Abstract:
A belt for conveying elements in provided wherein the belt comprises a compressible layer attached to the top surface of the belt. Preferably the compressible layer is resiliently deformable to cushion the impact of items on the belt. The belt preferably is a link belt and the top surface of the belt comprises a bonding layer for adhering the compressible element to the belt. The bonding layer may be a thermoplastic urethane that is heat fusible with the compressible layer to adhere the compressible layer to the belt.

Description:
RELATED APPLICATIONS 
     The present application hereby claims priority to U.S. Provisional Patent Application No. 60/443,891, filed Jan. 31, 2003, and which is hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to interlocking-link conveyor belts and has particular use in applications in which the conveyor is used to convey a workpiece and an increased gripping force between the conveyor and the workpiece is desired to reduce slippage between the conveyor and the workpiece. The present invention also relates to providing a belt having an upper surface that has a resiliently deformable surface. 
     BACKGROUND OF THE INVENTION AND DISCUSSION OF PRIOR ART 
     Link belts are generally known and used in a variety of applications, such as transmission belts and conveyor belts. When used as a conveyor, there may be slippage between the conveyor and the workpiece being conveyed. In some applications, it is desirable to reduce the slippage between the conveyor and the workpiece. 
     In addition, when used as a conveyor, frequently the material being conveyed is dropped onto the belt or manipulated so that the shock of the impact of the material onto the belt causes significant noise and/or vibration. The vibration can lead to accelerated wear of various components of the conveyor assembly. In addition, the significant noise produced by the impacting material degrades the work place environment and introduces dangers associated with high-noise environments. 
     SUMMARY OF THE PREFERRED EMBODIMENTS 
     A conveyor assembly comprising a continuous belt and a compressible gripping layer is provided. The belt is designed with sufficient tensile strength to convey the weight of the material being transported. This allows the material comprising the gripping layer to be selected without significant regard to the tensile strength of the material. A compressible layer is connected to the belt to form a gripping layer that also operates as a shock absorbing layer operable to resiliently deform to absorb the impact of material when material is placed on the top side of the conveyor assembly. 
     In a preferred embodiment, the compressible layer is a continuous hollow layer that is bonded to the top surface of the belt. In another embodiment, the compressible layer is formed of a plurality of separate compressible elements attached to the belt. Further, preferably the belt is formed of a plurality of interlocking links, and the separate compressible elements allow a belt link to be replaced without affecting the compressible elements on adjacent links. 
     A method for producing a belt is also provided. According to the method, a compressible layer is attached to the top surface of a belt. More specifically, preferably, the method includes the step of providing a belt having a top surface and adhering a compressible layer to the top surface. This may be accomplished by applying a bonding material to the top layer of the belt and then adhering the compressible layer via the bonding material. 
     In a preferred method, the bonding material is a layer of thermoplastic polyurethane on the top surface of the belt, and the compressible layer is also a thermoplastic material. The compressible layer is attached to the belt by heat fusing the compressible layer with the polyurethane bonding layer. Further, in a preferred method, the belt is comprised of a plurality of interlocking belt links and the method comprises the step of applying the bonding material to the top surface of sheet material and then cutting the belt links out of the sheet material. In yet another method, the compressible layer is cut after it is adhered to the belt. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of an interlocking-link conveyor assembly having a non-slip surface shown transporting a workpiece and engaged by a driving mechanism for the assembly. 
         FIG. 2  is a cross-sectional view of the conveyor assembly illustrated in  FIG. 1 . 
         FIG. 3  is a fragmentary side view partially in section, of the belt shown in  FIG. 1 . 
         FIG. 4  is a plan view of the belt shown in  FIG. 3 . 
         FIG. 5  is a top view of an individual link of the belt shown in  FIG. 1  prior to assembly. 
         FIG. 6  is a side view of the individual belt link shown in  FIG. 5 . 
         FIG. 7  is a perspective view of the belt illustrated in  FIG. 1  showing the belt in use in a power transmission application. 
         FIG. 8  is a cross-sectional view of an alternative embodiment of a conveyor assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings in general and  FIG. 1  specifically, the preferred embodiment of a conveyor assembly comprising a belt  15  having a non-slip gripping layer  40  is designated generally  10 . The assembly  10  is shown transporting a workpiece  14 . When the workpiece is placed on the conveyor assembly  10 , the gripping layer engages the workpiece. The gripping layer  40  preferably is deformable and has a high coefficient of friction to prevent slippage between the workpiece and the conveyor assembly  10 . 
