JPS6297819A - Screw for injection molder - Google Patents

Abstract

PURPOSE:To realize the installation and fixation of a screw head to a screw main body excluding by joining with thread by a method wherein annular grooves are provided on the peripheral surfaces of the fitting part of the screw main body and the screw head, the diameter of the shaft-shaped fitting part of which is made to be gradually reduced from the annular groove to the tip, and an elastic ring is fit in both the annular grooves. CONSTITUTION:First, a snap ring 4 is fitted to the annular groove 53 of a fitting hole 51. Secondly, when a screw head 3 is inserted from an engaging projection 36 side into the fitting hole 51 of a screw main body 5, the screw head 3 enters while expanding the snap ring 4 by a conical end 37 until the engaging projection 36 of the screw head 3 fits to the engaging hole 52 of the screw main body 5, and consequently the screw head 3 and the screw main body 5 engages with each other under the state that no relative rotation is possible between them. At the same time, the snap ring 4 contracts itself by means of the spring force of its own so as to fit in both the annular grooves 25 and 53 in order to join the screw head 3 and the screw main body 5 under the state no relative shifting in the axial direction is possible between them.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a ceramic screw for an injection molding machine, and particularly to a screw in which a screw head is attached and fixed to a screw body without using a screw connection.

In conventional injection molding machines, screws with screw heads corresponding to the injection materials are used to knead, measure, and inject various injection materials. For this reason, the screw is composed of a screw body and a separate screw head, and various heads such as a head with a backflow prevention ring and a standard head without a ring can be selectively attached to the screw body.

Furthermore, in the case of a head with a backflow prevention ring, the backflow prevention ring is interposed between the screw body and the screw rad, so the screw body and the screw head must be provided separately.

Due to the above-mentioned circumstances, conventionally, a threaded hole is provided in the distal end of the screw body in the axial direction, and a screw is formed on the base end of the screw head, which is separate from the screw body, to be threaded into this threaded hole. The screw head is screwed into place.

On the other hand, screws are exposed to high temperatures and pressures during crosstalk, metering, and injection, causing friction with the injection material and being corroded by the molten injection material, so they must be made of materials with excellent heat and wear resistance. In some cases, it may be desirable to use ceramic as a material of construction. However, ceramic has poor workability, and when the screw is made of ceramic, it is difficult to realize the configuration in which the screw head is screwed onto the screw body as described above.

Problems to be Solved by the Invention An object of the present invention is to provide a ceramic screw for an injection molding machine in which the screw head can be attached and fixed to the screw body without screw connection. .

Means for Solving the Problems In the screw for an injection molding machine of the present invention, a fitting hole into which a screw head is fitted is bored at the tip of the screw body, and the screw head has a fitting hole and a screw head. A shaft-like fitting portion to be fitted is provided, and an annular groove is provided on the circumferential surface of the shaft-like fitting portion, and the shaft diameter is configured to gradually decrease from the annular groove toward the distal end of the annular fitting portion. An elastic ring is engaged between the annular groove and the annular groove provided on the wall surface of the fitting hole, and an engaging part that is fitted in the fitting hole and the shaft-like fitting part so as not to rotate relative to each other is provided. It consists of the configuration provided.

After fitting the elastic ring into the annular groove formed on the wall of the fitting hole of the screw body, when the screw head is pushed into the fitting hole of the screw body, the shaft diameter will increase in the direction of the tip of the annular fitting part of the screw head. The elastic ring moves forward while expanding its diameter at the part where the diameter gradually decreases, and when it reaches the axial position where the annular groove provided in the shaft-shaped fitting part and the annular groove provided in the fitting hole wall surface are aligned in the axial direction. The elastic ring contracts into the annular groove of the annular fitting and engages both annular grooves. As a result, the screw head and the screw body are made immovable relative to each other in the axial direction via the elastic ring, and also become immovable relative to each other due to the engagement of the engagement portion that makes relative rotation impossible. After all, the screw head is installed and fixed simply by fitting the elastic ring into the annular groove of the fitting hole and then pushing the screw head into the screw body.

Example Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a screw for an injection molding machine according to an embodiment of the present invention. The screw 1 includes a screw head 3 fitted with a backflow prevention ring 2, and a snap ring 4 made of spring steel as an elastic ring. It is fixed to the screw body 5 via.

The screw body 5 is made of ceramic, and a bottomed fitting hole 51 is bored along the axis at the tip thereof, and a fitting having a rectangular cross section, for example, coaxially with the fitting hole 51 is formed on the bottom surface of the fitting hole 51. A matching hole 52 and an annular groove 53 for fitting the snap ring 4 are formed on the inner peripheral surface of the intermediate portion. Reference numeral 54 denotes a screw ridge formed over substantially the entire length of the screw body 5.

