Patent Description:
The invention relates generally to power-driven conveyors and, more particularly, to components in a conveyor system formed by two or more materials bonded together. Many conveyor components, such as belt modules that link together to form a conveyor belt, position limiters, wear strips and sprockets are injection molded out of a thermoplastic polymer material to form a rigid body.

Problems abound when attempting to form a conveyor component from multiple materials having different characteristics. It may be difficult to have different materials bond together to form a cohesive, unitary component.

<CIT> discloses a method for manufacturing a decorative molded article.

<CIT> discloses a module for chains or belts that is molded from a plastic compound containing a magnetizable element.

<CIT> discloses a plastic conveyor belt system providing high frictional surface contact between the conveyor work surface and the load carried by the conveyor.

In one aspect, the present invention provides a method of manufacturing a conveyor component, in accordance with claim <NUM>.

The disclosed systems and methods can be understood with reference to the following drawings. The components in the drawings are not necessarily to scale.

A method of joining a thermoformable material to an injection moldable material to form a conveyor component is provided. The invention will be described below relative to certain illustrative embodiments, though the invention is not limited to the illustrative embodiments.

<FIG> shows an embodiment of a conveyor component <NUM> comprising multiple materials chemically bonded to each other. The illustrative conveyor component <NUM> is a position limiter including a base portion <NUM> formed of a first material and an upper layer <NUM> formed of a second material bonded to the first material. The illustrative upper layer forms a limiting surface for contacting a conveyor belt to ensure proper engagement between a tooth on the conveyor belt and a sprocket driving the conveyor belt. The illustrative base portion <NUM> is formed of an injection molded material. The upper layer <NUM> comprises a thermoformable material bonded to the injection molded material during a manufacturing process.

The first material comprises an injection moldable material. As used herein, "injection moldable material" refers to any suitable material or combination of materials that may be injection molded to form a selected shape. Injection moldable materials are able to transition to molten form when heated. Examples include, but are not limited to thermoplastic polymer materials, such as polypropylene, polyethylene, acetal, or composite polymers.

The base portion <NUM> includes a snap clamp <NUM> for mounting the conveyor component to a shaft of a conveyor frame, as described in <CIT> and entitled "Snap-On Position Limiter for a Conveyor Belt", the contents of which are herein incorporated by reference.

The second material comprises a themoformable material. As used herein, "thermoformable material" refers to any suitable material or combination of materials that is thermoformable, i.e., able to be formed by heat and-or compression. A thermoformable material does not transition to molten form when heated and retains a solid, though malleable form. Examples include, but are not limited to ultra-high-molecular-weight polyethylene (UHMW), ceramic-impregnated plastic, and others known in the art. An example of a ceramic-impregnated thermoformable material is Ceram P® available from Quadrant EPP AG Corporation of Lenzburg, Switzerland.

The upper layer <NUM> forms a limiting surface <NUM> for guiding a conveyor belt relative to a sprocket. In one embodiment, the limiting surface <NUM> of the upper layer has a low coefficient of friction to facilitate its limiting function.

The ability to use two separate materials with different properties enables different parts of the conveyor component to have optimal properties for that parts' particular function. For example, the base portion <NUM> is formed of a stronger material to withstand certain forces and the limiting surface <NUM> is formed of material with a low coefficient of friction to facilitate the limiting function.

<FIG> illustrates the steps involved in manufacturing a conveyor component, such as the conveyor component <NUM> of <FIG>, having a base portion <NUM> formed of an injection moldable material and an upper layer <NUM> comprising a thermoformable material bonded to the injection molded material.

<FIG> is a diagram of a portion of a molding machine used in the process of <FIG>. The molding machine <NUM> uses an injection mold including a first mold half, shown as a bottom mold <NUM>. The bottom mold <NUM> includes a mold cavity <NUM> forming a mold surface <NUM> that defines the upper surface <NUM> of the final conveyor component <NUM>. The machine <NUM> includes holders for holding a substrate <NUM> of a thermoformable material. The holders <NUM> comprise spring-loaded pins forming an initial seat for the substrate <NUM> and extending through the bottom mold. The pins <NUM> initially hold the substrate above the mold cavity <NUM>. The machine also includes a heating mechanism <NUM> for heating the thermoformable substrate.

