Apparatus for attaching self-piercing nuts to a panel

Abstract: Attaching apparatus (1) has a punch (3) for striking a self-piercing nut "N" to one side of a metal panel "W", a piercing-caulking die (5) facing the punch (3) and located on the other side of the panel (W), and a nut holder (4) having formed in it a guide passage (10) in which the punch (3) is slidable. The nut holder (4) further has a nut-feeding aperture (11) opened perpendicular to the passage (10), and the punch (3) is connected by a back plate (7) to a base (8), with the die (5) being driven towards and away from the punch (3). A cylinder fixed on the back plate (7) drives the nut holder (4) fore and aft along the punch (3), so that the nut (N) is fed through the aperture (11) into an area located near and ahead of the punch's end (3a) when the nut holder (4) is retracted. The punch's end (3a) will be located flush with or slightly protruding ahead of the end opening of the passage (10) when the holder (4) is extended. The apparatus is installable in a press of a small shut height and can attach nuts to an inner side of a metal plate of a shape such as a reversed-U or -L or hat-shape.

Description: The invention relates to apparatus for attaching self-piercing nuts to one side of a panel such as a metal plate. In such apparatus each nut driven by a punch has an end face to cooperate with a piercing-caulking die located on the other side of the panel and in alignment with the nut, such that the end face is forced to bite the panel to form therein a hole, whose rim is simultaneously caulked so as to deform plastically and become integral with the nut. Self-piercing nuts capable of being secured to a metal plate when the plate is pressed have been used and are being used more and more in the mass production of metal plate products particularly in the automobile industry. Apparatuses for attaching the self-piercing nuts to a panel usually comprises a punch located on one side of the panel and striking the nuts towards the panel and also a piercing-caulking die facing the punch and located on the other side of the panel. Such an apparatus further comprises a guide member through which the punch slidably reciprocates, and a nut holder having a path extending perpendicular to the guide member and terminating as an end aperture so as to feed the nuts. In many cases, such apparatus is incorporated in a pressing machine together with other pressing dies or tools. The nuts are not necessarily fixed only to a plane portion of a metal panel, but often fixed to bottoms defining bent or drawn portions of L-shape or U-shape. Typically, the prior art apparatus for fixing the self-piercing nuts onto a metallic panel are constructed in such a manner as disclosed for example in the Japanese Utility Model Publication No. 63-20512. This apparatus comprises a nut holder capable of sliding along and relative to a punch for striking each nut. The nut holder has a guide post secured thereto and extending in parallel with the punch. A spring disposed in the guide post always urges the nut holder towards its normal position. The guide post is designed to be long enough to protect the nut from jamming while sliding along the punch. In consequence, a portion (hereinafter referred to as "punch block") consisting of the punch and the nut holder in the apparatus must be of such an increased overall height of length that the apparatus is difficult to be installed in a pressing machine having a small "shut height". The punch block may have to he placed in a hollow recess of the metal plate (hereinafter referred to as "work-piece") that has been pressed into a reversed-L, reversed-U or hat shape. Correspondingly, the piercing-caulking die is located outside the workpiece. However, it is difficult for the prior art punch block to take its operable position in such a narrow space, due to such a large axial dimension. Thus, it has scarcely been possible to secure the self-piercing nuts to an upright wall of the hollow space. Patent specification JP-A-06134628, upon the disclosure of which the first part of claim 1 is based, discloses a pressing punch supported in a holder and operatively connected by a back plate to a ram. The punch is longitudinally aligned in series and operatively connected to a piston of a hydraulic cylinder. A nut holder as well as a caulking die are always kept still. Therefore, the punch has to reciprocate a greater distance, and such a linear series of the punch and cylinder/piston is rendered so lengthy axially thereof as disabling the device to work within a narrow space ( viz., within a relatively small "shut height" ). According to the invention there is provided apparatus for attaching self-piercing nuts to a metal panel, the apparatus comprising: a punch to be located on one side of the panel and capable of striking nuts towards the panel, the punch being rigidly connected by a punch holder to a back plate; a piercing-caulking die facing the punch and to be located on the other side of the panel; a nut holder having a guide passage formed to allow the punch slidably to reciprocate therein, the nut holder having a feed path extending perpendicular to the guide passage and terminating as a nut-feeding end aperture; and a pair of fingers built in the nut holder so