GB2234695A

GB2234695A - Screwdriver accessory

Info

Publication number: GB2234695A
Application number: GB8922401A
Authority: GB
Inventors: Stanley George Andrew Pelling
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-08-01
Filing date: 1989-10-04
Publication date: 1991-02-13
Anticipated expiration: 2009-10-04
Also published as: GB2234695B; GB8917565D0; GB8922401D0

Abstract

A sleeve 11 surrounds the blade of a screwdriver and is a sliding fit upon it. In use, it extends beyond the blade tip of the screwdriver to envelop the screw head being operated upon in order to retain the screwdriver blade aligned with the head of the screw without slipping off. The sleeve is provided with a longitudinal slot 20 so that widening of the slot can accommodate screwdriver blades of a range of cross-sections. The sleeve has an upper cylindrical bore 13 of wide diameter divided by a shoulder 12 from a narrower bore 14 which may be provided with diametrically opposed recesses, for example up to the internal diameter of the wider portion 13 to accommodate screwdriver blades which extend beyond the maximum dimension of their main stem. The internal surfaces of the sleeve may be ribbed, particularly in the narrower section, to increase friction. <IMAGE>

Description

SCREWDRIVER ASSEMBLY This invention relates to screwdrivers and in particular to an accessory which assists the retention of the screwdriver blade on the head of the screw to be turned.

Particularly with power driven screwdrivers, there is a problem that a screwdriver tends to veer off the head of the screw being turned when torque is applied, which may damage the surrounding workpiece and also disconnects the drive between the screwdriver and the screw.

There has been proposed a sleeve for fitting on the screwdriver stem which sleeve is axially slidable on the screwdriver stem to encompass the screw head while it is proud of the workpiece. This simple sleeve is subject to several disadvantages. It has to be a tight fit on the screwdriver to stop it falling off the er,d of the screwdriver or sliding up the stem so that the screwdriver blade is exposed and 30 there is little tolerance in the manufacture of a sleeve for screwdrivers and many different sleeves have to be provided for screwdrivers of different sizes. According to the present invention there is provided a screwdriver assembly as set out in Claim 1. The inherent resilience of the sleeve material keeps the sleeve gripping the screwdriver blade so that it does not slip from the desired position on the blade.

Lother problem which is encountered is that screwdriver blades may exceed the maximum cross-section of the main stem adjacent to the tip of the blade, which Irieans that it is difficult to fit a cylindrical sleeve onto it. According to a preferred feature of the invention there is provided a sleeve as described above provided with diametrically opposed recesses extending outwardly from the interior walls of the bore to accommodate such wider portions of the blade.

The friction between the sleeve and the screwdriver can be increased if the internal surface of the bore of the sleeve is roughened, for example by ribbing.

Examples of the invention will now be described with reference to the accompanying drawings in which: Figures 1 to 4 are respectively a top perspective view, front elevation, plan, and section on Line A-A of a sleeve for use with a screwdriver having a hexagonal stem; and Figures 5 and 6 are respectively a side elevation and plan of the associated screwdriver stem, Figures 7 to 12 of the corresponding views for a second embodiment of the invention in which the screwdriver stem is cylindrical, and Figure 13 is an enlarged view of ribbing on the internal surface of the sleeve.

As can be seen in Figure 1, the sleeve 11 has a plain cylindrical exterior but an interior which is divided by a bevelled shoulder 12 into an upper cylindrical portion 13 of wide diameter and a lower bore 14 of hexagonal section for fitting closely around the hexagonal stem of the screwdriver. A slot 20 is cut in the sleeve parallel to its axis through its wall to allow the sleeve to open out slightly to receive a slightly over-sized screwdriver within its bore. The natural resilience of the sleeve material keeps the slot sleeve gripping the screwdriver. The slot 20 is located at the mid-point of one face of the hexagonal section 14 and equidistant between the diametrically opposed recesses 19 to be described below.

In operation, the sleeve of Figure 1 is slid over the end of the screwdriver stem to an initial position extending beyond the blade 22 of the screwdriver. The narrow bore 14 is a close fit on the stem 21 so that the sleeve is prevented from falling off by friction. The internal surface of the bore is ribbed, with ribs 31 extending parallel to the axis of the sleeve to improve friction.

The screwdriver and the sleeve 11 are placed in position on the head of the screw with the blade 22 engaging the slot of the screw head and the shoulder 12 resting on the periphery of the screw head. Torque is applied to the screwdriver and is transmitted to the screw by the engagement of the screwdriver blade 22 with the slot in the screw head; the screwdriver cannot slip off the head because of the engagement of the upper wide-diameter bore 13 of the sleeve with the periphery of the screw head.As the screw is driven home, the upper end 15 of the sleeve will engage the workpiece and the sleeve will be slid back on the screwdriver stem for the remainder of the operation but the engagement of the sleeve with the screw head will continue until towards the end of the operation depending on the shape of the screwdriver, thus preventing the screwdriver from slipping off the head of the screw.

At the end of the operation, the sleeve will be retracted fully on to the stem.

As will be seen from Figures 5 and 6, the screwdriver tapers from the maximum cross-section of the stem uniformly to the rectangular section of the tip 23 of the blade in the direction transversely to the elongate direction of the blade, but in the direction parallel to the elongate direction of the blade, the blade first extends to a larger dimension 24 than the maximum cross-section of the main stem before tapering uniformly to the cross-section of the tip 23.

This greater section is accommodated in the diametrically opposite slots 19 extending radially from the apices of the hexagonal cross-section of the lower bore of the sleeve, ending at the inner diameter of the upper cylindrical portion 13.

In the embodiment of Figures 1 to 6, the engagement of the hexagonal bore 14 of the sleeve with the hexagonal stem 21 of the screwdriver will cause the sleeve to be rotated with ( the screwdriver; in the embodiment of Figures 7 to 12, the lower bore 114 of the sleeve and the stem 121 of the screwdriver are cylindrical and so there is no rotational drive between the screwdriver and the sleeve. Components of Figures 7 to 12 have reference numbers increased by 100 in relation to the corresponding components of Figures 1 to 6.

Although the screwdriver has been shown with a simple conventional blade, it would of course be possible to provide a Philips-type (or other type) head for the screwdriver for either embodiment of the invention. The invention is applicable to screw heads of various shapes, including a flat countersunk head, round head and mushroom-shaped. The invention is applied to screwdrivers of various types, including conventional manual screwdrivers, electrically driven screwdrivers and pump action screwdrivers.

Claims

CLAPfi :

1. A screwdriver assembly comprising a stem, a screwdriver blade on one end of the stem and a sleeve having a wide bore portion and a narrow bore portion which is in frictional contact with the stem, the sleeve being axially slidable on the stem from a position in which its wide portion extends beyond the blade, the sleeve being split to accommodate a range of stem and blade dimensions.

2. An assembly as claimed in Claim 1 wherein the narrow bore portion is formed with opposed recesses to accommodate any extent of the blade beyond the corresponding extent of the stem.

3. An assembly as claimed in Claim 1 or Claim 2 wherein the internal surface of the narrow bore portion is rougilened.

4. An assembly as claimed in Claim 3 wherein the internal surfaces of the narrow bore portion is formed with longitudinal ribs.

5. An assembly as claimed in any one of Claims 1 to 4 wherein the stem is of non-circular section and the narrow bore portion of the sleeve is of corresponding non-circular section.

6. A screwdriver assembly substantially as hereinbefore desribed with reference to the accompanying drawings.