Screwdriver bit for phillips-head fasteners

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(11)

EP 0 551 930 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	18.08.1993 Bulletin 1993/33

(43)	Date of publication A2:
	21.07.1993 Bulletin 1993/29

(21)	Application number: 93104130.5

(22)	Date of filing: 03.11.1989

(51)	International Patent Classification (IPC)⁵: B25B 15/00

(84)	Designated Contracting States:
	AT BE CH DE ES FR GB GR IT LI LU NL SE

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Priority:

14.11.1988 US 270000

(62)	Application number of the earlier application in accordance with Art. 76 EPC:
	89311411.6 / 0369655

(71)	Applicant: Black & Decker Inc.
	Newark Delaware 19711 (US)

(72)	Inventor:
	Chaconas, Peter Constantine Glyndon, Maryland 21071 (US)

(74)	Representative: Stagg, Diana Christine et al
	Emhart Patents Department Emhart International Ltd. 177 Walsall Road Birmingham B42 1BP Birmingham B42 1BP (GB)

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References cited: :

(54)	Screwdriver bit for phillips-head fasteners

(57) A modified Phillips-type screwdriver bit is disclosed that is fully compatible with a standard Phillips-head fastener, and is designed to significantly increase the level of torque that can be applied to the fastener while at the same time substantially reducing the cam-out forces normally produced by a standard Phillips screwdriver-bit. These results are accomplished by the use of a driver having a cross-shaped recess formed in the head thereof, and having associated therewith an axis and including a bit portion symmetrical about any plane containing the axis of the driver and adapted for insertion into said recess which comprises radially symmetrical wing means having generated side surfaces and defining roots therebetween for rotationally driving said fastener on said side surfaces in the same manner in both rotational directions. Preferably said wing means comprise four equally radially spaced bit wings defined by generated side surfaces that in turn define an included angle between adjoining bit wings that progressively increases from a first predetermined angle at the base of said bit wings to a second greater predetermined angle at an axially spaced distance therefrom. The radially outwardly facing surfaces of said bit wings may be tapered toward a common point at an angle relative to the axis of said bit portion substantially equal to the Phillips-standard wing angle. The roots of said bit portion are preferably oriented relative to said bit axis at an angle substantially equal to the Phillips-standard root angle.

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