Drive Wheel Conveyor

Abstract: A drive wheel conveyor comprising a tubular side frame (11) extending in a transport direction and having an inner side wall (21), outer side wall (22), top wall (23) and bottom wall (24); a drive shaft (41) supported by the inner (22) and outer side walls (23) so as to extend through the side frame (11), transversely thereof and having an inward projection (49) extending inward through the inner side wall (21); a sprocket (45) fixed to the drive shaft (41) and positioned between the inner (21) and outer side walls (22); an endless drive chain (46) in engagement with the sprocket (45) and disposed inside the side frame (11) so as to be movable in circulation; and a transport wheel (51) having a shaft bore (53) with the inward projection (49) fitted therein and drivable by frictional resistance between the inner periphery of the wheel (51) defining the shaft bore (53)and the outer surface of the inward projection (49).

Description: BACKGROUND OF THE INVENTION The present invention relates to a drive wheel conveyor comprising: a tubular side frame extending in a transport direction and having an inner side wall, an outer side wall, a top wall and a bottom wall, a drive shaft supported by the inner and outer side walls so as to extend through the side frame transversely thereof and having an inward projection extending inward through the inner side wall, a sprocket fixed to the drive shaft, an endless drive chain in engagement with the sprocket so as to be movable in circulation, and a transport wheel having a shaft bore with the inward projection fitted therein and drivable by frictional restistance between an inner peripheral surface of the transport wheel defining the shaft bore and the outer surface of the inward projection. A drive wheel conveyor of this kind is disclosed in EP-A-⊘ ⊘51 867. This drive wheel conveyor comprises a tubular side frame with two U-shaped elements defining an inner side wall, an outer side wall, a top wall and a top bottom wall. A drive shaft is supported by the side walls so as to extend through the side frame transversely thereof and has an inward projection extending through the inner side wall. The projection carries a transport wheel, which is fitted around the drive shaft and drivable by frictional resistance between the transport wheel and the drive shaft. The other end of the drive shaft projects outward of the side frame into a space, which is defined by the two legs of the outer U-shaped elements and carries a sprocket having an endless chain in engagement therewith. The space defined by the two U-legs is closed by a cover in order to prevent the sprocket and endless drive chain assembly from being soiled. However, the known drive wheel conveyor structures is sometimes considered to be too big and susceptible to disturbances. For example there is the likelihood, that the endless chain becomes disengaged from the sprocket, so that the cover has to be removed for reassembling the chain, which leads to long standstills of the conveyor. Accordingly it is the object of the invention to provide a drive wheel conveyor which is compact in design and not susceptible against disturbances. According to the present invention this object is solved in that the sprocket and the endless drive chain in engagement therewith are positioned between the inner and outer side walls, the top wall is formed with a slit extending in the transport direction and a top cover is attached to an upper surface of the top wall to close the slit, a chain guide rail being attached to and depending from the lower surface of the top cover. According to the invention the space inside the tubular side frame is used for accommodating the sprocket and the endless According to the invention the space inside the tubular side frame is used for accommodating the sprocket and the endless drive chain, so that a very compact structure is obtained. Moreover, the provision of a guide rail for the endless chain obviates the likelihood of the chain becoming disengaged from the sprocket, so that the most important source of disturbances in operation is eliminated. Thus the drive wheel conveyor of the present invention is compact in design and very reliable in comparison with the state of the the art conveyors. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a conveyor embodying the invention; and FIG. 2 is a cross sectional view of a side frame and a transport unit which are included in the conveyor. DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a drive wheel conveyor which comprises a pair of opposite side frames 11 extending longitudinally of the conveyor and each in the form of a tube of rectangular cross section, and a pair of opposite rows of transport units 12 which rows are provided on the respective side frames 11. Pallets P carrying workpieces W thereon are supported at their opposite sides by these rows. The transport units 12 in each row are arranged at a spacing longitudinally of the side frame 11. The opposite side frames 11, as well as the rows of transport units 12, are of the same construction although oriented in different directions, so that the following description will be given of the right side frame 11 and one transport unit 12 shown in FIG. 2. The side frame 11 is in the form of a rectangular tube extending longitudinally of the conveyor, and comprises an inner side wall 21, outer side wall 22, top wall 23 and bottom wall 24. The inner side wall 21 has a large bearing hole 25, and the outer side wall 22 is formed with a small bearing hole 26, these holes 25, 26 being arranged concentrically. A large bearing 27 is fitted in the large bearing hole 25 with a housing 28 provide between the bearing and the side wall, while a small bearing 26 is fitted directly in the small bearing hole 26. The top wall 23 is centrally formed with a slit 31 extending longitudinally thereof. The slit 31 is closed with a cover 32, which is provided with an upper chain guide rail 33 depending therefrom. A pallet guide 34 is attached to the upper surface of the cover 32 at its inner end. A lower chain guide rail 35 is provided on the upper surface of the bottom wall 24 centrally thereof. The transport unit 12 has a drive shaft 41 extending through the side frame 11 transversely thereof. The drive shaft 41 includes a large-diameter portion 42 positioned at the middle of its length and supported by the large bearing 27, a small-diameter portion 43 close to the shaft outer end and supported by the small bearing 29, and a medium-diameter portion 44 between the large-diameter portion 43 and the small-diameter portion 43. A sprocket 45 is fixed to the portion 44 with a key. An endless chain 46 extending inside the side frame 11 longitudinally thereof has a portion thereof engaged with the sprocket 45 when traveling along an upper path. The outer end of the small-diameter portion 43 is covered with a metal cap 47. The large-diameter portion 42 has an inner end provided with a flange 48 and extending into an inward projection 49, which carries a transport wheel 51 thereon. More specifically, a friction ring 52 is fixed to the inward projection 49 with a key. The transport wheel 51 is formed with a shaft bore 53 having a bronze bush 54 inserted therein with a press fit. The bush 54 is slidably fitted around the friction ring 52. Provided between the inward projection 49 and the transport wheel 51 are dust seals 55 for covering a clearance between the outer surface of the friction ring 52 and the inner surface of the bush 54 to prevent extraneous matter from ingressing into the clearance. The inner end of the inward projection 49 is covered with a rubber cap 56. The inside diameter of the large bearing hole 25 is greater than the outside diameter of the sprocket 45. When the conveyor is assembled, the sprocket 45 is inserted into the side frame 11 through the large bearing hole 25. After the chain 46 has been engaged with the sprocket 45, the top cover 32 is attached to the side frame 11. Thus, a clearance sufficient to pass only the chain 46 therethrough is formed between the sprocket 45 and the guide rail 33. This obviates the likelihood of the chain 46 becoming disengaged from the sprocket 45. When the sprocket 45 is drivingly rotated by the chain 46, the drive shaft 41 rotates to drivingly rotate the transport wheel 51 by virtue of the frictional resistance between the outer surface of the friction ring 52 and the inner surface of the bush 54. When no external force acts on the pallet P as placed on the transport wheel 51, the pallet P is sent forward with the rotation of such transport wheels 51, whereas if the pallet P is subjected to an external force acting in a direction to hamper the movement of the pallet P, a slip occurs between the friction ring 52 and the bush 54 to stop the pallet P. With the construction described above, the drive mechanism other than the transport wheel 51, naemly, the drive shaft 41, the sprocket 45 and the chain 46 are all covered with the side frame 11. Accordingly, there is no likelihood of the worker becoming caught by the drive mechanism, nor is there any likelihood of extraneous matter ingressing into the side frame. Of course, the drive mechanism will not spatter oil or the like on the worker or the article being transported.

