US2095697A - Sheet scrubbing - Google Patents

Description

oct. 12, 1937. 0. M. HAMMER 2,095,697

l SHEET SCRUBBING A Filed Nov. 18, 1955 e sheets-snaai 1 r l 1 l Oct. 12, 1937. o. M. HAMMER SHEET SCRUBBING Filed Nov. 18, 1935 6 Sheets-Sheet 2 Oct. 12, 1937. o. M. HAMMER SHEET SCRUBBING Filed NOV. 18, 1935 6 'Sheets-Sheet 5 Oct. 12, 1937. o. MfHAMMER SHEET SCRUBBING A Filed Nov. 1s, 1935 6 sheets-sheet 4 A M NQ .HMV 4 l @l .W Q JH.' Y W @ha Oct. 12, 1937. l o. M. HAMMER 2,095,697

SHEET SCRUBBING Filed Nov. 18, 1935 6 Sheets-Sheet 5 200 Zei/ [weizfo: @La M #4M/WEE,

Oct. `l2, 1937. o. M. HAMMER 2,095,697

SHEET SCRUBBING Filed Nov. 18, 1935 6 Sheets-Sheet 6 Inventor'.- -OAMC- M. #4M/WEE,

Patented oci. 12, 1937 SHEET SCRUBBING laf M. Hammer, Vandergrift, Pa., assigner to American Sheet and Tin Plate Company, a corporation of New Jersey ApplicationNovember v18, 1935, Serial No. 50,443

s claim. (ci. 15-17) i 'I'his invention relates to cleaning the surfaces of sheet-like material and, while not limited thereto, i's particularly concerned with scrubbing both sides of substantially flat metal sheets which are relatively thin and brittle.

One of the objects is to provide a scrubbing machine capable of cleaning both sides of flat sheets of extremely thin 'gages which heretofore, because of their thinness, were necessarily manually scrubbed.

Another object is to scrub without damage both surfaces of a sheet which is naturally brittle, the surfaces and especially the ends of which will in ordinary scrubbing machines be bent or broken.

The usefulness of sheet scrubbing machines has heretofore been restricted, in the steel industries at least, to fairly heavy gage sheets such as No. 26 U. S. S. gage and heavier. Sheets lighter than this have not as a general rule had suiiicient rigidity and body strength to withstand the scrubbing action. This condition has necessitated the slow, laborious and costly manual scrubbing of thin gage sheets which is overcome by the present invention Furthermore, by means of the present invention one is able to mechanically scrub extremely brittle sheets such as silicon sheets used for electrical purposes.

Silicon sheets, having a usual `commercial silicon content ranging from .15% to 4.5%, are necessarily brittle and if scrubbed in the usual manner have one or both ends badly bent, torn and even broken by the action of the brushes of conventional scrubbing machines.

'I'he present invention is here disclosed in the form of la machine for uniformly cleaning thin gaged silicon sheet metal which is so thin and brittle that the usual scrubbing machines would l damage such a product and which therefore commercially has heretofore been manually scrubbed free from loose oxides and dirt follow ing its pickling.

Referring to the accompanying drawings:

Figure 1 is a partially broken away top view of the sheet scrubbing machine that embodies the principles of the present invention.

Figures 2 and 3 are sections respectively taken from 'the lines II-lI and IDI- III in Figure 1, Figure 3 showing the side of the machine in elevation excepting for one of its driving units.

Figure 4 is a section taken from the4 line 1V- IV in Figure 3, this gure showing the exit end of the machine in elevation excepting for certain minordetails.

' Figure 5 is a section taken from the line V-V in Figure 4 and shows in elevation the major 'portion of the side of the machine opposite to that shown by Figure 3, excepting for the omission of one of the machines powering motors.

Figure 6 is a wiring diagram of the machines control system.

Figures 7, 8 and 9 are diagrammatic views showing different phases of the scrubbing operation performed by this machine.

