Abstract:
The invention relates to a forging apparatus used for forging a heated blank ( 24   a ), which in a pre-treated operation has been given a volume essentially corresponding to that of the final product, said forging apparatus comprising upper and lower die parts ( 2, 16 ) arranged to be brought together into abutting relationship and having contacting surfaces ( 42   a,    18   b ) extending transversely of the direction of movement of the die parts, whereby when the contacting surfaces ( 42   a,    18   b ) are pressed together and brought into contact with one another as result of pressure exerted thereon, the blank is shaped in conformity with a die cavity defined with precision by the die parts ( 2, 16 ). The configuration of the forged component then essentially agrees with that of the desired finished component, i.e. no or at least only minimum post-treatment is required. Said contacting surfaces ( 42   a,    18   b ) extending transversely of the direction of movement of the die parts are arranged to have no contact with the die cavity ( 25 ) during the forging operation.

Description:
TECHNICAL FIELD 
     The invention relates to a pressing die used for forging a heated blank, which in a pre-treatment operation has been given a volume essentially corresponding to that of the final product. The forging apparatus comprises upper and lower die parts arranged to be displaced towards each other and having contacting surfaces extending transversely of the direction of movement of the die parts, whereby when the contacting surfaces are pressed together and brought into contact with one another as a result of pressure exerted on said parts, the blank is shaped in conformity with a die cavity defined with precision by the die parts. The configuration of the thus forged component then essentially agrees with that of the desired finished component, i.e. no or at least only minimum post-treatment is required. 
     TECHNICAL BACKGROUND 
     A device of the kind described above is previously known from U.S. Pat. No. 4,015,461. The forging apparatus described therein comprises two parts which are pressed against one another until the surfaces thereon that extend transversely of the direction of pressure exertion are brought into contact with one another. A die cavity having a carefully defined volume is thus defined, and the blank to be forged has been pre-treated so as to adopt that volume for the purpose of eliminating the need for post-treatments. 
     One problem encountered with this kind of forging dies is that during the forcing operation, material might be forced out from between the contacting surfaces, with the result that so called burrs may form on the component, making the undesired post-treatment necessary after all. At worst, the amount of material being expelled from between the contacting surfaces is of such a magnitude as making completion of the forging operation impossible. 
     Another problem encountered with forging dies of the kind outlined above is that they cannot be used for forging components having a more complex configuration, such as a cylinder having outwardly projecting fins or other protrusions thereon. It would be impossible to remove components of such a shape from a die of this kind. 
     It should be noted that by the expression “cylinder” as used in this context is intended a surface obtained by moving a straight line in parallel along a curve, such as an ellipse or a circle. 
     SUMMARY OF THE INVENTION 
     A first object of the present invention is to provide a forging apparatus, which is adapted satisfactorily to eliminate or to reduce to a minimum the need of post-treatment of the forged component. 
     A second object of the present invention is to provide a forging apparatus to be used to forge components having a more complex configuration. 
     A third object of the present invention is to provide a forging apparatus making an efficient manufacturing process possible. 
     The first one of these objects is achieved in accordance with the teachings of the invention in that such contacting surfaces that extend transversely of the direction of movement of the die parts and are mutually movable during the forging operation have no contact with the die cavity during the forging operation. This means that the material of the blank confined inside the die cavity during the forging operation cannot be squeezed out from between the contacting surfaces. 
     Furthermore, the forging apparatus preferably comprises a plurality of die members arranged to be displaced towards and away from the die cavity center and to be locked in their bought-together position in which they define the die cavity laterally. The fact that the members that define the die cavity radially, that is towards and away from the die cavity center, are arranged for radial movement means that during the forging operation the component is allowed to completely fill voids in the die members, and to thus form components having a comparatively complex shape. After the forging operation, the die members may be moved apart, thus allowing removal of the forged component. 
     Power-exerting means preferably are interconnected with the die members and arranged to move said members towards and away from the die center. Said power-exerting means are able to effect the pressing-together of the die members prior to the start of the forging operation, and to thereafter move said means apart after completion of the forging operation. 
