A drive unit for an article transfer system

Abstract: A drive unit for a roller-type conveyor system which comprises a drive gear (80) mounted on a drive shaft (68) within heat sink plates (60, 62) and driving a number of pinion gears (82) connected to a pinion shaft (84) each of which is connected to a roller by crimping with a flexible shaft. A tangential drive frangible sprocket wheel (90) is directly connected to the drive shaft (68). A number of transport mechanisms containing rollers and a drive unit as just described are mounted together to form a conveyor system. Should one drive unit of a set of drive units jam, the teeth of the respective sprocket wheel (90) are sheared so that the drive chain can slip over the sprocket wheel (90).

Description: Background of the Invention The invention relates to a drive unit for an article transfer system having a plurality of parallel rollers fixed in a planar array and forming a conveyor; a drive shaft supported for rotation having a drive gear disposed thereto; a driving sprocket disposed to said drive shaft; a plurality of pinion gears disposed in a circular array around said drive gear to be driven thereby. A drive unit for such an article transfer or conveying system is described in US-A-4,313,536. Separate drive systems at various portions of the rollertype conveyor systems allow flexibility in controlling the movement of articles. In this drive system, a drive shaft with a gear and a system of pinion gears driven thereby are mounted on thin mounting plates. The pinion gears drive rigid shafts which, in turn, are connected to the rollers via flexible shafts. The drive shaft is enclosed within bushings located between the thin mounting plates. The sprocket wheel used on the device of US-A-4,313,536 requires multiple "hang loads" on the drive shaft, including the bearing and washers abutting the sprocket wheel, as well as the spring and washers abutting the end bolt for making up the clutch-type mechanism for engaging the sprocket wheel to the drive shaft. Thus, a significant vertical load is applied to the drive shaft thereby contributing to the bending stress on the drive shaft. Further, the sprocket wheel is of a design requiring an increased pressure from the chain to drive the sprocket wheel further contributing to the undesirable stresses, including bending and torsion stresses, exerted on the drive shaft. Still further, sets of rollers operated by a single chain can jam when debris or an article is caught between a set of rollers operated by a drive unit since the sprocket wheel cannot stop the drive unit under such conditions. According, there is a need for an efficient, economical, simply constructed and easily installed improved conveyor drive unit for providing a much reduced load applied on the drive shaft. It is the object of the present invention to provide a drive unit for an article transfer system precluding jamming of a set of rollers driven by a single chain when abnormal loads are experienced in the rollers. This object is achieved in that the driving sprocket is frangible and fixed to said drive shaft. Such a drive unit prevents jamming of a set of rollers driven by a single chain without necessitating the use of coupling means. If one drive unit should jam when debris or an article is caught between a set of rollers operated by the drive unit, the driving sprocket of that drive unit will break, thereby allowing the chain to continue with its movement. The improved conveyor drive unit of the present invention is used for driving a planar array of a plurality of rollers preferably located to one side of the rollers whereby a flexible coupling connects each of the rollers with one of the pinion gears for driving the rollers. Such a drive unit can be rapidly and easily installed in a roller-type article transfer system. A very simple embodiment of the invention is provided when the driving sprocket has frangible sprocket teeth. The vertical load applied on the drive shaft is reduced if said frangible driving sprocket operates on a tangential drive. This reduces the vertical load applied on the drive shaft. The force exerted on the drive shaft and the force required to pull the sprocket means are both reduced, if that said frangible driving sprocket is a zero-degree of involute type sprocket. This also minimizes the "hang load" on the drive shaft, thereby further reducing the vertical load applied on the drive shaft. Preferably the frangible driving sprocket is made of a