as temporarily to hold the nut in place within the guide passage after the nut has passed through the end aperture into a delivery area located near and ahead of a fronted end of the punch, wherein the back plate is connected to and supports a rear end of the punch; characterised in that a double-acting pneumatic cylinder is secured to the back plate and has a piston rod extending in parallel with the punch; and the nut holder is operatively connected to the piston rod so as to be driven fore and aft along the punch, so that the nuts are supplied through the end aperture into the delivery area when the nut holder is at its extended position; wherein the frontal end of the punch is located flush with or slightly protrudes ahead of an end opening of the guide passage so that the feed path is closed by the punch when the nut holder is at its retracted position. Preferably the apparatus further comprises a guide post fixed on the nut holder extending in parallel with the punch, wherein the guide post is slidably inserted in a bearing sleeve, which is fitted in a bearing hole formed in the punch holder. Advantageously the back plate rigidly connects the punch to a base, and the piercing-caulking die facing the punch is driven towards and away from the punch in response to movement of the pneumatic cylinder; wherein the piercing-caulking die is capable of being driven towards the panel so as to press it against the punch, while moving the panel and the nut holder rearwardly in unison with each other a small distance so that the nut comes into contact with the panel, with the punch thrusting the nut onto the panel, whereby the nut and the die cooperate with each other to pierce a portion of the panel and simultaneously the die caulks a rim around a hole thus formed through the panel so as to secure the nut thereto, before the pneumatic cylinder retracts the nut holder away from the thus attached to the panel. Preferably the punch and the die facing one another stand substantially horizontally and in alignment with each other. Such apparatus can have a punch block whose length or height in its axial direction is reduced to such an extent as to be installed in any pressing machine of a small shut height, thereby allowing the end face of each self-piercing nut to be secured to an inner vertical wall that defines a narrow space of a U- or the like shape formed in a metallic panel. In operation, the pneumatic cylinder will drive the nut holder forward and towards its extended position so that a leading one of the nuts can be supplied through the feed path and end aperture thereof and into the delivery area. Then, the punch and the piercing-caulking die will be driven towards each other until the die comes into contact with a desired portion of the panel, before striking the nut at its rear face with the punch so that the nut's front face bites and pierces the desired portion. Simultaneously with the punching of the panel to form a hole at that portion, the die will caulk the rim of the hole to deform and become integral with the self-piercing nut. Subsequently, the cylinder will pull the nut holder back to its retracted position away from the nut thus secured to the panel. The die will also be retracted at the same time so that the panel having the nut secured thereto is freed to undergo the next manufacturing process. The retracted nut holder keeps the end aperture closed by the punch so as not to feed the succeeding nut, until opened again to feed it when the nut holder advances forward again in the next cycle. The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which:- Figure 1 is a front elevation of an apparatus for attaching a self-piercing nut to a panel according to the invention and shown partly in cross section; Figure 2 is also a front elevation of the apparatus of Figure 1 shown in a state in which one nut has just been struck to and pierced the panel; Figure 3 is a front elevation of the apparatus of Figure 1 in a state in which the nut has just been fixedly attached to the panel; Figure 4 is a vertical cross section of a punch block incorporated in the apparatus of Figure 1 and comprising a punch and a nut holder; and Figure 5 is a plan view of the punch block. Referring to the drawings, Figure 1 shows apparatus for attaching self-piercing nuts in the horizontal direction to a metal panel, viz. a workpiece "W" that has been bent into a reversed-U shape. Figures 2 and 3 illustrate in sequential order the operation of the apparatus shown in Figure 1. As seen in these figures, in apparatus 1 an operative portion referred to as a punch block 2 comprises a striking punch 3 and a nut holder 4, and can be located inside the workpiece "W". Correspondingly, a piercing-caulking die 5 is to be located outside the workpiece. The striking punch 3 is rigidly connected by a punch holder 6 to a back plate 7. This back plate 7, contacting and supporting the basal end of the punch 3, is fixed on a base 8 such that the punch 3 protruding sideways has its axis extending in a horizontal direction. The piercing-caulking die 5 disposed outside the workpiece "W" also extends horizontally to face the striking punch 3. The die 5 has its axis in alignment with that of the punch 3. A cam slide of a pressing machine not shown will drive the die 