     Preferably, the die members may be locked by a locking ring. The locking ring ensures even distribution of the radial pressure around the circumference of the entire die cavity in the course of the forging operation. 
     Preferably, the die parts may be displaced towards one another in a two-step operation, that is a first step, during which the locking ring is brought into contact with the die members, locking them in their brought-together position, and a second step, during which the blank is shaped in conformity with the die cavity, the configuration of which is precision defined by the die parts. This arrangement provides for a smooth forging process, wherein locking of the die cavity and the forging operation are effected in one and the same movement. 
     In accordance with a special embodiment of the die the die parts are arranged to be vertically spring-actuated. In consequence of this arrangement, the upper and the lower ends of the blank may be deformed simultaneously. This possibility is particularly advantageous for instance when fins or flanges are to be formed at the upper and the lower rim of the blank, or when multi-arm components, such as for instance cross members for universal joints are to be manufactured. 
     Other characterizing features of the invention will be apparent from the appended claims and will be described in the ensuring description of three presently preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     Three embodiments of the forging apparatus in accordance with the invention will be described in the following with reference to the accompanying drawings, wherein 
     FIG. 1 a  is a cross-sectional view of a first embodiment of the die in accordance with the invention, the die being shown in the initial position, and with a blank being inserted between the die members. 
     FIG. 1 b  is a cross-sectional view of a first embodiment of the die in accordance with the invention, the die being shown in the final position, and the blank having been shaped into the desired configuration. 
     FIG. 2 is a view from above of the die jaws incorporated in the die in accordance with FIGS. 1 a,    1   b.    
     FIG. 3 shows a component shaped by the die in accordance with FIGS. 1 a ,  1   b.    
     FIG. 4 a  is a cross-sectional view of a second embodiment of the die in accordance with the invention, the die being shown in the initial position, and with a blank positioned between the die members. 
     FIG. 4 b  is a cross-sectional view of a second embodiment of the die in accordance with the invention, the die being shown in the final position and the blank having been shaped into the desired configuration. 
     FIG. 5 shows a component shaped by means of the die in accordance with FIGS. 4 a ,  4   b,    
     FIG. 6 is an exploded view of the die in accordance with FIGS. 4 a ,  4   b.    
     FIG. 7 a  is a cross-sectional view of a third embodiment of the die in accordance with the invention, the die being shown in the initial positoin, and with a blank positioned between the die members. 
     FIG. 7 b  is a cross-sectional view of a third embodiment of the die in accordance with the invention, the die being shown in the final position and the blank having been shaped into the desired configuration. 
     FIG. 8 is a view from above showing the die jaws incorporated in the die in accordance with FIGS. 7 a ,  7   b , and 
     FIG. 9 shows a component shaped by means of the die in accordance with FIGS. 7 a ,  7   b.   
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 a,    1   b  illustrate a first embodiment of the forging apparatus in accordance with the invention, generally designated by reference numeral  1 . The lower die part  2  comprises a lower cylinder-shaped die holder  40 , which is fixedly mounted on the support  3 , preferably with the aid of a lower locking ring  4 , which grips a flange  5  formed at the lower edge of the die holder  40 . 
     An abutment member  6 , in this case essentially consisting of a cylinder, is arranged coaxially on the cylindrical die holder  40 . The inner diameter of the abutment member  6  essentially coincides with the inner diameter of the die holder  40 . An outwardly directed flange is formed at the lower edge of the cylindrical abutment member  6 . 
     An annular pad  7  formed with an external shoulder  7   a  is mounted around the abutment member in abutting relationship therewith, the inner diameter of said annular pad essentially agreeing with the external diameter of the abutment member  6 . The pad  7  is resiliently supported by the die holder  40 , preferably by means of a plurality of spring means  43 , whereby the pad  7 , in an unloaded condition, will be kept spaced from the die holder  40  but when exposed to a load of a predetermined magnitude, preferably exceeding  10  tons, the pad will be depressed into abutting relationship with an abutment face  42   a  formed between the pad  7  and the die holder  3 . Preferably, the abutment face  42   a  is the above-mentioned flange  42  formed at the lower edge of the abutment member. 
