Spiral conveyor

Abstract: A conveyor belt (20) has a textured edge (46) for use in a spiral conveyor which includes a plurality of protrusions (60) on the edge (46) of the belt engaging the capstan (12), providing enhanced friction between the belt and the capstan (12). The protrusions (60) may be placed on end links (77) or reenforcement links (82), and may be a part of rods (78) connecting links of the belt. The capstan (12) can be textured as well to provide an additional friction. As the result, the driving force is transmitted to the belt much more efficiently, and the practical use of the plastic conveyor belt (20) in the spiral conveyor systems is possible.

Description: BACKGROUND OF THE INVENTION The present invention relates to material handling equipment and, more particularly, to a conveyor system having a spiral portion. One type of conveyor is known having a conveyor belt in which a portion of the conveyor belt is formed into an ascending or descending spiral. The ends of the spiral are connected together through an out-run, a return-run and an in-run. The conveyor is at least partly driven by a capstan rotating within the spiral portion and contacting the inner edge of the conveyor belt as it traverses the spiral. Frictional forces are controlled by a sprocket drive on the out-run which controls longitudinal tension in the conveyor belt. In effect, the amount of drive is controlled by the amount of longitudinal tension applied to the out-run. This is similar to a nautical winch in which a plurality of turns in the bight of a rope are wound on a rotating reel. If the rope exiting the reel is left slack, the reel turns with insufficient friction with the rope to pull the incoming rope. If a moderate tension is applied to the exiting rope, a substantial force is applied to the incoming rope. Spiral conveyors are disclosed in U.S. Patent No. 3,348,659 (now expired) and 4,078,655. Spiral conveyors of the type described above, and disclosed in the referenced patents, are frequently used in food-preparation establishments to hold freshly baked goods in a cooling environment for a substantial time prior to a succeeding operation such as, for example, packaging. The food-preparation industry shares with other industries the desire for improved productivity. One approach to improved productivity includes increasing the throughput of spiral conveyors. Throughput is achieved by increasing the linear speed of the conveyor belt. As the linear speed of the conveyor belt increases, it becomes increasingly difficult to couple enough torque through the frictional contact between the outer surface of the capstan and the inner edge of the belt without applying destructive tension in the conveyor belt. The lack of friction between the belt and the capstan is especially low if the belt is made of plastic. Such low friction becomes even lower if there under wet and icy condition, which occurs very frequently in the food industry. Making belts from plastics has some distinct advantages, however. Some of these advantages are: the price of a plastic belt is usually lower than that of a metal belt; the weight of the plastic belt is significantly lower than the weight of the metal belt; it is substantially easier to maintain the plastic belt clean due to the lower adhesion of production debris and dirt to plastic. Plastic belts driven by sprocket wheels are described, for instance, in the U.S. Patent No.4 742 907. Plastic belts are also described in the U.S. Patent No.4 394 901. However, plastics have lower load bearing capacity than metals, and their use in the spiral systems is restricted. Therefore, one of the problems with the conveyor belts for spiral systems is a difficulty of the transmittal of a driving force from the capstan to the belt. The difficulty is especially severe in the case of plastic belts. OBJECTS AND SUMMARY OF THE INVENTION It is an object of the invention to provide a spiral conveyor which overcomes the drawbacks of the prior art. Generally speaking and in summary the invention has for object a spiral conveyor system using a predominantly plastic belt structure, for example of a type similar to that disclosed in US-A-4742 907 but the construction of which is modified in such a way that it is possible to drive it by a capstan including a plurality of circularly spaced capstan bars of the general type disclosed in US-A-3 348 659 but presenting a modified structure adapted to the plastic structure of the belt. More precisely the invention concerns A spiral conveyor system, comprising : a capstan rotatable about a vertical axis, the capstan including a plurality of circularly spaced capstan bars, the bars having outer surfaces forming the general peripheral cylindrical driving surface of the capstan, a belt having at its inner edge friction means in contact with the outer surfaces of the capstan bars for the frictional driving of the belt by the rotation of the capstan through the spiral belt run, characterized in that, the belt is of the type comprising a succession of plastic link units mounted and interconnected side by side and