Abstract:
The invention relates a drop forging method by means of a forging device provided with a hammer and a forging die, wherein a part placed in the forging die is shaped with a hammer blow, several engravings are formed in the die, a blank is initially inserted into the first engraving and said blank is moved along the other engravings to the last engraving, and then said blank picked up during shaping by a forging gripper. In order to obtain an optimum operating mode, the invention is characterized in that the part is received in a plurality of engravings with each hammer blow. In order to obtain a symmetrical distribution of the hammer load between occupied and non-occupied engravings, the parts are gripped respectively during shaping by the forging grippers. After each hammer blow, a successive displacement of the parts is carried out in the other engravings by removing the part from the last engraving or from the last but one by an engraving occupied by a part and a blank is inserted in the first engraving to be occupied.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application is a continuation of pending International patent application PCT/EP2004/053189 filed on Dec. 1, 2004 which designates the United States and claims priority from German patent application Nos. 10 2004 028 378.8 filed Jun. 11, 2004 and 103 56 258.3 filed Dec. 1, 2003, the contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates to a drop forging method, with a forging device having a ram and a die, a part lying in the die being shaped by a hammer blow, a plurality of impressions also being formed in the die, and a blank first being placed into a first impression and subsequently passing successively through further impressions to a final impression, and furthermore the part being gripped during the shaping by a forging gripper.  
       BACKGROUND OF THE INVENTION  
       [0003]     During forging, it has long been the custom to hold the part to be forged by means of gripping tongs. Even when the method is carried out with a forging device having a ram and a die, that is to say with a hammer, the part lying in the die is held by means of a forging gripper. This prevents the workpiece from shifting in the impression. When the method is carried out by means of hammers, after forging by the first impression, the part lying in the die is successively placed in the following impression if a number of impressions are provided, until the part to be forged has passed through the further impressions to the final impression. In the case of such forging devices formed as hammers, the kinetic energy of the ram is used for shaping the workpieces. Examples of hammers that are used as forging hammers are drop hammers, hydraulic hammers and also counterblow hammers.  
         [0004]     Apart from the forging devices formed as hammers, forging presses are known, in which the compressive forces are transmitted by means of a path-controlled press ram. These allow good forging results to be achieved, albeit also with relatively high initial costs. Moreover, not such high numbers of cycles per unit of time can be achieved as in the case of a forging hammer.  
         [0005]     There is known from DE 31 29 482 C2 a forging press with a plurality of impressions formed one adjacent the other in the direction of passing through. Automatic transport of the workpieces is effected, but when a workpiece has been placed into an impression, the transporting device is withdrawn, that is to say is separated from the tool, while the forging operation is carried out. A comparable method and a comparable forging press are known from DE 199 58 846 A1. In this connection, it is also generally known from DE 33 23 359 C2 to handle forged parts automatically in a forging method. To be specific, here it is proposed to forge on an auxiliary body, which may be used for the engagement of transporting tongs and for the accurate positioning of a forged part in an impression.  
         [0006]     On the basis of a forging method that is performed on a forging hammer, as presupposed at the beginning, the invention is concerned in first instance with the object of providing a drop forging method with a forging device having a ram and a die which, while making use of the generally more advantageous initial costs and high achievable numbers of cycles of such a device, nevertheless makes a high degree of automation possible, without having to accept disadvantages in the forging quality that is customary for such devices.  
         [0007]     Furthermore, the invention is also concerned with the object of providing a drop forging device, with a ram and a die, which, while making use of the advantageous initial costs of such a device, makes forging with a high degree of automation and high achievable numbers of cycles possible, without having to accept disadvantages in quality.  
