US2199069A - Sanding machine - Google Patents

Description

Aprii'30, 1940. a. F. FOWLER SANDING MACHINE Filed April 28. 1957' 4 Sheets-Sheet 1 IN V EN TOR.

ATTORNE S.

April 30, 1940. FQWLER 2,199,069

- SANDING MACHINE I V Filed April 28, 19:51 4 Sheets-'She et 2 25 J a7 /7 5 J I? 22 J 24 27 I J) 5 55 7 5/ l5 l4 w m """'Y4||v v IN V EN TOR.

A TTO EYS.

April 30, 1940. B. F. FOWLER SANDING MACHINE F'il d April 28, 195'? 4 Sheets-Sheet 5 INVEN TOR.

April 30, 1940- B. F. FOWLER .1 9.0 9

- v SANDING MACHINE Filegi April 28, 1937 4 Sheets-Sheet 4 w v I? A lluk ul 53 1 IN V NToR.

Patented Apr. 30, 194% snares PATENT. orrics 14 Claims.

This invention relates to sanding machines and.

more particularly to portable sanding machines.

Briefly, and in general terms, the invention relates to a portable sanding machine including a body or supporting structure, driving means, a

driving belt,'a sanding belt, driving and driven pulleys, an improved shoe or pressure plate for.

engagement with the inner surface of the driving belt, novel means for yieldingly and universally supporting said shoe, and a novel use and arrangement of auxiliary rollers adapted to guide and support said driving and sanding belts.

The present inventionis susceptible of a great many uses, but is particularly well adapted for use in economically finishing curved or convex surfaces such as are found, for example, on the metal bodies of automobiles.

Portable sanding machines have been used heretofore for finishing automobile bodies to supplant the comparatively crude method of finishing by hand-filling, a method which essential-' 1y increases production costs. However, prior sanding machines have been found to be inemcient because they are constructed with a shoe that is rigidly mounted with respect to the body or supporting structure and the number of practical uses to which such sanding machines might be put is thereby inherently limited.

One disadvantage of the use of the prior sand- 0 ing machines having'a rigid shoeis that it is difflcult to apply a. uniform pressure to the effective working area of the sanding' belt and, therefore, the quality of finish'obtainable is dependent upon the skill with which the operatorapplies the machine. Obviously, the degree of skill required increases with the softness of the surface worked upon. Thus, any uneven application of pressure upon the driving and the sanding belts by means of the rigid shoe results in more rapid removal of material from the surface worked upon at the high pressure points of contact and, hence, a uniformly smooth surface is not easily attainable.

Another disadvantage of the prior rigid-shoe type of sanding machines is that they are not adapted for expeditiously finishing curved. or convex surfaces and, therefore; require still greater skill upon the'part of the operator to make a neat job of such surfaces.

still another disadvantage of the rigid-shoe sanding machines is that, even in the hands of a skillful operator, the care required to produce satisfactory finishes consumes considerable time and such consummation of time increases production costs.

The present invention is designed to overcome the above defects and disadvantages of prior sanding machines by providing a machine which requires a minimum of skill to operate and which is adapted to quickly and expeditiously finish fiat and curved or convex surfaces with equal facility and at low cost. The above desirable results are primarily obtained by constructing a sanding machine with a shoe or pressure plate that is capable of automatically adjusting itself into alignment with the surface being finished. The finishing of convex surfaces is greatly facilitated by the provision of yieldable mounting means for the shoe. Such shoe-mounting .means may be used in combination with relatively rigid, or relatively yieldable, auxiliary rollers. Satisfactory finishes on convex surfaces, and particularly convex surfaces of relatively small radius, can be j obtained by removing, or omitting, the pressure shoe'and the means which yieldably supports the same; With the pressure plate removed, it will be clear that the auxiliary rollers engage and support the driving beltand'its associated sanding belt and permit inwardflexing of said belts I to conform to'the curvature of the surface being finished.

The invention contemplates numerous ways for mounting'the above shoe or pressure plate so that it may universally tilt and align itself relative to the surface being finished, and for the purposes of illustration I have shown three ways for mounting said plate, employing resilient or yieldable springs, a resilient o1" yieldable pad, and fluid or hydraulic means, respectively. Other and equivalent means may obviously be employed to accomplish the same results and it will, there- 3 fore, be understood that the shoe-mounting means disclosed herein are to be considered as illustrative only. It will also be understood that yieldably supported rollers may be used in the forms of the invention in which I have shown fixed rollers, and vice versa.

