US2413817A - Sheave - Google Patents

Description

D. FIRTH 2,413,817

Jan. 7,1947.

SHEAVE Filed Feb. '5, 1945 I I INVENTOR. lYQZJLZJZrZ /W,

Patented Jan. 7, 1947 SHEAVE David Firth, South Bend, Ind., assignor to Dodge Manufacturing Corporation, Mishawaka, Ind., a corporation of Indiana Application February 5, 1943, Serial No. 474,830

Claims.

Sheaves for multiple V-belt drives should have accurately formed belt'grooves the side walls of which should be uniformly wear-resistant. Wear resulting in. material enlargement of the belt grooves is objectionable as altering established pitch diameters. Unequal wear of the belt grooves would be especially objectionable as interfering with the important objective of maintaining the rubber driving belts equally tensioned and therefore in engagement with the sheaves at uniform distances from the sheave axes.

For conservation of metal, it is desirable to utilize wood or other suitable non-metallic material for the construction. of such sheaves. Wood sheaves of suitable construction can be used uncler many conditions for duties for whichcast iron sheaves of corresponding sizes have been commonly employed. The wood sheaves are of relatively light weight, which is importantly advantageous in transportation. Furthermore, the wood sheaves can be driven at faster speeds than the cast iron sheaves without going to pieces by centrifugal force. However, the wearing qualities of wood sheaves are generally interior to those of cast iron.

Sheaves having tractive surfaces of hard wood transverse of the grain thereof are satisfactorily wear-resistant under ordinary conditions; how ever the fabrication of wood sheaves so as to dispose the grain of the wood transversely of the tractive surfaces for substantially or nearly the entire circumference necessitates special shaping and arrangement of wood pieces, increasin labor and cost of production. Unless so fabricated, a wood sheave is liable to wear unevenly, due to presence of soft spots or inequalities of hardness in its tractive surfaces. Moreover a wood sheave is liable to wear down rapidly it operated in the presence of abrasive dust or used under conditions such as to be affected by grit between the driving belts and walls of the sheave grooves.

It is therefore desirable to provide a wood sheave with groove walls having hard metal wear surfaces. The present invention provides such a sheave of practicable character, readily and economically producible in desired forms and sizes.

A sheave embodying the invention ,is characterized by a sheave body of wood or other suitable non-metallic material having a metallic skinlike coating formed on, covering and bonded to the perimeter thereof and providing circumferentially continuous groove wall liners, the exterior of the coating or belt-engaging portions thereof being ground or machined and ground to provide smooth tractive surfaces. Thus the invention gives the advantage of a relatively light construction of non-metallic material with the wearing qualities of a metallic sheave. Further advantages of the invention will be hereinafter 7 indicated.

In the accompanying drawing, there is shown for illustration a, multiple V-belt sheave of one practicable construction embodying the invention.

Fig. 1 is a section of the illustrative sheave taken on a plane longitudinally of and through the sheave axis.

Fig. 2 shows a fragment of the rim portion of the sheave partly in section and partly in end elevation, this view being a portion of that shown on a reduced scale in Fig. 3.

Fig. 3 on a reduced. scale shows the sheave half in cross section on the line 3-3 of Fig. 1 and half in end elevation.

Fig. 4 is a diagrammatic representation in section of an enlarged fragment of the rim portion of the sheave.

In the drawing, I designates as a whole a laminatecl wood sheave body the perimeter of which is formed to provide annular'belt grooves 2 of V-shaped cross section. Formed on and covering the perimeter and lining the walls of the belt grooves is a hard skin-like coating 3 of ferrous metal or other suitable metallic material, the coating being bonded to the wood material of the body perimeter by engagement of numerous minute portions of the metallic coating in pores or interstices of the wood. The coating conforms in exterior shape substantially to the contour of the body perimeter, and, as best shown in Fig. 4, the portions of the coating lining the side walls of the belt grooves are ground to provide smooth surfaces for engagement by the V-belts, these being conical surfaces concentric with and of the same slant as the corresponding surfaces providing the side walls of the body grooves.

The coating may be formed by spraying atomized or finely divided molten of semi-molten particles of metal on the perimeter of the wood sheave body and on the film of such particles so deposited until there is built up a coating of desired thickness. This involves utilization of a method which is in industrial use for the coating of metal surfaces to provide corrosion-resistant and wear-resistant coatings and which has also been applied to the coating of glass, paper and wood for ornamentation. The method is carried out with the use of known apparatus including a spray gun through the nozzle of which is fed at a constant rate a wire' composed of the metal to supply the coating material. Concentric chambers of the spray gun are connected respectively with sources of oXy-acetylene gas, oXy-hydrogen gas and compressed air. At the nozzle of the spray gun the wire is melted by an oXy-acetylone or oXy-hydrogen flame and as it melts is subiected to a blast of compressed air, whereby the molten or melting metal is atomized and sprayed off. As the finely divided molten or semi-molten metal particles strike the wood surface of the sheave body perimeter, they rapidly chill and solidify, becoming bonded to said perimeter by keying in surface pores or interstices of the wood, and bonding and integrating with successively deposited particles. There is thus formed a coating of substantially uniform or homogeneous nature, composed of integrated and interbonded metallic grains, which can be easily machined and ground. The coating is susceptible of taking a very smooth and even glossy finish by polishing. A ground and polished surface of a coating of ferrous metal so formed has something of the aspect of polished granite.

