US1492659A - Rubbing machine - Google Patents

Description

May 6 1924. 1,492,659

s. F. ANDERSON RUBBING MACHINE Filed Sept. 4. 1917 4 Sheets-Shet 1 May 6 1 924. 1,492,659-

\ S.F.ANDERSON RUBBING MACHINE Filed Sept. 4,'1917 4 Sheets-Sheet 2 S. F. ANDERSON RUBBING MACHINE Filed Sept. 4., 1917 4 Sheets-Sheet 5 May 6 1924. 1,492,659

4 s.. F. ANDERSON RUBBING MACHINE Fil ed Sept. 4, 1917 4 Sheets-Sheet 4 Patented May 6, 1924.

SWAN F. ANDERSON, OF ROCKFORD, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

C. PAUL PARKER, TRUSTEE, OF CHICAGO, ILLINOIS.

RUBBING MACHINE.

Application filed September 4, 1917. Serial No. 189,563.

To all whom it may concern:

Be it known that I, SWAN F. ANDERSON, a citizen of the United States, residing at Rockford, in the county of WVinnebago and State of Illinois, have invented certain new and useful Improvements in Rubbing Machines, of which the following is a specification.

This invention relates to portable pneumatically operated rubbing machines adapted for polishing, burnishing, sanding or similarly treating with abrasive means, flat surfaces to be finished in the manufacture of pianos, metal and wood furniture, etc. Such a machine is exemplified by the provision of a body containing pneumatically operated mechanism for rapidly reciprocating in o-pposit-e directions a pair of rubbing elements which support the body and rest on the surface to be rubbed, the machine being easily movable or slidable about on the surface by hand operation.

Machines of this character heretofore provided become in a comparatively short time worn to such an extent that many parts must be replaced, or that the machines must in fact be entirely rebuilt. This wear is due in part to the grinding or wearing action of the finely divided pumice or other particles which are present as a consequence of the polishing operation, and which work into the operating parts. In many instances, the

exhaust air is passed through the operating parts, with the result that the suspended foreign particles in the air are also unavoidably ground into the wearing surfaces. The moving parts of prior rubbing machines are also often complicated in design sothat considerable wear thereof results due to the high speed at which they must operate.

In the present invention I have aimed primarily to provide a machine of this character which will practically and efficiently serve the purpose desired and will possess assured durability and longevity under the most severe conditions of usage.

These general objects I have attained by the provision of a rubbing machine of generally improved construction, the various novel features of which will be fully described hereinafter. However, it might be here mentioned that I have designed to pro-- vide improved slides or pad holders Whereby large and substantial bearing surfaces are obtained with minimum weight and size of the parts, this being enabled partly by reason of the telescoping relation of the slides, and to provide an improved closed guideway structure for said slides with means for utilizing the exhaust air to keep foreign particles out of the working parts. Certain features of the construction disclosed in this application, such as an improved oscillating valve actuated by an equalizing member which in turn is directly connected with a pair of pistons and maintains the latter in operative relation, the pistons being directly connected with the slides or pad-holders so that the force is applied in a most direct and efficient manner, are covered in a divisional application, Serial No. 401,232, filed August 4, 1920.

Other objects and attendant advantages will be readily appreciated as the invention becomes better understood by reference to the following description when considered in connection with the accompanying drawings; in which- Figure 1 is a side elevation of a rubbing machine embodying my improvements, the rubbing elements being in neutral position;

2 is a longitudinal vertical sectional View taken centrally through the machine with the right hand pad holder removed;

Fig. 3 is an end view of the cylinder and slide body with the end plate removed;

Fig. 4 is a face view of the removed end plate;

Figs. .5 and 6 are horizontal sectional views taken substantially on the lines 55 and 66, respectively, of Fig. 2;

Figs. 7 and 8 are cross sectional views taken substantially on the lines of 77-and 88, respectively, of Fig. 2;

Figs. 9 and 10 are detail perspective views of the piston equalizing member and its bridge supporting member, respectively;

11 is a vertical sectional and perspective view of the oscillating valve;

Fig. 12 is a perspective view in section of one of the pitsons;

Fig. 13 is a perspective view of one of the slides and pad holders, and Fig. 14 shows a guide pivot which serves to connect the equalizer With the slide Fig. 15 is a horizontal sectional view taken substantially on the line of 15-15 of Fig. 2;

ig. 16 is a similar sectional view but showlng the valve actuated from neutral to an operative position; and

Fig. 17 is a horizontal sectional view similar to Fig. 5 showing the pistons disposed in accordance with the position of the valve shown in Fig. 16.

