Method and apparatus for molding non-pneumatic wheels

A method and apparatus for molding non-pneumatic wheels is provided. The exemplary method and apparatus allow for the use of the same molding system to manufacture wheels with different hub constructions. Different configurations of removable mold elements are utilized within the same molding system to provide wheels with different hub constructions.

PRIORITY STATEMENT

The present application claims priority to PCT/US14/070784, filed Dec. 17, 2014 in the United States Receiving Office.

FIELD OF THE INVENTION

The subject matter of the present disclosure relates generally to a method and apparatus for molding non-pneumatic wheels.

BACKGROUND OF THE INVENTION

Non-pneumatic wheel constructions and their benefits are described in e.g., U.S. Pat. Nos. 6,769,465; 6,994,134; 7,013,939; and 7,201,194. Some non-pneumatic tire constructions propose incorporating a shear band, embodiments of which are described in e.g., U.S. Pat. Nos. 6,769,465 and 7,201,194, which are incorporated herein by reference. Such non-pneumatic tires provide advantages in tire performance without relying upon a gas inflation pressure for support of the loads applied to the tire.

In one example of a non-pneumatic wheel, a compliant band with a ground contacting portion can be connected with a plurality of web elements extending radially from a center element or hub. For certain constructions, such non-pneumatic wheel may be formed by open cast molding in which a material such as e.g., polyurethane is poured into a mold that forms all or part of the non-pneumatic tire. Reinforcements in various parts of the non-pneumatic wheel may be molded in place. For example, one or more inextensible reinforcements such as cords may be molded in place in the compliant band.

The molds used to cast such non-pneumatic wheel constructions are a substantial part of the overall expense of manufacturing. Multiple, intricate features must be used to mold e.g., the individual web elements that extend between the hub and compliant band. Typically, the molds are carefully machined from metal having a high thermal conductivity such as e.g., aluminum.

The hub is used to connect the non-pneumatic wheel with a vehicle. The hub may be connected directly to the vehicle or may be connected through another component such as a wheel center. A variety of different constructions or configurations may be used for the hub, which may be constructed in whole or in part from one or more metals. Because of the associated expense of creating the molds, a requirement of different molds for different hub configurations is undesirable.

Accordingly, a method and apparatus for molding non-pneumatic wheels would be useful. More particularly, a method and apparatus that allows use of the same mold for manufacturing non-pneumatic wheels with different hub configurations would be particularly beneficial.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for molding a non-pneumatic wheel. The exemplary method and apparatus allow for the use of the same molding system to manufacture wheels with different hub constructions. More particularly, multiple configurations of removable mold elements are utilized within the same molding system to provide wheels with different hub constructions. The present invention can provide a savings in manufacturing cost by avoiding the requirement of a different mold for each hub configuration. Additional objects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the invention.

In one exemplary embodiment, the present invention provides an adjustable molding system for a non-pneumatic wheel, the non-pneumatic wheel including a plurality of tension-transmitting web elements extending between a load support band and a hub, the non-pneumatic wheel defining axial, radial, and circumferential directions. The molding system includes an upper mold portion having a plurality of upper web forming elements spaced apart around the circumferential direction. A lower mold portion has a plurality of lower web forming elements spaced apart around the circumferential direction and are configured to receive the upper web forming elements when the molding system is in a closed position to form the tension transmitting web elements during the molding process. The upper mold portion and lower mold portion form an internal cavity when the molding system is in the closed position.

This exemplary molding system also includes a first configuration of removable mold elements for positioning within the internal cavity. The first configuration includes an upper mold bowl configured to form a surface of the wheel and a lower mold bowl supporting the upper mold bowl and configured to form a surface of the wheel. The lower mold bowl is supported on the bushing when the first configuration is positioned within the internal cavity. A removable bushing is positionable onto the lower mold portion. The molding system also includes a second configuration of removable mold elements for positioning within the internal cavity. The second configuration includes a spacer ring and a removable bushing positioned onto the lower mold portion. The spacer ring is received onto the bushing when the second configuration is positioned within the internal cavity. The first and second configurations are interchangeable within the molding system.

