A METHOD FOR JOINING TWO OR SEVERAL OVERLAYING SHEET FORMED MEMBERS TOGETHER, METAL OR NON-METAL, AND AN APPARATUS FOR CARRYING OUT THE METHOD

Abstract: A method for joining together two or several overlaying sheet formed members (10, 11), metal or non-metal, at which a coaxial arrangement of a punch (12), a die (9) and an anvil (Y) cooperate by means of their relative movement. The punch (12) carries out a first movement coaxially towards said die (9). Thereafter the anvil (Y) moves in the opposite direction. The anvil (Y) is axially blocked and said punch (12) carries out a second movement coaxially towards said anvil (Y) to a position between the anvil (Y) and the punch (12) which is dependent on the applied forces, the thickness, the number and the material of the sheet-formed members (10, 11).

Description: A METHOD FOR JOINING TWO OR SEVERAL OVERLAYING SHEET FORMED MEMBERS TOGETHER, METAL OR NON-METAL, AND AN APPARATUS FOR CARRYING OUT THE METHOD. TECHNICAL FIELD This invention relates to methods for joining two or several overlaying sheet formed members together, metal or non metal, and apparatuses for earring out such methods. BACKGROUND ART It is well known that a pair of overlaying metal members could be joined together by lancing and forming a part of one member through an unblanked part of the other member, and thereafter staking the lanced and formed part of the one member to an adjacent surface of the other member to secure the members together in overlaying relation. For example the US-A-3 924 378 shows such a joining operation carried out by means of an apparatus having two separately actuatable rams, one of the rams carrying a lancing and forming die and the other ram carrying a flattening punch or anvil whereby the one ram performs the lancing and forming operation and the other ram performs the staking operation. The apparatus is provided with adjustment means so that the upper sheet or sheets of the displaced section is not engaged by the downwardly moving flattening punch until the lowermost sheet of the displaced section is uncovered by the upwardly moving die so as to allow the lower sheet of the displaced section to be spread SUBSTITUTESHEET while the upper sheet or sheets are still confined by the die. Thus, said adjustment means must be operated for different thickness of the sheets. US-A-4 035 901 shows an apparatus having a single reciprocating head provided with a first means, i.e., a die, to perform the lancing and forming step on a first stroke of the head and provided with a second means, i.e., an anvil, that performs the staking operation on the second stroke of the same head. When the thickness of one or several of the sheets to be joined together or the material of the sheets is changed the stroke length of the first and the second strokes must be adjusted. GB-A-1 603 231 shows another machine for making a joint of the above entioned type. In this machine the moving head comprises the punch which in a first stroke pierces the sheets against the die placed underneath said sheets. Before the second stroke the die as well as the anvil are axially repositioned by means of holding means having inclined plane surfaces. If the thickness of the sheets is changed the reposition movement must be adjusted. The above examples of prior art all disclose systems having a relatively simple one-piece, non-expansible die. The corresponding machines are in principle of the two-stroke type. The second stroke is carried out with the deformed sections of the sheets at least partly outside the die. However, other systems and apparatuses operating with only one stroke are known in which the die is laterally expansible. In this type of apparatuses the second part of the joint-forming-process takes place inside the die. US-A-4 459 735 discloses an apparatus and a method of this type. By necessity the design of the die is much more complicated in a system like this and the choice of Su» 3 πτ material for the die might be critical. Thus the life expectation for such a die is comparatively low which makes the maintenancey costs high for the tool. In addition one and the same die cannot be used if the thickness of the sheets is changed. DISCLOSURE OF THE INVENTION One object of the present invention is to provide a method for joining together two or several overlaying sheet-formed members in a two-stroke process which method can produce a first type of joint with a single set of die, punch and anvil and without adjustment of said units for different sheet thickness, number or material. Another object of the invention is to provide an apparatus for carrying out said method, capable of producing at least two different types of joints, e.g. leak proof and non-leak proof joints, using different sets of die, punch and anvil. Due to the fact that the mechanical forces needed to make the joint according to the inventive method are comparatively low it is also possible to design the apparatus to be very light and compact for the use as a versatile hand-held tool. A further advantage of the invention is that the life expectations for the tool units punch, die and anvil, especially the critical die, are high. This is due to the relatively rugged design of the die compared to known designs. Our invention which provides a solution to the said technical problems is characterised according to the appended claims. BRIEF DESCRIPTION OF THE FIGURES Other objects, uses and advantages of this invention are apparent from the reading of this description which proceeds with reference to the