GB2159619A - Hand power disc sander dust extracter - Google Patents

Abstract

A hand power disc sander is fitted with a dust-proof hood in the form of flexible bellows (F) and evacuated by an extractor fan (e.g. a vacuum cleaner via a flexible hose). Grooves (H) in the hood rim (G) permit inflow of air over the work surface. The flexible bellows (F) permit engagement and tilting of the sander disc without disturbing the position of the rim of the hood. The rim is held against the work surface principally by the suction of the extractor fan. The bellows are so constructed as to resist lateral movement of the rim to prevent fouling the sanding disc. A variable air-bleed (R) is incorporated in the combined outlet pipe and supplementary handle (E) to compensate for the varying power of different vacuum cleaners. The invention may also be applied to a disc sander in which a single motor drives both the sanding disc and the extractor fan. <IMAGE>

Description

SPECIFICATION Hand power disc sander dust extracter This invention provides a means of containing the dust produced by a hand-held disc sander or a sanding disc used on a hand-held power drill.

The flexible sanding disc used with a handheld disc sander or more typically an electric drill with disc sanding attachment is widely used not least by the home handyman in a domestic environment. It is a very quick, cheap and effective way to sand down large areas, but the main disadvantage is the vigorous dispersal of dust. When used for sanding walls, floors or ceilings in home, office or industrial environments, the protection of furniture, carpets, machinery etc., and the subsequent removal of dust is often more timeconsuming than the actual sanding operation.

This invention allows a hand power drill with sanding disc attachment, or a hand power disc sander to be used in conjunction either with a domestic or industrial vacuum cleaner, or with a built-in extracter fan and dust-bag, on large substantially flat surfaces with complete containment of dust, avoiding the need to remove carpets, furniture, etc., or to use dust-sheets, in domestic, office or industrial environments. Existing designs of sanders with dust extraction facilities draw air away from the point of dust production but do not positively contain the dust, and in any case are not applicable to disc sanders.

The invention consists of a hood of box or cylindrical shape, closed at one end. The closed end is attached and sealed to the body of a power disc sander or a power drill with sanding disc attachment. The plane of the rim of the open end of the hood normally lies at least level with the plane of, and surrounds the sanding disc, but the rim may move axially by virtue of a flexible coupling at some point between the rim and the point of attachment to the drill or sander body. An aperture in the otherwise closed end of the hood is connected to the flexible hose of a vacuum cleaner or to the inlet of a built-in extracter fan. In use, the rim of the hood is held against the surface being sanded principally by the suction of the vacuum cleaner or extracter fan, also the elasticity of the flexible coupling.Notches around the rim of the hood are so proportioned as to permit an adequate influx of air, whilst maintaining sufficient pressure difference to hold the hood firmly against the surface being sanded without clamping it so tightly as to impede lateral movement. The size of the notches must be suited to the power of the extracter fan, and when this is a vacuum cleaner a variable air-bleed to compensate for the varying power of different types of vacuum cleaner must be provided.

Due to the flexible coupling, the sanding disc can be brought to bear at the appropriate angle without disturbing the rim of the hood.

The Flexible coupling is best achieved by constructing the walls of the hood in the form of a bellows, as this permits the necessary tilting of the plane of the rim of the hood in relation to the closed end of the hood without excessive lateral displacement of the rim of the hood in relation to the sanding disc. This is important in order to permit the minimum clearance between rim and sanding disc, allowing the device to sand as close as possible to edges and corners of work surfaces.The bellows must also (a) have a very high resistance to lateral displacement of the rim. (b) have sufficient stiffness only to ensure that, when in the normal, or relaxed, position, the bellows support the rim at least level with the sanding disc to ensure initial engagement of the rim with the work surface and (c) permit some degree of flexibility of the rim relative to its normal plane to enable other then perfectly flat work surfaces to be engaged. All of the above requirements are met by the adoption of camera bellows folding technique, either in the traditional square plan form, or adapted to hexagonal or octagonal shape. A flexible but essentially non-elastic material is required, and various types of plastic-coated fabric are suitable, with stiffening panels of, typically, thin hard cardboard.The stiffening panels are pleated and extend the full length of the bellows; this permits much quicker and simpler construction, and contributes to the required "stand-off" in the relaxed position, as compared with individual stiffeners for each fold, as used on traditional camera bellows.

