, these latter links will pivot about pin 17. Near their ends remote from pin 17, each of links 14 and 15 is provided with another pivot pin, link 14 being so provided with pin 18 and link 15 being so provided with pin 19. These pins 18 and 19 serve to constrain the movements of these remote ends of jaw link 14 and positioning link 15 in a direction generally transverse to the movement of piston rod 12 and drive link 13, i.e. in horizontal directions in the drawings. To that end, these pins 18 and 19 are trapped within slots 20 and 21 respectively. However, these pins also permit rotation of the remote ends of jaw link 14 and positioning link 15. By virtue of all of this, it will be seen that, as the piston rod 12 moves downwardly from the position shown in Figure 1, the angle included be tween jaw link 14 and positioning link 15 will gradually widen and, as is shown in Figure 2, will ultimately become 1800, that is the linkage means will be in its toggle condition.

Further downward movement of piston rod 12 will carry the linkage means downwardly beyond toggle so that the pin 17 is actually below the position shown in Figure 2 and the angle defined between jaw link 14 and positioning link 15 is again less than 1800 but open upwardly rather than downwardly as shown in Figure 1. This relationship is illustrated in Figure 3. As the piston rod 12 than moves back upwardly, the jaw and positioning links 14 and 15 will again pass through a toggle condition in which the angle defined between them is 1800. As the piston rod continues further upwardly, they will progressively reassume the position illustrated in Figure 1.

At the left-hand end of the machine as that machine is illustrated in the drawings, there is a jaw assembly generally designated by the numeral 25. This jaw assembly in cludes three tool elements including a piercing punch 26 carried by a piercing punch holding means comprising a holder 27 which, in tum, is held for horizontal movement by a piercing punch slide 28 which is mounted for horizontal reciprocating movement within main frame 10.

To the left of piercing punch 26, and as particularly visible in the cross-sectional view of Figure 4, there is a piercing die 29 so dimensioned as to be capable of cooperating with piercing punch 26, when the latter is brought into cooperative relation with the piercing die, in a manner described more fully hereafter to pierce - a multi-layer workpiece in the partial manner required by the type of joint being made. Figures 2 and 3 of the drawings show such a workpiece 30 in the position in which it is operated upon by the machine. This structure may, for example be the perimeter of an automobile hood turned, in this case, upside down from its ultimate intended position for the purpose of being worked upon by ths machine.

The hood consists of an outer metal surface 31 and an inner liner 32 which may be made of metal or plastics, as desired. The important thing to note about this workpiece 30 is its complex, re-entrant configuration at the location which is to be used for forming joints between the inner and outer layers.

Within the interior of die 29, there is positioned the swaying or flattening punch 33 (see again particularly Figure 4). The means which holds the piercing die 29 and swaging punch 33 combination consists of three slides reciprocable within the frame 10 from right to left and back again in the drawings. The three slides consists of two outer slides 34 between which is sandwiched an inner slide 35. The flattening punch 33 is carried by this inner slide 35 where as the die is carried by the outer slides 34.

Turning now to the opposite, or right-hand end of the frame 10 of the machine, it will be seen that there is positioned at this righthand end a positioning means which is collectively designated as positioning assembly 40. This positioning assembly includes an end plate 41 which is fixedly attached and terminates in the inner slide 35 and which extends at right angles to that slide, i.e.

into and out of the plane of the paper in the drawings to a lateral distance wide enough to also encompass the width of the two outer slides 34.

The outer slides 34, themselves, terminate in inclined end surfaces 34a. Between these inclined end surfaces 34a and end plate 41, there is positioned a camming means or wedgeshaped member 42 having a plane surface portion 42a which mates with the inclined end surfaces 34a of the outer slides 34. One such wedge-shaped member 42 is positioned, adjoining the inclined end surface 34a of each outer slide 34. These wedge-shaped members 42 are held in place but with limited vertical movement permitted, by means of pins 43 and 44 slidable within slots 45 and 46 respectively. Also mounted for pivoting about pin 44 is a three-fingered cam 47.

Trapped within slot 48 of this cam is a coupling means comprising a pin 49 fixedly attached to wedge-shaped member 42. A pin 50 protruding from an extension 51 of positioning link 15 is capable of abutting against either finger edge 52 or finger edge 53 of three-fingered cam 47. The former position is shown in Figure 1, the latter in Figures 2 and 3.

Finally, attention is invited to guide roller 54 and cam surface 55, the former being fixedly atached to frame 10 and the latter being provided along the edge of drive link 13 which is adjacent to guide roller 54.