     In a preferred embodiment, the belt  10  is a link belt having a top surface that forms a bonding surface  35 . Preferably, after the link belt  15  is formed, the gripping layer  40  is then bonded to the bonding surface  35  of the link belt. 
     The gripping layer  40  is preferably an elastically deformable layer that over lies the length of the belt. In this way, when a workpiece is placed on the belt, it is placed onto the gripping layer  40 . Alternatively, when used in a power transmission application, the gripping layer  40  is used as a drive surface to engage and drive cooperating elements. For example, in one application, the belt can be used to drive the rollers in a skate roller bed, as discussed further below. The gripping layer  40  frictionally engages the rollers to drive the rollers. 
     Referring now to  FIGS. 3 and 4 , the belt  15  preferably comprises a series of interlocking belt links  20 . One of the individual links  20  that comprise belt  15  is illustrated in  FIGS. 5 and 6 . Each belt link  20  has a body portion  22  and a fastener  30  connected to the body portion. In the present instance, the thickness of the belt link  20  between the top surface  38  and the bottom surface  39  is substantially uniform throughout the entire link. 
     A bonding material is permanently bonded to the top surface of each belt link  20 . The bonding material forms a bonding surface  35  that is coextensive with the top surface of the belt link  20 . Preferably, the bonding surface  35  is approximately 1 mm or less. 
     When the belt links are assembled to form a belt  15 , the bonding surface  35  can be used to bond the gripping layer  40  to the belt. Preferably, the bonding surface  35  is formed of a thermoplastic urethane and has a coefficient of friction that is greater than 1. In addition, preferably the bonding surface  35  has a coefficient of friction that is higher than the coefficient of friction of the bottom surface  39  of the belt link  20 . 
     The body portion  22  of the belt link  20  is generally rectangular, having two edges  25  extending longitudinally between a leading end  23  and a trailing end  24 , both of which extend transversely between the two edges. Adjacent leading end  23  a leading aperture  28  extends through the thickness of body portion  22 . Longitudinally spaced from the leading aperture  28  adjacent the trailing end  24 , a trailing aperture  29  extends through the thickness of body portion  22 . 
     The leading end  23  corresponds to the direction in which the assembly  10  travels as shown by the arrow in  FIG. 1 . However, the direction in which the assembly  10  travels can be reversed so that the leading end  23  does not lead the trailing end  24  with respect to the actual travel of the assembly. 
     The fastener  30  integrally connects the body portion  22 , and comprises a fastening tab  32  and a constricted neck  33 . The neck extends longitudinally, with one end connected to the fastening tab  32 , and the other end connected to the leading end  23  of body  22 . The length of the neck  33  between the leading end  23  and the fastening tab  32  is sufficiently long to allow the fastening tab  32  to extend through the apertures in two belt links  20  as will be further discussed below. 
     The fastening tab  32  is generally trapezoidal shaped, having two parallel ends that are transverse the neck  33 . The fastening tab  32  is substantially wider than the neck  33 , being widest at the point where it intersects the neck, and tapering as it extends away from the neck. 
     The belt links  20  are connected by passing the link fasteners through the apertures in adjacent belt links. To ensure that the belt links can properly connect, the apertures are configured and dimensioned with reference to the fastening tab and the neck. 
     In the present instance, the apertures through body  22  are non-circular. Both apertures  28  and  29  are longitudinally elongated so that their length  26  is greater than their width. To ensure that fastening tab  32  can pass through the apertures, the length of the apertures  26  is greater than the greatest width of the fastening tab  32 . 
     The width of apertures  28  and  29  is not constant. Instead, the apertures widen as they extend toward trailing end  24 . To provide proper connection between the belt links  20 , the apertures are narrower than the fastening tab width so that the fastening tab  32  cannot pass back through the apertures once the belt links are connected. However, the apertures are wider than the neck  33  to allow the neck to extend through the apertures while the belt links are connected, as will be discussed below. 
