Abstract:
In order to avoid the recoil of the striker in a hammer device (tool machine) with a striker ( 18 ) that can be accelerated to strike velocity, and a tool carrier ( 14 ) receiving the impact of said striker, the invention proposes to arrange the striker ( 18 ) between the tool carrier ( 14 ) and a corresponding mass carrier ( 16 ) which moves together with the striker ( 18 ) until the striker ( 18 ) strikes the tool carrier ( 14 ), imparting its own momentum via the striker to the tool carrier, with a supplementary mass ( 56 ) on the mass carrier ( 16 ) providing the necessary striking energy.

Description:
FIELD OF THE INVENTION 
     The object of the invention is a hammer (tool machine), in particular for recoilless high speed impact cutters for the cutting/shearing of wire and/or rod sections, generally for wire processing machines, in particular as part of single or multistage presses where the cutting cycle is integrated into the overall operation of the press. 
     BACKGROUND OF THE INVENTION 
     A device for cutting rod sections on automatic multistage crossfeed presses is known from DE 25 26 151 C3. Here, a striker (hammer) located at the end of a cam-guided striking lever indirectly strikes a sliding blade carrier. Upon the impact of the striker, the sliding blade carrier jumps forward with a high initial velocity (conservation of momentum). Then, coil springs return the sliding blade carrier back into contact with the striker so that the striker can move the sliding blade carrier to a transfer position where the rod section is picked up by a transport gripper. 
     This process has the disadvantage that the impact of the striker on the sliding blade carrier generates recoil which causes the striker to bounce off the sliding blade carrier; this, in turn, imposes a high stress on the cam gear driving the striker. 
     For this reason, the invention intends to solve the problem of avoiding the recoil caused by the impact of the striker on the sliding blade carrier, so that the cam gear is exposed only to a force with limited damaging effect. 
     SUMMARY OF THE INVENTION 
     The invention provides a machine tool hammer specifically intended for impact cutters for cutting sections of wire and/or rods. The tool includes a striker that can be driven back and forth at a selected impact speed, and a tool carrier on which the striker impacts. A separate mass carrier in the form of an auxiliary lever is located on the back side of the striker, facing away from the tool carrier. Starting at an initial position, the mass carrier stays in contact with the striker while following its movement towards the tool carrier until the striker strikes the tool carrier. At this point the movement of the mass carrier stops. The striker continues moving, driving the tool carrier from its starting position to cut the work piece. The striker then changes direction, allowing the tool carrier to return to its starting position, and thereafter taking the mass carrier back to its own starting position. The moving mass of the mass carrier is larger by the amount 2A/v 2  than the moving mass of the tool carrier, where A is the work required to effect the cutting operation and v the operating speed to be provided by the tool carrier. 
     By causing the mass of the mass carrier to be moved by the striker, the cam-driven striker serves only as an intermediate buffer for the tool carrier, to which the momentum of the mass carrier is transferred in such manner that the momentum of the mass carrier and striker combined is equal to the momentum of tool carrier and striker combined. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Below, the invention is explained in detail with the help of the design example shown schematically in the attached drawing. 
     FIG. 1 shows a front view of an embodiment of the invention which, at the same time, also illustrates the starting position of the cutting movement. 
     FIG. 2 shows a top view of the design shown in FIG.  1 . 
     FIG. 3 shows the design of FIG. 1 with a hammer position just before the hammer is accelerated towards the cutting lever. 
     FIG. 4 shows the design of FIG. 1 in an idle position for ejecting the wire section from the cutting sleeve of the movable cutting lever. 
     FIG. 5 shows the design of FIG. 1 with a hammer position as in FIG. 3, but with an alternative hammer drive system. 
    
    
     DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2 show a bolt  12  fixed in position in the frame of a single or multistage press, supporting a cutting lever  14 , an auxiliary lever  16 , and a striker  18  of a high speed cutter that is part of a forming press. A pretensioned compression spring  26  is installed on the spring pin  24  between the free ends of the short arms  20  and  22  of the two-armed levers  14  and  16 . Via a pin  30 , a joint  32  attached to the piston rod  34  of a cylinder-and-piston assembly  36  engages the striker  18 . Via the pin  38 , the cylinder-and-piston assembly  36  is attached to the frame of the forming press. 
     Via a set screw  46 , the longer arm  42  of the cutting lever  14  contacts a counter bearing  48  that is attached to the machine frame. At the end of its longer arm  44 , the auxiliary lever  16  also carries a set screw  50  which contacts the other side of the counter bearing  48 , opposite the set screw  46 . 