In a first step <NUM>, a "draft" (first version or prototype) insert and-or substrate <NUM> of a thermoformable material is formed. The draft substrate may be stamped, cut or otherwise formed into a basic outline shape through any suitable means known in the art. The draft insert/substrate could be a simple flat piece sized to a desired size, or could be a more complicated substrate of any size or shape. In the illustrative embodiment, the draft substrate <NUM> is cut to about the size of the mold surface <NUM> in the mold cavity <NUM>. Preferably, the draft substrate has a -0to+<NUM>% tolerance to allow slight expansion to cover the mold surface <NUM>. If necessary, heat may be applied to form the draft substrate <NUM>. The draft substrate <NUM> has a first surface <NUM> that forms the limiting surface <NUM> of the finalized position limiter and an opposite second surface <NUM> that forms a bonding surface that bonds the upper layer <NUM> to the base portion <NUM>. The draft substrate <NUM> may have any suitable thickness.

In step <NUM>, the draft substrate is inserted in a holder <NUM>. The illustrative holder comprises spring-loaded pins inserted in the bottom mold <NUM> and extending from the top surface thereof. The pins form a seat for holding the draft substrate <NUM> above the mold cavity <NUM>.

In step <NUM>, a heating mechanism <NUM> pushes down on the draft substrate <NUM> to preheat and shape the substrate <NUM>. The illustrative heat and pressure mechanism <NUM> comprises a piece of hardened steel shaped to the final form of the layer <NUM>. The heating mechanism presses the draft substrate <NUM> into the mold cavity <NUM> while applying heat to the thermoformable material. The illustrative heating mechanism <NUM> provides about <NUM> watts of heat energy, though the invention is not so limited. The heat and pressure makes the substrate sufficiently malleable to conform to the shape of the mold surface <NUM>, resulting in a shaped substrate <NUM>', shown in <FIG>, having the shape of the final upper layer of the conveyor component <NUM>. If the draft substrate <NUM> is already in a desired form, little pressure is applied so that the shape does not substantially change. In another embodiment, infrared energy can be used to heat the draft substrate. Other suitable means for preparing the draft substrate for adhesion can be used.

In step <NUM>, the heating mechanism <NUM> continues to apply heat and pressure to the shaped substrate <NUM>' until the shaped substrate <NUM>' is ready for bonding with an injection molded portion in step <NUM>. Preferably, the heat and pressure are uniformly applied to the bonding surface <NUM> of the substrate. In one embodiment, the shaped substrate <NUM>' is in a bondable state when the bonding surface <NUM>' is tacky or adhesive while the opposite surface <NUM> remains smooth and undeformed, or as close to the original surface finish as possible. In the bondable state, the molecules on the bonding surface <NUM>' are open and ready to chemically bond with another material.

For example, for a UHMW material, the heating mechanism is applied until the shaped bonding surface <NUM>' reaches a temperature of between about <NUM>°C (<NUM>°F) and about <NUM>°C (<NUM>°F). The heating mechanism is removed before the opposite surface <NUM> reaches about <NUM>°C (<NUM>°F). A "ready" bonding surface for UHMW will become clear, indicative of a bondable state, while the opposite side remains opaque, as shown in <FIG>. The substrate <NUM>' is ready for bonding when the transition <NUM> between the bondable material <NUM>' and the smooth material <NUM>' is in the middle of the substrate <NUM>', as shown in <FIG>.

In an illustrative embodiment, the temperature of the heating mechanism <NUM> is set to <NUM>°C (<NUM>°F) to provide a heating mechanism surface temperature of between about <NUM>°C (<NUM>°F) and about <NUM>°C (<NUM>°F). While the illustrative heating mechanism <NUM> is a direct contact metal material form with heater cartridges installed thereon, the invention is not so limited. The heating mechanism <NUM> may alternatively heat the thermoformable material through an indirect stream of hot air directed at the thermoformable material or through other means known in the art.

The actual temperature, pressure and time involved in getting the thermoformable material into a bondable state vary depending on the thermoformable material.

During application of heat and pressure, the draft substrate <NUM> may expand in one or more directions, trapping itself within the mold cavity <NUM>.