In another exemplary aspect, the present invention provides a method of molding a non-pneumatic wheel using a molding system that includes an upper mold portion and a lower mold portion that can be selectively joined to form an internal cavity. The exemplary steps include positioning a removable bushing and a lower mold bowl onto the lower mold portion; placing a compliant, load supporting band onto the lower mold portion; inserting an upper mold bowl onto the lower mold bowl; closing an upper mold portion onto the lower mold portion; and heating the lower mold bowl, upper mold bowl, and load supporting band to a predetermined temperature. A molding material may be poured into the molding system to form the non-pneumatic wheel.

DETAILED DESCRIPTION

As used herein, the following definitions apply:

“Meridian plane” is a plane within which lies the axis of rotation of the tire or wheel.FIGS. 2 and 3, for example, are cross-sections of an exemplary non-pneumatic wheel of the present invention taken along a meridian plane.

The “radial direction” or “R” is perpendicular to the axis of rotation of the tire or wheel.

The “axial direction” or “A” is parallel to the axis of rotation of the tire or wheel and perpendicular to the radial direction.

The “circumferential direction” follows the circumference of the tire or wheel and is denoted with “C”.

FIG. 1provides a perspective view of an exemplary non-pneumatic wheel50that can be manufactured using the present invention whileFIG. 2provides a cross-sectional view of wheel50taken along a meridian plane. The present invention is not limited to the particular shape, size, or appearance of the wheels shown in the figures. As will be understood using the teachings disclosed herein, wheels of other shapes, sizes, and appearances may be used as well.

Non-pneumatic wheel50includes a central mounting disk202this is provided with a series of apertures54through which threaded lugs or other fasteners may be inserted in order to mount wheel50onto a vehicle. Other mounting configurations may be used as well. Non-pneumatic wheel50also includes a compliant, load supporting band56positioned radially outward of a hub52and positioned concentrically with hub52. A tread48may be formed on, or provided as part of, load supporting band56. For example, a tread band may be adhered to load supporting band56.

A plurality of tension-transmitting web elements62extend along the radial direction R between hub52and load supporting band56. Web elements62are adjacent to one another and spaced apart about circumferential direction C of wheel50. Web elements62may have other shapes and configurations from what is shown inFIG. 1. Load supporting band56supports loads transmitted to non-pneumatic wheel50when mounted to a vehicle using mounting disk202. The load is transmitted by tension through web elements62to compliant band56.

By way of example, load supporting band56may include a shear band having an inner reinforcing band, outer reinforcing band, and a shear layer positioned therebetween. The shear layer may be constructed e.g., of an elastomeric material such as e.g., natural and synthetic rubbers, polyurethanes, foamed rubbers and polyurethanes, segmented copolyesters, and block co-polymers of nylon. The reinforcing bands may include reinforcements constructed from e.g., essentially inextensible cord reinforcements embedded in an elastomeric coating. Such reinforcements may include e.g., any of several materials suitable for use as tire belt reinforcements in conventional tires such as monofilaments or cords of steel, aramid or other high modulus textiles. Other constructions and materials may be used as well.

For the exemplary embodiment ofFIGS. 1 and 2, hub52is connected with a central mounting disk202embedded within an outer toroidal portion58of hub52using an exemplary molding system as described herein. By way of example, central mounting disk202may be constructed from a metal whereas hub52may be constructed from a polymeric material into which disk202can be molded. The polymeric material in the present embodiment, also referred to herein as the molding material, may be any suitable polymeric material such as e.g., a natural or synthetic rubber, polyurethane, foamed rubber and foamed polyurethane, segmented copolyesters, and block co-polymers of nylon.

Mounting disk202may be provided with one or more features to assist in securing disk202to outer toroidal portion58of hub52. For example, disk202may include a lip or bend226extending circumferentially about disk202. Mounting disk202may also include openings228(FIG. 4) through which material may extend during the molding process. Other features may be used as well.

FIG. 3provides a cross-sectional view of another exemplary embodiment of wheel50taken along a meridian plane where the same reference numerals denote the same or similar features as used in the embodiment ofFIGS. 1 and 2. For this exemplary embodiment, wheel50also includes a central mounting disk302. However, mounting disk302is not embedded within hub304. Instead, mounting disk302is attached to hub50along a flange314. By way of example, central mounting disk302and hub304may be constructed of one or more metals and welded or cast together.

