Device for a front automatic rivet feeding of a riveting machine and method for its implementation

Abstract: The device is suitable to the positioning of blind rivets constituted by a rivet head portion (2), a flange (3), and a pin, removable, in the opening of a riveting machine (10) and comprises a casing (12) enclosing the front end of the rivet machine and which forms a recess (32) finished at its front section by an elastic collet (1) with a central hole (33), the rivets reaching said recess (32) supplied by a lateral manifold (5), and it comprises means to displace the casing (12) lengthwise and telescopically with respect to the end of the riveting machine, in order to place the rivet pin (4), guided by a nozzle (13), inserted within a duct (34), previously intercepted by a retractable pivot (15), so that the displacement of the casing (12) producing a positioning of the rivet with its flange (3) protruding from the collet (1) and its head portion outside to the set ready to be riveted.

Description: The device this invention relates to consists in a uncomplicated automatic mechanism for feeding blind rivets of the type which include a rivet body or head portion, an annular flange or washer and a removable stem or pin, and which are designed for being arranged in the opening of a standard oil-pneumatic or pneumatic riveting machine usually marketed, with a head section which embodies a chuck which includes a gripping mechanism to lock the rivet pin or stem positioned within it, and a dynamic fluid cylinder for closing the said gripping mechanism and applying a backward tensile stress in order to deform the rivet head portion until the said stem is detached, which is being removed by suction through an duct axial to the said heat section, embodying likewise in general, means for individual feeding of the said rivets, for example by pneumatic conveyance, in a predetermined position toward the riveting gun. The device according to the invention was devised to constitute a set together with a pistol-type riveting machine which allows its use as self fed hand riveting pistol, to be incorporated to robot arms or, using suitable supports, work as a machine or static unit of automatic riveting, having access only by one of the sides of the two pieces to connect. As backgrounds of the invention, we can mention patents EP 285739, EP 491193, US 4205547, US 4027520, US 5042131, FR-A-2045297 and FR-A-2587246. The European patent EP 285739 discloses a device for positioning blind rivets, which is associated to a pistol body to which the blind rivets are fed, one by one, with the pin or stem in back position, comprising a collet which, through a set of levers moves to position the pin of related rivet in the interior of the front opening or mouth of the riveting head. The device proposed is complex, it takes a significant place, namely close to the front part of the riveting tool, which limits the operation freedom and when moving the rivet outside the said riveting tool, there exists the risk of causing accidents when handling the set. In addition, with this device a certain number of cycles could fail, due to a poor pointing of the rivet pin in the mouth of the riveting head, because of lack of guide. In the European patent EP 491193, it is disclosed an apparatus for feeding rivets to the front section of a riveting machine, where the rivets are presented and fed joined in a tape or support feeder, which moves forward on a slide, and by means of a lever which moves externally to the riveting tool, they are taken one by one and positioned in front of the riveting tool. A rivet positioning device embodying a tape or rivet feeder is likewise disclosed in above patent FR-A-2045297. These devices have the main drawback of requiring the said rivet tape (preparation and feeding), with subsequent incremental cost and manoeuvrability loss of the set, in addition to imply a significant structural complexity due to the support and forward movement means of the said slide in coordination with the own means of the riveting tool. In addition, rivets evacuation is performed directly down the floor or in an auxiliary deposit and in addition the scraps of the bearing tape have to be picked up. Patent US 4205547 proposes a rivet positioning device, which includes likewise a set of levers and collet outside the riveting tool for positioning the rivet pin or stem in the interior of the front opening of the riveting head. The said levers are mounted on a slide external to the body of the riveting tool for its displacement from a rivet collection point up to another one for conveying it to the said collet. This device likewise means a significant structural complexity and is very bulky, therefore it affects the tool manoeuvrability. French patent FR-A-2587246 discloses a device having similar characteristics, designed for a robot unit with guiding means for mentioned positioning levers. Patent US 5042131 discloses a device to feed rivets to a riveting