US3166877A - Abrasive sheet support system - Google Patents

Description

Jan. 26, 1965 REAMES 3,166,877

ABRASIVE SHEET SUPPORT SYSTEM Filed Feb. 18, 1963 INVENTOR LEONARD (J His/W55 BY ML o/v, 5E7 n5 & C 616 ,qrrok/vevs United States Patent 3,166,877. A R S VE SHEET SUPBQR S fiT M Leonard W. Rearnes, Howell, Mich, assignor to Edward J. Sopcalr, Howell, Mich, and Thomas L; Draper, Birmingham, Mich.

Filed Feb. 18, 19 63, Ser. No. 259,276

' 3 Claims, (Ci. 51-378) This invention relates to the abrasive art; and more particularly to a support system for abrasive sheets for use on rotary abrading machines.

The problem In the grinding or dressing of surfaces such as of metal castings, automobile bodies for repainting and the like, the rotary abrasive machine has been found to be particularly desirable. The rotary action tends to render the abrasive self-cleaning by rejecting the material removed from the surface and thus reduces the clogging of the abrasive grit that would otherwise occur.

Early abrasive sheet support systems merely comprised a sheet of abrasive material cemented to a rubber backing disc. However, because the rubber backing disc acted as a heat insulator, early clogging resulted from the fact that paint and other materials removed from a suriace were rendered gummy by the heat and thus caused early clogging thus overriding the advantage of circular action.

One advance in the art provided a ribbed backing member for the abrasive sheetfioatably supported between the abrasive sheet and a rubber drive disc, so that the backing sheet could move relative to the abrasive and thus bring different grains into contact with the work surface upon repeated application of the abrasive thereto. This is set forth in our copending application Serial Number 259,109, filed February 18, 1963, which describes a novel backing disc and its use in the typical prior art mounting system.

However, such typical prior art mounting system as will be hereinafter described was characterized either by:

(a) A substantial number of parts requiring consider- I able dexterity by the Workman in replacing the abrasive sheet when it' wore out; or

(b) Welding parts together to reduce the total number. However, this required discarding the more costly and essential part, namely, the rubber drive disc, when replacingthe backingdisc. ii

Accordingly, an important advance inthe art would be provided by a novelsupport system for rotary abrasive discs characterized by a minimum of parts yet providing for the replacement of the separate elements without discarding any other element.

Objects Accordingly, an important object of the present inven tion is to provide a novel support system for a rotary abrasive disc. t

A further object is to provide a novel support system for a rotary abrasive disc characterized by improved *ease ofassembly and reduced number of Working parts.

A still fr rther object is to provide a nove support system'for a rotary abrasive disc characterized by handling teristic of analogous units of the prior art.

Other objects of this invention will appearin the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

Ilie drawings 1 is a section view .of-a typical rotary abrasive sheet support system of the prior art;

FIGURE 2 is a section View similar to FIGURE 1, but showing a preferred embodiment of the present invention; and

FIGURE 3. is a section view of a second embodiment of the invention.

Before explaining the present invention in detail it is to be understood that the invention is'not limited'in its application to the details of construction and arrangement of parts illustrated in. the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways Also, it is to be understood that the phraseology 9r terminology employed herein is for the purpose of description and not of limitation.

v The environment The environmental surrounding of the present invention comprises an electric motor driven and generally handheld grinder or abrasive machine. Such a machine typically includes a driving motor mounted within a die cast aluminum housing or equivalent. handle or handles are formed on the housing so that an operator can pick up the unit and manipulate it over a surface to be dressed, such as an automobile tender in repairing the same. A drive shaft is journaled in the housing and is suitably geared to the motor. I

The shaft of the machine has an extending stub and this is designated by'the reference numeral 10 in FIG- U E 1 of the d aw n GU E 1 lu t te e know structure which has heretofore-been employed, but' upon which the present invention provides an advance in the art.

