US3360210A - Waste stripper for label-making machines - Google Patents

Description

E. C. FRISBIE Dec. 26, 1967 WASTE STRIPPER FOR LABEL-MAKING MACHINES 4 Sheets-Sheet l Filed June 22, 1965 Dec. 26, 1967 E. c. FRISBIE WASTE STRIPPER FOR LABVELMAKING MACHINES Filed June 22, 1965 Dec. 26, 1967 E. c. FRISBIE 3,360,210

WASTE STRIPPER FOR LABEL-MAKING MACHINES Filed June 22, 1965 4 Sheets-Sheet 5 EDWARD C. FRISE/E 1N VENTOR 7' ORNE Y E. C. FRISBIE Dec. 26, 1967 4 Sheets-Sheet 4 Filed June 22, 1965 EDWARD C. FRISE/E INVENTOR BW MINNIE@ 6@ TTOEWEY United States Patent O 3,360,210 WASTE STRIPPER FOR LABEL-MAKING MACHINES Edward C. Frisbie, Oakland, NJ., assigner to Charles D. Ingraham & Sons, Inc., Nutley, NJ., a corporation of New Jersey Filed June 22, 1965, Ser. No. 465,991 5 Claims. (Cl. 242-65) ABSTRACT OF THE DISCLOSURE Apparatus for automatically stripping waste material from an intermittently moving backing strip carrying pressure-sensitive, adhesive labels and winding the strip of waste material on a roll. The roll is frictionally driven by a drive roll during movement of the backing strip and the Waste material strip passes over a spring-biased idler roller which is displaceable in a direction parallel to the movement of the 'backing strip in correspondence with Achanges in the tension of the waste material strip.

This invention -relates to a machine for making pressure-sensitive adhesive labels and more particularly to a waste stripper for automatically peeling the waste material from the backing strip after the individual labels have been die cut and winding the waste material on a rewind roll.

Labels of the type to which this invention is directed are made from a supply stock, or web, consisting of a sheet of paper coated with a pressure-sensitive adhesive and carried -by a backing strip made of glassine, or other material, from which the paper can be separated without loss of the adhesive. The web is supplied in roll form, passed through a label-making machine and then rewound into a roll. Generally, the web passes through the machine in an intermittent manner between a platen and a reciprocating die. When the web is stationary, the die is operated to cut through the paper, but not through the .backing strip, thereby forming a plurality of individual labels of desired configuration. After the individual labels have lbeen formed, it is necessary to remove the excess paper, or Waste material, from the backing strip, that is, all of the paper other than the labels. Thus, the rewound roll comprises the backing strip carrying only the labels.

The rewound roll is subsequently fed into other machines which apply printed matter to the individual labels and/ or automatically remove the labels from the backing strip and apply them to particular articles. On the other hand, certain label-making machines are provided with printers for applying the printed matter to the labels. In the latter case, the paper stock may be imprinted before or after the individual labels have been die cut.

In any case, it is necessary to remove t-he waste material in such manner as to maintain the original registry of the labels carried by the backing strip. This has been a problem which is not solved by waste strippers heretofore available and, consequently, a certain percentage of the finished labels are imperfect and must be scrapped.

A waste stripper made in accordance with this invention overcomes the shortcomings of prior such devices and- 3,360,210 Patented Dec. 26, 1967 An object of this invention is the provision of a waste stripper adjustably positionable on a label-making machine, which stripper operates in timed sequence with the intermittent advance of a strip of label stock through the machine.

An object of this invention is the provision of a waste stripper for attachment on a machine used to make pressure-sensitive adhesive labels carried by a backing strip, said waste stripper automatically removing, from the backing strip, the waste material remaining after the formation of the labels and winding such waste material into a roll.

An object of this invention is the provision of a waste stripper for automatica-ily stripping the waste material from a web passing through a label-making machine, said Waste stripper comprising `a roll on which the waste material is wound, intermittently operated means for frictionally driving the roll and a spring-biased idler roller positioned proximate to the web and over which the strip of waste material passes to the said roll, said idler roller I being spring-biased and movable in a direction parallel to the movement of the web in correspondence with changes in the tension of the waste material strip.

These and other objects and advantages of the invention will become apparent from the following description when taken with the accompanying drawings. It will be understood, however, that the drawings are for purposes of illustration and are not to be construed as defining the scope or limits of the invention, reference being had for the latter purpose to the claims appended hereto.