tool, comprising a duct which leads to a recess, coaxial to and in the front of the riveting head , the end portion of the said duct being pivoting with respect to the grips of that riveting head, which, when moving forward takes the said tube sideward until catching the rivet by its pin , and when it goes backward, the tube returns to its feeding position. This device has the drawback of an irregular positioning of the rivets due to a poor orientation of the pivoting tube, which, in addition, sustains a wear because of the friction with the riveting head, compelling to use specially resistant and expensive materials, or to replace the said tube from time to time. The evacuation of the pins detached from the rivet requires that an auxiliary deposit is coupled to the riveting tool with subsequent increase of weight and limitation in the manoeuvre of the set. In this device, the collets which lock the rivet must be exaggeratedly opened (with subsequent over-effort on the retraction spring) to let the riveting head passes. As for patent US 4027520, it does not disclose a device that can be associated to a riveting tool, but a special gun in which the rivet is conveyed by pneumatic conveyance close to the front end of the said gun, having access to the interior of a recess frontally delimited by means of flexible collet, being thereafter held by a grip which is moving forward toward the said recess, and pushed until the rivet head portion protrudes externally to the gun and is ready for the riveting operation. The said structure is not applicable to a conventional riveting gun or tool, as in above disclosed devices, and, in addition, the initial position of the rivets in the said recess is critical, as they are conveyed to the said point by fluid dynamic means and at a certain speed, which may produce an incorrect arrangement of the rivet in the said recess which gives rise to problems, and requires that means for a temporary retention of the rivet in that recess are provided, until the rivet is held by the grip of the riveting tool. In addition, the expelling of rivet pins after the riveting operation, is performed directly outside, or it requires that a collecting container associated to the gun is provided, which, once more, means a restriction of the manoeuvrability. The device this invention is referring to tries to overcome above problems, and proposes for such purpose means and a methodology for positioning the rivets in the front section of a quite simple riveting tool, constituting a set applicable to any conventional tool such as a riveting gun or similar, which means a minimum volume increase and which virtually does not affect the working front section, involving only a slight increase of weight and therefore an optimum manoeuvrability of the set with evacuation of the rivet pins axially to the riveting tool, backwardly and up to a collection point at a distance from the working point, and a very safe positioning of the rivets allowing them to be held by the grips. The device is, in addition easily adaptable to any riveting tool and, namely, it is applicable as it has been said to riveting guns. For such aim, the device involved comprises a support associated to the riveting tool body dealt with, on which side pneumatic cylinders are fasten to, the said cylinders causing that an external casing which surrounds the gripping mechanism front end of the said riveting tool moves forward or backward, in due time, and which telescopically slides on itself. This casing incorporates at its end a plurality of collet fingers, in radial arrangement around an axis coaxial to the gripping mechanism axis, hinged by its back end to the casing, and which may be opened, defining a front central opening for the rivet passing, or to remain closed, locking the said rivet pin, an external elastic ring having been provided which tends to keep the said collet fingers in a closed position and a collar which encloses the back ends of the said collet fingers, with a small play. The casing possesses in addition an inlet side duct for the rivets conveyed by compressed air, according to conventional art, in a predetermined position. The device is following disclosed together with its methodology illustrated by means of its operation cycle: When the external casing is fully taken far from the gripholder, forwardly, a recess is formed between the gripholder and the collet fingers located at the end of the said casing, in whose interior comes the rivet through a side manifold connected to the inlet duct and coming from an automatic dosing vibrator located in a self-contained piece of furniture which incorporates the electro-pneumatic installation. When the external pneumatic cylinders makes the casing goes backward, the chamber existing between the fingers in radial arrangement and the pistol gripholder becomes shorter; this provokes that by means of some internal conicities performed on the internal face of the said fingers and an exchangeable guiding