EP0016782B1

EP0016782B1 - Drum for sanding belt

Info

Publication number: EP0016782B1
Application number: EP19790900663
Authority: EP
Inventors: Edward Harrison Phillips
Original assignee: Mechanical Plastics Corp
Current assignee: Mechanical Plastics Corp
Priority date: 1978-06-07
Filing date: 1980-01-14
Publication date: 1983-06-08
Also published as: DE2965607D1; BR7903626A; JPS555295A; JPS6146274B2; EP0016782A4; WO1980000033A1; EP0016782A1; CA1111255A

Abstract

A drum (10) adapted to be coupled to the chuck (20) of a hand drill for mounting a sanding belt (24) for rotation. The drum (10) is of one-piece construction and has a central, imperforate web (12) integral with flexible flanges (14) on the outer periphery of the web (12). The web (12) and flanges (14) are formed from a resilient material, so that the web (12) can expand or stretch and the flanges (14) can flex under centrifugal force to increase the frictional engagement between the web (12) and flanges (14) and the inner surface of a sanding belt (24) on the drum (10). In one form of the drum (10) the flanges (14) have a pair of continuous ribs (22) at respective side extremities thereof. This drum is adapted for use with a cylindrical sanding belt (24) having a pair of axially spaced annular shoulders (28) on the inner surface thereof, the ribs (22) being adapted to engage the shoulders (28) to prevent axial movement of the belt (24) on the drum (10). Another embodiment of the drum (10) is free of such ribs (22) and is adapted to be used with a sanding belt which may have abrasive on both the inner and outer surfaces thereof.

Description

Rotary drums for sanding belts have been used in the past but, for the most part, they are made up of several parts and require assembly which adds to production costs. Also, a major drawback of drums previously made for this purpose is the relatively short operating life re- quring replacement and adding to the overall cost of sanding operations. Because of these drawbacks a need has arisen for an improved drum for sanding belts wherein the drum is of simple and rugged construction, has a long operating life and can be produced at minimal cost.
One prior art arrangement is shown in US-A-22 21 173. This reference shows a drum for a sanding belt in which a drum body has a central web having a central pin receiving hole, a circular outer periphery and a pair of flanges integral with the web at the outer periphery thereof and projecting laterally from opposed sides of the outer periphery.
The drum shown in this reference is of sponge rubber material and is therefore relatively soft. It is provided with a smooth outer surface either by so casting the rubber or by cementing a peripheral band to the sponge body. In either case this need for a special outer surface complicates the construction of the drum. Furthermore, in addition to a central driving pin, the drum is provided with a central driving hub through which the pin passes. This again complicates the manufacture of the drum because the hub portion requires assembly to the body of the drum.
In order to secure the abrasive band to the drum body the drum body is made fractionally larger than the band so that it has to be compressed to allow mounting of the abrasive band. In operation the abrasive band is held both by the precompression in the sponge rubber material and also by the effects of centrifugal force acting on the yieldable core of the drum.
A further drum for a sanding belt is shown in GB-A-992 300. Here the body of the drum is made of foamed plastic material and is provided with special abrasive strips at its surface which coact with the inner surface of the abrasive band to retain the same on the drum. The body of this drum is, in similar fashion to the drum of US-A-22 21 173 of relatively thick-walled construction and has at most only vestigal flanges. Again a special driving hub is provided which leads to unnecessary complications when manufacturing the drum.
Accordingly the object of the present invention is to provide an improved drum for sanding belts which is of simple and rugged construction, has a long operating life, can be produced at minimal cost and which nevertheless ensures that the abrasive band remains in position on the drum during use.
In order to satisfy this object there is provided, in accordance with the present invention, a drum for a sanding belt in which a drum body has a central web having a central pin-receiving hole, a circular outer periphery, and a pair of flanges integral with the web and projecting laterally from opposed sides of said outer periphery, characterised in that said web has a boss integral therewith and surrounding said central pin receiving hole; in that the drum body is formed from a natural rubber having a hardness in the range of 45-65 Durometer; and in that the web and flanges are of thin wall construction with the radially inner surfaces of the flanges diverging conically away from the web at an angle whereby to permit the flanges to be sufficiently flexible so as to bow radially outwardly due to centrifugal force as the web expands radially outwardly upon rotation of the drum.
Thus it will be seen that the drum body is of a one-piece construction which therefore greatly simplifies manufacture. Furthermore, the web portion of the drum has an integral boss with a central pin receiving hole which ensures that the drive for the drum can be readily transmitted to the drum without having to make the web unduly thick. The use of a natural rubber having a hardness in the range 45-65 Duro- meters for the drum body enables the use of a relatively thin-walled construction which facilitates manufacture and also retention of the abrasive band on the drum. The conically diverging flanges not only simplify the manufacturing process but also assist in the outward bowing of the flanges under centrifugal force which contributes to reliable retention of the abrasive band thus ensuring that the band does not move circumferentially around the drum or axially of the drum when the drum and belt are rotated.
In one embodiment the drum has a pair of annular ribs at the outer side extremities of the two flanges. A sanding belt having a pair of axially spaced inner peripheral shoulders on the inner surface of the belt is used with this type of drum so that the ribs engage the shoulders when the belt is on the drum to prevent axial movement of the belt on the drum.
Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings which show:

Fig. 1 is a perspective view of one embodiment of the sanding drum of the present invention;
Fig. 2 is a vertical section through the drum and illustrating the way in which it is mounted on the chuck of a hand drill;
Fig. 3 is an enlarged fragmentary, cross sectional view of the drum, showing a second embodiment of the drum for use with a sanding belt having abrasive on both the inner and outer surfaces thereof;
Fig. 4 is a view of the sanding belt used with the drum of Fig.3;
Fig. 5 is a view similar to Fig. 3 but showing the drum of Figs. 1 and 2; and
Fig. 6 is a view similar to Fig. 4 but showing a sanding belt of the type used with the drum of Figs. 1, 2 and 5.

A first embodiment of the sanding belt drum of this invention is broadly denoted by the numeral 10 and is shown in Figs. 1, 2 and 5. Drum 10 is formed from a resilient material and comprises a circular, flexible, imperforate central web 12 and a pair of flexible outer peripheral flanges 14 integral with web 12 so that drum 10 is of a one-piece construction. The web and flanges are preferably formed simultaneously in a molding process. The web is of a thin wall construction and, as shown in Figs. 2 and 5, is provided with a pair of bosses 16 at the center thereof for support purposes. The bosses project laterally from opposite sides of the web. While Fig. 5 shows the sides of the web parallel with each other, they could be tapered from the center outwardly with the thinnest part near the outer periphery of the web to provide additional support.
A pin 18 extends through the boss and the web as shown in Fig. 2. Thus, a chuck 20 on a hand drill or the like can grip the pin for rotating drum 10 about the central axis of web 12.
Flanges 14 have cylindrical outer surfaces and project laterally in opposed directions from the outer periphery of web 12 as shown in Figs. 2 and 5. The flanges have respective integral ribs 22 at their outer extremities. These ribs are formed with the flanges in a molding process. The flanges have a thin wall construction and, because they are resilient, they are essentially flexible so as to flex radially outwardly when subjected to centrifugal force. Similarly, web 12, being of a thin wall construction, and formed from a resilient material can expand or stretch radially outwardly under centrifugal force as drum 10 is rotated at high speed, such as 2200 rpm or the like. This assures a positive frictional engagement between the web and the flanges and the inner surface of a sanding belt mounted on the drum for rotation.
For additional holding capabilities, ribs 22 are provided for use with a sanding belt 24 (Fig. 6) which comprises a band 26 provided with annular shoulders 28 on the inner surface thereof at locations spaced inwardly from the opposed sides thereof. These shoulders can be formed by securing a band to the inner surface of band 26 with the inner band having an axial length less than that of band 26.
Shoulders 28 abut ribs 22 in the manner shown in Fig. 5 when band 26 is mounted on flange 14. Thus, a tendency for the belt to move axially of the drum is countered in two ways, first by the frictional engagement between the flange and the inner surface of band 26 and, secondly, by the stop feature provided by the engagement of ribs 22 with shoulders 28.
Drum 10 has the following typical dimensions: Maximum diameter of about 3.80 inches, web thickness of about .25 inch, total axial length of flanges 14 of about 1.40 inches, and angle a (Fig. 3) of about 5°. The radially inner surfaces of the flanges thus diverge conically away from the web at the angle a. The material of drum 10 is typically 55 Durometer natural rubber but can have a hardness in the range of 45-65 Durometer.