Two parallel, and longitudinally extending housing bases I 0 vare transversely connected by separators II, these bases being rigidly held together by steel keys I2. On one side of this base assembly is secured a roll drive base I3 while on the opposite side is fastened a motor base I4. On the roll drive base and brush drive motor base are mounted the motors for the pinch rolls and rotary brushes respectively, which are later described. The roll and brush drive and motor bases are secured to the outside portions of the housing bases I 0 by the keys I2.

Cn top of the housing bases Il! are equal and oppositely mounted vertically extending roll .housings I5 with vertically extending slots or windows I6. .These housings go to make up the v are vertically extending, equal and opposite brush housings I1. These brush housings each vhave shaft openings I8 and arcuated slots I9. Adjacent and abutting said brush housings and likewise extending along the top of the housing bases I0 toward the exit end of said machine are another pair of equal and opposite roll housings 20 having windows I6:V

Likewise adjacent and abutting roll housings 20 and extending along the top of the housing 40 bases III and toward the exit'end of said ma. chine are equal and opposite brush housings 22 which have shaft openings I8* and arcuated slots IS. The arcuated slots of these second named brush housings are equal but curve4 oppositely to the similar slots in the brush housing I1 for reasons to be later described.

Finally, adjacent and abutting this second set of brush housings 22 and resting on the housing base III are equal and oppositely spaced roll housings 23. These roll housings differ from the first and second named roll housings in that they have a double window I6' and constitute the exit end pf the machine. Y

Thus aremade upV the base and sides proper of the machine. These bases and sides may be of cast iron. The abutting `sectional sides of these 'roll and brush housings may overlap so as to be held together in any suitable manner, such as'by guides to further aid in conveying the sheets.

'Ihe top and bottom guides, as well as the upper and lower pinch rolls, rotary brushes and sprays, are respectively above and below the center line of travel of the sheet material and vwill hereafter be so designated.

Tov simplify the details of the above apparatus it will bedivided and separately explained as the rotary brush, conveying, guiding, spraying-and operating control systems. The correlated action of all systems will then be exemplied in a brief summary of the general operation of said apparatus.

` Rotary brush system The rotary brush system includes at least one 'pair or unit of stiil' ber or wire brushes which rotate in the same scrubbing direction and above and below the sheet material being cleaned. The preferred embodiment, however, includes two such units of rotary brushes, one pair or unit hereafter designated as A constantly rotating in a scrubbing direction opposite to that of the other 'pair B.

'I'he pair of brushes A are madeup of parallel brushes 30 and 3| located above and below the -center line of sheet travel respectively, and rotating in the same scrubbing direction. Likewise in. pair B, which parallel the first named pair, are brushes 32 and 33 respectively located l' above and belowthe center line of sheet travel but rotating in an opposite scrubbing direction to the pair A.

These brushes 30 to 33 inclusive are mounted on shafts 34, the ends of which extend through ,the arcuate slots I3 and I9' of the brush housings I 'Il and 22, respectively. The ends of these brush -shafts 34 are rotatably secured to brush arms 35 to 33 inclusive, located on the outside of the housings. Thus the pair of brushes A are rotatably secured tov brush arms 35 and 33 on the free and driven sides respectively, while the ends of the shafts of the pair of brushes B are rotatably secured to brush arms 31 and '38 on their free and driven sides respectively. All of the brush arms are secured for reciprocating movement about stud shafts 39 set in the shaft openings Il of their respective housings.

In general, each brush arm is made up of a longvertically extending arm to the lower end of which are integrally attached short arms which extend from either sideof the vertical extension at an angle of about 45 thereto.- The 1 intersection of the short angular arm and the vertically extending long arm constitutes the center of reciprocating movement of each brush Between the pinch rolls,

movement of one brush -unit to the other.

sions are shaft openings into which are rotatably secured the brush shafts 34 just mentioned.