In operation, the machine shown in the drawings is initially brought into the position shown in Figure 1. In this position, the piercing punch 26 has been retracted to the right and the assembly of both inner and outer slides 35, 34 has been moved to the left by a distance equal to the space shown in Figure 1 between the right-hand edge of stop member 41 and the lefthand edge of the stop member 56 which is firmly attached to frame 10 and absolutely limit the rightward movement of these inner and outer slides 35, 34. It will be apparent that the rightward movement or retracting movement of piercing punch 26 was accomplished by the rightward movement of pin 18 and its entrainment of piercing punch slide 28 in the process as the toggle linkage means 13, 14, 15 was being brought into the position illustrated in Figure 1. Likewise the leftward movement of the inner and outer slides 35, 34 was produced by the movement from right to left of pin 19 under the influence of the same toggle linkage movement.

What this does is to, in effect, open wide the jaw assembly 25 of the machine. This then enables insertion into that jaw assembly, and location in an operating position between die 29 and piercing punch 26, of the workpiece to be joined such as that shown at 30 in Figures 2 and 3. Incidentally, this position of the inner and outer slides 35, 34 of Figure 1 is indicated again in broken lines in Figure 2, in order to show most clearly the difference between these two Figures insofar as the positioning of the inner and outer slides is concerned.

Also at this stage in the operation of the machine, the three fingered cam 47 is in the position shown in Figure 1, by virtue of the fact that pin 50 bearing against finger edge 52 rotates this cam into that position about pin 44. Such rotary movement in turn is transmitted to wedge 42 through pin 49 trapped within slot 48 and wedge 42 therefore assumed its lowermost position. It will be recognized that up and down movement of wedge 42 in turn translates into right and left movement of outer slides 34, by virtue of the mating camming surfaces 34a, 42a at which the wedge 42 and the outer slides 34 meet. Thus the downward-most position of cam 42 shown in Figure 1 corresponds to the rightmost position of outer slides 34 insofar as the right and left displacement of these outer slides 34 is concerned which is imparted by up and down movement of wedge 42.

It is desired to emphasize that this rightleft movement of outer slides 34 is to be carfully distinguished from the right-left movement of both outer slides 34 and inner slides 35, which is accomplished not by up and down movements of wedge 42 but by overall movements of the inner and outer slides assembly simultaneously under the influence of pin 19 carried by positioning link 15. As previously discussed these right-left movements of the entire assembly of inner and outer slides open and close the jaw assembly 25 for locating the tool elements in an operating position. In contrast, the rightleft movements of outer slides 34 only, under the influence of up-down movement of wedge 42 affects only the right-left position of die 29. As will be explained more fully hereafter this position determines whether a peircing or a swaging function is accomplished at any given stage by advance of piercing punch 26 during operation of the machine.

Figure 2 shows the same fastening machine at a later stage in its operation than Figure 1, and specifically with the jaw link 14 and the positioning link 15 in their toggle condition reached as a result of downward movement of drive link 13 from the position illustrated for that drive link in Figure 1.

One important change which will be discerned in Figure 2 as compared with Figure 1 is that the assembly of both inner and outer slides 34, 35 has moved to the right up against stop member 56. This was the result of rightward movement of pin 19 within slot 21 during straightening of jaw and positioning links 14, 15. Therefore both piercing die 29 and flattening punch 33 have been carried to the right by the same amounts, i.e. they remain in the same relative positions which they occupied in Figure 1 but further to the right. At the same time, piercing punch 26 has been moved leftward under the influence of pin 18 acting through slot 20 upon slide 28. In fact this has taken place to such an extent that piercing punch 26 has traversed both thicknesses of material 31 and 32 and has displaced these into the interior space within die 29 permitted by the retracted positioning of flattening punch 33 within the die.

Attention is invited to the fact that wedge 42 remains in the same downward-most position as in Figure 1. Although extension 51 from positioning link 15 has pivoted, and so has pin 50 to the extent that it is no longer bearing upon finger edge 52 of three fingered cam 47, nevertheless this pivoting has not been of sufficient magnitude to cause the three fingered cam to also rotate. Rather, the pin 50 has at this point (Figure 2) traversed the space between surfaces 52 and 53, during which it exerts no turning force upon the three fingered cam 47 and, as a result, also no up or down moving force upon wedge 42.

