US1998770A - Method of and apparatus for grinding and polishing flexible sheets - Google Patents

Description

'April 23, 1935. I SCHULTE I 7 1,998,770

METHOD OF AND APPARATUS FOR GRINDING AND POLISHING FLEXIBLE SHEETS Filed Dec. 30, 1931 5 Sheets-Sheet 1 lfraewir April 23, 1935. LISCHULTE 1,998,770

METHOD OF AND APPARATUS FOR GRINDING AND POLISHING FLEXIBLE SHEETS 'Avvewme: Q [001.5 561/0475 April 23, 1935. L, sc u E 1,998,770

METHOD OF AND APPARATUS FOR GRINDING AND POLISHING FLEXIBLE SHEETS Filed De'O- 30, 9 5 Sheets-Sheet 3 April 23,1935 r 1.. sci-lune I 1,998,770

METHOD OF AND APPARATUS FOR GRINDING AND POLISHING FLEXIBLE SHEETS April 23, 1935. SCHULTE 1,998,770

METHOD OF AND APPARATUS FOR GRINDING AND.POLISHING FLEXIBLE SHEETS Filed Dec. 50, 1931 5 Sheets-Sheet 5 i 40 4a 6. IZ

5 M glza a Arroemzr Patented Apr. 23, 1935 UNITED STATES METHOD OFQAND APPARATUS FOR GRIND- IN G AND POLISHING FLEXIBLE SHEETS Louis Schulte, Cleveland, Ohio, assignor to Schulte Grinding and Polishing Machine Company, Incorporated, Cleveland, Ohio, a corporation of Ohio Application December 30, 1931, Serial No. 583,960

42 Claims.

This invention, in the embodiment illustrated and described, relates to apparatus for grinding and polishing flexible'metallic sheets and to the method used in finishing the surface of such sheets.

In the following specifications and appended claims, the terms grinding" or grinding and polishing are to be interpreted as including such operations upon the surface of a sheet as grinding, smoothing, producing satin finish, bufling,

polishing or similar operations. The term flexible sheets is to be interpreted to comprise sheets ofthe medium or thinner gauges which are relatively flexible in sheets of relatively large area and which can be deflected to a perceptible degree without being injured by such deflection. This term "flexible sheets, is also to be interpreted to include a continuous ribbon of flexible material.

As is-well known to those skilled in this art, it has been practically impossible to produce a uniformly smoothly ground or polished surface on sheets or strips, especially of the medium or thinner gauges of metal, without the expenditure of much time and effort. It has been very difflcult to grind relatively thin sheets or strips without injuring or burning such sheets or strips. This is due partly to the fact that it is very difficult to produce a sheet which is perfectly uniform in thickness and which is perfectly flat. The impairment caused by grinding is also partly due to the fact that it is difficult to produce an abrading or polishing surface, of the type required for this work, which is absolutely true. The dimculty in grinding is multiplied by the fact that a relatively thin sheet, upon being ground, heats up instantly and unevenly due to unevenness of pressure on different portions of the sheet, thus causing the sheet to burn, discolor, warp, and expand irregularly. The lack of evenness of the surface serving to support the sheet and press it against the grinding surface is also one of the important contributing elements which has caused defective work. The

fact that heretofore thin sheets have been ground while they are supported on a relatively rigid and non-yielding or hard surface, has contributed largely to the production of defective finishing because the engagement of the grinding wheel or other grinding element with the surface of the sheet has necessarily caused uneven intensity of contact between the wheel and the sheet at different points for the reasons stated above,

These difliculties have been especially prevalent in the finishing of sheets or strips of stainless steel, which is now used in large quantities and in many applications where a particularly good finish and high polish are essential.

The methods and apparatus heretofore used for grinding and polishing thin sheets required much handling of the sheets and much hand finishing and, all in all, are not adapted for modern production methods.

One of the objects of this invention therefore is to provide methods and apparatus which will produce an even, uniform and smooth finish upon thin relatively flexible sheets and which are, at the same time, adapted for quantity production and which will reduce the ldsses due to defective or incomplete finishing, to a A further object of this invention is to provide methods and apparatus in which the quality of the work produced will not materially be affected by the usual commercial variation in thickness of the sheets, lack of perfect flatness in the sheets or imperfections in the grinding or supporting surfaces.

A further object of this invention is to provide apparatus in which the sheet will not be held between the grinding surface and a hard supporting surface, but in which the sheet is held against the grinding surface by resilient means, the tension of which may be regulated as may be required.

A further object of this invention is to provide apparatus in which the entire area of a thin sheet may be ground and/or polished.

A further object of this invention is to provide apparatus in which the sheet can be instantly withdrawn from the grinding surface at any stage of the grinding action or at any location of the sheet with relation to the grinding element, at the will of the operator.

A further object of this invention is to provide apparatus which is adapted to flex the sheet at the point of grinding concavely toward the rotating grinding surface so as to expose a larger area of the sheet to the grinding surface, thus reducing the intensity of pressure of the grinding surface-upon the sheet.

A further object of this invention is to provide methods and apparatus of a continuous type for successively performing the several different grinding and/or polishing operations on a flexible sheet without removing the sheet from the apparatus.

A further object of this invention is to provide apparatus in which the sheets to be ground may be loosely placed on a conveyor and may be ground and may then be lifted from the conveyor, all without the use of any device requiring the fastening of the sheet to the belt.