In the drawings wheein like refrence characters de- -note like parts in the several views:

FIGURE 1 is a side elevational View of a label-making machine including a waste stripper made in accordance with this invention and with the conventional machine components shown diagrammatically;

FIGURE 2 is a t-op plan view showing the label stock as it passes through the machine;

FIGURE 3 is an enlarged elevational view taken from the left side of the waste stripper (which side corresponds to that shown in FIGURE 1) and with a portion of the vertical mounting plate broken away; Y

FIGURE 4 is a similar view taken from the right side of the waste stripper;

FIGURE 5 is a similar view taken from the front of the waste stripper but with the forward idler roller and its mountings omitted;

`FIGURE 6 is a horizontal cross-sectional view taken along the line VII-VII of FIGURE l;

FIGURE 7 is a vertical cross-sectional view taken along the line VII--VII of FIGURE 5; and

FIGURE 8 is a schematic diagram of the circuit for controlling operation of the electromagnetic clutch.

Reference now is made to FIGURE 1, which is a` diagrammatic side elevation of a label-making machine having attached thereto a Waste stripper made in accordance with this invention. Such machine comprises a pair of spaced, parallel tracks, or ways, supported on a plurality of legs 10, only the forward way 11 being visible in this particular View. A supply roll 12, of the label stock, is rotatably positioned at one end of the machine while a rewind roll is positioned at the other end. The stock, or web 15, consists of paper having one surface coated with a pressure-sensitive adhesive and carried by a backing strip, the paper being of a grade and thickness desired for thel particular labels and the backing strip being glassine, wax paper, or the like, so that the paper adheres thereto to form the webbut yet is readily removable therefrom by a peeling action. As shown in FIGURE 1, the paper constitutes the upper portion of the web 15.

To condition the machine for operation, an end of the web is drawn by hand, between the fixed platen 16 and the label-forming die 17, between a pair of drive rollers 1-8, through the waste stripper made in accordance with this invention and identified by the numeral 19, and between a pair of tension rollers 20, and thence to the rewind roll. Except for the waste stripper, the other operating components of the machine are of conventional design and construction and, therefore, will be described only briefly. The operation of such components is effected by suitable mechanical couplings to a main drive shaft 2.1, such drive shaft being rotatably secured to the rear way and rotated continuously during machine operation by an electric motor, not shown. The drive rollers 18, generally covered by rubber or other suitable material, are rotated intermittently to pull the web 15 a predetermined extent along the platen 16. When the web is stationary, the die 17 is power driven toward the platen, thereby cutting through the upper paper portion of the web but not through the backing strip and forming a plurality of labels of desired configuration. For example, each operation of the die may form two labels 22 shown in FIGURE 2, which is a plan view of the web. After the die 17 has been moved out of engagement with the web, the drive rollers 18 again are rotated to advance the web. It will be apparent that the extent to which the web is advanced, during each operating cycle of the drive rollers, will depend upon the size and number of the labels to be formed upon each operation of the die. In any event, after several label-forming cycles, the paper portion lof the web which lies between the die and the waste stripper 19 (identified by the letter (L) in FIGURE 2), will be cut into a plurality of labels, which labels adhere to the backing strip.

The tension rollers 20 are continuously rotated by a separate electric motor 22 but the frictional pulling force exerted thereby upon the web is only suflicient to maintain the web taut to the left of the drive rollers 18 when the latter are stationary. IOn the other hand, when the drive rollers are rotating, the tension rollers 20 move the web through the waste stripper and toward the rewind roll 13. The rewind roll 13 may be rotated in timed sequence with the movement of the web, or alternatively, the rewind roll can be rotated by suitable friction means whereby the web is rewound smoothly even though it is moved intermittently through the machine.

With continued reference to FIGURE 1, the waste stripper comprises a forward idler roller 25, a rear idler roller 26, a waste roller 27 and a drive roller 28. At the beginning of machine operation, the operator peels the waste material from the web, in the region of the stripper, passes such waste strip 29 about the idler rollers 26 and 25, between the rollers 27 and 28, and attaches the end to the waste roller 27 as by means of a piece of adhesive tape. A more detailed description of the waste stripper is given hereinbelow. Sufiice to say, for the present, that the drive roller 28 is rotated during the time intervals when the web is advanced and that the waste roller is carried by a shaft which is slidably movable within aligned, vertical slots formed in the spaced, upper ends of the stripper, only the slot 30 being visible in FIGURE 1. Normally, then, the waste roller 27 is in surface contact with the drive roller 28, the latter having a roughened surface formed, for example, as by a sheet of emery paper cemented thereto. Thus, the waste roller 27 is rotated, frictionally, by the drive roller 28 and moves upwardly as the layer of waste material is built up thereon. Further the rear idler roller 2.6 is spring-biased and supported in such manner that it can move in either direction in a plane parallel to the web in response to changes in the tension of the waste material strip. The Waste stripper is positionable along the machine ways and is secured in a desired fixed position as by means of the bolts 31.