The brush arms 36 and 38 on the driven side are similar in construction to their respective I companion brush arms 35 and 31 except that the short extension arms are further extended to include a iixed idler triple width sprocket 40 around which rotates a triple width driving chain 4|. Furthermore, arms 36 and 38 carry a `housing integral with and between the vertical arm and the lower side of the short extension arm. Within each integral housing is mounted a springtensioned, vertically adjustable idler sprocket pin box 42 which maiz'tains the driving chain 4I under constant tension.

Mounted von the cast motor base I4 is a motor 43 which through a shaft and pinion 44 and 45, respectively, drives a gear 46. 'I'his gear in turn carries a short drive shaft 41 which is supported in a four-bearing standard 48 having two bearing supports for said shaft 4l. Between the bearing supports is a triple width sprocket 49 which drives triple width chain 4|.

'Ihis driving chain 4|, traveling constantly in a counter-clockwise direction, rotates a sprocket 50 which is fixed to the brush shaft 34 and drives the lower brush 3| of the pair A. This chain 4I then passes over vertically adjustable idler sprocket 42 and hence to the xed idler sprocket 40.

Another sprocket 5| is ilxed to the shaft of the upper rotary brush 30 and the chain 4| is passed over this sprocket in such a manner that the said brush rotates in the same scrubbing direction as the brush 3| which lies in a plane below the center line of the sheet travel, the brush 30 being above the centerline of sheet travel. The triple width chain 4| finally passes from the brush sprocket 5| to the sprocket 49 and the drive cycle for the pair of brushes A is com- -sprocket 40. The chain then passes over asprocket 5| which, fixed to the shaft 34 drives the upper brush 32 in such a manner that its rotation is in the same direction as the brush 33 which lies in a plane below the center line of sheet travel, the brush 32 being above the centerline of sheet travel. 'I'he triple width chain 4 i finally passes from the brush sprocket 5| to drive the sprocket 49' and the drive cycle vfor the pair of brushes B is complete.

Attached to the top of each of the brush arms 35 to 38 inclusive are worm housings 60. Each of these housings retains a short worm shaft 6| on which is iixedly mounted a worm 62. Worms 62 and worm shafts 6| on opposed housings are interconnected by a transverse shaft 33 throughl clamp couplings 34.

Mounted in each housing Il and meshing at right anglesto the worm 32 is a rotatable worm wheel 35 through which are threaded parallel and longitudinally extending screws 36. These screws also serve to interconnect brush units A and B, thereby transmitting simultaneous reciprocating These screws 86 are transversely.. connected and braced by a steel angle 61. To this cross brace Slis attached a connecting fork 68 which in turn is connected to a crank drive to be later described. 'I'his connecting fork in moving back and forth transmits, through parallel screws 86, simultaneous reciprocating motion as desired to the brush arms 35 to 38 inclusive.

Byv release of a lock nut wheel B9 and the manual turning of the hand-wheel l0 as secured to the worm shaft 6l, the opposing brush arms (for example 3l and 38) are caused to be jointly moved to the right or left, thus varying the position of their brushes 32 and 33 closer or farther away from the center line of sheet travel. Likewise, the brushes 30 and 3| may be shifted toward or away from the center line of sheet travel by the rotation of the hand-wheel and worm shaft by which they are interconnected.

4Such a shifting of one pair of brushes to indirectly or directly vary their pressure on the sheet passing therebetween has no effect on the position or pressure of the other pair of arms, each pair being capable of independent adjustment of the other.

Conveying system The conveying system includes several pairs of Idriven pinch rolls all rotating in the same directhe ends of which are welded shaftsA 8,4 which are mounted in suitable bearing blocks or chucks 8l. These chucks 81 are located in equal and opposite windows I6 of the roll housings I5. 'I'he pinch roll is superimposed on the driven pinch roll 80 and is driven by frictional contact therewith, constant contact being maintained by spring-tensioned screws vertically adjustable through a housing cap 86.

