Sanding attachment for a tool

Abstract

 A sanding attachment for a power tool in which the abrasive surface is provided on a drive disc (10) which is releasably secured to a two part articular drive shaft (11). A sleeve (12) is slidingly mounted on the drive shaft (11) and may be moved to a position in which movement of the two shaft parts (19, 21) relative to each other is allowed within predetermined limits or a position in which the two shaft parts (19, 21) are fixed in axail alignment with the drive disc 10.

Description

[0001] This invention relates to apparatus which may be fitted to tools in order that various operations may be performed on a desired object and in particular to a sanding attachment which may be fitted to a power tool.

[0002] In known apparatus for this purpose a sanding surface is mounted on a disc, the disc being mounted on a shaft via a flexible body part, the flexibility of the body part, and hence of the sanding attachment, being determined by the pressure exerted on the body part by screw adjustment means on the shaft and adjustable axially of the shaft to exert pressure on the body part and increase the rigidity of the attachment or to relieve the pressure on the body part and therefore increase the flexibility of the attachment.

[0003] However, with this known arrangement the problem arises that the attachment is complicated and expensive to construct and the amount of transverse flexibility, and the reproducibility thereof, relative to the shaft is minimal.

[0004] An object of the present invention is to provide an improved apparatus of the kind aforesaid.

[0005] According to the invention there is proposed an attachment for a power tool comprising a drive shaft and a driving disc releasably secured to said shaft in coaxial relationship thereto and adapted to receive an abrasive element into engagement therewith, characterised in that the said shaft comprises articularly connected parts and a control sleeve selectively movable relative to and axially of said parts to and from a position wherein said parts are secured in axially aligned disposition by the sleeve.

[0006] According to a preferred feature, the articulated connection between the shaft parts comprises a recess in a first shaft part and a ball at the adjacent end of a second shaft part, the ball being located in the said recess and being secured therein by a pin extending transversely of the recess and passing through an aperture in the ball.

[0007] According to a further preferred feature, the ball is angularly adjustable about the pin within predetermined limits.

[0008] According to a still further preferred feature, a clearance is provided between adjacent regions of the first and second shaft parts to define the adjustment limits aforesaid.

[0009] The invention will now be described further, by way of example only, and with reference to the single figure of the accompanying drawings which shows a sectional side elevation of one form of apparatus constructed in accordance with the invention.

[0010] Referring now to the drawing, the apparatus comprises a drive disc 10, a flexible drive shaft 11 arranged coaxially therewith and a sleeve member 12 movably mounted on the drive shaft 11 in a manner hereafter to be described in more detail.

[0011] The drive disc 10 is circular and has a dished central section 13 thereto. In the centre of the disc 10 there is a circular hole 14, through which a bolt 16 may extend. A self-adhesive annular foam rubber pad 17 of like outside dimensions to the disc 10 is attached to the outer surface of such disc. The inner diameter of pad 17 corresponds to the diameter of the dished portion 13 of the drive disc 10. Attached to the outer face of pad 17 is an annular pad 18 of Velcro (Registered Trade Mark) material of like radial dimension to pad 17 by which a sanding surface (not shown) can be removably attached to the drive disc 10.

[0012] The flexible drive shaft 11 comprises first and second shaft parts.

[0013] First shaft part 19 is generally cylindrical, is of stepped external configuration and has axial blind bores 22, 23 at the respective opposite ends thereof. The bore 22 at the outer end of the first shaft part 19 is screw threaded to receive bolt 16 whilst a pin 24 extends diametrically through the first drive shaft part in the region of blind bore 23, the wall of the shaft part having aligned holes 26, 27 therein to receive such pin.

[0014] As previously stated, the outer surface of the first drive shaft part 19 is of stepped configuration and radially outwardly extending flanges 28, 29 separated by a reduced diameter region 31, that flange at the outer end of the drive shaft part is screw-threaded to receive the corresponding end of the sleeve member 12.

[0015] The annular end face of the first shaft part at the inner end thereof is radiussed, as shown at 25 in the drawing.