5 to reciprocate along its axis towards and away from the punch 3. As is best seen in Figure 4, the nut holder 4 has a guide passage 10 formed therein to receive and permit the striking punch 3 to slide fore and aft. The nut holder 4 further has a feed path 12 extending perpendicular to the guide passage 10. The feed path 12 formed through a chute portion 4a of the nut holder has a nut-feeding end aperture 11 opening into and communicating with the guide passage 10. A chute hose 14 is attached by a joint 13 to the rear end of the chute portion 4a, so that self-piercing nuts "N" supplied through the hose 14 can advance through the feed path 12 and the end aperture 11 into a delivery area. This area defined in the guide passage 10 is located near and in front of the distal (viz. frontal) free end 3a of the punch 3. A pair of fingers 15 are provided in the nut holder 4 so as temporarily to hold the nut "N" in place within the guide passage 10. The nut holder further has a sensor 16 to detect the nut "N" having entered the delivery area. Since the striking punch 3 is fixed to the base 8, the nut holder 4 has to reciprocate along, relative to and axially of the punch. In order to smooth such a reciprocation, a guide post 17 fixed on the nut holder 4 extends in parallel with the punch 3. This guide post is slidably inserted in a bearing sleeve 19, which is fitted in a bearing hole 18 formed in the punch holder 6 mentioned above. A pneumatic cylinder 20 having a base end secured to the back plate 7 is located adjacent to the punch holder 6. The cylinder 20 is the double-acting type has a piston rod 21 extending in parallel with the punch 3. A distal end of the piston rod 21 is connected to the chute portion 4a of the nut holder 4. Thus, the rod 21 and the holder 4 can move fore and aft in unison with each other, and long the punch 3. When the nut holder 4 is temporarily at its extended position shown by the solid lines in Figure 4, a nut "N" can transfer from the end aperture 11 to the delivery area formed in the guide passage 10. If, on the contrary, the nut holder 4 is at a retracted position shown by the phantom lines in figure 4, the frontal end 3a of the punch 3 will stand in flush with or slightly protrude out of an end opening of the passage 10. The nut holder 4 temporarily held at such a retracted position will close the nut-feeding end aperture 11 of the feed path 12, so that a succeeding nut "N" is prevented from undesirably entering the guide passage 10. The base 8 has brackets 25 and 26 secured to its front and rear sides, respectively to support the workpiece "W" to which the self-piercing nuts "N" have to be attached. A stopper 27 protruding from the front bracket 25 serves to hold the workpiece at its correct position. Figure 1 shows the described apparatus 1 in its state ready to strike and attach the nut to a panel. The nut holder 4 is urged by the pneumatic cylinder 20 to take its foremost position. The nut "N" is held in the delivery area within the guide passage 10. The front face of the nut holder 4 is in contact with the inner face of a vertical wall of the workpiece "W" held at its correct position. The piercing-caulking die 5 is at a retracted position. Next, the die 5 will be driven towards the workpiece "W" so as to press the workpiece against the punch 3. In consequence, the workpiece and the nut holder 4 will be moved in unison and rearwardly a small distance along the punch 3, against the resistance imparted by the pneumatic cylinder 20. Thus, the punch 3 will assume a thrust position relative to the nut holder, as if having moved forward a little. As a result, the self-piercing nut "N" is thrust strongly by the punch 3 towards the workpiece "W" as shown in Figure 2, so that the front face of the nut pierces a portion of the workpiece. At the same time, the piercing-caulking die 5 will caulk the rim around the thus pierced hole so as to fix the nut on the workpiece. Once the nut is struck and attached to the workpiece, the pneumatic cylinder 20 will retract the nut holder 4 away from the nut "N" attached to the workpiece"W", as shown in Figure 3. The piercing-caulking die 5 is also retracted to liberate the workpiece, which will then be lifted and transferred to a subsequent work station. In the described embodiment, the nut "N" is struck horizontally to be attached to a vertical wall of workpiece "W" which is of a reversed-U shape. However, the apparatus provided herein may also be used to strike the nuts upward to be fixed to a lower side of any workpiece's top. The apparatus can be installed in a pressing machine of a small "shut height". In summary, the striking punch is slidably inserted through the nut holder which in turn is driven fore and aft along the punch by the double-acting pneumatic cylinder. Therefore, the punch block consisting of the punch 3 and nut holder 4 in this apparatus can be of such a small dimension in the direction of their axes as to be installable in a pressing machine of small shut height. Self-piercing nuts can thus be attached to an inner side of a workpiece that may be of reversed-U or -L shape or hat-shape or the like. The nut holder at its retracted position closes the nut-feeding aperture so as reliably to inhibit succeeding nuts from entering the delivery area.