A further object of this invention is to provide apparatus in which an unfinished sheet may be fed into one end' of a. machine and in which the sheet may be subjected to a plurality of finishing operations and delivered from the other end of the machine, completely finished, all without any intermediate manual handling.

Another object of this invention is to provide apparatus adapted for the grinding of sheets which will present a substantially continuous surface of the sheets to the grinding element and in which the grinding element continuously maintains contact with the surface of the sheets to be ground.

A further and more specific object of this invention is to produce a machine which is adapted to permit the use of an endless flexible belt for supporting the sheets to be ground during their passage through the machine and during their grinding operation.

A further specific object of this invention is to produce a. novel arrangement of grinding wheel and sheet supporting rollers in'which the sheet is supported and ground between three centers instead of the usual two opposed centers or one center and an opposed support.

A further object of this invention is the production of apparatus of this type and for this purpose, which is simple in construction, economical to manufacture and reliable in its operation.

Further and more specific objects of this invention will become apparent from the following description and claims.

The annexed drawings and description set forth in detail certain means and methods embodying this invention, such disclosed means constituting, however, but one of the forms and but a few of the methods in which the'principle of this invention may be applied.

Referring to the annexed drawings:

Figure 1 is a side elevation of my improved continuous flexible sheet grinding apparatus, this view being drawn to relatively small scale and being partly diagrammatic.

Fig. 2 is a plan view of my improved continuous sheet grinding apparatus.

Fig. 3 is a detached fragmentary perspective view of a belt used in my improved sheet grinding apparatus, this View showing the preferred method of mounting the sheets on the belt.

Fig. 4 is a view similar to Fig. 3 but showing a modified method of mounting the sheets on the belt.

Fig. 5 is anotherwiew similar to Fig. 3 showing a modification in the method of mounting the sheets on the belt when the sheets are relatively narrow as compared with the width of the belt.

Fig. 6 is an enlarged transverse section through the parts shown in Fig. 5. i

Fig. '7 is a view similar to Fig. 5 showing a modified method of mounting narrow sheets or strips on the belt.

Fig. 8 is an enlarged transverse section through the parts shown in Fig. 7.

Fig. 9 is a fragmentary sideelevation of my improved continuous flexible sheet grinding apparatus, the scale of this view being somewhat enlarged overthe scale of Fig. l and showing only the terminal portion and one grinding unit adjagrinding units being broken away.

Fig. 10 is a plan view of the apparatus in Fig. 9.

Fig. 11 is a still further enlarged view of one shown end of the grinding units shown in Fig. 9, this view on the plane indicated by line l2a-l 2a of Fig. 12,

showing the mounting of certain rollers.

Fig. 13 is a view similar to Figs. 3, 4, 5, and 7,

.showing a modified method of mounting the sheet on the belt, this modification including the use of a clamping member.

Fig. 14 is a fragmentary enlarged side elevation of the parts shown in Fig. 13.

Fig. 15 is a transverse section of my improved grinding apparatus, this view being taken on the plane indicated by line l5-l 5 in Fig. 9, and being drawn to the same scale as Figs. 11 and 12.

.Fig. 15a is a fragmentary plan view taken from the plane indicated by line l5al5a in Fig. 15, showing a drive for reciprocating certain of the shafts used in this apparatus.

Fig. 16 is an enlarged view of a portion of Fig. 12, showing certain belt-supporting rollers and pinch rollers and the relation of these parts to the grinding element.

Fig. 17 is a fragmentary view similar to Fig. l6

showing the action of .these parts upon o'verlapping ends of sheets to be ground when the sheets are placed upon the belt in the manner indicated in Fig. 3.

Fig. 18 is a View similar to Fig. 16 showing the preferred position of the parts shown in Fig. 16

as the end of the sheet to be ground approaches the grinding element, when the sheets to be ground are mounted upon the belt in the manner indicated by Fig. 4 or when the leading sheet reaches the grinding element.

Fig. 19 is a view similar to Fig. 16 showing the relative location of the parts shown in Fig. 16 when a relatively thicker sheet is being ground on the belt.

Referring first to Figs. 1, 2, 9 and 10, my inven tion comprises a conveyor whichpreferably consists of an endless relatively flexible belt I made of duck, rubber fabric or other suitable material. This belt is mounted at one end of the apparatus on the driving or head pulley 2 and at the other end on the driven or tail pulley 3. This belt travels through a plurality of grinding units indicated at 4, these grinding units each being provided with a grinding wheel 5 as the abrading or polishing element. The belt further passes through a plurality of grinding units 6 each provided with a grinding belt I as the abrading or polishing element. As will be evident from an inspection of the drawings, the upper strand of the belt passes 'Idler rollers 8 or other supports for the return strand are provided to prevent the sagging or vibration of the return strand of the belt. Upper idler rollers 9 may also be provided for the upper strand of the belt as suggested in broken lines in Figure 9, for those cases for which rollers are found necessary.

The driving or head pulley 2 is.,rotatably mounted in a pair of bearings I0 each mounted on a floor stand said bearings being provided with adjusting screws |2 for a p rp se to be presently pointed out. This pulley is driven by a motor l3 through a suitable gear reducer I4 and sprocket chain drive l5, as will be clearly evident from an inspection of Figs. 9 and 10. The adjusting screws |2 are provided for the purpose of maintaining the proper tension on the sprocket chain drive l5.