[0016] Second shaft part 21 comprises in succession a spherical head 32, a tapered shoulder 33, a solid cylindrical body 34 and a solid cylindrical engagement member 36 adapted at the outer end to engage with a power tool (not shown). The spherical head 32 is provided with a diametric hole formed by two frusto-conical parts through which pin 24 extends joining the shaft parts together. The second shaft part 21 is also screw-threaded in the region of the tapered shoulder 33 to receive the corresponding end of sleeve member 12.

[0017] Sleeve member 12 is generally cylindrical and hollow and is screw threaded at both ends of the internal surface to engage with respectively the tapered shoulder 33 of the second shaft part 21 or the flange 29 at the outer end of the first shaft part 19.

[0018] Sleeve member 12 is slidingly received on the external surface of first shaft part 19 and selectively determines the flexibility or rigidity of the attachment. With the corresponding end of sleeve member 12 screwed into engagement with the first shaft part 19 in the region of its outer end then flexibility in the transverse direction is allowed by means of movement of second shaft part 21 relative to first shaft part 19 biassed by a spring 38 provided between the respective shaft parts. The amount of flexibility afforded may be determined by the relative dimensions of the frusto-conical hole 37 and the pin 24 and/or the clearance between the respective shaft parts in the region of the radiussed inner end of the first shaft part 19.

[0019] In a particularly preferred embodiment the relative movement of the drive shaft parts is restricted to 2.5° in the transverse direction.

[0020] However, with the sleeve member 12 screwed into engagement with the second shaft part 21 in the region of the tapered shoulder 33, the attachment is rigid with the two shaft parts maintained in axial alignment with the drive disc 10.

[0021] In this way it is possible for efficient coarse or fine sanding to be achieved depending on the rigidity or flexibility of the attachment.

[0022] It is, of course, to be understood that the invention is not intended to be restricted to the details of the above embodiment which is described by way of example only. Thus, for example, a like effect is thought to be attainable by providing a flexible, for example rubber, body between and secured to the first and second shaft parts in lieu of the ball and socket connection herein disclosed.

Claims

1. An attachment for a power tool comprising a drive shaft and a driving disc releasably secured to said shaft in coaxial relationship thereto and adapted to receive an abrasive element into engagement therewith, characterised in that the said shaft (11) comprises articularly connected parts (19, 21) and a control sleeve (12) selectively movable relative to and axially of said parts to and from a position wherein said parts are secured in axially aligned disposition by the sleeve.

2. An attachment according to claim 1, wherein the articulated connection between the shaft parts comprises a recess (23) in a first shaft part (19) and a ball (32) at the adjacent end of a second shaft part (21), the ball being located in the said recess and being secured therein.

3. An attachment according to claim 2, wherein the ball (32) is secured in the recess (23) by a pin (27) passing through an aperture (37) in the ball.

4. An attachment according to claim 3, wherein the aperture (37) in the ball comprises two axially aligned frustro-conical parts.

5. An attachment according to claim 3 or 4, wherein the ball (32) is angularly adjustable about the pin within predetermined limits.

6. An attachment according to claim 5, wherein the predetermined limits are defined by a clearance between adjacent regions of the first and second shaft parts.

7. An attachment according to claim 5, wherein the predetermined limits are defined by the relative dimensions of the pin (27) and the aperture (37) in the ball.

8. An attachment according to any one of claims 5 to 7, wherein the predetermined limit is 2.5° either side of the axis of the attachment.

9. An attachment according to any one of the preceding claims, wherein the control sleeve (12) is screw threaded on its internal surface for selective engagement with cooperable screw threads (29, 33) on the respective said parts.

10. An attachment according to any one of the preceding claims, further including biassing means (38) acting on the ball.

11. An attachment according to claim 10, wherein the biassing means comprises a spring.

12. An attachment according to any one of the preceding claims, wherein the drive disc (10) is attached to the drive shaft (11) by a single bolt (16).

Drawing