JPH0714003Y2 - Flexible casters made of synthetic resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to a synthetic resin swivel caster which is used by being attached to a moving body such as a carriage or a movable chair, and further, in which a ball groove is formed. The present invention relates to a synthetic resin free caster in which a metal race is integrally attached to the caster body.

2. Description of the Related Art In a conventional caster 1 made of synthetic resin, as shown in FIG. 3, a mounting base 2 made of synthetic resin and a caster body 5 made of synthetic resin supporting wheels 6 are bearing balls.
The assembly is completed by utilizing the retaining ring 4 which is rotatably combined via 10 ... And 10 ', and fixed to the mounting base 2 by the set screw 3. A semicircular groove-shaped ball groove having the same diameter in vertically symmetrical arrangement on the upper end of the shaft 5c protruding upward from the center of the upper surface of the caster body 5 and on the lower surface of the mounting base 2 facing it. 5a and 2a are provided, and a large number of bearing balls 10 ... Are inserted in rows in these grooves 5a and 2a. In addition, a ball groove 5b formed on the peripheral side surface of the shaft portion 5c and a lower end inner corner of a cylindrical bearing portion 2c projecting downward from the mount 2 so as to surround the outer periphery of the shaft portion 5c. The ball groove 2b and the ball groove 4a at the upper corner of the inner circumference of the flange portion formed inward from the lower end of the retaining ring 4.
A large number of bearing balls 10 '... Are inserted in a row between them and the caster body 5 is smoothly rotated around a vertical center line with respect to the mounting base 2. US
The universal caster disclosed in the specification of P4,494,271 and the drawings has substantially the same structure as the caster shown in FIG. The basic structure of the universal caster disclosed in Japanese Utility Model Publication No. 54-44920 is similar to that described above, but the ball groove is formed by a metal race.

Problems to be Solved by the Invention (I) In the synthetic resin caster shown in FIG. 3 or disclosed in US Pat. No. 4,494,271 and drawings, the bearing balls 10, 10 'are made of synthetic resin. A large load acts on the mounting base 2 because the mounting base 2, the caster body 5, or the ball grooves 2a, 5a or 2b, 4a, 5b directly provided on the holding ring 4 directly contact the synthetic resin ground surface. In such a case, there is a problem that the hard bearing balls (steel balls) 10 and 10 'are likely to bite into the synthetic resin background surface of the relatively soft ball groove to cause damage or deformation such as dents.

Similarly, when changing the direction of the swivel caster, each bearing ball 10, 10 ′ has a ball groove 2 a, 5 a or 2 b,
5b and 4a are transferred, so due to the friction and frictional heat generated by the transfer, the synthetic resin ground surface of the ball groove that is in direct contact with the bearing balls 10 and 10 'is worn or deformed due to high temperature ( There is a problem that the caster main body 5 is not smoothly rotated with respect to the mounting base 2 due to the occurrence of depression or damage, and in an extreme case, the caster main body 5 is likely to be in a non-rotatable state.

(II) In this respect, the ball grooves 2a, 5a or 2 are provided as in the free caster disclosed in Japanese Utility Model Publication No. 54-44920.
When b, 5b, and 4a are each formed of a metal race that is hard and has excellent wear resistance, the above problems can be greatly improved.
However, as disclosed in Japanese Utility Model Publication No. 54-44920, if each metal race is attached to the ball groove portion one by one, there is no problem in terms of manufacturing technology, but the man-hours are bulky and troublesome. In addition, there is a possibility that the metal race may be separated from the caster body and separated from the caster body due to long-term use, and a long-term stable service life cannot be expected.

(III) Then, for example, in order to form the ball grooves 5a, 5b of the caster body 5 shown in FIG. 3 by an integral metal race, two annular grooves 9a which become the ball grooves as shown in FIG. 4,
It is conceivable to prepare a crown-shaped metal race 9 in which 9b is molded, fit it into the shaft portion 5c of the caster body 5 and integrally mount it. However, the inward protruding portion formed by the annular groove 9b on the peripheral side surface portion of the metal race 9 is an enlarged portion 5d outside the position of the upper end of the shaft portion 5c of the caster body 5, particularly the position indicated by the two-dot chain line a. It becomes a so-called undercut portion 9c, which cannot be fitted at all. As a solution to this, as shown in FIG.
If the enlarged portion 5d of 5c is removed, the metal race 9 has a shaft portion.
Can be fitted to 5c. Therefore, the metal race 9 can be integrally attached and fixed to the shaft portion 5c by stopping the screw 15 from above or fixing the peripheral side surface portion with the pin 21. However, a space 20 is formed in the portion cut at the position indicated by the two-dot chain line (a), causing rattling, and the mounting and fixing state of the metal race 9 is unstable, which makes it uneasy for long-term use. In addition, in the portion adjacent to the space portion 20, the annular groove 9b of the metal race 9 has the bearing ball 1
There is a problem that it is easily deformed by the load received from 0 and 10 '.