Driven or tail pulley 3 is similarly mounted in a pair of bearings l6 each mounted on a floor stand I], these bearings also being provided with adjusting screws l8 for the purpose of regulating the tension on the endless flexible belt I.

The grinding units 4 and 6 are similar except for the type of abrading element which is employed and it will therefore not be necessary to describe both types of these grinding units, and

accordingly a description of grinding unit 6 will suflice for both types.

Referring to Figs. 11, 12, and 15, it will be apparent that each grinding unit consists of three floor stands, I9, 20, and 2|. Fixedly mounted on each of these floor stands is a bearing 22, and a shaft 23 is mounted in each of these three bearings for rotational and axial movement. Fixedly secured to each floor stand I9 and 20 are a pair of stanchions 24, upon the upper end of which brackets 25 are adjustably mounted. Each of these brackets supports a bearing 26 in which a shaft 21 is rotatably mounted.

A pulley 28 is fixedly mounted on the shaft 23 intermediate the stands l9 and 20, this pulley preferably being especially constructed of a plurality of thin fabric discs 28a surrounded by a coating or covering 2822 of rubber or other similar material. A pulley 29 is fixedly mounted on the shaft 21 in a position alined with pulley 28, this pulley being formed of wood, hollow metal, or other satisfactory material. Mounted upon the pulleys 28 and 29 is the grinding or polishing belt I which forms a rotating grinding surface around the lower periphery of the pulley 28 adjacent to the sheets to be ground, as will hereinafter be pointed out.

The shaft 23 is further provided with a driving pulley 3| mounted intermediate the stands 20 and 2|. This pulley is rotated by a driving belt 32 which is in turn driven by means of a motor pulley 33 mounted upon a motor 34, as will be evident from an inspection of Figs. 9 and 10.

The shaft 23 is reciprocated axially by means of a small motor 35 mounted on a bracket 36 which is in turn supported on the floor stand 2|. This motor 35 drives a speed reducing set 31 which drives an eccentric 38. This eccentric engages a suitable groove 39 formed in the shaft 23 and causes this shaft to reciprocate in the bearings 22 as the eccentric rotates. The reciprocation of the shaft 23 causes the pulley 28 to reciprocate in like manner. This reciprocation of the pulley 28 causes the grinding belt I to'reciprocate due to the fact that the pulley 28 is the pulley which drives this belt 1. The pulley 29 is made somewhat longer than the width of the belt in order to permit the belt to travel lengthwise of this pulley 29 as a result of the axial shifting of the pulley 28.

As has been heretofore pointed out, the belt I passes through the upper portion of this grinding unit adjacent to the rotating grinding surface at the underside of the belt, and this belt is supported by a pair of spaced supports which, in the embodiment shown, consist of a pair of spaced supporting or bed rollers 40 as will ap- "and the other in floor stand 20. Screws 41 engage these bearings blocks 45 for the purpose of vertically adjusting the blocks 45, shafts 44 and 44a, and particularly the spaced supporting rollers 4|). These screws are provided with threaded engagement with the floor stands at 48 and are each formed with a hand wheel 48 adapted for manually actuating these screws for the purpose of accurately adjusting the vertical position of the rollers 40.

The front end of the shaft 44a, as viewed in Fig. 11, is longer than the shaft 44, and projects outwardly from the bearing block 45. Fixedly mounted on this outward projection of the shaft 44a is a worm gear 50 which is engaged by a worm 5| mounted on a shaft 52, this shaft being in turn supported in a pair of bearings 53, 53 mounted on a plate which is fixedly secured to the bearing block 45, slidably mounted in floor stand I9. This shaft 52 is provided with a hand-wheel 54 by means of which the worm 5| may be rotated causing the worm gear 50 to rotate the shaft 4411.

At the opposite end, shafts 44 and 44a are each provided with a spur gear 55 meshing with each other, as clearly shown in Figs. 12 and 15. It will now be apparent that a rotation of the hand- Wheel 54 will cause a rotation of the shaft 44a and that the rotation of the shaft 44a through the gears 55 will cause a rotation of the shaft 44 in the opposite direction. The spaced supporting rollers 40 being mounted in the upper ends of the arms 43 and these arms being fixedly mounted on the shafts 44 and 440., will move rollers 40 spaced relatively closely together and Fig. 19 shows these rollers spaced relatively much further apart. A counterweight 56 mounted on a lever 51 fixed on the shaft 44a is provided for the purpose of counterbalancing the weight of the arms 43, rollers 40 and other parts associated with these rollers, so as to facilitate the manual movement of these parts by the handwheel.

Pivotally mounted at each end of each of the rollers 40 adjacent the arms 43 is an angularly shaped bracket 58 shown in Figs. 12 and 15, and Figs. 16 to 19 inclusive. Each of these brackets supports a pair of pinch rollers. the upper one of which is indicated at 59 and the lower one of which is indicated at 60. These pinch rollers are rotatablymounted on shafts 6| and 62 respectively. The belt I passes between the upper and lower pinch rollers as clearly shown. The lower shaft 62 is fixedly mounted in the bracket 58 and the upper of these shafts is mounted in a bearing block 63 slidably mounted in the vertically extending leg of the bracket 58. A screw 64 is provided for the purpose of forcing the roller 59 downwardly with any desired degree of pressure. The upper pinchrollers 59 are each provided with a covering of rubber or other similarly elastic material 65.