     The external shoulder  7   a  of the pad  7  supports an annular grooved disk  9  the upper face  9   a  of which is level with the upper face  7   b  of the pad and the inner face  9   b  of which abuts against the external face of the external shoulder  7   a  of the pad. 
     The grooved disk  9  is formed with a pluralilty of radially undercut grooves  10 , in the present case in the number of four grooves, which in accordance with the shown example run transversely across the upper face  9   a  of the entire grooved disk  9 . In each groove  10  a holder  11  is received for movement in said groove, the outer face  11   a  of the holder  11  sloping downwards and outwards away from the center of the die. Power-exerting means  12  are arranged at each holder for the purpose of displacing the holders  11  along the grooves  10 . A die jaw  13  is positioned interiorly of each holder and arranged in such a manner that the die jaws are pressed together when the power-exerting means  12  displace the holders inwards along the grooves  10 . Recesses  44  the shape of which corresponds to the desired appearance of the forged component  45  are formed on the inner face of the die jaws  13 . Each holder  11  and each die jaw  13  are configured as a sector of a ring, such that when pressed together they form two essentially continuous concentric rings, which may be designated a die ring  14  and a holder ring  15 , respectively (see FIG. 1 b ). The lower face  14   b  of the die ring  14  has a width radially that essentially equals the width of the upper face  7   b  of the pad. 
     In accordance with the first embodiment, the upper die part  16  of the forging apparatus  1  essentially consists of the vertically movable pressing head  17 , on which a punch  18  is mounted. In this case the punch  18  essentially consists of a cylinder, the inner diameter of which equals that of the abutment member  6 . The punch  18  is formed with an abutment face  18   b , allowing the punch  18  to be lowered into the die ring  14  until the abutment face  18   b  contacts the die ring  14 , in which position the lower face  18   a  of the punch is located below the upper face  14   a  of the die ring. 
     The punch likewise supports a thrust collar  19  arranged concentrically thereon, and a locking ring  20  is resiliently mounted on the collar, preferably by means of a number of spring means  21 , whereby the locking ring, in an unloaded condition, will be kept spaced from the thrust collar  19  but when exposed to a load of a predetermined magnitude, preferably exceeding 10 tons, the locking ring will be urged over a predetermined distance towards the thrust collar. The inner face  20   a  of the locking ring  20  slopes at such an angle that its inclination corresponds to that of the outer face  11   a  of the holders  11 , whereby when the locking ring  20  is being pressed downwards over the holder  11 , the latter will be forced inwards, along the grooves  10 , and consequently will press the die jaws  13  together. 
     The contacting surface  11   a ,  20   a  between the holders  11  and the locking ring  20  preferably is self-locking, that is, the inclination is so adapted to the coefficient of friction that a lateral force will not generate a vertical force that might cause a movement in that direction. 
     Finally, the die in accordance with the first embodiment preferably comprises a preferably solid mandrel  22  of cylindrical shape, which is arranged to move upwards through the channel  23  formed by the die holder  40 , the abutment member  6 , the die laws  13  and the punch  18 . For instance means (not shown) to move the mandrel upwards are located underneath the support  3 . The external diameter of the mandrel  22  essentially equals that of the abutment member  6  and the internal diameter of the punch  18 , and the mandrel height at least equals that of the die jaws  13 . 
     The blank  24   a  to be pressed into shape by means of the die in accordance with the first embodiment is a cylinder which has been lathe-turned into predetermined dimensions, suitable to a tolerance of ±0.1 mm, preferably ±0.05 mm. The dimensions of the cylinder are such as to allow the mandrel to be introduced into a space  25 , which is delimited by the mandrel  35  and the die ring  14  laterally and by the abutment member  6  at the bottom. The blank  24   a  also is heated to at least 650° C., preferably to between 1200° C. and 1300° C. 
     In use of the forging apparatus, the mandrel  22  is moved upwards, through the die holder  40  and the abutment member  6  and is positioned level with the die jaws  13  and the holders  11 , whereupon the treated and heated blank  24   a  is applied on the mandrel  22 . The power-exerting means  12  urge the holders  11  inwards, along the grooves  10 , the holders pushing the die jaws  13  in front of themselves, whereby the above-mentioned die ring  14  is formed and retains the blank  24   a  in abutment against the mandrel  22 . The pressing head  17  is then lowered towards the support  3  in a two-step operation. 