Means for Solving the Problems As means for solving the above-mentioned problems of the conventional technology,
As shown in FIGS. 1 and 2 of the drawings, a synthetic resin universal caster according to the present invention has bearing balls 10, 10 'on a synthetic resin mounting base 2 to be mounted on a moving body such as a truck. In a universal caster in which a shaft portion 5c of a synthetic resin caster main body 5 for supporting a wheel is rotatably assembled by using a retaining ring, a cylindrical bearing portion protruding downward from the mounting base 2 A series of metal races 7 from the lower end of 2c to the inner surface and ceiling surface
Are integrally mounted, and the metal race 7 is provided on the ceiling surface and at the lower corners between the inner peripheral surface and the lower end, respectively, to form ball grooves.
7a and 7b are formed.

A shaft portion projecting upward in the center of the upper surface portion of the caster body 5 and fitted into the cylindrical bearing portion 2c of the mounting base 2
A crown-shaped metal race 9 is integrally attached from the upper end surface of 5c to the peripheral side surface, and the metal race 9 forms ball grooves 9a and 9b on the peripheral side surface and the upper end surface, respectively.

A flange portion 4b is formed so as to surround the lower end portion of the cylindrical bearing portion 2c from the lower end portion of the retaining ring 4 fixed to the mounting base 2 inwardly, and the upper surface of the flange portion 4b to the inner peripheral surface are formed. A series of metal races 8 are integrally attached to each other, and a ball groove 8a is formed at the upper corner between the upper surface and the inner peripheral surface by the metal races 8.

Ball groove formed by the metal race 9 of the shaft portion
Bearing balls 10 and 10 are respectively provided between the ball grooves 7a and 7b formed by the metal race 7 of the cylindrical bearing portion 2c and the ball groove 8a formed by the metal race 8 of the retaining ring 4 and 9a and 9b. 'Is interposed.

The crown-shaped metal race 9 forming the ball groove 9b on the peripheral side surface of the shaft portion 5c of the caster body 5 is integrally attached to the shaft portion 5c of the caster body 5 by an insert molding method. To do.

Action Whatever the shape and structure of the shaft portion 5c of the synthetic resin caster body 5 and the crown-shaped metal race 9 attached to the shaft portion 5c, especially if the metal race 9 has the undercut portion 9c, Since it is mounted by insert molding method, it is possible to firmly mount the metal race 9 in a tightly integrated state at the stage of the injection molding process of the caster body 5, and no post-processing such as screwing or pinning is necessary. Absent. Of course, the ball grooves 9a and 9b of the metal race 9 are
There is no danger of being damaged by the bearing balls 10, 10 '.

Embodiment Next, an embodiment of the present invention shown in the drawings will be described.

The basic structure of the universal caster 1 made of synthetic resin shown in FIG. 1 is almost the same as that of the conventional example shown in FIG. A synthetic resin caster body 5 for supporting the wheels 6 and a bearing ball 10, 10 'on a mounting base 2 made of synthetic resin, not shown, which is mounted on a moving body such as a carriage or a movable chair.
And is rotatably assembled using the holding ring 4.

A series of metal races 7 are integrally attached from the lower end surface of the cylindrical bearing portion 2c protruding downward from the mounting base 2 to the inner peripheral surface and the ceiling surface.
And a ball groove 7a at the lower corner between the inner peripheral surface and the lower end surface,
7b is formed.

In addition, the retaining ring 4 which is fastened and fixed to the mounting base 2 with the screw 3
A flange portion 4b is formed inwardly from the lower end of the cylindrical bearing portion 2c to surround the lower end of the cylindrical bearing portion 2c. A series of metal races 8 are integrally attached from the upper surface to the inner peripheral surface of the flange portion 4b. A ball groove 8a is formed in the upper corner between the upper surface and the inner peripheral surface.

A caster body 5 supporting the wheels 6 is projected upward at the center of the upper surface of the caster body 5 and is fitted in the inner portion of the cylindrical bearing portion 2c of the mounting base 2. The shaft portion 5c has a crown shape from the upper end surface to the peripheral side surface. The metal race 9 of is attached integrally,
Ball grooves 9a and 9b are formed on the peripheral side surface and the upper end portion by the metal race 9, respectively.

The bearing ball 10 is provided between the ball grooves 7a and 9a.
, And bearing balls 10 'are also inserted between the ball grooves 7b and 8a and 9b, so that the mounting base 2 and the caster body 5 are assembled in a rotatable relationship.

As each of the metal races 7, 8 and 9 described above, a hard metal thin plate such as a steel plate having a thickness of about 0.4 to 0.6 mm made by a method such as press forming is used.
When the rust prevention of the metal races 7, 8 and 9 is important, a stainless plate, a brass plate or the like is used.

Each of the metal races 7, 8 and 9 is integrally attached to the mount 2, the retaining ring 4 or the caster body 5 by the insert molding method.