The body of my improved rubbing and burnishing machine comprises two general portions, namely:a cylinder containing portion and a slideway portion designated in general by reference characters 21 and 22, respectively. The body is preferably so shaped that the metal incorporated in its structure gives the machine the weight requisite to increase the eflect of the abrasive means and facilitate the operation. Suitable means may be employed such as bolts 20, for securing the body portions rigidly together. The body portion 21 contains two cylinders 23 and 24 arranged in parallel relation and extending entirely through the body. Provision is made centrally between the ends of the body for the disposal of operating parts, by coring out this portion, as indicated, to form the chamber 25 which, it will be noted, intersects the central portion of the cylinders and in fact divides each cylinder into a double or opposed cylinder. Pistons 26 and 27 slidable in the cylinders 23 and 24 respectively are of the double acting type adapted to take air pressure at both ends. The construction of the pistons and the means by which they are pneumatically operated will be described later on following a description of the slides and pad holders which are operated directly by the pistons.

Assuming now that the pistons are adapted to be reciprocated rapidly in opposite directions, I have made provision for connecting a burnishing pad or rubbing tool as directly as possible to each piston in order that the power may be applied in a most eflicient manner. In so doing, however, due

regard must be had to the fact that because of the high speed at which the parts reciprocate, wearing surfaces or guide ways of large area must be provided which will mount the pad holders in a very substantial manner and which will also eliminate as much as possible the ingress of foreign matter or particles of pumice, etc, into the .operating parts during usage. I have, therefore, provided slides of novel construction and arrangement connected directly to the pistons and adapted for the attachment thereto of pad holders beneath the body. These slides, designated generally by reference characters 28 and 29, are constructed to provide maximum bearing surface in a limited s ace and minimum weight of parts. To this end each slide comprises a central upright portion 31 slidably engaged in a central slotway or guideway 32 extending throughout the length of the body 22 and in reality dividing the latter into two separate side portions, and latterly projecting slides 33- and 34 in ofi'set planes as illustrated clearly in Fig. 13. The portions 31, 33 and 34 slidably engage in correspondingly shaped ways in the body portion of the tool and by reason of the substantial length of these surfaces or portions a considerable area of bearing surface is provided. Referring to Figs. 6 and 13 it will be noted that the lateral slide portion or wing 34 of the slide 29 is of a length nearly equal to the length of its respective piston, while the opposite lateral wing 33 is only about half the length of the wing 34. It will also be noted that by reason of this construction it is possible to arrange the slides 28 and 29 so that they are in overlapping or telescoping relation, making it possible to obtain the relatively long bearing surface desired. In order to further guide the sides against lateral displacement the outer end of each wing portion 34 is provided with a depending flange 35 which fits in a correspondingly shaped groove or way in the body portion 22. In further reference to the telescoping relation of the slides 28 and 29 it will be noted that each slide has a relatively long wing portion 34 on a separate side of the central slotway 32, which portion 34 bears on its upper surface against the under surface of the cylinder body portion 21, and that each slide has an opposite wing-portion 33 of shorter length disposed in a'plane below that of its wing portion 34 and consequently operating in spaced relation below the wing portion 34 of its opposite slide. This will be observed particularly by reference to Figure 8, which shows the wing portion 33 of the slide 29 disposed below the wing portion 34 of the slide 28. In constructing the body portion 22 to accommodate the slides just described I have in the present instance, formed each side of this body portion of two parts 37 and. 38 suitably and. rigidly secured together and shaped so as to provide the proper slideways for the lateral wings of both slides. I do not, however, wish to limit the invention to this particular construction or to the particular construction of the slides since these might be constructed and arranged difi'erently without departing from the general principles I have in mind. The direct connection spoken of between each slide and its respective piston is clearly illustrated in Figs. 8 and 13 from which it will be observed that each slide is provided with an integral upstanding trunnion 39 fittingly engaged in the aperture 41 in its respective piston centrally between the ends thereof. The central portion '31 of each slide is shaped beneath the machine body for attachment to the pad holder which carries the burnishing pad or other abrasive means employed in the rubbing operation. From the foregoing it will be manifest that the air pressure applied to both ends of the pistons (in a manner to be described hereinafter) will reciprocate the pistons rapidly in opposite directions and the pistons will in turn directly reciprocate the slides which carry the burnishing elements now to be described.