     In the first step, the locking ring  20  is carried downwards, over the holders  11 , causing the die ring  14  to be pressed additionally together and to be locked in that position. In addition, the punch  18  is moved into contact with the blank  24   a.    
     In the second step, the punch  18  is forced downwards into the blank  24   a , deforming the latter, while at the same time the spring means  21 ,  43 , interposed between the die holder  40  and the pad  7  and between the thrust collar  19  and the locking  20 , respectively, are compressed. In consequence hereof, the blank is compressed vertically and fills out the recesses  44  formed in the die jaws, and eventually it adopts precisely the shape of the die cavity defined by the mandrel  22  and the die ring  14  radially and by the abutment member  6  and the mandrel  18  axially. 
     When the pressing head  17  reaches its lowermost position, it is returned to its original position, bringing along the locking ring  20 , which releases its grip on the holders  11  and the die jaws  13 . The holders are moved apart by the power-exerting means and the mandrel  22  is lowered, leaving the finished forged component  24   b ,  45  resting in an unconstrained condition on the abutment member  6 . 
     The finished component  24   b  (most clearly apparent from FIG. 3, bearing numeral reference  45 ), which issues from the forging apparatus in accordance with the embodiment shown in FIGS. 1 a ,  1   b , consists of an essentially cylindrical body  46  formed with one upper and one lower flange  47  and  48 , respectively. 
     FIGS. 4 a ,  4   b  illustrate a second embodiment of the forging apparatus in accordance with the invention, generally designated by numeral reference  101 . The lower die part  102  of the forging apparatus comprises a pad  107  having a cylindrical configuration and being securely mounted on the support  103 , preferably by means of a locking ring  104  which securely grips a flange  105  formed at the lower edge of the pad. At its top, the pad is provided with inner and outer shoulders,  50  and  107   a , respectively. 
     An abutment member  106 , in the present case essentially in the shape of a guide sleeve  106  configured as a cylinder, is arranged interiorly of the pad  107 . The upper rim of the guide sleeve advantageously is formed with an outwardly directed flange  51 , which rests on and fills the inner shoulder  50  of the pad. An ejector  52  delimits the die cavity at the bottom and is arranged to be moved from below, upwards through the guide sleeve  106 . For instance, means (not shown) could be provided underneath the support  103  to cause the ejector  52  to move upwards. 
     The outer shoulder  107   a  of the pad  107  supports an annular grooved disk  109  formed with a plurality of radial undercut grooves  110 , in the present case in the number of four, which grooves in accordance with the shown example run transversely across the upper face  209   a  of the entire grooved disk. The upper face  209   a  of the grooved disk, the upper face  107   b  of the pad, and the upper face  106   a  of the guide sleeve are level with one another and consequently jointly form a flat surface having a centrally located, vertical channel  123 . 
     Each groove  110  of the grooved disk  109  receives a holder  111  for movement therein, the outer face  111   a  of said holder  111  sloping in a direction downwards and outwards from the center of the die. A power-exerting means  112  is provided at each holder  111 , said means arranged to displace the holder  11  along the groove  110 . Interiorly of each holder  111  there is arranged a die jaw  113  arranged to press the die jaws  113  together as the holders  111  are moved inwards, along the grooves  110 . Each holder  111  and each die jaw  113  is configured as a sector of a ring, such that when pressed together they form two essentially continuous and concentric rings, which may be designated die ring  114  and holder ring  115 . In accordance with this embodiment, the die ring  114  is formed with an inwardly directed flange  54  which in the pressed-together position has an interior diameter which essentially equals the interior diameter of the guide sleeve  106 . 
