GB2064708A - Improved composite gear and method of manufacture - Google Patents

Abstract

In a composite gear 20 or sprocket wheel, the outer toothed portion is formed of a piece of continuously moulded flexible gear belting 24 attached to the rim of the gear or sprocket wheel centre blank or disc. The outer portion is preferably formed as a plastic belt by a well known continuous moulding process. A section of the appropriate length is severed from the endless belt and it is attached by being cemented or snapped into or otherwise fastened to the centre blank for providing the outer toothed or sprocket portion for engaging gears, chains or belts. <IMAGE>

Description

SPECIFICATION Improved composite gear and method of manufacture The present invention relates to composite gears or sprocket wheels. More particularly, the invention relates to such gears or wheels where the outer teeth or sprocket members, for engaging other gears or chains, are formed independently on a gear blank or centre portion and are mounted on the rim of the blank to complete the gear or sprocket.

This invention makes use of known techniques for forming a variety of belts or chains of differing shapes by a continuous plastic extrusion and moulding process. Such belts include teeth or sprocket engaging members formed of a plastic body which is usually reinforced with embedded non-stretchable cable or cording. These belts or chains, with their intregal teeth or chain engaging members, provide an inexpensive and effective outer working surface for the gears or sprocket wheels. The composite gear or sprocket wheel comprises a central gear blank which is easily moulded or otherwise formed of plastic or metal with a smooth or grooved rim to which a section of the belt material is attached. These blanks are rapidly and inexpensively manufactured since they require no precision moulding or machining of the critical tooth or sprocket portions.The belts for forming the teeth or sprockets on the other hand, are easily and inexpensively manufactured by known continuous extrusion moulding processes, wherein a plastic body portion including precisely formed teeth or sprockets are moulded around embedded strengthening members such as metal or fibre reinforcing cords.

Thus, each gear or sprocket in accordance with the invention includes the central gear blank or disc surrounded by an outer working portion comprising a circular section formed of endless belt or chain cut to length and cemented, screwed, snapped or otherwise attached to the blank. The term gear as used herein is mearit to designate such generally similar items as gears, or sprocket wheels or toothed wheels or the like.

Accordingly, an object of the present invention is to provide an improved gear or sprocket wheel or similar drive member.

Another object of the present invention is to provide an improved composite gear or sprocket wheel having a central gear blank surrounded by a toothed or sprocketed portion formed from continuously moulded flexible gear chain or belting.

Another object of the present invention is to provide an improved and inexpensive composite gear or sprocket.

Another object of the present invention is to provide an improved method of forming gears or sprockets inexpensively and with a wide variety of tooth or sprocket configurations.

Another object of the present invention is to provide an improved gear or sprocket having plastic teeth or sprocket members.

Other and further objects of the present invention will become apparent upon an understanding of the illustrative embodiments about to be described or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

A preferred embodiment of the invention has been chosen for purposes of illustration and description and is shown in the accompanying drawings, forming a part of the specification, wherein: Figure 1 is a side elevational view of a continuously moulded belt-like member for forming the outer portions of gears or sprocket wheels in accordance with the present invention.

Figure 2 is a vertical sectional view of the member of Fig. 1 mounted on a gear blank forming a sprocket wheel.

Figure 3 is a side elevational view illustrating a sprocket wheel as illustrated in Fig. 2 in engagement with an endless chain.

Figure 4 is a fragmentary perspective view of a continuously moulded flexible gear belt for use in the gears of the invention.

Figure 5 is a perspective view of a preferred embodiment of a composite gear in accordance with the invention.

Figure 6 is a fragmentary side elevational end view of the gear of Fig. 5 partially in section.

Figure 7 is a fragmentary perspective view of another embodiment of a continuously moulded belt for use with the composite gears of the invention.

Figure 8 is a side elevational view of another embodiment of a continuously moulded belt-like member for use in the gear or sprocket wheels of the invention.

Figure 9 is a vertical sectional view of a sprocket wheel having an outer chainengag- ing member as illustrated in Fig. 8.

Figure 10 is a perspective view of a gear in accordance with the invention illustrating a composite gear having an outer toothed belt member attached by a plurality of screws to an inner gear blank or disc.

Figs. 1 through 3 illustrate one embodiment of a composite sprocket wheel 1 in accordance with the invention and formed by the method of the invention. The composite sprocket wheel 1 includes a central blank or disc 2 having a central hub 3 with the usual shaft mounting hole 4. The rim 5 of the blank 2 is provided with an inwardly directed circular shot 6 for engaging the spaced locking projections 7 formed on the moulded belt-like member 8 as illustrated in Fig. 1. The belt-like member 8 is formed by known extrusion methods where a surrounding plastic body portion 9 is extruded and moulded surrounding an embedded reinforcing cable 10 which is fibre or steel or a combination thereof. The plastic portion may be nylon or polyurethane or other suitable plastics.The belt-like member 8 includes rounded sprockets or teeth 11 shaped for engaging a particular sprocket chain or belt 1 2 of the general type illustrated in Fig. 2. The bottom portion of the belt-like member body 9 has the identical spaced locking projections 7 for engaging the slot 6 in the blank 2. The projections 7 have a generally truncated pyramidal shape as illustrated in Figs. 1 and 2 with a central slot 1 3 providing flexibility for blank mounting and having spaced locking flange portions 14 for engaging the facing circular flanges 1 5 of the gear blank slot 6. The composite sprocket wheel 1 is assembled by cutting a length of the belt-like member 8 to the exact length required to encircle the blank 2.Thereafter, this cut portion is snapped into place in the above described groove 6 with the locking projections 7 holding the short section of the belt-like member 8 in position. While the section of belt 8 may require no additional fastening, it is also possible that the facing ends may be either welded or cemented or otherwise fastened together and to the gear blank 2.

