GB2069893A

GB2069893A - Apparatus for sanding timber surfaces

Info

Publication number: GB2069893A
Application number: GB8101147A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-01-21
Filing date: 1981-01-15
Publication date: 1981-09-03
Also published as: IT1145909B; SE8100090L; FR2473933A1; GB2069893B; ES498644A0; NL8007032A; DK26181A; ES8200830A1; CA1154258A; IT8112415A0

Abstract

A device for sanding surfaces, more particularly moulded surfaces, of timber components, comprises a wheel member 4 consisting of elastomeric material, and at least one sanding belt 6, which at least partially surrounds the circumference of the wheel member 4. The wheel member is coaxially mounted on a support bush 1. Two stressing discs 3a, 3b of metal are disposed on the support bush one on each side of the wheel member to grip the wheel member. The belt may comprise a plurality of portions on a resilient supporting film, the ends of which are joined by an overlapping resilient member. <IMAGE>

Description

SPECIFICATION Apparatus for sanding timber surfaces The invention relates to an apparatus for sanding the surfaces, more particularly moulded surfaces, of timber components, with a wheel member the circumference of which is at least partially surrounded by at least one sanding belt.

An apparatus of this kind is intended particularly for sanding moulding surfaces of timber components, for example in the furniture industry. According to the prior art, these sanding wheels are provided with a rigid base member which can be mounted on a sanding spindle and extends over the greater part of the radius of the moulding sanding wheel and the circumference of the basic member is provided with a resilient covering which in turn is surrounded on the circumference, at least indirectly, by a sanding belt. As seen in cross-sectional view, the circumferential surface of the resilient covering has a contour shape which complements the moulding contour of the moulded surface which is to be sanded and the sanding belt, placed or adhesively affixed to the circumferential surface, also follows the moulding contour.

Known moulding sanding wheels suffer from the disadvantage that they are still relatively hard and therefore unyielding despite the resilient covering on the external circumference and that accordingly they can be guided with only slight pressure against the timber which is to be sanded and that nevertheless premature loss of the abrasive particles from the sanding belt, burning or tearing of the sanding belt frequently occurs during the sanding operation. Sanding of timber with inaccurate mouldings therefore gives rise to problems which interfere with production, for example in furniture construction. Moulding inaccuracies of this kind result necessarily from the constant regrinding of the moulding tools but also from drying of the timber, and from incorrect guiding of the workpiece on the moulding machine and so on.

It is the object of the invention to provide an improved device with substantially greater resilience on the circumference but being nevertheless capable of following the timber surfaces, which are to be finish-sanded, more closely during the sanding operation.

According to the invention this problem is solved in that the wheel member consists of elastic material, more particularly soft, extensible rubber, and is coaxially mounted on a support bush and that stressing discs of metal are disposed on the support bush on both sides of the wheel member to grip the wheel member.

This embodiment offers the advantage that owing to its extension resulting from centrifugal force, the soft material of the wheel member is able to yield more readily during sanding; this is because the resiliency force acts opposite to the expanding centrifugal force and thus provides substantial adaptation to the moulding inaccuracies of the material which has to be sanded. Sanding does not therefore give rise to high local contact pressures between workpiece and sanding wheel with the initially described adverse consequences. The sanding operation itself is improved and the service life of the sanding wheel is substantially prolonged. Owing to the extensibility of the wheel member and the resultant improved yield of the resilient material it is possible to operate with a relatively high sanding pressure.At excessive sanding pressures the wheel member yields more readily, or, as a result of centrifugal force, stretches more closely on to the workpiece if the contact pressure is too low. This substantially prevents abrasive particles of the sanding belt breaking out of the bond, even at a high sanding pressure, or burning of the sanding belt.

By virtue of these working properties it is possible to obtain large moulding contours with only one sanding wheel along all planes. The extension obtained by centrifugal force leads to optimum penetration of the abrasive particles into the workpiece so that only one sanding operation achieves an exceptionally good result.

