Magnetically attractive driver bit assembly

Details Magnetically attractive driver bit assembly Magnetically attractive driver bit assembly

2000-02-01

2001-04-03

Eley, Timothy V. (Department: 3723)

Tools

Wrench, screwdriver, or driver therefor

Having work engaging and force exerting portion inserted...

C081S452000

Reexamination Certificate

active

06209426

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a magnetically attractive driver bit assembly.
BACKGROUND OF THE INVENTION
Conventionally, when driving a screw, devices such as one disclosed in the Japanese Utility Model Publication No. Sho 46-35987, wherein air attraction is employed to attract a screw to the tip of a driver bit, have been utilized. Also, for example, the Publication of Unexamined Japanese Utility Model Application No. Sho 57-202669 discloses a device, wherein magnetic force is employed to attract a screw to the tip of a driver bit by magnetizing the driver bit using one or more permanent magnets.
In the case where air attraction is employed, however, it is necessary to fit a device adapted for air attraction around a driver bit. Therefore, when driving a screw into an object having a counterbore, the driver bit with such a device cannot be used because the outside diameter thereof is relatively large. Moreover, since the weight of the end portion of a screwing robot is increased, it is impossible to convey a screw attracted to the driver bit from a screw supply position to a screwing position at high speed.
Prior art for magnetizing a driver bit itself has the disadvantage that the magnetic attraction of the driver bit for a screw is not strong enough to securely hold the screw. As a result, high-speed movement of a screwing robot arm from a screw supply position to a screwing position may cause the screw to drop off the driver bit and, therefore, speed-up of the screwing operation is prevented.
SUMMARY OF THE INVENTION
Wherefore, a principal object of the invention is to provide a novel driver bit assembly which comprises a driver bit and a magnetically attractive device and shows a strong magnetic attraction when applied to a screwing robot and the like so that the operating speed of the robot arm can be increased. Another object of the invention is to provide a driver bit assembly which can prevent breakage of the magnetically attractive device even when the driver bit is broken.
To attain these and other objects, there is provided a magnetically attractive driver bit assembly capable of magnetically attracting a screw, the driver bit assembly comprising: a driver bit made of a magnetic body having a tip for engaging with the screw and a peripheral portion extending from the tip to a position at a predetermined distance; a cylindrical spacer made of a magnetic body fitted around the peripheral portion of the driver bit; a fixing means for fixing the cylindrical spacer around the driver bit; and a ring magnet fixed to an end of the cylindrical spacer by means of its magnetic attraction and adapted for magnetically attracting the screw.
The fixing means is preferably another ring magnet, which is disposed between the cylindrical spacer and a step located between the above peripheral portion and a large diameter portion, and magnetically attracts both the step and the cylindrical spacer.
Alternatively, the fixing means may be an O-ring fitted on the inner surface of the cylindrical spacer, which has an annular in cross-section larger than the clearance between the inner surface of the cylindrical spacer and the outer surface of the peripheral portion of the driver bit, and which is elastically deformed to fix the cylindrical spacer on the driver bit.
Preferably, the length of the cylindrical spacer is such that, when a screw is magnetically attracted to the tip of the driver bit, the head of the screw and the ring magnet do not contact each other with a narrow gap therebetween.
In the case where an O-ring is employed as a fixing means, the length of the cylindrical spacer is such that even when the cylindrical spacer is positioned away from the step of the driver bit, the above described gap occurs between the head of the screw and the ring magnet.


REFERENCES:
patent: 3707894 (1973-01-01), Stillwagon, Jr.
patent: 4219062 (1980-08-01), Berkman
patent: 5724873 (1998-03-01), Hillinger
patent: 5861789 (1999-01-01), Bundy et al.
patent: 46-35987 (1971-12-01), None
patent: 57-202669 (1982-12-01), None

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