end on end with each other, the link units being of the type telescoping with each other at a belt side inner edge, end links on the inner edge of the belt are provided and interconnected to the plastic link units and bear said friction means at their end edge, the belt side surface and the peripheral driving surface of the capstan comprising cooperating friction means formed by protrusions provided on one surface coacting with grooves provided on the other surface. In this way it is provided an interface between a capstan of a spiral conveyor and an inner surface of a conveyor belt which increases the drive force applied to the conveyor belt. And simultaneously it is provided a conveyor belt with an improved friction properties. This is permitted notably by providing a spiral conveyor having a predominantly plastic belt with a textured edge co-acting with a textured capstan in which the capstan-conveyor belt presents interacting system with higher friction between the capstan and the belt. The capstan can be textured as well to provide additional friction. As the result, the driving force is transmitted to the belt much more efficiently, and the practical use of a plastic conveyor belt in a spiral conveyor system is enabled. In one embodiment the conveyor belt has a textured edge for use in a spiral conveyor which includes a plurality of protrusions on the edge of the belt engaging the capstan, providing enhanced friction between the belt and the capstan. The protrusions may be placed on end links or reenforcement links, and may be a part of rods connecting links of the belt. The capstan is textured as well to provide an additional friction. As the result, the driving force is transmitted to the belt much more efficiently, and the practical use of the plastic conveyor belt in the spiral conveyor systems is possible. The protrusions also make possible the use of belts with a longitudinal pitches higher than one and two inches. According to the feature of the invention, the above belt may have a longitudinal pitch greater than two inches. The end units and reinforcement links may be flat plates, or have other shape useful in the spiral conveyor systems. The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjuction with the accompanying drawings, in which like reference numerals designate the same elements. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram of a spiral conveyor in which the present invention may be employed. Fig. 2 is a view of the spiral conveyor of Fig. 1 to which reference will be made in describing the prior art and the present invention. Fig. 3 is a close-up cross section of one vertical bar of Fig. 2 and a conveyor belt according to the prior art. Fig. 4 is a side view of the vertical bar of Fig. 3. Fig. 5 is a close-up cross section of the vertical bar and a conveyor belt according to an embodiment of the invention. Fig. 6 is a side view of a vertical bar according to a further embodiment of the invention. Figs. 7A and 7B are top and side views, respectively, of a portion of an edge of a prior art plastic conveyor belt without reenforcement links. Figs. 8A and 8B are top and side views, respectively, of a portion of an edge of a prior art plastic conveyor belt with reenforcement links. Figs. 8'A and 8'B are top and side views, respectively, of a portion of an edge of a prior art plastic conveyor belt driven by the sprocket wheels. Figs. 9A and 9B are tops and side views, respectively, of an edge of a plastic conveyor belt according to one embodiment of the present invention. Figs. 10A and 10B are tops and side views, respectively, of an edge of a plastic conveyor belt according to one embodiment of the present invention. Figs. 11A and 11b are tops and side views, respectively, of an edge of a plastic conveyor belt according to one embodiment of the present invention. Figs. 12A and 12B are tops and side views, respectively, of an edge of a plastic conveyor belt according to one embodiment of the present invention. Figs. 13A and 13B are top and side views, respectively, of an edge of a plastic conveyor belt according to one embodiment of the present invention. Figs. 14A and 14B are top and side views, respectively, of an edge of a plastic conveyor belt according to one embodiment of the present invention. Figs. 15A and 15B are tops and side views, respectively, of an edge of a plastic conveyor belt according to one embodiment of the present invention. Figs. 16A and 16B are tops and side views, respectively, of an edge of a plastic conveyor belt according to one embodiment of the present invention. Fig. 17 is a view of a portion of a metal conveyor belt for sppiral conveyors of the prior art. Fig. 18 is a view of a portion of a plastic belt for spiral conveyors of a prior art. Fig. 19 is a view of a portion of a metal belt according to one embodiment of the present invention. Figs. 20A and 20B are top and side views, respectively, of an edge of of a plastic conveyor belt according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Fig. 1, there is shown, generally at 10, a spiral conveyor system to which the present