One further embodiment of the invention is arranged so that one end of the support bush is provided with a flange and the other end of the bush is provided with an internally threaded collar which can be mounted on an externally threaded bush portion. This construction of the moulding sanding wheel permits simple manufacture on the one hand and the exchanging of damaged wheel member or stressing discs on the other hand.

During sanding, the stressing discs, more particularly constructed as metal discs, prevent lateral deflection of the wheel member but permit radial extension of the wheel member such as under the effect of centrifugal force.

Advantageously, a soft, extensible rubber of high quality is used for the wheel member. For example, it is also possible to use plastics materials.

According to another embodiment of the invention the stressing discs are provided with retaining pins which project inwardly against the wheel member. This step prevents relative rotation of the wheel member with respect to the support bush. The retaining pins are disposed coaxially opposite each other and each projects into an associated bore of the wheel member.

The invention also extends to moulding sanding wheels with sanding belts which circulate over only part of the circumference of the wheel member and are also guided over a second axially parallel pulley. The circumferential surface of the wheel member can have any desired and suitable moulding profile but it can also be constructed in flat form, for example like a sanding pulley.

If an endless sanding belt, formed by joining the ends of a strip, is loosely placed around the cylindrical wheel member with a flat circumferential surface, it is possible for the resilient material of the belt to be extended by centrifugal forces during rotation of the wheel member. Such an extension is possible however only until the increasing diameter of the wheel member has reached the width of the surrounding sanding belt. The walls of the cylindrical wheel member will then place from the inside against the sanding belt so that the wheel member surrounded by the sanding belt is converted into a rigid and fixed element and the sanding advantages, which can be achieved by the resilience of the wheel member, are again lost.

In order to utilize the advantages of a resilient wheel member in flat sanding, the sanding belt is resilient in accordance with one advantageous further embodiment.

Owing to the resilience of the sanding belt, the resilience of the wheel member of rubber is also fully retained, since the sanding belt is able to adapt itself to all changes of diameter of wheel member during sanding, for example those resulting from centrifugal forces or a varying sanding pressure.

Sanding belts comprise a paper or fabric which is provided on one side with a layer of abrasive particles. The sanding belt can be assembled from a plurality of strip-shaped portions and the joints between the portions are resilient in accordance with the invention. However, a preferred embodiment provides that an endless sanding belt is formed from one strip by joining the free ends thereof and the joining region is resilient. This one resilient region is sufficient to fully utilize the advantages of the resilient wheel member in flat sanding.

A particularly simple and therefore advantageous embodiment of the resilient connection provide that an overlapping resilient joining member is attached to inner belt surfaces at said ends. Rubber or plastics can be used as materials for the lap portion. When butt joining the ends of a sanding belt, the joining member is adhesively affixed to the support ply. To ensure a reliable adhesive join, the resilient joining member is provided on the one side with a textile coating, more particularly cotton velour.

Sanding belts which must be constructed so that they can adapt themselves readily to different moulding contours of the sanding wheels are based on the circumferential surfaces of sectioned sanding wheels for sanding moulded surfaces of timber components. In a known sanding belt such adaptation is obtained by the sanding belt having cuts at least along one of its longitudinal sides and the sanding belt is adhesively affixed to the sectional circumferential surface of the sanding wheel. This construction of the sanding belt still has various disadvantages. The number and shape of the cuts in the sanding belt are different for different moulding contours so that production and stock-keeping of the sand belt becomes more expensive.The attachment, more particularly by adhesive joining, of the sanding belt to the moulded circumferential surface of the individual sanding wheels is time-consuming and costly because the many one-sided or two-sided portions of the sanding belt formed by the cuts must be pressed successively and individually in an ordered manner upon the sanding wheel.

Furthermore, there is the disadvantage that the resilient sanding wheel can extend during replacement only until the increasing diameter of the wheel member has reached the width of the surrounding sanding belt.

In conjunction with moulded wheel members, the invention provides that the sanding belt has a support film which is extensible in the longitudinal direction and on which sanding portions with abrasive material, more particularly sanding strips, are mounted.

