The present invention relates to a transfer system for carrying out assembling of parts, while circulating a pallet with a work placed thereon along a transfer line forming a closed loop.
Such a transfer system for carrying out the assembling of parts, while circulating a pallet with a work placed thereon along a transfer line forming a closed loop is conventionally known (see Japanese Patent Publication No.4-57555). In the above known transfer system, a pallet-shaped carriage on which a work can be placed is circulated on rails placed along a quadrilateral transfer line. In this case, the carriage is allowed to travel by connecting and disconnecting an endless chain, circulatively driven along the rails by a drive source, to or from the carriage, or the carriage is allowed to travel pitch by pitch by bringing the carriage into and out of engagement with a rack which is reciprocally driven through a predetermined distance along the rails by a drive source, and during this time, the assembling of parts to the work placed on the carriage is carried out.
However, the above known system suffers from a problem that when the length of the transfer line is to be changed, it is necessary to change the length of the endless chain or of the rack provided along the transfer line, and such replacing work becomes of a large scale, resulting in a great deal of cost required.
Moreover, the known system also suffers from another problem that it is necessary to supply parts to be assembled to a work from the outside, to the carriage in succession and for this reason, it is difficult to enhance the working efficiency. To carry out the operation of assembling the parts to the work, working air is required for enabling lifting and lowering of the work to a level which makes the operation easy, or for driving an air tool such as an impact wrench. However, there is a problem that if the working air is supplied from the outside of the moving carriage, the handling or the attachment and detachment of an air hose is troublesome.
The present invention has been accomplished in view of the above circumstances, and it is a first object of the present invention to provide a transfer system for carrying out the assembling of parts, while circulating a pallet having a work placed thereon along a transfer line forming a closed loop, wherein the length of the transfer line can be changed to any other one without modification of a pallet driving device.
It is a second object of the present invention to provide a transfer system for carrying out the assembling of parts, while circulating a pallet having a work placed thereon along a transfer line forming a closed loop, wherein the operation of assembling parts to the work can be carried out efficiently.
To achieve the first object, according to a first aspect and feature of the present invention, there is provided a transfer system having transfer-in stations and transfer-out stations for assembling parts to a work on a pallet, while circulating the pallet along a transfer line forming a closed loop, the transfer system comprising a first conveyer and a second conveyer which are disposed in parallel to each other to transfer a plurality of pallets in an abutting state, a first traverser for transporting the pallets individually from a terminal end of the first conveyer to a start end of the second conveyer, and a second traverser for transporting the pallets individually from a terminal end of the second conveyer to a start end of the first conveyer, the first and second conveyers and the first and second traversers being disposed in the same horizontal plane to form the transfer line, the transfer-in stations and the transfer-out stations being disposed adjacent each other on or in the vicinity of the first and second traversers, the first and second conveyers being operable to drive the pallets by bringing friction rollers which are rotated by a drive source mounted at a fixed side, into abutment against the pallet.
With the above arrangement, the first conveyer, the first traverser, the second conveyer and the second traverser are disposed in the same horizontal plane to define the transfer line forming the closed loop for transferring the pallets, and the first and second conveyers drive the pallets by bringing the rotated friction rollers into abutment against the pallet. Therefore, the number of the pallets can be increased and decreased only by changing the lengths of the first and second conveyers without making any modification to the friction rollers, and thus it is extremely easy to change the length of the transfer system. Moreover, while keeping the structure simple and of a low cost, the generation of vibration and noises can be prevented to drive the pallet smoothly. In addition, the transfer-in stations and the transfer-out stations for carrying out the transfer of the work onto and out of the pallet are disposed adjacent each other on or in the vicinity of the first and second traversers. Therefore, most of the transfer line is used ensuring space and time for carrying out the assembling of the parts to the maximum, along which line the work can be transferred, whereby useless space and time required for returning of an empty pallet can be maintained to the minimum.
To achieve the first object, according to a second aspect and feature of the present invention, in addition to the first feature, the transfer-in station for transferring the work onto the pallet and the transfer-out station for transferring the work from the pallet are disposed adjacent to each other on or in the vicinity of the first and second traversers.
With the above arrangement, the transfer-in and out stations for transferring the work onto and out of the pallet are disposed adjacent each other on or in the vicinity of the first and second traversers. Therefore, most of the transfer line is used ensuring space and time for carrying out the assembling of the parts to the maximum, along which line the work can be transferred, whereby useless space and time required for returning of an empty pallet can be maintained to the minimum.
To achieve the first object, according to a third aspect and feature of the present invention, in addition to the first feature, the transfer-in station for transferring a part tray to the pallet and the transfer-out station for transferring the part tray from the pallet are disposed adjacent each other on or in the vicinity of the first and second traversers.
With the above arrangement, the transfer-in and out stations for transferring the part tray to and out of the pallet are disposed adjacent each other on or in the vicinity of the first and second traversers. Therefore, most of the transfer line is used ensuring space and time for carrying out the assembling of the parts to the maximum, along which line the part tray can be transferred, whereby useless space and time required for returning of an empty pallet can be maintained to the minimum.
To achieve the first object, according to a fourth aspect and feature of the present invention, in addition to the first feature, the first and second traversers include transfer means for transporting the work at a terminal end of either one of the first and second conveyers to a start end of the other of the first and second conveyers.