The screw head 3 is made of ceramic and has a conical tip 3.
1. It is integrally constituted by a cylindrical intermediate part 32 and a shaft-shaped fitting part 33 into which the ceramic backflow prevention ring 2 is loosely fitted. An annular groove 35 for accommodating the snap ring 4 is formed at a position in the axial direction that faces the annular groove 53 when the screw body 5 comes into contact with the distal end surface of the screw body 5.

Further, at the other end of the fitting portion 33, a prismatic engagement protrusion 36 that fits into the engagement hole 52 of the screw body 5 is protruded. conical end 37 of
is formed.

As shown in Fig. 2, a snap ring 4 made of spring steel
In a free state, it has an elongated arc shape with both ends spaced apart in plan view, and has a center diameter D that is approximately the same as that of the fitting hole 51, and is capable of expanding in diameter under a pressing force.

To assemble the screw 1 having the above-mentioned configuration, first, the snap ring 4 is fitted into the annular groove 53 of the fitting hole 51, and the screw head 3, in which the backflow prevention head 3 is fitted into the cylindrical intermediate part 32, is inserted at one end, that is, When inserted into the fitting hole 51 of the screw body 5 from the engaging protrusion 36 side, the screw head 3 is fitted while pushing and expanding the snap ring 4 by the conical end 37, and the engaging protrusion 36 of the screw head 3 is inserted into the fitting hole 51 of the screw body 5.
is inserted into the engagement hole 52 of the screw body 5, and the screw head 3 and the screw body 5 are engaged with each other so that they cannot rotate relative to each other. When the stepped end surface 34 of the screw head 3 comes into contact with the distal end surface of the screw body 5, the snap ring 4 engages with the annular groove 35, and the annular groove 35 of the screw head 3 and the screw body 5. 53 are aligned in the axial direction, the snap ring 4 that was engaged in the annular groove 53 contracts in diameter due to its spring force, opening the annular groove 35°5.
3, and connects the screw head 3 and the screw body 5 so that they cannot move relative to each other in the axial direction.

The screw 1 assembled as described above is incorporated into an injection device of an injection molding machine, and performs crosstalk, metering, and injection operations. During injection, the backflow prevention ring 2 slides to the right in Fig. 1 under the reaction force of the injection force applied to the injection material, as is conventionally known, and seats on the tip surface (valve seat) of the screw body. , prevent backflow of injection material.

In the above embodiment, both the screw head 3 and the screw body 5 are made of ceramic, and the backflow prevention ring 2 is attached. However, in the present invention, one or both of the screw head 3 and the screw body 5 is made of a material other than ceramic, for example. It can also be applied to a screw made of special steel or a screw without a backflow prevention ring 2.

Effects of the Invention As described above, according to the present invention, the screw body and the screw head can be coupled via the elastic ring by simply pushing the axial fitting portion of the screw head into the fitting hole of the screw body. , the screw head can be securely attached to the screw body with one touch. Moreover, since there is no need to form threads on the screw head and screw body as in the past, it is possible to solve the problem of coupling the screw head and screw body that occurs when the screw is made of ceramic, which is difficult to cut. The screw head and screw body can be separated even in the case of screws made of ceramics, so in addition to enjoying the high heat resistance and high wear resistance associated with the use of ceramic, various screw heads including backflow prevention rings can be attached to the screw body. Screws that are compatible with various injection materials can be easily provided by simply using the following method.

[Brief explanation of drawings]

FIG. 1 is a partial schematic sectional view showing a screw for an injection molding machine according to an embodiment of the present invention, and FIG. 2 is a plan view of the snap ring shown in FIG. 1. 1...Screw, 2...Backflow prevention ring, 3...
・Screw head, 4...Snap ring, 5...
・Screw body, 33...Shaft-like fitting part, 35.53
... Annular groove, 51 ... Fitting hole. Fig. 1 Fig. 2 1 varnish screw 33 2 Axis #1 strange part 4: Snatch 7 sug 5 varnish screw 43 pieces

Claims (2)

[Claims] (1) In a screw for an injection molding machine in which a screw head is attached to a screw body, at least one of the screw body and the screw head is made of ceramic, and the screw head is fitted to the tip of the screw body. A fitting hole is bored, and the screw head has a shaft-shaped fitting part that fits into the fitting hole,
An annular groove is provided on the circumferential surface of the axial fitting part, and the shaft diameter is configured to gradually decrease from the annular groove toward the distal end of the axial fitting part, and the annular groove and the wall surface of the fitting hole A screw for an injection molding machine, wherein an elastic ring is engaged between an annular groove provided in the screw, and an engaging portion is engaged with the fitting hole and the shaft-shaped fitting portion in a manner that prevents relative rotation. (2) The engaging portion includes an angular engaging protrusion provided at the tip of the shaft-like fitting portion and a rectangular engaging protrusion provided on the bottom surface of the fitting hole that engages with the engaging protrusion. The screw for an injection molding machine according to claim 1, wherein the screw is constituted by a matching hole.