     The belt links  20  are made of a material of sufficient tensile strength to convey the weight of the workpiece  14  or transmit the necessary power, if used in a power transmission application. In the preferred embodiment, the belt links  20  are made of a thermoset urethane that is reinforced with a polyester fabric. 
     Because the belt links have sufficient tensile strength to convey the weight of the workpiece  14 , the material used to make the gripping layer  40  can be chosen according to characteristics such as deformability, resilience and coefficient of friction, without significant regard to its tensile strength. A variety of resilient elastomeric materials can be used. In the preferred embodiments, the gripping layer  40  is made from a thermoplastic urethane. 
     The gripping layer  40  is preferably formed as a separate element that is attached to the surface of the belt. Referring to  FIGS. 2–3 , in the present instance the gripping layer  40  is an extruded hollow generally cylindrical element formed of a resilient thermoplastic urethane. Preferably the wall thickness of the gripping layer is relatively thin (i.e. less than ¼″) so that the gripping layer can readily collapse or compress when it engages another element. 
     As previously stated, the assembly  10  comprises an interlocking-link belt  15  having a gripping layer  40 , which is comprised of a plurality of belt links  20  that have been described above. The following discussion describes the interconnections between the belt links  20  that form the belt  15 . 
     As shown in  FIGS. 3 and 4 , a series of belt links  20  are arranged in a superimposed successive overlapping relation to form the belt  15  with a bonding surface  35 . The bottom surface  39  of each belt link overlaps the top surface  38  of an adjoining belt link, so that the thickness of the belt  15  is at least twice the thickness of an individual belt link  20 . 
       FIG. 3  illustrates a portion of the assembly  10 , showing how the bonding layers  35  of the belt links combine to form a bonding surface when the belt links are interconnected. Included in these views is the connection between a belt link  20 A, and the two preceding belt links,  20 B, and  20 C. In this connection, the fastening tab  32 A of belt link  20 A passes sideways through apertures in the two preceding belt links. It first passes through the leading aperture  28 B of the adjacent preceding belt link  20 B and then passes through the trailing aperture  29 C of the next preceding belt link  20 C. 
     The term preceding is used with respect to the direction the assembly travels, as shown in by the arrow in  FIG. 3 . Because the direction of travel can be reversed, the preceding belt links can be succeeding with respect to the actual travel of the assembly  10 . 
     After passing through the aperture in belt link  20 C, the belt link fastening tab  32 A is twisted to bear against the bottom surface  39 C of belt link  20 C. When connected in this way, the top surface of belt link  20 A is the top side  11  of belt  15 , and the bottom surface  39 C of belt link  20 C is the bottom side  12  of belt  15 . 
     Referring to  FIG. 2 , the belt  15  is produced as follows. The belt links  20  that make up the belt  15  include at least one layer of reinforcing material, such as woven polyester sheet. The reinforcing material is impregnated with a binding material to form a composite material. The binding material is liquified and deposited onto the reinforcing material while liquid. Preferably, the composite material includes a plurality of layers of reinforcing material and the binding material is a thermoset urethane. 
     A bonding material is deposited on the composite material, preferably while the binding material is wet. In other words, preferably the bonding material is deposited on the composite material before the composite material is cured or dried. The bonding material may be sprayed on, poured on or the composite material may be partially submerged in a bath of bonding material. The bonding material may be a chemical adhesive, such as an epoxy. However, preferably the bonding material is a film of thermoplastic urethane that is approximately coextensive with the upper surface of the composite material. Since the binding material of the composite material is wet when the film is placed on the composite material, the film adheres to the composite material. 
     After the bonding material is deposited on the composite material, the combination is cured. During the curing process the layer of bonding material permanently bonds to the composite material. 
     Ordinarily the cured material is at least several times wider that the width of the belt links  20 . The cured material is therefore cut into a plurality of elongated strips approximately as wide as the width of a belt link  20 . The belt links are then cut-out from the strips of cured material. In the present instance, the belt links are formed by punching, which also simultaneously punches the rearward and forward apertures in the belt links. 
     Formed in this way, the belt links  20  have an integral bonding surface approximately 1 mm thick forming the top surface  38  of the belt link. The bonding surface is coextensive with the substrate material forming the belt link  20  which in the present instance is polyester reinforced thermoset urethane. 
