US3103304A

US3103304A - Fiber-breaker for fiber-plastic depositor

Info

Publication number: US3103304A
Application number: US769365A
Authority: US
Inventors: John J Nawalanic
Original assignee: Ibis Enterprises Ltd
Current assignee: Ibis Enterprises Ltd
Priority date: 1958-10-24
Filing date: 1958-10-24
Publication date: 1963-09-10
Anticipated expiration: 1980-09-10

Description

. Sept. 10, 1963 J. NAWALANIC 3,103,304

FIBER4BREAKER FOR FIBER-PLASTIC DEPOSITOR Filed Oct. 24. 1958 3 Sheets-Sheet 1 INVENTOR. JOHA/J. NAWALAN/C ATTOEA/[VS Sept'. 10, 1963 J. J. NAWALANIC 3,103,304

FIBER-BREAKER FOR FIBER-PLASTIC DEPOSITOR Filed Oct. 24, 1958 3 Sheets-Sheet 2 INVEN TOR. Jay/v J. NA WA; A Al/C @Afu, z? 444 Sept. 10, 1963 J. J. NAWALANIC 3,103,304

FIBER-BREAKER FOR FIBER-PLASTIC DEPOSITOR 5 Sheets-Sheet 3' Filed Oct. 24, 1958 I I N VEN TOR. JOHN J NA WALA N/C BY w/i/'gfitdu 16m ATTOEA/EYS United States Patent 3,103,304 FIBER-BREAKER FOR FIBER-PLASTIC DEPGSITGR John J. Nawalanic, Cleveland, Ulric, assignor, by mesne assignments, to Ibis Enterprises Limited, Hamilton, Bermuda, a body corporate of Bermuda Filed Get. 24, 1953, Ser- No. 769,365 Claims. (Cl. 225-4) This invention rel-ates to improvements in a fiberbreaker for a fiber-plastic depositor.

One of the objects of the present invention is to provide an improved method and apparatus for breaking continuous lengths of fiber into shorter lengths.

Another object of the present invention is to provide a novel cooperation between a breaking roller and a cooperating back-up roller having a resilient exterior cover arranged to break continuous lengths of fiber into shorter lengths at the point of tan-gency of the two cooperating rollers while the rollers are in rolling contact with each other, so that the resilient coating of the back-uproller aids in throwing the broken fibers away from the point of tangency on the discharge side of the rollers.

Other points of invention reside in the critical amount of compression of the resilient cover of the backup roller at the point of tan-gency with the breaker roller and the critical length of projection of the breaking blades radially outside of the periphery of the breaking roller.

Another object of the present invention resides in a novel arrangement of the fiber breaking apparatus wherein it is suspended from a single point of support from a handle or holding frame.

A further object of the present invention is to provide novel means for supporting a drive motor in cantilever fashion from the driven back-up: roller and its supporting brackets.

Another object of the invention is the provision of a novel structure of the breaker roller whereby standard safety razor blades may be quickly assembled or disassembled from the roller, this structure involving a minimum number of parts and being very eflicient for quick change of blades.

A further object of the present invention resides in a novel means for mounting the breaking roller in the sup porting brackets for quick disassembly.

Still a further object of the invention resides in the combination of hand feed roller just ahead of the breaking and back-up rollers, in combination with a combined roving guide and brake for the hand feed roller.

Other objects and advantages of the present invention will be apparent from the accompanying drawings and description and the essential features will be set forth in the appended claims.

In the drawings,

FIG. 1 is a front elevational view of one embodiment of my invention, this being taken at the discharge side of the apparatus and being broken away in parts to show the construction ofthe back-up roll and its driving mechanism;

FIG. 2 is a transverse sectional view of the same taken along the line-2-2 of FIG. 1;

FIG. 2A is a diagrammatic view, greatly enlarged, of a portion of FIG. 2 taken at the point of tangency between the breaking roll and the back-up roll;

FIG. 3 is an end elevational view of the device of FIG. 2 taken from the position of the line 33'of FIG. 1;

FIG. 4 is a fragmental end elevational view similar to FIG. 3 but showing a modified embodiment of the releasable bearing cap which holds the bearing for the breaking roll;

3 ,1 @3'93 Patented Sept. 10, l 963 ice FIG. 5 is a fragmental elevational view of the device of FIG. 4 taken along the line 55 thereof; while FIG. 6 is a transverse sectional view, partly in section, taken along the line 6-6 of FIG. 2.

