METHOD OF SPINNING A PULLEY FROM A TUBULAR BLANK

Abstract: The invention comprises a method of spinning a pulley using a tubular blank. A tubular blank (B) is placed in a spinning machine mandrel (10). The hub (14) is formed by spinning down, or inward, one end of the tubular blank, while leaving the other end as a cup for either spinning a pulley or sprocket profile. This process results in natural thickening of metal at the hub by maintaining a constant volume of metal while reducing the diameter of the tube during the spinning process.

Description: Title Method of Spinning a Pulley From A Tubular Blank Field of the Invention The invention relates to power transmission pulleys, and more particularly to a method of spinning a pulley from a tubular blank. Background of the Invention Pulleys and sprockets are widely known and used as a means of transmitting power between shafts. Power transmission pulleys are made in several ways. Sheet metal types are fabricated by spinning or cam dies. In this method, the belt profile is formed in a radial motion of the die to the blank. Representative of the art is U.S. patent no. 4,840,607 (1989) to Hitchcock et al. which discloses a spun formed poly-v belt pulley formed with a "can-shaped" blank by compressing material in a groove formation area along a side of the blank. This invention does not afford flexibility on the thickness of the hub area nor is it a one step process. The prior art also relies on the can-shaped blank having a proper pre-formed thickness for the web. The pulleys are simply pressed into shape with existing pre-form web thickness. Further, the pre-form requires a forming step that precedes the spinning step, adding cost to the finished part. Other prior art pulleys rely on horizontal forming, for example as shown in U.S. patent no. 5,987,952, which does not afford the most advantageous plastic flow of the sheet metal for the application described herein. The process relies on spinning the metal on the face of a round blank from the outside to the middle, until the gathered metal is formed around a central post to form the hub. This process requires a certain diameter for the part and its blank to make it possible to gather the required volume of metal. For parts having a small diameter or a very long and or thick hub, there is not enough surface area to gather the required volume of metal . What is needed is a method of spinning a pulley using a tubular blank. What is needed is a method of spinning a pulley from a tubular blank by gathering metal inwards toward a hub end of a tubular blank. What is needed is a method of spinning a pulley using a tubular blank that affords inwardly gathering a higher volume of gathered metal. The present invention meets these needs. Summary of the Invention The primary aspect of the present invention is to provide a method of spinning a pulley using a tubular blank. Another aspect of the invention is to provide a method of spinning a pulley from a tubular blank by gathering metal inwards toward a hub end of a tubular blank. Another aspect of the invention is to provide 'a method of spinning a pulley from a tubular blank that affords inwardly gathering a higher volume of gathered metal . Other aspects of the invention will be pointed out or made apparent by the following description of the invention and the accompanying drawings . The invention comprises a method of spinning a pulley using a tubular blank. A tubular blank is placed in a spinning machine mandrel. The hub is formed by spinning down, or inward, one end of the tubular blank, while leaving the other end as a cup for either spinning a pulley or sprocket profile. This process results in natural thickening of metal at the hub by maintaining a constant volume of metal while reducing the diameter of the tube during the spinning process. A desired profile is then spun into the rim of the pulley. Brief Description of the Drawings Fig. 1 depicts a cross-sectional view of a tubular blank. Fig. 2 depicts a cross-sectional view of a tubular blank on a mandrel . Fig. 3 depicts a cross-sectional view of a form roller as it forms a tubular blank. Fig. 4 depicts a cross-sectional view of a fully formed pulley. Description of the Preferred Embodiment of the Invention Fig. 1 depicts a cross-sectional view of a tubular blank. The tubular member or blank comprises a cut piece of tube, pipe, or a deep drawn cup with the bottom punched out. The tubular blank has a length L, diameter Di, and thickness Ti. Fig. 2 depicts a cross-sectional view of a tubular blank on a mandrel. The process begins by placing the tubular blank B on an appropriately sized mandrel 10. The diameter Di may be sufficient to create a slight interference fit between blank and the mandrel, or the blank may be clamped to the mandrel by means known in the art. The mandrel and blank are then rotated by headstock 10. Form roller 12 is moveable radially and axially by equipment known in the art in order to properly form the blank. To form the pulley, the mandrel is rotated. The form roller is moved into contact with the side of the tubular blank at a location chosen by the operator. As the form roller moves inwardly, the metal is gathered in a steadily decreasing diameter at a hub location about the tailstock. Since the volume of metal is unchanged by the process, the decreasing diameter causes the hub portion to thicken as the form roller moves inward. Fig. 3 depicts a cross-sectional view of a form roller as it forms a tubular blank. Form roller 12 is shown moving in an inward radial direction Mi. As the form roller moves inward, the metal is gathered ahead of the form roller, thereby creating hub 14 as the diameter D 2 of the hub 14 is progressively reduced. The metal is gathered and the hub is formed about tailstock 11 as the form roller continues to move inward. Form roller 12 may follow the contour 15 of the mandrel 10 in order to give proper form to the finished part. It may also taper the profile of the web as required by a user, resulting in tapered profile that thickens from the rim toward the hub area. The path of the form roller may also be axially adjusted as it moves inward in order to vary the thickness of the web 17. In this manner, a web thickness may be tapered, varied, or held constant as required by a user. Web 17 may also be spun into a concave or combination or concave/convex shapes to further strengthen the web. Fig. 4 depicts a cross-sectional view of a fully formed pulley. The inside diameter D 3 of the hub is determined by the width of the tailstock 11. The gathered metal at hub 14 has thickness T 2 , which is significantly greater than the initial thickness Ti. To finish the hub, finishing roller 13, moved in direction M 2 , is then used to shape the final form of hub 14. The final form or shape of hub 14 is made by the profile of the finishing roller. Finishing roller 13 may have any profile required by a user that is known in the art. Hub thickness may be kept at T 2 , or it can also be reduced to thickness T 3 , to form a puller. Once the part is formed, it is removed from the mandrel for final shaping of the rim or belt bearing surface 16 as required by a user. A shaping roller (not shown) is used to shape the belt bearing surface. The belt bearing surface may be given a v-belt profile, a multi-ribbed profile, or any other profile known in the art by metal forming means. Although a single form of the invention has been described herein, it will be obvious to those skilled in the art that variations may be made in the construction and relation of parts without departing from the spirit and scope of the invention described herein.

Claims: Claims I claim: 1. A method of spinning a pulley comprising the steps of: forming a tubular member having a length and a tubular member diameter and an initial thickness; spinning the tubular member with a mandrel; pressing a forming roller against a side of the tubular member; moving the forming roller radially inwardly against the tubular member; decreasing the tubular member diameter along a length portion; gathering inwardly displaced metal about a tailstock at a hub location; terminating movement of the forming roller; and retracting the forming roller. 2. The method of spinning a pulley as in claim 1 further comprising the step of: terminating movement of the forming roller when the hub has a thickness in excess of the initial thickness. 3. The method of spinning a pulley as in claim 2 further comprising the step of: pressing a finishing roller against the hub to form a hub shape and a thickness. 4. The method of spinning a pulley as in claim 3 further comprising the steps of: pressing a shaping roller against an outer belt bearing surface of the tubular member; and moving the shaping roller to form a profile on the outer belt bearing surface.

Inventors: HODJAT YAHYA, HODJAT, YAHYA
Applicants: GATES CORP, THE GATES CORPORATION
Application year: 2001
Main classification: B21D53
IPC codes: B21D22, B21D53