     The upper die part of the forging apparatus in FIGS. 4-5 essentially consists of the vertically movable pressing head  117  to which the punch  118  is attached. In this case, the punch  118  is a cylinder having an essentially flat bottom face  118   a  and an internal diameter, which is smaller than the internal diameter of the guide sleeve  106 , and an external diameter, which essentially equals the interior diameter of die ring  114 . Furthermore, the punch  118  is formed with a shoulder  118   b , whereby the punch  118  may be lowered into the die ring  114 , until the abutment  118   b  abuts against the die ring  114 , in which position the lower face  118   a  of the punch  118  is spaced somewhat above the inwardly directed flange  54  of the die ring  114 . 
     The pressing head  117  likewise supports a solid, cylindrical mandrel  122 , which is vertically movable. The exterior diameter of the mandrel  122  essentially equals the interior diameter of the punch  118 . 
     The pressing head  117  likewise supports a thrust collar  119  arranged concentrically with the punch  118 , and the locking ring  120  is resiliently mounted on the collar, preferably by means of a number of spring means  121 , whereby the locking ring  120 , in an unloaded condition, will be kept spaced from the thrust collar  119  but when exposed to a load of a predetermined magnitude, preferably exceeding 10 tons, the locking ring will be urged over a predetermined distance towards the thrust collar  119 . The inner face  120   a  of the locking ring  120  slopes at such an angle that its inclination corresponds to that of the outer face of the holders  111 , whereby when the locking ring  120  is being pressed downwards over the holders  111 , the latter will be forced inwards, along the grooves and in consequence thereof press the die jaws  13  together. 
     The contacting surface  111   a ,  120   a  between the holders  111  and the locking ring  119 , preferably is self-locking, that is, the inclination is so adapted to the coefficient of friction that a lateral force will not generate a vertical force that might cause a movement in that direction. 
     The blank  124   a  to be forged by means of the die in accordance with the second embodiment of the invention is in the form of a cylinder  124   a  which has been severed from a turned rod. The dimensions of the cylinder  124   a  are such as to allow it to be introduced into a space  125  formed between the mandrel  122  and the die ring  114 . In addition, the blank is heated to at least 650 degrees, preferably to between 1200 and 1300 degrees. 
     In use of the forging apparatus  1 , the blank  117   a  is placed centrally in the space  125  between the die jaws  113 , whereupon the mandrel  122  is moved downwards, through the blank  124   a  until the lower face  122   a  of the mandrel  122  assumes a position below the upper face  106   a  of the guide sleeve  106 . The power-exerting means  112  urge the holders  111  inwards, along the grooves  110 , the holders pushing the die jaws  113  in front of themselves, whereby the above-mentioned die ring  114  is formed and retains the blank in abutment against the mandrel  122 , whereafter the pressing head  117  is lowered towards the support  103  in a two-step operation. 
     In the first step, the locking ring  120  is carried downwards, above the holders  111 , causing the die ring  114  to be pressed additionally together and to be locked in that position. 
     In the second step, the punch  118  is pressed downwards into abutment against the blank  117   a , while at the same time the spring means  121 , interposed between the thrust collar  119  and the locking ring  120 , are compressed. In consequence hereof, the blank  117   a  is compressed axially, and material is being forced down through the annular aperture that has formed between the mandrel  122  and the guide sleeve  106 , flowing along the interior wall of the guide sleeve  106 . The forging operation is completed, when the upper part of the punch  118  abuts against the die ring, and when this happens a component  124   b  (most clearly illustrated in FIG.  5  and bearing numeral reference  56 ) has been formed, configured as a cylinder  57  having an outwardly directed flange  58  at its upper end. 
     Following the completion of the forging operation, the mandrel  122  is lifted out of the forged component  124   b , whereupon the pressing head  117  is returned to its original position, bringing along the locking ring  120 , which releases the holders  111  and the die jaws  113 . The holders  111  are moved apart by the power-exerting means and the ejector  52  is carried upwards, through the guide sleeve  106 , and pushes the forged component  124   b ;  240  upwards. 
     In accordance with an alternative use of the forging apparatus in accordance with the second embodiment, the mandrel  122  is carried upwards and shortly before completion of the forging operation, it is arrested in a position, wherein its lower end  122   a  is level with the lower face  118   a  of the punch  118 . Upon continued pressing, the material is forced radially inwards, along the lower face  118   a  of the punch  118 , closing the cylinder that has been shaped in the forging operation. The finished component thus is given the shape of a cylinder having an outwardly directed flange at one of its ends, which furthermore is a closed end. 
