BACKGROUND OF THE INVENTION 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, requiring 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.

SUMMARY OF THE INVENTION

The present invention satisfies the aforesaid need by providing a drum of a one-piece construction. The drum is formed from a moldable, resilient material which has a long useful operating life and does would not need replace¬ ment except at relatively infrequent intervals.

To this end, the drum comprises a central, imper- forate web integral with a pair of outer peripheral flanges provided with a cylindrical outer surface. The drum is formed from a resilient material, such as natural rubber, so that, when the drum is rotated at a high speed, the web will expand or stretch radially outwardly and the flanges will flex radially outwardly under centrifugal force. This will cause the web and flange to press firmly against the inner

surface of a sanding belt on the drum to enhance the fric- tional engagement therebetween. This feature assures that the sanding belt will not move circu ferentially of the flange or axially of the drum itself when the drum and belt are rotated.

One embodiment of the drum uses a pair of annular ribs at the outer side extremities of respective 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. A second embodiment of the drum has a cylindrical outer surface for the flanges with the surface being free of the ribs of the first embodi- ment. In this case, the drum is used with a sanding belt which may have abrasive on its inner surface as well as its outer surfaces. If the abrasive is used on the inner sur¬ face, it frictionally engages the cylindrical outer surface of the web and flanges to increase the friction engagement therebetween. However, the abrasive is not needed on the inner surface for this purpose.

The primary object of this invention is to provide an improved drum for a sanding belt wherein the drum is of a moldable material, is of a simple and rugged one-piece construction, and can be made at minimal cost yet the drum has superior holding power to retain a sanding belt thereon even when operating at high rotational speeds.

Another object of this invention is to provide a drum of the type described wherein the drum is formed from a resilient material and has a central, expandable web inte¬ gral with a pair of outer peripheral flexible flanges pro¬ vided with a cylindrical outer surface, whereby the web will expand and the flanges will flex radially outwardly due to centrifugal force to frictionally engage the inner surface of a sanding belt to thereby substantially eliri-inate cir¬ cumferential and axial movement of the belt on the drum. Other objects of this invention will become

apparent as the following specification progresses, refer¬ ences being had to the accompanying drawing for an illus¬ tration of the invention.

IN THE DRAWING:

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 re- silient material and comprises a circular, flexible, i - perforate 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.

-BUR TΓ

OMPI

.A A.. W1P0 _Λ

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 J.0 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. 5) of about 5°. The material

ISU E

OMPI

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 circumferencial movement of band 26 rela¬ tive 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. Abra¬ sive 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 10a 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 des¬ cribed in some detail by way of illustration and example for purposes of clarity of undering, it will be obvious that certain changes and modifications may be practiced within the scope of the appended claims.

^J