Conveyors: power-driven – Conveyor section – Load propelled as the reactive means in a linear motor or...
Reexamination Certificate
1999-09-07
2001-09-18
Noland, Kenneth W. (Department: 3651)
Conveyors: power-driven
Conveyor section
Load propelled as the reactive means in a linear motor or...
C198S690100
Reexamination Certificate
active
06290056
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a conveying apparatus and, in particular, to a conveying apparatus suitable for conveying magnetic workpieces such as lead frames.
2. Description of the Related Art
As a conventional example of a lead frame conveying apparatus, a guiding apparatus has been proposed in Japanese Utility Model Publication No. 7-35388, in which a lead frame is guided along the upper surface of a non-magnetic guide rail and in which a non-magnetic guide member is provided at one side edge of the upper surface of the guide rail. The apparatus also has magnets embedded in the guide member at appropriate intervals. In this apparatus, the side edge of the lead frame is attracted by the magnetic force and kept in contact with the guide member, so that a high level of positional accuracy can be achieved. Further, there is no need to provide a device for preventing the lead frame from going backward or a device for imparting tension.
In the above-described apparatus, however, it is necessary to employ transfer means such as a transfer lug for transferring the lead frame, and it is difficult to perform high-speed conveying with low vibration and low noise. Further, since the lead frame is in close contact with the guide member, there is frictional resistance between the lead frame and the guide member. When the transfer lug is engaged with the lead frame to transfer the lead frame, a large load is partially applied to the lead frame, and there is a danger of the lead frame being expanded or deformed.
To solve the above problem, U.S. Pat. No. 5,816,385 proposes a conveying apparatus capable of conveying a magnetic workpiece at high speed with low vibration and low noise and allowing high-accuracy positioning to be effected. This conveying apparatus serves to convey a magnetic workpiece having two adjacent surfaces. The apparatus comprises a non-magnetic rail having a guide surface for slidably guiding a first surface of the workpiece. The conveying apparatus also comprises a non-magnetic belt having a conveying surface in contact with a second surface of the workpiece and movable along the rail and driving means for running the belt. The conveying apparatus further comprises a magnet which is arranged at a position opposed to the rail through the intermediation of the belt and which generates a magnetic force including a component force for bringing the second surface of the workpiece into close contact with the belt and a component force for bringing the first surface of the workpiece into contact with the rail.
In the above conveying apparatus, the magnetic workpiece is conveyed in a state in which it is attracted to a magnet (yoke) through the intermediation of the non-magnetic belt. When conveying a workpiece requiring a large magnetic force, the friction between the non-magnetic belt and the magnet (yoke) increases. This friction leads to wear of the non-magnetic belt and the magnet (yoke) which results in a deterioration in durability and a degeneration in conveying position accuracy of the apparatus. Furthermore, a large driving force is required to drive the belt.
The wear on the non-magnetic belt and the magnet (yoke) may be avoided to some extent by performing low-friction surface treatment on the sliding surface of the non-magnetic belt or the yoke, or applying oil for lubrication. These solutions, however, are not permanent measures to solve the problem.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a conveying apparatus capable of conveying magnetic workpieces at high speed with low vibration and low noise, superior in durability, and contributing to a reduction in driving force.
To achieve the above-described object, according to a first aspect of the present invention, there is provided an apparatus for conveying a magnetic workpiece having two adjacent surfaces, comprising a non-magnetic rail having a guide surface slidably guiding a first surface of the workpiece, a non-magnetic conveying member having a conveying surface in contact with a second surface of the workpiece and movable along the rail, driving means for running the non-magnetic conveying member, a rotatable roller whose peripheral surface is in rolling contact with a surface opposed to the conveying surface of the magnetic conveying member, and a magnet incorporated in the roller and adapted to generate a magnetic force having a component force for causing the second surface of the workpiece to be attracted to the roller through the intermediation of the non-magnetic conveying member and a component force for bringing the first surface of the workpiece into contact with the rail.
The second surface of the workpiece is attracted to the conveying surface of the workpiece by the magnet, so that, when the non-magnetic conveying member is moved along the rail by the driving means, the workpiece moves integrally with the non-magnetic conveying member. At this time, the first surface of the workpiece is slidably guided by the guide surface of the rail, so that the workpiece is conveyed while maintaining a stable attitude. The back surface of the non-magnetic conveying member, that is, the surface opposed to the conveying surface, is supported by the roller so that it can roll, so that the conveying member does not slide on the magnet (yoke). Since the conveying member does not slide on the magnet (yoke), wear of the conveying member and the magnet can be prevented. Further, since there is substantially no friction between the conveying member and the roller, it is possible to reduce the driving force for driving the belt. During conveying, the workpiece moves in contact with the non-magnetic member, so that concentration of load on a part of the workpiece does not occur. Thus, it is possible to convey the workpiece at high speed without applying excessive load to it, whereby deformation and deflection of the workpiece can be prevented.
When the non-magnetic conveying member is stopped abruptly, there is a danger of the workpiece undergoing positional deviation due to inertial force. In the present invention, however, the second surface of the workpiece is in close contact with the non-magnetic conveying member due to the magnetic force, so that, if the conveying member is stopped abruptly, the workpiece can be stopped without resulting in any positional deviation. Further, since there is no need to provide a device for preventing the workpiece from going backward or a device for imparting tension, the size of the apparatus can be reduced.
When the non-magnetic conveying member of the present invention is run no return operation is required. Since no return operation is required high-speed conveying is possible, and no violent vibration or noise is involved if the speed is increased.
According to another aspect of the present invention, there is provided a conveying apparatus for conveying a magnetic workpiece having two adjacent surfaces, comprising, a non-magnetic rail having a guide surface for slidably guiding a first surface of the workpiece, a plurality of rollers having peripheral surfaces in rolling contact with a second surface of the workpiece, driving means for causing the rollers to rotate in synchronism in the same direction, and magnets incorporated in the rollers and adapted to generate a magnetic force having a component force for causing the second surface of the workpiece to be attracted to the rollers and a component force for bringing the first surface of the workpiece into contact with the rail.
In the apparatus described above, the magnetic workpiece is directly attracted by the rollers, and the workpiece is conveyed in one direction by rotating the rollers. In this case also, as in the case of the first aspect of the present invention, the workpiece can be conveyed at high speed with low vibration and low noise. Further, positioning can be effected with high accuracy. In addition, the workpiece and the rollers are only in rolling contact with each other, and there is no sliding movem
Kajiwara Masatoshi
Okawa Teruo
Ootsuki Katsumi
Burns Doane , Swecker, Mathis LLP
Murata Manfacturing Co., Ltd.
Noland Kenneth W.
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