WO1998053955A2

WO1998053955A2 - An improved abrasive disc and backing plate therefor

Info

Publication number: WO1998053955A2
Application number: PCT/NZ1998/000068
Authority: WO
Inventors: Adrian George Bogalo
Original assignee: Bogalo Adrian
Priority date: 1997-05-28
Filing date: 1998-05-28
Publication date: 1998-12-03
Also published as: AU7941898A; WO1998053955A3

Abstract

A ring-shaped abrasive disc (1) has a series of tabs (3) around the disc (1) which are used to secure it to a backing plate (10), which includes slots (11) arranged around its periphery for receiving the tabs (2). The backing plate (10) may also include an impeller to blow air over the abrasive disc (1) to provide cooling or remove swarf from the work surface.

Description

AN IMPROVED ABRASIVE DISC AND BACKING PLATE THEREFOR FIELD OF THE INVENTION

The present invention relates to an abrasive disc and a backing plate for mounting the disc to a circular sander or grinder. The invention also relates to a method of manufacture of an abrasive disc.

BACKGROUND OF THE INVENTION

Conventional abrasive discs, or disks, consist of a, generally, circular disc with a small central aperture. This aperture is merely provided for a spindle of the driving machine to protrude through. A locking member is screwed to the spindle to clamp the disc about the aperture to secure the disc in place.

One disadvantage of such a conventional system is the time taken to replace a disc. Replacing a disc requires unscrewing and rescrewing of the locking member.

Another disadvantage of the conventional disc is their inefficient use of materials. This arises from the fact that, in use, only an outer portion of the disc contacts a work piece. The inner portion is effectively wasted.

Another problem associated with some conventional systems is that the work piece is heated up by the continuous friction of the disc on it. This heating can damage some work pieces.

An attempt at overcoming some of the above disadvantages is the use of VELCRO (Trade Mark), or such like, to attach the disc to the backing plate. This facilitates faster replacement of discs. However, the limited strength of VELCRO (Trade Mark) restricts its application to low speed or low torque abrasion. Certainly, the grinding of metals is not within the capabilities of such a system.

Another attempt to overcome some of the problems outlined above is a system in which the disc and mounting means have formed therein circular holes positioned in a circle around the disc. A suction is created out through the holes when the disc rotates. This suction provides cooling

SUBSTITUE SHEET (Rule 26) of the work piece. However, the attachment of the disc to the driving machine is conventional, so this system does not address any of the other problems mentioned above.

It is an object of the present invention to reduce or overcome the above disadvantages of prior art devices or at least to provide the public with a useful choice.

Other objects of the invention may become apparent from the following description which is given by way of example only.

SUMMARY OF THE INVENTION

According to one aspect the invention consists of an abrasive disc including: a disc portion; at least two projecting portions provided on the disc portion.

Preferably the projecting portions are tabs which are, further, preferably arranged around the periphery of the disc portion.

Preferably the disc portion is annular having an outer periphery and an inner periphery where, further, preferably the area defined by the inner periphery is greater than about one fifth of the area defined by the outer periphery.

Another aspect of the invention consists of an abrasive disc including: an annular portion having an outer periphery and an inner periphery; wherein the area defined by the inner periphery is greater than about one fifth of the area defined by the outer periphery.

Another aspect of the present invention consists of a backing plate for an abrasive disc, said backing plate including: a first surface which may support an abrasive disc;

SUBSTITUE SHEET (Rule 26) a second surface distal from the first surface; and a set of engagementtions adapted to engage tabs on an abrasive disc.

Another aspect of the present invention consists of a backing plate or an abrasive disc, the backing plate including: a first surface which may support an abrasive disc; a second surface distal from the first surface; a recessed region formed in the first surface and positioned centrally with respect to the first surface; at least one conduit passing from the first surface to the second surface and adapted such that when the backing plate rotates, in use, air from the surrounds of the backing plate is forced through the conduit.

Preferably the backing plate of the paragraph immediately above includes a kinetic pump, such as an impeller or turbine, which is adapted to force air in to or out of the recessed region when the backing plate rotates in use.

A further aspect of the present invention consists of a method of manufacturing an abrasive disc, the method including the steps of: providing a sheet of abrasive materials; forming an annular disc from the material; and providing projecting portions around the annular disc.

Preferably the projecting portions are tabs which may include a crease at the join between the tab and the annular disc.

A further aspect of the present invention consists of a method of manufacturing two abrasive discs, the method including the steps of: providing a sheet of abrasive material; forming a first abrasive disc from the sheet of abrasive material;

SUBSTITUE SHEET (Rule 26) removing a portion of the first abrasive disc, the portion being concentric with respect to the first disc, to form a second abrasive disc.