I have chosen to illustrate my improved fiber-breaker as adapted [for use in apparatus for forming a fiber reinforced plastic article disclosed and claimed in United States Patent No. 2,787,314, granted April 2, 1957, to David 'F. Anderson. It should be understood, however, that my improved fiber-breaker may be used for its intended purpose whether or not it is associated with the resin spraying apparatus of the above-mentioned Anderson patent.

For simplicity of expression, the rotatable roll which carries a plurality of blades will hereinafter be referred to as the breaking roll because the action is more a break ing of the fiber than a cutting action.

The essential parts or" the apparatus about to be described are the above-mentioned breaking roll and a coacting back-up roll against which the blades operate. A suitable frame must be provided to rotatably support these two rolls and in the present disclosure, this comprises two generally parallel plates, 10* and 11, which serve as brackets to support the rest of the lcoacting apparatus. In order to support my improved device so that the fiberbreaker may be disposed intermediate two resin sprays, I have shown a handle bar 12 which is supplied at opposite ends with handles 13 to be gripped by the operator. At its mid point, the handle bar is flattened as indicated at 14 and, at that point, two screws 15 pass through the flattened portion of the handle bar 12 and are threaded into the upper end of the bracket 10 as clearly shownin FIG. 2. At the same time, these two screws hold a cap 16 in place against the bracket 10 to embrace an air pipe 17 intended to supply air to two resin spray heads on opposite sides of the fiber-breaker herein disclosed. The bracket 11 is notched at its upper end as indicated at 11a to snugly embrace the lower side of the pipe 17. Three

rigid spacer members

18, 19 and 20 are spaced between the

bracket plates

10 and 11 and held rigidly to these'brackets by means of screws 21 whose heads bear on the outer faces of

plates

10 and 11 and are threaded into the ends of the spacer members. This provides a rigid framework for holding the coacting rollers about to be described.

The breaking roll, as best seen in FIGS. 1, 2 and 6, comprises a smooth cylindrical body 22, having a plurality of radially extending slots running the entire length of the body and opening toward the outer periphery of the body and adapted to receive standard safety razor blades. Where the blades are approximately 0.0105 inch to 0.0120 inch thick, I prefer to make the radial slots approximately 0.013 inch wide. These blades, indicated at 23, may be spaced as desired around the circumference of the cylindrical body 22 in order to break the fibers into desired lengths. In the drawings, I have shown these blades evenly spaced around the circumference but they might be unevenly spaced if it were desired to have some fibers shorter than others. Referring to FIG. 2, it will be noted that the slots receiving the blades 23 terminate short of a bore 24 extending axially through the body 22 from end to end. A shaft 25 is a tight lit in this bore and extends beyond the body 22 at opposite ends thereof to there receive bearings 26 which are a press lit on the shaft 25. These bearings are held in place by screws 27 threaded axially into the shaft 25. Preferably, but not necessarily, the blades 23 are beveled at opposite ends of the body 22 as seen at 23:: in FIGS. 1 and 6, and the blades when assembled in the body 22 are held in position by end caps 28 which are annular in form and have inwardly tapered edge flanges 28a which overlie the ends of the blades 23 and coact with the beveled corners 23a to hold the blades firmly in place. These end caps 28 are held in place by the screws 27 and it will be obvious that the structure is readily disassembled for renewal of the blades 23 by simply removing one or both of the screws 27, then removing a bearing 26 and an end cap 28 to give access to the blades 23.

When the breaking roller is assembled in the holding frame, each of the bearings 26 rests in a suitable recess in the

bracket plates

10 and 11 as clearly shown in FIG. 6. As seen in FIGS. 2 and 3, approximately half of each of the bearings 26 is received in the recess in

plate

10 or 11 as the case may be, and the other half of the bearing is received in a suitable recess and snugly held in place by a bearing cap 29, each of which is held in place by screws 30 which pass through the bearing cap and are threaded into the

bracket plates

10 or 11 as the case may be. It is thus very easy to loosen the screws 30 to remove the bearing caps 29 so that the entire assembly of FIG. 6, between the screws 27, may be quickly removed to change breaking rollers or to change blades.