The principal object of the present invention is to provide a portable sanding machine which is small in size, light in weight, easyto operate or manipulate and capable of doing a greater number of operations inthe art of surface finishing than has been possible with previous devices of the same general class.

Another object of the invention is to provide a sanding machine which can be used to expeditiously and economically finish fiat and curved or convex surfaces.

Another object of the invention is to provide a sanding machine construction in which'the sanding machine construction inwhich the shoe or pressure plate is substantially universally supported and adapted to automaticallyalign itself with the surface being sanded. A still further object of'the invention is to pro vide a shoe or pressure plate for use in portable sanding machines adapted to quickly dissipate the heat generated by the frictional engagement chine of Fig. 1 viewed in a plane indicated by the line 22 of Fig. 1;

Fig. 3 is an enlarged sectional view taken on the line 3-3 of Fig. 2;

Fig. 4 is anelevational view showing another form of means for mounting the shoe or pressure plate upon the supporting frame or body of a portable sanding machine;

Fig. 5 is a sectional view taken on the line 5-5 of Fig. 4;

Fig. 6 is an isometric view showing a heat insulating pad for use with the mounting means shown in Fig. 4;

fig. 7 is an isometric view showing a resilient pad for use with the mounting means shown in Fig. 4; V

Fig. 8 is an isometric view of a shoe or pressure plate which may be used in the embodiments of the invention disclosed in Figs. 1 and 4;

Fig. 9 is an isometric view of a heat insulating spacer designed for use with the shoe-mounting means shown in Fig. 4; a 4

Fig. '10 is a transverse sectional view through the shoe or pressure plate taken on the line Iii-4 t of Fig. l;

Fig. 11 is a detail view of the means provided on the supporting frame for preventing the auxiliary rollers from getting out of alignment with the driving and sanding belts;

Fig. 12 is a diagrammatic view of the form of invention disclosed in Figs. 1, 2 and 3;

Fig. 13 is a diagrammatic view of the form of invention shown in Figs. 1, 2 and 3 but with the shoe or pressure plate omitted tofacilitate finishing of convex surfaces of small radius;

Fig. 14 is a diagrammatic view of the form of the invention shown in Fig. 4 but with the shoe or pressure plate omitted to facilitate finishingof convex surfaces of relatively large radius;

Fig. 15 illustrates a third form of mounting for the shoe which includes fluid means for universally supporting said shoe;

Fig. 16 is a horizontal sectional view taken upon the line I6-l6 of Fig. 15; and

Fig. 17 is a vertical sectional view taken upon the line Ii-J'i of Fig. 1'5. Referring now more particularly to Figs. 1, 2

ing through said extensions.

and 3 of the drawings, the main body or the supporting structure for the various elements comprising the sanding machine constituting the present invention is generally indicated by the numeral I. Said body comprises a motor casing 2 containing a motor, a combined closure plate and bracket 3 secured to one end of said motor casing, and a reduction gear housing 4 secured to the opposite end of said casing. A handle 5 is secured to' the reduction gear. housing I and is adapted to be grippedby one hand of the operator when the machine is in use. A second handle ii, adapted to be gripped by the other hand of the operator, is carried by lateral extensions '1 of the bracket 3. The handle 6 is supported relatively to the extensions 7 by means of a pair of substantially parallel pins 8 pass- Cotter pins 9 extend through the ends of the pins 8 adjacent the extensions 1 and a coil compression spring l0 surrounds each of said pins, said springs being interposed between the extensions 1 and lugs II projecting laterally from the handle 6. With the above in mind, it will be clear from Fig. 2 that the handle 6 may be moved axially with respect to the motor casing 2 by compressing the springs in to facilitate removal of the sanding belt as will be described hereinafter.

A'switch i2 is conveniently located adjacent the handle 6 and is adapted to control the operation of the motor in the casing 2.