Other aspects of the invention may become apparent from the following description which is given by way of example only and with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 :

Shows a top perspective view of a disc according to the present invention.

Figure 2:

Shows a top view of a backing plate according to an embodiment of this invention. The tabs of the attached disc are visible.

Figure 3:

Shows a side view of a backing plate according to an embodiment of the invention.

Figure 4:

Shows a cross section side view along the line B-B of the backing plate of Figure 2.

Figure 5:

Shows a cross-section side view of the backing plate according to an alternative embodiment of the present invention.

Figure 6:

Shows a section through the line A-A of the backing plate of Figure 5.

Figure 7:

Shows a cross-section side view of the backing plate shown in Figure 5 and including an impeller, in an exploded position, which is not cutaway.

SUBSTITUE SHEET (Rule 26) Figure 8:

Shows a cross-section through the line D-D of a backing plate according to a further alternative embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Figure 1 shows an abrasive disc 1 according to an embodiment of the present invention. The underside of the disc 1 is not shown, but merely consists of a flat surface with abrasive particles embedded in it or any coating known in the art for use in abrasive or frictional treatment of surfaces. The direction of rotation of the disc in use is depicted by the arrow C.

The disc 1 is, typically, formed from conventional abrasive paper, fibre or card. Suitable materials will be apparent to those skilled in the art.

The disc 1 has a relatively large circular portion 2 cut out from its centre. The area of the centre portion 2 is approximately equal to about one third of the total area defined by the periphery of the disc 1 in the case of one preferred embodiment. Typically however, the diameter of the cut-out portion is 5 cm or more. In most cases the area of the cutout is more than one fifth of the total area defined by the outside periphery of the dish. The suitable size of the centre portion 2 is determined by the portion of a conventional disc which has only limited, or occasional, contact with a work piece when in use and also by the minimum width needed to secure the discs to the backing plate. Any region of a disc which would not contact the work piece would be essentially, wasted. The cut-out portion 2 may be used separately to form a smaller conventional abrasive disc.

The disc also has a number of tabs 3, or projections, formed by cuts or lines of weakness, in the disc 1 . These tabs may be folded upwards along fold lines, or creases, stamped into the disc. However, it may be preferred that no fold lines are formed. Figure 1 shows four tabs 3, although any suitable number may be used. The tabs 3 are formed to point in the same direction around the disc 1 . This direction is opposite to that which the disc rotates in use.

SUBSTITUE SHEET (Rule 26) The tabs 3 are typically cut to have as smooth a shape as possible. This acts to maximise the strength of the tabs and also tends to cause less wear on the cutting tool during manufacture.

Typically during manufacture of the discs, a large disc will be formed and then the removed portion 2 will be formed from that larger disc leaving a ring-shaped portion. Then a disc is formed from the ring- shaped portion by the addition of the tabs 3 and a conventional disc is formed from the removed portion 2 by methods apparent to those skilled in the art.

Figure 2 shows a backing plate 1 0 for the abrasive disc 1 according to the present invention. The backing plate has slots 1 1 formed in it. The tabs 3 of an attached abrasive disc 1 protrude through the slots 1 1 . The slots are radial, but their cut-away profile viewed in the axis of the slots is angled, or inclined, in a direction around the backing plate 1 0 opposite to which the backing plate rotates in use. The fitting of tabs 3 is facilitated by the slots 1 1 being thus angled. Also, when the abrasive disc 1 is in contact with the work piece, a frictional torque is generated on the disc in the direction opposite to that in which it rotates. This force drives the tabs 3 further into the slots 1 1 and against the backing plate 1 0. This action secures the abrasive disc 1 to the backing plate 10.

The backing plate 1 1 may also include a spring clip 1 2. The ends of the spring clip are biased downwards against the backing plate 1 0 over two of the slots. The spring clip 1 2 is used to secure two of the tabs against the top of the backing plate 1 0. This securement helps prevent the abrasive disc from becoming loose or detaching from the backing plate 1 1 when the abrasive disc 1 is not in contact with a work piece. It will be appreciated that the spring clip may be in a modified form to secure any number of tabs of the disc.

Means may be provided to limit the chance of damage to the tabs and/or disc during operation of a grinder or the like employing a disc and backing plate of the present invention. Thus, the backing plate may be arranged to transfer force to the ends of the tabs rather than the joining

SUBSTITUE SHEET (Rule 26) border of the tabs to the rest of the disc. This may be done by having stops or abutments, such as 33 shown in Figure 8 and discussed later, on the rear side of the backing plate adjacent the slot exits. Another way of achieving this may be to have blind slots which terminate at one end and having the ends of the tabs abut against these ends in use. Alternative arrangements will be apparent to those skilled in the art. It will also be apparent to those skilled in the art that the slots are preferably formed at as acute an angle as possible to further limit stress on the tab joins.