An alternative arrangement of the bearing caps is shown in FIGS. 4 and where the bearing cap 29' is provided with a hinge leaf 31 which is received in a suitable slot in the bracket plate 11 and pivotally mounted on a screw 32. Thus the cap 29' is always connected to the bracket plate 11' so that it is not lost. The free end of the bearing cap is held in assembled position by screw 33 threaded into the member 11'. In this position, the recess 34 in the bearing cap firmly holds the bearing 26 in position. Other than as described in this paragraph, the embodiment of FIGS. 4 and 5 operates in the same manner as that described in connection with FIGS. 1, 2 and 3.

The back-up roll 35, as clearly seen in FIGS. 1 and 2, comprises a rigid annular body 36 which may be of any suitable material, but preferably is made of aluminum for the elimination of static and for the better conduct-ion of heat. Part of the aluminum may be cut away as indicated at 37 to eliminate weight. To the outside of the body 35 a resilient cover is attached. In the drawings, I show a circular band 38 of suitable metal to which is bonded an annular ring of resilient material 39, preferably having the resilience of rubber of 45 to 55 durom-eter when breaking ordinary glass fiber but which may be slightly harder when breaking softer fibers as hereinafter discussed. I find that I get good results in the embodiment hereinafter described more in detail if the ring 39 is approximately /2 inch thick in the radial direction. The resilient sleeve 39, in the embodiment disclosed, measures approximately 1 /8 inches axially or somewhere near the approximate length of the blade-s 23 between their end caps 28. It is obvious that the axial dimension of the resilient cover 39 need only be wide enough to break the number of strands of fiber roving fed to the device. At one side of the back-up roller, the ring 38 abuts against a flange 36a extending radially outwardly from the body 36. At the opposite side, screws 40, threaded into the body 36, have heads which radially enter into the ring 38 and engage against the ring 38 to hold it firmly against the flange 36a and to hold it against turning relative to the body 36. The body 36 has a central through bore 41 which provides a shoulder 42 at one end against which a friction reducing ball bearing 43 is a press fit. At the opposite end a shoulder or recess 44 receives a slotted driving disk 45 which is also a press fit at that end. A pintle 46 has its inner end 46a of a diameter to snugly enter the bearing 43. The pintle has an intermediate diameter 46b which acts as a spacer between the back-up roller and the bracket plate 11. A still larger diameter 460 of the pintle is a snug fit in the bracket plate 11. An enlarged head 46d on the pintle bears against the outer face of the plate 11 and the pintle pin is fixed relative to the plate 11 by means of two screws 47.

Means is provided to drive the breaking roll and the back-up roll in a direction to feed continuous lengths of fiber between them from left to right as viewed in FIG. 2. In other words, the breaking roll travels in a counterclockwise direction and the back-up roll in a clockwise direction as viewed in FIG. 2 and as indicated by arrows in that view. Preferably, one only of these rolls is driven and the frictional contact between them is depended upon to drive the other. In the present embodiment, the back-up roll is driven by means of a standard quarter inch drill electric motor 47 It is obvious that other driving means might be utilized.

A novel construction is here shown for supporting the motor 47 from the

bracket plates

10 and 11. Referring to FIG. 1, the pintle 46 supporting bearing 43 at one side of the roll 39 has already been described. At the opposite side of the roll, namely, toward the motor 47', the final output shaft 48 of the electric motor passes through a suitable opening in bracket plate 10 and through a ball bearing 49 suitably held in plate 10. The free end of shaft 48 has secured to it a driving dog 50 which is in the nature of one part of a jaw clutch. The member '50 is suitably secured to shaft 48 'as for instance by means of the set screw 51. The jaw clutch comprises two axially extending projections 50a diametrically opposite each other and adapted to engage in one or the other of a pair of grooves 45a in the member 45 previously described. These grooves are clearly shown in FIG. 2. It results from this construction that the roll 39 is readily removable from the driving connection 50 by merely removing the pintle 46 and plate 11 after which the roller 39 may be moved in an axial direction toward the left as viewed in FIG. 1 to disengage the jaw clutch members 50a and 45a.

The structure above described results in the support of the motor 47 in a cantilever fashion from the

bracket plates

10 and 11. It will be note-d in FIG. 1 that the weight of motor 47' is exerted downwardly on bracket plate 10 and upwardly on bracket plate 11 which results in pressing the recess 11a of bracket plate 11 more firmly upwardly against the pipe 17.