     The belt links  20  are assembled to form a continuous interlocking link belt  15 . The belt links  15  are connected to one another as detailed above and shown in  FIGS. 3 and 4 . Preferably, the assembled belt is then trimmed by cutting the edges of the belt to form beveled edges that engage the sheaves of the pulleys about which the conveyor assembly  10  travels. 
     The gripping layer  40  is preferably attached to the belt  15  after the belt is formed, but before the ends of the belt are connected to form a continuous loop. As described above, preferably the bonding surface  35  is formed of a thin layer of the thermoplastic urethane that is adhered to the top surface of the belt links. To attach the gripping layer  40 , the gripping layer is placed on top of the belt. Heat is then applied to the gripping layer and the bonding surface to fuse the gripping layer and bonding surface together. In other words, heat is applied so that the thin layer of urethane on the top surface of the belt melts together with the bottom wall of the gripping layer, which preferably is also formed of urethane. 
     Preferably the gripping layer  40  is a continuous layer that extends around the entire length of the belt  15 . Accordingly, the ends of the gripping layer  40  are spliced together, preferable by heating the ends of the belt to fuse the ends together. In this way, preferably the gripping layer forms a continuous outer surface having a substantially uniform surface along the entire length of the belt. 
     As discussed previously, the conveyor assembly  10  can be used in power transmission applications as well. Referring to  FIG. 3 , the conveyor assembly  10  is used to drive a rollerbed  50 . The gripping layer  40  operates as an elongated pad that frictionally engages rollers  52  in the rollerbed  50 . As the conveyor assembly  10  is driven forwardly, the frictional engagement between the gripping layer  40  and the rollers  52  cause the rollers to rotate. This in turn causes any workpieces on top of the rollerbed  50  to be displaced along the rollerbed. 
     The rollerbed comprises a pair of parallel siderails  54  that support a plurality of skate wheel rollers  52  journaled between the siderails in a parallel array forming a rollerbed having a conveying surface parallel to the longitudinal run of the conveyor assembly  10 . The conveyor bed is positioned above the longitudinal run of the gripping layer  40  such that the longitudinal motion of the gripping layer in one direction along the length of the bed in frictional engagement with the undersides of the parallel rollers, causes the plurality of rollers  52  to rotate as indicated by the arrow in  FIG. 7 . The rotating rollers  52  then advance articles resting on the upper sides of the rollers. 
     Although in the preferred embodiment, the belt is a link belt with links connected by tabs, the present invention is broad enough to include other types of belts. For instance, other types of link belts can be used, such as a rivited link belt in which the overlapping links are rivited to each other. In addition, belts that are not link belts can be used, such as endless belts (i.e. belts made of a single length of material with the ends spliced together to form the belt). When using an endless belt, the belt material can be formed and the gripping layer  40  can be attached to the belt material before the ends of the belt are spliced together. Such a method is potentially more efficient then attaching the gripping layer after the ends of the belt are spliced together. 
     In addition, although the cushioning layer has been described as an elongated hollow generally cylindrical element, the invention is not limited to the particular type of cushioning layer. For instance, the cushioning layer may be solid or have relatively thick walls (i.e. thicker than ¼″). Further, the gripping layer may be formed of a fiber reinforced, metal reinforced or foamed thermoplastic urethane. Additionally, although the bonding surface  35  and gripping layer  40  are preferably formed of a thermoplastic urethane, the elements can be formed from other materials. However, it is desirable that the materials be selected to ensure a consistent secure bond between the belt and the gripping layer. Preferably, the bond is provided by thermally bonding the belt  15  and the gripping layer  40  as described above, so that the materials should be selected to provide a consistent secure thermal bond. In other instances however, it may be desirable to use a chemical adhesive as a primary or secondary bond between the gripping layer and the belt. If a chemical adhesive is used as a primary bond, it is possible to eliminate the thermal bond between the two layers. If the chemical adhesive is used as a secondary bond, preferably the chemical adhesive provides additional support to the thermal bond. If a chemical adhesive is used as a primary or secondary bond, the bonding surface and gripping layer should be formed of materials that can be securely connected by the chemical adhesive. 