Both stand-off and inherant stiffness, however, are controlled largely by the cross-over folds at the corners of the bellows, and may be adjusted by varying the thickness of the plasticised fabric or the number of corners (e.g. octagonal vis-a-vis square bellows). Suitable bellows could also be made by plastic moulding techniques, circular in plan form; unit costs would be reduced at the expense of substantial initial capital investment.

The rim of the hood must provide the controlled influx of air whilst maintaining even and close contact with the work surface. The interface between rim and work-surface must have low co-efficient of friction and high resistance to wear of the rim. The rim must have some degree of flexibility to accommodate other than perfectly flat work surfaces. These requirements are met by attaching slightly convex rectangular pads formed from hard sheet metal, to a flexible but non-elastic backing strip. The pads are attached---convex side away from the backing strip-by folding over two sides of each pad and pinching them over the edges of the backing strip. In practice, the backing strip is the final fold of the bellows.

The pads are close pitched, and the narrow gaps between them, combined with the con vexity of the pads, provide the apertures for air influx.

A specific embodiment of the invention in a dust extracter for use with a hand power drill and sanding disc is shown in Fig. 1. This is suitable for use with any power drill (A) which has the usual accessory flange (B). The closed end of the hood comprises a back plate (C) of 1.5 mm light allow sheet attached by screws or rivets to a light alloy casting (D) which provides the attachment socket for the drill accessory flange, secured by two grub screws at 90 (not shown) and a further socket for the outlet pipe (E) which accepts a vacuum cleaner hose, and also acts as an auxiliary handle. This outlet pipe is interchangeable in order that different makes of vacuum cleaner can be accommodated. The bellows (F) are constructed from plastic coated fabric approximately 0.3 mm thick, using camera bellows folding technique adapted to a basically octagonal plan form.The eight pleated stiffening panels are made from hard cardboard, approximately 0.3 mm. thick, attached by impact adhesive. At the point of attachment to the circular back-plate, the four inward-facing end folds fit behind, and the four outward-facing end folds fit to the front of the back-plate; they are further secured by adhesive to prevent accidental displacement of air leaks. The dimensions of the bellows permit the use of discs (J) up to 178 mm in diameter and with a bellows fold width of 24 mm the cross-over folds are roughly equal to the straight folds on the outside, as shown in Fig. 2. The rim can thus conveniently comprise sixteen identical pads (G) which clip directly on to the terminating folds of the bellows. The pads are pressed from bright stainless steel sheet 0.4 mm in thickness, the convex area standing 2.0mm.

above the backing strip (i.e.; end fold of bellows). The ends of the pads are spaced 3.00 mm apart and this permits the required controlled air influx (H). The rate of wear of the pads is very low when used on most interior constructional or decorative materials, but increases when used over bare brick, stone or concrete, to the extent that sets of pads should be available as spares. Pads can be removed and fitted with square-nosed pliers. Four of the sixteen pads are shown in position in Fig. 2. Some improvement in the integrity of the basically circular plan-form of the complete rim results if the pads are made in the form of a trapezium rather than as a true rectangle as shown in Fig. 2, but this is not essential.

In use, a drill is secured in the back plate socket with the handle of the drill at approximately 90 to the combined outlet pipe and auxiliary handle, as seen in plan view, of the back plate. The vacuum cleaner hose lies under the operator's right fore-arm and protrudes behind the operator where it is least likely to obstruct normal control. The 45 angle of attachment of the outlet pipe to the back plate is partly determined to aid the smooth flow of the dust/air mixture which acquires an element of rotary motion in the hood due to the normal direction of rotation of the sanding disc. The variable air-bleed is effected by means of a rotating sleeve (R) over a hole (S) in the outlet pipe (E).Easy control of the air-bleed in use can be an advantage in certain circumstances, e.g. when sanding ceilings the suction can be increased to support the weight of the sander.

The back-plate is at all times parallel to the normal plane of the sanding disc, and provides a ready visual assessment of the correct engagement angle for the sanding disc.