It will be apparent, then, that the portion of the web which has passed through the waste stripper will comprise only the individual labels carried by the backing strip. Such portion of the web is illustrated by the dimension (M) in FIGURE 2, in which figure the backing strip is identified by the numeral 33t.

Before passing on to a detailed description of the waste stripper, attention is directed to the wheel 34 carrying a peripheral shoe 35 having an arcuate length of some 180 degrees. By means of a suitable gearing arrangement, this wheel rotates continuously during machine operation and effects the closing and opening of the normallyopened contacts of a micro switch 36, which switch is secured in fixed position on the machine. Closure of the micro switch contacts energizes an electro-magnetic clutch associated with the drive roller 28 of the waste stripper so that the drive roller is rotated only during the time periods when the web is advanced along the machine.

Reference now is made to FIGURES 3-5 which are enlarged elevational views of the waste stripper with portions of the forward mounting plates broken away in FIGURES 3 and 4. FIGURE 3 is taken from the left side (corresponding to that shown in FIGURE 1), FIGURE 4 is taken from the right side and FIGURE 5 is taken from the front side, that is, looking in the direction of the web movement as shown in FIGURE l. The components of the stripper are carried by a pair of vertical mounting plates 40, 40', which span the ways 11, 11 and which are secured in fixed position to the corresponding ways by the bolts 31 and 31. Secured to the upper ends of these plates, as by the sets of bolts `42, 42', are bifurcated end pieces forming the aligned vertical slots 30, 30. The waste rewind roller 27 is secured to a shaft 43 which is slidable within the slots 30, 30, axial movement of the shaft being limited by the end nuts 44, 44 threaded thereon. The drive roller 28 also is secured to a shaft 45 passing through aligned bearing holes formed in the two mounting plates, said shaft having an end nut 46 threaded on an end and a bevel gear 47 secured to the other end.

Secured to the vertical front edges of the mounting plates 40, 40 are a pair of bearing blocks 50, 50 for the shaft of an additional idler roller 51. Secured to the inclined front edges of the mounting plates are a pair of rectangular blocks 52, 52 which are omitted from FIGURE 5 for clarity of disclosure. These blocks are of identical construction and only the construction of one such block will now be described with specific reference to FIGURE 3. A transverse slot is formed through the rectangular block 52 for receiving the square bearing block 53. Such block is adjustably positioned within the slot by means of an adjusting screw `54 threaded through a hole formed in the lower end of the block, which screw is retained in the set position by a locking nut 55. A compression spring 56 loosely encircles the shank por- `tion of a headed pin 57, which pin is slidable within a hole formed in the other end of the block 52. Thus, the bearing block 53 is spring-biased to the lright and can move within the slot in response to changes in the tension of the waste material strip 29, passing over the roller 25. This roller is secured to a reduced-diameter shaft having one end passing into a bore formed in the bearing block 53. The described arrangement can best be understood by reference to FIGURE 6, which shows the square bearing blocks 53, 53 passing through the slots of the respective rectangular blocks 52, 52 The idler roller 25, here shown broken away, is secured to the shaft 58 having its ends journalled in the bearing blocks 53, 53'.