nozzle, superposed to the gripholder, the rivet is centered, its pin goes into a duct central to riveting grips and thanks to a retractable pivot incorporated in the gripholder which at a certain time obturates the said central duct, the rivet is outwardly pushed forcing in opening the collet fingers and remaining finally held by their pin, by the said fingers, ready for the riveting operation. Once riveting is performed, the pin detached from the rivet head portion remains locked by the riveting grips. The two external cylinders make the casing moves forward, the retractable pivot is taken apart releasing the central duct, at same time that the riveting grips release the pin which is sucked backward by a vacuum pump and conducted through a tube toward a collector located in a self-contained piece of furniture. At same time these operations are performed, the following rivet is automatically introduced in the recess. The displacement of the said retractable pivot is performed by means of a cam shape which operates it in correspondence with the forward movement of the casing toward the grip mechanism, or by a lever mechanism, driven by a pneumatic cylinder, controlled by a sequentially programmed electronic device to push the said pivot toward a position of interference with the central duct of the grip mechanism in due moment and regardless of the casing movement. A spring coaxial to the said retractable pivot tends to keep it apart from its position of intercepting the axial duct of the grip mechanism. The above and other objects, features and advantages of the invention will become more readily apparent from the following description, reference being made to the accompanying drawings in which : Fig. 1 is a top plan view of a riveting pistol incorporating a device according to the invention, in whose upper half, located above the lengthwise symmetry axis, the cylinder with the stem which operates the casing is shown in a retracted position; in the half located under the said symmetry axis, the said stem appears extended. Fig. 2 shows a longitudinal view partially in section, of the set of Fig. 1, by the plane of section II - II, with the casing in advanced position, the recess which is formed in its interior in the front of the grips of the riveting tool, lodging a blind rivet. Fig. 3 is a part section view, at larger scale, of the end portion of the casing, with detail of the assembly of one of the collet finger it embodies. Fig. 4 corresponds to a lengthwise view partially in section, of the set of Fig. 1, by the section taken along the plane IV - IV, with the casing in retracted position and the rivet located at the grip of the tool in a position ready for riveting. Fig. 5 is a front view of the tip of the moveable casing, which allows to see the three collet fingers it embodies, in the disclosed example. Figs. 6, 7 and 8 show three views in side elevation and part lengthwise section, of a pistol equipped with a device for feeding rivets, according to the invention, provided with means alternative to those of the drawings of the three first figures to displace the retractable pivot to a position of interference (a situation which is shown in Fig. 7), designed to intercept the central duct of the grip mechanism. The device according to the invention is applicable to the positioning of blind rivets formed by a rivet 2 body or head portion -2-, a flange or washer -3- and a pin or stem -4-, removable (see Fig. 2), in a riveting machine such as a fluid dynamic riveting pistol -10-, with a section of head which embodies a chuck -17- fed with a spring -7-, the said chuck comprises a gripping mechanism -25- designed for holding the pin -4- of the rivet positioned within thereof, and an internal fluid dynamic cylinder to close the said gripping mechanism and to apply a tensile stress with the purpose of deforming the rivet head portion -2- until detaching the said pin -4-, which is evacuated through a duct -9- axial to the said head section, which likewise embodies means for individual feeding of the said rivets such as a pneumatic conveyance, at a predetermined position, toward the said riveting pistol. The device, according to the invention, is characterized in that it includes: a casing as a sleeve -12-, which surrounds the front end of the gripping mechanism -25- of the riveting pistol, in coaxial arrangement thereof, the said casing -12- internally defines a recess -32- and is finished a- its front section by a collet -1- with a central hole -33- which, in its internal face, has a conic profile; a manifold -5- in a side of the casing -12- defining a passageway to supply rivets to the interior of the said recess -32- conducted by the said pneumatic conveyance means through a duct -35-, coupled to the said manifold -5-. a nozzle -13-, exchangeable, placed in superposition and alignment with the end of the duct -34- central to the gripping mechanism -25-, the said nozzle offers a conical profile oriented facing the distal end, provided with