Suitable methods of connecting the backing plate to a grinding or sanding machine will be apparent to those skilled in the art. The preferred embodiments of the present invention employ a conventional spigot type attachment of the backing plate by way of the aperture 1 3 to a grinding or sanding machine.

Figures 3 and 4 show a side view and cut-away side view of the backing plate 10. The spring clip is not shown in Figures 3 and 4.

Figures 5 and 6 show an alternative embodiment where the backing plate 20 has angled conduits 21 formed in it. The conduits 21 may be angled both radially and in the direction of rotation of the backing place. Angling in the direction of rotation of the backing plate causes air to be forced down on to a work piece when the backing plate rotates in use. The radial angling of the apertures directs the air through the central cut-away portion 2 of the disc 1 into the recessed portion. The air will then pass outwards across the working surface of the disc. This flow of air serves to both cool the work piece and also to blow away swarf from the grinding area. By reversing the direction in which the apertures 21 point, the backing plate will suck air upwards. Any advantages to providing suction rather than blowing will be apparent to those skilled in the art and may vary on a case-by-case basis.

In another embodiment the set of conduits 21 may be formed such that the central portion of the backing plate resembles a turbine with the portions between adjacent apertures resembling fins of a turbine.

SUBSTITUE SHEET (Rule 26) Figure 7 shows a backing plate, or mounting member 20 and impeller, turbine, or similar, 30 according to a further aspect of the invention. The backing plate 20 has a recessed portion 31 formed in its lower side. In the embodiment shown in Figure 7, the recessed portion is shaped to accommodate the impeller 30.

The impeller 30 may serve to improve the air flow over the disc. Suitable arrangements of impeller will be apparent to those skilled in the art. Alternatives to the impeller for particularly directing air flow out past the attached disc will be apparent to those skilled in the art. The impeller 30 may be separable from the backing plate or it may be integrally formed with the backing plate.

Figure 8 shows a cut-away section of another backing plate 10 according to the most preferred embodiment of the present invention. The backing plate 1 0 includes a slot 1 1 which extends at an acute angle to the disc. This facilitates fitting of the tabs 3 into the slots 1 1 and to reduce the tendency for the abrasive disc to tear under stress. Recessed portions 34 may also be formed in the backing plate 1 0 to further facilitate fitting of tabs 3 into the slots 1 1 . The slot 1 1 may also include a slot end, or tab abutment portion, 33 against which the end of the tab 3 may abut. Between the abutment portion 33 and overhanging portion 35, some of the driving force may be transferred to the tab 3. The remainder of the driving force will be transferred by a tab contact surface 36 which preferably includes a metal, wear resistant plate.

The use of the abrasive disc and backing plate of the present invention may allow an abrasive disc to be changed faster than with a conventional disc arrangement. This facilitates achieving greater productivity in a manufacturing situation. The time saving arises from the fact that a central locking member does not have to be unscrewed from the spigot to change the disc.

SUBSTITUE SHEET (Rule 26) A disc of the present invention requires less material than a conventional disc, the removed portion 2 being usable to form a second smaller disc.

The arrangement of conduits, turbines, and/or impeller with the annular disc provides a flow of air onto the work piece to both cool the work piece, to prevent damage from overheating, and to blow filings or swarf away from the work piece.

Where in the foregoing description reference has been made to specific components or integers of the invention having known equivalents then such equivalents are herein incorporated as if individually set forth.

Although this invention has been described by way of example and with reference to possible embodiments thereof, it is to be understood that modifications or improvements may be made thereto without departing from the scope of the invention as defined in the appended claims.

SUBSTITUE SHEET (Rule 26)

Claims

1 . An abrasive disc including: a disc portion; at least two projecting portions provided on the disc portion.

2. An abrasive disc as claimed in claim 1 , wherein the projecting portions are tabs.

3. An abrasive disc as claimed in claim 1 or claim 2, wherein the projecting portions are integral with the disc portion.

4. An abrasive disc as claimed in any one of the preceding claims, wherein the projecting portions have a joining border along which they are joined to the disc portion, and at least one engageable border which is free from the disc when in use.

5. An abrasive disc as claimed in any one of the preceding claims, wherein the projecting portions each project substantially transversely to a radial line from the centre of the disc.

6. An abrasive disc as claimed in any one of the preceding claims, wherein the projecting portions each extend in substantially the same direction around the disc.

7. An abrasive disc as claimed in any one of the preceding claims, wherein the projecting portions are arranged substantially around the periphery of the disc.

8. An abrasive disc as claimed in any one of the preceding claims, wherein the projecting portions substantially point in a direction opposite the direction of rotation of the disc in use.