     By means of an attachment screw  54 , a movable supplementary mass  56  which performs the cutting work is attached to the long lever arm  44  of the auxiliary. lever  16 . A cutting sleeve  62  is attached to the long arm  42  of the cutting lever  14  by means of a clamping screw  60 . 
     The position of the cutting lever  14  as shown in FIG. 1 permits the feeding of a wire  66  coming from a wire supply, through an additional cutting sleeve  68  that is installed in the frame in line with the cutting sleeve  62  in idle position, and into the cutting sleeve  62  located in the cutting lever  14  (FIG.  2 ). 
     Laterally adjacent to the cutting sleeve  68 , shown on the left in FIGS. 1 and 2, an ejection sleeve  70  which guides an ejection ram  72  sliding on its inside is installed in the frame. 
     The alternate drive system for the striker  18  shown in. FIG. 5 makes use of a cam gear  80 . For this purpose, a non-rotating twin cam plate  84  is installed on a driven shaft  82  of the forming press. A pivoting angled double roller lever  90  is supported in a pivot bearing  88  installed in the frame. Both arms  92  and  94  of this lever  90  each carry a roller  96  and  98 , respectively, which contact the twin cam plate  84 . The upper arm  94  of the double roller lever  90  actuates the striker  18  by means of a tie rod  100 . 
     For actuating the striker  18 , a camshaft or a servomotor, for example, may be used instead of the cam gear  80 . 
     The operation of the high-speed impact cutter is as follows, starting with the condition shown in FIG. 1 where all three levers  14 ,  16 , and  18  are in contact with each other: 
     While the wire  66  is still being fed forward through the cutting sleeves  68  and  62  that are lined up with each other, the striker  18  is removed from the cutting lever  14  by the cam gear  80 , or by the action of the piston rod of the cylinder-and-piston assembly  36 , pulling along the auxiliary lever  16  until the striker  18  and the auxiliary lever  16  reach the position shown in FIG.  3 . This causes the spring  26  to be pretensioned even more, and it holds the cutting lever  14  in contact with the counter bearing  48 . 
     Now, the striker  18  is accelerated back into its starting position shown in FIG. 1, either by the cam gear  80 , or by applying a pressure medium to the piston of the cylinder-and-piston assembly  36 . In the course of this process, the spring  26  holds the auxiliary lever  16  in contact with the striker  18 . After completion of the feeding of the wire into the cutting sleeve  62 , the accelerated striker  18 , together with the auxiliary lever  16  and the supplementary mass  56  attached to the same, impacts on the cutting lever  14  at a certain speed. Now, the cutting lever  14  immediately rotates—to the left in FIG.  1 —around the pin  12  with the same speed as the striker  18 . 
     Via the striker  18 , the kinetic energy stored in the moving auxiliary lever  16  is transferred to the cutting lever  14  in such manner that the auxiliary lever  16  stops immediately (physical law of the conservation of momentum). No other reaction force has been applied to the striker  18  but that which corresponds to the energy required for cutting the wire  66 . This additional energy can be determined experimentally and be made available by means of the moving supplementary mass  56 . 
     FIG. 4 shows the striker  18  and the cutting lever  14  in a return idle position. While they remain in this position, the ejector ram  72  sliding in the ejection sleeve  70  ejects the wire section  76  of the endless wire supply  66  (that had been cut/sheared by the cutting sleeves  62  and  68 ) from the cutting sleeve  62  in conventional manner for further processing in the forming press. The return position of the cutting lever  14  for the ejection of the wire section  76  was reached by further actuation of the cylinder-and-piston assembly  36 , or by means of the cam gear  80 ; in the course of this, the cutting lever  14  was moved away from the counter bearing  48  by the striker  18 , against the force of the spring  26 . 
     After the ejector ram  72  has been removed from the cutting sleeve  62  of the cutting lever  14 , the striker  18 , the cutting lever  14 , and the auxiliary lever  16  are returned to the pivot position shown in FIG. 3 by an actuation of the piston rod of the cylinder-and-piston assembly  36 , or by the cam gear  80 , with the movements described above occurring in reverse: i.e., when the striker  18  impacts the immobile auxiliary lever  16 , this auxiliary lever  16  picks up the momentum of the striker  18  and the cutting lever  14 , and the striker  18  keeps moving along with the auxiliary lever  16  without delay. 
