JPH0611155Y2 - Split nut for mold clamping device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a split nut applied to a mold clamping device such as an injection molding machine or a die casting machine.

(Prior Art) A split nut for a mold clamping device is applied to, for example, a mold clamping device of an injection molding machine, and plays a role of locking a mold so as not to open during mold clamping.

This type of mold clamping device is composed of a die head having a fixed mold and a platen having a movable mold, and the molds are opposed to each other to move the platen toward and away from the die head to open and close the mold. Usually, one end of a tie rod is fixedly attached to the platen at four corners, and the protruding end of each tie rod is inserted into through holes provided at the corresponding four corners of the die head. A semi-divided split nut that is openable and closable is attached to the die head on the side opposite to the die of the through hole.The split nut is closed at the time of mold clamping and meshes with the threaded portion of the tie rod end inserted into the die head. It performs the tightening and locking functions and opens when the mold is opened to allow the axial movement of the tie rod.

The structure of a conventional split nut for a mold clamping device having such a function is shown in FIGS. 6 to 8.

In these figures, 1'is a split nut, 2 is a tie rod, and Figs. 6 and 8 show a state in which the split nut 1'is closed and meshes with the tie rod 2. This split nut 1'has a shape obtained by splitting a normal nut into two, and is in a closed state at the position shown by the solid line in FIG. 7 and opened at the position shown by the alternate long and short dash line. It is in a state.

However, in the conventional split nut 1'for mold clamping device, as shown in Fig. 8, screws with the same pitch are used to firmly mesh with the tie rods 2 over the entire surface. The reaction force of the tie rod against this tightening load acts on each tooth of the split nut, and at this time, the load tends to concentrate near the nut seat surface, especially the 1st to 5th teeth from the seat surface. In particular, the first tooth is the largest and the stress is severe.

(Problems to be Solved by the Invention) FIG. 9 is a diagram showing a load sharing mode of each tooth at the time of mold clamping of a split nut for a mold clamping device having a conventional equal pitch screw structure. In the figure, the solid line indicates the value of the load applied to each tooth based on the design calculation, and the broken line indicates the actual load sharing of each tooth based on the error during manufacturing.

As is clear from the figure, in the case of the screw structure of equal pitch, most of the load at the time of mold clamping is shared by the first to fifth first half teeth from the seat surface. Among them, especially the first tooth has a large load sharing rate and is in a severe stress condition.

The present invention has been made in order to eliminate such a problem, and the load sharing of each tooth during tightening is averaged to the latter half teeth of the split nut, and the load sharing of the first half tooth where the load concentration occurs occurs. The load mode of each tooth is set so as to reduce the load.

(Means for Solving the Problem) Therefore, the present invention is a split nut for a mold clamping device, which is composed of two or more divided pieces and which is closed during mold clamping and meshes with a tie rod to provide a mold clamping lock function. Are formed by parallel grooves of unequal pitch, and this is a means for solving the above problems.

That is, according to the present invention, firstly, the tooth surface of the split nut is formed in a parallel groove with zero lead. A load sharing mode is set so as to reduce the load sharing of the teeth in the first half where the stress concentration is large, and the groove interval (pitch) is changed according to the mode.

Here, the teeth of the other tie rod that meshes with the split nut are naturally parallel teeth, but the pitch of each tooth of the tie rod is set to be the same.

(Operation) By changing the pitch of the parallel teeth of the split nut, the amount of bending due to the load of each tooth changes, and the load sharing of each tooth changes. The present invention changes the pitch of each tooth so as to obtain a desired load sharing mode so that stress is not concentrated on some teeth.

(Embodiment) Hereinafter, the present invention will be described more specifically based on the illustrated embodiment.

1 to 3 show a split nut structure according to an embodiment of the present invention. FIG. 1 is a side sectional view for explaining a load direction acting on the split nut and a tie rod during mold clamping, and FIG. FIG. 3 is a cross-sectional view showing the opened / closed state of the split nut, and FIG. 3 is a partially enlarged view showing the meshed state of the split nut and the tie rod.