The preferred method of placing this apparatus into operation will now be described.

Prior to starting this apparatus, all of the supporting rollers must be lowered away from the grinding elements 5 and I so that these elements will not contact the empty belt. These grinding elements are then set into motion by the startingof the motors 34 and- 35, the motors 34 rotating these grinding elements at a high rate of speed and the motors 35 causing their axial reciprocation. The belt I is then seti'nto motion by start-.

ing the motor I3. The speed of the belt is relatively very slow and its speed will depend on the type of material to be finished, and the type of grinding or finishing elements being used.

A sheet 66 to be ground is now loosely mounted on the moving belt I and this sheet is then carried successively to each of the different grinding units 4 and 6 which are included in this apparatus. When this sheet 66 has reached the center of the grinding element in the first grinding unit, as shown for instance in Fig. 18, the.

supporting rollers 40 in this grinding unit are raised manually by turning the hand wheel 49 until the sheet contacts the grinding surface with the desired pressure. This same raising f the rollers 40 in the other grinding units will be effected as the leading edge of the sheet successively reaches the centers of the grinding elements of all succeeding grinding units 4 and 6.

As soon as the first sheet 66 has travelled a sufficient distance to provide space for another sheet on the loading end of the belt, a second sheet 66a is also loosely mounted on the belt I, the leading edge of this sheet 66a overlapping the trailing edge of the sheet 66, as shown at 61 in Figures 2, 3, and 10. The successive sheets 66b and 660, etc., are then loosely mounted on the belt I as the preceding sheets move in their path through the apparatus, each sheet slightly overlapping the trailing end of the preceding sheets.

It will be apparent that when these sheets reach the pinch rollers 59 and 60, the sheet and belt will be pinched and the sheet will be held frictionally to the surface of the belt I by these pinch rollers, the intensity of this frictional engagement being adjustable as may be required. The rubber covering on the upper pinch roller prevents the scoring or marking of the polished sheet. As shown, these pinch rollers are preferably provided at points just ahead of and just behind the point where the grinding or polishing element engages the sheet and they are provided for the purpose of preventing the sheet from being shifted or thrown longitudinally of the belt by the force of the grinding action on the sheet, either as the front end of the sheet meets the grinding roller or as the trailing end of the sheet leaves the grinding roller.

The sheets maybe overlapped in the manner shown at 61 so that it will not be possible for the grinding surface to engage the trailing edge of a sheet and curl it upwardly, causing damage to the sheet and possible damage to the grinding surface. The relation of the overlap 61 to the grinding surface is clearly shown in Fig. 17. However, the sheets may be successively placed on the conveyor with a slight space between the sheets.

An inspection of Fig. 16 will disclose the fact that the belt I together with the superimposed sheet 66 is slightly depressed downwardly by the center of the grinding surface of the belt 30. It will be understood that the intensity of contact pressure of the grinding surface of sheet 66 may be varied either by changing the tension on the belt I or by changing the spacing of the rollers 40 or by raising and lowering these rollers 40 by means of the mechanism provided for this purpose. In the use of this construction, there is no fixed, unyielding, or hard surface immediately under the point at which the sheet is being ground, and if there is any variation in the thickness of the material of the sheet or in the surface of .the grinding element, or in the surface of the supporting element, the belt will flex sufficiently to absorb these or any other irregularities. The reciprocation of the grinding element avoids the formation of deep scratches in the sheets and makes it easier to produce a high finish on the sheet.

When each sheet has passed through all of the grinding units it may be lifted from the slowly moving belt, as will be understood, or it may be allowed to discharge onto another conveyor from the end of the belt conveyor. 'It will be understood that the number of grinding units employed in a continuous sheet grinding apparatus of the type described will vary with the number of operations required onthe sheet, and thenumber of units shown in Figs. 1 and 2 is illustrative only. It will also be understood that the several successive grinding units will be provided with different types or grades of polishing elements as may be required to finish the sheet to the desired degree.

It will be understood that different thicknesses of sheets to be ground will require different intensities of contacts a of the sheet against the grinding wheel, and it is particularly pointed out that a thicker sheet will require a wider spacing of the supporting rollers 40 as the resistance to deflection of a thick sheet is considerably greater than that of a thinner sheet. This condition has been illustrated in Fig. 19 where a relatively thick sheet 68 is shown mounted on the belt.

It will also be apparent that the pinch rollers,

being supported in brackets 56, which are pivotally mounted on the rollers 40, will float and will in fact be supported by the belt I and will move or shift vertically with a change in the vertical position of the belt. This is clearly shown in Figs. 16, 18, and. 19.

It will also be apparent thatthe preferred method of loosely mounting the sheets on the belt in an overlapping manner as described above and as illustrated in Figs. 2, 3, and 10, will cause practically the entire upper surface of the belt to be covered with sheets to be ground and that in this method only a very small portion of the edge of the belt is exposed to the grinding surface. This small portion, however, is held spaced from the grinding surface by the thickness of the sheets and the belt is therefore not injured by the Leesmo of "the belt by the grinding wheel to raise the supporting rollers 40 when the leading end of the sheet reaches the lower point of the 'grinding surface or I and to again lower the supporting rollers when the trailing end of the sheet reaches the lowermost point of the grinding surface. It

is also possible in this method to reverse the direction of travel of the belt I just prior to the .time when the end of the sheet reaches the lowermost point of the grinding surface. This method has the advantage that a much smaller number of grinding units may be employed as one unit may perform its operations upon the sheet several times. In this event, it is only necessary to provide a sufficient number of grinding units to provide all the types or grades of finishing or polishing surfaces which may be required.