the said collet -1-, of the casing -12-; means to displace in a predetermined distance the said casing, lengthwise and telescopically with respect to the end of the chuck, co-aligned with the central duct -34- of the gripping mechanism -25-, to place the rivet pin --4-, guided by the nozzle -13-within the said duct -34-; means to intercept the axial duct -34- of the gripping mechanism -25- constituting a stop limiting the insertion for the rivet pin -4-, determining when ending the displacement of the said casing -12- a positioning of the said rivet such that the flange -3-thereof protrudes from the elastic collets -1- and the rivet head portion -2- remains outside the set ready for its insertion in a hole of a workpiece. In the embodiment given as example in the drawings, the said manifold -5- supplying the rivets, has an inclined orientation with respect to the lengthwise axis of the chamber -32- and has connected a flexible duct -35- to feed the rivets, the manifold -5- remaining in opposition with respect to the riveting pistol -10- handle or to a supporting element of the riveting tool involved. The means for displacing the casing -12, telescopically with respect to the chuck of the riveting pistol, comprise external pneumatic cylinders supported on a support -22- secured to the riveting pistol -10- body, and drawn in their two positions of retraction and extension in the two semi-halves of figure 1. The stems --14- which are oriented in parallelism to the duct axis - 34-, are connected by their ends to some appendages -18- solid with the casing -12- as it is shown in figures 1, 7 and 8. Fig. 1 likewise details an elastic stop -20-, coaxial to the said stems -14- designed to limit the displacement in retraction of the casing -12-. And a part -18- or coupling nipple of the pistol axial duct -9- (Fig. 2) is shown with a vacuum pump --11- for evacuating the pins detached from the rivets, which are advantageously conducted to a far collection point, by a flexible tubular duct -23-. As it can be seen in figures 3 and 5, the collet -1-, in the front part of the casing -12-, comprises a plurality of collet fingers -36- in radial arrangement around a coaxial axis with the central duct -34-, of the gripping mechanism -25-, hinged by their back end, which may be opened forming a front central opening having a diameter slightly larger than the washer -3- and body -2- of the rivet, or may remain closed defining a central front hole - 33-, suitable to lock the pin -4- of the same rivet, an external elastic ring -37- having been designed which tends to keep the said fingers -36- in closed position, and a collar -39- attached to the casing -12- which encloses the said back ends of the fingers -36-, with a small play. The articulation of the fingers -36- of the collet comprises an offset -38- of the said fingers back end, which is supported on an annular element -41- socketed in an annular groove -42- of the casing -12- external surface. As it can be seen in figures 2 and 6, a sleeve -24-connects the casing -12- to the body -10- front end of the riveting pistol, acting as guard. The means to intercept the duct -34- during the displacement of the casing -12- in order to constitute a penetration stop for the rivet pin -4-, in its access within the said duct, comprises a pivot -15- inserted in a drilled hole -8- lateral to the duct -34- which flows at a predetermined distance of the front end of the said duct, the said pivot -15- is retractable thanks to a coaxial spring -16-, which tends to displace it outwardly of the said drilled hole -8-, in such a way that its end does not intercept the duct -34-, means having been designed to displace the said pivot -15-, compressing the said spring - 16-, in a way that its end interferes the duct -34- and acts as insertion limiting stop of the pin -4- in the said duct -34-. The means to provoke a displacement of the pivot -15-comprise an offset with a regular profile bottom ending in a ramp -31- at the casing -12- internal face, the said offset remains facing like a sliding track with the external end of the said pivot -15-, in a way that the interposition of the pivot in the duct -34- occurs in coordination with the linear backward run of the casing - 12-. As stated above in figures 6 to 8, alternative means have been represented, on the ground of the same principle of the invention, to provoke a displacement of the pivot - 15- comprising a set of levers, -26-, -27-, -28- driven by a pneumatic cylinder -29- and coupled thereto by the part - 30- controlled by a sequentially programmed electronic device, to actuate , through an electrovalve the cylinder - 29- and to displace the pivot -15- to a position of interception of the duct -34-, at any moment, and regardless the casing -12- movement. With that it is achieved that the pistol may work in any orientation and namely in upright position, upwardly riveted, avoiding that the pin -4- could accidentally penetrate within the duct - 34-, without this later