accompanying drawings forming part thereof and wherein: Figure 1 shows an apparatus according to the present invention implemented as a hand held tool. Figure 2a is a diagram showing on a time scale the motion of three essential parts of the machine. Figure 2b is a signal diagram showing the input and output signals to and from the apparatus according to figure 1 as well as certain internal signals of the connected control unit. Figure 3 shows the essential phases of a complete operation cycle. Figure 4 shows a second embodiment of the control unit. Figure 5 shows a third embodiment of the control unit. Figure 6 shows a fourth embodiment of the control unit. Figure 7 shows an alternative arrangement of the punch, die and anvil according to the invention. Figure 8 shows a type of joint which could be produced by means of the arrangement according to figure 7. Figure 9 shows examples of sections through joints according to figure 8. Figure 10 shows a section through a circular joint which could be produced with an arrangement according to figure 1. DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows an apparatus according to the present invention. The embodiment refers to a handheld tool, but the principles of the method and the apparatus are applicable to stationary equipment as well. The main parts of the machine are the body 1 with the handle 20. The body is provided with three moving systems. The first of those systems constitute a single-acting cylinder-piston assembly with a piston X in the cylinder 2 and a spring 13. The piston is mechanically coupled to a punch 12 which is moved by the piston. The second moving system comprises a movable anvil Y, a spring guiding member 4 and a spring 5. The member 4 transfers the forces from said spring 5 to the anvil Y. All said parts are contained in the cavity 3. The anvil Y is coaxially movable with the punch 12. In one direction, i.e to the right in figure 1, the anvil is moved by means of forces from the spring 5 transfered through the member 4 and in the other direction it is moved by means of forces from the punch 12. In this particular embodiment the anvil Y is guided by a die 9 which cooperates with the punch 12. The third moving system is also a single-acting cylinder-piston combination 6,8,7,21. The piston 6 is mechanically coupled to the blocking member Z which acts on the anvil Y. In order to operate the three different moving systems hydraulic and/or pneumatic pressure signals are connected SUBSTITUTESHEET to the systems by means of conduits or channels 15,16,17 within the body 1. A handle 20, scematically shown in figure 1, is fixed to the body 1. The handle is provided with a manual valve 19 which in this case is a three way/ two position/ normally closed valve having a trigger 18. The fluid input/output ports of the tool are marked G, A, H, C, P and the corresponding fluid signals are designated g, a, h, c, p. For the operation of the tool the input/output ports have to be connected to a control unit which could be designed in many different ways. The control unit provides a sequence of signals to the different ports during the operation cycle. Figure 2b shows a signal diagram for the input/output signals at the respective ports during one complete operation cycle and figure 2a the resulting movements of the three moving systems of the tool. In this part of the description only signals g, a, h, c, p are considered. The other signals illustated in figure 2b are internal signals of the control unit which will be described later on. The signals now considered have all been illustrated as binary signals in which the transfer between the two signal levels takes place without any time delay, in reality this is of course not the case but for the sake of simplicity the hydraulic/pneumatic signal time delay is not considered here. On the other hand the time delays in the physical movements of the three systems are much larger and have to be taken into account. These time delays are therefore shown in figure 2a. Although the movement between different positions of the systems are not linear in time, they have for the sake of simplicity been so illustrated in figure 2a. As mentioned above a certain sequence of signals must be provided at the input/output ports to make the tool work. Many different embodiments of control units capable of delivering such a sequence could be envisaged a few examples of which will be described below. At first a general description of the operation of the tool will follow without any reference to details of a specific control unit. Consider figures 1 and 2. Up to time to the tool is in its rest position having its control . unit connected to the power source, i.e. in this case pneumatic pressure, ready to operate. The input port P is during the whole cycle provided with pneumatic pressure which could be seen from figure 2b. In the following it is assumed that two sheets 10,11 which are to be joined together are positioned between the punch 12 and the die 9. At time to the trigger 18 is operated which causes the pressure from input P to be connected through the valve 19 to output A. As a response to this pressure raise at output A the control unit deliveres a high pressure hydraulic signal g to input port G and the first moving system. As mentioned above the minor time delays between the occurence of these signals are not considered here. The oil which now enteres the cylinder 2 of the first moving system causes the piston X to start its movement to the left in figure 1. The punch 12, moving