FIG. 4provides a perspective view of an exemplary embodiment of an adjustable molding system100for a non-pneumatic wheel whileFIG. 5provides a side view of the same system100. Molding system100has a first configuration FC of removable mold elements that may be used to mold the exemplary wheel50ofFIGS. 1 and 2. Molding system100also has a second configuration SC of removable mold elements that may be used to mold the exemplary wheel50ofFIG. 3. In addition, first configuration FC and second configuration SC are interchangeable with each other within molding system100as will be further described in order to manufacture wheels with different hub configurations. InFIGS. 4 and 5, first configuration FC and second configuration SC are each shown in an exploded, non-sectional view to show their sequencing relative to each other within molding system100. Only one configuration, FC or SC, is used at time during the molding of a non-pneumatic wheel.

Molding system100includes an upper mold portion102and a lower mold portion106. InFIGS. 1 and 2, the upper mold portion102and part of the lower mold portion106are shown in sectional views to more clearly reveal certain interior components. Along with the FC and SC configurations of interchangeable mold elements, upper and lower mold portions102and106can be used to make the exemplary embodimentFIGS. 1 and 2as well as the exemplary embodiment ofFIG. 3, which allows for a substantial savings in production costs by e.g., the avoidance individual molds for each embodiment of the non-pneumatic wheels.

Upper mold portion102includes a plurality of upper web forming elements104spaced apart along circumferential direction C. Lower mold portion106includes a plurality of lower web forming elements108also spaced apart along circumferential direction C. When molding system100is in a closed position as depicted in the cross-sectional views ofFIGS. 6 and 7, web forming elements104and106can be used to mold tension transmitting elements62of either of the previously described exemplary embodiments of non-pneumatic wheel50. More particularly, in the closed position, the lower web forming elements108interlock with the upper web forming elements104to provide spaces therebetween for the formation of the web-like, tension transmitting elements62during the molding process in which a molding material such as e.g., polyurethane is poured into molding system100. In other embodiments of system100, web forming element104and108may meet to each form only a portion (e.g., half) of the web elements62. Other constructions may be used as well.

Referring toFIGS. 4, 5, and 6, the first configuration FC, used for the exemplary embodiment ofFIGS. 1 and 2, includes an upper mold bowl200having an upper mold bowl forming surface214. During molding operations, surface214forms part of the inner surface64of outer toroidal portion58. A lower mold bowl204supports the upper mold bowl200. Lower mold bowl204provides a lower mold bold forming surface216that also forms part of the inner surface60of outer toroidal portion58during molding operations.

Central mounting disk202is held in place between upper mold bowl200and lower mold bowl204when molding system100is in a closed position shown inFIG. 6. It should be understood that central mounting disk202is part of non-pneumatic wheel50and is not part of first configuration FC of removable mold elements. Central mounting disk202is positioned to be embedded within hub52when molding material is poured into molding system100and fills the internal chamber or cavity112formed by mold portions102and106when molding system100is in the closed position.

First configuration FC also includes a bushing206configured for receipt of lower mold bowl204and upper mold bowl200. More particularly, when molding system100is in a closed position with first configuration FC positioned in internal cavity112as shown inFIG. 6, bushing206projects along vertical direction V into an opening220in lower mold bowl204, through opening218in central mounting disk202, and into an opening222in upper mold bowl200.

A central opening232of bushing206is used to position bushing206onto a pilot124extending from lower mold portion106. Bushing206has a top end208and a bottom end212. An annular rib210is formed on bottom end212and extends along circumferential direction C. Rib210supports lower mold bowl205on pilot124. As shown inFIG. 6, rib210is received into a recess224formed in the interior230of lower mold bowl205. During molding operations as described below, bushing206can be used to lift lower mold bowl204, mounting disk202, and upper mold bowl200simultaneously to remove from, or place the same into, molding system100. For example, a robotic arm can be used to grasp bushing206by top end208and position as needed.

