Apparatus for Producing Continuous Strip of Uncured Rubber and Like Raw Materials

This invention relates to improvements in the art of processing uncured rubber and like raw materials.

When natural or synthetic uncured rubber stocks or like raw materials are being processed in a mill, extruder or like treating apparatus, they are generally fed into the apparatus in the form of either relatively large irregularly shaped slabs or elongated strips previously formed by suitably cutting up sheets of such material. Whereas the processor of the raw material normally desires to have it in slab or strip form, the producer of such materials, who is usually confronted by a shipping and storage problem, prefers to have the material in sheet form, since neither irregularly shaped slabs nor elongated continuous strips of substantial length can be packaged as compactly and economically as possible, i.e. without an undue waste of space. A further disadvantage encountered is that when such material to be processed is in slab or sheet form, it is difficult to feed it uniformly into the apparatus so as to assure the uniformity of the treatment.

It is the primary object of the present invention, therefore, to provide a novel apparatus for cutting sheets of uncured rubber or like raw material so as to enable the relatively wide sheet stock to be readily transformed into continuous strip stock lending itself to a continuous and uniform feeding into the treating apparatus.

Generally speaking, the objectives of the present invention are attained by means for slitting a sheet of such raw material transversely in an alternating sequence in from the opposite side edges of the sheet, in such a manner that each slit terminates short of the respective other side edge of the sheet. The cutting means preferably is a rotary cutter having an even number of blades the cutting edge of each of which is recessed at a respective end of the cutter, with the successive cutting edges being recessed at opposite ends of the cutter in an alternating sequence. When an end portion of a sheet so slit is then introduced into the bite of the treating apparatus while the same is in operation, the sheet is subjected to a pulling force and separates along the slits into a continuous zig-zag strip.

The foregoing and other objects, characteristics and advantages of the present invention will be more clearly understood from the following detailed description thereof when read in conjunction with the accompanying drawings, in which:

FIG. 1 is a fragmentary top plan view of an apparatus embodying the principles of the present invention for producing continuous strip stock from a sheet of the raw material to be processed in a treating apparatus;

FIG. 2 is a fragmentary side elevational view of the apparatus shown in FIG. 1; and

FIGS. 3 and 4 diagrammatically illustrate two ways of utilizing the strip stock formed by the said apparatus.

Referring now first to FIGS. 1 and 2, according to the preferred aspects of the present invention the apparatus 10 for cutting sheet stock S of uncured rubber or like raw material into continuous strip stock comprises a rotary cutter 11 driven by any suitable means (not shown) and journalled in parallel cooperative relation to a rotatable back-up roll 12. The cutter 11 is provided with a plurality of essentially longitudinally extending, peripherally spaced blades 13 which are shown as being curved in the manner of an ogee. The blades 13, of which there must be an even number, are alternatingly recessed at one end, as shown at 13', so that each cutting edge effectively starts at one end of the cutter 11 and terminates somewhat short of the other end thereof. The two members 11 and 12 are adjustably preloaded toward each other, e.g. by springs or other suitable means (not shown), to permit the sheet stock S passing therebetween to be penetrated to a predetermined extent by the active cutting edge portions of the blades 13. Both the cutter and the back-up roll are preferably made of metal, e.g. stainless steel or the like, with the roll 12 further having an outer covering 12' of a suitable elastomeric material, e.g. cast polyurethane.

In the operation of the apparatus 10, the sheet stock S is fed into the bite of the assembly by means of a suitable conveyor arrangement 14 and is there subjected to the cutting action of the blades 13, which at the same time feed it through the nip of the members 11 and 12. It will be readily understood that only the portion of each blade 13 which is not recessed will penetrate into the sheet stock S, and that any portion of the latter which underlies a recessed portion 13' of a given blade will not be cut by that blade. The arrangement may, of course, be so set that the sheet stock S will be entirely cut through, or, for a reason to be explained presently, that the sheet stock will be only partially cut through so as to leave an unpenetrated sheet thickness of, say about 0.003 to 0.004 inch or so. The sheet stock S' which has passed the cutter 11 is transported away by a further suitable conveyor arrangement 15 and is seen to be provided with a plurality of obliquely oriented, parallel, transverse slits 16 extending in an alternating sequence in from the opposite side edges of the sheet and each terminating, as shown at 16', short of the respective other side edge of the sheet. The cut sheet stock S' thus is seen to be composed of a continuous zig-zag strip (see also FIG. 3) in which the connections between adjacent parallel reaches 17 are constituted by the unsevered portions 17' of the sheet.

It will be understood that the present invention can be utilized in a variety of ways. Thus, the apparatus 10 can be more or less intimately associated with a treating apparatus 18 (FIG. 3) of any desired type, for example an extruder used to extrude tread slabs or strips for tires, so that once the leading end of the strip stock 17 has been fed into the extruder, the pulling force exerted by the latter on the strip automatically opens the sheet stock S' into the desired strip form, thereby ensuring a continuous and uniform admission of stock into the extruder. In such a case, the sheet stock S' may be either fully or partly cut through, as previously described, since even if the latter of these conditions obtains, the unpenetrated sheet thickness in the regions of the slits 16 is insufficient to prevent the sheet sections 17 from being pulled apart into the desired strip form. Quite obviously, the original sheet stock S fed into the apparatus 10 may be fed to the latter either directly from a sheeting mill or the like (not shown) or from a package or bale (not shown) in which it was shipped (in properly "soaped" or stearate-coated condition) to the operator of the extruder. This latter arrangement would be highly advantageous, for example, for a retreader who could feed the sheet stock shipped to him by a rubber producer first out of the bale right into the cutter assembly and thence directly into the extruder. The foregoing would apply equally well, of course, if the device 18 were a mill or other processing apparatus rather than an extruder.

Alternatively, if the apparatus 10 is located in the plant of a rubber producer, the latter may feed the stearated sheet stock S taken from a mill or other storage facility into the apparatus 10 to form the cut sheet stock S' which then in its unextended form, i.e. merely as slit sheet, may be packaged (FIG. 4) in a standard bale 19 or on a truck for storage and/or shipment. For this purpose it might actually be preferable (although not necessarily essential) that the sheet stock S' be only partly cut through, since this might make it easier to handle the sheet during the baling and unbaling operations. The ultimate user of the strip stock, e.g. a retreader, is then in a position to feed the strip 17 directly from the bale into the extruder, tests having shown that the cut sheet stock S' does not tend to reknit along the slits 16 between adjacent strip reaches 17 during storage and shipment.

It is to be understood that the foregoing description of preferred aspects of the present invention is for purposes of illustration only, and that a number of changes and modifications in the structural and operational features and relationships disclosed may be made without any departure from the spirit and scope of the present invention as defined by the hereto appended claims. Thus, the blades 13 on the cutter 11 need not be ogee-curved as shown but could be linear instead, and obviously the sheet stock may be cut so that the slits 16 extend substantially at right angles to the side edges of the sheet rather than obliquely as shown. Also, the sheet feed may be intermittent and effected by means other than the cutter itself. Other variations will readily suggest themselves to those skilled in the art.