Improved extraction device associated with the extrusion pin in a machine for the production of wholly tubular rivets

Abstract

 An extraction device associated with the extrusion pin (11) in a machine for the production of wholly tubular rivets (10), wherein the extrusion pin (11) is driven to transla­te inside the frame of the machine inside a bore (30) pro­vided in a die (12), by an inner rod (19) lined-up with the extrusion pin (11) and driven by a first lever (21), where the inner rod (19) is coaxially located so as to slide inside a tubular rod (22), operatively driven in correspondence of the die (12) by a second lever (23), wherein in front of the tubular rod (22) an extraction sleeve (27) is located, which is provided with an inner, coaxial bore, so as to be able to receive the extrusion pin (11), and has an outer size equivalent to that of the bore (30) provided in the die (12).

Description

[0001] The present invention relates to an improved extraction device associated with the extrusion pin in a machine for the production of wholly tubular rivets.

[0002] In the machines for producing wholly tubular rivets, with the drive mechanism driving the extrusion pin, the die and the block holding the rivet forming punches, a device is generally associated for extracting the finished rivet off from the extrusion pin.

[0003] Such a device, which is directly driven, by means of a cam transmission means, by the same shaft which drives the extrusion pin, usually ends with a fork-shaped element which clamps the rivet, while this is still inserted on the extrusion pin made come off the die. A subsequent backwards motion of the extrusion pin disengages the rivet and leaves it on the fork-shaped element which then discharges it in a known way, or makes it drop inside a collecting container.

[0004] The separation, or extraction of the wholly tubular rivet from the extrusion pin by means of such a fork-­shaped element, although is simple, determines the need for a perfect correlation and synchronism between the various movements and positionings and the various components. In fact, in the lack of such a perfect correlation and synchronism, either interferences between the fork-shaped element and the extrusion pin, or difficulties in disengaging the so-formed wholly tubular rivet from the same pin may arise, with possible damages to the movable elements, or even to the die.

[0005] One should furthermore consider that the need for a fork-shaped extraction element, as well as for all of the relevant kinematic transmissions and lever systems connected with it, render more complex and delicate, and, consequently, expensive, the machine, as regards to its setup.

[0006] The purpose of the present finding is to solve the above problems, possibly getting rid of the fork-shaped extraction element, so as to simplify the machine and rendering it more reliable.

[0007] This purpose according to the present invention is achieved by providing an improved extraction device associated with the extrusion pin in a machine for the production of wholly tubular rivets, wherein said extrusion pin is driven to translate inside the frame of the machine inside a bore provided in a die, by an inner rod lined-up with said extrusion pin and driven by a first lever, characterized in that said inner rod is coaxially located so as to slide inside a tubular rod, operatively driven in correspondence of said die by a second lever, in front said tubular rod an extraction sleeve being located, which is provided with an inner, coaxial bore, so as to be able to receive said extrusion pin, and has an outer size equivalent to that of said bore provided in said die.

[0008] The structural and functional characteristics and the advantages of a device according to the present invention will be better understood from the following exemplifying, non-limitative disclosure, as referred to the relevant schematic drawings, wherein:

Figure 1 shows a partially sectional longitudinal view of a device according to the present invention, and

Figure 2 shows a sectional view of a magnified detail of Figure 1, in a different operating step.

[0009] Referring to the Figures, in a machine (not shown) for the production of wholly tubular rivets 10, an improved extraction device according to the present invention, associated with an extrusion pin 11 and a die 12, is provided.

[0010] A frame or bedplate 13, partially shown, supports the guide unit for the extrusion pin 11. More precisely, on one side of the bedplate a means for returning backwards the extrusion pin 11 is fastened, which is constituted by a couple of hollow cylindrical elements 14, which are fastened to the same bedplate, and are positioned parallel to the direction of movement of the pin 11, inside which return springs 15 are contained, which urge rods 16 sliding inside them, and supporting at their end a crossbeam 17, to return backwards.

[0011] Inside a bore 20 through said crossbeam 17 an enlarged end head 18 of an inner through rod 19 is slidingly housed and is constrained to stop against said crossbeam. The other end of the rod 19 is linked to the extrusion pin 11.

[0012] A first drive lever 21 is provided in order to operatively drive the inner rod 19. The lever 21 is driven in a way known from the prior art, and not shown, by means of a kinematic transmission acting on the cams of a drive shaft.