Referring now particularly to Fig. 3, the reduction gear housing 4 encloses one end of a motor drive shaft i3. Said drive shaft has a worm 14 secured thereto and a key it for driving said worm M. The worm l6 meshes with a gear l6 which is secured to and driven by a key (not shown) on the drive shaft I? extending transversely of the housing 5. One end of the driven shaft ill has a reduced extension i8 adapted to extend through a ball bearing l9. Said ball hearing is disposed in a recess 20 formed in a side wall 29 of the reduction gear housing 4, and is retained in said recess by a cover or dust cap 22 secured to the'wall M by screws 23. The reduced end it of the shaft ii is prevented from moving longitudinally with respectto said ball hearing by means of a nut 26 threaded upon said end of said shaft. Y

The opposite end of the shaft I! is also provided with a reduced extension adapted to receive a driving pulley .26. Said driving [pulley is maintained in assembled relation with the shaft i? by means of a nut 27 which clamps said driving pulley against a shoulder 28 on said shaft.

The shaft i7 is supported intermediate its reduced ends by a ball bearing 29 seated in a recess 3t formed in a wall 3i of the reduction gear housing t. The outer portion of said ball bearing is provided with a sealing means 32 to prevent foreign matter from gaining access to said ball bearing and oil from escaping'from the housing through said bearing.

The housing 6 has an opening 33 covered by a closure plate 36 secured to said housing by screws 35. Theball bearings I9 and 29 have packing means 36 and 31, respectively, disposed at the inner sides thereof and in engagement with the shaft ll. Thus. the reduction gears l4 and it are disposed in a completely closed housing, and preferably run 'in oil.

The driving pulley 26 is provided with vanes 38 adapted to blow air against the reduction-gear housing t to thereby cool the same. In order to facilitate cooling, said housing is provided with a plurality of cooling fins 39. These fins-are designed to conduct heat from the oil contained in the housing 4 to the exterior of said housing and to thereby dissipate the same by convection to the air and especially such air as is blown against said fins by the vanes 38 of said pulley.

The driving pulley 25 is further provided with radially extending flanges 40 and M adapted to receive between them a driving belt s2, which is preferably made of some elastic material such as rubber, and a sanding belt 43 lying in super posed relationship to said driving belt.

A driven pulley M is rotatably supported upon a shaft 55 journaled in lugs 65 formed integral with the handle 6. Thedriven pulley M is also provided with radially extending flanges t! and 58 adapted to receive between them the driving belt a2 and the sanding belt 43.

The motor casing 2 is provided with a transversely extending rib 39 which terminates in a plate 55. The bracket 3 carries a rib 58 disposed substantiallyparallel to the rib ts and terminating in a plate 52 disposed in substantially the same plane as the plate 5d. 5d, and the rib 5i and the plate 52, each constitute a bracket adapted to support a base member for a pressure plate and/0r auxiliary rollers. As shown in Fig. 2. a base member 53 is secured to the plates 5|! and 52 by screws 5 The base member 53 carries a pair of ears 55 at opposite ends-thereof adapted to receive shafts 55 carrying rollers 51. A depressible shoe or, pressure plate 58 is disposed above the base member 53 and normally engages and supports the inner side of the driving belt 42. The rollers 5'? are arranged at opposite ends of the'shoe 58 and serve as auxiliary supports for the driving belt 62 and the sanding belt 63.

Four pins59 are threaded at one end into said shoe 58; two in a lug 8t formed at each end of said shoe. A resilient compression spring 5i surrounds each of said pins 59 and is disposed between the lugs 50 and the base member 53, There is sufficient clearance between the pins 59 and the apertures in the base member 53 through which they pass to permit lateral and longitudinal; or universal tilting and movement of the shoe 58 relatively to the base member 53. Thus. it will be seen. thatthe shoe 58 may readily tilt and align itself with any surface against which the sanding belt is applied. and further. that said shoe 58 may yield relatively to said surface and move towardthe base member 53 upon ap lication of pressure sufficient to compress the springs 5i. a

In order to take up the excess slack in the driving belt 42, means 62 is provided to maintain said driving belt taut at all times. Said means comprises a stud 65 secured to a boss 55 of the motor casing 2. and a link 5? adapted to be pivotally mounted upon said stud. The link 61 carries an idler pulley 58 which engages an outer face of the driving belt 32. The link t! has one end of a tension spring 69 connected thereto. and

the other end of said spring is connected to the basemember 53. It will be clear from an ins ection of Fig. 2, that the tension spring 69 tends to draw the link 61 and the idler pulley 68 toward the base member 53 and thus applies pressure to the belt 42 to maintain the same taut to prevent slipping thereof. The driving belt 52 and the sanding belt 43 are maintainedrelatively taut by the action of the springs It upon the driven pulley M.