lubricant-impregnated nylon composition. Brief description of the drawings Figure 1 is a side elevational view of a drive unit in accordance with the prior art; Figure 2 is a cross-sectional view of the drive unit of Figure 1, including an illustration of an associated chain for driving the sprocket wheel and an associated bolt for mounting the drive unit; Figure 3 is a side elevational view of an improved conveyor drive unit in accordance with the present invention showing the mounting plates and sprocket means mounted on a drive shaft; Figure 4 is a partial cross-sectional view in accordance with the present invention showing at least one associated crimped shaft mounted on the mounting plates, and a sprocket means pinned on the drive shaft; and Figure 5 is a perspective view of the improved conveyor drive unit in accordance with the present invention. Description of the preferred embodiments Attention is first directed to Figure 1 which shows a drive unit as shown in US-A-4,313,536, generally referred to by reference number 1. The drive unit 1 has mounting plates 3, 5, 7 and 9 spaced apart by spacers 11, 13 and 15. A plurality of pinion shafts 18 are mounted on mounting plates 3, 5, 7 and 9. A driven shaft 24 is mounted on the mounting plates 3, 5, 7 and 9 and accommodates a sprocket wheel 26. Thrust washers 28 and 30 adjacent to the sprocket wheel 26 are further mounted on the drive shaft 24. A spacer or bearing 31 is seated on the drive shaft 24 adjacent the thrust washer 28. Thrust washer 30 is biased against sprocket wheel 26 by spring 32 which bears against washer 34 which, in turn, is secured to drive shaft 24 by means of bolt 36. As more clearly shown in Figure 2, one end of each pinion shaft 18 is bored and squared to receive a flexible shaft 38. Each flexible shaft 38 is connected to a conveyor roller (not shown). The drive shaft 24 rides in bushing 39 mounted between mounting plates 5 and 9. Drive gear 40 is affixed to drive shaft 24 by means of a key 42. Disposed in a circular array for meshing around driven gear 40 are a plurality of pinion gears 44 which are fixed to pinion shafts 18. Mounted between mounting plates 5 and 9 are bushing 46 for accommodating the pinion shafts 18. A pair of holes are drilled through drive shaft 24 on either side of the sprocket wheel 26 and pins 48 and 50 are inserted therethrough over which thrust washers 28 and 30 are inserted. Thus, thrust washers 28 and 30 are mounted on drive shaft 24 in a manner wherein they are fixed relative to the rotation of the drive shaft 24, but at least one of the thrust washers 28 and 30 is axially movable on the drive shaft 24. The sprocket wheel 26 causes the thrust washers 28 and 30 to begin turning when a given force is applied by pressing the thrust washers 28 and 30 against the sprocket wheel 26. Once motion has begun, the thrust washers 28 and 30 are forced against the sprocket wheel 26 and remain turning. The pinion shafts in the unit of US-A-4,313,536 are mounted on the thin mounting plates 3, 5, 7 and 9 while the drive shaft is enclosed within bushing 39. Thus, the rotating driven shaft 24 and the sprocket wheel 26 generate heat which cannot be dissipated by the thin mounting plates 3, 5, 7 and 9 thereby retaining the heat therein which can lead to the annealing or weakening of the aforesaid elements. Further, the construction of the drive unit 1 imposes multiple "hang loads" on the drive shaft 24, including the bearing or spacer 31, washers 28, 30 and 34, spring 32 and end bolt 36. The various elements which make up the hang loads when combined contribute to the vertical load exerted on the drive shaft 24 which results in unnecessary bending stress thereon. Further, the sprocket wheel 26 is not tangentially driven thereby requiring higher pressure from the chain 52 in order to drive the same. Thus, undesirable stresses, including torsion stress, exerted on the drive shaft exist. Also, the drive unit 1 includes a non-frangible sprocket wheel 26 which can lead to sets of rollers operated by a single chain 42 to jam when debris or an article is caught between a set of rollers operated by the driven unit 1. Figure 3 shows the improved conveyor drive unit of the present invention, generally designated by reference number 58. The conveyor drive unit 58 comprises heat sink plates 60 and 62 and spacers 64 and 66 therebetween. The ratio between the thickness of each of the heat sink plates 60 and 62 and the diameter of the drive shaft 68 can be 1:1 or 1:2. The