In Figure 3 the downward movement of drive link 13 has continued carrying the jaw and positioning links 14, 15 beyond their toggle condition and into the reverse folded position from that which they had in Figure 1. This causes no significant movement of piercing punch 26 because, although pin 18 slides rightwardly, there is "play" provided by slot 20, so that this small amount of rightward movement is not transmitted to a significant degree to piercing punch 26.

On the other hand, this further downward movement of drive link 13 does cause a change in the situation at the positioning assembly 40. In particular, the extension 51 of positioning link 15 pivots even further up beyond the position shown in Figure 2 and so does pin 50 protruding from this extension 51. This further upward movement of pin 50 is now transmitted to three fingered cam 47 through bearing of pin 50 upon finger edge 53. The cam 47 consequently rotates clockwise about pin 44 and this clock wise movement is in turn translated into an upward movement of wedge 42 by pin 49 within slot 48.

The effect of this movement of wedge 42 upwardly is to push outer slides 34 to the left with respect to the position which these occupied in Figure 2. For clarity, there is shown in Figure 3 in broken lines the position of the left-most edge of outer slides 34 which these occupied in Figure 2. This is to be contrased with the solid line position of this lefthand edge of slides 34 which is shown in Figure 3. The latter is the position which these outer slides 34 in fact occupy at the stage of operation of the machine represented in Figure 3.

The consequence of this leftward movement by the distance between the broken and solid line lefthand edges of outer slides 34 in Figure 3 is to move the piercing die 29 to the left by a corresponding distance but without affecting the position of flattening punch 33 which remains in the same location in which it was in Figure 2. Thus, in effect, the piercing die 29 is pulled away to the left from the two layers of material 31, 32 which had been pierced in the stage of operation illustrated in Figure 2.

In addition, however, and this very im portant, the construction of the slot arrange ment cooperative with pin 19, is such that this small leftward movement of the outer slides 34 has also been transmitted to the entire toggle linkage means 13, 14 and 15.

This linkage means has therefore been displaced to the left and, when the linkage means now returns to the toggle condition by virtue of upward movement of drive link 13 during upward movement of the reciprocating piston rod 12, the leftward excursion of piercing punch 26 will be greater than it was during the piercing action.

This result of providing not only the slot 21 in main frame 10, but also a shorter slot 21a in inner slide 35, while fixing pin 19 with respect to outer slide 34. When the outer slides move leftward because of upward movement of wedge 42, pin 19 moves leftward against the left-hand end of short slot 21e, and is maintained in that position during return through toggle of the linkage means.

The positioning link 15 must therefore pivot about that left-most position of pin 19, and the whole linkage, including the punch 26, is carried further to the left, causing the desired swaying action.

The idler 54 serves to restrain the drive link from moving further to the left than desired and cam surface 55 controls these excursions at the various stages of machine operation. This then results in subjecting the materials 31 and 32 to compression between the piercing punch 26 and the swaging punch 33. This differs from what has happened in the prior operation of the piercing punch when the material was subjected to piercing by interaction between piercing punch 26 and die 29 but not to compression between piercing punch 26 and flattening punch 33.

With the die 29 retracted to the left away from these layers of material 31, 32 at this stage in the operation of the machine (Figure 3) the result of this compression is a lateral expansion of the compressed material, thereby locking the joint in place.

It will be appreciated that, by selecting the distance which die 29 moves to the left during the displacement discussed in connection with Figure 3 above determines how much of the two displaced layers of material 32, 33 becomes subject to lateral spreading. If the leftward displacement of die 29 is only by the thickness of material layer 31, then only one of these displaced layers of material will be able to spread laterally during the compression or swaging action. On the other hand if the leftward displacement is equal to the thickness of both material layers 32 and 31, then both of these layers of material will be subjected to lateral spread. Intermediate displacements will give rise to intermediate spreading conditions.

The extent of such leftward displacement of die 29 is adjustable by appropriately modifying the positioning assembly of the machine. One such possible modification in volves the slope of the edges 34a, 42a. As this slope is made steeper relative to the horizontal, the distance of displacement of the outer slides 34 and with it the distance of leftward displacement of die 29 decreases.

However this would require a rather extensive modification of the machine involving removal of the outer slides and removal of wedge 42 and replacement of both with corresponding elements having their mating surfaces 34a and 42a set at a different angle.

A much easier way of achieving such adjustment is by the extent of vertical displacement of the wedge shaped element 42.

This can be adjusted readily by simply slipping three fingered cam 47 off its mounting shaft 44 and replacing it with a three fingered cam in which the angular spacing between finger edges 52 and 53 is different.