The sanding belt 43 may be readily removed The rib 3d and plate from the pulleys25 and M for replacement or any other purpose by moving the handle 5 toward I the casing 2 thereby compressing the springs l0 and providing sufiicient slack in said sandingbelt to permit the same to be passed over the flanges of said pulleys.

The shoe or pressure plate 58 shown in Fig. 2 is illustrated in. more detail in Fig. 8. Here. the

means devised for cooling the shoe 58 by dissipation of the heat resulting from the friction of the driving belt thereagainst is more clearly shown. It will be seen that the outer face 10 I of said shoe, which intimately or friction'ally env gages the under side ofthe driving belt 42. is provided with a series of angularly disposed grooves ii and 12 extending inwardly from side faces 13 and 14 thereof to a longitudinally extending groove 15 disposed intermediate said side faces.

The inner or under side of said shoe is. provided with a plurality of substantially parallel cooling fins '55 adapted to increase the radiating surface of said shoe. The radiating surface is increased by the provision of vertical recesses ll extending through said shoe between.the fins 16 and into the grooves H and I2. is further increased by the surface of recesses 18 extending through said shoe and into the longitudinal groove 15. The fins 15 may also be provided with apertures 15, as shown in Figs. i, 5 and 6. Thus, it will be seen that the shoe 58 is so made as to present a maximum area .of radiating surface which is conducive to cooler Said radiating surface operation of the shoe and driving belt, and to a longer useful life of said belt.

Heat transfer from the shoe 58 to the remainder of .the machine is materially reduced by spacing the. body of the shoe away from the base member 53 by means of the compression springs ti. While some heat will be conducted to the base members 53 by the pins 59 and the springs hi, the quantity of heat so conducted is prac- 'tically negligible.

While I have shown four pins 59 for substantially universally supporting the. shoe 58, it will be understood that this number is not essential and that any other'number of pins, more or less, which will support the shoe in the manner specified, is contemplated by this invention.

The sanding machine illustrated in F'g. 2 is particularlywell adapted for finishing fiat surfaces, and convex surfaces of a relatively large curvature. In orderto adapt said sanding machine to finish convex surfaces of a smaller radius, it is only necessary to remove the pins 59 so that the shoe 58 may be disassembled to permit greater flexing of the belt inwardly inter mediate the auxiliary rollers 5?. For the purpose of convenience I have diagrammatically illustrated in Figs. 12 and 13, respectively. the two forms which the machine of Fig. 2' ma v take. a

Fig. 12 shows the shoe 58 in position, and Fig. 13 illustrates the same machine with the shoe and its resilient support removed. It will be obvious from the latter figure that the dr vin and sanding belts may readily flex inwardly relatively to the auxiliary rollers 51 to conform to the curvature of the surface being finished thereby.

Referring now to the form of the invention upon a base member 8I adapted to be secured to the body of a sanding machine by means of webs suchas the plates. 58 and 52 shown in Fig. 1.

The rigid, preferably metallic, shoe 58, the body of'insulating material I8, the slab of resilient material 88,'and the base member 8| are maintained in assembled relation by four pins 82 which have one end thereof threaded into the shoe 58' and the opposite end provided with a head 83 which projects below the base member 8|. Since the studs 82 will con-' duct a slight amount of heat from the shoe 58, it is desirable to protect the slab of resilient material 88 from said heat and this 'is accom-- plished by placing an insulating spacer 84 in. the surrounding relationship with said studs at the points where they would otherwise contact said resilient material. Such spacer is specially illustrated in Fig. 9. I

As shown in Fig. 5, the pins 82 may be fitted with considerable clearance in the apertures 85 in the base member 8! through which they pass. Such clearance will obviously permit depression and universal tilting of the shoe 58 relative to the base member 8|. However, in order tov permit a greater degree of relative tilting than could be obtained with plain circular apertures of uniform diameter, the apertures may be beveled at opposite ends thereof as indicated at" 86.

The auxiliary rollers 51? shown in Fig. 4, instead of being mounted in fixed relation to the base member as in Fig. 2, are so mounted that they can move relatively to the body of the machine and also relatively to the shoe 58". In order to permit such movement, the base member BI is provided with two pairs of projecting lugs 81 and 88, respectively, adapted to receive and pivotally support one end of arms 89 and 88, respectively. The arm 88 is pivotally mounted in the lugs 81' by means of a pin 8I., and the arm 98 is pivotally mounted with respect to the lugs 88 by means of a pin 82. The opposite end of the arm 88 carries projections 88 adapted to rotatably support one of the auxiliary rollers 57, and the opposite end of the arm 98 is provided with similar means 88 for supporting the other auxiliary roller.