In machines of this character; various abrading elements are employed as the rubbing agent and are attached to what is known as pad holders in turn secured to slides. For general burnishing and polishing purposes thick felt pads are'secured to the slides and serve as the rubbing agent, and pumice or the like is applied to the work to be operated on by the pads. It is this type of pad holder that I have illustrated in the present instance although when sand paper, emery cloth or other abrasive materials are used the holder means would be especially adapted for the kind of abrasive used. It should therefore be understood that the" term pad holder is used means employed for securing the abrasive or rubbing member to the reciprocating member. Referring now to the particular pad holder illustrated in the drawings and constituting a part of the present improvements it will be seen that each slide is shaped to provide below the machine body, flat out standing attaching portions 42 in close proximity to the underside ofthelb'ody and shaped at their extremities to receive the pad holders and fastening means for securing the latter to the slides. Each pad holder consists of a flat backing 43 provided with integral upstanding lugs 44 which engage opposite ends of the attaching portions 42 and are secured thereto by means of bolts 45 passing through the lugs 44 and said portions 42. To the face of each backing 43. is secured felt pads. My invention contemplates securing the felt pads to the backing of the pad holder in a novel manner so that the pads need not be larger than their working area or face and so that the rubbing pad may be used until worn very thin before it is necessary to substitute a new pad therefor. To this end a felt pad 46 positioned against the face of the backing 43 and serving as a cushion, shown in Fig. 7, is provided with apertures 47, and a rubbing pad 48 positioned on the face of the cushion pad is provided with small apertures in ali ment with the opening 47 to receive the astening screws 49. By reason of this construction the fastening screws which in reality constitute headed fastening members, will draw the portions of the rubbing pad surrounding the screws into the tapered openings, thereby rigidly securing the rubbing pad to the pad holder and at the same time allowing the heads of the screws to. be drawn inwardly from the face of the rubbing pads a substantial distance. Thus ing certain quite serious deficiencies in machines previously marketed. I have aimed primarily toward simplicity in construction and durability. At the same time I have concluded, after a long series of experimentation, that the various operating parts must be properly balanced and equalized so that there will be no vibration, that the forces be applied as directly as possible and not be transmitted through any needless movements, that because of the high speed at which the parts operate maximum bearing surfaces shall be provided in all instances, and that special provision must be made for preventing any foreign matter aside from the proper lubricants, from entering the operating mechanism and consequently scor ing and impairing the bearings. I have therefore devised a novel means for maintaining the pistons in proper cooperative relation, a novel valve mechanism, and a novel means for utilizing the exhaust air to prevent the entrance of foreign particles to the operating parts, without passing the exhaust air therethrough. The means employed in the present instance for maintaining the pistons in proper relative relation at all times consists of an equalizer designated generally by character 51, shown in detail in Fig. 9, having a cross head 52 secured to a central trunnion or pivot stud 53 which is rotatably positioned in the bore 54 of a bridge member 55 which spans the chamber 25 intermediate the two pistons and is suitably secured to thebody 21 by means of machine screws '56. The ends of the cross head or equalizer 52 slidably cooperate with the pistons through the agency of slotted guides 57 having pivots 58 rotatable within the studs 39 of the slides 28 and 29. By reason of this construction the pistons will be positively held in cooperative relation when reciprocated and the construction is very substantial, yet simple. To prevent interference between the equalizer arms and pistons the latter are cut away as at 59. They are also bored out or hollowed to reduce weight and momentum and are cut away centrally at their inner sides 61 so as downward axial displacement.

