GB2548142A

GB2548142A - Screwdriver

Info

Publication number: GB2548142A
Application number: GB1604128.7A
Authority: GB
Inventors: Francis Govier John
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-03-10
Filing date: 2016-03-10
Publication date: 2017-09-13
Also published as: GB201703902D0; GB201604128D0; GB2548247A

Abstract

The screwdriver has a manually gripable stock or handle (2) having mounted thereto an elongate screwdriver shaft (3) having a screw-engaging tip (4); a slidable axial sleeve (6) fitted coaxially around the elongate shaft, the sleeve having a distal end shaped for engagement with a screw head and a proximal end to fit in the stock (2), the proximal end having an enlarged flange (8a); a blind socket or recess (9) in the stock for receiving the shaft and the proximal end of the sleeve, the blind socket having a constriction at the open end of the blind socket for engaging the enlarged flange: and a spring (11) in the blind socket to engage the proximal end of the sleeve and to bias the sleeve away from the stock.

Description

Screwdriver

The present invention concerns a screwdriver, which may be of the traditional manual type, or may be a motor-powered type. In particular, the invention concerns a screwdriver adapted to inhibit unwanted movement of its tip relative to the head of a driven screw.

Although screwdrivers (both manual and motor-powered) for driving a wood screws or the like have been known for many years, and they are probably the most ubiquitous of hand tools, they nevertheless have some disadvantages. Specifically, unwanted movement of the tip of a screwdriver relative to the head of a screw to be driven remains a significant problem. Such unwanted movement (which is generally lateral movement in the case of slotheaded screws) can result in the tip of the screwdriver slipping out of the head of the wood screw. Such slipping is especially problematical when the head of the screw is not readily accessible, or when the workpiece into which the screw is being inserted is subject to vibration. Such unwanted movement can cause damage to the head of the screw, to the workpiece into which the screw is being screwed, and/or to fingers of the operative.

Proposals have been made to provide tubular sleeves for the shafts of screwdrivers with ends of the tubular sleeves intended to engage with the outer edge of the screw head, in order to inhibit such unwanted movement. Examples of such disclosures are given in, for example, US patents 4800788 and 5029498, and GB2251196A1. Such sleeves are all intended to be retrofit to existing manual screwdrivers, which has the disadvantage that they must be sufficiently flexible to slide over the widest part of the screwdriver shaft (shank) -namely the tip, but then fit sufficiently snugly that they do not slide back over the tip when the screwdriver is in use.

According to the invention, there is provided a screwdriver comprising (a) a manually grippable stock having mounted thereto an elongate screwdriver shaft having a screw-engaging tip; (b) a slidable axial sleeve fitted coaxially around the elongate shaft, the sleeve having a distal end shaped for engagement with a screw head and a proximal end to fit in the stock, the proximal end having an enlarged flange; (c) a blind socket in the stock for receiving the shaft and the proximal end of the sleeve, the blind socket having a constriction at the open end of the blind socket for engaging the enlarged flange; and (d) resilient biasing means provided in the blind socket for engaging the proximal end of the sleeve to bias the sleeve away from the stock.

The screwdriver according ίο the invention therefore includes a freely slidable sleeve with a distal end to engage with a screw head (such engagement being preferably by encircling the periphery of the screw head). The sleeve is biased by the resilient biasing means towards the screw so that the distal end of the sleeve snugly fits to the screw head and thereby prevents unwanted lateral movement of the screw when the latter is driven by the screwdriver. Typically the head of the screw may fit into the distal end of the sleeve to a depth of up to about 3 millimetres.

The sleeve is therefore resiiientiy biased to fit around the screw head; user pressure on the screwdriver can cause the sleeve to retract slightly, typically to a depth of about 8 millimetres. This is therefore advantageous when the screwdriver is used to drive countersunk screws.

The resiiientiy biased sleeve advantageously helps to grip the screw and to prevent lateral movement of the screwdriver tip relative to the screw thread, thereby preventing damage to the screw or workpiece, or personal injury to the user.

The sleeve may, in one embodiment, comprise a tube of plastics material, typically of an engineering plastics material such as polypropylene, high density polyethylene, polyamide (nylon) or the like, in this embodiment, it is particularly preferred that such a tube be in the form of a unitary integral extrusion. Such a tube is preferably such that it has flexibility in a transverse direction (so that it can grip around the head of the screw when in use) but not in a longitudinal direction (so that it can be biased by the biasing means substantially without compression).

In an alternative embodiment, the sleeve may comprise a tube of engineering metal, such as aluminium. Such a metal tube should again be substantially rigid in a longitudinal direction.

The sleeve in the screwdriver according to the invention is generally axially symmetrical, and furthermore generally substantially cylindrical (apart from the enlarged flange) so that the sleeve has a circular opening at the distal end to engage with the screw head. The enlarged flange is shaped to engage with an internal lip in the blind socket, such that the sleeve is maintained in place (that is, not fully pushed out of the blind socket) when the sleeve is biased by the resilient biasing means.

The sleeve should be of sufficient length to be able to surround the entire exposed length of the screwdriver shaft when biased outwardly to the full extent by the biasing means, leaving the proximal end and the enlarged flange in the blind socket. When the sleeve is pressed from the distal end, the proximal end may retract into the blind socket against the action of the resilient biasing means.