Plates 85 are secured to each end of the base member 8| by means of screws 88. Each plate 85, as best illustrated in Fig. 11, is provided with a projection 81 adapted to be received in a recess 88 formed in the arm 89. It will be understood that the arm 98 is also provided with a recess 98 adapted to receive a projection 81. The purpose of said projections and recesses is to prevent transverse movement .of the arms 88 and 88 relatively to the plates 85 and the base member 8I. By reason of the. above arrange ment, the auxiliary rollers 51 will at all times be maintained in alignment with the driving belt 42 and the sanding belt 88.

In order to maintain the auxiliary rollers in contact with the driving belt 82, and at the same time to permit yielding of said rollers relatively to the shoe 58", supporting means gen erally designated 88 is provided. Said means comprises four bolts I88, a pair of said bolts being adapted to pass through each of said plates 85 and through one of the arms .88 and 88. One end of said bolts is provided with a head I8I adapted to seat in a substantially semi-spherical .recess I82 formed in the plates 85. The purpose -of a recess of such shape is to permit swiveling of the bolts I88 relatively to the plates 95. The

opposite ends of said bolts I88 are threaded and each bolt is adapted to receive adjusting nuts I83 and washers I84 and I85. The washer I85 I is adapted to engage the under side of the arms and a compression spring I86 is adapted to be mounted upon each of said bolts between the washers I84 and I85.

It will be clear from the above described con-- struction that in finishing'a surface, pressural application of the driving and sanding belts against, said surface at the zone directly in line with one of the auxiliary rollers 51", will cause said roller to move inwardly by reason of the fact that the arm'carrying the same is pivotally mounted and can move inwardly as is obvious from Fig. 4. Upon suchmovement of either of the arms 88 or 88, the bolts I88 will swivel slightly in their sockets I82 and the compression springs I86 will be compressed in accordance with the pressure applied to, or the amount of yield of, said auxiliary rollers. When the machine is withdrawn from the work, the pressure on the belts is relieved and the arm 89 and/or 88 and the associated roller or rollers will be automatically returned to their initial position by theaction of the springs I85.

In order to increase the utility of the form of the invention shown in Fig. 4, the. bolts 82, the shoe 58, the insulating body I8 and the slab of resilient material 88 may be removed from the base member 8| to permit the driving and driven belts to flex inwardly to a comparatively greater degree between the auxiliary rollers 51. Upon removal of the above specified parts, it will be clear that the driving and sanding belts can flex and conform themselves to a convex surface of a relatively large radius, and that upon inward yielding of the auxiliary rollers 51 still larger convex surface can be accommodated.

The embodiment of the invention shown in Fig. 4, but with the shoe 58 and the resilient supporting means therefor removed is diagrammatically illustrated in Fig. 14.

Referring now to Figs. 15, 16 and 17,, which disclose a third means for universally mounting a shoe or pressure plate 58 it will be noted a I base member 8i is shown adapted to be secured to the body of a sanding machine by means of plates such as the plates 58 and 52, illustrated in Fig. 1. tively rigid arms I81 designed to rotatably support auxiliary rollers 51'.

The base member 8| is provided with a laterally extending boss I88 providing a horizontal bore E89 open at one end H8 and reduced and closed at the opposite end thereof as indicated at III. The reduced end III communicates with anguiarly disposed passageways III, each of which passageways opens into a vertical bore II8. As best illustrated in Fig. 16, there are four passageways H2 and four cylindrlcal bores II3. Each of the bores I I8 is adapted to receive a slidable plunger I I 4.

The angular passageways H2 are preferably formed by drilling through the base member ,8I at a point adjacent the lower end of the vertical bores H8. The inner ends of the passageways II2, as has already been stated, open into the reduced bore III, and the outer ends of said passageways are each closed bya plug in the form of a screw II5. i

,The plungers II4, are of such length that they extend beyond the open ends of the vertical bores H3, and preferably terminate in a ball end H6.