to enable proper mounting of the equalizer intermediate the pistons. The oscillatory valve illustrated in detail in Fig. 11 is adapted to be actuated directly by the equalizing member 51 and consists of a cylindrical portion 62 having a diametrical slotway in its lower end which receives the equalizing member. The valve is revolvable in a bushing 63 fixed in the body 21 in axial alignment with the equalizer and is provided with an annular head 64 seated on top of the bushing so as to maintain the valve against A steel washer 65 may be interposed between the bushing 63 and the head 64 of the valve to serve as a proper seat therefor; Air under pressure is supplied to the machine from a suitable source through a handle 66 suitably secured to the body 21 in axial alignment with the valve andhaving an air passage 67 communicating therewith. The air passes downwardly through the passages 68 and 69 '(Fig. 11) in the valve and is adapted to be communicated with the passages 71, 72, 73 and 74 at proper intervals as determined by oscillation of the valve for moving the pistons back and forth. It will be noted that the passages 68 and 69 in the valve intersect its periphery at diametrically'opposite points and are adapted to register with the ports in the bushing which communicate with the air inlet passages 71 to'74 inclusive. As indicated in Figs. 3 and 16 the air inlet passages communicate with the ends of the cylinders. The valve ports, coplanar with the air intake passages and ports, include exhaust ports 75 and 76 adapted to register at proper intervals with both the ports of the intake passages mentioned and the exhaust passages 7 7 and 78 disposed intermediate theair intake passages. These exhaust passages communicate, as shown in Figs. 2 and 16, with passages 79 formed in end plates 81 which entirely cover the ends of the body portions 21 and 22 and consequently close the ends of the cylinders. The ends 81 may be suitably secured to the body by machine screws or the like passing through openings 82. The upright passages 79 in the end plates communicate at their lower ends through openings 83 (Fig.4) with openin s 8& arranged from end to end in the b0 y portions 38 in close proximity to and flanking both sides of the central slotway 32. These openings are restricted at their under sides to provide narrow months 85 coextensive with the length of the slotway 32 and through which the exhaust air may be forced downwardly for the purpose of preventing foreign matter from entering the slotway and working upwardly into the operating mechanism, as will be mentioned herein- 2 after. Referring a ain to the valve it will be noted,-viewing igs. 5 and 17 that there is provision made in the connection between any movement of the valve for a purpose presently mentioned. A splash guard 86 underlying the machine throughout the length thereof intermediate the depending pad fasteners and in close proximity to the arms 42 of the slides, is secured at its ends to the end plates 81. This guard prevents water and pumice from splashing upwardly into the slot wa of 32 and also cooperates, as will be descri ed hereinafter, with the exhaust air in keeping the mechanism free from foreign matter. i

A flushing attachment is employed in connection with the machine for the purpose of supplying water to the Work as may be required at different intervals to mix with the pumice. I have designed to arranged the flushing hose in such manner that it will not interfere with manipulation of the machine and also so that it may be attached in a very simple manner and may be conveniently operated at will to secure the desired supply of water. To this end I have arranged the fiushing hose 87 within the periphery of the handle 66 by, providing a longitudinal channel 88 therein as noted in Figs. 1 and 8 for the reception of the hose and have further grooved the machine body as at 89 and 91 so that the hose may be disposed substantially within the body so as not to present an obstruction at the side of the machine. A spring pressed check lever 92 is arranged to constantly pinch the hose and close the water passage, it being obvious that the operator, by simply pressing inwardly on the outer end of lever 92 may release the hose and allow the water to be supplied in either small or large quantities.

The mouth of the hose by being located-centrally between the rubbing pads applies the Water at the immediate point of usage. By. reason of this attachment the operation is greatly facilitated since the operator may work swiftly without being inconvenienced by a cumbersome flushing attachment and the water may he immediately applied in such quantities as may be desired without detracting from the operators attention in manipulating the machine.