       SUMMARY OF THE INVENTION  
       [0008]     With regard to the method, the stated object is achieved first and foremost in the case of the subject matter of claim  1 , it being provided that, with every hammer blow, a part is accommodated in a plurality of impressions, with symmetrical distribution between occupied and unoccupied impressions with regard to loading of the ram, the parts being respectively gripped during shaping by the forging gripper, and after every hammer blow a successive displacement of the parts into a further impression being performed, with a part being removed from the final impression or the last impression that is occupied by a part before the final impression, and the blank being placed into the first impression to be occupied. It is preferred that, with every hammer blow, a part is accommodated in each impression, which part is respectively gripped during the shaping by the forging gripper and after every hammer blow is successively displaced into the adjacent impression toward the final impression. In this process, a part is in each case also removed from the final impression and a further part is placed into the first impression. However, even with the method described here, it is possible, as explained in principle for a forging press in the already cited DE 31 29 482 C2, always to skip certain impressions, including in an alternating manner, so that all the impressions are occupied in a specific rhythm, but not simultaneously; this while paying attention to the most uniform loading possible, as desired with regard to a ram, to keep the guides in good condition. It is pertinent that according to the method described here, the hammer is always loaded virtually uniformly. This not only results in less loading of the guides, but also has advantageous effects on the quality of the forged piece. The method is here carried out in a way that is known in principle to this extent, with the forged pieces being constantly gripped. As a result of the described uniform loading of the forging hammer, not only are the guides found to become less worn, but also the forging displacement on the forged pieces is not increased in comparison with known methods, but even generally reduced.  
         [0009]     The described method is preferably suitable for forging forged parts such as the halves of pliers. In principle, however, it is also suitable for other forged parts; in particular for such parts as have a greater length than width. These may, for example, also be parts such as connecting rods or camshafts.  
         [0010]     If the method is carried out on a forging device having two guide pillars, forming a double-stand type of construction, there is the possibility that the parts accommodated by the impressions are disposed one adjacent the other in a connecting line of the guide pillars and are successively displaced on this connecting line. The die is then aligned in the same way as in customary methods that are known per se. However, by contrast, it is ensured in the case of the method according to the invention that, with the hammer blow, a multiplicity of impressions are occupied, in a symmetrical way with regard to the loading of the ram, and not just one impression as in the prior art. An advantageous alternative according to the invention is that of designing the method in such a way that the parts to be forged, or “blanks”, run in over as short a path as possible and can be set down at the end of the forging operation without changing their position. For this purpose, the impressions are disposed one adjacent the other in a series lying transversely in relation to a connecting line of the guide pillars, and the parts are successively advanced in the direction of this series arrangement. The parts themselves consequently lie in the connecting line or parallel to it. This specifically takes the form that the parts removed from the final impression and/or placed into the first impression are introduced and/or discharged in a direction parallel to the direction of passing through. According to the invention, it is appropriate in this respect that, on the transporting device reaching right up to the forging device, the parts introduced and/or discharged are heat-treated by means of a heating system associated with said transporting device. The forged parts are consequently brought to the required temperature necessary for working the parts. To allow the successive displacement of the parts to be advantageously performed, the parts are in any case transported in the die from impression to impression by simultaneous raising and setting down at their opposite end regions. For example, this may take place by means of crank ejectors from impression to impression or from cavity to cavity. The end regions of the parts are used to grip onto the parts. Access to the parts takes place from below. Troublefree implementation of the method results from the fact that the transporting rhythm of the parts is synchronized with the forging frequency. Then the method according to the invention allows the same part to be forged two or more times in an impression of the same form, these impressions being separate from one another and passed through one following after the other in the direction of passing through. Identical and non-identical impressions are therefore provided in irregular sequence. With regard to the possibility of only occupying some of the impressions, albeit in a symmetrical manner, with every hammer blow, it is therefore also possible for a number of identical impressions to be provided one adjacent the other or in symmetrical sequence in relation to one another, as required by the working steps themselves. The forging of one and the same part two or more times in impressions of the same form can lead for example to a better surface and to greater dimensional accuracy.  