With the above arrangement, the work at the terminal end of either one of the first and second conveyers can be transported to the start end of the other of the first and second conveyers by the transfer means provided on the traversers and hence, the smooth transporting of the pallet can be carried out.
To achieve the first object, according to a fifth aspect and feature of the present invention, in addition to the fourth feature, the transfer means have transfer surfaces capable of being lifted and lowered relative to the bottom surface of the pallet on the first and second conveyers, between positions which are higher and lower respectively than the bottom surface of the pallet.
With the above arrangement, the transfer surface of the transfer means is lifted and lowered relative to the bottom surface of the pallet on the first and second conveyers, between positions which are higher and lower respectively than the bottom surface of the pallet. Therefore, the transporting of the pallet between the first and second traversers and the first and second conveyers can be conducted smoothly.
To achieve the first object, according to a sixth aspect and feature of the present invention, in addition to the fourth feature, the transfer system further includes a cylinder for pushing out the pallet from the terminal ends of the first and second traversers to the start ends of the first and second conveyers.
With the above arrangement, the pallet is pushed out from the terminal ends of the first and second traversers to the start ends of the first and second conveyers by the cylinder and therefore, the transporting of the pallet from the first and second traversers to the first and second conveyers can be conducted smoothly.
To achieve the first object, according to a seventh aspect and feature of the present invention, in addition to the first feature, the transfer system further includes an air tank which is mounted on the pallet and in which air for driving an air tool is stored, and an air supply means provided at least at one place on the transfer line for supplying air to the air tank.
With the above arrangement, the air tool can be driven by the air stored in the air tank mounted on the pallet and therefore, the handling of an air hose is simplified, and also the operability of the air tool is improved, as compared with a case where air is supplied from the outside of the pallet. Moreover, the air can be supplied to the air tank, while the pallet is being circulated along the transfer line. Therefore, the supplying of the air to the air tank can be conducted easily.
To achieve the second object, according to an eighth aspect and feature of the present invention, there is provided a transfer system having a transfer-in station and a transfer-out station for assembling parts to a work on a pallet, while circulating the pallet along a transfer line forming a closed loop, the pallet including a part support for supporting parts and an air tank in which working air for assembling the parts to the work is stored, and an air supply means being provided at least at one place on the transfer line for charging air in the air tank.
With the above arrangement, the pallet includes the part support for supporting the parts to be assembled to the work and hence, it is unnecessary to sequentially supply the parts from the outside to the pallet moving along the transfer line, leading to an enhanced operability. Moreover, the parts can be assembled to the work by the air stored in the air tank mounted on the pallet without sequential supplying of the air from the outside to the pallet moving along the transfer line, and hence, the handling of an air hose is simplified. In addition, the air can be supplied to the air tank, while the pallet is being circulated along the transfer line. Therefore, the supplying of the air to the air tank can be conducted easily.
To achieve the second object, according to a ninth aspect and feature of the present invention, in addition to the eighth feature, the work supported on work support jigs provided on the pallet is lifted and lowered by air cylinders connected to the air tank.
With the arrangement, the work supported on the work support jigs is lifted and lowered by the air cylinders and hence, the work can be supported in a position suitable for the operation, whereby the part assembling operation can be carried out efficiently. Moreover, the air cylinders can be driven by the air stored in the air tank mounted on the pallet without sequential supplying of the air from the outside to the pallet moved along the transfer line and hence, the handling of an air hose to the air cylinders is simplified.
With the above arrangement, the air tool is driven by the air stored in the air tank mounted on the pallet without sequential supplying of the air from the outside to the pallet moved along the transfer line. Therefore, the handling of the air hose to the air tool is simplified, and also the operability of the air tool is improved.
To achieve the second object, according to an eleventh aspect and feature of the present invention, in addition to the eighth feature, the work support jigs provided on the pallet are capable of being lifted and lowered to levels suitable for the operation.
With the above arrangement, since the work support jigs provided on the pallet are capable of being lifted and lowered to the level suitable for the operation, the work can be supported in a position suitable for the operation, whereby the part assembling operation can be carried out efficiently.
To achieve the first object, according to a twelfth aspect and feature of the present invention, in addition to the first feature, a working space, in which an operator can move, is provided inside the transfer line forming the closed loop, so that access of the operator to the pallet is enhanced by the working space.
With the above arrangement, it is possible for the operator to access any of the pallets through the working space at a low speed. The brake rollers 23, 23 apply a braking force to one of the plurality of pallets P moved by the main drive rollers 22, 22, which is located at the terminal end of the first conveyer C1, thereby preventing the pallet P from overrunning onto the first traverser T1. The transfer-out drive rollers 24, 24 are driven at a speed higher than that of the main drive rollers 22, 22, when one pallet P located at the terminal end of the first conveyer C1 is to be separated from the succeeding pallet P and moved to the start end of the first traverser T1. The transfer-in drive rollers 21, 21 are driven at a speed higher than that of the main drive rollers 22, 22, when one pallet P located at the terminal end of the second traverser T2 is to be moved to the start end of the first conveyer C1 to catch up with the final pallet P on the first conveyer C1.