The operation of my improved rubbing and burnishing machine will now be described. In all of the assembled views in the drawings, except Figs. 16 and 17, the parts are shown in neutral position-that is, one in which the air under pressure admitted to the-machine will not actuate the pistons until-the valve has been moved slightly beyond a dead center position. This ma be done by moving the slides or the pad elders. In the neutral position it will be noted that the pistons 26 and 27 are both centrally disposed in their respective cylinders, as shown in Fig. 5, .and that the valve as shown in Fig. 15, precludes the air under pressure from entering the cylinders. Upon moving the slides in either direction the valve will be oscillated through the agency of the equalizing member 51 as described above, so that the passages 68 and 69 of the valve will register with either thecylinder air passages 71 and 74 or the passages 7 2 and 73, dependent upon the direction in which the valve is oscillated. As shown in Figs. 16 and 17 the valve has been oscillated in a clockwise direction, thus communicating the air supply with the passages 71 and 7 4 and consequently admitting the air to the lower left hand piston and upper right hand piston shown in Fig. 17, whereupon the pistons will be forced by the air pressure in the direction indicated by the arrows. The piston action is very rapid and in order that the stroke may be accomplished before the valve changes the air supply ports to the cylinders to effect the reverse piston action, a lost motion is provided between the valve and the equalizer 51 to permit the pistons to more independently of the valve and acquire suflicient momentum to carry them to the end of their stroke before the valve is oscillated to admit the reverse air supply. This will be plainly seen by reference to Fig. 17 from which it will be noted that the pistons may move nearly half the length of their stroke before the valve will be oscillated by the equalizing member 51 in a counter-clockwise direction. While cylinders are taking air through the intake passages 71 and 74 as just mentioned, the opposed supply passages 72 and 73 will be connected thru the valve ports 75 and 76 with the exhaust passages 77 and 78 respectively, so that as the pistons are driven in one direction the exhaust air of the opposed cylinders will be simultaneously expelled from their respective cylinders and forced down through the passages 79 and out of the long narrow months 85 at the under side of the machine. The valve action just described takes place automatically, that is, reverses automatically, due to the alternating action of the opposed cylinders. As a consequence of this action the pistons will reciprocate very rapidly at a speed dependent, of course, on the air pressure and upon the resistance to the rubbing tools due to the nature of the work being performed. In view of the rapidity of this operation the exhaust air will be substantially continuous and, consequently, will be forced into the openings 84 from both ends and discharged downwardly through the narrow mouths 85 throughout the length of the machine. This downwardly discharging exhaust air will strike the top of the splash guard 86 and will be deflected laterally with suchforce very eflfectual means is provided for keeping the operating mechanism clean and in good working condition; and in this regard it will be especially noted that the exhaust air is not passed through the operating mechanism such as through the slide bearings, etc., but is conveyed in passages entirely separate from these and is then applied at the desired points of use. Consequently, the bearing surfaces are not continually subjected to the blast of exhaust air and there is no danger of foreign particles being carried into the slotway in this manner.

It is believed that the foregoing conveys a clear understanding of the principles and objects of the invention prefaced before, and attention is called to the compact arrangement and simplicity of parts in accomplishing the desired ends and the relatively large bearing surfaces afforded and the manner in which all parts are counterbalanced in action so that there is no vibration such as might affect ease and accuracy of the work. It should be understood that while I have illustrated one practical working embodiment of my improvements various changes might be made in the construction and arrangement of parts without departing from the spirit and scope of the invention as expressed in the appended claims.

I claim:

1. In a rubbing machine of the character described, a pad holder slide consisting of a central slide portion, guides extending laterally from the central portion in opposite directions and in different planes one above pair of pad holders or the like, comprising a pair of slides each having a central slide portion and guides extending laterally therefrom in opposite directions in different planes one above the other and arranged so that the upper lateral guide of each slide is in over-lapping or telescoping relation to the lower guide of the other slide.

3. In a rubbing machine of the character described, a body having an inclosed guideway and a narrow slotway extending therefrom to the exterior of the body, a pair of pad holder slides reciprocable upon said guideway and extending through said slotway, pad holders beneath the body attache to said extending portions of the slides, and means within the body for reciprocating the slides in opposite directions, the slides being constructed within the body to have a slide bearing one on the other.

