US2693669A

US2693669A - Floating sanding platen

Info

Publication number: US2693669A
Application number: US130619A
Authority: US
Inventors: Richard G Riedesel
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1949-12-02
Filing date: 1949-12-02
Publication date: 1954-11-09
Anticipated expiration: 1971-11-09

Description

1954 R. e. RIEDESEL 2,693,669

FLOATING SANDING PLATE-N FiledDeo. 2, 1949 2,693,669 Patented Nov. 9, 195 4 ice FLOATING SANDING lll ATEN a Application December SerialNo. 130,619

2 Claims. (Cl- 51-141) This invention relates to supports or anvil members or platens for use in backing up or supporting sheet abrasives at the point where the workpiece being abraded contacts the abrasive coated side of the abrasive sheet during an abrading operation.

It is particularly applicable to belt sanding or belt grinding, i. e., to abrading operations in which an abrasive belt or strip is employed, and the invention is accordingly illustrated in the present disclosure in connection with belt sanding apparatus.

A belt sanding apparatus usually comprises an endless abrasive belt mounted on two or more pulleys, and means for continuously driving the belt. Abrading operations with such apparatus may be divided roughly into two classifications, namely, unsupported operations and supported operations. An unsupported operation is where there is no support back of the belt at the point of contact with the work other than the tension of the belt, whereas a supported operation is where there is.

The present invention relates to the latter type of operation, i. e., to supported operations.

In the said supported type of operations there are at least two principal types or classes of supports. One is a roller, wheel or pulley, usually one of the driving or idling pulleys around which the endless belt is mounted, the peripheral surface of the pulley being employed to bear against the work. This is sometimes referred to as a roll or line contact support. The second type of support is a back-up or anvil member which is applied to a span of the belt between two of the pulleys, and it is to this second or back-up type of support that the present invention relates.

Abrasive belt supports or back-ups, of which a common form is the platen type of support, are frequently evaluated in respect to (1) the length of time that the abrasive belt with which the support is being used, remains serviceable, usually referred to as the belt life; (2) the length of time during which the support remains serviceable, i. e., the support life; (3) the amount of material removed by abrasion from the workpiece during a given length of time in an abrading operation, some times called the rate of cut; and (4) the quality of work gone;1 on the workpiece, sometimes called the quality of Heretofore the known platens and other supports have all failed or been deficient in at least one and sometimes in two or even three of the four respects above referred to. The attainment of one quality has been accompanied by the loss of one or more of the other three.

It is accordingly an objective here to provide a support that will at once make substantial progress toward the attainment of satisfaction in all four of the above mentioned features, namely, belt life, support life, rate of cut, and quality of finish. Another objective is to provide a support suitable for use in the edge grinding of glass and similar hard relatively thin objects.

The invention provides a back-up or anvil member in the form of a platen comprising a base, a face plate overlying the base with a layer of resilient material between them, and spring members impelling the face plate toward the base.

Such platens have been found to attain the stated ob- 1ect1ves.

An illustrative platen is described below and illustrated in the accompanying drawings in which:

Figure 1 is a side elevation, partly in section;

Figure 2 is a plan view;

Figure 3 is a bottom elevation; and

Figure 4 is a diagrammatic sketch showing the platen being used in the edge grinding. of glass.

The working face of the platen that bears against the back of the abrasive belt during an abrading operation, is the outer surface 10 of the face plate 'llwhich bears against a layer of sponge rubber*12 which, in turn, bears against the outer surface 13 of abase plate 14. The face plate thus overlies the base plate and is in spaced relation thereto and parallel therewith, with the resilient layer 12 between them. Y

Four studs 15 extend inwardly from the face plate 11 through apertures in the resilient layer 12 and apertures in the base plate 14 to a point beyond the inner surface 16 of the base plate. The studs are free to turn or to move axially in the said apertures.

If desired, the studs may be fixed to the face plate 11. In the illustrated platen however, the face plate is pierced with apertures that register with the said apertures in the resilient layer and the base plate, and the studs are in the form of screws 15 extending therethrough and being free to turn or to move axially therein, with the heads 17 of the screws countersunk and bearing against the outer surface of the face plate.

Each stud is provided with a stud head in the form of a nut 18 that is threaded onto the screw 15. A spiral compression spring 19 surrounds each stud and bears at its outer end against the stud head 18 and at its inner end against the inner surface 16 of the base plate 14, thereby impelling the face plate 11 toward the base plate.

In action, the resilient layer 12 cushions the pressure against the face plate 11. When the pressure is decreased, the resilient layer restores the face plate 11 to its normal position by pressing outwardly against it, but this action is braked or retarded by the springs 19. Thus the recovery is slower than what the resilient layer would normally produce in comparison with its resistance to pressure.

Suitable means for holding or attaching the platen in a belt sanding machine is provided in the form of a sleeve 25 fixed to the base plate 14 and bored to receive a supporting shaft 26.

In use the platen is held by the supporting shaft 26 in an endless abrasive belt grinding machine with the face 10 of the platen adjacent the non-abrasive side of the downwardly moving span of the abrasive belt 29. A workpiece such as a sheet of glass 27, held by hand or resting on a support 28, is pressed against the abrasive side of the belt opposite the platen.

The spring members of the present invention provide numerous advantages.

For example, they keep a tension on the face plate, holding it snug against the force of the resilient layer that lies between the face plate and the base plate, thus minimizing chatter tendencies.

They provide a slower return of the face plate to its normal position after any sudden unevenness in the pressure between the work and the belt, such for example as is frequently caused by the splice in an endless abrasive belt. Thus they may be said to function somewhat in the nature of shock absorbers.

The studs 15 ride in oversize holes. The springs keep the studs from any binding that might otherwise be caused by the accumulation in the holes of abraded particles or by friction of the studs against the sides of the holes. This aids in maintaining the face plate in a continuous floating state.

The springs keep the studs from working out of the face to cause belt snagging.

The shock absorbing function of the springs prevents premature mineral breakdown on the belt, thus helping to lengthen the belt life.

Although particularly useful in the edge grinding of glass, platens made according to this invention are also useful in surface grinding operations.

I claim:

1. A sanding platen comprising a base plate having an inner and an outer surface, a face plate overlying the outer surface of the base plate, the face plate being in spaced relation to the base plate and parallel with the base plate, the outer surface of the face plate providing the working surface of the platen, a layer of resilient material between the base plate and the face plate, a plurality of apertures extending through the base plate and the layer of resilient material, a plurality of studs extending inwardly from the face plate through the said apertures to a point beyond the inner surface of the base plate, each stud having a head at its inner end, and spiral springs surrounding the respective studs and compressed between the stud heads and the inner surface of the base plate to impel the face plate toward the base plate.

2. The sanding platen of claim 1 in which the face plate is provided with apertures that register with the apertures in the base plate and the layer of resilient material, and in which the studs are screws and the stud heads are nuts turned onto the screws,

the screws being 15 2,279,782

free to turn and to move axially in the apertures, and the sclzrew heads bearing against the outer surface of the face p ate.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 804,902 Tyden Nov. 21, 1905 829,191 Yarnell Aug. 21, 1906 l,030,473 Kroeze June 25, 1912 1,825,883 Moore Oct. 6, 1931 1,986,521 Oakley Jan. 1, 1935 2,272,273 Parker Feb. 10, 1942 Fowler Apr. 14, 1942