with the piston X, will reach contact with the sheet 11 at time tl. When making a first type of joint, the punch 12 at the corresponding position will start to cut the two sheets and the anvil Y of the second moving system will be moved to the left in figure 1 against the force of the spring 5. This movement continues until the piston X reaches the position cl at time t2 illustrated in figure 1 and 2. At this position the punch has just cut through the two sheets 11 and 10 along part of the punch circumference. The length of the piston stroke is defined by the design of the first moving system. With an appropriate length of the punch 12 the corresponding position of the punch tip could, e.g.,be made flush with the common surface between the sheet 10 and the die 9. As can be seen from figure 2a the anvil has now reached the position c2. In the next step, at time t3, the control unit deliveres a signal c on the input C with a set time delay tl measured from the operation of the trigger. In the present embodiment this signal is a pneumatic signal. The signal acts on the third moving system of the tool and actuates the piston 6 which forces the blocking member Z against the anvil Y without engaging the blocking slot 22. At the same time the hydraulic pressure to the first moving system drops as can be seen from figure 2b. This means that the piston X of the first moving system will start moving to the right in the figure 1 forced by the two springs 13,5. The anvil Y and the two sheets 10,11, still in contact with the punch 12, will follow the movement to the right in figure 1. The third moving system is still under pressure and at time t4 the blocking slot 22 is just opposite to the blocking member Z. Thus, the anvil will be blocked in the corresponding position when the piston 6 moves forward. The third moving system could consequently also be considered as a position indicator for the anvil. When moving forward the piston 6 opens a conduit or channel for the pressure signal h which is an output signal from the tool to the control unit indicating that the anvil has reached a defined position and is now blocked. The control unit responds by once again delivering hydraulic pressure on input G of the tool. The direction of the movement of the first moving system is reversed and the punch 12 carries out a second stroke. As mentioned above the anvil is now blocked in position c3, cf., figure 2a. The deformed portions of the two sheets 10 and 11 are now outside or at least partly outside the die 9. Mechanical forces between the punch 12 and the anvil Y will now squeeze the deformed portions of the two sheets and make these portions expand laterally. As long as the operator holds the trigger nothing more will happen in the tool after the punch 12 has reached its final position which is dependent on the pressure of the signal g and the thickness and material of the sheets to be joined. The pressure will be set manually on the control unit to an appropriate value as described below. At time t5, in this particular embodiment defined as the moment when the trigger is released, all the signals except p return to zero and the tool returns to its rest position. The time interval between to and t5 is defined as t2 in figure 2. This time interval could of course alternatively be set internally in the control unit. At time t5, thus, the piston of the first moving system will once again reverse its direction of movement. At the same time the blocking member Z will release the anvil. As can be seen from figure 1 the blocking member is still blocking the spring guiding member 4 so that the anvil cannot move further to the right. Due to the mechanical deformations of the sheets around the punch they will follow the punch in its movement to the right until they reach the edge of the cylinder • housing in the tool gap. At this point they will be disengaged from the punch 12 which continues its motion to the right to the rest position. In the diagram 2b this moment corresponds to time t6. S U BS TITUTESHΞET Figure 3(I-V) shows the essential phases of a complete operation cycle. The tool as illustrated is the same as just described and the connected control unit is an exemple of such a unit capable of delivering the signals of figure 2b. The designations of the five figures(I-V) correspond to the same designations in figure 2. Figure 3(1) shows the status of the control unit when the input 38 is provided with pneumatic pressure from a standard source available in the workshop. The unit 27 is a standard air preparation unit including a filter, a regulator and a lubricator. This part of the control unit is not essential for the description of the operation of the circuit. It forms, however, part of a practical realisation of said circuit. As can be seen the input P of the tool is provided with the regulated pressure already at this stage. The inputs to the valves 29,28,25, all of the 3 way/2 position, normally closed, pressure controlled type, are also provided with regulated pressure. At the input of the valve 25 a second regulator 26 is arranged to set the pressure to the pneumatic-hydraulic booster 24 and thus the output hydraulic pressure to the input G of the tool which in its turn operates the first moving system of the tool. This state corresponds to the time before to in figure 2. As described above at time to the trigger was operated which caused an operating signal a to be transfered to the control unit, cf., figure 3 (II). When this signal is received by the control unit the following will