The smaller this angular spacing the greater will be the displacement of wedge shaped camming means 42 resulting from the operation of the machine. Conversely the wider this angular spacing the less will be this vertical displacement. A lesser vertical displacement of wedge shaped camming means 42 produces a smaller leftward displacement of die 29 and conversely a greater vertical displacement of wedge shaped camming means 42 produces a greater leftward displacement of die 29.

A still easier method of adjustment is by control of the extent of downward (reverse folded) movement of links 14 and 15 (see Figure 3). The further these links are moved downward beyond the toggle condition, the further extension 51 will move upwardly, and the more cam 47 will rotate. This, in turn, will move wedge 42 upward further, and cause greater leftward displacement of outer slides 34 bearing die 29. The converse is true for lesser downward displacement of links 14, 15. Thus, control of the downward excursion of piston rod 12 effects the desired control of die movement, within the limits of vertical movement of wedge 42.

Having now completed the piercing and swaging operation of the materials 31 and 32, thereby forming the desired joint in the edge of the workpiece 30, the upward movement of drive link 13 continues until that link ends up back in the position of Figure 1. This results in repositioning the jaw assembly 25 in the position illustrated in Figure 1. This involves piercing punch 26 being retracted to the right, while inner and outer slides 35 and 34 are being extended to the left but in such relative alignment that die 29 again protrudes sufficiently to the right beyond flattening punch 33 to permit piercing by piercing punch 26 in a subsequent operating cycle of the machine.

Many variations in the described machine are possible, for example, the specific shape of jaw assembly 25 can, of course, be varied to suit the particular hard-to-reach configura tion to be worked upon.

If more than one joint is to be made in close proximity, the machine can be widened and two or more punch-and-die elements positioned side-by-side, all actuated by the same mechanism.

The machine itself can be fixed, or "port able", e.g. suspended from a chain hoist for convenient movement to the work location, and so forth.

Variations are also possible in the camming arrangements of positioning assembly 40.

WHAT WE CLAIM IS: 1. A machine for operating on a workpiece comprising at least two layers to be joined, from opposite sides of the workpiece to form a locking joint therein, the machine being adapted to effect relative displacements of tool elements comprising a piercing punch, a piercing die and a flattening punch, both for locating the tool elements in an operating position in relation to a workpiece and for operating on the workpiece, the machine comprising; a machine frame adapted to remain stationary during locating and operating displacements of the tool elements; a respective means for holding each of the tool elements, each holding means being reciprocably mounted to the frame; positioning means mounted to the frame and comprising reciprocably movable means for changing the relative positions of the holding means; and toggle linkage means mounted to the frame and adapted to be reciprocably actuated so that the linkage passes through toggle alternately in opposite directions, a first link of the linkage means adapted to impart the operating displacement to one of the tool element holding means, and a second link of the linkage means adapted to impart operating a

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. volves the slope of the edges 34a, 42a. As this slope is made steeper relative to the horizontal, the distance of displacement of the outer slides 34 and with it the distance of leftward displacement of die 29 decreases. However this would require a rather extensive modification of the machine involving removal of the outer slides and removal of wedge 42 and replacement of both with corresponding elements having their mating surfaces 34a and 42a set at a different angle. A much easier way of achieving such adjustment is by the extent of vertical displacement of the wedge shaped element 42. This can be adjusted readily by simply slipping three fingered cam 47 off its mounting shaft 44 and replacing it with a three fingered cam in which the angular spacing between finger edges 52 and 53 is different. The smaller this angular spacing the greater will be the displacement of wedge shaped camming means 42 resulting from the operation of the machine. Conversely the wider this angular spacing the less will be this vertical displacement. A lesser vertical displacement of wedge shaped camming means 42 produces a smaller leftward displacement of die 29 and conversely a greater vertical displacement of wedge shaped camming means 42 produces a greater leftward displacement of die 29. A still easier method of adjustment is by control of the extent of downward (reverse folded) movement of links 14 and 15 (see Figure 3). The further these links are moved downward beyond the toggle condition, the further extension 51 will move upwardly, and the more cam 47 will rotate. This, in turn, will move wedge 42 upward further, and cause greater leftward displacement of outer slides 34 bearing die 29. The converse is true for lesser downward displacement of links 14, 15. Thus, control of the downward excursion of piston rod 12 effects the desired control of die movement, within the limits of vertical movement of wedge 42. Having now completed the piercing and swaging operation of the materials 31 and 32, thereby forming the desired joint in the edge of the workpiece 30, the upward movement of drive link 13 continues until that link ends up back in the position of Figure 1. This results in repositioning the jaw assembly 25 in the position illustrated in Figure 1. This involves piercing punch 26 being retracted to the right, while inner and outer slides 35 and 34 are being extended to the left but in such relative alignment that die 29 again protrudes sufficiently to the right beyond flattening punch 33 to permit piercing by piercing punch 26 in a subsequent operating cycle of the machine. Many variations in the described machine are possible, for example, the specific shape of jaw assembly 25 can, of course, be varied to suit the particular hard-to-reach configura tion to be worked upon. If more than one joint is to be made in close proximity, the machine can be widened and two or more punch-and-die elements positioned side-by-side, all actuated by the same mechanism. The machine itself can be fixed, or "port able", e.g. suspended from a chain hoist for convenient movement to the work location, and so forth. Variations are also possible in the camming arrangements of positioning assembly 40. WHAT WE CLAIM IS:

1. A machine for operating on a workpiece comprising at least two layers to be joined, from opposite sides of the workpiece to form a locking joint therein, the machine being adapted to effect relative displacements of tool elements comprising a piercing punch, a piercing die and a flattening punch, both for locating the tool elements in an operating position in relation to a workpiece and for operating on the workpiece, the machine comprising; a machine frame adapted to remain stationary during locating and operating displacements of the tool elements; a respective means for holding each of the tool elements, each holding means being reciprocably mounted to the frame; positioning means mounted to the frame and comprising reciprocably movable means for changing the relative positions of the holding means; and toggle linkage means mounted to the frame and adapted to be reciprocably actuated so that the linkage passes through toggle alternately in opposite directions, a first link of the linkage means adapted to impart the operating displacement to one of the tool element holding means, and a second link of the linkage means adapted to impart operating and locating displacements to the remaining tool element holding means including operating the positioning means.

2. A machine as claimed in claim 1, wherein the tool element holding means each comprise a respective slide for moving the associated tool element, the slides being reciprocable along paths parallel to each other.

3. A machine as claimed in claim 2, wherein the positioning means comprises cam means reciprocable along a path transverse to the paths of the slides and having a plane surface portion inclined with respect to the reciprocating path of the cam means, the inclined surface mating with a correspondingly inclined surface on the slide which holds the piercing die, whereby reciprocating movement of the cam means is capable of pro

ducing reciprocating movement of the piercing die.

4. A machine as claimed in claim 3, wherein the positioning means further comprises a pivotable, multi-fingered cam, and means coupling the pivotable cam to the reciprocable cam means so that pivoting of the cam in opposite directions can produce reciprocation of the cam means in opposite directions.

5. A machine as claimed in claim 4, wherein the positioning means further comprises a pin which is displaceable to alternately bear against confronting edges of adjacent fingers of pivotable cam, the pin being adapted to impart rotation to the pivotable cam in one direction when bearing upon one finger edge and in the opposite direction when bearing on the confronting finger edge.

6. A machine as claimed in claim 5, wherein the pin is mounted for displacement by the second link of the toggle linkage means.

7. A machine as claimed in any one of claims 2 to 6, comprising means responsive to predetermined movements of the second link of the toggle linkage means for reciprocating by the same distance along said parallel paths the respective slides holding the piercing die and the flattening punch.

8. A machine as claimed in claim 7, comprising means responsive to movements of the second link different from said predetermined movements to reciprocate the slide holding the piercing die without moving the slide holding the flattening punch.

9. A machine as claimed in any one of the preceding claims, wherein the toggle linkage means further comprises a drive link for causing the linkage means to reciprocate, the drive link being actuable to move substantially at right angles to the first and second links when these are in their toggled condition.

10. A machine as claimed in claim 9, wherein the means for actuating the reciprocating movement of the drive link comprises a hydraulic piston mounted on the frame, and a piston rod connected to the drive link.

11. A machine as claimed in claim 10, wherein a complete set of displacements of the tool elements is carried out during a single reciprocating cycle of the piston rod for locating the tool elements in an operating position and operating on the workpiece to form a locking joint therein.

12. A machine as claimed in any one of the preceding claims, wherein the tool holding means are so configured that the piercing die and flattening punch are capable of penetrating into a re-entrant shape defined by the workpiece.

13. A machine for operating on a workpiece comprising at least two layers to be joined, from opposite sides to form a locking joint therein substantially as herein described with reference to the accompanying drawings.