[0013] In its turn, the inner rod 19 is coaxially slidable inside a tubular rod 22 driven, and controlled to translate by means of a second drive lever 23, which engages inside planar, recessed surfaces 24 of the tubular rod 22, thus preventing this latter from rotating during its translation.

[0014] The tubular rod 22 is externally and at least partially surrounded by bushings 25 up to the wall of a die-holder block 26, inside which the die 12 is located. Opposite to said tubular rod 22 an extraction sleeve 27 is positioned, which is so shaped and flanged in 28, at least in correspondence of its end facing the tubular rod 22, so as to come into engagement with it. The extraction sleeve 27, which, when moving relatively to the die 12, slides inside a guide spacer 29 integral with the die-­holder block 26, and coaxial with a bore of said die 12, has, at its narrower front portion, an outer size which is equivalent to that of bore 30.

[0015] The extraction sleeve 27 is provided with an inner channel, in such a way as to enable the extrusion pin 11 to run through, and translate inside, it.

[0016] As shown in the Figures, the extrusion pin 11 is constrained to the inner rod 19 by means of a cup-shaped container element 31, provided with an axial bore through its basis, and screwed down by means of complementary screw-threads 32 respectively provided on the inner wall of the cup-shaped container 31 and on the outer surface of a shorter-diameter portion 33 of the inner rod 19.

[0017] A device according to the instant invention in a machine for the production of wholly tubular rivets operates as follows.

[0018] Once that a length of material is located inside the bore 30 of the die 12 and that in a known way, e.g., by means of two different operating steps by means of an equal number of punches, a wholly tubular rivet is formed, removing it from the extrusion pin 11, which is in the position shown in Figure 1, is necessary.

[0019] To this end, the second drive lever 23 is moved in the direction as shown by the arrow 34, making the tubular rod 22, which is integral with it, advance. Such an advancement also causes the extraction sleeve 27 to advance in the same direction. The extraction sleeve 27 obliges, by means of its smaller-diameter front portion, the formed rived 10 to come off the bore 30 of the die 12 (Figure 2).

[0020] In this way, the rivet 10 is ejected and free, and the first lever 21 can be thus disengaged from the enlarged head 18, so as to cause the extrusion pin 11 to return back to its initial position, by being returned backwards by the springs 15.

[0021] The second drive lever 23 is then moved backwards, by moving it to a direction opposite to that shown by the arrow 34, and the subsequent introduction of a new length of material inside the bore 30 of the die 12 makes the extraction sleeve 27 move backwards, up to stop against the end of the tubular rod 22.

[0022] In this way, by means of a device according to the present invention, the fork-shaped element which is present in the prior art is completely got rid of, and the occurrence of any possible interferences between it and the finished rivet leaving the die supported by the extrusion pin 11, or the same extrusion pin, is prevented.

[0023] Furthermore, by means of this device the certainty is achieved that the wholly tubular rivet, once finished, is removed off from the die and is disengaged from the extrusion pin.

Claims

1. Improved extraction device associated with the extrusion pin in a machine for the production of wholly tubular rivets, wherein said extrusion pin is driven to translate inside the frame of the machine inside a bore provided in a die, by an inner rod lined-up with said extrusion pin and driven by a first lever, characterized in that said inner rod is coaxially located so as to slide inside a tubular rod, operatively driven in correspondence of said die by a second lever, in front of said tubular rod an extraction sleeve being located, which is provided with an inner, coaxial bore, so as to be able to receive said extrusion pin, and has an outer size equivalent to that of said bore provided in said die.

2. Device according to claim 1, characterized in that said extraction sleeve comprises, on one side, a flanged end portion to come to stop against said tubular rod, and on the other side, a portion having said outer size equivalent to that of said bore of said die, with said flanged end portion being slidable inside a spacer coaxially lined-up with said bore of said die.

3. Device according to claim 1, characterized in that said tubular rod slides on bushings integral with said frame, and has planar surfaces with said second drive lever, suitable for preventing said tubular rod from rotating relatively to said second driver lever.

4. Device according to claim 1, characterized in that in correspondence of said first lever, said inner rod is provided with an enlarged end, which is integral with an elastic means for returning backwards said extrusion pin.

5. Device according to claim 1, characterized in that said extrusion pin is constrained to said inner rod by means of a cup-shaped container element having an axial bore through its basis screwed down, by means of a screw-thread provided on its inner wall, to an end of said inner rod, which is provided with a complementary screw-thread on its outer surface.

Drawing