In use, pin 18 is secured in the conventional manner to chuck 20 and sanding belt 24 is then placed on the drum and seated on the flanges 14 in the manner shown in Fig. 5. Then the hand drill associated with chuck 20 is actuated to rotate drum 10 and thereby permit the sanding of a surface by the outer surface of band 26 which is provided with an abrasive in the usual manner. During the sanding operation, web 12 will expand radially outwardly and flanges 14 will flex outwardly yet web 12 will generally maintain its disc-like shape since it is rotating in its own plane. There will be no circumferential movement of band 26 relative to flanges 14 during rotation of drum 10 because of the frictional engagement of web 12 and flanges 14 and the inner surface of band 26. Moreover, this frictional engagement plus the stop action afforded by ribs 22 will prevent any substantial axial movement of band 26 relative to flanges 14.
Fig. 3 illustrates another embodiment of drum 10, namely drum 10a. This drum is substantially the same in all respects as drum 10 except that drum 10a has no ribs 22. Instead, drum 10a has a completely cylindrical outer surface and is adapted for use with a sanding band 24a which may have abrasive on both its inner and outer surfaces. Abrasive need not be on the inner surface and, if used, it need not cover the entire inner surface as shown in Fig. 4. If used, however, the abrasive on the inner surface provides greater friction between the drum 10 and the sanding belt. Without the abrasive on the inner surface, there will be sufficient friction between the flange of drum 10a and the inner surface of sanding belt 24a because of the expansion or stretching of the central web of drum 1 Oa and the flexing of outer peripheral flanges due to centrifugal force, thereby causing the web and flanges to be pressed with greater force against the inner surface of the sanding belt to achieve an increased frictional force.
Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be obvious that certain changes and modifications may be practiced within the scope of the appended claims.

Claims

1. A drum (10) for a sanding belt (24; 24a) in which a drum body has a central web (12) having a central pin-receiving hole, a circular outer periphery, and a pair of flanges (14) integral with the web and projecting laterally from opposed sides of said outer periphery, characterised in that said web (12) has a boss (16) integral therewith and surrounding said central pin receiving hole; in that the drum body is formed from a natural rubber having a hardness in the range of 45-65 Durometer; and in that the web (12) and flanges (14) are of thin wall construction with the radially inner surfaces of the flanges diverging conically away from the web at an angle (a) whereby to permit the flanges (14) to be sufficiently flexible so as to bow radially outwardly due to centrifugal force as the web (12) expands radially outwardly upon rotation of the drum (10).

2. A drum as set forth in claim 1 and characterised in that each flange (14) has a projection (22) on the outer side extremity thereof for engaging a respective shoulder (28) on the inner surface of a sanding belt.

3. A drum as set forth in claim 2 and characterised in that the projection (22) on each flange (14) comprises an annular rib.

4. A drum as set forth in any preceding claim and characterised in that said drum has a maximum diameter of about 9.65 cm, in that the thickness of said web is about 0.64 cm, in that the total axial length of said flanges (14) is about 3.56 cm and in that said angle (a) is about 5°.