US3359580A - Method for producing shaped-head screws and tool for carrying out the method - Google Patents

Description

Dec. 26, 1967 Filed July 19, 1965 Fig. la

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M. OSMAN ET AL METHOD FOR PRODUCING SHAPED-HEAD SCREWS AND TOOL FOR CARRYING OUT THE METHOD Fig. la

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INVENTORS M/i ms 0841/7/14 4/vmi. Wamky r-JW- Z ATTORNEYS Dec. 26, 1967 QSMAN ET AL 3,359, 580

METHOD FOR PRODUCING SHAPED-HEAD SCREWS AND TOOL FOR CARRYING OUT THE METHOD Filed July 19, 1965 5 Sheets-Sheet 2 Fig. I

IN VENTORS Mews 5/144, A'A/TAA 4 0/1 A TTORNEYS Dec. 26, 1967 OSMAN ET AL 3,359,580

METHOD FOR PRODUCING SHAPED-HEAD SCREWS AND TOOL FOR CARRYING OUT THE] METHOD Filed July 19, 1965 3 Sheets-Sheet 3 IN VE N TORS A/M Zos 0.94444 4/1/74; Mal 4x; '/.srm'/v (saw/ma umsfeewm 44w fie-leave 4/525/ A TTORNEYS United States Patent 3,359,580 METHOD FOR PRODUCING SHAPED-HEAD SCREWS AND TOOL FOR CARRYING OUT THE METHOD Mikls Osman, Antal Novalr, Istvan Csiimiir, Lajos Fernbach, and Fereuc Mezei, Budapest, Hungary, assiguors to Csavaraugyar, Budapest, Hungary Filed July 19, 1965, Ser. No. 473,044 1 Claim. (Ci. -2)

ABSTRACT OF THE DISCLOSURE A tool for producing shaped-head screws in a single working step by means of upsetting and extrusion consists of a die and a heading block. The latter is supported by a die holder and said die is supported by a counter frame. The heading block comprises an upsetting mandrel arranged for sliding movements therein whichin its home position-encloses a closed forming cavity with the heading block and the die. The heading block is arranged in the die holder for sliding movements in the direction of the movements of the upsetting mandrel, and is biased by a spring against such displacements.

The improvement consists in the employment of an ejecting stop in the counter frame arranged for abutting against and pushing back said heading block with respect to said upsetting mandrel when the die holder is in a transversely displaced position. Thereby, a workpiece in the forming cavity will be knocked out by means of the upsetting mandrel.

This invention relates to a method for producing shaped-head screws and to the tool for carrying out said method.

It is known that shaped-head screws have largely been produced up to now in a so-called two-step cold upsetting press. In such automatic equipment sections of predetermined length are cut oil the bobbin storing the material of the screws, and these sections are placed in dies. Here, the cut workpiece is upset by means of the preliminary upsetting device arranged in the centreline of the die. After completion of the upsetting operation the preliminary upsetting device is withdrawn from the working space and its place is taken by a bolt header which develops the pre-upset part of the workpiece to a head, i.e. the workpiece is headed. The cylindrical-head semiproduct formed in this Way is placed by the automatic machine onto a conveyor means which then feeds the screws provided with cylindrical heads into another automatic machine, i.e. into the trimming machine. Here, the head of the cylindrical-head screw is cut to hexagon by shearing. The obtained hexagonal screw is conveyed into a storage vessel whence the screws are forwarded to heat treatment (annealing) since due to the extensive coldworking accompanying the shearing action the head has become brittle and may break in use. After the completion of this operation the semi-product is led to another automatic machine which rolls a thread into the shank of the screw.

This known process requires three different automatic machines and heat treatment for processing the screws; hence, it has a relatively high space requirement and it is time and work consuming, thus rendering the manufacturing process relatively costly.

In order to eliminate these difiiculties the use of a four-stage extruding press has already been suggested, which produces hexagonal screws by means of plastic cold-working. By this method first the shank is extruded and then the head is upset. The advantage of this process Patented Dec. 26, 1967 is that the heat treatment is omitted and screws of uniform strength may be produced in which therefore the strength of the shank and the head is practically the same; the equipment for carrying out the process is, however, expensive and the conventional two-step cold upsetting press may not be transformed for applying this method.