Reverting back to FIGURES 3-5, the web 15 is supported by a horizontal plate 60 secured in fixed position to the two mounting plates and having a downwardly offset forward end serving as a guide lip. Seen through the broken away portion of the mounting plate 40, FIGURE 3, is the springbiased rear idler lroller 26, the furthermost end of which is rotatably and removably carried by a slide -blgock 61 disposed proximate to the inner surface of the other mounting plate 40. A first guide ypost 62,

secured in fixed position on the mounting plate 40', is

agarra@ provided with a clearance hole accommodating the rod 63 which has an end force-fitted into a hole formed in the slide block 61. A first compression spring 64 loosely encircles the rod 63 and is confined between the slide Iblock and the post 62. A second, l-onger rod 65 is slidable within a hole formed in a second guide post 66, `which also is secured in fixed position on the mounting plate 40'. The left end of the rod 65 is force-fitted into a hole formed in the slide block 61. A second compression spring 67 loosely encircles the rod 65 and is confined between the post 66 and an adjustable collar 68, which is secured in the desired position by a set screw, thereby to apply a predetermined compression to the spring 67. It will `be noted that the waste material strip 29 passes over the idler roller 26. Thus, as the tension on the waste material is increased, the idler roller 26 and the supporting guide block 61 lwill move to the right against the biasing force of the spring 67. Such movement of the idler roller 26 is axial of the web 15 -by reason of a similar assembly of the roller-supporting mechanism positioned proximate to the inner wall of the other mounting plate. Such mechanism is shown in FIGURE 4 with corresponding parts identified iby primed reference numbers. The two ends of the rods 65 and 65', which project beyond the respective guide posts 62, 62, have a transverse flat tie -bar 70 secured thereto, as by screws. v

The symmetrical construction and assembly of th spring-biased arrangement supporting the rear idler roller 26 of the lwaste stripper is shown in FIGURE 6, which is a horizontal cross-sectional view taken along the line VI-VI of FIGURE 3 but with a portion of the forward idler roller and its supporting shaft 58 broken away. The transversely aligned fixed guide posts, 62, 62 and 66, 66' are secured in fixed positions to the respective, vertical mounting plates and 40. The slide .blocks 61, 61 are provided with facing, longitudinal channels, each channel including a vertical portion extending to the upper surface of the corresponding slide Iblock. The rear idler roller 26 is rotatable with the longitudinal portions of the channels and is inserted into position by passing the ends thereof through the vertical portions of the slots. As is apparent from FIGURES 3 and 4, the ends of the idler roller 26 are retained in the longitudinal portions of the slide block channels by the tension exerted against the roller Aby the strip 29 of the waste material. As this tension is increased, or decreased, the slide blocks and the idler roller move linearly in a plan parallel to that of the web.

Referring now specifically to FIGURES 4 and 5, an electro-magnetic clutch 72 has an integral collar 73, which collar is secured to the shaft 74 passing through aligned holes provided in the bearing blocks 75 and 76, said bearing blocks being secured to the vertical mounting plate 40. A bevel gear 77 (see FIGURE 4) is secured to the shaft 74 and is in mesh with the similar bevel gear 47, which is secured to the shaft carrying `the drive roller 28 (see FIGURE 5). A sprocket wheel 78 normally is freely rotatable about the`shaft 74 and 4is connected by a drive chain 79 to the sprocket wheel 80, the latter being secured to the main drive shaft 21 of the machine. Although the main drive shaft 21 rotates continuously during operation of the machine, the drive shaft 74, carrying the bevel gear 77, rotates only when the electrornag netic clutch 72 is energized by a voltage applied to the leads 81, that is, the sprocket wheel 7 8 rotates freely about its shaft 74 when the clutch is deenergized and such sprocket wheel is mechanically coupled to its shaft by means of the collar 73 and the clutch when the latter is energized.

As has been described with reference to FIGURE 1, the wheel 34 is rotated by the main drive shaft 21 and carries a -shoe 35 which effects a closing and opening of the electrical contacts of the micro switch 36. The timed operating sequence of the machine is such that the contacts of the micro swit-ch are closed when the drive rollers 18 are rotated to advance the web 15. After the web has been advanced, the shoe 35 permits the micro switch contacts to return to the open position. The micro switch contacts control the operation of the magnetic clutch as will now be described with reference to the schematic circuit diagram of FIGURE 8. Here, a voltage obtained from a conventional power line is applied to the rectifier -83 upon closure of the line switch 84. The operating solenoid of the electro-magnetic clutch 72 is connected across the output diagonals of the rectifier through the contacts of the micro switch 36. As shown, the operating pin 85, of the micro switch, is depressed by the shoe 35, the switch contacts are closed and the clutch is energized, whereby the sprocket wheel 78 is mechanically coupled to the shaft 74. When the trailing edge of the shoe V35 passes beyond the pin 85, the switch contacts are opened, the clutch is deenergized and the sprocket wheel is decoupled from the shaft 74; the micro switch incorporating a suitable spring-biasing arrangement which normally retains the contacts to open position, as is well known.

rIt will be clear, now, that the drive roller 28, of the waste stripper (see particularly FIGURE 4), is rotated only during the time period when the web 15 is advancing and that the rotation of this drive roller-results in the strip 29, of the waste material, being wound on the waste roller 27. Further, as the diameterof the rolled waste strip increases, the shaft 43, carrying the waste roller 27, slides upwardly within the aligned slots of the bifurcated end pieces secured to the vertical mounting plates of the waste stripper.