Additionally, when in the closed position as shown inFIG. 6, load support band56is positioned between upper mold portion102and lower mold portion106. Further, in the closed position, upper mold bowl200and lower mold bowl204are positioned concentrically within load support band56. Similarly, upper web forming elements204and lower web forming elements108are positioned within load support band56when molding system100is in the closed position. As such, during molding operations, load support band56forms part of the mold when molding material is poured into the internal cavity112formed by the closing of molding apparatus100. This allows the molding material to join with load support band56to form non-pneumatic wheel50.

An exemplary method of using molding system100to manufacture exemplary non-pneumatic wheel depicted inFIGS. 1 and 2will now be described. Using the teachings disclosed herein, it will be understood that other methods with different steps or a different sequence of steps may be used in still other exemplary methods of the present invention.

In one exemplary method, the molding surfaces of molding system100are cleaned. After a preheating step, the molding surfaces are treated with a coating to help release molding material after molding and curing. Bushing206can be used to lift lower mold bowl204, mounting disk202, and upper mold bowl200simultaneously and place onto the lower mold portion106of molding system100. Load support band56is placed within a complementary groove118defined by lower mold portion106. The upper mold portion102is then placed onto lower mold portion106with support band56received into complementary groove122.

The molding system100is heated again until e.g., a predetermined temperature is reached. Next, a molding material such as e.g., polyurethane or another material as previously described is poured into molding system100. More specifically, the molding material is poured through e.g., opening120and allowed to fill internal cavity112formed by the closed position of molding system100. The mold material fills the interstitial spaces formed by the upper and lower mold portions102and106to form wheel50. During the pouring step, after the pouring step, or at the same time as the pouring step, molding assembly100is rotated to e.g., help distribute the molding material within molding system100and remove bubbles that may be entrained in the molding material.

Molding system100is then placed into an oven for additional heating so as to cure the molding material. Once the molding material is cured, molding system100can be removed from the oven. Upper mold portion102can then be removed and non-pneumatic wheel50can be de-molded. Bushing206can be used to remove the cast wheel50along with the removable mold elements from lower mold portion106.

Referring toFIGS. 4, 5, and 7, the second configuration SC can be used to mold the exemplary wheel ofFIG. 3and is interchangeable with first configuration FC. Second configuration SC includes a spacer ring306and bushing206. When mold system100is in the closed position shown inFIG. 7, mounting disk302rests upon spacer ring306. Spacer ring206defines an opening310through which bushing206projects along vertical direction V. Pilot124projects along vertical direction V through opening232in bushing206.

Mounting disk302is located within hub304. Hub304is supported upon lower mold portion106. When molding system100is in the closed position shown inFIG. 7, a spring loaded pour cap (not shown) pushes down onto the top edge300of canned hub304to seat the hub onto the lower mold portion106.

Additionally, when in the closed position shown inFIG. 7, load support band56is positioned between upper mold portion102and lower mold portion106. Specifically, load support band56is received into complementary grooves118and122. Further, in the closed position, cap300and hub304are positioned concentrically within load support band56. Similarly, upper web forming elements204and lower web forming elements108are positioned within load support band56when molding system100is in the closed position. As such, during molding operations, the outer surface308of hub304and the inner surface of load support band304forms part of the mold when molding material is poured into the internal cavity112formed by the closing of molding apparatus100. This allows the molding material to join with the external surface308of hub304and load support band56to form non-pneumatic wheel50. Hub304and mounting disk302form part of wheel50and are not part of the second configuration SC of removable mold elements.

As will be understood using the teachings disclosed herein, methods similar to that previously described for first configuration FC may be used to mold the exemplary wheel50ofFIG. 3using the second configuration SC. As previously stated, configurations FC and SC are interchangeable. Either configuration may be removed from molding system100to allow for installation of the other configuration depending upon the wheel hub configuration that will be manufactured.

Multiple bushings206may be used with the present invention. For example, different configurations of wheels50may use bushings206of different sizes and shapes. In addition, to facilitate manufacture, multiple bushings206may be used. For example, during manufacture, several bushings206may be used at the same time so that as mold system100is unloaded with a molded wheel50, another assembly of e.g., bushing206, bowls200and204, along with disk202may be loaded into mold assembly100in preparation for molding another wheel50. Other methods may be used as well.