It is the object of the invention to eliminate the above difficulties and to develop a tool for producing shapedhead screws which renders the known two-step cold upsetting press suitable for producing screws without shearing and heat treatment. The invention is based on the recognition that by combining upsetting with extrusion, the rod-shaped raw material may be provided with hexagonal heads in one working step, without dislocation and without any considerable difference in the strength i of the head and that of the shank which has been provided with a thread through thread rolling. This is achieved in such a manner that the work-piece is upset in the same working process and in the same working position in a closed die cavity up to the establishment of a contact with the wall of the cavity, and then extruded up to the complete filling of the cavity. It has been established in the course of experiments that the screws produced by this process are practically equivalent to those produced in the four-stage cross-feed extruding presses, since no considerable difference exists between the strength of their heads and that of their shanks, i.e. they might be considered as of uniform strength. The shape of the head also corresponds to the standard requirements. In addition, the method according to the invention may be effected also with two-step cold extruding presses after slight modification, which means that the introduction of the invention requires hardly any investment. The heat-treatment of the screws may also be omitted, i.e. no annealing furnace is necessary and the labour and fuel costs arising from heat treatment can be saved.

The modification involves the use of a tool consisting of a die and header in which according to the invention an upsetting mandrel is led through the header and encloses, together with the header and die, a closed forming cavity. When the upsetting mandrel starts to upset the workpiece in this enclosed space, the workpiece is upset until it gets in contact with the wall of the cavity. With the progress of the upsetting action the contact between the workpiece and the cavity wall becomes more and more complete and upsetting is replaced by extrusion. When the workpiece is already in contact with the cavity wall, the material merely flows under the eifect of the further displacement of the upsetting mandrel, thus filling the cavity completely. This also means that it assumes the form of the cavity. If, therefore, the cavity has the form of a hexagonal screw head, the workpiece will have a head of similar shape, on completion of upsetting and extrusion.

In order to enable the invention to be more readily understood, the tool according to the invention is shown in the accompanying drawing in connection with the manufacture of hexagonal screws.

FIGS. 10, 1b, 1c, 1d and 1f show end views of various phases of the conventional method for producing hexagonal screws;

FIGS. la, lb, 1c, 1d and 1 show the correspondin g side elevations;

FIG. 1e shows the scrap resulting from the trimming operation in the above figures;

FIGS. 2a, 2b, 2c and 2e show end views of various phases of producing hexagonal screws in accordance with the present invention;

FIGS. 2a, 2b, 2c and 22 show the corresponding side elevational views;

FIG. 2d is a fragmentary cross-sectional view of the structure shown in FIG. 20'; and

FIGS. 3 to 5 represent the longitudinal section of the embodiment shown by way of example of the tool required for the process according to the invention, in three different working positions.

As can be seen in FIGURES la to 1 the starting material of the conventional process is a rod-shaped workpiece 11 which is cut up to section I, having a weight greater by the weight of the chips than that of the completed screw (FIG. la). The cut-up workpiece 11 is preupset, so that the section of length 1 takes the shape 11a (FIG. lb). The section 11a of the pre-upset workpiece is formed to a circular head 11b (FIG. lc) during the headupsetting working phase. Now, the forming of the cylindrical heading to a hexagonal head 11c follows. The head of the screw 11, represented in FIG. as a semi-product, is pulledthrough an annular die corresponding to the hexagonal head, which shears the excess parts. Thus, the head 11c to be seen in FIG. 1a is completed. The scraps 11d resulting from the trimming may be seen in FIG. 12 in top view. Then, the shank of the workpiece 11 having I head 110 is provided with a thread lle in the manner known by itself, through thread rolling (FIG. 1 It is thus obvious that the conventional process consists of cutting up, preliminary upsetting, head upsetting, trimming or shearing and of thread rolling, i.e. of five working phases and during the process, the scraps 11d to be seen in FIG. 12 occur, the material of which shall be taken into account when determining the size of the section of length l, for cutting-up the workpiece 11.

The work phases according to the invention are shown in FIGS. 2a to 2e. When comparing the two groups of figures, it is immediately apparent that with the method according to the invention the number of working phases is reduced by one since the trimming (FIG. la) is omitted. At the same time no scraps 11d according to FIG. 1e occur. Due to the absence of scraps, the part I intended for the development of the head of the cut-up workpiece 12 may also be smaller than I. With the method according to the invention, therefore, not only does production become simpler due to the reduction of number of working phases but also the raw material demand is reduced due to the absence of scraps. Thus, the method according to the invention means a considerable improvement in the fields of both technology and economy, as compared to the conventional method.

For carrying out the method according to the invention, the tool shown in FIGS. 3 to 5 may be used. The main parts of this tool are a heading block 15 and a die 16, the former being arranged in a die holder or ram 17 of the two-step cold upsetting press known by itself, while the latter is arranged in a counterframe 18. In the headin-g block 15 an upsetting mandrel 20 is led which encloses in its home position, together with the heading block 15 and die 16, a closed forming cavity 21. In the ram 2 the heading block 15 is arranged sliding against the preliminary header, namely against a spring 22 in case of the embodiment shown by way of example, in the direction of displacement 23 of the upsetting mandrel 20'. In the counterframe 18a stop 25 is used as ejector means which loads the heading block 15 against the spring 22 in the position of ram 2 deflected transversely to the direction of upsetting 23, as shown in FIG. 5.

