This invention relates to a tool and, more particu¬ larly, to a tool which is provided with one or more locking members.

Many tools in use today are designed to be fitted with sheets of consumable material. Amongst such tools are power sanders and drum sanders which are adapted to be fitted with sheets of abrasive material.

One of the difficulties in using these tools is securing the sheets of abrasive material to the tool in a reliable and effective manner.

US-A-3 818 651 discloses a drum sander having an annular rim the circumference of which is covered with a sheet of abrasive material. The ends of the sheet mater¬ ial extend into a radially outwardly tapered slot in which a C-shape sleeve is rotatably mounted. The C-shape sleeve subtends an angle of about 320°. In use, the free ends of the sheet are inserted into the C-shape sleeve which is then rotated to trap the sheet between the outer perimeter of the C-shaped sleeve and the wall of the outwardly tapered slot. It will be noted that the maximum gripping force is determined by the inherent resilience in the C-shaped sleeve.

UK-A-1 529 005 discloses a polishing wheel the outer surface of which is divided into six segments each covered by an abrasive strip. Each abrasive strip ex¬ tends over its allotted segment and each end of the abrasive strip is turned inwardly and held in position by rotation of a respective pivotally mounted shaft having an eccentric cam mounted thereon. This arrange¬ ment is relatively heavy, complex and expensive. In addition, as the bearing supporting the shaft wears the shaft becomes unable to restrain the strip remote from the bearing in a satisfactory manner.

According to the present invention, there is

provided a tool having an elongate recess for accommoda¬ ting a locking member, a locking member in said elongate recess and a slot through which an item to be secured can be inserted into said elongate recess, characterized in that said locking member comprises an inelastic bar which can be turned from an inoperative position in which said item can be inserted into said elongate recess via said slot and an operative position in which at least a major portion of the length of said inelastic bar acts between one side of said elongate recess and said item to trap said item against an oppo¬ site side of said elongate recess.

Preferably, said elongate recess is of substantial¬ ly circular cross-section.

Advantageously, part of said locking member is of substantially circular cross-section and part is flat.

Preferably, part of said locking member between said part of substantially circular cross-section and said flat is rounded.

Advantageously, the length of said locking member is substantially equal to the length of said elongate recess.

Preferably, at least one end of said locking member is provided with a socket.

Advantageously, said items is a sheet of abrasive material and said tool is a sander.

Preferably, said sander is provided with a layer of resilient material to support said abrasive material.

Advantageously, said sander is a drum sander.

The present invention also provides a tool in accordance with the invention with a sheet of abrasive material attached thereto.

In another application, the tool comprises a rotor of a rotary planer and said item is a blade therefor.

For a better understanding of the present invention and to show how the same may be carried into effect reference will now be made, by way of example, to the accompanying drawings, in which: -

Figure 1 is a side view of one embodiment of a tool in accordance with the present invention with a sheet of abrasive material mounted thereon;

Figure 2 is an end view looking in the direction of line II-II on Figure 1;

Figure 3 is a fragmenting view showing, on an en¬ larged scale, a detail of the tool shown in Figure 2;

Figure 4 is a perspective view of a locking member;

Figure 5 is a view similar to Figure 3 showing the sheet of abrasive material being mounted on the tool;

Figure 6 is a perspective view of a second embodi¬ ment of a tool in accordance with the present invention with a sheet of abrasive material mounted thereon;

Figure 7 is a perspective view of a third embodiment of a tool in accordance with the present invention with two sheets of abrasive material mounted thereon; and

Figure 8 is a perspective view of a fourth embodi¬ ment of a tool in accordance with the present invention with a sheet of abrasive material mounted thereon.

Referring to Figures 1 to 5 of the drawings, there is shown a drum sander which is generally identified by the reference numeral 1. The drum sander 1 comprises a drum 2 which is made of rigid plastics material (PVC) and is mounted on an arbor 3. A layer 4 of resilient plastics material (foam) is permanently glued to the outside of the drum 2 and acts as a cushion for a sheet 5 of sandpaper.

As better shown in Figure 5, the ends 6 and 7 of the sheet 5 pass through a radially extending slot 8 in the drum 2 into a recess 9 which extends the full length

- A -

of the drum 2 and accommodates a locking member 10.

As shown in Figure 4, the locking member 10 com¬ prises a bar of aluminium which is coextensive with the recess 9 and is provided at each end with a socket 11 which can accommodate a hexagonal key.