         [0011]     The forging device may still be constructed in the tried-and-tested manner. By occupying the impressions with parts in a symmetrical manner with regard to the loading, or occupying all the impressions with parts, the guides are uniformly loaded. During the return movement of the ram after each hammer blow, the parts lying simultaneously in all the impressions, apart from a part lying in the final impression or the last impression that is occupied before the final impression, are transported at the same time into the adjacent or next-provided impression in the direction of passing through. The die may form at least two impressions of the same form one adjacent the other. Furthermore, the die having the impressions positioned one adjacent the other may have a different alignment in relation to the connecting line of the guide pillars. In particular, there are two possibilities for this. One possibility is that the impressions are disposed one adjacent the other in a connecting line of the guide pillars. On the other hand, the impressions may also be disposed in a series one adjacent the other transversely in relation to the connecting line of the guide pillars. An advantageous configuration is distinguished by providing a transporting device for the parts to be placed into the first impression and/or to be removed from the final impression, with a transporting direction parallel to the direction of passing through. This alignment allows the transporting device for introducing and/or discharging the parts to reach right up to the forging device and allows the transporting device to have in the region of introduction and/or discharge a heating system for heat-treating the parts. To allow the parts to be moved from one impression into the other, the die has a conveying mechanism for raising, conveying and setting down the parts from impression to impression by engaging opposite end regions of the parts. This conveying mechanism is coordinated with the operating mode of the ram, so that a transporting rhythm of the parts that is synchronized with the forging frequency can be obtained.  
         [0012]     Independently of whether all the impressions or only some of the impressions are occupied with a part, in a symmetrical manner, with every hammer blow, it is preferably provided with regard to the transporting device that a forging and transporting gripper is associated with every impression irrespective of the occupation with each hammer blow.  
         [0013]     With regard to the tool costs and the mode of operation, it proves to be of advantage for the forging and/or transporting grippers to be disposed outside a base area of the die. Both the die and the forging and/or transporting grippers represent modules that are independent of one another, so that each can itself be optimally configured. The use of a forging hammer instead of a forging press brings the advantage of low-cost construction of the forging device. In particular, use of a drop hammer as the hammer is commended. This means that, when there is movement of the ram toward the forged piece, acceleration due to gravity takes effect, while raising takes place by means of a lifting member. According to the invention, the hammer may be a counterblow hammer. In this case, the lower ram and upper ram move counter to each other, so that losses of energy due to impact and propagation of the impact in the floor are avoided entirely. The forging and transporting grippers would then have to be disposed at an appropriate level to be associated with the forging tools. The counterblow hammers may even help to simplify the gripping and conveying mechanism, because they offer more space. Such counterblow hammers are of advantage in particular for the forging of crankshafts. Also to be emphasized is the fact that the forged part is constantly gripped during forging, whether by the forging gripper or the transporting gripper. If this gripping takes place by the transporting gripper, the latter even performs a dual function. With regard to its association with the hammer, advantages are obtained in that the guide pillars have at the level of the lower die a recess facing the die for receiving the forging and/or transporting grippers. Moreover, the grippers are configured in such a way that the geometry of the gripping ends, changing during a forging blow, or their alignment, can be taken into account. For this purpose, the forging grippers may for example have pivotally suspended gripping heads or resiliently yielding gripping heads. Up to a certain extent, slipping of the blanks in the gripping ends may also be tolerated. Finally, it must also be emphasized that the forging and/or transporting grippers may be formed in such a way that they are hammer-resistant. On account of this, it is of advantage that the forging and/or transporting grippers move in concert with the movement of the forging hammer with every forging blow. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     Several exemplary embodiments of the invention are explained below with reference to the drawings, in which:  
         [0015]      FIG. 1  shows a view of a forging device according to the first embodiment for carrying out the method;  
         [0016]      FIG. 2  shows a section along the line II-II in  FIG. 1  in a schematic representation;  
         [0017]      FIG. 3  shows a schematic representation of the lower die in front view;  
         [0018]      FIG. 4  shows the view according to the direction of arrow IV in  FIG. 3 ;  
         [0019]      FIG. 5  shows a forging device according to the second embodiment in schematic plan representation;  
         [0020]      FIG. 6  shows a longitudinal section through an impression of a die with a modified conveying mechanism, operating on a double-tong principle, with a part still lying in the impression;  
         [0021]      FIG. 7  shows a representation following on from  FIG. 6 , the part having been lifted out of the impression by means of the transporting tongs and the gripping tongs being located in their release position;  
         [0022]      FIG. 8  shows a view comparable to  FIG. 1  of the forging device according to the third embodiment;  
         [0023]      FIG. 9  shows a cross section through the forging device above the lower die; and  
         [0024]      FIG. 10  shows a cross-sectional representation in the region of the transporting and forging grippers located in the position of engagement. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]     The exemplary embodiments are described with regard to carrying out the method in such a way that a part is accommodated in every impression for every hammer blow.  