When relatively narrow sheets are to be ground, a plurality of them may be placed with their longitudinal edges adjacent each other so that they.

substantially cover the entire width of the belt.

- In the event, however, that there is not a suflicient number of pieces of the same thickness to be ground. it is possible and practical to cover the belt with a relatively thin, soft, annealed, flexible, black plate. 'such, for instance, as the sheet shown in Figs. 5 and 6, this sheet being riveted with copper rivets, or otherwise secured to the belt and covering the entire outer surface ofthe belt. The strips H to be ground may then be placed in any desired position, preferably centrally, on the covered belt. When this combination is passed through the apparatus and when the sheets are being ground, it is probable that some portions of the covering 10, especially near the edges of the belt, will be ground through in time, due to the fact that the plate may contact the grinding surface. This covering material 10. however, being a relatively cheap material and being easily applied, its renewal will not entail any great expense nor inconvenience upon the operator of this apparatus.

In Figs. Z and 8 another method of adapting this apparatus for grinding relatively narrow strips is shown, this method including the placing of a relatively thick plate 12 of flexible metal, fibre or the like, on the belt and then placing the relatively thinner narrow strips" which are Gil position or releasing the same.

to be ground. on top of this plate 12. The relatively thick plate 12 will hold the belt I sufliciently spaced from the grinding surface to prevent the accidental engagement of the belt with the surface. It will= be understood, of course, that the material 12 must not be of a thickness which will prevent the flexing of the sheet under the grind ng surface to a position substantially as shown in Figs. 16 and 19.

In Figs. 13 and 14 another method of mounting the sheet on the belt is shown, this method contemplating the use of a clamp adapted to permanently fix the sheet 74 to the belt until the clamp is released. This clamp comprises an eccentric 15 supported in a pair of ears I6 mounted on a cross member 11. A handle 18 fixedly mounted with relation to the eccentric is provided for the purpose of moving the eccentric to the clamping When this method of holding the sheet on the belt is used, it is, of course, not necessary to provide the pinch rollers 59 and 60. It will also be evident that the supporting rollers 40 must be lowered when the clamping eccentric 15 approaches the grinding element in order to permit this clamp to pass- If it is not desired, to lower the supporting-rollers 40 the direction under the grinding element.

of travel of the belt I may be reversed and the number of operations required to finish the sheet may be performed by the same grinding element, after which the sheet may be removed or passed on to the next grinding or polishing element.

The apparatus herein described produces a uniformly smooth ground or polished surface on relatively thin sheets of material of relatively large areas, without burning, warping, distorting, or otherwise injuring the sheets, and this apparatus produces this result in a continuous manner with a minimum of manual handling and conforms to modern production methods. This apparatus eliminates those features referred to at the beginning of this specification, which have heretofore caused defects in the finishing of these sheets. It will also be clear that the tension of the belt yieldinglyholds the sheetagainst the grinding surface and that the intensity of this contact between the sheet and grinding surface can be additionally adjusted to suit the requirements by the mechanism provided. It will also be clear that the mechanism described consists of a very adaptable means for flexing the sheet concavely toward the grinding surface and for varying the radius of the curvature of the sheet and the arcuate length of engagement of the sheet with the grinding surface. It will also be apparent that this apparatus discloses a simple mechanism which will permit the instant withdrawal of the sheet from the grinding surface at any point during the grinding operation at the will of the operator. The provision of such dropping or disappearing rollers is especially advantageous in the event that the grinding element starts to spoil a sheet, when the sheet can be lowered or pressure on the wheel released before much harm is done and long before the belt or grinding wheel could be-stopped. Attention is also directed to the location of the axis-of the grinding wheel and the axes of the supporting rollers at the apexes of a triangle, resulting in a thereby. It is contemplated, for certain purposes, to use only one grinding unit between the head and tail pulleys, as one practical embodiment of-this invention. In this case, the sheet to be ground is passed back and forth through the grinding unit by reversing the direction of travel of the belt until the necessary number of passes have been made. The sheet is then placed in another similar machine performing a succeeding operation. This method reduces the number of grinding units required for a complete installation, but necessitates more handling of the sheets.

It will be understood that various alterations, modifications, and/or additions may be made in theapparatus shown without departing from the scope of this invention as defined by the appended claims. For instance, automatic means for raising and lowering the supporting rolls might be provided in order to raise and lower these rolls at predetermined points as may be desirable. Likewise this invention is not limited'to the use of pinch, rollers as other means may be provided for holding the sheet in position on the flexible belt.

It should also be pointed out that numerous modifications might be made in the flexible belt, such, for instance, as the substitution of a chain belt therefor, or the substitution of a plurality of narrower belt sections might be made for this belt.

