RU2098216C1 - Hammer head and rod joint assembly - Google Patents

Abstract

FIELD: plastic metal working, namely, construction of forging hammers. SUBSTANCE: joint assembly includes rod stem arranged in seat of head and joined with part along cone surface. Rod has recess on transition portion between its cone and cylinder parts. Recess has rounded edge turned to said cone part. Length l and depth h of recess are selected according to conditions:

and

Description

 The invention relates to the processing of metals by pressure. Specific to the design of forging hammers.

 Known node connecting the rod with the hammerhead according to the invention (ed. St. N 1473894, 1987). This assembly consists of a tapered shank and a rod located in the socket of a woman by means of intermediate ones installed in the gap: packets of split rings, half-sleeves and a split sleeve.

 The disadvantages of this node is the design complexity due to the large number of parts, the difficulty of mutual adjustment (mating) of the contact surfaces. In this regard, the durability of such a node cannot be sufficiently high.

 Also known node "Device for connecting the rod to the hammer head" by ed. 1639868, 1989

 This assembly contains a conical shaft end mounted in the axial cavity of the woman with the adapter sleeve. At the same time, grooves are made on the outer surface of the sleeve at the output section, and its internal cavity is conjugated to the stem shank.

 The disadvantage of this node is the lack of durability, since the grooves on the outer surface of the sleeve, reducing the contact surface with the mating surface of the socket, will lead to accelerated destruction of these surfaces due to increased specific loads and pressure stresses.

 In addition, it is known that the solid sleeves used at the Izhstal production association in Izhevsk do not provide a sufficient increase in the durability of such a joint.

Known node connecting the rod with a hammer woman according to [1]
The disadvantage of this node as well as nodes with adapter sleeves is their low durability due to the low resistance of the stem (it breaks in the section above the shank, in the immediate vicinity).

 Moreover, the small durability of this unit on the one hand is determined not only by its high complexity of construction, but also by the fact that in the zone of contact of the upper part of the cone of the stem shaft with the headstock, large tensile stresses arise (with joint bending and compression), which leads to fatigue cracks, which ultimately lead to damage to the shank. The presence of a hollow cavity 7 with a liquid that receives the energy of impact of the piston. In this case, the hollow part is subject to fluid pressure from the inside of the stem, which leads to additional tensile stresses along the line of contact between the shank and the woman in the transition zone from the conical and cylindrical parts. Thus, the stress state increases, which increases the likelihood of fatigue stress of the rod at the top of the woman.

 The problem solved by the invention is to increase the durability of the node connecting the rod with the hammer head by increasing the resistance of the rod.

где d_м.хв. максимальный диаметр хвостовика в его верхней части.This problem is solved in that the node connecting the rod to the hammer head containing the stem shaft located in the axial socket of the head coupled to the socket on a conical surface is made so that a recess is made on the rod at the transition from the conical to the cylindrical part with a rounded edge facing the conical part, while the length l and depth h are selected from the relations

where d _m.hv. maximum diameter of the shank in its upper part.

 The rationale for the limits in the ratios.

At l / d _m.hv. <0.25, the length of the recess l is insufficient, since when the shank of the stem shrinks deeper into the nest in the head, the recess can completely enter the inside of the nest. In this case, the positive effect of the notch on preventing the occurrence of microcracks will cease, since the dangerous zone of rod breakage will move above the notch to a place that will be tightly covered by the upper input section of the socket.

At l / d _m.hv. > 0.30 the length of the notch will be unreasonably large. The possibility of subsidence of the shank into the socket is limited. Therefore, the upper input section of the nest will not be able to move above the upper boundary of such a long recess.

At h / d _m.hv. <0.008, the depth h of the excavation will be insufficient, which will lead to a decrease in the achieved result due to an imperceptible shallow depth. Moreover, with a certain subsidence of the shank and deepening of the recess in the socket during bending of the rod under asymmetric loading of the rod in the recess area, it will come into contact with the upper input edges of the socket, which will also reduce the achieved result.

At h / d _m.hv. > 0.012, the depth of the notch on the rod will be unnecessarily large, since the achieved result will not increase, and the cross section of the rod in the notch area will decrease and reduce its strength characteristics.

 In FIG. 1 shows a General view of the proposed node connecting the rod with the hammerhead; figure 2 node 1 of this connection on an enlarged scale; figure 3 is a known connection node; figure 4 is a conventional diagram of the bending of the hammer rod and the reversal of the falling parts (women with a stamp) with an asymmetric impact of the upper half of the rod against forging; figure 5 schematically shows the elastically deformed state of the upper part of the shank of the proposed rod; Fig.6 is the same, the shank of a known rod.