         [0026]     According to the first embodiment as shown in FIGS.  1  to  4 , the forging device for carrying out the method is designated by the number  1 . The forging device  1  has two guide pillars  2 ,  3 , disposed parallel to each other. The latter extend from an anvil block or a base plate  4 , which for its part is supported on a foundation  6  by means of an intermediate layer  5 .  
         [0027]     The guide pillars  2 ,  3  accommodate between them a ram  7 , which can be moved in the vertical direction and is engaged by a drive  8 .  
         [0028]     Between the pillars  2 ,  3 , the base plate  4  carries a lower die  9 , which can be secured there by means that are not represented. Opposite the lower die  9 , the ram  7  is provided on its underside with an upper die  10 .  
         [0029]     The die  9  has a rectangular outline and forms on its upper side a plurality of impressions a, b, c, d and e, positioned one adjacent the other. The impression a is the first impression and the impression e is the final impression. The impressions a to e serve for accommodating parts T to be shaped. The direction of passing through x of the parts placed into the impressions a to e runs transversely in relation to the connecting line of the guide pillars  2 ,  3 . It is provided for the impressions a to e to be positioned one adjacent the other in such a way that they are generally spaced equally from one another. When there is a hammer blow, the opposing impressions (not represented) of the upper die that interact with the impressions a to e lead to shaping of the parts T placed in the impressions a to e.  
         [0030]     As can be seen from the plan view representation, when the forging device  1  is in operation, a blank R is placed into the first impression a. After being placed into the first impression a, this blank therefore represents a part T to be shaped. Serving for introducing and discharging the parts T is a transporting device  11 ,  12 , which reaches right up to the forging device and is formed by two sections. The transporting device  11  reaches up to the side of the die  9 , which forms the first impression a. The transporting device  12  is adjacent the final impression e. The finished forged parts are conveyed away on it. This means that the parts placed into the first impression a and the parts removed from the final impression e are introduced and discharged in a direction parallel to the direction of passing through x the die  9 . If appropriate, removal of the finished forged parts can also take place by a differently configured transporting device.  
         [0031]     It can be seen from  FIG. 2  that a heating system  13 , indicated by dashed-dotted lines, is associated with the transporting device  11  reaching right up to the forging device  1 . This ensures that the blanks are always at the requisite temperature when they are placed into the first impression a. The use of a heating system would also be possible on the transporting device  12 , in order to heat-treat the finished forged parts for possible further processing.  
         [0032]     It can be seen from the plan view representation according to  FIG. 2  that, starting from the first impression a, the parts placed into the impressions a to e are continuously brought into the final form in the impression e. In the case of the exemplary embodiment, the impressions a to e are configured in such a way that halves of pliers, as are used in water pump pliers, can be forged in them. For example, the impressions b and c may be configured in the same form, so that the same part T is forged twice in an impression of the same form. As can be gathered from the drawing, these two impressions b and c are passed through one following after the other in the direction of passing through.  
         [0033]     The longitudinal extent of the impressions a to e runs in a transversely directed manner in relation to the longitudinal sides of the die  9 . A conveying mechanism  14  is associated with each longitudinal side. These mechanisms are identical in their construction, so that only one is explained below. Each conveying mechanism  14  has two pivotally mounted crank arms  15  with pivot axes  16  aligned parallel to the impressions a to e. One crank arm  15  is adjacent the first impression a and the other adjacent the final impression e. Mounted on crank pins  17  that are provided on the crank arms  15  are links  18 , which for their part are fixed by their link end  19  on a conveying bar  20  guided in the longitudinal direction outside the die  9 . Consequently, two conveying bars  20  are provided, moving close to the longitudinal sides of the die  9 .  