being intercepted by the pivot -15. The method to feed rivets according to above explanation comprises following phases: conveyance of a blind rivet comprising a rivet head portion or body (2), a flange or washer -3- and a stem or pin -4-, removable, in a predetermined position within the recess -32- of the casing -12- enclosing the front end of the gripping mechanism -25- of the riveting tool; telescopic linear displacement, of predetermined length, of the said casing -12- coaxially and approaching the end of the said gripping mechanism -25-, to place the pin -4-, of the rivet within the central axial duct -34- of the said mechanism -25-; obturation of the axial duct -34- of the gripping mechanism forming a penetration stop of the said pin in the said duct, in coordination with the displacement of the casing -12- or independently thereof, at any time of the cycle, to oblige the portions -2- and -3- of the rivet to protrude from the said casing -12- by a distal end, provided with elastic collets -1-; evacuation of the pin detached from the rivet after riveting, performed according to conventional art, by the riveting tool or pistol to which the device is applied, through the duct -34- of the gripping mechanism and an axial canal -9- which is connected with an evacuation area located far from the riveting tool. feeding of a new rivet which remains retained against the front external wall of the riveting tool, until the casing -12- returns to its initial feeding position, of maximum remote place with respect to the gripping mechanism -25-, a moment in which, as a passageway through the manifold -5- lateral to the casing -12- becomes free, the rivet has access to the recess -32- impelled by compressed air. The last mentioned step, guarantees that the rivet has access to the recess -32- at low speed, because of the short distance to run from the bottom of the manifold --5-, where it has been impelled by pressurized air through the tube -35-, avoiding this way rebounds and in general incorrect positioning, as those which may be produced in the event of above mentioned patent US 4027520.

Claims: Device for a front automatic rivet feeding of a riveting machine particularly applicable to the positioning of blind rivets formed by a rivet body or head portion (2), a flange or washer (3) and a removable pin or stem (4), in a riveting machine such as a fluid dynamic riveting pistol (10), with a section of head which embodies a chuck (17) which comprises a gripping mechanism (25) designed for holding the pin (4) or stem of the rivet positioned within thereof, and some fluid dynamic cylinders to close said gripping mechanism and to apply a tensile stress with the purpose of deforming the rivet head portion (2) until detaching the said pin (4), which is evacuated through a duct (9) axial to said head section, the device also comprising means for an individual feeding of the said rivets, such as a pneumatic conveyance, at a predetermined position, toward the said riveting pistol, characterized in that it comprises: a) a casing as sleeve (12), which surrounds the front end of the gripping mechanism (25) of the riveting pistol, in coaxial arrangement, the said casing (12) internally defining a recess (32) and is finished at its front section by a collet (1) with a central hole (33) which, in its internal face, has a conic profile; b) a manifold (5) in a side of the casing (12) defining a passageway to supply rivets to the interior of the said recess (32), supplied by the said conveyance means through a duct (35), coupled to the said manifold (5). c) a nozzle (13), exchangeable, placed in superposition and alignment with the end of the duct (34) central to the gripping mechanism (25), the said nozzle having a conical profile oriented facing the distal end, provided with the said collet (1), of the casing (12); d) means to displace a predetermined distance said casing, lengthwise and telescopically with respect to the end of the chuck, co-aligned with the central duct (34) of the gripping mechanism (25), to place the rivet pin (4), guided by the nozzle (13) within the said duct (34); e) means to intercept the axial duct (34) of the gripping mechanism (25) constituting a stop limiting the insertion for the rivet pin (4), determining when ending the displacement of the said casing (12) a positioning of the said rivet such that the flange (3) thereof protrudes from the elastic collets (1) and the rivet head portion (2) remains outside the set ready for its insertion in a hole of a workpiece. Device according to claim 1, characterized in that said manifold (5) supplying the rivets, has an inclined orientation with respect to the lengthwise axis of the chamber (32) co-aligned with the duct (34) of the gripping mechanisms (25) and to said manifold (5) a flexible duct (35) to feed the rivets is connected, the manifold (5) remaining in opposition with respect to the riveting pistol (10) handle or to a supporting element of the riveting tool involved. Device