The base member 8| carries rela- The periphery of said plungers is packed by I means of a packing element I I1 secured in place by a packing retaining ring I Ill. The ball ends N6 of the plungers H4 are adapted to be received in substantially semi-spherical sockets I I9 formed in lugs I20 depending from the shoe 58 Dust and other foreign material is prevented from settling upon the plungers II! by collapsible diaphragms I2I surrounding each of said plungers: One end of said diaphragms is secured to the packing retaining rings H8 and the opposite end thereof is secured to the lugs I20. the plungers clean, also serve to prevent inadvertent expulsion of the plungers Hi from the bores H3, as when the pressure on the shoe 58 from the tension of the driving belt is relieved, or said belt is removed from the driving and driven pulleys.

It will be clear from the foregoing that with proper clearances, the ball and socket supports for the shoe 58 provide means whereby the shoe 58* can tilt universally, or in other words either longitudinally or transversely or in both directions simultaneously, with respect to the base member 8!. g

The horizontal bore I09 contains a piston I22 having a cup packing I23 secured to one face thereof by a screw I26. The opposite face of said piston is preferably cut away to form a recess I25 adapted to receive one end of a compression spring I26.

The open end MB of the cylindrical bore I'II9 is closed by a hexagonal-shaped cap I27. Said cap is provided with a threaded aperture I28 adapted to receive an adjusting screw I28. One end of said adjusting screw terminates in a .cone- ,shaped cap IZl. Said cap is provided with-a threaded aperture I28 adapted to receive an ad-,

justing screw I29. One end of said adjusting screw terminates in a cone-shaped portion I33 which projects into one end of the compression spring I 2'6; the other end of said spring being seated in the recess I25 of the piston I22. The

opposite end of said adjusting screw, as best shown in Fig. 16, is provided with a slot I3I adapted to receive a screw driver (not shown) for adjusting the'same. A look nut I32 is threaded upon the adjusting screw I29 and is adapted to lock said screw in any desired position of adjustment by Jamming against the cap I21,

The'horizontal bore I09, the reduced extension III thereof, the passageways H2 and the vertical bores IE3 contain a fluid, not shown in the drawings, which is adapted to hydraulically support the plungers M4; the fluid in the bore use being intended to be disposed upon that side of the piston I22 which carries the packing I23. Hence, it will be apparent that the plungers H4 may be adjusted to a desired vertical height in the vertical bores I It by adjusting the position of the piston I22in the horizontal bore I09, and that said piston may be adjusted in said horizontal bore by turning the adjusting screw I29. It will also be apparent that such adjustment is not permanentor inflexible and that the plungers Md may move either up or down in the bores H3 independently of each other and ina more or less resilient manner by reason of the fact,

that the piston I22 is not fixedly adjusted but is backed by a resilient spring I26, the adjusted compression of which may be increased by any fluid forced back and out of the vertical bores I I3 and into the bore M19, as by downward movement of said plunger; or the compression of said Said diaphragms, in addition to keepingspring' may be relievedas by an outward movement, of said plungers.

I By providing spaced pulleys, one of which is resiliently supported by means which tend to exert a force moving the pulleys apart, and passing an endless driving belt 42 around these pulleys, which belt is held out .of it's normal path between the pulleys by an idler roll I58, and a sanding belt 43 which takes the direct path between the pulleys, certain very desirable results are achieved. In sanding machines of the type described which are used in-modern high speed production a serious problem is encountered in the dissipation of heat generated by friction of the sanding belt upon the surface being worked upon and upon the supporting members of the machine. In some cases the heat may be so high that the adhesive used to adhere the abrasive to the belt is softened and the abrasive comes 0d the backing. By providing means for spacing .1"

paratus the driving belt &2 is longer than the sanding or abrasive belt &3 and, due to the action of the idler roll 65, the driving belt engages the driving and driven pulleys it and d6 over a greater part of their circumference than does the sanding belt d3. Thus, the possibility of slipping of the driving pulley 25 may be reduced.

By providing a resilient connection between the handle 5 and-the members which support the driven roller dd the spring It tends to maintain the sanding belt d3 under the proper tension while the idler roll at with its spring support maintains the driving belt 32 under the desired tension. As is clearly seen in Figure 2 the sand ing belt 53 is spaced entirely away from the driv ing belt 2 for substantially the center to center distance between the pulleys 2t and dd on one side of a common center line drawn between these pulleys. By causing the driving and sand-= ing belts to be moved. outwardly away from the common centerline of the pulleys on the opposite side thereof by the universally movable shoe and roller arrangements, the use of the device in finishing curvedor dimcultly accessible surfaces is greatly facilitated.