A sanding belt constructed in this manner bears upon the circumferential mouldings of the sanding wheels without difficulty and over the entire surface when being placed upon the sanding wheels. Such a sanding belt can therefore be equally well employed, without any subsequent working, for a wide range of differently contoured moulded sanding wheels. Special adaptation of the sanding belt to specific mouldings is therefore obviated for the user of the sanding belt. Stockkeeping is reduced.

In a sanding belt of this kind the sanding strips are arranged on the support film at an angle to the longitudinal sides of the support film and are closely mutually adjacent. The inclined arrangement of the sanding strips improves the sanding operation itself. The sanding portions to be mounted on the support film can also have any suitable shape, for example they could be in corrugated strip form. Attaching the sanding portion on the support film is performed advantageously by adhesive joining with adhesives which remain resilient.

Advantageously, the support film is constructed of rubber so as to ensure a high degree of resilience and therefore good adaptability of the sanding belt to different sanding wheel sections.

The support film can also be constructed of resilient plastics material or can be a resilient fabric.

Exemplified embodiments of the invention, disclosing additional inventive features, are illustrated in the accompanying drawings in which: Figure 1 is a section through a sanding wheel with a moulded circumferential surface; Figure 2 is a section through a sanding wheel with a flat circumferential surface; Figure 3 is a diagrammatic side view of the sanding wheel according to Figure 2 during operation; Figure 4 is a partial section through a butt joint of the ends of a sanding belt; Figure 5 is a plan view of a sanding belt comprising a resilient support frame and sanding strips mounted thereon; Figure 6 is an end view of the sanding belt according to Figure 5; Figure 7 shows the sanding belt according to Figure 5 in the stretch state;; Figures 8 and 9 are partial cross-sections through moulded sanding wheel with sanding belts according to Figure 5 disposed in the wheel circumference and Figure 10 is an enlarged plan view of the moulded sanding wheel according to Figure 8 with the sanding belt illustrated in Figure 5 thereon in portions.

The moulding sanding wheel shown in section in Figure 1 is provided with the support bush 1 by means of which it is slid on to a sanding spindle not shown. On one side the support bush 1 is provided with a fixedly disposed flange 1 a. On the other side it is provided with an externally threaded bush portion 1 b on to which an internally threaded collar 2 can be mounted. A wheel member 4 together with two stressing discs 3a and 3b, bearing thereon on both sides, is slid onto the cylindrical portion of the support bush 1 and after being slid thereon said stressing discs are thrust by the mounted collar 2 against the flange 1 a of the support bush and are thus axially retained.

Each of the stressing discs 3a and 3b is provided with inwardly facing retaining pins 7 which project into open bores 8 in the wheel member. The retaining pins are welded to the stressing discs but they can also be riveted or screw-mounted thereon.

The circumferential surface of the wheel member 4 has a circumferential, groove-shaped moulded recess 5. A sanding belt 6 is placed on the moulded recess 5 and on the adjoining regions of the circumferential surface of the wheel member.

Figure 2 shows a section-in schematic form through a sanding wheel with a flat circumferential surface. Identical components have the same reference numerals as those in Figure 1.

The circumferential surface of the wheel member supports a ring bearing thereon and comprising the sanding belt 6.

Figure 3 is a side view of the sanding wheel provided with a sanding belt 6. Identical components have the same reference numerais.

Figure 3 shows a workpiece 1 5 which is sanded flat with a rotating sanding wheel. The rotating motion of the sanding wheel and the feed motion of the workpiece 15 are both indicated by arrows.

Figure 3 indicates that the contact region between the sanding belt 6 and the workpiece 1 5 is superficial and the sanding pressure is therefore distributed over the surface so that burning of the sanding belt is avoided. The sanding performance is again substantially higher, since using the same stress on the sanding belt it is possible to operate with a higher sanding pressure because of the larger contact surface area.

The sanding belt 6 is joined by means of a butt joint 18 at its ends to form an endless ring surrounding the wheel member 4.