invention may be applied. A capstan 12 is rotated about its vertical longitudinal axis 14 by any convenient means such as, for example, an electric motor 16 driving a chain 18. A conveyor belt 20 is formed into an in-run 22, a spiral portion 24, an out-run 26, a take-up section 28 and a return run 30. A plurality of pulleys 32 shape conveyor belt 20 into its various parts. Take-up section 28 includes a sprocket drive 34 for applying a predetermined longitudinal tension to out-run 26. A take-up loop 36 is formed by sprocket drive 34 and take-up pulleys 38 and 40. A take-up force 42, indicated by a downward-directed arrow, is applied to take-up pulley 38 to help form take-up loop 36. Take-up force 42 may be applied by any convenient means such as, for example, a pendant weight, not shown. Spiral conveyor system 10 is illustrated as an up spiral or helix. Some applications employ a down spiral. Other applications combine an up spiral with a down spiral with the out-run of one feeding the in-run of the other. Conveyor belt 20 is of a type which permits a limited amount of longitudinal telescoping to form spiral portion 24. Such types of conveyor belt are well known and are fully described in, for example, the above-referenced patents. Thus, further detailed description thereof is considered not required, except insofar as it is necessary to support the present detailed description. In operation, sprocket drive 34 applies a predetermined longitudinal tension to out-run 26. This at least partly controls the tightness with which the inner edge of spiral portion 24 contacts the surface of capstan 12, and thus controls the friction between these elements. It is customary to permit capstan 12 to rotate at a speed which produces a surface velocity exceeding the velocity of the inner edge of spiral portion 24 contacting capstan 12. This speed difference, called overdrive, is from a few percent to a few tens of percent. The amount of overdrive is conventionally adjusted by adjusting the amount of longitudinal tension applied by sprocket drive 34. In some applications, sprocket drive 34 is mechanically coupled to electric motor 16 for concerted action thereof. In other applications, sprocket drive 34 is driven by a separate apparatus, optionally under closed-loop control for maintaining a predetermined tension in out-run 26, or a predetermined speed of spiral conveyor system 10. In the prior art, capstan 12 may have a solid surface, or may be formed of a plurality of vertical bars (not shown in Fig. 1). For the remainder of the present disclosure, the invention is described in the environment wherein capstan 12 is of the type formed of vertical bars. One skilled in the art will recognize that the invention is not limited to this environment, but may be applied to a capstan 12 having a solid, or other surface. The problem to be solved is transferring sufficient driving force from capstan 12 to spiral portion 24, preferably while maintaining a satisfactory amount of overdrive. Referring now to Fig. 2, capstan 12 is essentially a cage constructed of a plurality of vertical bars 44 supported by conventional means to form an approximation of a cylindrical surface. It is friction at the interface between the outer surfaces of vertical bars 44 and an inner edge 46 of conveyor belt 20 which drives spiral portion 24. Referring now to Fig. 3, an enlarged cross section of vertical bar 44 is shown, together with an inner edge 46 of one type of conveyor belt 20 (a more detailed drawing of the edge of the prior art belt used in a spiral type conveyors is depicted on Figs. 7A, 7B, 8A and 8B). Vertical bar 44 includes a rectangular tube 48, upon which is clipped a U-shaped resin member 50. First and second lugs 52 and 54 grip an inner surface 56 of rectangular tube 48. An outer bearing surface 58 of U-shaped resin member 50 bears against inner edge 46. For purposes of description, conveyor belt 20 is assumed to be of a type wherein transverse bars (not shown) are terminated in an enlarged portion 60 usually consisting of the flat enforcement links. It is seen that, in actuality, it is the surfaces of enlarged portions 60 which contact outer bearing surface 58 for the frictional transmission of motive force from vertical bar 44 to spiral portion 24. Referring now to Fig. 4, a few basics of the operation of spiral conveyor system 10 are described. The concept of overdrive must be understood. As spiral portion 24 rotates about capstan 12, at each revolution, spiral portion 24 experiences a change in height equal to the distance between tiers of spiral portion 24. If the peripheral speed of capstan 12 were exactly matched to the speed of inner edge 46, then a point on inner edge 46 would remain in the same transverse location on a outer bearing surface 58 as it rises or descends with its advancement about capstan 12. Thus this point on inner edge 46 would trace a vertical line on outer bearing surface 58, as indicated by a line labelled overdrive = 0. This is generally considered to be undesirable since experience has shown that this tends to develop substantial resistance