One particularly advantageous adaptation of this invention is for use as a strip polishing machine for polishing relatively narrow thin strips having a width of ten inches or less. For this purpose the conveying belt is made correspondingly narrower than the belt shown and a continuous strip several hundred feet in length is fed from a reel onto one end of the conveying belt and again wound on a reel from the discharging end of the conveyor belt after it has been successively engaged by a series of grinding and/or bufling elements. For such strip polishing apparatus a single pair of pinch rollers located near the loading end of the conveyor belt is usually sufficient.

In several of its broader aspects, this invention is not confined to the use of a flexible belt for supporting the sheet. It is thoroughly practical to pass the sheet to be ground through a grinding unit and support this sheet directly on the supporting rollers without the interposition of any conveying belt. In its broader aspects, also, it is not necessary that the spaced supports under the grinding elements be rollers as these supports may take any form adapted to hold up the belt. In its broader aspects, also, it is not necessary that the grinding elements be located between the spaced supports. It is perfectly practicable to deflect the belt downwardly adjacent one of such supporting rollers only and thus produce the necessary tension between the sheet and the grinding unit.

One process, for the practice of which the herein described apparatus is particularly well adapted, is fully described and claimed in my co-pending application, Serial No. 615,580, filed June 6, 1932.

Many other modifications of this invention and its application will naturally occur to those skilled in this art, and the present disclosures should therefore be considered as typical only, and I desire not to be limited to the exact constructions.

shown and described.

What I claim is:

1. The method of grinding the surface of an individual flexible sheet consisting of mounting the sheet on a relatively slowly traveling flexible belt, causing the belt to carry the sheet into engagement with a rapidly rotating grinding surface, causing the sheet to progress across the I grinding surface'at the same speed as the belt,

and causing the sheet and. the belt to flex conjointly concavely toward the grinding surface at the point of grinding, and frictionally holding the sheet to the belt while it is being ground.

2. The method of progressively grinding the surface of a flexible sheet consisting of supporting the sheet on a relatively flat flexible belt under tension, causing the belt to carry the sheet successively into engagement with a plurality of different grinding elements, and deflecting the belt concavely toward the grinding surfaces at the grinding elements, causing the sheet to be held against the grinding elements, by the' tension of the deflected belt, and frictionally holding the sheet fixed on the belt at each grinding element.

3. The method of grinding the surface of a flexible sheet consisting of loosely supporting the sheet on a flexible belt, causing the sheet to $11.0-

cessively engage a series of separate grinding surfaces located at spaced stations, concavely flexing the sheet at the grinding surfaces to present a concave portion of the sheet to each grinding surface, and holding the sheet in frictional engagement fixed relatively to said belt at each grinding station, and releasing said frictional engagement after the sheet has passed the station.

4. The method of finishing a plurality of relatively flexible sheets consisting of placing said 5. In a continuous sheet griding apparatus, a

plurality of spaced grinding units, an endless flexible belt mounted on spaced driving and. driven pulleys and passing said grinding units and adapted to support a plurality of individual rectangular flexible sheets placed lengthwise on the belt, each of said grinding units comprising a rotating grinding surface and mechanism independent of said grinding surface, for frictionally holding each of said sheets to said belt while said sheet is being ground and mechanism adapted to flex the belt concavely toward the grinding surfaces.

6. In a machine for grinding individual flexible sheets, a grinding element, a flexible belt adapted to carry the flexible sheets on its upper surface, spaced supports engaging the lower surface of said belt leaving the belt unsupported there-' between, means adapted to contact the grinding element with the upper surface of the belt at said unsupported portion, and means adapted to constrain the flexible sheets to travel at the same speed as the belt and prevent the moving of said sheets on the belt by said grinding element.

7. In a machine for grinding flexible sheets, a traveling flexible belt adapted to support the sheets on one sideand mounted on spaced pulleys, spaced supports engaging the other side of said belt and located intermediate said pulleys, a grinding element adapted to contact said sheets intermediate said supports, means for varying the intensity of contact between said element and said sheets, and means adapted to constrain said sheets to travel in a fixed position on and at the same speed as said belt.

8. In a machine of the character described, a

traveling flexible belt adapted to convey flexible sheets on its upper surface, spaced supports engaging the under side of said'belt, a grinding element adapted to contact the upper surface of said belt intermediate said supports, and means for' varying the spacing of said supports in-a hori-,

vey a flexible sheet, said belt being mounted on spaced pulleys, means for rotating one of said pulleys, a pair of spaced supports located intermediate said pulleys and engaging one side of said belt, said grinding element contacting said sheet on said belt only intermediate said supports, mechanism adapted to raise the supports and lower the supports while said belt is moving whereby said sheet is contacted with and withdrawn from contact with said grinding surface, and means for preventing the shifting of the sheet relatively to the belt.

11. In apparatus for grinding a flexible sheet, in combination, means for progressing the sheet, spaced bed rollers independent of said progressing means adapted to support the sheet, a grinding element adapted to contact said sheet between .said spaced rollers, and means for varying the proximity of the rollers and the grinding element by changing the spacing of the rollers.

12. In apparatus for grinding flexible sheets, in combination, three parallel rollers mounted in spaced triangular arrangement, and a traveling belt formed of flexible material and adapted to support a flexible sheet, passing between said rollers and contacting said rollers, one of said rollers being provided with a grinding surface, means for varying the proximity of said rollers, and means adjacent said rollers adapted to frictionally constrain the sheet to move with the belt.