4. In a rubbing machine of the character described, a body having an inclosed guideway and a longitudinal narrow slotway extending downwardly from said guideway to the underside of the body, a pair of pad holder slides each having a narrow central portion extending through said slotway and aving guides extending laterally from opposite sides of its central slide portion, the entire upper surface of the slides having a slide bearing on bottom surfaces of the inclosed guideway, pad holding devices beneath the body attached to the extended ends of the central slide portions, and means withing the body for reciprocating the slides.

5. In a rubbing machine of the character described, the combination of a body, reciprocable rubbing elements and pneumatically operated mechanism therefor on the body, a handle attached to the body by means of which the latter may be manipulated, said handle having an air passage, and a liquid .passage substantially within its periphery,

and connections between the air passage and pneumatically o erated mechanism and between the liqui passage and a point in proximity to the rubbing elements through which latter passage liquid is supplied to the active working faces of the rubbing elements.

6. In a pneumatically operated rubbing machine, the combination of a body, a rubbing element dis osed beneath and supporting the body an mounted for reciprocation thereon, pneumatically operated means on the body for reciprocating said rubbing element, the machine being so constructed that access to the means for reciprocating the rubbing element is had only through an opening provided for reciprocation of the rubbing element, means for delivering the exhaust air from the pneumatically operated means downwardly from mouths alongside of and substantially throughout the length of said opening for preventing foreign matter from entering said opening, and means for defleeting said downwardly directed air to prevent it from striking the working face of the rubbing element.

7 In a rubbing machine of the character described, the combination of a bodv, a plurality of rubbin elements reciprocably guided within the ody and extending below the same, operating means carried by the body and connected with the rubbing ele-. ments for reciprocating the same, means for directing air under pressure downwardly from mouths alongside and substantially throughout the length of the ways of the rubblng elements to prevent foreign matter from entering said ways, and means for defleeting said downwardly directed air laterally to prevent such air from striking the working faces of the rubbing elements.

8. In a rubbing machine of the character described, the combination of a body having a vertical longitudinal slotway intersecting the bottom of the body, a rubbing element disposed beneath the bod and having an upstanding part reciproca le lengthwise of the body in said slotway, air delivery mouths at both sides of the slotway and extending substantially throughout the length thereof and through which air is delivered downwardly and inwardly to prevent foreign matter from entering the slotway, and means for deflecting said air outwardly to prevent it from striking the working face of the rubbing tool.

9. In a pneumatic rubbing machine of the character described, the combination of a frame, a plurality of rubbing elements mounted for reciprocation in a common longitudinal way on the frame, means for directing air under pressure downwardly and inwardly from points flanking the sides of said way to prevent foreign matter from entering the way, and means for deflecting said air outwardly to prevent it from striking the working faces of the rubbing elements.

10. In a rubbing machine, the combination of a main body carrying means for reciprocating a pair of pad holder slides and carrying a bottom bearing surface for said slides, a pair of pad holder slides having top bearing surfaces slidable upon the bottom bearing surface of the body, a slideretaining structure detachably secured to the body so as to inclose said slide bearing surfaces and prevent displacement of the slides with respect to said surface, and air passages in said slide-retaining structure through which air is delivered into the path of the reciprocating slides and outwardly from the body for preventing, foreign'matter from working into the inclosed slide surfaces.

11. In a rubbing machine of the character described, the combination of a main bod carrying means for operating pad hol er slides and carrying a-bottom slide bearing surface, a sectional slide retaining structure beneath said body and comprising side body sections detachably secured to the main body, said side bodies being shaped to provide an inclosed slide compartment immediately beneath said slide bearing surface and spaced apart to provide a way connecting said compartment with with the bottom of the sectional structure, a plurality of pad holder slides. extending through said way and having slide portions slidable upon the bottom and each side body section having an air passage in proximity to said way extending substantially from end to end thereof and through which air may be discharged downwardly and into the path of the reciprocating slides bearing surface of the main body.

12. In a pneumatic'rubbing machine of the character described, the combination of a cylinder body, the bottom of which carries a slide bearing surface, a sectional slide retaining body beneath said cylinder body and detachably secured thereto, said sectional body comprising two side sections shaped to provide a slide compartment immediately beneath said slide bearing surface of the cylinder body, pad holder slides beneath the sectional body and having portions retained thereby. within said compartment and slidable upon the bearing surface of the cylinder body, and means for conveying exhaust air through the side body sections, remote from said side compartment, and for discharging'said air from said body sections across the path of the reciprocating slides so as to prevent foreign matter from entering the slide compartment.