In the present embodiment, the roll 39 is approximately 3 inches in outside diameter and the breaking roll 22 is approximately 1%. inches in outside diameter. In this successful embodiment of my invention the two rollers are assembled so that there is an interference at their point of tangency so as to compress the resilient cover 39 approximately 0.040 inch inwardly from its true unstressed circumferential position.

Referring now to FIG. 2A, I have illustrated the action that takes place when a continuous length of fiber or roving, as indicated by the broken line 52, is fed from left to right between

rolls

22 and 39 at their point of tangency. It will be understood that the diagram is enlarged and distorted for the purpose of illustrating the principle involved. Because of the circumferential interference between the coacting rollers, mentioned above, the resilient cover 39 of the roller 35 is engaged between the outer surface of the cylindrical body 22 between the points X and Y, holding the fiber roving firmly between these points. Then, the blade 23, which preferably extends between 0.043 inch and 0.048 inch radially outwardly beyond the cylindrical body 22, will press into the resilient material 39 as indicated in FIG. 2A and sever the fiber roving at that point. The blade 23 has a sharp edge which embeds itself slightly in the resilient cover 39 and in so doing stretches the length of fiber between the points X and Y until it is actually broken by the blade. The resilient, rubber-like material displaced between the points X and Y moves over toward the right as viewed in FIG. 2A, in the direction of roll travel, to produce a wave indicated at 39a. When the device is operating, this appears at 39a as a standing wave with visual persistence. However, due to the fact that the blades 23 intermittently enter the pockets in the resilient cover 39 [as illustrated in FIG. 2A, I believe that the wave 39a is actually formed intermittently or at least exaggerated every time one of the blades 23 occupies the position shown in FIG. 2A. In actual practice, the resilient material, earlier bowed downwardly by knife 23, snaps radially outwardly when it reaches the zone 39a to kick the broken fibers upwardly and outwardly as they leave the point of tangency between the breaking roll and the back-up roll. This is indicated at 52a in FIG. 2 and actually causes the broken fibers to be thrown out far enough to be hit 'by resin sprayed from guns which are supported from the pipe 17 at either side of the breaking and back-up rolls with converging sprays as taught in the above mentioned Anderson patent so that the two resin sprays and the stream of broken fibers 52a join in a common mixing zone.

I have mentioned the conditions for successful breaking of ordinary glass roving as included a standard Schick or Pal safety razor blade having a single sharp edge extending between .043 inch and .048 inch radially beyond the cylindrical body 22 of the breaking roll and coacting with a resilient cover 39 having a resiliency between 45 and 55 durometer rubber hardness. Slightly changed conditions are necessary to break sorter fibers which would include a glass roving with a siliconetype binder sold under the trade name Garan or fibers of nylon, rayon and cotton. For these softer fibers a resilient cover 39 should preferably have a resiliency of rubber of 65 'durometer .and the blade 23 should extend beyond the cylindrical body 22 approximately 0.055 inch which corresponds to a Schaefer safety razor blade with one sharp edge.

Means is provided for guiding and feeding continuous lengths of fiber roving to the breaking and back-up rolls. The novel means shown for this purpose comprises a rubber covered roll 53 journaled .at its opposite ends in the bracket plates and 11 and provided with a knurled knob 54 on the outside of plate 11 which is rigidly connected with the roller 53 so as to turn the same by hand. Coacting with the roller '53 is a combined roving guide and brake which comprises the member 54 L-shape in section and extending substantially the full width of the roll 53. This guide has depending ears 55 at each end thereof which are perforated so as to embrace the spacer member 20 as clearly shown in FIGS. 1 and 2. One or more through openings 56 are provided in the shorter leg of the member 54 so that a continuous length of roving may pass through an opening 56, between roller 53 and the longer leg of member 54 and then to the point of tangency between the breaking roll and the back-up roll.

Means is provided to bias the member 54 to the full line position shown in FIG. 2 where the longer leg of the member 54 is lightly pressed against the bottom of roller 53. The means here shown for this purpose comprises a fairly stiff closely wound spring 57 which has one end passing through a diametr-ioal opening in the spacer member 20 and held in position by means of a screw 53. The free end of the spring presses against the under-side of the longer leg of the member 54 so as to urge it in a counterclockwise direction as shown in FIG. 2. When it is desired to thread a new length of roving through the device, the end of the roving is passed through the opening 56 and between the roll 53 and the longer leg of the member 54. The knob 54' is then turned in the proper direction to feed the roving 52 from left to right as seen in FIG. 2. This causes the member 54 to move toward the broken line position indicated in FIG. 2. The spring pressed member 54 thus puts a slight drag on the roving 52 as it is fed toward the breaking device which aids in the orderly process of breaking.