drive shaft 68 is journalled in heat sink plates 60 and 62 which have bosses 63 and 65 which provide further support for the drive shaft 68, thereby not necessitating the enclosure of the drive shaft 68 in the bushings 39 as in the aforementioned prior drive unit. Spacers 69 and 70 are mounted between heat sink plates 74 and 76. Spacer 70 is preferably made of stainless steel and has a threaded aperture 72 passing therethrough for accommodating bolts (not shown) when the drive unit 58 is mounted. A drive gear 80 is fixed to drive shaft 68. A plurality of pinion gears 82 which are fixed to pinion shafts 84 are disposed in a circular array for meshing around drive gear 80 (see Figure 4). As better illustrated in Figure 4, the pinion shafts 84 of the drive unit 58 of the instant invention have crimped portions 86 for connecting therein flexible shafts connected to the conveyor rollers (not shown). Further, the pinion shafts 84 substantially extend between, and are journalled in, heat sink plates 60 and 62 so that the end of the pinion shafts 84 which have a higher strength than the flexible shaft connected thereto can better withstand the shear and fatigue stresses during rotation than the arrangement taught in the above-discussed US-A-4,313,536 wherein a portion of the flexible shafts 38 is rotated within the apertures passing through the mounting plate 3. Further, the crimping of the flexible shafts to the pinion shafts 84 within the confines of the heat sink plates 60 and 62 similarly provides for a stronger coupling. Further shown in Figure 4 is a sprocket wheel 90 having an integral end piece 92 with an aperture 94 passing therethrough for accommodating a pin 96 for mounting the sprocket wheel 90 onto the drive shaft 68. Spacers 64, 66, 69 and 70 have a bolt 98 with a threaded end passing therethrough for mounting thereof between the mounting plates 60 and 62. As shown in Figure 4, the drive shaft 68 only has the sprocket wheel 90 mounted thereon, unlike the driven unit shown in US-A-4,313,536. Thus, significant reduction in the vertical load on the drive shaft 68 is accomplished. The sprocket wheel 90, as in Figure 5, is a zero-degree involute gear, i.e., one which has a zero-degree pressure angle capable of operating on a tangential drive. Thus, practically no bending stress or torsion stress is applied on the drive shaft 68 when the chain drives the sprocket wheel 90. Thus, the torque applied by the chain on the sprocket wheel 90 having a zero-degree pressure angle, as opposed to a 14 1/2 - degree pressure angle, is reduced by 10 to 15 percent, thereby providing a significantly smooth and much improved driving of the sprocket wheel 90. The sprocket wheel 90 is made of plastic known under the trademark "Nylatron" which is generally a nylon material impregnated with lubricant, such as molybdenum disulfide. Further, the sprocket wheel is frangible, i.e., the teeth can be sheared, thereby stopping the set of conveyor rollers being driven by the affected drive unit 58. Thus, jamming of an entire set of conveyor rollers being driven by a single chain can be prevented by the shearing of the sprocket wheel teeth of a single drive unit.

Claims: A drive unit for an article transfer system having a plurality of parallel rollers disposed in a planar array and forming a conveyor; a driven shaft (68) supported for rotation having a drive gear (80) fixed thereto; a driving sprocket (90) disposed to said drive shaft (68); a plurality of pinion gears (82) disposed in a circular array around said driven gear (80) to be driven thereby; characterized in that said driving sprocket (90) is fixed to said drive shaft (68) and is frangible and breaks when abnormal loads are experienced in the rollers. A drive unit as defined in Claim 1, characterized in that the driving sprocket (90) has frangible sprocket teeth. A drive unit as defined in Claim 1, characterized in that said frangible driving sprocket (90) operates on a tangential drive. A drive unit (58) as defined in Claim 1, characterized in that said frangible driving sprocket (90) is a zero-degree of involute type sprocket. A drive unit (58) as defined in Claim 1, characterized in that said frangible driving sprocket (90) is made of a lubricant-impregnated nylon composition.

Inventors: BARKLEY PAUL E, FAUTH FREDERICK E SR, BARKLEY, PAUL E., FAUTH, FREDERICK E., SR.
Applicants: AMERICAN BOTTLERS EQUIP, AMERICAN BOTTLERS EQUIPMENT CO. INC.
Application year: 1990
Main classification: B65G13
IPC codes: B65G13