13. In a pneumatic rubbing machine of the character described, the combination of a body equipped with a pair of double-end pistons and with a bottom bearing surface, a pair of pad holder slides reciprocable upon said surface and connected with the pistons for reciprocation thereby, a structure detachably secured to the body and inclosingthe slide compartment, and passages extending from the ends of the cylinders through said detachable structure, remote from the slide compartment, and terminating in discharge openings in juxtaposition to the outer ends of the slides whereby exhaust air from the cylinders will be discharged across the path of the reciprocating slides so asto prevent entrance of foreign matter to the slide compartment.

14. In a rubbing machine of the character described, the combination of a body structure having a narrow slotway through its underside, a pair of pad holder slides mounted to reciprocate on inclosed guideways within the body structure and extending downwardly through said slotway and constructed for carrying pad holders beneath the body, mechanism within said body structure for reciprocating the slides, means for blowing air downwardly from the body along one side of said slotway so as to prevent foreign matter from entering the same, and a deflector beneath the slotway for deflecting said air outwardly away from the active working faces of the rubbing elements.

15. In a rubbing machine of the character described, the combination of a pair of pad holder slides, a body with which said slides --are slidably associated and which carries mechanism for reciprocating the slides, each slide comprising a horizontal portion located beneath the body and with which the pad holder or rubbing element is connected, a vertical portion intermediate the sides of said horizontal portion, and a horizontal portion extending laterally from each side of said vertical portion, one of the lateral portions of each slide being higher than the other lateral portion and extending over the lower lateral portion of the other slide.

16. In a rubbing machine of the character described, the combination of a pair of double pistons spaced laterally in parallel relation in a horizontal plane, a pair of reciprocable pad holder slides arranged beneath the pistons, a pivotal connection between each piston and one of the slides on a vertical axis approximately intersecting the longitudinal axis of the piston centrally between the ends thereof, and a connector between the pistons pivotally mounted to oscillate about a vertical axis intermediate the pistons and centrally between the ends thereof for maintaining the pistons in proper relative relation upon reciprocation thereof in opposite directions.

17 In a device of the class described, a body portion having a pair of laterally spaced parallel cylinders, a pair of reciprocable pistons in said cylinders, pneumatic means for actuating said pistons, means operably connecting said pistons and constraining them to move synchronously in opposite directions, said latter means being wholly enclosed within said body portion, a pair of reciprocable slides driven by direct connections with the center portions of said pistons respectively, and a pair of pad holders carried by said slides positioned beneath said body portion and arranged to move to and from each other with the reciprocation of said pistons.

18.- In a device of the class described, a body portion having a pair of laterally spaced parallel enclosed cylinders, a pair of reciprocable pistons in said cylinders, passages in said body portion adapted to deliver pressure fluid to both ends of each of said enclosed cylinders, valve means for controlling said, passages, a pair of reciprocable, slides driven by direct connections with the center portions of said pistons respectively, means associated with said slides and said pistons adapted to actuate said valve means and to constrain said pistonsto move synchronously in opposite directions, said last mentioned means and said valve means being wholly enclosed within said body portion, and pad holders carried by said slides transversely of said bodyportion and adapted to move in the same plane to and from each other with the reciprocation of said pistons 19. In a device of the class described, a body structure enclosing a pair of spaced parallel cylinders, a piston operable in each of said cylinders, pneumatic means enclosed within said body structure adapted to impart alternate power impulses to both ends of each of said pistons, an operating handle centrally mounted on the upper portion of said body structure having a passage therethrough for connecting said pneumatic means with a source of pressure fluid, means enclosed within said body structure for causing the synchronous'movement of said pistons in opposite directions, a pair of reciprocating slides driven by said pistons and having their bearing surfaces enclosed within said body structure, each of said slides having a depending portion extending outwardly from said body structure, and pad holders mounted on said depending portions transversely of and beneath said body structure, said pad holders being arranged to reciprocate to and from each other with the operation of said pistons.

SWAN F. ANDERSON.

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