Figure 4 shows an enlarged part view in section of the butt joint 1 8. The two ends of the sanding belt comprising a support ply 9 and abrasive particle coating 10 are butted together and are joined to each other by an overlapping resilient joining member 11 of rubber, which is adhesively attached to the inner surface of the support plys 9.

Such an endless sanding belt is able to absorb resiliently changes of diameter. If the wheel member 4 of rubber, which is provided with such a sanding belt, extends as a result of centrifugal forces being applied thereto during rotation, the connecting lap portion 11 of rubber of the sanding belt will be stretched.

A sanding belt 21 for a sanding wheel according to the Figure 1 is shown only partially in Figure 5. It comprises a support film 22 of a high grade rubber which is strong but stretchable.

Narrow sanding strips 23 of emery film, for example of emery cloth, are disposed diagonally, i.e. at an angle to the longitudinal edges of the sanding belt, and are parallel by mutually adjacent.

The sanding strips are adhesively mounted on the support film, more particularly by a resilient adhesive material.

Figure 7 indicates that spaces 24a appear between the sanding strips 23 when the sanding belt 21 is stretched in the longitudinal direction (as indicated by the arrows) owing to the extension of the support film 22. This does not reduce the security of mounting of the sanding strips on the support film.

Figures 8 and 9 show two embodiments, where, in the one embodiment, the sanding belt 21 is placed in a moulded recess 26 in the circumference of the moulding sanding wheel 25a and, in the other embodiment, the sanding belt is placed in semicircular form over the circumference of the moulding sanding wheel 25b. Owing to its longitudinal resilience the sanding belt bears readily and completely on the sectioned circumferential surfaces of the sectioned sanding wheels. This is shown particularly clearly in Figure 10 which is a plan view of the sectional sanding wheel 25a according to Figure 8. The sanding belt, shown in portions only and placed upon the sectioned recess 26 of the moulded sanding wheel 25a while being simultaneously extended, is in this embodiment particularly stretched in the region outside the sectioned recess 26.

Accordingly, spaces 24e are formed between the sanding strips 23 while the sanding strips 23 continue to be situated closely mutually adjacent in the inner region of the sectioned recess 26.

Claims

1. A device for sanding surfaces, more particularly moulded surfaces, of timber components, the device comprising a wheel member consisting of elastomeric material, at least one sanding belt, which at least partially surrounds the circumference of the wheel member, a support bush, on which the wheel member is coaxially mounted, and two stressing discs of metal disposed on the support bush one on each side of the wheel member to grip said wheel member.

2. A device according to claim 1, wherein a flange is provided at one end of the support bush and an internally threaded collar is provided at the other end of said bush, the collar being mounted on an externally threaded bush portion.

3. A device according to claim 1 or 2, wherein a plurality of retaining pins are provided on the stressing discs, the wheel member having a like plurality of bores defined therein, the retaining pins projecting inwardly towards the wheel member and extending inwardly into said bores.

4. A device according to claim 3, wherein said bores are through bores parallel to the axis of rotation of the wheel member, each such bore accommodating at each end thereof a pin of one of said stressing discs, whereby the pins are arranged in coaxial opposed pairs.

5. A device according to any one of claims 1 to 4, wherein the sanding belt is resilient

6. A device according to claim 5, wherein the sanding belt is a single strip with ends which are resiliently joined together.

7. A device according to claim 5 or 6 further comprising an overlapping resilient joining member attached by adhesive to inner belt surfaces at said ends.

8. A device according to claim 7, wherein the resilient joining member is provided on one side with a coating of cotton velour.

9. A device according to any one of claims 5 to 8, wherein the sanding belt comprises a plurality of belt portions which are resiliently joined together.

10. A device according to claim 5, wherein the sanding belt comprises a supporting film resiliently stretchable in the longitudinal direction and sanding portions mounted on said film.

11. A device according to claim 10, wherein the sanding portions are in the form of longitudinal strips disposed on the supporting film at an angle to the longitudinal direction of the supporting film and are closely mutually adjacent.

12. A device for sanding surfaces substantially as herein described with reference to the accompanying drawings.