13. In apparatus of the character described,

a movable flexible belt adapted to support a flexible sheet, said belt'being mounted on spaced pulleys, spaced bed rollers located intermediate said pulleys, supporting said belt, a grinding element adapted to contact a sheet supported on the belt, intermediate said rollers, and roller elements frictionally holding said sheet on said belt independently of said grinding element, whereby a shifting of the sheet on the belt by the grinding element is prevented.

14. In apparatus of the character described, a grinding surface, a traveling flexible belt adapted to loosely support and convey a flexible sheet past said grinding surface, a vertically movable roller mechanism adapted to support said belt, and a pair of idler pinch rollers, including said sheet and belt, and adapted to frictionally hold said sheet to said belt. I

15. In apparatus of the character described, a rotating grinding surface, a traveling flexible belt adapted to convey individual flexible sheets loosely mounted thereon, past the grinding surface, vertically movable roller mechanism adapted to support said belt, and a pair of idler floating pinch rollers, said pinch rollers anchored against traveling with the belt but adapted to shift vertically with the belt.

16. Apparatus for grinding flexible sheets, a

grinding element, a flexible'sheet conveying belt adapted to progress the sheet beneath the grinding element, adjustable supports for said conveying belt adapted to progressively flex the moving belt concavely toward the path of the periphery of the grinding element, means for progressively holding the sheet in frictional engagement with the conveying belt, and means for reciprocating the grinding element transversely of the direction of movement of the sheet.

17. In apparatus for grinding flexible sheets, in combination, a conveyor adapted to support the sheet to be ground, a roller supporting said conveyor and pinch roller mechanism pivotally mounted with relation to said conveyor supporting roller and adapted to frictionally hold the .in combination, a conveyor adapted to support the sheet to be ground, conveyor supporting rollers mounted on a shaft, a pair of pinch rollers mounted in a bracket pivotally mounted on said shaft, one of said pinch rollers being located above said conveyor and the other of said pinch rollers being located below said conveyor.

19. In apparatus for grinding flexible sheets, in combination, a conveyor adapted to support the sheet to be ground, said conveyor resting on a pair of spaced conveyor supporting rollers each mounted in a tiltableframe, and mechanism for simultaneously tilting said frames in opposite directions, whereby they spacing of said rollers is varied.

20. In apparatus for grinding flexible sheets, in combination, a conveyor adapted to support the sheet to be ground, said conveyor resting on a pair of spaced conveyor supporting rollers each mounted in a. tiltable frame, and mechanism for simultaneously tilting said frames in opposite directions, and an adjustable pinch roller mounted on one of said brackets and adapted to hold the sheet against said conveyor.

21. In apparatus for grinding flexible sheets, in combination, a conveyor adapted to support the sheet to be ground, said conveyor resting on a pair of spaced conveyor supporting rollers each mounted in a tiltable frame, and mechanism for simultaneously tilting said frames in opposite directions, and a pair of pinch rollers pivotally mounted adjacent one of said supporting rollers and mounted to move vertically with said belt.

22. In grinding apparatus, in combination, a flexible belt, a flexible sheet mounted 'on said belt, a rotating grinding surface adapted to contact said sheet, a pair of spaced rollers for supporting said belt under said grinding surface, and means adapted to move said rollers to concavely flex said sheet around said grinding surface, and a pair of pinch rollers pivotally mounted with relation to one of said rollers adapted to frictionally hold said sheet to said belt.

23. In an apparatus for grinding individual flexible sheets, in combination, a grinding element, a conveyor belt adapted to progress the sheets beneath the grinding element, and means for successively and progressively clamping the sheets to the belt, wherebythe sheets are constrained to travel with and at the speed of the belt, and concavely flexing them toward the grinding element as they pass the grinding point.

24. The method of grinding the surface of a relatively flat flexible sheet consisting of feeding the sheet on a flexible beltriding upon a pair of spaced supporting rollers, causing a grinding element to engage the sheet between said supporting rollers and flex the sheet at the grinding element, in a direction opposed to the support of the rollers, and progressively holding that portion of the sheet adjacent to the grinding element, in frictional engagement with the belt, whereby the sheet is caused to travel with and at the speed of the belt, and permitting the balance of the sheet to shift freely on the belt before it reaches the grinding element and after it passes the grinding element.

25. In apparatus for grinding flexible sheets, a grinding element, a composite conveyor adapted to support and progress the sheets in contact with the element, said conveyor consisting of a belt formed of relatively flexible material and a covering of relatively wear resisting flexible material on-the sheet supporting face of the belt, said belt and said covering being adapted to flex conjointly. I

26. In apparatus for grinding flexible sheets, a grinding element, a conveyor adapted to support and progress the sheets in contact with the element, said conveyor consisting of a belt formed of relatively flexible material and a covering of relatively wear resisting material renewably mounted on the sheet supporting face of the belt, said belt and said covering being adapted to flex conjointly.

27. In apparatus for grinding a flexible sheet, a grinding element, a conveyor adapted to progress the sheetin contact with the element, said conveyor comprising a composite belt formed of flexible materiaL provided with a covering of flexible wear resisting material secured to the belt and adapted to support the sheet, means for actuating the conveyor, and means for conjointly flexing the conveyor and covering and sheet concavely toward the grinding element at the point of grinding. i

28. In apparatus for grinding a flexible sheet, a rotating grinding element, a moving conveyor formed of flexible material and adapted to support and progress the sheet in contact with said grinding element, a holding-device moving with the conveyor adapted to rigidly hold one end of the sheet and including 'a member adapted to rigidly hold one end of the sheet in frictional engagement with the conveyor substantiallyin the plane of the sheet supporting surface of the conveyor whereby the sheet is prevented from being shifted on the conveyor by the abrasive action of the grinding element.