It also holds the roving between the member 54 and roller 53 at the termination of a breaking operation so that the roving does not pull back out of the guide opening 56 so as to unthread the device.

Preferably, a control switch actuator 59 is located on the handle connected by means not shown with the motor 47' for starting and stopping the motor. One has, therefore, only to assemble the parts in the manner herein disclosed, feed a continuous length of fiber through the opening 56, under the roller 53 and into the bite between the breaking and back-up rolls and then push the switch actuator 59 to operate my fiber-breaking device. This may be done with or without the cooperation of the synthetic resin sprays, whose function is disclosed and claimed in the above mentioned Anderson patent.

What is claimed is:

l. A fiber-breaking device comprising a frame, coacting breaking and back-up rolls rotatably mounted in said frame and in frictional engagement through said fiber with each other at a zone of tangency, said breaking roll comprising a generally cylindrical body having a substantially rigid peripheral surface and having at lest one blade rigidly mounted in said body and extending radially outwardly beyond said surface of said body a short distance, said back-up roll having an outermost cover having a resiliency corresponding to rubber of ap proximately 45 to 55 durorneter, said rolls having through said fiber a slight interference at said zone of tangency so that said breaking roll engages and deforms through said fiber the rubber cover of said back-up roll along a short circumferential distance, and means for driving at least one of said rolls in a manner to carry continuous lengths of fiber between said rolls for breaking said fibers and subsequently kicking said lengths off said rolls. 7

2. The combination of claim 1, wherein said blade extends beyond said body a distance between approximately 0.043 inch and approximately 0.055 inch, and said interference between said rolls is approximately 0.040 inch in radial extent.

3. A fiber-breaking device comprising two generally parallel frame bracket members, coacting breaking and back-up rolls rotatably mounted in said bracket members and in a mutual driving engagement at a zone of tangency between them, spacer members rigidly connected between inner faces of said bracket members by means including securing members accessible from outside one of said bracket members for permitting relative separation of said members along the axis of said rolls, said rotatable mounting for said breaking roll including hearings in said bracket members and bearing caps partially embracing said bearings and removable in planes at right angles to the axis of said breaking roll and secured to said bracket members, and said rotatable mounting for said back-up roll including a pin and connecting means on said pin and back-up roll permitting relative rotation between said pin and roll when engaged and permitting said pin to be engaged with or disengaged from said roll solely by axially moving said pin relative to said back-up roll, said pin extending through and being axially removable from the outside of said one bracket member, whereby said one bracket member and said rolls may be quickly disassembled from the other of said bracket members remaining secured to said spacer members.

4. The combination of claim 3 including drive means for said back-up roll including a shaft passing through the other of said bracket members axially of said back-up roll, and a jaw clutch between said shaft and said backup roll disengaged solely by axial movement of said backup roll away from said shaft after disassembly of said one bracket member.

5. The combination of claim 4 including means for suspending said device from above and secured to said other bracket member only, said one bracket member engaging said last named means on the underside only thereof, and a motor operatively connected with said drive shaft on the outside of said other bracket member, whereby said motor is supported in cantilever fashion and urges said one bracket member against said last named means.

6. The combination of claim 3 including an idler guide roll rotatably mounted in said bracket members ahead of and axially parallel to said breaking and back-up rolls, an L-shape plate oscillatably mounted on one of said spacer members in front of said guide roll, one leg of said plate engaging against the underside of said guide roll, resilient means urging said one leg against said guide roll, the other leg of said plate being upstanding in front of said guide roll, and there being a fiber guide opening through said other leg of said plate, whereby movement of fiber through said guide opening tends to move said one leg away from said guide roll.

7. A fiber-breaking device comprising a frame, coacting breaking and back-up rolls rotatably mounted in said frame on parallel axes and substantially in engagement with each other through said fiber at a zone of tangency, said breaking roll comprising a generally cylindrical body having a substantially rigid peripheral surface with at least one blade rigidly mounted in said body and extending axially of said body and projecting radially beyond said surface on said body a short distance, said blade being approximately 0.0105 inch to 0.012 inch 1 thick and having its radially outermost edge sharpened, said back-up roll having a rubber-like outermost cover having a resiliency corresponding to rubber of approximately 45 to 65 durometer, and means for causing rotation of said rolls in a manner to carry lengths of fiber between said rolls, whereby said blade pushes into said cover and breaks said fibers there.