A typical prior structure Referring now to FIGURE 1 in further detail, it will be noted that stub 10 is provided-with an axially extending threaded bore 12 to receive a cap screw'14 used to hold the grinding assembly to the end of the stub shaft 10.

The general components of the system It will be noted that a rubber drive washer 16 of substantial body andthickness is provided with a metal insert 1.8 at the center. The insert 13 comprises a tubular sleeve flanged at the top end as at 20. The insert 18 is joined as by vulcanizing in the center hole of the rubber 'drive disc 16. i

It will be noted that the body of the cap screw 14 is inserted through the bore of the insert 18"'for as'seinbly inherent in either of these arrang t wm be a gh hereinafter.

It will be noted that an abrasive sheet 26 of circular form and having an appropriate centerhole is held between the cap 240i js crew 1 4 andthe topside of the spacer 22. w i

The backing disc, one form being disclosedinour copending application Serial Numberi25 9,ll09,'filed;l?ebit ary 18, 19.63, is designated28 and is (if-generally circular configuration. The disc 2 8 hasacenter .hole'sliyvn eby it is fitted "into the "spacer 22.forretentionagainst-ahial movement. 'It mightbe stated that 'the' spacer 22 is flanged over'on one side or'the other after insertion through the center hole 30 .Ot-the disc 2 8 to assemble the parts. It will be noted that thehole fillis slightly larger than the bight of the spacer 22, so that the disc I washer 16 by floating on the spacer 22 in the space between the abrasive sheet 26 and drive washer 16. It will be understood from the foregoing that the sheet 26 and washer 16 move together but can rotate relative to disc From the foregoing it will be understood that when the workman presses the abrasive sheet against a work surface, the drive disc presses against the back of disc 28 on one side and the work presses sheet 26 against the disc on the other side to lock all 3 elements together.

Advantage of this arrangement is that every time a workman lifts the unit .away from the work surface, the backing disc 28 can move slightly relative to the abrasive sheet 26 and the drive disc 16, so that on next contact with the work, different abrasive grain will be forced into contact with the work surface and therefore give the grain previously working, a chance to unload. As discussed above, the backing disc forms a subject of our copending application and therefore a more detailed description is not set forth herein. It is sufiicient to note that the backing disc 28 is provided with radially extending ridges to provide radial lines of contact between the abrasive grit and the work, and these change upon release of pressure as set forth above.

This prior art structure, as will be noted from the foregoing description, could be made according to one of the following optional arrangements:

(A) A drive washer 16, spacer 22 and disc 28, and abrasive sheet 26 can be separately assembled on the cap screw 24. This provided the greatest number of parts, namely, four as follows:

viding one less part, to wit:

(1) Washer 16-spacer 22-disc 28 as a single assembly;

(2) Abrasive sheet 26; and

(3) Cap screw 24,

It will be noted that this arrangement provides a lesser number of parts, thus giving greatest economy of operator time'for changing the abrasive sheet but a distinct disadvantage from a cost standpoint. Thus, because the spacer 22 and drive Washer 16 are an integral unit by spot welding replacement of the backing disc 28 necessarily entails loss of the drive washer 16.

The present" invention provides a distinct advance in the art ovcreach of the foregoing prior art arrangements, and a full description will now be provided.

The inventive embodiment FIGURE 2 In accordance with the present invention, provision is made for changing the abrasive sheet with a minimum disassembly of parts, and the replacement of the backi ing disc without throwing away the rubber drive washer; thus providing in one advanced unit, the advantages of both of the above arrangements of the prior art, but without any of the disadvantages.

' Drive washer 0f FIGURE 2 The present invention embodies a rubber drive washer as described in the prior art; however, because of its different configuration, it will be provided with a different reference number. Thus, in the embodiment of FIG- URE 2, the drive disc is designated by the reference numeral 32. The disc 32 has a larger center hole 34 than 16 previously discussed, to accommodate the larger diameter of the insert 34. The insert 34 has a tubular body portion 36, and an annular base flange 38 having a threaded opening 40 centrally thereof.

