APPARATUS FOR DRIVING ROLLERS OF ROLLER HEARTH KILN

Abstract: The rollers (1) of a roller hearth kiln are coupled to driving shafts (2) extending horizontally away from the kiln. A casing (5) extending along the kiln houses the ends of the driving shafts (2), and vertical sprocket wheels (4) driven by a chain (8) are mounted on the ends of the driving shafts in the casing. To avoid risk of floating of the chain away from the sprocket wheels (4), rail (7) is secured to the bottom of the casing (5) so as to extend below the sprocket wheels (4), and the driving chain (8) moves on the rail while engaging the sprocket wheels (4) from below.

Description: This invention relates to an apparatus for driving the rollers of a roller hearth kiln which is used for making ceramic products such as for baking tile green ware. US-A-3608876 describes such an apparatus, corresponding to the first part of present claim 1. In a conventional method for driving the rollers of a roller hearth kiln, a sprocket wheel is secured to the free end of each driving shaft of the roller and a long driving chain runs while engaging the sprocket wheels from above. In this method, the pitch of the driving chain must coincide with that of the sprockets. Even when they are in coincidence in the beginning, the driving chain is susceptible to an elongation after a long period of operation, and such elongation results in an increase of the driving chain pitch which leads to a difference in pitch between the driving chain and the sprockets. Difficulties have been experienced in that the driving chain tends to float due to the above difference in pitch between the sprockets and the driving chain, and such floating of the driving chain is detrimental to accurate drive of the rollers. Japanese Utility Model Laying-open Publication No. 9233/1972 proposed a modification of the roller driving apparatus. According to this modification, a continuous long case is provided on one side of the roller hearth kiln so as to house the sprocket wheels secured to the driving shafts of the rollers. Cushion rubber pieces are mounted on the lower surface of a top lid of the case in such a manner that each rubber piece urges the driving chain against the corresponding sprocket wheel so as to prevent the driving chain from floating. However, the above modification has a number of shortcomings; namely, an additional load to the driving chain, difficulty in giving a proper tension to the driving chain, possibility of irregularity in roller rotation due to wear of the cushion rubber piece, and an increased complication in maintenance and repair such as removal of the top lid of the case which removal requires at least a partial stop of the roller hearth kiln. Therefore, an object of the invention is to obviate the above-mentioned difficulty and shortcomings of the prior art by providing an improved apparatus for driving the rollers of a roller hearth kiln. The apparatus according to the invention can ensure reliable transmission of driving power to the sprocket wheel of each roller, may need no additional torque as compared with the prior art, facilitates easy application of proper tension to the driving chain, and is easy to maintain and repair. Besides, the apparatus of the invention can be produced at a low cost. An apparatus for driving rollers of a roller hearth kiln according to the invention is set out in claim 1. The rail is disposed directly or indirectly on the bottom of the case. Since the driving chain runs on the rail, it never floats or moves away from the sprocket wheels, so that smooth transmission of the driving power to the sprocket wheels is always ensured. With the tensile sprocket wheels, a proper tension can be easily applied to the driving chain, and proper engagement of the driving chain with the sprocket wheels of the driving shafts can be ensured. Thus, the use of the conventional cushion rubber pieces is completely eliminated together with shortcomings associated therewith. For a better understanding of the invention, reference is made to the accompanying drawing, in which the single figure is a schematic sectional view of an apparatus according to the invention, which view is taken at right angles to longitudinal direction of a roller hearth kiln. In the figure, 1 is a roller, 2 is a driving shaft, 3 is a coupler, 4 is a sprocket wheel, 5 is a case, 6 is a bearing, 7 is a rail, 8 is a driving chain, 9 is a bottom plate, 10 is a tensile sprocket wheel, and 11 is a holder. In the embodiment of the single drawing, each roller 1 is driven by a corresponding driving shaft 2 which is coupled to the roller 1 by a coupler 3. It is understood that a plurality of parallel rollers 1 are disposed in a roller hearth kiln at a certain pitch, but only one of such rollers 1 is shown in the figure for simplicity. The axis of rotation of each roller 1 is at right angles to the longitudinal direction of the kiln. The driving shaft 2 of the embodiment carries a pair of sprocket wheels 4, 4 with a spacing therebetween. A case 5 extends along one side of the kiln so as to house sprocket wheels 4 carried by the driving shafts 2. The case 5 extends in the longitudinal direction of the kiln, so that the driving shaft 2 is journaled by bearings 6, 6 mounted on opposite sidewalls of the case 5. A pair of rails 7, 7 are disposed on the inner surface of the bottom plate 9 of the case 5 in such a manner that the two rails 7, 7 extend below the corresponding sprocket wheels 4, 4 of each driving shaft 2 respectively. A driving chain 8 runs on the top surface of each rail 7 while engaging the sprocket wheel 4 from below as shown in the single figure. After reaching the longitudinal end of the case 5, each driving chain 8 descends to the outside of the case 5 and returns to the opposite longitudinal end of the case 5 through a path under the bottom plate 9 so as to form an endless loop of the driving chain 8. At least one tensioning sprocket wheel 10 is rotatably supported by an adjustable holder 11, which holder 11 is secured to the bottom plate 9 of the case 5 and is capable of holding the tensioning sprocket wheel 10 on the return path of the driving chain 8. Thus, the driving chain 8 engages the tensioning sprocket wheel 10 on its return path under the bottom plate 9, and a suitable tension is given to the driving chain 8 from the tensioning sprocket wheels 10, the plurality of sprocket wheels 10 are arranged in such a manner that the driving chain 8 may extend along a zigzag path while engaging such tensile sprocket wheels 10. In operation, when the driving chain 8 runs, all the rollers 1 engaging the driving chain 8 are rotated at an identical revolving speed on the same direction by the transmission through the sprocket wheels 4, in the same manner as in the case of prior art. The apparatus of the invention does not require precision in the coincidence of the pitch of the sprockets of the sprocket wheel 4 with the pitch of the driving chain 8 because the distance between the driving chain 8 and the rollers 1 is always kept constant, while such coincidence has been necessary with the prior art. The apparatus of the invention also eliminates the risk of floating of the driving chain 8 away from the sprocket wheel 4 even if the driving chain 8 is somewhat elongated after use, because the driving chain 8 runs on the rail 7. Thus, the invention ensures reliable power transmission from the driving chain 8 to the rollers 1. Further, the location of the return path of the driving chain 8 under the case 5 facilitates the application of a proper tension to the driving chain 8 and easy maintenance of the driving chain 8. As compared with the conventional structure of urging the driving chain 8 against the sprocket wheels 4 by the cushion rubber pieces secured to the inside surface of a top lid of the case 5, the apparatus of the invention is free not only from the extra load of urging the driving chain 8 but also from any troubles due to wearing of the cushion rubber pieces, so that its maintenance is very easy and its production cost can be reduced. In the illustrated embodiment, the rail 7 is disposed directly on the bottom plate 9 of the case 5, but it is also possible to secure a suitable mounting member for the rail 7 on the inside surface of the case 5 so as to provide a spacing between the inside surface of the case 5 and the rail 7. As described in detail in the foregoing, the apparatus of the invention ensures reliable power transmission from a driving chain to sprocket wheels secured to the driving shafts for rollers, requires no extra torque for urging the driving chain toward the sprocket wheels, facilitates easy application of a proper tension to the driving chain and easy maintenance, and reduces the production cost. Thus, the invention obviates the difficulties and shortcomings of the prior art and contributes greatly to the industry. Although the invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in details of construction and the combination and arrangement of parts may be resorted to.