Likewise located about the middle of the apparatus and between the two sets of brush rolls A" and B 'are pinch rolls 8| and 8| which are constructed and arranged similarly to rolls 80`80' but positioned in windows I6 of the equal and opposite roll housings 20. e

Beyond the set of brushes B and adjacent the exit end of the machine aretwo pairs of pinch rolls 82-82' and 83-83 which are constructed and arranged as are the previously mentioned pinch rolls except that they are located in double housing windows I6 of the equal and opposite roll housings 23.

The pinch roll shafts 88 extend at one end through their respective bearing blocks or chucks Y 8l and respectively carry single and double sprockets 88 and89 keyed thereto. Thus the shafts of the pinch rolls y8| and 82 each carry a double sprocket 89 while shafts of pinch rolls 80 and 88 each carry a single sprocket 88.

A motor 90 is mounted in the rll drivebase wand .drives a worm gear speed reducer 92 through a shaft l9| and coupling 93. 'Ihe speed reducer` 92, likewise mounted on the base I3, drives the pinch roll 8| through a shaft 94 and a coupling 95. Thel double sprocket 89 mounted on the shaft 80- drives, through the chain 98; the

' pinch roll 80 by the single sprocket 88 attached thereto vand the double sprocket 89 attached to sprocket 89 then drives, through the chain 96, the single sprocket attached to the pinch roll 83.

Guiding system Thus, between driven pinch roll 80 and bottom rotary brush 3| is located a cast guide |00 to support the sheet traveling therebetween. Such a guide is parallel to pinch rolls 80-90' and suitably supported and bolted to brackets |0| cast integral with each of opposite roll housings l5. At spaced intervals across .the top face of said 'guides are grooves which hold short, longitudinally extending wearing strips |02 of bronze or the like. The sheets traveling thereover contact these replaceable wearing strips.

A bottom guide |03, similarly constructed, arranged and supported, rests on integral brackets |06 'of roll housings 23 and serves to support the sheet between the lower rotary brush 33 and the pinch roll 82.

Parallel to and between driven pinch rolls 82 and 83 and supported on integral brackets |05 attached to the roll housing 23 is another bottom guide |06 which carries longitudinally extending wearing strips |01 replaceably mounted in grooves on the top side thereof. These wearing strips are longer than those previously described and are curved downwardly as they approach the pinch roll 8,2 to prevent the incoming sheet material from passing therebeneath.

Another bottom guide |08 may be placed between the rotary brush 93 and the guide |03. This guide "also extends transversely of the machine and carries removableinserts |09 of wear resistant metal. Such a guide, however, is caused to reciprocate in unison with the movement of the B set of rotary brushes, such a movement being accomplished by attaching its ends to lugs `brush arms 31 and 38.-

Connecting links Hl are also attached to lugs H0, the other ends of which reciprocate in horizontal guide arm bearings ||2 attached between brush housing -22 and roll housing 23 by bolts 24. This guide, therefore, is caused to move slightly forward' and upward to not only clear brush 33 as it swings in and out of contact with the underside f a sheet being cleaned but also to prevent any appreciable downward bending of the sheet as it clears a top guide |2| above and adjacent the rotary brush 38.

Spanning the space between the rotary brushes 3i and 39 and on either side of the pinch roll 8| are located bottom guides ||3 and IM. These guides extend transversely of the apparatus and parallel tothe top rotary brushes 30 and 32, respectively. These guides H3 .and H8 are mounted on respective brackets I i5 and H6 which are integral with the roll housings '20. The tops of these guides are substantially ilat and lie in a plane immediately below the" center line of sheet travel, the ends o f said guide tops curving downwardly slightly to prevent the sheet from passing therebeneath.

As the rotary brush 30 contacts and presses against the top of `asheet passing thereunder,

the flat top section of the guide I|3 prevents the sheet from buckling or bending under the high pressure and scrubbing action. In a similar manner the top of the guide ||4 braces and holds the sheet from buckling or bending as it is scrubbed under pressure by the rotary brush 32.