8. The combination of claim 7 wherein said blade projects radially beyond the peripheral surface of said body a distance of approximately 0.040 inch.

9. The method of breaking a continuous length of fiber into shorter lengths comprising feeding said continuous length of fiber between two rotatable rolls in peripheral engagement, holding said fiber firmly between said rolls at two points respectively on opposite sides of a circun ferential zone of engagement between them, simultaneously forcing said fiber between said two holding points radially away from one of said rolls until it breaks there, the other of said rolls having a resilient rubber-like cover, and forming a standing wave in the resilient cover of said other roll just downstream from said breaking point and thereby kicking shorter cut lengths of fiber radially away from the periphery of the other of said rolls immediately adjacent the zone of discharge of said shorter lengths from between said rolls.

10. A fiber-breaking device ing fiber glass roving, ing and back-up rolls adapted for breakcomprising a frame, coacting breakrotatably mounted in said frame on &

parallel axes and substantially in frictional engagement with each other through said fiber at a zone of tangency, said breaking roll being of substantially smaller diameter than said back-up roll and comprising a generally cylindrical body having asubstantially rigid peripheral surface with at least one blade rigidly mounted in said body and extending axially of said body and projecting radially outwardly beyond said surface on said body a short distance, said blade being approximately 0.0105 inch to 0.012 inch thick and having its radially outermost edge sharpened, said back-up roll having a rubber-like outermost cover having a resiliency corresponding to rubber of approximately to durometer, said rolls having a slight interference at said zone of tangency so that said breaking roll engages and deforms the rubber cover of said back-up roll along a short circumferential distance, said blade projecting radially beyond the peripheral surface of said body a distance between approximately 0.043 inch and approximately 0.055 inch, and said interference between said rolls being at least approximately 0.040 inch in radial extent, and means for causing rotation of said rolls in a manner to carry continuous lengths of fiber between said rolls so that said rubber-like cover holds said fiber firmly between said rolls at two points respectively on opposite sides of a circumferential zone of engagement between them, said blade pushes into said rubber-like cover and simultaneously forces said fiber between said two holding points radially away from said breaking roll until it breaks there, and said resilient cover subsequently forms a standing wave just downstream from said breaking point and thereby kicking in a well distributed pattern shorter lengths of fiber radially away from the periphery of said rolls immediately adjacent the zone of discharge of said shorter lengths from between said rolls.

References Cited in the file of this patent UNITED STATES PATENTS 244,845 Bowles July26, 1881 674,922 Koehl May 28, 1901 705,041 Copland July 22, 1902 1,180,309 Mid-gley Apr. 25, 1916 1,804,608 Hagemann May 12, 1931 2,252,733 S henman et a1. Aug. 19, 1941 2,297,877 De Bruen Oct. 6, 1942 2,472,662 King June 7, 1949 2,692,022 Horgan Oct. 19, 1954 2,714,250 Twedt Aug. 2, 1955 2,729,028 Slayter et a1. Jan. 3, 1956 2,783,839 Rugg Mar. 5, 1957 2,803,304 Kessler Aug. 20, 1957 3,003,235 Temple Oct. 10, 1961 3,011,257 Bamberger Dec. 5, 1961

Claims

1. A FIBER-BREAKING DEVICE COMPRISING A FRAME, COACTING BREAKING AND BACK-UP ROLLS ROTATABLY MOUNTED IN SAID FRAME AND IN FRICTIONAL ENGAGEMENT THROUGH SAID FIBER WITH EACH OTHER AT A ZONE OF TANGENCY, SAID BREAKING ROLL COMPRISING A GENERALLY CYLINDRICAL BODY HAVING A SUBSTANTIALLY RIGID PERIPHERAL SURFACE AND HAVING AT LEST ONE BLADE RIGIDLY MOUNTED IN SAID BODY AND EXTENDING RADIALLY OUTWARDLY BEYOND SAID SURFACE OF SAID BODY A SHORT DISTANCE, SAID BACK-UP ROLL HAVING AN OUTERMOST COVER HAVING A RESILIENCY CORRESPONDING TO RUBBER OF AP-