Claims: A drive wheel conveyor comprising: a tubular side frame (11) extending in a transport direction and having an inner side wall (21), an outer side wall (22), a top wall (23) and a bottom wall (24), a drive shaft (41) supported by the inner and outer side walls (21, 22) so as to extend through the side frame (11) transversely thereof and having an inward projection (49) extending inward through the inner side wall (21), a sprocket (45) fixed to the drive shaft (41), an endless drive chain (46) in engagement with the sprocket (45) so as to be movable in circulation, and a transport wheel (51) having a shaft bore (53) with the inward projection (49) fitted therein and drivable by frictional restistance between an inner peripheral surface of the transport wheel (51) defining the shaft bore (53) and the outer surface of the inward projection, characterized in that the sprocket (45) and the endless drive chain (46) in engagement therewith are positioned between the inner and outer side walls (21, 22), the top wall (23) is formed with a slit (31) extending in the transport direction and a top cover (32) is attached to an upper surface of the top wall (23) to close the slit (31), a chain guide rail (33) being attached to and depending from the lower surface of the top cover (32). A drive wheel conveyor as defined in claim 1, wherein the inner side wall (21) is formed with a bearing hole (25) in the portion thereof, where the drive shaft (41) extends through the inner side wall (21), and a bearing (27) having the drive shaft (41) extending therethrough is fitted in the bearing hole (25) by a housing (28). A drive wheel conveyor as defined in claim 1 or 2, wherein the drive shaft (41) has inner and outer ends each covered with a safety cap (56). A drive wheel conveyor as defined in any of claims 1 to 3, wherein a clearance between the bore-defining peripheral surface of the outer surface of the inward projection (49) has inner and outer ends each covered with a dust seal (47, 55).

Inventors: WAKABAYASHI TAKAO, WAKABAYASHI,TAKAO, WAKABAYASHI,TAKAO C/O NAKANISHI METAL WORKS CO.LTD
Applicants: NAKANISHI METAL WORKS CO, NAKANISHI METAL WORKS CO., LTD.
Application year: 1993
Main classification: B65G13
IPC codes: B65G13