according to claim 1, characterized in that the means for displacing the casing (12, telescopically with respect to the chuck of the riveting pistol, comprise external pneumatic cylinders (21) sustained on a support (22) secured to the riveting pistol (10) body, and which stems (14), which are oriented in parallelism to the axis of the duct (34), are connected by their ends through some appendages (19), to the casing (12). Device according to claim 1, characterized in that the collet (1), comprises a plurality of collet fingers (36) in radial arrangement around an axis coaxial with the central duct (34), of the gripping mechanism (25), hinged by their back end, which may be opened forming a front central opening having a diameter slightly larger than the washer (3) and body (2) of the rivet, or may remain closed defining a central front hole (33), suitable to hold the pin (4) of the same rivet, an external elastic ring (37) having been designed which tends to keep the said fingers (36) in closed position, and a collar (39) attached to the casing (12) which encloses the said back ends of the fingers (36), with a small play. Device, according to claim 4, characterized in that the articulation of the fingers (36) of the collet comprises an offset (38) of the said fingers back end, which is supported on an annular element (41) socketed in an annular groove (42) of the casing (12) external surface. Device, according to claim 1, characterized in that a sleeve (24) connects the casing (12) to the body (10) front end of the riveting pistol, acting as guard. Device, according to claim 1, characterized in that the means to intercept the duct (34) during the displacement of the casing (12) in order to place the rivet pin (4) within the said duct, comprises a pivot (15) inserted in a drilled hole (8) lateral to the duct (34) which flows at predetermined distance of the front end of the said duct, said pivot (15) being retractable thanks to a coaxial spring (16), which tends to displace it outwardly of said drilled hole (8), in such a way that its end does not intercept the duct (34), having been designed means to displace said pivot (15), compressing said spring (16), so that its end interferes the duct (34) and acts as insertion limiting stop of the pin (4) in the said duct (34). Device, according to claim 7, characterized in that the means to provoke a displacement of the pivot (15) comprise an offset with a regular profile bottom ending in a ramp (31) at the casing (12) internal face, the said offset remaining facing like a sliding track with the external end of the said pivot (15), so that the interposition of the pivot in the duct (34) occurs in coordination with the linear backward run of the casing (12). Device, according to claim 7, characterized in that the means to cause a displacement of the pivot (15) comprise a set of levers, (26), (27), (28) driven by a pneumatic cylinder (29) controlled by a sequentially programmed electronic device, to actuate, through an electrovalve the cylinder (29) and to displace the pivot (15) to a position of interception of the duct (34), at any moment, and regardless the casing (12) movement. Method for a front automatic rivet feeding to a riveting machine characterized in that it comprises following phases: a) conveyance of a blind rivet comprising a rivet head portion or body (2), a flange or washer (3) and a stem or pin (4), removable, in a predetermined position within the recess (32) of a casing (12) enclosing the front end of a gripping mechanism (25) of a riveting tool; b) telescopic linear displacement, of predetermined length, of said casing (12) coaxially and approaching the end of the said gripping mechanism (25), to place the pin (4), of the rivet within the central axial duct (34) of said mechanism (25); c) obturation of the axial duct (34) of the gripping mechanism forming a penetration stop of the said pin in the said duct, in coordination with the displacement of the casing (12) or independently thereof, at any time of the cycle, to compel the portions (2) and (3) of the rivet to protrude from said casing (12) by a distal end, provided with elastic collets (1); d) evacuation of the pin detached from the rivet after riveting, through an axial duct (34) of the gripping mechanism and an axial canal (9) which is connected with an evacuation area located far from the riveting tool. e) feeding of a new rivet which remains retained against the front external wall of the riveting tool, until the casing (12) returns to its initial feeding position, of maximum remote place with respect to the gripping mechanism (25), a moment in which, as a passageway through the manifold (5) lateral to the casing (12) becomes free, the rivet has access to the recess (32) impelled by compressed air.

Inventors: SANCHO GATELL ANTONIO, SORRIBES GRANEL LUIS, SANCHO GATELL, ANTONIO, SORRIBES GRANEL, LUIS
Applicants: CANVIBLOC SL, CANVIBLOC, S.L.
Application year: 1993
Main classification: B21J15
IPC codes: B21J15