The resilient biasing means typically comprise a helical spring arranged for engagement with the enlarged flange at the proximal end of the sleeve to bias the sleeve away from the stock. Other suitable resilient biasing means include shaped elastomeric bodies or other forms of spring.

When the resilient biasing means is a helical spring, it preferably fits around the elongate screwdriver shaft {or shank) with one end of the helical spring engaging the closed end of the blind socket and the other end engaging the proximal end of the sleeve (such as the enlarged flange thereof).

The constriction at the open end of the blind socket is preferably annular, and shaped and dimensioned to engage with a corresponding annular enlarged flange of the sleeve. Such an annular constriction typically coaxially surrounds the elongate screwdriver shaft.

The elongate screwdriver shaft is preferably of conventional tool metal construction (for example of tool grade steel). The tip is shaped to engage with a corresponding shape in the screw head. For example, when the screw is of the slot-head type, the screwdriver has a straight tip. Alternatively, when the screw is of the cross-head (or Philips) type, then the screwdriver has a complementary shaped cross-head tip.

Generally the screwdriver shaft has a portion thereof extending from the tip that is of circular cross-section; the proximal end (that is the end mounted to the stock) typically has flat sides or conventional projections for secure anti-rotation engagement with the stock.

The stock may be of conventional form for a manual screwdriver, such as a moulded body of suitable high impact plastics or elastomeric material, moulded around the proximal end of the screwdriver shaft (and with the blind socket moulded as an integral part of the stock).

Alternatively, the screwdriver shati may be removable from and replaceable to the stock, in which case the stock is preferably provided with a motor for driving the screwdriver shaft, so as to provide a power-driven screwdriver. Such a power-driven screwdriver preferably has a chuck to enable different screwdriver shafts to be inserted or replaced; the stock is generally provided with a trigger so that the user can selectively cause the motor to either drive the screw in or out. A power-driven screwdriver of this nature may have impact-driver bits. A preferred embodiment of the invention will now be described with reference to the accompanying drawing of which the single figure is a schematic view of an exemplary screwdriver according to the invention.

Specifically, the drawing shows a manual screwdriver 1 having a manually ghppable stock 2 which receives an elongate screwdriver shaft 3 having a a screw-engaging tip 4, and within the stock, protrusions 5a, 5b for keying to the material of the stock 2. A slidable axial flexible sleeve 6 fits coaxially around the shaft 3. The sleeve 6 has a circular open end 7 for engagement with a screw head (not shown) and an opposed end 8 having an enlarged flange 8a. The sleeve is as shown substantially cylindrical apart from the enlarged flange 8a.

End 8 is received in a blind socket 9 in the stock, the blind socket having a constriction 10 at the open end thereof for engaging the enlarged flange 8a. A helical spring 11 (which coaxially surrounds shaft 3) is provided in the blind socket for engaging the end of the sleeve 6 to bias the sleeve away from the stock. The sleeve therefore covers the entire exposed length of the shaft 3 under the biasing action of the spring; when pressure is put on the end 7 of the sleeve 3, the sleeve will partially retract into the socket 9 against the action of the spring 11. A screwdriver according to the invention (such as the embodiment just described) may be used with any conventional screws, such as wood screws, or screws for fitting to metal or to other materials (such as masonry). The screws may be countersunk, flat head, domed, or any other conventional type of screw.

Claims

1. A screwdriver comprising (a) a manually grippable stock having mounted thereto an elongate screwdriver shaft a screw-engaging tip; (b) a siidabie axiai sleeve fitted coaxially around the elongate shaft, the sleeve having a distal end shaped for engagement with a screw head and a proximal end to fit in the stock, the proximal end having an enlarged flange; (c) a blind socket in the stock for receiving the shaft and the proximal end of the sleeve, the blind socket having a constriction at the open end of the blind socket for engaging the enlarged flange; and (d) resilient biasing means provided in the blind socket for engaging the proximal end of the sleeve to bias the sleeve away from the stock.

2. A screwdriver according to claim 1, wherein the sleeve comprises a tube of plastics material.

3. A screwdriver according to claim 2, wherein the tube comprises a unitary integral extrusion.

4. A screwdriver according to claim 1, wherein the sleeve comprises a tube of engineering metal.

5. A screwdriver according to any of claims 1 to 4, wherein the tube sleeve is axially symmetrical, and substantially cylindrical.

6. A screwdriver according to any of claims 1 to 5, vi/herein the resilient biasing means comprise a helical spring arranged for engagement with the enlarged flange at the proximal end of the sleeve to bias the sleeve away from the stock.

7. A screwdriver according to claim 6, wherein the helical spring fits around the elongate screwdriver shaft with one end of the helical spring engaging the closed end of the blind socket and the other end engaging the proximal end of the sleeve.

8. A screwdriver according to any of claims 1 to 7, wherein the constriction at the open end of the blind socket is annular, and shaped and dimensioned to engage with a corresponding annular enlarged flange of the sleeve.

9. A screwdriver according to claim 8, wherein the annular constriction coaxially surrounds the elongate screwdriver shaft.