Exlcnsion shaft In this embodiment of the invention, as distinguished from the prior art of FIGURE 1, note that an extension shaft 42 is utilized that is provided at its top end with a threaded stud portion 4 that is turned into the thread opening it? of flange .38 of insert 34. The remaining details of this shaft include opposed flats 46 for application of a wrench and a threaded stud portion 48 at the bottom. By the bottom threaded stud 48, the unit can be attached to the stub shaft of an abrasive machine in the manner of FIGURE 1.

To review a bit, it should be pointed out that joinder between insert 34- and the drive washer 32 is made as by vulcanizing.

Note that the interior of the insert 34 is threaded with a known type of locking thread 50.

Disc holder 0) FIGURE 2 An important aspect of the present invention resides in the attachment of the backing disc, designated 28, because the same as previously described. This is effected by means of a disc holder designated by the reference numeral 52 that is threaded into the thread 58 in locking relation.

Disc holder 52 includes a tubular body member 54, externally threaded with a locking thread to lock into the previously mentioned locking thread it). The holder 52 is provided with a top annular flange 56. it will be noted that the exterior thread 55 on body member 54 extends only part way up, so that an annular washer 58 when tightened thereon will be stopped in spaced relation to the top flange 56.

The disc holder 52 is assembled to the backing disc 28 by inserting the body 54 through the center hole 30 of the backing disc and then threading on the annular washer 58 in locking relation. Disassembly of this unit is the reverse. Further assembly comprises threading the bottom exposed portion of the thread 55 into the thread 5th until the washer 58 bottoms on the top flange 60 of insert 34 to provide a locked, assembled relation of parts.

Abrasive sheer retainer 0 FIGURE 2 As shown in the upper portion of FIGURE 2, the abrasive sheet retainer 62 takes the form of what might be described as an internal thread cap screw. Thus, the unit d2 includes a tubular body 64 internally threaded as at 66 whereby it is threaded onto the upper portion of threaded stud 44 of the shaft 42, that was previously threaded through center hole 40 of washer 32.

Final assembly is made by laying the abrasive sheet 26 on top of the backing disc 28 with the center hole aligned, and then inserting and tightening the capped retaincr 62.

Regarding the foregoing embodiment, it is noted that the drive washer 32 and backing sheet disc 28 are dished slightly at the center, so that when final assembly is made, the top flange 68 will lie slightly below the working level of the abrasive sheet as in FIGURE 1, so that only the abrasive grit will contact the work and the top of the cap member 62 therefore does not engage the work to prevent scarring.

Changing abrasive FIGURE 1 From the foregoing, it will be noted that changing the abrasive sheet 26 merely involves removal of the retainer 62; lifting off the sheet; and replacing. The drive washer 32 is never removed, nor is its relationship with the backing disc 28 disturbed.

It will be noted however that if replacement of the backing disc 28 becomes necessary, this can be done very easily by merely removing the disc holder 52; the washer 58; and reassembling. Note that this operation is effected quickly and without loss of the more expensive drive Washer 32.

Thus, a substantial advance in the art is provided.

The inventive embodiment of FIGURE 3 The embodiment of FIGURE 3 utilizes a cap screw in accordance with the prior art; but, like FIGURE 2,

overcomes the disadvantages of the prior art and functions in a manner generally analogous to the embodiment of FIGURE 2.

A complete description of the FIGURE 3 embodiment now follows:

This embodiment of the invention, mounts directly to the end of the stub shaft and utilizes a cap screw 14.

