Integrated roller for a treadmill, method for making and a special-purpose extrusion tool

This invention generally relates to a fitting part for a fitness apparatus, specifically, it relates to an integrated roller for a treadmill, and also to a method for making the same and an extrusion tool for use in the said method.

The existing rollers of treadmill have structures as shown in FIG. 1 to FIG. 12. Referring to FIG. 3, the roller shown contains a steel tube and an iron sleeve, in time of making such rollers, a length of iron sleeve is inlayed into the inner surface of the steel tube to achieve the purpose that the iron sleeve clamps the bearing. Since such a roller includes two parts, the making thereof has to involve more process steps and higher material wastage, and after long time of rolling, the long time squeezing and thus heating up of the iron sleeve by the bearing will make the contact between the iron sleeve and the steel tube gradually become loose, thus increasing the fit clearance between the steel tube and the iron sleeve, and consequently shortening the service life of the roller. To solve this problem, the iron sleeve with cap as shown in FIG. 7 is sometimes adopted commercially, although such manner succeeds in solving the problem of service life, it requires even more process steps and involves even higher material wastage. The process shown in FIG. 11 is to increase the thickness of the steel tube and directly machine the inner surface of the tube into bearing hole to form a plateau; this method reduces process steps, but compared with the process according to this invention, its raw materials cost is 30% higher. As for the processes shown in FIG. 3 and FIG. 7 where more process steps are involved, the raw materials cost is about 15%-20% higher than the process according to this invention.

The technical problem to be solved by this invention is to provide an integrated roller for a treadmill featuring material saving, simple structure and less process steps in making in order to make up the drawback that the making process is relatively complicated of prior art rollers, in addition, this invention also provides a method for making the integrated roller for a treadmill and a special-purpose mold for use in the said method.

To solve the technical problem, the technical scheme adopted in this invention is that an integrated roller for a treadmill is comprised of rollers, the said rollers are of integrated structure with the outer end and the inner end integrated, the outer diameter surface of the said inner end and the inner hole surface of the said outer end form close fit or clearance fit, and the tip of the inner end extends inward along the inner diameter direction for a distance to form a plateau shape.

The said clearance is 0-6 mm.

Inside the said clearance, solid glue or iron ring is configured.

The said roller is of cylinder or cone shape.

To make the above integrated roller for treadmills, the making method according to this invention comprises the following several steps:

a. Firstly prepare raw blank, place the blank on a lower fixed plate, then compact the blank using an upper compaction plate, and then carry out a first-time extrusion to the blank using a female mold; in this way, a steel tube with round end is extruded into a tube with arcuate end, and after the completion of this step, a second step is followed.

b. The second step is to place the blank that has gone through the first-time extrusion on a lower fixed plate, and compact with an upper compaction plate, then carry out inverted extrusion to the blank using a male mold so that the outer diameter surface of the inner end and the inner hole surface of the outer end form close fit or clearance fit; in this way, a half finished product with shape as shown in FIG. 13 and FIG. 17 is formed, and after the completion of this step, the half finished product is further processed to have a plateau for bearing placing by the method of lathe machining or mold extrusion to finish the production of a finished product in this invention.

To allow the formation of close fit or clearance fit between the outer diameter surface of the inner end and the inner hole surface of the outer end in the above method, a special-purpose mold should be used. Such mold includes a male mold and a female mold, the said female mold has a tapering hole configured inside the front end body, the front end of the hole is horizontal, the middle is arc transition section, and the rear end is horizontal; the said male mold has a boss with tapering fillet configured on the front end, at the same time, the boss and the rear end of the male mold are in tapering fillet transition connection.

This invention has the following advantageous effects:

1. The outer end and the inner end are of integrated structure, then when bearing squeezes the inner end of the roller, and the inner end of the roller will transfer the applied force to the outer end, at the same time, the thickness of the end where bearing is installed is one times thicker than before and it\'s a whole body, so the inner end has less tendency to deform, thus the service life is prolonged, besides, the raw material consumption is low and the structure is simple, and according to experiments, it is proved that when the same torque is transferred, this integrated roller is superior to the one shown in FIG. 3, and has the same service life with the ones shown in FIG. 7 and FIG. 11.

2. The tip of the inner end extends inward along the inner diameter direction for a distance, and then when operating, the roller can more effectively fix the bearing and thus improve the practical effect of the product.

3. The outer diameter surface of the inner end and the inner hole surface of the outer end form clearance fit, then when the difference between the outer diameter of the steel tube and the outer diameter of the bearing is too large, the clearance formed at the ends can be utilized to clear up the fit clearance between the outer diameter of the steel tube and the bearing, thus this invention can be used with bearings of different specifications, the practicability of this invention is improved, and better application effect as well as the lower cost are achieved.

4. Inside the ends clearance is configured with solid glue or iron ring, the glue or ring functions to cushion the squeeze applied from the bearing to the inner end, thus allowing the long time service of the product.

5. This invention adopts mold extrusion method for processing, so the process steps are reduced and the cost is saved.

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