Claims: Apparatus for attaching self-piercing nuts to a metal panel (W), the apparatus (1) comprising: a punch (3) to be locate on one side of the panel (W) and capable of striking nuts (N) towards the panel (W), the punch (3) being rigidly connected by a punch holder (6) to a back plate (7); a piercing-caulking die (5) facing the punch (3) and to be located on the other side of the panel (W); a nut holder (4) having a guide passage (10) formed to allow the punch (3) slidably to reciprocate therein, the nut holder (4) having a feed path (12) extending perpendicular to the guide passage (10) and terminating as a nut-feeding end aperture (11); and a pair of fingers (15) built in the nut holder so as temporarily to hold the nut (N) in place within the guide passage (10) after the nut has passed through the end aperture (11) into a delivery area located near and ahead of a frontal end (3a) of the punch (3), wherein the back plate (7) is connected to and supports a rear end of the punch (3); characterised in that a double-acting pneumatic cylinder (20) is secured to the back plate (7) and has a piston rod (21) extending in parallel with the punch (3), and the nut holder (4) is operatively connected to the piston rod (21) so as to be driven fore and aft along the punch (3), so that the nuts (N) are supplied through the end aperture (11) into the delivery area when the nut holder (4) is at its extended position; wherein the frontal end (3a) of the punch (3) is located flush with or slightly protrudes ahead of an end opening of the guide passage (10) so that the feed path (12) is closed by the punch (3) when the nut holder (4) is at its retracted position. Apparatus according to claim 1, further comprising a guide post (17) fixed on the nut holder (4) extending in parallel with the punch (3), wherein the guide post (17) is slidably inserted in a bearing sleeve (19), which is fitted in a bearing hole (18) formed in the punch holder (6). Apparatus according to claim 1 or claim 2, wherein the back plate (7) rigidly connects the punch (3) to a base (8), and the piercing-caulking die (5) facing the punch (3) is driven towards and away from the punch (3) in response to movement of the pneumatic cylinder; wherein the piercing-caulking die (5) is capable of being driven towards the panel (W) so as to press it against the punch (3), while moving the panel (W) and the nut holder (4) rearwardly in unison with each other a small distance so that the nut (N) comes into contact with the panel (W), with the punch (3) thrusting the nut (N) onto the panel (W), whereby the nut (N) and the die (5) cooperate with each other to pierce a portion of the panel (W) and simultaneously the die (5) caulks a rim around a hole thus formed through the panel (W) so as to secure the nut (N) thereto, before the pneumatic cylinder (20) retracts the nut holder (4) away from the nut (N) thus attached to the panel (W). Apparatus according to claim 3, wherein the punch (3) and the die (5) facing one another stand substantially horizontally and in alignment with each other.

Inventors: SHINJO HIROSHI, SHINJO, HIROSHI
Applicants: SHINJO SEISAKUSHO YK, YUGENKAISHA SHINJO SEISAKUSHO
Application year: 1995
Main classification: B23P19
IPC codes: B23P19