happen. The valve 25 will open and the regulated pressure from its input will be communicated to the input of the booster 24. The signal a will also be conducted through the valve 30 which is of the 3 way/2 position, normally open, pressure controlled type, to the pneumatic OR-gate 33 and open the hydraulic, 3 way/2 position, normally closed valve 37. As a result the amplified hydraulic pressure at the output side of the booster 24 will be conducted through said valve to the input G of the tool. At the same time the pneumatic delay circuit 31,32 will be activated which starts the time delay tl, cf., figure 2. Assuming that the trigger is still operated the next change in the signal state at the output of the control unit will be decided by the time delay tl. The output signal b from the delay circuit is shown in figure 2b. At time t3, i.e at the end of said time delay, the high level of this signal is reached and the valve 29 will be opened delivering the pneumatic output signal c from the control unit cf., figure 3 (III). At the same time the valve 30 will be closed and the signal d returns to zero. Consequently the hydraulic valve 37 will also be closed. A leakage path is opened for the return pressure from the first moving system through the valve 37, the hydraulic restiction 34 and to the hydraulic accumulator 35. The booster 24 still delivers the amplified pressure on its output which is, however, now blocked by the valve 37. The leakage pressure from the first moving system back to the control unit is much lower which means that the checkvalve 36 is closed. By means of the restriction 34 it is possible to adjust the reverse ' speed of the piston X of the first moving system. When the signal h raises, at time t4 as described above, indicating the blocking of the anvil Y, the valve 28 will be opened, cf., figure 3 (IV). The regulated input pressure will thus be tranferred through the OR-gate 33 to the valve 37 and open this valve once again giving the hydraulic output pressure g which will start the second stroke of the first moving system of the tool. Finally, when the operator releases the trigger at time t5, cf.figure 3 (V), the signal a will return to zero and the remaining pressure from the pressure accumulator 32 of the delay circuit will leak through the check valve parallell to the flow restiction 31 back to the trigger valve of the tool where it is exhausted. This means that the signal b returns to zero and the valve 29 will be closed. When closing it brings signal c to zero which in its turn closes valve 30 and brings the blocking member to return to its rest position. " At this rest position the signal h will return to zero closing the valve 28 causing the hydraulic valve 37 to close. When the valve 37 closes the leakage path for the first moving system through that valve is opened once again. Due to the fact that the signal f has dropped to zero the piston of the booster is now free to move upwards. When the pressure at the output of the booster has dropped to the same level as the pressure in the hydraulic accumulator 35 the checkvalve 36 will open and connect a return oil flow from the accumulator and the first moving system of the tool back to the booster 24. Thus the final rest status is reached with all signals except the signal p at zero level and the operation cycle is completed Figure 4 shows a second embodiment of the control unit. The designations of corresponding components ' are the same. The main difference from what has been described above resides in the design of the hydraulic valve 37 here called 37' . In this embodiment this valve is controlled by means of pneumatic pressure in both directions. When using such a valve it- is possible to dispose of the pneumatic OR-gate 33 and the valve 30, shown in the first embodiment. Therefore a control unit according to figure 4 is cheaper. The two embodiments now described both operate with high pressure at the output from the booster during the whole operation cycle of the tool. In the figures 5 and 6 two other embodiments of the control unit are shown in which the output from the booster is not provided with a hydraulic valve. This means that in order to have the first moving system of the tool making two strokes the piston of the booster has to make two strokes. Now the aii- volume and consequently the corresponding pneumatic capacity in the booster is considerable which means that the stroke of the piston of the booster will be rather slow. Therefore, even if the two embodiments according to figures 5 and 6 could deliver the same signals to the tool as described above, the time scale will be different. In order to have the possibility to adjust the speed of the backward movement of the first moving system of the tool like in the previously described embodiments it is in the exemples of figures 5 and 6 possible to introduce between the booster 24 and the valve 25 and 25' respectively a parallell combination of a checkvalve and an adjustable pneumatic restiction. Of course many other configurations for the control unit could be conceived giving the same sequenεe of output signals to the tool. All the described embodiments of the control unit as well as the tool itself take the necessary power from the pneumatic pressure source 38. Other types of power sources e.g. electrical could of course be envisaged for the tool and/or the logic. Especially for stationary machines it would be possible with for instance cam driven mechanical actuators for the moving parts. The components 28, 33, 30, 31, 32, 29 of the