to vertical motion of conveyor belt 20. This arises, at least partly, from a tendency for points on inner edge 46 to catch on vertical bar 44. From a practical standpoint, it is possible to discern the amount of overdrive that exists in a particular spiral conveyor system 10. With use, enlarged portions 60 leave easily visible scratches in outer bearing surface 58. The angle that these scratches make with a vertical line is indicative of the amount of overdrive. If overdrive equals 100 percent, no motion of conveyor belt 20 is produced. This results in horizontal scratches, as shown in Fig. 4. This is, of course, undesirable since zero motion of conveyor belt 20 means that spiral conveyor system 10 is non-functional. Normal overdrive of a few percent is indicated by a diagonal line as shown in Fig. 4. The angle that the scratch marks make with the vertical or horizontal are indicative of the amount of overdrive. The relationship between these angles and the actual amount of overdrive depends on the dimensions of the system. However, from a qualitative standpoint, the steeper the angle from the horizontal, the less the overdrive. The overdrive experienced by a particular spiral conveyor system 10 can change with time due to changes in load, temperature, humidity and lubrication, among other things. Monitoring the angles of scratch marks on outer bearing surfaces 58 is a useful way of alerting a maintenance operator of changes in overdrive that may require correction. As noted in the foregoing, as linear speeds increase, it becomes increasingly difficult to couple sufficient driving force between capstan 12 and spiral portion 24. Referring now to Fig. 5, a vertical bar 62 includes a U-shaped resin member 64 with an outer bearing surface 66 having a plurality of shallow vertical grooves 68 therein. The resulting irregularity in the outer bearing surface 66, as it contacts enlarged portions 60 increases the driving torque. However, several features prevent locking of enlarged portions 60 into grooves 68, and thus a zero-overdrive situation, with resulting improper operation, is avoided. First, it will be noted that grooves 68 are shallow, and thus have relatively gentle slopes. Thus, if an enlarged portion 60 enters a groove 68, it is capable of sliding up and out therefrom with a slight increase in friction. The cumulative effect of all of the slight increases in friction provides the desired increase in the transfer of motive force from vertical bar 62 to spiral portion 24. Second, with one direction of rotation of capstan 12 (Fig. 1), angle of contact of enlarged portions 60 with outer bearing surface 66 tends to lift inner edge 46 of spiral portion 24 (Fig. 2). This tends to release any binding which may occur. With the opposite direction of rotation of capstan 12, the angle of contact tends to urge inner edge 46 downward. Some installations may take advantage of the downward urging to increase driving friction. The vertical grooves 68 in vertical bar 62 offer the advantage that they can be formed during the extrusion of U-shaped resin member 64, without extra cost beyond a possible one-time tooling cost for a modified extrusion die. It is believed that some benefit may be attained by slanting the grooves so that they form a right angle with angle of contact 70. Referring to Fig. 6, a U-shaped resin member 72 is shown in which angled grooves 74 are disposed at right angles to angle of contact 70. This arrangement tends to maximize the increase in driving friction. It does, however, carry the disadvantage that angled grooves 74 cannot be formed during longitudinal extrusion of U-shaped resin member 72. Thus, if U-shaped resin member 72 is extruded, angled grooves 74 must be formed after extrusion by, for example, machining. If U-shaped resin member 72 is formed by casting, angled grooves 74 can be formed during the casting process. Angled grooves 74 may be oriented at angles that do not make right angles with angle of contact 70. For example, if it is desired to lift or depress inner edge 46 (Fig. 2), then the angle of angled grooves 74 may be changed to accomplish this result. It is also within the contemplation of the invention to orient angled grooves 74 parallel to angle of contact 70. With this arrangement, enlarged portions 60 (Fig. 5) tend to ride within grooves 68. If the overdrive is increased above the design point as a result of changing environmental or other conditions, enlarged portions 60 tends to climb out of angled grooves 74. When this occurs, an increase in cumulative friction tends to return the overdrive to the design point. It is further within the contemplation of the invention to provide two sets of angled grooves 74, one aligned generally with angle of contact 70, and the other inclined at a different angle to angle of contact 70. The second set may be at right angles, or at some other angle, to angle of contact 70 according to the principles discussed above. It is likely that the two sets of angled grooves 74 are preferably at right angles to each other, but this is not a requirement of the present invention. Relative