In one embodiment, the manufacturing process employs a heat transmitting layer <NUM> between the substrate <NUM> and the heating mechanism <NUM>. The heat transmitting layer <NUM> transfers heat from the heating mechanism but prevents the eventually tacky material in the substrate <NUM> from sticking to the heating mechanism <NUM>. Any suitable material may be used to form the heat transmitting layer. Preferably, the heat transmitting layer comprises a non-stick surface coating, such as polytetrafluoroethylene and others known in the art.

After the substrate <NUM>' is ready for bonding, the heating mechanism <NUM> is retracted from the ready substrate <NUM>' in step <NUM>. If a heat transmitting layer <NUM> is used, it is also removed.

An upper mold half (not shown) immediately mates with the bottom mold <NUM> to close the mold in step <NUM>.

Then, in step <NUM>, injection molding of the base portion <NUM> commences. Preferably, the mold is preferably closed and injection molding to commences while the substrate <NUM>' is still in the bondable state. Step <NUM> involves injecting molten injection moldable material into the closed mold in which the ready substrate <NUM>' is contained. Preferably, the gates on the mold for the molten material are located to push the substrate <NUM>' against the surface <NUM>. Thus, the injection pressure is directed towards the adhesive surface <NUM>' and holds the substrate in place within the mold.

The molten injection moldable material contacts the bondable layer <NUM>' of the substrate and the two materials bond and lock onto each other.

The thermoformed substrate <NUM>' is preferably kept to a high enough temperature to continue the bonding process during the cooling of the injection molded portion <NUM> of the conveyor component. This is done with a variance of tools (for the injection molded portion <NUM>) and/or warming channels in the tool (to keep the non-injection molded substrate <NUM>' to a bondable temperature.

In one embodiment sonic waves may be transmitted into the mold to enhance the bonding between the substrate <NUM>' and the injection molded material. The sonic waves excited the modules to promote bonding. Electronic beams and - or radiation may also be used.

The above-described manufacturing technique may be used for any type of conveyor component that is traditionally injection-molded. Examples include, but are not limited to, sprockets, wear strips, conveyor belt modules, position limiters and other components known in the art.

<FIG> show another embodiment of a conveyor component <NUM> comprising a thermoformable material bonded to an injection moldable material. The conveyor component <NUM> is a conveyor belt module including an injection molded base <NUM> and a thermoformed upper layer <NUM>. The thermoformed upper layer <NUM> is heated and shaped until a bonding surface of the upper layer is in a ready, bonding state in a mold. Then, the material for the base <NUM> is injected into the mold while the bonding surface is still in the ready, bonding state to form the base portion <NUM>, such that the base portion <NUM> is bonded to the upper layer <NUM>.

<FIG> shows a conveyor component <NUM> comprising an injection molded base <NUM> and a thermoformed upper layer <NUM> having extensions <NUM> bonded to the injection molded base <NUM>. The conveyor component <NUM> is formed by heating and shaping the upper layer <NUM> until a bonding surface of the upper layer is in a ready, bonding state in a mold. Then, the material for the base <NUM> is injected into the mold while the bonding surface is still in the ready, bonding state to form the base portion <NUM>, such that the base portion <NUM> is bonded to the upper layer <NUM>. The thermoformable portion may form the top of a module, or the bottom of the module.

In another embodiment, a drive bar for a conveyor belt may be thermoformed or compression molded, then a main body of the conveyor belt may be injection molded onto the drive bar. Alternatively, a main body may be thermoformed or compression molded, then a drive bar injection molded onto the main body.

Claim 1:
A method of manufacturing a conveyor component (<NUM>), comprising the steps of:
inserting a thermoformable substrate (<NUM>) into a mold cavity (<NUM>), the mold cavity (<NUM>) having a mold surface (<NUM>);
applying pressure and heat to the thermoformable substrate (<NUM>) to shape the thermoformable substrate on the mold surface (<NUM>);
removing the pressure and heat when a first surface (<NUM>') of the thermoformable substrate (<NUM>) is in a ready for bonding state and an opposing second surface (<NUM>') of the thermoformable substrate (<NUM>) is in a nonbondable state;
closing the mold cavity (<NUM>); and
injecting a molten injection moldable material into the mold cavity (<NUM>), such that the molten injection moldable material contacts and bonds to the first surface (<NUM>') of the thermoformable substrate (<NUM>) while the first surface (<NUM>') remains in a bondable state.