     The gripping layer  40  has been described as a continuous generally cylindrically-shaped element, however the gripping layer can be formed into numerous different configurations. For instance, the gripping layer may have a half around, square, trapezoidal, rectangular or triangular cross-section. In addition, rather than being a single continuous element, the gripping layer can be formed of multiple layers or a series of separate segments of the same or different materials. Further, the upper surface of the gripping layer need not be a uniform continuous surface as described previously. In certain applications, the upper surface may form one of various profiles, such as a cogged profile formed of a series of notches formed to the top surface of the gripping layer. If the gripping layer is an extrusion, the profile can be formed into the extrusion after the material is extruded, but while the material is still hot so that the formed profile sets in the gripping layer. 
     Further, although the belt assembly  10  has been described as including a gripping layer  40 , alternatively, one or more elements can be thermally bonded to the belt  15  in a manner similar to how the gripping layer is bonded to the belt. For instance one or more segments or components can be adhered to the surface of the belt to operate as pins, cogs, teeth or other elements rather than the continuous gripping layer, depending upon the application. 
     Referring now to  FIG. 8  an alternate embodiment is illustrated. The alternate embodiment is similar to the embodiment illustrated in  FIGS. 1–7  and described above, however, this alternate conveyor assembly  110  has a gripping element  140  that is configured differently from the gripping element  40  described previously. Accordingly, except where otherwise discussed below, elements in this second embodiment are preferably substantially similar to corresponding elements in the first embodiment and are designated with the same reference number with an additional  100 . For instance, the belt links  120  in the second embodiment are substantially similar to the belt links  20  described in the first embodiment. 
     The alternate conveyor assembly  110  comprises a belt  115  having an upper surface to which a gripping or cushioning element  140  is attached. The gripping layer may extend outwardly overhanging the side edges of the belt  115 . However, preferably the gripping layer is approximately as wide as the width of the belt or narrower. 
     The gripping element comprises an elongated channel having sidewalls  142  and a top surface  144  extending between the sidewalls. Preferably, the top surface is substantially flat across the width and along the length of the belt. In addition, preferably the top surface has a thickness that is greater than the thickness of the side wall. 
     Although the top surface  144  is illustrated as continuous between the sidewalls, the top surface may extend between the sidewalls without interconnecting the sidewalls. The bottom surface  146  of the gripping element may be continuous like the top surface, however, preferably a slot extends through the bottom surface along the length of the gripping element. The slot provides addition clearance for the top surface when the top surface is deformed downwardly. In other words, when the top surface of the belt  110  engages an item, the top surface  144  may deform downwardly into the hollow space within the gripping element  140  and into the recess formed by the slot in the bottom surface  146 . This provides an greater distance for compression relative to the height of the sidewall than a similar element not having a slot, thus allowing a reduced profile for the gripping element. In addition, although the slot is shown as a through slot, the slot may be formed as a groove on the interior face of the bottom surface  146 . 
     The gripping element  140  may be attached to the belt in any of the methods described above in connection with the first embodiment. However, preferably the gripping element  140  is adhered to the belt by heat fusing the gripping element with bonding layer  135  on the top of the belt. 
     As described in the first embodiment, the gripping element is preferably a unitary element that extends along substantially the entire length of the belt so that the gripping layer provides a continuous top surface around the belt. Rather than being a single piece, the gripping element may be two or more elements that are individually bonded to the surface of the belt, so that the structure is essentially the same as a single continuous piece. However, in certain instances, it may be desirable to form the gripping element into a plurality of segments that are bonded to the belt. Using a plurality of elements, the ends of the gripping elements may be connected to one another so that the gripping element pieces provide a substantially continuous outer surface. Alternatively, the gripping elements may be adhered to the belt so that there are gaps between adjacent gripping element, so that the outer surfaces of the gripping elements do not create a substantially continuous surface around the length of the belt. 
     The separate gripping elements may be separately formed and individually adhered to the belt. Alternatively, a continuous gripping element may be adhered to the belt as described above, and then the gripping element may be cut into a plurality of segments by cutting the gripping element transverse the length of the belt. The length of the gripping segments may vary. In some instances, the gripping segments may overlap a plurality of belt links. In other instances, to maximize the flexibility of the conveyor assembly, the gripping segments may be cut so that each belt link has a separate gripping segment, with each belt segments being shorter than the length of each belt link. 
     The terms and expressions which have been employed are used as terms of description and not of limitation. There is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof. It is recognized, however, that various modifications are possible within the scope of the invention as claimed.