The coating 3 may be of ferrous or other desired metal or alloy or metallic material com posed mainly of metal but containing carbon, silicon or other elements. For example the coating may be of metal of a cast iron or hard steel composition or of alloy steel.

lhe coating may be of say about the thickness of heavy paper or thin cardboard or of greater thickness if desired. Usually a coating of not more than about one sixty-fourth of an inch thick is preferable to one of greater thickness, it being desirable to conserve the use of coating metal as Well as to avoid undue increase of weight of the wood sheave.

The coating provides not only smooth hard tractive surfaces for the belt groove walls but also a protective armor for the perimeter of the wood sheave body, preventing scuffing or chipping thereof or breakage of the narrow wood ribs formed between the belt grooves, and reinforces and strengthens the wood sheave body.

Thus the invention substantially increases the practicability and efi'iciency of a wood sheave; obtains the advantage of a relatively light construction of non-metallic material with the durability and wearing qualities of a cast iron or hard metal sheave; renders it unnecessary to fabricate wood sheaves with the grain of the wood presented transversely of'the tractive surfaces for substantially or nearly the entire circumference; and provides a construction which permits the use of soft wood, paper board or other relatively soft, light, cheap materials for the sheave body.

It is contemplated that the bodies of sheaves embodying the invention may be made variously from non-metallic materials of the class comprising wood, paper and the like, including plywood, paper board, papienmach, fibre board and analogous materials, and also such moldable plastics .as may be suitable for sheave bodies and susceptible of coating of their perimeters by the method described without injurious effect upon the peripheral contours of the molded bodies.

The invention is thus conducive to promoting the utilization of wood and other non-metallic materials for sheave construction. In this connection an important advantage of the invention is that manufacture thereof is not limited to particular forms and sizes by the use of dies, molds and the like; the wood or non-metallic bodies being readily producible in desired forms and sizes, to meet dii ferent requirements as to pitch diameters and members of belt grooves, and the 4 metallic coatings being easily applicable to any forms and sizes thereof.

Another advantage of the invention is that the metallic coating 3 may be electrically connected with the sheave shaft, for conducting ofi static electricity accumulating on the rubber driving belts running'in tractive engagement with the sheave, thereby affording protection from sparking by static electrical discharges, which is of great importance for installations where electric sparks would be liable to cause explosions; thus further increasing the practicability of wood sheaves or enlarging the field in which they can be utilized. Electrical connection of the coatin 3 with the sheave shaft may be made simply and inexpensively by a strip of metallic coating material 4 formed on the face of the wood sheave body and leading from the coating 3 to the shaft. In the case of the illustrative sheave, which is of the split contractible hub type and has fitted in its hub bore a split contractible wood bushing 5. the conducting strip i is continued across the end of the bushing as indicated at 6 in Fig. 3, or, more accurately speaking, the conducting strip 4 contacts with conducting material formed on the bushing at 6 and contacting with the shaft.

With respect to its body construction and mode of mounting, the illustrative sheave is in accord ance with and embodies the invention disclosed in the pending patent application of Firth and Lower, Serial No. 458,829, filed August 6, 1942, now Patent No. 2,352,474, dated June 27, 1944. The sheave body, comprising hub and rim portions and a connecting Web portion, is built up of adhesively joined wood plies or laminations arranged transversely of the sheave axis. The web laminations and corresponding laminations of the hub and rim portions of the sheave body are provided by the intermediate discs 1' and outer discs 8. Additional laminations of the rim portion of the sheave body, forming overhanging extension thereof, are provided by the rim rings 9 and facing rings Eli. Additional hub laminations are provided by the complemental halves ll of hub discs divided by the radial slots 12.

The several discs, rings and half discs referred to may be one piece elements or some or all of them may be composed of suitable jointed smaller wood pieces.

Cut through the laminated wood sheave body, at opposite sides of and spaced from the sheave bore, are a pair of large openings 13 the inner flat walls Hi of which are parallel-and perpendicular to the diametric plane A--B bisecting said openings. The portion of the sheave body between the openings is divided longitudinally of the axis by the slots [2 extending radially from the hub bore .to diametrically opposite points beyond the circumference of the hub. The slots 52, as Well as the openings I3, extend clear through the sheave body as shown in Fig. 1. There is thus provided a contractible split hub unitary with the surrounding rim portion of the sheave body.