first described embodiment of the control unit could for instance SUBSTITUTE SH ET be changed to electronic eqivalents and one of the pneumatic pressure regulators of the unit 27 and 26 respectively could in that case be disposed of. In the tool the trigger could be an electrical trigger and the blocking unit Z, 6, 7, 8, 21 an electro agnetical unit giving an electrical output signal h. Such a system would give the same input and output signals between the tool and the control unit as shown in figure 2b although some of them would now be electrical. A further envisaged embodiment has instead of the pressure booster 24 a hydraulic pump driven by an electrical motor. A substitution of the trigger by a pedal or arranging the feed-back signal h to be taken out from the first moving system are examples of changes within the general scope of this invention. When describing the tool and the operation sequence of the same above it has been assumed that the resulting joint will be of the non-leak proof type. In the first stroke of the punch 12 this will cut through the two sheets 10,11 along part of the circumference of the punch. However, other types of joints could be produced by means of the described method making use of a slightly different sets of punch, die and anvil in the tool. It is here referred to a leak proof type of joint of the same general type as described in the US-A-4 459 735 mentioned obove in the description of the prior art, cf. figure 10. As mentioned that system operates with only one stroke of the moving part of the machine and the die has laterally moving parts. In our system on the other hand the main moving unit of the tool makes two strokes. The dimensions of the cooperating punch and die are such that the punch in the first stroke does not cut through any part of the sheets but makes a preferably cylindrical deformation by a drawing action mainly in the clearance between the punch and the die. By means of the anvil the deformed portions of the two sheets are then brought outside the die before the second stroke takes place. The free lateral extrusion of sheet material then takes place during the second stroke. In figure 7 an alternative arrangement of the moving parts is shown. The same designations have been used for corresponding units. In this embodiment the die 9 is moved by the piston X towards the punch 12 in the fir-st stroke. The first predetermined relative position between die and punch is defined by the end position of the piston movement. The anvil Y is operated in the same way as described above. A joint which could be produced by means of this arrangement is shown in figure 8. Two sections through such a joint is shown in figure 9. S UBSTITUTESHEE

Claims: CLAIMS 1 Method for joining together two or several overlaying sheet formed members(10,11) , metal or non-metal,at which a coaxial arrangement of a punc (12) ,a die(9) and an anvil(Y) are caused to cooperate by means of their relative movements characterised in that it comprises the following steps said punch{12) (or die 9) is caused by means of applied forces to carry out a first movement in a first direction coaxially towards said die(9) (or punch 12) to a first predetermined relative position between punch and die which is independent of the thickness of or number of the sheet- formed members(10,11), said anvil(Y) is caused by means of applied forces to move in the opposite direction coaxially towards a second relative position between the anvil(Y) and the die(9) (or punch 12) which position is also independent of the thickness of or the number of the sheet-formed members(10,11) , said anvil(Y) is caused to be axially blocked in said second relative position, said punch(12) (or die 9) is caused by means of applied forces to carry out a second movement in said first direction coaxially towards said anvil(Y) to a third relative • position between the anvil(Y) and the punch(12) (or die 9) which is dependent on the applied forces, the thickness, the number and the material of the sheet-formed members(10,11) . 2 Apparatus for carrying out the method according to claim 1 for joining together two or several overlaying sheet-formed members, metal or non-metal, comprising a coaxial arrangement of a punch(12), a die(9) and an anvil(Y) moveable relative to each other characterised in that a punch(12) (or die 9) carrying member(X) is arranged to be moved, when actuated, in a first direction coaxially towards said die(9) (or punch 12) to a first predetermined relative position between punch and die which is independent of the thickness of or number of the sheet- formed members(10,11) , an anvil(Y) carrying member(4) is arranged to be moved by means of applied forces in the opposite direction coaxially towards a second relative position between the anvil(Y) and the die(9) (or punch 12) which position is also independent of the thickness of or the number of the sheet-formed members(10,11) , a blocking member(Z) is arranged to block axially said anvil(Y) in said second relative position, said punch (or die) carrying member(X) is arranged to carry out a second movement in said first direction coaxially towards said anvil to a third relative position between the anvil and the punch (or die) which is dependent on the applied forces, the thickness, the number and the material of the sheet-formed members.

Inventors: GUBBIOTTI LUCIANO, RAPILLARD PHILIPPE, GUBBIOTTI, LUCIANO, RAPILLARD, PHILIPPE
Applicants: BEREMA AB, CERAC SA, CERAC S.A.
Application year: 1989
Main classification: B21D39
IPC codes: B21D39