In the embodiment shown in Figures 1 to 5 the recess 9 was drilled to a diameter of mm. The locking member 10 was formed from aluminium rod of mm dia¬ meter leaving a clearance of mm between the rod and the recess 9.

As shown in Figure 5 a flat 12 is formed on the aluminium rod by machining a maximum of mm from one edge. The junction between one end of the flat 12 and the circumference of the rod is then radiused as shown by reference number 13.

In use, a sheet 5 of sandpaper is cut to approxima¬ tely the correct length, wrapped around the drum 2 and the ends 6 and 7 are pushed through slot 8 into recess 9. A hexagonal key is then inserted into socket 11 and rotated anti-clockwise. This action wedges the ends 6 and 7 between the locking member 10 and the recess 9. Any tendency for the ends 6 and 7 to be pulled into the recess 9 merely tightens the sandpaper about the drum 2 and slightly compress the layer 4. A tight fit is, of course, highly desirable.

The drum sander 1 is intended to be rotated at up to 3600rpm. In order to minimise vibration the position of the recess is preferably set so that the amount of material removed from the drum 2 for the recess 9 and the slot 8 is substantially dynamically balanced by the locking member 10 and the ends of 6 and 7 of the sheet 5.

When locking member 10 is rotated clockwise from the position shown in Figure 3, the ends 6 and 7 are ejected from the slot 8 thereby making the sheet 5 easy

to remove from the drum 2.

Figure 6 shows a miniature drum sander which is generally identified by reference numeral 101. The construction of the drum sander 101 is generally similar to the drum sander 1 and parts having similar functions have been identified by similar reference numerals to those used in Figures 1 to 5 but in the 100 series. The major difference between the embodiments is that the recess 109 lies on the longitudinal axis of the drum sander 101. Furthermore the drum 102 is made from solid steel.

In the embodiment shown in Figure 7, a drum sander 201 is covered with two sheets 205A and 205B of sandpa¬ per. The sheets 205A and 205B are secured to the drum sander by two locking bars 210 A, 210B mounted in re¬ spective recesses 209A, 209B provided on opposite sides of the drum 202.

Figure 8 shows a sheet 305 of abrasive material secured to a hand sander 301 by two locking members 310 which are disposed in respective recesses 309 as shown.

Typically, the diameter of the drum of the drum sander shown in Figure 6 would be about 25mm. The dia¬ meter of the drum shown in Figure 1 either 45mm or 60mm and the diameter of the drum shown in Figure 7 about 75mm.

The thickness of abrasive sheets varies signific¬ antly according to the grade of abrasive required. However, most sheets are about 1mm thick. The width of the slot 8 is therefore about 3mm. The diameter of the recesses 9 and the starting diameter of the rod from which the locking member 10 is formed is typically as follows : -

Diameter of Diameter of Diameter of Drum (mm) Recess 9(mm) Locking Bar

25 45 60 75

It will be noted that the locking member 10 acts between one part of the recess 9 and the ends 7 and 8 of the sheet 5 to trap the ends 6 and 7 against the oppo¬ site side of the elongate recess 9 over the entire length thereof. Whilst this is wholly recommended it is conceivable that an embodiment in which only a major portion of the length of the locking member is operative would be acceptable for light duty. Such might be achieved by, for example castellating the substantially circular portion and/or the flat of the locking member to provide spaced fingers of contact with the one side of the recess and/or the sheet of abrasive material.

Various modifications to the embodiments described are currently envisaged, for example whilst the inven¬ tion has been primarily developed for attaching sheets of material such as abrasive paper and polishing clothes onto drums, pads and blocks we have discovered that the invention has another very significant use.

In particular, in electrically powered planers it is conventional to mount the cutter blades (typically two) on a rotor which, in use, rotates at high speed. Positioning the cutter blades is relatively difficult involving first position each cutter blade and then clamping it in place by tightening three set screws which act against a plate which in turn acts on the cutter blade.

This procedure needs considerable skill since the cutter blade needs to be held in position while the set

screws are tightened.

We have found that if a cutter blade is inserted in the radially extending slot 8 rotation of the locking member 10 will retain the cutter blade in place.

Whereas aluminium is the preferred inelastic mater¬ ial for the locking member other suitable materials could comprise, for example steel. A rigid plastics material, could also be used.