     As proposed by the invention, the arrangement of the striker  18  between the cutting lever  14  and a mass carrier, i.e. the auxiliary lever  16  (disregarding the supplementary mass  56  of this lever for the moment), can be compared to the familiar physical arrangement of three ideal spherical pendula in one plane, where two outer spheres of identical mass are each in contact with a center sphere of random mass. If the center and one outer sphere together are pulled away from the other outer sphere (by deflection of the pendulum), and are then released, the outer sphere trailing the center sphere stops when the center sphere impacts on the previously immobile outer sphere and pushes it along. Here, the theorem of the conservation of momentum and energy applies, if no other forces besides gravity are present. Specifically, this means that the center sphere transfers the momentum of the trailing outer sphere to the other outer sphere that is being pushed away while fully retaining its own momentum, so that there is no complete transfer of momentum as will happen in the same spherical pendulum arrangement if only the one outer sphere is pulled away from the center and other outer sphere, both of which remain at rest, and is then released. 
     The assembly  36 , or the gear  80 , is needed for driving the striker  18  in order to allow a machine-synchronous operation, and also for selecting the desired cutting speed. The mass of the striker  18  is not an essential feature. 
     The present invention may be further characterized by the following numbered paragraphs. 
     I.) Hammer (tool machine), specifically intended for impact cutters for cutting sections of wire and/or rods, with a striker that can be driven at impact speed, and a tool carrier on which the striker impacts, characterized by the features that on the back side of the striker ( 18 ), facing away from the tool carrier (cutting lever  14 ), a separate mass carrier (auxiliary lever  16 ) is located; this mass carrier stays in contact with the striker ( 18 ) while following its movement towards the tool carrier ( 14 ), until the striker ( 18 ) strikes the tool carrier ( 14 )—which interrupts the action of its drive system—and stops at the same time; by means of the striker ( 18 ) that is being moved back to its starting position, said mass carrier ( 16 ) is taken along back to its own starting position, starting at that moment when the striker ( 18 ), its drive system resuming operation again, strikes the mass carrier ( 16 ), and the tool carrier ( 14 ) that has been moved back to its starting position stops at the same time; and that the moving mass of the mass carrier ( 16 ) is larger by the amount 2A/v 2  than the moving mass of the tool carrier ( 14 ), where A is the cutting work and v the operating speed to be provided by the tool carrier ( 14 ). 
     II.) Hammer as in Paragraph I, whose driven tool carrier can be moved back to its starting position by means of a return spring, characterized by the features that the tool carrier and the mass carrier are designed as two-armed levers ( 14  and  16 , respectively) with a common pivot point (pin  12 ) on which the striker ( 18 ) pivots between the two levers ( 14  and  16 ); that the two longer arms of the levers carry the tool (cutting sleeve  62 ) and an exchangeable supplementary mass ( 56 ), respectively, and that the return spring (compression spring  26 ) is installed between the two shorter arms of the levers; and that they are each equipped with a stop (setscrew  46  and  50 , respectively) which acts in conjunction with a fixed counterstop (counter bearing  48 ) that is located in the pivoting sector of the striker ( 18 ). 
     III.) Hammer as in Paragraphs I or II, characterized by the feature that the striker ( 18 ) can be driven by means of a push and pull rod ( 34 ;  100 ) linked to it by means of a pivot joint. 
     IV.) Hammer as in Paragraph 3, characterized by the feature that the push and pull rod is the piston rod ( 34 ) of a cylinder-and-piston assembly ( 36 ). 
     V.) Hammer as in Paragraph III, with a contacting cam gear ( 80 ) whose two rollers ( 96  and  98 ) are attached to an angled lever ( 90 ), characterized by the feature that the push and pull rod ( 100 ) is linked to one ( 94 ) of the two arms ( 92  and  94 ) of the lever. 
     VI.) Use of the hammer as in one of Paragraphs I-V with impact cutters having one movable ( 62 ) and one fixed ( 68 ) cutting sleeve, characterized by the feature that the tool carrier (cutting lever  14 ) accepts the movable cutting sleeve ( 62 ) and can be moved between a starting position in which the two cutting sleeves ( 62  and  68 ) line up along the material (wire  66 ) to be cut, and an end position in which the movable cutting sleeve ( 62 ) in alignment with the cut section of material (wire section  76 ) lines up with a fixed ejection sleeve ( 70 ) guiding an ejection ram ( 72 ).