- While I have shown my invention embodied in several forms, it will be understood that numerous changes may be made therein without departing from the spirit of the invention or from the scope of the annexed claims.

What I claim is:

1. In a surface finishing machine, a body, a belt, pulley means operatively supporting said belt relative to said body, means for driving said pulley means, a supporting shoe adapted to contact said belt and. mounted so that it can tilt transversely with respect to the normal plane of said belt, auxiliary belt supporting rollers and means for supporting saldrollers for independent V supporting roller adjacent said tilting belt contacting means, and a pivoted support for said roller permitting movement of said roller toward and away from said body.

3. A surface finishing machine of the type described including a body, a belt, pulley means operatively supporting said belt relatively to said body, pressure shoe means yieldably supporting said belt intermediate saidpulley means, and auxiliary yieldingly mounted means engaging and supporting said belt adjacent said yieldable pressure shoe.

4. A surface finishing machine of the type described including a body, a belt, pulley means operatively supporting said belt relatively to said body, and a plurality of elements supporting said belt intermediate said pulley means, said elements including spaced apart rollers and a universally movable rigid surfaced pressure shoe between said rollers, the belt engaging portion of said rollers being below at least a portion of the' belt engaging surface of said pressure shoe.

5. A surface finishing machine of the type described including a body, driving and driven pulleys operatively arranged relatively to said body, a belt in engagement with said pulleys, a shoe adapted to be in frictional engagement with said belt, means supporting said'shoe, independently movable brackets supported by said body, and a pair of rollers mounted on said brackets and arranged adjacent the opposite ends of said shoe and constituting auxiliary supporting means for said belt.

6. In a. sanding machine having an endless belt, a pair of spaced pulleys for supporting said belt and a pressure member-adapted to engage the inner surface of said belt, said pressure member being adapted to permit universal movement of the portion of the belt engaged thereby and comprising a rubber or the like body and a rigid face or surface member adapted to contact the belt.

7. In a sanding machine having an endless belt, a pair of spacedpulleys forsupporting said belt and a pressure member adapted to engagecomprising a rubber or the like body, a rigid face or surface member adapted to contact the belt and a heat insulating material member between and means for limiting the movement of each of said rollers toward said belt independently of the other roller.

9. In a sanding machine, a. body, a belt, pulleys engaging said belt and operatively supporting same relative to said body, spaced arms pivotally mounted on said body, rollers carried by said arms, resilient means tending to move said rollers into engagement with the inner surface of said belt, means for limiting the movement of said rollers towardsaid belt and a resiliently supported pressure shoe member between said rollers.

10. In a sanding machine, a body, a belt, pulleys engaging said belt and operatively supporta face finishing beltoverlying said driving belt,

pulley means operatively supporting said driving belt relative to said body, means for driving said pulley means, belt backing-up means adapted to "contact said driving belt and mounted so that it can tilt' transversely to the normal plane of said belt, auxiliary belt supporting rollers, and means for supporting said rollers for independent movement toward and away from said body.

12. A surface finishing machine of the type described including a. body, driving and driven pulleys operatively arranged relative to said body, a driving belt in engagement with said pulleys, a surface finishing belt, a belt supporting shoe adapted to contact said driving belt and arranged for substantially universal tilting movement relative to said driving belt, an auxiliary belt supporting roller adjacent said tilting belt contacting shoe, and a pivoted support for said roller permitting movement of said roller toward and away from said body.

13. In a surface finishing machine of the type described, a body, spaced pulleys supported by said body, means for driving one of said pulleys,

a driving belt in engagement with said pulleys, a surface finishing belt overlying said driving belt, a shoe adapted to be in engagement with.

said driving belt, means supporting said shoe, independently movable brackets supported by said body, and belt engaging means mounted on said brackets and arranged adjacent the opposite ends of said shoe and constituting auxiliary supporting means for said belts.

14. In a surface finishing machine; a body, a

-' belt, pulleys carried by said body engaging said belt and operatively supporting same relative to said body, spaced arms pivotally mounted on said body, belt engaging members carried by said arms, resilient means tending to move said belt engaging means into engagement with the inner surface of said belt, and a resiliently supported pressure shoe member between said belt engaging means.

BERT F. FOWLER.

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