Designation of positions: 1 rod (upper part), 2 shank (lower part of the rod), 3 woman (stamp holder of the upper stamp), 4 stamp (upper half), 5 stamp (lower half), 6 stamp holder of the lower stamp, 7 piston cylinder hammer work, 8 forgings (figure 4), d ^m.hv. the maximum diameter of the stem shank, l the length of the recess at the lower end of the upper cylindrical part of the stem (to the shank), h the depth of this recess, R is the radius of rounding when moving from the upper border of the stem to the recess; A, B, C, B ₁ and C ₁ designate the points of the outlines of the transition section from the upper border of the shank to the adjacent part of the stem of the proposed connection node in figure 5 and the known node in figure 6.

 The known node connecting the rod with a die tool (prototype) is shown in FIG. 3, proposed in FIG. 1 and 2 and consists of a stem part 1 adjacent to the shank, a shank 2, a woman 3.

 The assembly of the connection unit (both known and proposed design) is carried out so that the cone-shaped shank 2 is inserted into the axial socket (hole) of the woman 3 and hammered with an interference fit to the upper border of the shank.

 During the operation of the hammer with the help of the piston 7 (in the cylinder), the rod with the woman are raised to then lower them down and strike the upper half of the die 4 against the forging 8 located on the lower half of the die 5. Such strokes are repeated several times to completely form the forging.

 The first blows of the stamp on the forging often lead to asymmetric (lateral) loads (due to asymmetric shapes of the initial workpiece). Therefore, the hammer stock may undergo elastic bending deformation (see figure 4).

 With multiple elastic bending deformations of the rod, fatigue microcracks occur, then macrocracks, leading to rod failure.

 Damage to the stem, as is known from practice, most often occurs in a section slightly above the connection node (near the shank).

 To explain and understand the mechanism of microcrack formation leading to breakage, FIG. 6 (where the elastic bending of the rod during asymmetric impact is shown). To explain the slowdown in the formation of cracks in the proposed site is shown in Fig.5.

In FIG. 5 and 6 are shown by a dashed line in the outline of the stem shank zone before the shank is driven into the die holder seat. Points A, B, and C are marked. After driving the shank with an interference fit into the die holder holder at a known node (Fig. 6), the shank 2 is elastically compressed and takes the shape shown by a solid line. In this case, points B and C moved to the place of points B ₁ and C _1, respectively. As can be seen from the drawing, the line AB ₁ C ₁ longer than the line ABC. Therefore, the ABC zone as a result is subjected to stretching, a prestressed state is created even before the start of work. During operation of the eccentric shock load and bending of the rod (as shown in FIG. 4), tensile stresses along the ABC line (AB ₁ C ₁ ) will increase even more. As a result of repeated repetitions of voltage surges, this leads to the appearance of micro- and then macrocracks and, ultimately, to rod failure.

With the proposed node connecting the rod with a woman (Fig. 5) when driving the shank into the socket, the initial outlines (shown by a dotted line) along the line of points A, B, C will take the position (shown by a solid line) of points AB ₁ and C ₁ . The line of points AB ₁ C _{1 is} less than the line ABC. So the zone ABC of the rod is subjected to compression (and not stretching, as in the known node of Fig.6). When the rod bends to the right (Fig. 4), the ABC zone should undergo (as in the previous case) stretching. The pre-compression stress in the proposed site AB ₁ C _{1 is} compensated (removed) with such a bend of the rod. And if the bend creates a greater (over compensation) stress, then all the same it will be significantly less than with a known joint.

 In the case of a bend of the rod to the left, that is, in the opposite direction, unlike the previous one, folding of compressive stresses (including compression from driving the shank into a socket with an interference fit) will occur, which is preferable to tension, since the metal is better able to withstand compressive stresses than tensile ones. Therefore, the stability and durability of the rod with the proposed connection node will increase significantly compared with the known.

Claims (1)

A node connecting the rod to the hammer head containing the stem of the stem located in the axial socket of the head and mating with the socket on a conical surface, characterized in that a recess with a rounded edge facing the conical part is made on the rod at the transition from the conical part to the cylindrical one, while length l and depth h are selected from the relations

where d _{m. x in the} maximum diameter of the shank in its upper part.

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