The parts of the hub at opposite sides of the slots 12 are connected by bolts consisting preferably of slender metal rods it having screw threaded end portions engaged by the nuts I6 accommodated in the openings 53, flat metal washers ill being interposed between the bolt nuts and flat walls l4- forming the opposite sides of the sheave hub. By tightening said nuts, the sheave hub can be contracted on the contractile bushing 5 to clamp the sheave to the bushing and the latter to the shaft, whereby to secure the sheave in fixed relation to and driving connection with the shaft.

The bushing 5, which may be of metal but is preferably of wood, is split longitudinally by a slot l8 extending the full length of the bushing. In its uncontracted state the bushing fits the hub bore of the sheave and the shaft to which it is applied, though in view of the contractibility of the bushing the shaft may be of slightly less diameter than the bore of the bushing. The sheave can be used with wood bushings of different inside diameters to adapt it to shafts of different diameters.

One practicable method of making a sheave body of the construction described (which can be made in several different ways) is as follows. First there is built up or fabricated in the rough a laminated wood body or pile of adhesively joined wood discs, either integral or composite, to provide the laminations for the hub and web and intermediate portion of the rim or all except the overhanging extensions of the rim portion of the sheave body. Having built up such laminated wood body in any appropriate manner, the next step is to bore a center hole therethrough to provide the hub bore. Next the openings I3 are cut through said body. Then said body is split by sawing through it on the diametric line C-D, using a thick saw through the part of the body which is to form the hub and web, so as to provide the radial slots l2, and using a thin saw through the surrounding or outer portion of the laminated body. Said body is thus divided into two identical half parts. Now the holes for the hub bolts are drilled in said half parts, and the 2 bolt rods I5 are inserted in said half parts which are then glued back together again; or, after inserting said bolt rods the said two half parts may be joined by suitably keying them together. After these operations there are added wood rings to provide the laminations for the rim extensions of the sheave body, such added wood rings being adhesively united to said body and to one another. The unfinished sheave body thus made in the rough is now put into a lathe and shaped to the form desired, as, for example, that shown in Fig. l.

It will be apparent that in the case of a sheave body of the construction described, the

metallic coating 3, forming a continuous binding around its perimeter, ties together the several laminations of the rim portion of the body and effectually reinforces and strengthens the structure.

The particular construction of sheave shown and described will be understood to be exemplary, the invention being applicable to non-metallic sheaves of various different forms and constructions and adapted to be mounted by various different means on the sheave shafts or on sleeves to be applied to the shafts.

In making a sheave embodying the invention, the wood sheave body is mounted in a suitable machine in which it is rotated about its axis, and the metallic coating material is sprayed on its perimeter while it is so rotated, whereby to obtain a coating of substantially uniform thickness.

I claim:

1. A sheave for power transmission comprising a peripherally grooved sheave body of wood or other suitable non-metallic material having a thin coating of metal covering and adhering di rectly to its perimeter and lining the groovetyalls thereof, said coating being composed of integrated separately formed grains and bonded to said walls in driving connection therewith by engagement of such grains in surface pores or inter,-

stices of said non-metallic material, and the por tions of said coating lining said groove walls;

having ground smooth belt-engaging surfaces.

2. A sheave for power transmission comprising a sheave body of wood or other suitable nonmetallic material having a plurality of annular belt grooves formed in its perimeter and a circumferentially continuous and seamless thin metallic sheathing conforming to the contour of and covering said perimeter and lining the walls of said grooves, said sheathing being a metallic coating fitting as a skin and adhering directly to said perimeter in driving connection therewith and the portions thereof lining the walls of said grooves having ground smooth belt-engaging surfaces.

3. A sheave for power transmission comprising a sheave body of wood or other suitable non-metallic material of laminated formation with its plies or laminations arranged transversely of the sheave axis and having a plurality of annular belt grooves formed in its perimeter, and a circumferentially continuous and seamless thin metallic sheathing conforming to the contour of and covering said perimeter and lining the walls of said grooves, said sheathing being a metallic coating fitting as a skin and adhering directly to and binding said perimeter in driving connection therewith and tying together the plies or laminations of the rim portion of the sheave, and the portions of said coating lining said groove walls having ground smooth belt-engaging surfaces.

4. A V-belt sheave for power transmission comprising a sheave body of wood or other suitable non-metallic material having one or more annular belt-grooves of V-shaped cross section formed in its perimeter and having circumferentially continuous thin metallic films lining the walls of said grooves and adhering directly thereto in driving connection therewith, said films having smooth belt-engaging surfaces.

5. A V-belt sheave for power transmission comprising a sheave body of wood or other suitable non-metallic material having a plurality of annular belt grooves of V-shaped cross-section formed in its perimeter and a circumferentially continuous and seamless thin metallic sheathing conforming to the contour of and covering said perimeter and lining the walls of said grooves, said sheathing being a metallic coating fitting as a skin and adhering directly to said perimeter in driving connection therewith, the coating being composed of integrated separately formed grains and bonded to said walls by engagement of such grains in surface pores or interstices of said nonmetallic material, and the portions of said coating lining said groove walls having ground smooth belt-engaging surfaces.

DAVID FIRTH.

Images