A specific embodiment of the invention in a purpose designed disc sander is shown in Fig.

3. The general arrangement is similar to the design in Fig 1 except that the outlet from the hood feeds to the inlet of a centrifugal extracter fan (K) directly coupled to the motor shaft, with step-down gearing (L) located between the extracter fan casing and the hood. The outlet of the extracter fan feeds into a directly attached dust-bag (M). The power required to operate the extractor fan is considerably greater than in existing designs of belt or orbital sanders with a dust extracter facility, and any appreciable speed reduction on heavy loading of the sanding disc will result in loss of suction. For these reasons the motor (N) must be liberally rated, and the design is best suited to a powerful tool for professional use.

The cost would be justified where maximum operating convenience is an economically important consideration. Fig 3 illustrates only a typical relationship between hood, gearing, extracter fan and motor, and shows no details of handles, switch or precise shape of, or support for the dust bag, these details not being peculiar to this application of the invention. In Fig. 3 the hood is illustrated in a typical working position the work surface being represented by the dotted line (P) whereas in Fig. lit is in the relaxed or disengaged position.

Claims (11)

1. A dust extracter for a hand power disc sander which contains dust by means of a hood, one closed end of which incorporates and is sealed to the body of the power sander, and the other, open, end surrounds and lies approximately level with the sanding disc. Air and dust are drawn from the hood via an aperture in the closed end by an extracter fan, and air is drawn into the hood over the work surface via shallow grooves in the rim of the open end of the hood which is otherwise held in contact with the work surface principally by the partial vacuum within the hood. The walls of the hood are constructed in the form of a bellows to enable the rim to remain in contact with the work surface when the sander body is tilted to achieve the correct engagement angle of the sanding disc.The rim of the hood is located concentrically with the sanding disc and is constrained from lateral movement relative thereto by the methods of construction of the bellows.

2. A dusct extracter for a hand power disc sander as claimed in Claim 1 wherein the rim of the hood consists of slightly convex rectangular pads formed from hard sheet metal attached by means of turned-over edges to a flexible but non-elastic backing strip, the necessary air inlet grooves being formed by the narrow gaps between adjacent pads.

3. A dust extracter for a hand power disc sander as claimed in Claims 1 and 2 wherein the necessary characteristics of the bellows are achieved by using an adaptation of folding techniques as used in traditional camera bellows of the cross-over fold type, to form a bellows of basically octagonal plan-form, but so proportioned that the cross-over folds are equal in length to the eight sides resulting in a regular sixteen-sided perimeter. The final fold of the bellows thus forms the flexible backing strip for a sixteen element rim.

4. A dust extracter for a hand power disc sander as claimed in any preceding claim wherein the function of the extracter fan is performed by means of a vacuum cleaner connected by its flexible hose.

5. A dust extracter for a hand power disc sander as claimed in Claim 4 wherein the dust extracter comprises a readily detachable accessory for use with a hand power drill with disc sander attachment.

6. A dust extracter for a hand power disc sander as claimed in Claim 5 wherein the outlet pipe of the dust extracter hood to which is attached the vacuum cleaner hose, being rigidly attached to the closed end of the hood and the hand power drill body, is so aligned as to serve also as a second handle to complement the handle of the hand power drill.

7. A dust extracter for a hand power disc sander as claimed in Claim 6 wherein a variable air-bleed is incorporated to accommodate the varying power of different vacuum cleaners.

8. A dust extracter for a hand power disc sander as claimed in Claim 7 wherein the variable air-bleed is located in the combined outlet pipe and complementary handle in such a way as to facilitate ready adjustment of the air-bleed when the sander is in use.

9. A dust extracter for a hand power disc sander as claimed in Claims 1-3 wherein the high-speed motor of the disc sander drives an extracter fan directly by the motor shaft, and the sander disc via suitable reduction gearing.

10. A dust extracter for a hand power disc sander substantially as described herein with reference to Figs. 1 and 2 of the accompanying drawings.

11. A dust extracter for a hand power disc sander substantially as described herein with reference to Fig. 3 of the accompanying drawings.