The top guides consist primarily of two similarly constructed and arranged guides |20 and |2| which are parallel to and immediately above the rotary brushes 3| and 33, respectively. These guides |20 and |2| are respectively supported on brackets |23 and |24 cast integrally with the rotary brush housings |1 and 22.

These fixed top guides both carry removable rectangular bronze or similar wear resistant metal inserts |22 which, together with the guide proper, brace the-top side of the sheet material as the rotary brushes therebeneath scrub. said sheets under variable pressure. Thus the bending or buckling of the sheet is prevented in a like manner to the bracing of the bottom of the sheet by the bottom guides ||3 and ||4.

Parallel and-between the top pinch rolls 82 and 83 is a guide |25 which carries atV spaced intervals removable wear resistant inserts |26, said inserts being of a construction similar to the wear resistant inserts |01 on the bottom guide |06` but in staggered relation thereto. The inserts |26 are turned upward at the end which faces the oncoming sheet so as to prevent the sheet from passing thereover. In fact, the top guide |25 is the reversal of the guide |06 therebeneath.

Spray system Extending along the one side of the apparatus,

` parallel to each other and above and below the center line of the sheets travel, are pipes |30 and |3| suitably connected at one end to a main feeder pipe |32 and closed at the opposite end by caps |33. From pipes |30|3| are short vertical extension pipes |308 and |3| which are of varying lengths to suit the desired positioning of the transversely extending spray pipes proper connected thereto by ells |34.

While these transversespray pipes maybe readily guide |20. Likewise constructed and arranged is vtransverse spray pipe |32 which cleans the topof the sheet just before it enters between therotary brush 32 and the bottom guide ||4.

Other top spray pipes are |38 and |39 which` cleanse the top of the sheet as it emerges from the brush 32, guide ||4 and pinch rolls 82-82' respectively, the direction of spray in these two cases being; however, opposite to direction of sheet travel. i

A transverse-spraypipe |40 directs its spray.

against the bottom of the sheet against its direction of travel as said-sheet emerges from between the brush roll 3| and the top guide |26,

while a spray pipe |4| is similarly constructed Operating control system The operating control system causes the two sets of rotary brushes A and B to be reciprocated so as to enter into or be out of contact with the sheet material passing therebetween.

Such a reciprocation is accomplished by apparatus (disclosed above under the heading Rotary brush system) connected `to a motor |50, which is mounted on a cover frame |5| which rests on top of the roll and brush housings and covers the entire top of the machine.

'I'he apparatus which interconnects the motor |50 and the` connecting fork 68 comprises a crank arm |52 which joins the connecting fork 68 with the shaft |53 of the worm gear reducer |54, said shaft carrying at its other end a shaft extension on which is mounted a gear |55. This gear |55 drives a companion gear |56 which in turn rotates a central shaft incorporated in a 180-4 segment limit switch |51.

At right angles to the gear reducer shaft |53 and interconnected thereto is a shaft |58 which connects the motor |50 with the gear reducer |54 through a coupling |59. Interposed between the coupling |59 and motor |50 is a magnetic brake |60.

The proper consequent reciprocation of the two sets of brushes A and B through the connecting fork 68 is caused by -suitable electrical connections between the motor |50, 180 segmental switch |51 and triggers |10 and |80.

The trigger is suitably and rotatably mounted on the shaft |1| at the entrance end of the apparatus. A sheet entering the machine depresses said trigger, causing the limit switch |12 (through leverage |13). to operate a motor |50 which in rotating turns the crank arm |52 sufficiently to cause the A set of brushes to contact the sheet. The crank. arm movement is limited to 180 by the segment switch |51 which, -when 180 cycle of the crank arm is completed, cuts oif the motor |50 and applies the magnetic brake |60 which grips the shaft |58 andstops the reciprocating action.

As previously mentioned, the longitudinal screws 66 so connect the two pairs of brushes A and B that when the A setof brushes (30 and 3|) are contacting the sheet, the B set of brushes (32 and 33) are out ofcontact.