Figs. 4, 5 and 6 illustrate another embodiment more particularly useful as a gear 20 for engaging other gears or appropriately toothed belts or chains. This embodiment employs a generally similar central gear blank or disc 21 having a hub 22 and a mounting hole 23.

Fig. 4 illustrates a portion of a continuously extruded and moulded flexible gear belt 24 having moulded teeth 25. The belt 24 is also formed by known continuous moulding processes and includes a moulded plastic body portion 26 reinforced by a pair of cords 27 of fibre or steel or a combination fibre and steel.

The gear 20 is also assembled by cutting an appropriate length from the belt 24 which will encircle the outer generally cylindrical rim 28 of the gear blank 21 in the manner illustrated in Figs. 5 and 6. In this case, the portion of the belt 24 is cemented or otherwise fastened to the outer rim 28 of the gear blank 21 to form the completed composite gear 20.

Fig. 7 illustrates another embodiment of an extruded belt 30 for use as the outer portion of a composite gear. This also is a flexible moulded belt with teeth 31 similar to a timing belt or other belt and having a moulded plastic body 32 with embedded flexible cords 33. This embodiment has spaced apertures 34 for use with mounting screws or pins for attaching it to a gear blank. It also illustrates another form of tooth having spaced projecting side flanges 35 which are useful in certain applications for acting as side guides for a timing belt or other belt.

Fig. 8 illustrates another embodiment of a belt 40 which has the general form of spur gear stock. The belt 40 has the usual plastic moulded body 41 with reinforcing embedded cords 42 (Fig. 9). Spaced spur teeth or sprockets 43 extend from the body 41 of the belt 40. Fig. 9 illustrates the belt 40 cut to encircle a spur gear blank 44 where the outer portion of the belt 40 is cemented into an appropriate circular groove 45 at the rim of the blank 44.

Fig. 10 illustrates a composite gear 50 employing screw fastenings 51 for holding the outer toothed belt portion 52 in place on a gear blank 53.

It will be seen that an improved composite gear or sprocket wheel has been described which is formed from a novel combination of an extruded belt-like plastic member with a gear blank. This novel combination is particularly advantageous as it permits the inexpensive manufacture of gearing and also permits gears or sprocket wheels to be manufactured with a wide variety of differing sizes, shapes, and specifications as needed and in either large or small numbers are required at a given time for use with other transmission members such as gears, or belts of chains and the like.

As various changes may be made in the form, construction and arrangement of the parts herein without sacrificing any of its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in a limiting sense.

Claims (14)

1. A transmission member comprising the combination of an inner blank having a circular outer rim, a strip of moulded flexible plastic material substantially equal in length to the circumference of said blank rim and fastened thereto and having radially directed force transmitting members for engagement with co-operating members on an interconnected transmission member.

2. The member as claimed in Claim 1 in which said strip of plastic material is a portion of a continuously moulded length of the material of indeterminate length.

3. The member as claimed in Claim 1 in which said strip of plastic material has reinforcing cords embedded therein.

4. The member as claimed in Claim 2 in which said strip of plastic material has longitudinal reinforcing cords embedded therein.

5. The member as claimed in Claim 1 in which said strip of plastic material is cemented to said blank.

6. The member as claimed in Claim 1 in which said strip of plastic material is attached by fasteners to said blank.

7. The member as claimed in Claim 1 in which said blank comprises a slot around its rim and said strip of plastic material has radially inwardly projecting locking members locked in said slot.

8. The member as claimed in Claim 7 in which said locking members and said slot having interlocking flanges.

9. The member as claimed in Claim 1 in which said force transmitting members on said strip of plastic material comprise teeth.

10. The member as claimed in Claim 1 in which said force transmitting members on said strip of plastic material comprise sprockets.

11. The member as claimed in Claim 9 in which said teeth comprise spaced side flanges.

1 2. A composite gear comprising the combination of an inner blank, a circular outer toothed member fastened to said blank and comprising a section of a flexible moulded plastic belt member of indeterminate length.

1 3. The gear as claimed in Claim 1 2 in which said belt member has one or more longitudinal reinforcing cords embedded therein.

14. The gear as claimed in Claim 1 2 in which said toothed member is cemented to said blank.

1 5. The gear as claimed in Claim 1 2 in which said toothed member is attached by fasteners to said blank.

1 6. The gear as claimed in Claim 1 2 in which said blank comprises a slot around its rim and said toothed member has radially inwardly projecting locking members locked in said slot.

1 7. The gear as claimed in Claim 1 6 in which said locking members and said slot have interlocking flanges.

1 8. The gear as claimed in Claim 1 2 in which said teeth comprise spaced side flanges.