         [0034]     After starting the forging device, the state in which all the cavities or impressions a to e are occupied with parts T is obtained. This leads to uniform loading of the ram  7  occurring with a hammer blow, which has advantageous effects on the guiding of the ram and to a great extent does not cause any forging displacement of the parts that undergo the deformation. In the same way, this has advantageous effects on the guiding of the die. During a hammer blow, the conveying bars  20  are in a corresponding position, compare  FIG. 4 . In this position, the parts T lie with their opposite end regions  35  in upwardly open transporting indentations  21  of the guiding bars  20 . In addition, deployed abutments  27  act on the end portions  35  of the parts T, configured as gripping ends. During the return stroke of the ram  7 , the conveying bars  20  are raised by pivotal displacement of the crank arms  15  in the indicated pivoting direction following retraction of the abutments  27 , and consequently the parts T are lifted out from their impressions a to e in order to be placed into the adjacent impression in the direction of passing through. This does not apply to the part lying in the final impression e, since this is then associated with the discharging transporting section  12 . At the same time as this operation, a new blank, coming from the transporting section  11 , is placed into the first impression a. In this way, with every hammer blow, all the impressions are each loaded with a part, which parts successively pass through the die. To allow this to be carried out in a troublefree manner, the transporting rhythm of the parts is synchronized with the forging frequency.  
         [0035]     According to the second embodiment as shown in  FIG. 5 , the same components have the same reference numerals. As a departure, the impressions a to e of the die  9 ′ are now disposed one adjacent the other in a connecting line of the guide pillars  2 ,  3 . This means that the parts accommodated by the impressions are successively displaced on this connecting line during the forging.  
         [0036]     A transporting mechanism  11  similar to in the case of the previous embodiment is then provided. To allow the first blank R in the conveying direction to be transferred as intended to the first impression a, a turning station S is associated with the transporting mechanism  11 , which station in each case turns the corresponding blank R through 90° in accordance with the forging frequency and allows it to be pushed into the first impression a. Also provided in this version is a heating system  13 , by means of which the blanks delivered to the forging device  1  are brought to the requisite temperature.  
         [0037]     Also represented in this version is a transporting mechanism  12  for transporting the finished forged parts away.  
         [0038]      FIGS. 6 and 7  concern a modified configuration of conveying mechanism  22 , associated with the die  9 . This mechanism operates on the double-tong principle. Therefore, two transporting tongs  23 ,  24  are disposed positioned one above the other. The latter are adjacent the relevant side surface of the die. Projecting beyond this is the end  35  of the part T placed into an impression. On the other side of the transporting tongs  23 ,  24  are forging tongs  25 ,  26 , which can likewise entering into gripping engagement with the end  35 . While the forging tongs  25 ,  26  only perform an opening and closing movement according to the direction of the arrow, the transporting tongs  23 ,  24  can carry out a transporting movement along the side surface of the die in their closed position  23 ,  24 .  
         [0039]     To be specific, the conveying mechanism  22  operates as follows:  
         [0040]     during the hammer blow, the gripping tongs  25 ,  26  grasp the end  35  of a part T lying in an impression, while the transporting tongs  23 ,  24  are released from the end  35  and are in a position away from the latter, cf.  FIG. 6 .  
         [0041]     Once a hammer blow has taken place, the forging tongs  25 ,  26  open. This is accompanied by the forging tongs  23 ,  24  entering into a position of engagement with the end  35 , so that subsequently the part T lifted out from the impression can be placed into an adjacent impression by means of the transporting tongs  23 ,  24  performing a conveying movement. During the opening of the transporting tongs  23 ,  24 , the forging tongs  25 ,  26  then enter into engagement with the end  35 .  
         [0042]     According to the third embodiment as shown in FIGS.  8  to  10 , the same components have the same reference numerals.  