Drive washer of FIGURE 3 Disc holder 0] FIGURE 3 A disc holder, designated by the reference numeral 84, is threaded into the thread 7 6 in locking relation. The disc holder 84 includes an outer tubular body member 86, externally threaded as at 88, with a locking thread to lock to the previously mentioned locking thread 76. This unit is provided with an annular, radial top flange 90. Inside the body 86, there is press fitted and locked against rotary movement, as by splines, a tubular body member 92, having a top flange 94. It will be noted that the flanges 90 and 94 are axially spaced to accommodate the backing disc 28 for rotation in the U-shaped section channel formed therebetween. The unit 84 is threaded into the thread 76 and both exterior body member 86 and interior body member 92 bottom on the base flange 78 to preserve the channel space between 90, 94. Thus the backing disc 28 and the rubber drive washer 70 are an assembled unit for operation, but can be disas- 6 sembled for replacement of the backing 28 should this become necessary.

Assembly of FIGURE 2 To assemble the system for operation to the stub shaft iii, the cap screw 14 is inserted through the hole in the abrasive sheet 26 and then through the disc holder 84 which with attached disc 28, and then through rubber drive washer 7t and then threaded into the bore 12 of the shaft 10. The same principle of operation is provided as in FIGURE 2. Thus, it will be noted that case of abrasive disc replacement is provided and that the backing member 28 can be replaced when necessary with a minimum expenditure of time and without other parts replacement.

What I claim is:

1. A support system for securing a circular abrasive sheet to a threaded shaft comprising an annular drive washer of resilient material, an interiorly threaded insert fixed to said washer at the center thereof, disc holding means including a pair of telescopically assembled axially bored elements having concentric axially spaced flanges defining therebetween an outwardly opening channel, one of said elements being exteriorly threaded for threaded assembly into said insert, a backing disc having a central aperture through which one only of said elements projects to entrap said disc between said flanges with said disc overlying said drive washer, and an abrasive sheet retainer having a radially enlarged flange for confining a central portion of said abrasive sheet against said disc holding means and an axial projection extending through said disc holding means for, threaded engagement with said threaded shaft.

2. A support means as defined in claim 1 wherein the disc holding means includes a first element provided with a top annular flange and an externally threaded body, and a second element in the form of a washer threaded onto the body of the first element, the first element flange and the washer defining an outwardly opening channel therebetween.

3. A support system as defined in claim 1 wherein the disc holding means includes a first element having a peripheral flange and an elongated axial extension and a second element including a peripheral flange and an exteriorly threaded axial extension interiorly bored to receive the extension of the first element therethrough, in sliding relationship therewith.

References Cited in the file of this patent UNITED STATES PATENTS 2,902,799 Beck Sept. 8, 1959

Claims (1)

1. A SUPPORT SYSTEM FOR SECURING A CIRCULAR ABRASIVE SHEET TO A THREADED SHAFT COMPRISING ANANNULAR DRIVE WASHER OF RESILIENT MATERIAL, AN INTERIORLY THREADED INSERT FIXED TO SAID WASHER AT THE CENTER THEREOF, DISC HOLDING MEANS INCLUDING A PAIR OF TELESCOPICALLY ASSEMBLED AXIALLY BORED ELEMENTS HAVING CONCENTRIC AXIALLY SPACED FLANGES DEFINING THEREBETWEEN AN OUTWARDLY OPENING CHANNEL, ONE OF SAID ELEMENTS BEING EXTERIORLY THREADED FOR THREADED ASSEMBLY INTO SAID INSERT, A BACKING DISC HAVING A CENTRAL APERTURE THROUGH WHICH ONE ONLY OF SAID ELEMENTS PROJECTS TO ENTRAP SAID DISC BETWEEN SAID FLANGES WITH SAID DISC OVERLYING SAID DRIVE WASHER, AND AN ABRASIVE SHEET RETAINER HAVING A RADIALLY ENLARGED FLANGE FOR CONFINING A CENTRAL PORTION OF SAID ABRASIVE SHEET AGAINST SAID DISC HOLDING MEANS AND AN AXIAL PROJECTION EXTENDING THROUGH SAID DISC HOLDING MEANS FOR THREADED ENGAGEMENT WITH SAID THREADED SHAFT.

Images