This condition exists until the sheet contacts a second trigger |80 located between pinch rolls 82'-82 and the upper and lower guides |2| and |03 respectively. Upon such a contact the sheet lifts said second trigger and throughv suitable leverage |8| causes a limit switch |82 to operate the motorl|50 which again turns 180 so as to bring the second set of brushes kiB'into contact with the advancing sheet and at the same time cause the first set of brushes A to be retracted i away from the center line of sheet travel.

The magnetic brake |60, together with the 180 segmental switch |51, are common expedients to prevent the overrunning of brush arm movement, the release of said brake from the shaft lss taking effect as soon as a circuit between either of the limit switches |121 or |82 is completed, and the gripping action taking place as soon as seg- 1 ments of the switch |51 have traveled 180.

Only one such trigger switch need be used and the leverage system of such triggers may be replaced with a simple electrically operated trigger if so desired without departing from the scope of the invention.

The wiring diagram The diagram in Figure 6 is greatly simpliiied. It shows power lines 200 and 20| and the various limit switches are shown as they are when the scrubber stand B is closed and the stand A is open. Each of the limit switches may be considered as having an upper and a lower set of contacts.

When a sheet operates the switch |12 its upper contacts are opened and its lower contacts are closed, which completes a circuit from line 200', through line 202, the solenoid of a relay 203 and through line 204 to the line 20|. This closes the contacts of this relay and starts the motor |50 which rotates until the limit switch |51 opens its bottom contacts, due to 180 rotation, and breaks the circuit through the line 202.

'Ihe top contacts of the limit switch |51 are now closed, so the closing of the top contacts of the switch |82 by passage of the sheet closes a circuit through a line 205 and energizes the solenoid of a relay 206. This closes the contacts of this relay and energizes the motor |50 until the top contacts of the switch |511 are again opened by '180 rotation of this switchs cam.

The contacts of the relays are in series with a line 20i that connects the motor |50 and the solenoid of the brake |60 to the lines 200 and 20|.

General operation To summarize the foregoing description the following typical operation of the apparatus fully illustrates the principle involved.

With the sprays operating and the pinch rolls rotating tocarry sheet material from 4the entrance to exit end of the machine, thin gaged and possibly brittle sheet S is singly fed into the apparatus between the pinch rolls 80-80'.

This action, partially and diagrammatically shown in Figure 7, causes the trigger |10 to be depressed, which in turn causes the operating control system to move the connecting fork 68 from left to right, said movement causing the set or unit of rotary brushes A to swing into contact with the oncoming sheet. This set or unit of brushes A rotates in the direction of the sheets travel and thus contacts the front end of the sheet in such a manner that it is not opposed or resisted by the scrubbing action of the brushes. f Such action prevents tearing and bending of sheets which otherwise would be badly damaged. The scrubbing action of the brushes may be varied in intensity or pressure; in any event the top and bottom guides, as previously described, prevent buckling of the sheet through their bracing action.

In the illustrated machine the two sets or umts v sheet S and causes thesecond or B set of brushes 32 and 33 to make contact with the sheet (Figures 8 and 9).

The rotation of this latter set or unit of brushes Bis equal to but in the opposite direction to that of the rst named set of brushes. Thus, the rear half of the sheet is scrubbed both top and bottom in such manner that when the rear of said sheet passes between the rotary brushes 32 and 33 the latter do not oppose or resist the end of the edge of the sheet.

Thus, the front end or half of the forward moving sheet S is scrubbed in a direction equal to the direction of the moving sheet while the rear end or half of the same sheet is scrubbed in a direction opposite to its direction of travel. In other words, the scrubbers always scrub away from the leading and trailing edges of the sheets.

The chain drive for the pinch rolls 80 to 83 inclusive may be covered by suitable guards while guards may also cover the chain drive and gears incidental to the rotary brush drive.

While I have shown and described a speciiic embodiment of my invention it will be understood that I do not wish to be limited exactly thereto, since various modifications may be madewithout departing from the scope of my invention.