9. An abrasive disc as claimed in claim 4, including at least one crease along at least a portion of the joining border.

SUBSTITUE SHEET (Rule 26)

10. An abrasive disc as claimed in any one of the preceding claims, wherein the disc portion is annular having an inner periphery and an outer periphery.

1 1 . An abrasive disc as claimed in claim 1 0, wherein the area defined by the inner periphery is greater than about one fifth of the area defined by the outer periphery.

1 2. An abrasive disc as claimed in claim 10 or claim 1 1 , wherein the diameter of the inner periphery is greater than about 5 cm.

1 3. An abrasive disc including: an annular portion having an outer periphery and an inner periphery; wherein the area defined by the inner periphery is greater than about one fifth of the area defined by the outer periphery.

1 4. A backing plate for an abrasive disc, said backing plate including: a first surface adapted to support an abrasive disc; a second surface distal from the first surface; and a set of engagement portions adapted to engage tabs on an abrasive disc.

1 5. A backing plate as claimed in claim 1 4, wherein the engagement portions are slots defining a first surface aperture and a slot end.

1 6. A backing plate as claimed in claim 1 5, wherein the slot end includes a surface against which a tab of an abrasive disc may abut.

1 7. A backing plate as claimed in claim 1 5, wherein at least one slot may extend through the backing plate so that the slot end defines a second surface aperture in the second surface.

SUBSTITUE SHEET (Rule 26)

1 8. A backing plate for an abrasive disc as claimed in any one of claims 1 5 to 1 7, wherein the slots are arranged such that the first surface apertures are aligned substantially radially with respect to the backing plate.

1 9. A backing plate as claimed in any one of claims 1 5 to 1 8, wherein the first surface may comprise a disc attachment portion which is substantially flat and annular and disposed at the periphery of the first surface and wherein first surface apertures are disposed in the disc attachment portion.

20. A backing plate as claimed in any one of claims 1 5 to 1 9, wherein each slot end is displaced angularly from the respective first surface aperture so that the slots are substantially inclined with respect to the first surface.

21 . A backing plate as claimed in any one of claims 1 7 to 20, further including at least one securing portion adapted to apply pressure to the second side of the backing plate in the region of at least one second surface aperture.

22. A backing plate as claimed in any one of claims 1 4 to 21 , further including: a recessed region formed in the first surface and positioned centrally with respect to the first surface; at least one conduit passing from the first surface to the second surface and adapted such that when the backing plate rotates, in use, air from the surrounds of the backing plate is forced through the conduit.

23. A backing plate as claimed in claim 22 further including a set of engagement portions adapted to engage tabs on an abrasive disc.

SUBSTITUE SHEET (Rule 26)

24. A backing plate as claimed in claim 22 or claim 23, wherein the at least one conduit may be arranged to include an opening to the first surface that is disposed in the recessed region.

25. A backing plate as claimed in any one of claims 21 or 24, wherein the at least one conduit may be arranged to force air radially with respect to the backing plate.

26. A backing plate as claimed in any one of claims 21 to 23, including a kinetic pump adapted to force air into the recessed region when the backing plate rotates.

27. A backing plate as claimed in any one of the claims 22 to 25, including a kinetic pump adapted to pump fluid out of the recessed region to the second surface of the backing plate when the backing plate rotates.

28. A backing plate as claimed in any one of claims 22 to 27, including a flow directing means which when the backing plate rotates, causes air to flow from the recessed region substantially radially over the first surface.

29. A method of manufacturing an abrasive disc, the method including the steps of: providing a sheet of abrasive material; forming an annular disc from the material; and providing projecting portions around the annular disc.

30. A method as claimed in claim 29, wherein the projecting portions are tabs.

31 . A method as claimed in any one of claims 29 or 30, wherein the projecting portions are provided by forming lines of weakness in the annular disc.

32. A method as claimed in any one of claims 29 or 30, wherein the projecting the portions are provided by forming cuts in the annular disc.

SUBSTITUE SHEET (Rule 26)

33. A method as claimed in any one of claims 29 to 31 , further including forming at least one crease substantially where the projecting portions are joined to the annular disc.

34. A method of manufacturing two abrasive discs, the method including the steps of: providing a sheet of abrasive material; forming a first abrasive disc from the sheet of abrasive material; removing a portion of the first abrasive disc, the portion being concentric with respect to the first disc, to form a second abrasive disc.

35. An abrasive disc substantially as herein described and illustrated with reference to the accompanying drawings.

36. A backing plate for an abrasive disc substantially as herein described and illustrated with reference to the accompanying drawings.

37. A method of manufacture of an abrasive disc substantially as herein described with reference to the accompanying drawings.

SUBSTITUE SHEET (Rule 26)