angles other than 90 degrees are within the contemplation of the invention. It will be evident that the present invention is directed toward increasing the amount of driving force that can be transmitted to conveyor belt 20. As described above, this increased driving force may be used to increase the speed at which belt 20 is advanced. It would be clear to one skilled in the art that the increased driving force is equally useful for driving a more heavily loaded belt 20 at the same speed, or even lower speed. Referring now to Figs. 7A and 7B, a plastic belt 75 of the prior art is made of links consists of main links 76 and end links 77 connected by rods 78. Rods 78 have heads 80 which may protrude. However, the manufacturer of this type of belt, KVP Systems of Rancho Cordoba, California does not recommend this type of belt for use in spiral conveyor systems because they feel that heads 80 are not strong enough to withstand the loads typical of spiral conveyors. Referring to Figs. 8A and 8B, another plastic belt, shown generally at 79, made of links manufactured presently by the KVP Systems consists of main links 76 and end links 77 connected by rods 78. End links 77 are reenforced by reenforcement links 82 which are connected to rods 78. Heads 84 are countersunk in depressions 86. This type of the belt is recommended by the KVP Systems for the spiral conveyors. However, due to a lack of sufficient friction, adequate drive forces cannot be transmitted efficiently by this type of the plastic belt. The lack of the sufficient friction is a consequence of a low coefficient of friction characteristic for plastics. An attempt to increase the friction by increasing the longitudinal tension exposes this type of belt to excessive loads. Referring to Figs. 8'A and 8'B, a plastic belt 87 of the prior art, includes plastic links 89 such as those manufactured by the Intralox, Inc. Links 89 form a lattice-like structure having horizontal bars 93. Crossbars 91 are added to make the structure rigid. Crossbars 91 protrude beyond horizontal bar 93, forming protrusions 95, to add the rigidity and strength to the structure. They protrude beyond the sides of link 89 as well, as is seen in the top view in Fig. 8'A. Links 89 are connected to each other by rods 78, which have button-like retainers to hold rods 78 in place. Belt 87 is driven by a sprocket wheel which co-acts with a central portion of belt 87. This belt is a straight, rigid band, suitable for use in straight, not spiral, conveyors. The edge of this belt does not co-act with any driving mechanism, like a capstan, and is not functional in that sense. Protrusions 95 are not designed to engage in frictional contact with a driving mechanism. The present invention includes edge treatments of plastic conveyor belts to allow transfer of driving force to the conveyor belt, especially for spiral conveyors. To further improve the transfer of the driving force to the conveyor belt, the present invention provides for the use of a plastic belt with a textured edge. The textured edge of the plastic belt may be used together with a textured capstan. These edge treatments are shown in more detail in Figs. 9-16. Figs. 9A and 9B show top and side views, respectively, of a portion of an edge of a plastic belt 88 interacting with the capstan according to one of the embodiments of the present invention. To increase the friction between the edge of the belt 88 and the capstan, reenforcement links 82 have a buttons 90 protruding therefrom. Buttons 90 preferably have rounded edges. One button may be placed either on every reinforcement link 82, or on chosen reinforcement links 82 to achieve the desired co-action with the capstan. Instead of a button 90, any other shape of the protrusion increasing the friction and, at the same time, facilitating frictional engagement of the edge with the capstan so that belt 88 can be utilized in spiral conveyors. For example, vertical ridges, may be substituted for buttons 90. The edges of the protrusions may be rounded to eliminate angled surfaces which may be difficult to disengage from the capstan. In spiral conveyors using overdrive, the ability for the elements of the textured edge to disengage from the capstan is very important. Therefore, the edge of a belt must provide suitable disengagement as well as suitable engagement with the capstan. Protrusions having rounded shapes permit such engagement and disengagement. Such protrusions may be either molded, or attached to the belt separately. I.e., they may be so-called "field attached" elements that can be retrofitted to existing belts. Reenforcement links 82 may be flat plates, as it is shown at Fig. 9A, or they may be of any other shape useful in the present application. Referring now to Figs. 10A and 10B, there is shown, generally at 92, a portion of an edge of a belt of the present invention having reenforcement links 82. Preferably, the belt is made of plastic. Field attached buttons 94 may be attached by any chosen means to reenforcement links 82. For example, they may be glued, threaded, welded, etc. The material of buttons 94 may