In the die 16 an ejector pin 24 is led in a manner known by itself which acts in the sense 26 opposite to the arrow 23.

The embodiment of the two-step cold upsetting press according to the invention, shown by way of example, operates as follows:

Pro-upsetting occurs in the position of the die shown in FIG. 5 in a manner known in itself, hence, its details are not described here.

In the working position shown in FIG. 3 the pre-upsetting is completed and the screw 12 as a semi-product having a pre-upset head 12a takes its place in the forming cavity 21. The ram 17 advances until the heading block 15 bears against the front side of the die 15, thus developing the enclosed forming cavity 21 around the pre-upset head 12a.

As the ram 17 moves off further in the direction of the arrow 23, the upsetting mandrel 20 gets in contact with the pre-upset head 12a and begins its upsetting. Upsetting is continued until the pre-upset head 12a gets in contact with the wall of the forming cavity 21. Wherever, due to the resistance of the wall, the material does not yield to the upsetting effect, it begins to flow and thereby the subsequent filling out with material of that part. of the forming cavity surrounded by a hexahedron begins. In the meantime the spring 22, unable to deflect in the direction opposite to the arrow 23, becomes more and more tensioned and increases the force by which the heading block 15 is pressed against the die 16.

The end of this working phase is to be seen in FIG. 4. The upsetting mandrel 20 has travelled forward to such an extent that the forming cavity 21 has been narrowed to the part corresponding to the hexagonal screw head and this part was entirely filled with the pre-upset head 12a. Thus, the hexagonal head 12b of the screw 12 was formed.

Then, the ram 17 moves off in the direction 26 opposite to the arrow 23, that is, it opens the forming cavity 21. If in such a case the head 12b does not adhere to the forming cavity 21 but remains in the die 16, the ejector pin 24 led in the die ejects the screw 12 in the manner known by itself.

If, however, the screw remains with its head 12!; stuck in the forming cavity 21, the ram 17 moving in the direction of the arrow 26 carries along the screw 12, 12b and may cause breakdown (machine break) in the following working cycle. The stop 25 has the purpose of preventing its occurrence. When the ram 17 advances again in the direction of the arrow 23, but in a position transversely deflected to the direction 23, the front face of the heading block 15 impacts on the stop 25 which presses back the heading block 15 against the spring 22. The upsetting mandrel 20, however, leaning rigidly against the ram 17, cannot follow the displacement in the direction of the arrow 26 of the heading block 15, that is, it remains in its position and ejects the screw 12 retained by its head 12]) in the forming cavity 21 in the outlet groove 27 of the counterframe 18 by the pressure exerted onto the head 12b. The screw 12, 12b falls from here onto the conveyor which forwards the screws provided with regular heads into the thread rolling machine in a manner known in itself.

Simultaneously with the ejection, the upsetting of the next workpiece is carried out in a manner known in itself, as can be seen in the top part of FIG. 5.

It may occur that in the final upsetting operation of the head 12a, the burr 12c indicated in distorted scale in FIGS. 2c and 2d develops on the head 1%. For its removal the thread rolling machine is provided with a cutting tool which parts off the burr 12c during the thread rolling operation. Thus the removal of the burr does not require a separate working cycle.

The invention has been described above in connection with the production of screws provided with hexagonal heads. It is obvious that instead of a hexagonal head, screws with heads of any other shape may be produced without departing from the basic idea according to the invention. The root of the matter is to carry out the forming in a closed cavity, that is to extrude the material after being upset.

What we claim is:

A tool with die and heading block for producing shapedhead screws in a single working step by means of upsetting and extrusion, having, in combination, a die holder for supporting said heading block, a counterframe for supporting said die, and an upsetting mandrel arranged for sliding movements in said heading block, said mandrel in its home position enclosing with said heading block and said die a closed forming cavity, said heading block being arranged in said die holder for sliding movements in the direction of displacements of said upsetting mandrel and biased by a spring means against such displacements, said counterframe being provided with an ejecting stop arranged for abutting against and pushing back said heading block with respect to said upsetting mandrel in transversely displaced position of said die holder so as to cause a workpiece to be knocked out from said forming cavity by means of said upsetting mandrel.

References Cited UNITED STATES PATENTS LEONIDAS VLACHOS, Primary Examiner.

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