I claim:

1. A sheet scrubbing machine including the combination of at least two pairs of driven rotary scrubbers and means for mounting and rotating said scrubbers so that either pair may contact the sides of a lengthwise passing sheet while the other pair isfree from contact therewith.

2. A sheet scrubbing machine including the combination of at least two oppositely driven rotary scrubbers, means for mounting said scrubbers so that either may contact the same side of an edgewisedly passing sheet while the other is free from contact therewith, and means responsive to movement of said passing sheet for automatically causing said scrubbers to alternately contact the same side of said sheet so that at least the leading and trailing edge portions of the same are contacted only by Whichever one of said scrubbers is driven to rotate away therefrom.

3. A sheet scrubbing machine including the combination of means for horizontally feeding a sheet to be scrubbed, at least two oppositely driven upper rotary scrubbers and at least two oppositely driven lower rotary scrubbers for respectively scrubbing the top and bottom sides of said sheet, means for mounting said upper scrubbers so that either may contact the upper side of said sheet while the other is free from the same and for also similarly mounting said lower scrubbers respecting the bottom side of said sheet, and means responsive to movement of said sheet for automatically causing said upper and lower scrubbers to respectively alternately contact said sides of said sheet so that at least the leading and trailing edge portions of the same are contacted only by those of said scrubbers which are driven to rotate away therefrom.

4. A sheet scrubbing machine including the combination of at least twounits of spaced parallel scrubbers arranged in tandem parallel relationship, ineans for driving the scrubbers of each of said units in respectively opposite scrubbing directions, means for feeding a sheet to be scrubbed successively between the scrubbers of .said units in a horizontal position, and means for alternately rocking said units during the passage of said sheet therethrough.

5. A sheet scrubbing' machine including the combination of atleast two units of spaced parallel` scrubbers arranged in tandem parallel relationship, means for driving the scrubbers of each of said units in respectively oppilsite scrubbing directions, means for feeding a Sheet to be said units in ahorizontal position, means responsive'to movement of said sheet for automatically alternately rocking said units into scrubbing contact with said sheet so that at least the leading and trailing end portions of the latter are contacted only by the -scrubbers of whichever one of said umts is driven by the first named means in a scrubbing direction away therefrom, and supports arranged above and below said sheets at positions opposite said scrubbers when the latter contact said sheet due to rocking of said units.

6. A sheet scrubbing machine including the combination of at least two units of spaced parallel'scrubbers arranged in tandem parallel relationship, means for driving the scrubbers of each of said units in respectively opposite scrubbing directions, means for feeding a sheet to be scrubbed successively between the scrubbers of said units in a. horizontal position, means responsive to movement of said sheet for automatically alternately rocking said units into scrubbing contact with said sheet so that at least the leading and trailing end portions of the latter are contacted only by the scrubbers oi' whichever one of said units is driven by the iirst named means in a scrubbing direction away therefrom, supports arranged above and below said sheets at positions opposite said scrubbers when the latter contact 2,095,697 .scrubbed successively between the scrubbers of said sheet due to rocking oi' said units, the iirst named means driving the .last one of said units through which said sheet passes in a scrubbing direction towards its leading edge portion whereby it is not rocked into scrubbing contact by the third named means until after said leading edge portion has passed, a movable guide arranged close to the lower scrubber of the last named unit and means for moving said guide from the path of said lower scrubber when said last named unit is rocked intocontact with said sheet by the third named means.

7. A sheet scrubbing machine including the combination of rotary scrubbing means andA means for controllingsaid scrubbing means so that said scrubbing means rotatively scrubs both sides of a sheet away from both the leading and trailing end portions of said sheet fed lengthwise past the same.

8. A method of scrubbing the surface of at sheet materials which includes the steps of moving the sheet longitudinally of itself, scrubbing the leading end portion of said sheet material in the same direction as its longitudinal travel and scrubbing the trailing end portion of said sheet material in the opposite direction to its longitudinal travel.

OLAF M. HAMMER.

Images