Tools – Wrench – screwdriver – or driver therefor – Machine
Patent
1997-10-08
1999-01-26
Smith, James G.
Tools
Wrench, screwdriver, or driver therefor
Machine
81 5737, 173159, B25B 2306
Patent
active
058627243
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to screw driving method and apparatus wherein the tip of a driver bit is fitted into the groove of the head of a screw, the fitted screw is disengaged from a screw carrier strip by a forward stroke force of the driver bit, the tip of the screw is driven to a predetermined depth in a workpiece, and the screw is screwed by rotating the driver bit.
BACKGROUND ART
An apparatus for fitting the tip of a driver bit into the groove on the head of a screw, disengaging the fitted screw from a screw carrier strip by a forward stroke force of the driver bit and driving the screw into a workpiece while rotating the driving bit is publicly known as Japanese Patent Laid-Open No. 7-171770 (JP-A-7-171770). In this screw driving apparatus, in order to solve the problem such a reaction that the driving apparatus is raised when the screw pressed against the workpiece is driven, a moving piston for advancing a driver bit is connected through a spring to the driver bit. The piston can move forward in the way that it compresses the spring even when the driver bit abuts against the workpiece to resist further advance, thereby it preventing the reaction in the direction that the apparatus tends to be raised.
Nevertheless, the above screw driving apparatus described in Japanese Patent Laid-Open No. 7-171770 (JP-A-7-171770) causes additional reaction if a strong spring to meet a strong pressing force is used for high-speed pressing and high-speed driving of screws because a greater pressing force is required for screwing them in after they abut against the workpiece. On the contrary, the use of a weak spring decreases the speed of pressing screws to slow the driving operation. It is also feared that failure in disengaging screws from a screw carrier strip or in fitting of the tip of the driver bit into the groove on the screw head may arise to hinder the driving operation.
DISCLOSURE OF INVENTION
Accordingly, the present invention aims to provide a screw driving method which is capable of driving screws reliably with less reaction and at a high speed.
Another object of the invention is to provide a screw driving apparatus which is capable of driving screws reliably with less reaction and at a high speed.
The inventor of the present invention analyzes by experiments that in the screw driving apparatus, a strong pressing force of 7 Kg to 10 Kg is required during the period between disengaging a screw from the screw carrier strip and driving the tip of the screw to a predetermined depth in a workpiece, and then a weak pressing force of about 2 Kg or 3 Kg is sufficient when the screw being rotated is screwed into the workpiece. This is because after the screw has been driven into the workpiece to a certain extent, further applying a pressing force of the same strength causes the screw to be driven in like a nail, not to be properly screwed in, so that a sufficient pulling resistance as required of the screw is not obtained.
The present invention provides a screw driving method comprising steps of fitting the tip of a driver bit into the groove on a screw head, disengaging the fitted screw from a screw carrier strip under a forward stroke force of the driver bit, driving the tip of the screw to a predetermined depth in a workpiece, and screwing the screw in while rotating the driver bit. The method is characterized in that the screw driving method comprises: steps of advancing the driver bit with a strong pressing force by a primary piston during a period between the step of fitting the tip of the driver bit into the groove on the screw head and the step of driving the tip of the screw to the predetermined depth in the workpiece; and when the screw is screwed into the workpiece after the driving of the screw into the workpiece, advancing the driver bit with a weak pressing force by a secondary piston which passes through the primary piston.
The present invention also provides a screw driving apparatus which has a cylinder, piston means reciprocating in the cylinder by means of compress
REFERENCES:
patent: 2383380 (1945-08-01), Gimpel
patent: 5231902 (1993-08-01), Uno et al.
Arata Ken
Fujii Satoshi
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