The operation of the waste stripper will best berunderstood by reference to FIGURE 7, which is a vertical cross-sectional view taken along the line VII-VII .of FIGURE 5. The drive roller 28 is rotated only during those portions of the machine operating cycle when the web 15 is being advanced. Thus, during movement of the web, the strip 29 of the waste material is peeled therefrom and wound upon the waste rewind roller 27. When the web is stationary, the drive roll also lis stationary. It Iwill be noted that the slide block 61 is biased t0 the right by the spring 64 and to the left by the spring 67. The adjustable collar 68, is secured to the rod 65 to compress the spring -67 as is necessary in order to set the normal position of the idler roller 26. Such adjustment of the normal, or working, positionof the idler roller is desirable to fix the axial line along which the Waste material is peeled from the web, since the initial force required at the start of each peeling operation depends upon the size of the particular labels, the character of the backing strip and the particular pressure-sensitiveadhesive. The described vadjustment obviates the need to move the entire waste stripper and/or other operating components of the machine in order to effect an optimum release of the waste material from the backing strip.

Once the normal position of the idler roller 26 has been set for operation with a particular web, the slide block 61 is free to move to the left or to the right in response to changes in the tension of the waste strip 29 effective against the idler roller 26. Such tension changes may occur due to varying adhesion of the waste material and the backing strip at the peeling point, the build up of the waste material strip on the roller 27, or the difference in the force required to start the peeling operation as compared to that after the peeling operation has been started. In any event, the described floating arrangement of the slide block provides compensation for these variable factors, thereby effecting a uniform release of the waste material from the backing strip. This factor, together with the fact that the stripping operation is performed only during the period when the web is moving through the machine, eliminates the possibility of distorting the backing strip carrying the formed labels thereon. Obviously, distortion of the backing strip alters the original registry of the labels and may render such label- 7 carrying strip unsatisfactory for subsequent use in a printing machine or a machine for automatically removing the labels from the strip.

In the illustrated construction and arrangement of the waste stripper, the rear idler roller is shown of a relatively small diameter and spaced somewhat from the surface of the web. Such arrangement has been found to be, practical for use on label-making machines wherein the ratio of the label area to that of the waste material is relatively high. In machines wherein this ratio is smaller, itis desirable to use a roller of larger diameter with its surface positioned in closer proximity to the web surface. Also, certain label-making machines have gear racks secured to the top surfaces of the ways. In such instances, the waste stripper can advantageously be provided with a conventional meshing gear rotatable by a handle to position the stripper along the rack and a locking lever for securing it in the desired position.

Having now described the construction and operation of my novel wast-e stripper, those skilled in this art will will be able to make Various changes and modifications without thereby departing from the scope and spirit of the invention as recited in the following claims.

I claim:

1. A waste stripper comprising,

(a) a pair of vertical, spaced mounting plates,

(b) a horizontal plate spanning said mounting plates for supporting a web of label-making stock,

(c) a rewind roller carried 'by ya shaft journaled for rotation within aligned, vertical slots formed at the upper ends of the mounting plates,

(d) a drive roller rotatably carried by the mounting plates `and positioned to support said rewind roller,

(e) a first idler roller having la surface proximate to said horizontal plate,

(f) `bearing means supporting said first idler roller for rotation about an axis parallel to the plane of said horizontal plate,

(g) adjustable spring-biasing means for positioning said bearing means in a predetermined position while affording linear movement thereof parallel to the horizontal plate,

(h) a second `idler roller, and

(i) spring-'biased Ibearing means carried by the said vertical mounting Iplates and supporting said second idler roller Ifor rotation rabout an axis spaced a greater distance from the horizontal plate than that of the said first idler roller.

2. The invention as recited in claim 1, including a drive shaft carried by one of said vertical mounting plates, means coupling said dri-ve shaft to the shaft of said drive roller for simultaneous rotation thereof, and means including -an electro-magnetic clutch carried by said drive shaft for effecting rotation thereof by a remotely positioned power driven shaft.