Claims: An apparatus for driving the rollers (1) of a roller hearth kiln comprising:- a plurality of driving shafts (2) each coupled, at one end, to a corresponding one of the rollers; a sprocket wheel (4) provided on each of the driving shafts (2) at the other ends; a case (5) extending along the kiln so as to house the ends of the driving shafts with the sprocket wheels; a rail (7) extending along the bottom of the case beneath the sprocket wheels; and an endless driving chain (8) which is capable of moving along the rail while engaging the sprocket wheel from below and which has a return path outside the case; characterized in that the apparatus also comprises a plurality of tensioning sprocket wheels (10) rotatably supported by adjustable holders (11) secured to the outside of the case (5) so that the tensioning sprocket wheels (10) engage the driving chain (8) during its return path so as to apply a tension to the driving chain, the return path lying under the case (5) and being a zig-zag path. An apparatus according to claim 1 wherein an additional sprocket wheel (4) is provided on each of the driving shafts close to the other sprocket wheel and spaced therefrom, an additional rail (7) is provided, extending along the bottom of the case below the additional sprocket wheels, and an additional endless driving chain (8) is provided which is capable of moving on the additional rail while engaging each of the additional sprocket wheels from below. An apparatus according to claim 2 wherein at least one additional tensile sprocket wheel (10), rotatably supported by the adjustable holder (11) engages the additional driving chain during part of its return path so as to apply a tension to the chain.

Inventors: KAJIURA, YASUHIRO
Applicants: NGK INSULATORS, LTD.
Application year: 1987
Main classification: F27B9
IPC codes: F27B9, F16H7