29. In apparatus for grinding a flexible sheet, a rotating grinding element, a conveyor formed of flexible material and adapted to support and progress the sheet in contact with said grinding element, a clamping device mounted on said conveyor, said clamping device including a rigid member engaging the under side of the conveyor and, a member above the belt opposed to the rigid member and movable toward and from the upper surface of the conveyor, adapted to rigidly clam one end of thesheet.

30. In apparatus for grinding a flexible sheet, a rotating grinding element, a moving conveyor formed of flexible material and adapted to support and progress the sheet in-contact with said grinding element, a holding device adapted to rigidly hold one end of the sheet to the conveyor, said device including an eccentric rotatably supported adjacent the upper side of the conveyor and adapted to pinch the sheet between the eccentric and the upper side of the conveyor, and a relatively rigid member supported adjacent the lower side of the conveyor and juxtaposed to the eccentrio and adapted to resist the thrust of said eccentric against the flexible conveyor;

31. In an apparatus for grinding flexible sheets, in combination, a flexible belt, a grinding element, means for causing the belt to travel, means adapted to engage a sheet on the belt with the grinding element, and means traveling with the belt for clamping one end of the sheet downwardly to the belt, and means for conjointly flexing the belt and sheet at the point of engagement of the sheet with the grinding element.

32. In a machine of the character described, the combination of a rotating grinding element, sheet-supporting means, means for progressing a sheet into.v contact with the grinding element,

adjustable supporting rollers for deflecting the sheet concavely toward said element, one of said rollers being in advance of and the other roller being behind the rotating grinding element with relation to the direction of travel of the sheet, and means operable from a single point for adjusting said deflecting rollers while maintaining their axes parallel with the grinding element.

' 33. In a machine for grinding flexible sheets, the combination of supporting rollers on which the sheet rests and on which it is moved, a grind ing element, a pair of said rollers being so arranged that the sheet between the rollers is free to flex whereby it may present a concave surface to the grinding element, one of said pair of rollers being in advance of and the other of said pair of rollers being behind said rotating surface relative to the direction of movement of the-sheet, and means for controlling the flexing of the sheet by simultaneously adjusting the position of said pair of rollers withrespect to the grinding element.

34. In an apparatus for grinding flexible sheets in combination, means for progressing the sheets to be ground, a grinding elementand a pair of spaced supports for the sheet, said element and said supports, respectively, being located onopposite sides of the sheet, each support being mounted in a frame, and means for simultaneously tilting said frames in opposite directions to vary the spacing of the supports.

35. In a machine for grinding flexible sheets, the combination of a grinding element, a supporting belt for thesheet, means for progressing the belt, a pair of spaced supports for the belt on opposite sides of the radial plane of the grinding element normal to the belt, and means for simultaneously separating said supports and moving them away from the grinding element.

36. The combination of a grinding element, a supporting belt below the element, a pair of spaced supports below the belt whereby a flexible sheet may be held in contact with the grinding element for considerably more than a line contact, and means for symmetrically adjusting the position of the supports vertically and horizontally with reference to the vertical center plane through the grinding element.

37. In an apparatus for grinding flexible sheets, the combination of a grinding element, a belt formed with a substantially flat surface and made of relatively flexible material adapted to support individual sheets, means for moving the belt to carry the sheets one after another past the grinding element, and adjustable means for clamping each sheet to the surface of the belt in front of and behind the grinding element with reference to the direction of travel of the sheets, during the grinding operation.

38. In an apparatus for grinding flexible sheets, the combination of means for progressing the sheets to be ground, a grinding element, a pair of idle supporting rollers for the sheet, said rollers being spaced on opposite sides of the grinding point, and means for simultaneously adjusting said supporting rollers in a vertical direction with relation to the grinding element, whereby 'the sheet is progressively flexed to a uniform extent throughout its length.

39. In an apparatus for grinding flexible sheets, the combination of means for progressing the sheets to be ground, a grinding element, a pair of idle supporting rollers for the sheet, said rollers being spaced on opposite sides of the grinding point with relation to the direction of travel of the. sheets, and means for simultaneously adjusting said supporting rollers in a vertical and horizontal direction.

40. In apparatus for grinding flexible sheets, in combination, a belt formed of relatively flexible material adapted to support and convey the sheets, a pair of spaced pressure rollers engaging the upper surface of the belt, adapted to frictionally hold the sheets to the belt, a pair of spaced support rollers engaging the under surface of the belt and located intermediate said pressure rollers, a rotating grinding element adapted to contact the upper surface of the belt at a point intermediate said support rollers.

41. In apparatus for grinding flexible sheets, in combination, a belt formed of relatively flexible material adapted to. support and convey sheets, a pair of spaced roller elements adapted to support the belt, a rotating grinding element adapted to engage the belt intermediate said supgrinding element, and other means for adjusting the support vertically and horizontally to move the belt and the work carried thereby into and out of contact with the grinding element.

LOUIS SCHUL'I'E.

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