3. The invention as recited in claim 2, wherein the said bearing means supporting the first idler roller comprises a pair of spaced slide blocks receiving the ends of said roller; and wherein the said adjustable spring-biasing means comprises axially-aligned sets of rods, each set of rods being slidably supported by spaced posts secured to the vertical mounting plates and having adjacentlydisposed ends secured to an associated slide block; compressing springs carried by each of said rods; and collar means carried by one rod `of each set and securable in fixed position thereon to apply a predetermined amount of compression t-o the corresponding spring.

4. In a pressure-sensitive adhesive label-making machine of the class having a main drive which rotates continuously during machine operation and wherein a web of la'bel stock is advanced intermittently during formation of the labels, the combination of,

(a) a waste stripper carried by the machine and through vwhich the web passes after the formation of the labels, said stripper comprising a first idler roller having a surface proximate to the web, a second idler r-oller offset `from the first idler roller along the web axis, a rewind roller on Awhich a strip of waste material is wound after it passes over both of said idler rollers, a drive roller carried by a shaft and supporting the roll yof waste material as it is wound on said rewind roller, a drive shaft rotatably coupled to the shaft carrying the drive roller, said drive shaft carrying an electro-magnetic clutch,

(b) means rotatably connecting the said drive shaft of the waste stripper to the main drive shaft of the machine when the said clutch is energized.

(c) a normally-open switch carried by the machine,

(d) switch-actuating means effecting operation of said switch in timed sequence with the advance of the we'b, and

(e) leads connecting the clutch to a source of voltage upon closure of the said switch, the arrangement being such that the clutch is energized only when the web is advancing whereby the said drive roller rotates the said rewind roller to wind the strip of waste material thereon simultaneously with the advance 0f the web through the waste stripper.

5. The invention Ias recited in claim 4, wherein the said -first idler roller is carried by spring-backed bearing means movable in a plane parallel to that of the web in correspondence with changes in the tension of the waste lmaterial strip as it is wound on the said rewind roller.

References Cited UNITED STATES PATENTS 942,164 12/ 1909 Bolton 242-67.3 X 1,181,937 5/1916 Stevens 242--65 1,929,087 1'0/'1'933 Wood 242-753 1,985,524. 12/1934 Stacey 242-673 2,743,064 4/1956 LeFebure et al. 242-673 X 3,055,606 9/-1962 Alden 242-673 3,178,123 4/1965` Buddecke 242-673 X 3,191,884 6/1965 West et al. 242-67.1

GEORGE F. MAUTZ, Primary Examiner.

Claims (1)

1. A WASTE STRIPPER COMPRISING, (A) A PAIR OF VERTICAL, SPACED MOUNTING PLATES, (B) A HORIZONTAL PLATE SPANNING SAID MOUNTING PLATES FOR SUPPORTING A WEB OF LABEL-MAKING STOCK, (C) A REWIND ROLLER CARRIED BY A SHAFT JOURNALED FOR ROTATION WITHIN ALIGNED, VERTICAL SLOTS FORMED AT THE UPPER ENDS OF THE MOUNTING PLATES, (D) A DRIVE ROLLER ROTATABLY CARRIED BY THE MOUNTING PLATES AND POSITIONED TO SUPPORT SAID REWIND ROLLER, (E) A FIRST IDLER ROLLER HAVING A SURFACE PROXIMATE TO SAID HORIZONTAL PLATE, (F) BEARING MEANS SUPPORTING SAID FIRST IDLER ROLLER FOR ROTATION ABOUT AN AXIS PARALLEL TO THE PLANE OF SAID HORIZONTAL PLATE, (G) ADJUSTABLE SPRING-BIASING MEANS FOR POSITIONING SAID BEARING MEANS IN A PREDETERMINED POSITION WHILE AFFORDING LINEAR MOVEMENT THEREOF PARALLEL TO THE HORIZONTAL PLATE, (H) A SECOND IDLER ROLLER, AND (I) SPRING-BIASED BEARING MEANS CARRIED BY THE SAID VERTICAL MOUNTING PLATES AND SUPPORTING SAID SECOND IDLER ROLLER FOR ROTATION ABOUT AN AXIS SPACED A GREATER DISTANCE FROM THE HORIZONTAL PLATE THAN THAT OF THE SAID FIRST IDLER ROLLER.

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