be plastic, metal, ceramics or other suitable material. Figs. 11A and 11B show top and side views, respectively, of an edge of a conveyor belt, shown generally at 96, (optionally made of plastic) which interacts with the capstan according to one of the embodiments of the present invention. Reinforcement links 82 are secured by extended rods 98 extending past reenforcement links 82. Extended rods 98 may be made of metal, plastic, co-extruded material (metal core with plastic body) or any other suitable material. Figs. 12A and 12B show tops and side views, respectively, of an edge of a conveyor belt which interacts with the capstan according to a further embodiments of the present invention. This embodiment is similar to the embodiment shown on Figs. 9A and 9B, except that end links 77 are not reenforced with reenforcement links 82. Therefore, buttons 90 are attached directly to end links 77. According to the invention, end links 77 may be flat plates, or they may be of any other shape useful in the present application. Figs. 13A and 13B show tops and side views, respectively, of an edge of the conveyor belt which interacts with a capstan according to one of the embodiments of the present invention. This embodiment is similar to the embodiment shown on Figs. 10A and 10B, except here, end links 77 do not have reenforcement links 82. Therefore, field-attached buttons are attached to end links 77. Field-attached buttons 94 are of partially spherical shape, and have rounded edges to ease the interaction with the capstan. Figs. 14A and 14B show top and side views of an edge of the conveyor belt which interacts with a capstan according to one of the embodiments of the present invention. This embodiment is similar to the embodiment shown on Figs. 11A and 11b, except here, end links 77 are not reenforced with reenforcement links 82. Extended rods 98 extend past end links 77 to contact the surface of a capstan. Figs. 15A and 15B and 16A and 16B show top and side views of an edge of a conveyor belt which interacts with a capstan according to further embodiments of the present invention. On Figs. 15A and 15B, generally at 100, there is shown a portion of an edge of the belt of the present invention. Rods 78 have protruding heads 102 protruding past links 77. Protruding heads 102, may be given the shape of buttons, partially spherical shapes, or may have any other rounded shape. These shapes provide smooth engagement with the capstan. Rods 78 can be made of different materials, and can be factory or field installed. On Figs. 16A and 16B, generally at 104, there is shown a portion of the belt of the present invention having rods 78 with protruding heads 102 extending past end links 77. Heads 102 are rounded and button-like to provide a smooth engagement with the capstan. Rods 78 can be made of different materials, and can be factory or field installed. Heads 102, as well as all button-like shapes described above, may have partly spherical outer surfaces. Referring to Fig. 17, there is shown, generally at 106, a portion of a metal conveyor belt for spiral conveyors of a prior art. It consists of rods 108 connected with the help of links 110. This belt has a longitudinal pitch X. The longitudinal pitch X is typically either 3/4 of an inch, or one inch. The longitudinal pitch greater than one inch is not used for metal belts for spiral conveyors presently, because their ability to be driven is poor. The increased longitudinal pitch is a problem for plastic belts as well. On Fig. 18, there is shown, generally at 112, a portion of a plastic belt for spiral conveyors of a prior art. It consists of links 114 connected with rods 108. The longitudinal pitch of this belt is indicated by Y. The largest pitch available for plastic belts for spiral conveyors is two inches. Using such belt with the pitch greater than two inches would cause difficulties with its driving. Referring to Fig. 19, there is shown, generally at 116, a portion of a metal belt according to one embodiment of the present invention. It consists of rods 118 connected with end links 120. The longitudinal pitch of this belt is inducated by X. It is greater than one inch, and is typically three inches. Heads of rods 122 protrude and provide an aid to drive the belt. In addition, protrusions 124 are placed on links 120 to enhance the belt's ability to be driven. Protrusions 124 are made here as buttons with rounded edges, but they may be of any shape. Referring to Figs. 20 A and 20B, there is shown, generally at 96, an edge of a plastic conveyor belt according to one embodiment of the present invention. It consists of main links 76 connected with rods 78 which have protruding heads 102. End links 77 have buttons 90 to increase a driving force to drive the belt. The longitudinal pitch of this belt is four inches, as it is indicated on the Fig. 20A. There may be just one button 90, or several of them, or none, depending on the requirements as to a particular belt with a particular pitch. Placement of the buttons 90 on end links 77 greatly enhances the ability to be driven for belts with pitches greater