         [0043]     As a departure from the first embodiment, forging grippers  28  and transporting grippers  29 , forming a conveying mechanism  22 , are now provided on both sides of the lower die  9 . Furthermore, the guide pillars  2 ,  3  have level with the lower die  9  a recess  30  facing the latter for receiving the forging and transporting grippers  28 ,  29 . The latter are formed in such a way that they are hammer-resistant and therefore move in concert with the forging device  1 , which is configured as a forging hammer, with every forging blow. As also in the case of the first embodiment, the hammer is a drop hammer. As in the case of the first embodiment, the longitudinal extent of the impressions a to e then runs in a transversely directed manner in relation to the longitudinal sides of the die  9 . Two transporting bars  31 ,  32 , which are disposed one above the other and for their part are carriers of the transporting grippers  29 , are associated with each longitudinal side. The transporting bars  31 ,  32  are controlled in such a way that they can perform a longitudinal movement in the direction in which the parts pass through. Furthermore, the transporting bars  31 ,  32  are displaceable toward each other. Both the lower die  9  and the upper die  10  are provided with five impressions a, b, c, d and e, lying one after the other. By contrast, six transporting grippers  29  respectively extend from the transporting bars  31 ,  32 . The spacing of the transporting grippers  29  from one another corresponds to the spacing of the impressions from one another. It is therefore possible that grippers  29  associated with the introducing transporting section  11  can receive a part arriving there.  
         [0044]     As can be seen from  FIG. 10 , the lower transporting grippers  29  are carriers of extension arms  33 . Each extension arm  33  is supported by means of a compression spring  34  on the transporting bar  32 . The spring excursion of the lower grippers  29  is designed in such a way that a small upward stroke can be carried out from the position of engagement with the ends  35  of the parts T, which ends  35  serve as gripping ends, thereby achieving a certain spring-loading effect.  
         [0045]     Level with the impressions, two forging grippers  28  are associated with each of them. Each forging gripper  28  is displaceable in the direction of the double-headed arrow according to  FIG. 10  and can accordingly be brought into the position of engagement with the gripping ends  35  of the parts. In addition, each gripper  28  is able to perform a pivoting movement about a vertical axis  36 . The engagement surfaces  37  acting upon the gripping ends  35  run parallel to each other and are made smooth.  
         [0046]     The transporting rhythm of the parts T is synchronized with the forging frequency. Control of the forging grippers  28  also takes place correspondingly, said grippers entering into a position of engagement with the gripping ends  35  from a release position—represented by dashed-dotted lines. Once this has taken place, the hammer blow is carried out by downward displacement of the ram  7 , cf.  FIG. 10 . This means that the forged piece T is constantly gripped during the forging and is accordingly in a controlled position. During this operation, the transporting grippers  29  likewise remain in engagement with the gripping ends  35 . However, it would also be possible for the transporting grippers  29  to assume a position away from the gripping ends  35  during the forging.  
         [0047]     It can be seen in particular from  FIGS. 9 and 10  that the ends of the blanks or parts T have a lateral projection beyond the die  9 . The projections form the aforementioned gripping ends  35 . The parts or blanks may be configured as round material. However, the use of flat material is also possible for example. It is then also possible for a certain mass distribution to be provided with respect to the blanks, that is to say a pre-deformation of the same.  
         [0048]     It can be gathered from  FIG. 9  that, with every forging blow, the geometry of the gripping ends  35  or their alignment changes. The forging grippers  28  are capable of allowing for such a change. If the geometry changes, the gripping ends  35  that are held with non-positive engagement by the forging grippers  28  between the abutment surfaces  37  slip into the corresponding position. It is therefore ensured that the forged pieces are nevertheless held in a controlled manner during the forging operation.  
         [0049]     In addition, it is possible that, during the operation described above, the forging grippers  28  can pivot about the vertical axis  36 , in order to obtain an adaptation or alignment of the gripping ends. In the release position of the forging grippers  28 , the latter then return again to their starting position.  
         [0050]     All disclosed features are (in themselves) pertinent to the invention. The disclosure content of the associated/accompanying priority documents (copy of the prior application) is also hereby incorporated in full in the disclosure of the application, including for the purpose of incorporating features of these documents in claims of the present application.