By the way, the method of attaching a series of crown-shaped metal races 9 from the upper end surface of the shaft portion 5c of the caster body 5 to the peripheral side surface by the insert molding method is carried out in the manner of the mold structure illustrated in FIG. A metal race 9 having a coronal shape which is produced in advance by a method such as press molding in the same shape as the outer shape of the shaft portion 5c of the caster body 5 is a mold 12 for molding the shaft portion 5c of the caster body 5 injection molding die. And, it is installed in an immovable state inside the slide piece 12 'attached thereto.
After that, the other die 13 is closed, and a molten resin injection process is performed, so that the metal race 9 is attached to the shaft portion 5c.
The caster body 5 integrally formed with is molded. After molding, open the pair of dies 12 and 13 and slide the slide piece.
The caster body 5 that has been molded is taken out by retracting 12 'to both sides. The same insert molding method is applied to the other mounts 2 and the metal races 7 and 8 of the retaining ring 4.

Advantageous Effects of the Present Invention A synthetic resin free caster according to the present invention has a ball groove 7a formed in metal races 7, 8 and 9 integrally attached to a mounting base 2, a retaining ring 4 and a caster body 5, respectively. Bearing ball 1 in 9a or 7b, 8a, 9b
Since 0 and 10 'are transferred and the hard balls (steel balls) do not come into direct contact with the synthetic resin ground surface, even if a large load, vibration, shock, etc. is externally applied to this free caster, it is a hard bearing ball. There is never a risk of wear, damage or dents in the ball grooves caused by 10, 10 '.

Moreover, the crown-shaped metal race 9 forming the ball groove 9b
No matter what the shape and structure of the shaft portion 5c of the caster body 5 itself is, both are simple due to the synthetic resin injection molding process applying the insert molding method that is technically mature. It is securely and integrally fixed, and no trouble such as screwing is required. Therefore, this universal caster is suitable for mass production at low cost. Moreover,
Since the metal races 7, 8 and 9 themselves are also integrated into a tightly bonded state that is difficult to deform, the metal races 7, 8 and 9 themselves exhibit a long useful life.

Similarly, even if frictional heat is generated due to contact between the bearing balls 10, 10 'and the metal races 7, 8, 9 when the direction of the universal caster is changed, the metal races 7, 8, which have good heat transfer properties,
Due to the heat radiation effect of 9, most of the friction heat is immediately dissipated in the air, and the friction heat transmitted to the mounting base 2, the retaining ring 4 and the caster body 5 is small, so that the mounting base 2, the retaining ring 4, the caster body 5 Even if is made of a thermoplastic resin, it will not be melted by frictional heat or deformed at high temperature.

[Brief description of drawings]

1 is a sectional view showing an embodiment of a synthetic resin caster according to the present invention, and FIG. 2 shows a part of an injection molding die in which a metal race is integrated with a caster body by an insert molding method. FIG. 3 is a sectional view showing an example of a conventional caster made of synthetic resin, and FIG. 4 shows a conventional method in which a shaft of a caster body is covered with a separately formed crown-shaped metal race. Explanatory drawing and FIG. 5 are enlarged explanatory views of a state in which a metal race is covered. 2 …… Mounting base 10, 10 ′ …… Bearing ball 6 …… Wheel 5 …… Caster body 5c …… Shaft 4 …… Holding ring 7 …… Metal race 7a, 7b …… Ball groove 9 …… Metal race 9a , 9b …… Ball groove 8 …… Metal race 8a …… Ball groove

Claims (1)

[Scope of utility model registration request] 1. A shaft made of a synthetic resin caster body for supporting a wheel is rotatably assembled using a retaining ring on a synthetic resin mounting base which is mounted on a moving body such as a truck. In the universal caster, a series of metal races are integrally attached from the lower end surface of the cylindrical bearing portion projecting downwardly to the mounting base to the inner peripheral surface and the ceiling surface, and the metal race forms the ceiling surface and the inner surface. A ball groove is formed in each of the lower corners between the peripheral surface and the lower end surface, and a shaft portion projecting upward at the center of the upper surface of the caster body and fitted into the cylindrical bearing portion of the mounting base. A crown-shaped metal race is integrally attached from the upper end surface to the peripheral side surface, and ball grooves are formed on the peripheral side surface and the upper end surface by the metal race. A flange portion having a shape surrounding the lower end portion of the cylindrical bearing portion is formed inwardly from the lower end portion of the holding ring, and a series of metal races are integrally attached from the upper surface to the inner peripheral surface of the flange portion, A ball groove is formed in the upper corner between the upper surface and the inner peripheral surface by the metal race, and is formed by the ball groove formed by the metal race of the shaft portion and the metal race of the tubular bearing portion. Bearing balls are respectively interposed between the ball groove formed by the metal race of the retaining ring and the ball groove formed on the peripheral side surface of the shaft portion of the caster body. A free caster made of synthetic resin, characterized in that the race is integrally attached to the shaft of the caster body by an insert molding method.