The split nut 1 according to this embodiment is a tie rod 2 with a parallel groove.
By adopting a meshing part with and by changing the pitch of each tooth of the parallel groove, the amount of bending due to the load of each tooth is changed, and the load sharing mode is set to the target mode.

According to the illustrated embodiment, as shown in FIG.
~ 15th tooth) makes the pitch almost the same and performs load sharing evenly, and for the first half teeth (1st to 5th teeth) where concentrated load occurs, set a large pitch to reduce load sharing. I am doing it.

As a result, the concentrated load that has been conventionally applied to the first tooth can be dispersed, and the stress generated at the mold clamping load in each tooth can be reduced to improve the reliability.

In addition, in this embodiment, the unequal pitch is set, for example, between the third to fifteenth teeth from the seat surface, and the maximum pitch adjustment amount is set to a range of 0.01 mm to 1% with respect to the tie rod pitch, and The load sharing mode is set as the target mode.

FIG. 5 shows a schematic configuration when the split nut of the present invention is applied to a mold clamping device in an injection molding machine.

The split nut 1 has a structure in which it is meshed with the tie rod 2 by a parallel groove.

The tie rod 2 is attached to the platen 8 by a tie rod attachment nut 7. Male and female dies 6 are attached to the platen 8 and the die head 9, respectively.
Is moved to the die head 9 side to clamp the die 6.

After the split nut 1 is meshed with the tie rod 2, the hydraulic ram 3 is moved by pouring the hydraulic oil into the hydraulic cylinder chamber 4 from the hydraulic oil inlet 5 to move the split nut 1 into the tie rod 2.
Push in the axial direction while engaging with. As a result, the platen 8 to which one end of the tie rod 2 is fixed is pulled toward the die head 9, and the platen 8 and the die 6 sandwiched between the die head 9 are tightened. At this time, the pitch is changed so that a part of the load applied to the teeth of the split nut 1 near the seat surface is changed to a mode in which the load is applied to the teeth far from the seat surface. Thus, the load is averaged over all teeth, and the stress distribution in the axial direction of the split nut 1 becomes uniform.

(Effect of the Invention) As described above in detail, according to the present invention, since the teeth of the split nut are formed by parallel grooves and the pitch of each tooth is changed so as to be in a predetermined load mode, the load sharing is achieved. It is possible to concentrate the load on the teeth near the seat surface, which has a large variation compared to other teeth, and to distribute the load evenly on the part away from the seat surface. Can hold the load.

Further, in the present invention, since the tooth contact surface is a parallel surface, it is possible to suppress the variation in load sharing due to the deviation of the shaft center of the bolt and the nut.

[Brief description of drawings]

1 to 5 relate to the present invention, in which FIG. 1 is a vertical sectional view showing a load direction with respect to a split nut and a tie rod when a mold is clamped, and FIG. 2 is a cross sectional view showing opening and closing of the split nut. , FIG. 3 is an enlarged view of a partial vertical section showing a meshing state of the split nut and the tie rod, FIG. 4 is a tooth load sharing mode diagram at the time of mold clamping, and FIG. 5 shows the present invention applied to an injection molding machine. 6 to 9 show a conventional example, FIG. 6 is a longitudinal sectional view showing a load direction with respect to a split nut and a tie rod when a mold is clamped, and FIG. FIG. 8 is a partial vertical cross-sectional enlarged view showing the meshing state of the split nut and the tie rod, and FIG. 9 is a tooth load sharing mode diagram during mold clamping. Description of main parts of the drawing 1 ... Split nut, 2 ... Tie rod 3 ... Hydraulic ram, 4 ... Hydraulic cylinder chamber 6 ... Mold, 8 ... Platen 9 ... Die head

Claims (1)

[Scope of utility model registration request] 1. A split nut for a mold clamping device, which is composed of two or more divided pieces and is closed during mold clamping and meshes with a tie rod to perform a mold clamping lock function, wherein tooth surfaces are formed by parallel grooves of unequal pitch. Split nut for mold clamping device characterized in that