JPS6316507Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to thread-shaped molded products such as male threads, feed screws, and worms.

Conventionally, screw-shaped molded products that take advantage of the characteristics of synthetic resins have been manufactured by injection molding. However, when this type of screw-shaped molded product, such as a worm, is manufactured using injection molding, the axis of the worm may become distorted due to molecular orientation of the synthetic resin that occurs during molding, uneven cooling rate, etc. There is a problem that the value may decrease. For this reason, a so-called insert molding method is used in which a metal rod is inserted into a shaft made of synthetic resin.

However, the only way to hold the metal rod within the cavity of the mold during molding is to use the end of the metal rod, and it has been difficult to hold the metal rod strongly and reliably within the cavity. For this reason, the injection pressure when injecting synthetic resin into the cavity tends to cause the metal rod to tilt or bend, and it is difficult to obtain good shaft straightness by inserting the metal rod. Accompanied.

Additionally, when a metal rod is inserted into a synthetic resin shaft, the metal rod prevents the synthetic resin from shrinking in the axial direction, generating large internal stress, which can cause cracks in the shaft and screws. It was hot.

This invention was made in view of the above circumstances, and the purpose is to provide a screw-shaped molded product with good shaft straightness and less likely to cause cracks.

This invention will be explained in detail below with reference to the drawings.

The figure shows a worm as an example of the screw-shaped molded product of this invention, and reference numeral 1 in the figure indicates the worm.

This worm 1 has a metal shaft portion 2 that forms a shaft.
and a threaded portion 3 made of synthetic resin that forms a thread. The shaft portion 2 has a cylindrical shape, and a plurality of recesses 4 are provided on its circumferential surface. The recess 4 is formed to have a predetermined depth and extend in the circumferential direction along the peripheral surface. That is, it is formed along a plane substantially perpendicular to the axial direction. A threaded portion 3 formed on the circumferential surface of the shaft portion 2 has a ring-shaped engagement portion 5 that fits into the recess 4 of the shaft portion 2, and a threaded portion 3 that threads the circumferential surface of the shaft portion 2 in a spiral shape at a constant pitch. It consists of a surrounding spiral part 6. The engaging portion 5 prevents the spiral portion 6 from shifting, and is provided at a pitch 1.5 times that of the spiral portion 6, and the outer circumferential surface of the engaging portion 5 is the same as the circumferential surface of the shaft portion 2. It is considered to be the diameter dimension. The spiral portion 6 has a trapezoidal cross section, and its inner circumferential surface is in close contact with the circumferential surface of the shaft portion 2 and is joined to the engaging portion 5 every 1.5 turns around the shaft portion 2.

To manufacture such a worm 1, the shaft portion 2 is inserted as an insert into a predetermined position in a cavity of a predetermined injection mold and is fixed. When holding and fixing the shaft portion 2, the peripheral surface of the shaft portion 2 that is not covered by the threaded portion 3 is held by a mold. After the shaft portion 2 is fixed in the cavity in this manner, a synthetic resin is injected into the cavity to form the threaded portion 3.

In the case of the worm 1 having such a structure, when the shaft portion 2 is set and held in the cavity of a mold, the shaft portion 2 can be held at any position, so that the shaft portion 2 can be held securely. Therefore, the shaft portion 2 does not tilt or bend due to the injection pressure when forming the threaded portion 3, and the straightness of the worm 1 can be improved.

Also, an engaging portion 5 that locks the threaded portion 3 to the shaft portion 2 is provided.
The axial position of ... is the recess 4 of the metal shaft 2.
It is determined by ... and is not affected by molding shrinkage. For this reason, the spiral portion 6 that joins the engaging portion 5 is prevented from molding shrinkage in the direction of the helical winding, and the pitch of the spiral portion 6 is therefore cut into the cavity of the mold. Since the pitch is faithfully transferred, this worm 1 has good pitch accuracy of the screw thread.

In particular, in the thread-shaped molded product of this example, since the recesses 4 are provided at the same intervals, the accuracy of the thread pitch is further improved.

Furthermore, the screw-shaped molded product of this invention has a spiral portion 6
is intermittently fixed to the shaft part 2 via the engaging part 5, so the spiral part 6 between the engaging parts 5, 5 is in a state where it is in close contact with the shaft part 2 but not fixed and deformed. It becomes possible. Therefore, the stress generated in the spiral portion due to molding shrinkage is alleviated, and the occurrence of cracks in the spiral portion is prevented. Furthermore, the risk of cracks occurring due to external forces is also prevented.

Furthermore, the worm 1 has an entire shaft portion 2
Since the shaft is formed by the metal rod, it can have a larger diameter than the metal rod that is conventionally inserted into the shaft, and therefore the strength of the shaft is improved.

In addition, in the above explanation, the worm 1 was shown as an example of the screw-shaped molded product, but the worm 1 is not limited to this.
It can also be used for male threads, feed screws, bolts, etc. in which threads are spirally provided on the circumferential surface of a cylindrical, conical, or cylindrical shaft.

Further, the cross-sectional shape of the spiral portion 6 may be a semicircular shape, a triangular shape, etc. other than a trapezoid, and further,
One part of the spiral part 6 may have a different shape from the other, for example, hemispherical convex parts may be provided at predetermined intervals on the outer peripheral surface of the spiral part 6 shown in the figure.

Furthermore, since the shaft portion 2 can have a large diameter,
In addition to metal, materials with low rigidity such as synthetic resin can also be used.

In addition, although the above embodiment shows a screw-shaped molded product in which the recesses 4 are provided at regular intervals, the recesses 4...
The intervals between the two do not necessarily have to be constant and can be changed as necessary. For example, when the shaft portion 2 is conical, it is desirable to gradually change the intervals between the recesses 4 in order to fix the spiral portion 6 at constant intervals in the helical winding direction. Further, in cases where the pitch accuracy of the screw threads is not so required, the interval between the recesses 4 may be arbitrarily changed with reference to the force applied to the spiral portion 6 during use.

As explained above, the screw-shaped molded product of this invention has a shaft portion in which recesses are formed at multiple locations on the circumferential surface along a surface substantially perpendicular to the axial direction, and a locking member that fits into the recesses of the shaft portion. The threaded portion made of synthetic resin, which has an engaging portion and a spiral portion formed integrally with the engaging portion, is provided by injection molding, so when manufacturing by injection molding, the shaft portion is It can be securely held within the mold cavity. Therefore, the screw-shaped molded product of this invention is of high quality with excellent shaft straightness.

In addition, in the thread-shaped molded product of this invention, the spiral portion is intermittently fixed to the shaft portion via the engaging portion, so that the spiral portion can be deformed. Therefore, the stress generated in the spiral portion due to the difference in the amount of shrinkage during cooling after molding is alleviated, and the occurrence of cracks in the spiral portion is prevented.

[Brief explanation of the drawing]

The figure is a schematic sectional view showing an example of the screw-shaped molded product of this invention. DESCRIPTION OF SYMBOLS 1... Worm, 2... Shaft part, 3... Threaded part, 4... Recessed part, 5... Engaging part, 6... Spiral part.

Claims (1)

[Scope of utility model registration request] A shaft portion having recesses formed at multiple locations on the circumferential surface along a plane substantially perpendicular to the axial direction, an engaging portion that fits into the recesses of the shaft portion, and a spiral formed integrally with the engaging portion. A thread-shaped molded product in which a synthetic resin threaded part having a part is provided by an injection molding method.