Slide with segmented tooling held closed by stationary remote spring

#The invention relates to forging machines and, in particular, to an arrangement for improving the performance of segmented radially moveable tooling on such machines.

#Multi-station forging machines have demonstrated their ability to mass produce parts of complex shape in an economical manner. In using a progressive forging process to produce a complex part from round wire, there is frequently a need to create an hourglass shape, i.e. two bulbous zones longitudinally spaced by an intermediate zone narrower than each bulbous zone. To control the shape of the part, it is customary to use segmented tooling that can close on the narrow zone and open sufficiently to allow longitudinal passage of one of the bulbous zones. A problem often encountered with segmented tooling is that the pressure forces on the segments in the forging process, urges them to separate and, in turn, they push back on those elements intended to constrain them in a closed or constricted position. The pressure forces involved in the forging action can exceed the ability of the constraining elements and the segments can open slightly in the forging blow. When this happens, the precision of the part shape degrades, unwanted and detrimental material flash can occur between the segments and tooling wear can be accelerated. Conventionally, the segments are confined in the tapered bore of a sliding die case and the die case is spring-biased in a direction that resists opening of the segments. Traditionally, springs have been situated behind the sliding case. Ordinary springs, even when they are several in number and distributed around the die center, provide a relatively small force that can be inadequate to resist the reaction forces occurring in the sliding surfaces of the tooling. One approach to solve this problem has been to use a larger machine where more room is available for larger springs. A relatively recent approach to increase the biasing force on the die case has been to mount a gas spring on the die breast below the die station in question and transmit the spring force through a lever that multiplies the spring force.

#In the forging of some complex parts, it is necessary or desirable to employ sliding, segmented tools on the slide or ram. This application of such segmented tooling faces the same challenge of biasing the tool case with sufficient force to prevent reverse movement of the case and consequent opening of the segments. In general, the space available around the tool case on the slide severely limits the hardware, apart from the regular tooling, and related appurtenances, that can be mounted on the slide. This lack of room makes it difficult to utilize large conventional springs. Moreover, there typically is insufficient room to mount a gas spring or structurally adequate supporting bracketry as well as a lever at a typical work station on the slide. Additionally, it is desirable to minimize the mass being reciprocated on the slide. Still further, where a gas spring requires liquid cooling, the supply of such coolant to a reciprocating slide is problematic.

#FIG. 1 is a vertical cross-sectional view through the center of a workstation of a multi-station progressive forging machine in a plane parallel to the direction of slide movement; and

#FIG. 2 is an isometric view of a lever and tool case.

#Referring now to FIG. 1, there is partially shown in vertical cross-section, a multi-station progressive cold forming or forging machine 10 having at the left a stationary die breast 11, and at the right a reciprocating slide or ram 12. The overall arrangement of the machine 10 is generally conventional and reference to U.S. Pat. No. 4,898,017 can be made for the general organizational details of the machine frame and drive, the disclosure of which is incorporated herein by reference.

#FIG. 1 represents a station in the machine in which a part is being progressively formed and it is desired to form the part with segmented tooling mounted on the slide 12 so that an hourglass-shaped area is made on a work piece or part 13. A center line of the die and punch elements is indicated at 14.

#A die 16 is assembled in a die block 17 carried on a breast plate 18. Hanging directly below the die 16 is a high force compression spring 19 in the form of a nitrogen gas spring of a commercially available type. The gas spring comprises a cylinder 21 and a piston 22 with a piston rod 23 extending out of the cylinder 21. Preferably, the central axis of the spring 19 is parallel to and directly vertically in line with the center line 14 of the die and punch. The spring 19 is supported vertically and laterally with respect to its horizontal axis in a bracket 24 having a bore that closely fits the outside diameter of the cylinder 21. A rear or bottom end 26 of the cylinder 21 is axially supported, preferably through direct abutment, with the breast plate 18. A forward end 27 of the piston rod 23 presents a flat vertical surface. The spring cylinder 21 rearward of the bracket 24 is encased in a cylindrical shell 28. The interior of the shell 28 is formed with a continuous helical groove 29. Ends of the shell 28 are sealed in a liquid-tight manner on the outside surface of the cylinder 21. Liquid coolant/lubricant, such as circulated in other parts of the machine 10 is conducted through the groove 29 so that it is in contact with the outer surface of the cylinder 21 and is thereby enabled to draw heat from the spring 19 produced by cyclical compression of the spring during operation of the machine 10 as discussed below.