APPARATUS FOR APPLYING FIXING SCREWS TO A METAL SHEET

Field of the invention

THIS INVENTION relates to apparatus for applying screws to a metal sheet and is particularly suited, although not exclusively so, to applying fixing screws to attach a roofing sheet having an undulating or corrugated or other form of surface profile surface to an underlying support structure.

State of the art

Corrugated iron roofs are common in Australia and are constructed from sheets of corrugated iron arranged with their edges overlapping one another and attached to an underlying metal or wooden framework by headed fixing screws. The points of attachment are signified by lines of pre-formed holes drilled through the sheets and framework and through which the fixing screws pass.

Care and skill are required to attach a corrugated iron roof in position. The corrugated iron sheets are usually inclined and often hot to the touch, and the screws have to be held so as to extend perpendicularly to the planes of the holes through which they are to be screwed. This involves a tradesman using two hands respectively to hold a screw in alignment with the axis of a hole through which it is to be passed, and simultaneously to screw it into the hole. At the same time the tradesman must take care not to accidentally slip down the inclined surface of the corrugated iron sheet and fall to the ground beneath. Unfortunately many tradesmen refuse to harness themselves in position because of the inconvenience involved, and this increases the risk of injuries to those working in the roofing industry.

Because of the problems outlined above, some tradesmen, will not worry unduly if some of the fixing screws have their longitudinal axes inclined to the planes of the holes through which they are being screwed, as the fault cannot be seen once the screw has been screwed down. Reliance is then placed on there being enough correctly positioned screws to hold the iron sheet in place without leaking, during its normal working life.

Object of the invention

An object of the invention is to provide a tool to assist a tradesman to apply headed, pointed fixing screws to an iron sheet to secure it to a supporting framework.

The invention Apparatus for applying a pointed, headed fixing screw to a metal sheet to secure it to a support, compris es i an open-ended, hollow body for placing over a position on the sheet at which a screw is to be located, the open end of the body being shaped to conform to the surface of the sheet surrounding said position when the longitudinal axis of a screw held in the body is substantially perpendicular to the plane of the sheet; a driving shaft extending through the body and being slidable and rotatable therein; a first end-portion of the shaft being adapted to be gripped in a chuck of a hand-held power tool; a second end- portion of the shaft being located inside the body and having means for enabling a fixing screw to be held by its head in axial alignment with the axis of rotation of the shaft so as to rotate therewith; and, a resilient member urging the shaft away from the body in the direction of its first end-portion.

Preferred features of the invention

The body is preferably made of a heat insulating material such as plastics and is conveniently formed with side windows so that a tradesman can see that the fixing screw is correctly held inside the body before the device is placed over the position on the sheet at which the screw is to be located.

The means for holding the fixing screw inside the body suitably comprises a bit which can be fitted to the second end-portion of the shaft and then held in place by grub screws

or some other mechanism so as to rotate therewith. A socket or spigot may be provided in the free end of the bit and of a non-circular cross-section, to enable a fixing screw having a head of complementary shape to be fitted into the bit and then held in place, for example, by magnetic attraction. If preferred, a sleeve may be used in place of the bit and held on the shaft by grub screws.

The resilient member may take the form of a coiled compression spring wound around the shaft between the body and a stop on the shaft positioned remotely from the body.

Introduction to the drawings

The invention will now be described in more detail, by way of examples, with reference to the accompanying drawings, in which:

In the drawings

FIGURE 1 shows one example of apparatus of the invention in an exploded perspective view; and,

FIGURE 2 shows the apparatus of figure 1 assembled and fitting against one corrugation of a corrugated iron sheet.

Description of preferred example

Figure 1 shows apparatus 1 in the form of a hollow, frusto-conical, hard plastics body 2 formed with three side windows 3. A steel driving shaft 4 having an enlarged tubular lower end 15 extends through the body 2 and has an upper or first end-portion terminating in a formation 5 designed to be gripped by a chuck (not shown) of a handheld power tool such as an electric drill. The enlarged tubular lower end of the shaft is provided with lateral threaded bores for grub screws (not shown). These grub screws are used to hold in the tubular end of a the shaft 4 a shank of a removable attachment in the form of a bit 11. The bit 11 is held in place on the shaft 4 by grub screws (nor shown) so that it rotates with the shaft 4. The lower end of the bit 11 extends beyond the lower end

of the shaft 4 and is formed with a hexagonal socket for the reception of a complementary head of a pointed fixing screw (not shown). The bit 11 is magnetized so that the screw is magnetically held in the socket in axial alignment with the axis of the shaft 4.

The plasties body 2 has a cylindrical opening 10 at its upper end which contains a cylindrical metal bushing 7 through which the shaft 4 extends. The shaft is thus rotatable and axially slidable in the bushing 7. A coiled, steel compression spring 9 encircles the upper end-portion of the shaft 4 where it protrudes from the body 3, and its lower end is held in place by fitting around an annular protrusion 10 projecting upwardly from the top end of the body 2 around the bushing 7. The upper end of the spring 9 is held in place by pressing against the underside of a cylindrical collar 16 held in place on the shaft by a grub screw (not shown) passing radially through the collar 16 and bearing on the shaft 4. The spring 9 is in compression so that it urges the shaft 4 in the direction of its upper end-portion.

The body 2 has a wavy circular under rim 12 which, as shown in figure 2, is formed with two, parallel and part-cylindrical rebates 13 shaped to be complementary to the convex curvature of a cusp 14 of a corrugation of a corrugated iron sheet 15. The under rim 12 can thus be fitted snugly against the top of the corrugation and, when in this position, the aligned axes of the driving shaft 4 and the fixing screw are perpendicular to the plane of the corrugated iron sheet. The side windows 3 enable a tradesman to see that this required alignment is correct and maintained.

Operation of preferred example

To use the apparatus 1 a tradesman fixes the upper end of the shaft 4 into a chuck of a hand-held power tool. After checking that the correct replaceable bit 11 is attached to the lower end of the shaft 4, the tradesman inserts the hexagonal head of a pointed fixing screw into the complementary socket of the bit 11 so that the screw and shaft axes are collinear. Finally a resiliently flexible and waterproof washer is pushed onto the screw.

The tradesman next selects the position at which the screw is to be used, and fits the under rim 13 of the body 2 to the cusp of the corrugation at this position so that the rim surround the position. The tool is then forced down to drive the pointed end of the screw through the iron sheet. Simultaneously the tradesman operates the tool to rotate the screw so that it screws itself tightly into the hole in the iron sheet made by its pointed end and the flexible and waterproof washer is compressed between the head of the screw and the iron sheet. The power tool is then lifted to release the screw head from the sleeve 11 and allow the tradesman to insert a new screw into the bit 11 so that the process can be repeated.

In some circumstances it may be required to change the body 2 for another one having a different profile of under rim 13. For example a flat profile may be required for attaching a flat sheet to an underlying framework. Alternatively the screw may be required to be driven into a metal sheet having a different profile of corrugation or undulation or at a position on a corrugated sheet corresponding to a valley in the corrugations.

The replacement of the body 2 by another having the required profile of under rim is achieved by removing the collar 16. This allows the body 2 and attached compression spring 9 to be slid off the upper end of the shaft 4 and replaced with another body 2 having the desired profile. The spring 9 and collar 16 can then be restored to their former positions.