than two inches, e.g., for belts having longitudinal pitches from 3 to 6 inches. Therefore, placement of protrusions along an inside edge of plastic and metal belts will greatly enhance their ability to be driven. All belt embodiments described above may be used for belts with the longitudinal pitch greater than one inch for predominantly metal belts, and greater than two inches for predominantly non-metal belts. Additional protrusions may be placed in these cases on the edge of belts, e.g., on their end links, reenforcement links, etc., to improve belts, driving characteristics. All the edge treatments illustrated on Figs. 9A-16B, 19, 20A and 20B may have protrusions either on every link, or on chosen links to achieve satisfactory performance. The protrusions can be disposed at any convenient center-to-center distance (particularly helpful in facilitating field installation) as long as adequate drive friction is provided. The protrusions may be made of any convenient material such as, for example, plastic, metal, ceramics, combination of those, and co-extruded materials. The protrusions can be molded together with the end links, reenforcement links, rods, or other surface designed to engage the capstan, or they may be field installed. The shapes of the protrusions are not limited to the shapes shown on Figs. 9A-16B, 19, 20 and 20B. They may include vertical ridges, buttons, rods, teeth, or any other type of protrusions which provides satisfactory drive friction and strength when used in a spiral conveyor systems. All of the edge treatments of the present invention are applicable to a wide range of belt styles. They are not restricted to plastic belts, and may be used in metal, ceramic, or belts of other material. The conveyor belts of the present invention may comprise main links of different configurations, and end units, or links, and reenforcement links, may be either flat plates, or of any other shape useful in the present invention. To obtain improved transfer of the driver force to the belt, the present invention provides for a system consisting of the belt having protrusions on its edge, and a co-acting textured capstan. This combination provides improved friction between the capstan and the edge of the belt, resulting in better transmission of the drive force. When such a combination is used, it is possible to greatly improve the utility of plastic belts in spiral conveyor systems. The types of protrusions used include the embodiments shown at Figs 9-16, 19, 20A and 20B. The combination of the textured capstan and textured conveyor's edge permit the use of protrusions made of plastic which would be too brittle to use in the spiral conveyors. Such a combination also permits greatly improved drive efficiency, belt life and applicability of plastic belts to spiral conveyors. The edge treatments of the present invention in plastic belts also permits their use with smooth capstans.

Claims: A spiral conveyor system, comprising : a capstan (12) rotatable about a vertical axis (14), the capstan including a plurality of circularly spaced capstan bars (44,62), the bars having outer surfaces forming the general peripheral cylindrical driving surface of the capstan, a belt (88,92,96,100,104,126) having at its inner edge friction means (90,94,98,102) in contact with the outer surfaces of the capstan bars for the frictional driving of the belt by the rotation of the capstan through the spiral belt run, characterized in that, the belt is of the type comprising a succession of plastic link units (76) mounted and interconnected side by side and end on end whith each other, the link units being of the type telescoping with each other at a belt side inner edge, end links (77) on the inner edge of the belt are provided and interconnected to the plastic link units (76) and bear said friction means (90,94,98,102) at their end edge, the belt side surface and the peripheral driving surface of the capstan comprising cooperating friction means formed by protrusions provided on one surface coacting with grooves provided on the other surface. A spiral conveyor system according to claim 1 characterized in that the outer surfaces of the capstan bars (44,62) forming the general peripheral cylindrical driving surface of the capstan are substantially flat and provided with friction means (68,74) thereon. A spiral conveyor system according to claim 1 or 2 characterized in that friction means provided on capstan bars are formed by grooves (68,74). A spiral conveyor system according to claim 3 characterized in that grooves (68) are provided parallely to the length of the bars. A spiral conveyor system according to claim 3 characterized in that grooves (74) are provided at angle with the length of the bars. A spiral conveyor system according to one of the preceding claims characterized in that protrusions (90, 94, 98, 102) are provided and disposed on the inner edge of said belt on said end links (77).

Inventors: IRWIN GUY L, IRWIN, GUY L.
Applicants: IRWIN GUY L, IRWIN, GUY L.
Application year: 1990
Main classification: B65G21
IPC codes: B65G15, B65G17, B65G23, B65G21