     FIG. 6 is an explosive view of the second embodiment of a forging apparatus in accordance with the invention and merely intends to illustrate the relative orientation of the various parts and their relationship. The drawing figure is essentially applicable also to the other two embodiments, even though some details are different. For example, the spring arrangement with respect to pad  6  of the first embodiment of the forging apparatus is not shown. 
     The forging apparatus in accordance with the third embodiment is shown in FIGS. 7 a ,  7   b . The parts incorporated therein essentially are the same as in the die according to the second embodiment and therefore have been given the same numeral references as in treat embodiment, 
     The essential difference between the dies of the second and third embodiments lies in the extension of the die cavity in the cross-pressing direction, as best illustrated in FIGS. 2 and 8, respectively, and in the configuration of the punch. 
     Like in previous embodiments, the die jaws  213  of die  201  according to the third embodiment essentially are configured as sectors of a circle, such that when in their brought-together position, they form a die ring  214 . However, in this case the space  225  at the center of the ring is essentially rectangular and is formed by two oppositely positioned jaws  60 , which have been cut off in the direction towards the center whereas the remaining two jaws  61  are formed with rectangular recesses  62  in the direction away from the center (see FIG.  8 ). 
     The punch  218  is configured to fit the rectangular space  225  and otherwise it possesses the same characteristics as does the punch  118  in accordance with the second embodiment of the die. 
     The blank  224   a  to be forged by means of the die  201  in accordance with the third embodiment also has a shape allowing it to be introduced into the rectangular shape  225 . 
     In use of the forging apparatus  201  the blank  224   a  is placed centrally in the space  225  between the die jaws  213 , whereupon the holders  211  are displaced inwards, along the grooves  210 , by the power-exerting means  212 , pushing the die jaws  213  in front of themselves in the direction towards the center of the space  225 , such that the die ring  214 , having the rectangular center space, is formed. 
     The forging operation starts by the mandrel  222  being lowered, until its lower faces  222   a  assumes a position below the upper face  206   a  of the guide sleeve  206 , and in doing so urges part of the blank  224   a  in front ot itself. Thereafter, the pressing head  217  is lowered in a two-step operation as has been described earlier. 
     As material is being forced down through the annular opening, along the interior wall of the guide sleeve  206 , the part of the blank that has been depressed by the mandrel  222  is pressed downwards. When the forging operation has come to its end, that is when the abutment face  218   b  of the punch abuts against the die ring  214 , said part of the blank has been shaped against the ejector  52  in the lower part of the guide sleeve  206 , and a component  224   b  having a closed-end cylindrical portion at its lower end, has been formed. The lower face  218   a  of the punch and the inwardly direction flange  54  of the die ring  214  could for example be configured in such a manner that the component  24   b  (best shown in FIG. 9, bearing numeral reference  63 ) may be used as a connecting rod. 
     The tolerances of the parts of the dies described above are such that no material will be pressed into the joints between the various parts during the forging operation. This means that the forged component  24   b ,  224   b ,  324   b  does not exhibit faults such as so called burrs or the like, and therefore may be used directly, or at least after only minor post-treatment, such as e.g. fine smoothing. 
     It should be appreciated that the invention as defined in the appended claims is not limited to the preferred embodiments described above. 
     For example, the directions of reference, such as lower face, upper face, upwards, downwards, radially, axially, and so on are intended to relate to the drawing figures only. Obviously, the die could equally well extend in the horizontal plane and the parts of the die could be positioned differently relative to one another than shown and described. 
     The number of grooves in the grooved disk could vary, and although three or more grooves are preferred, also two grooves are able to produce the desired effect. Actually, the provision of one single groove is conceivable, in which case one of the die jaws is stationary while the other one is movable. 
     In the forging operation, the die jaws may be moved by the locking ring over the very last part towards the center when the punch has already been carried somewhat down between the die jaws. This arrangement would make possible a tighter or closer abutment between the external sides of the punch and the die ring.