Tire shredding machine

There is disclosed for use in a machine for shredding scrap automotive tires or the like of the type comprising a pair of oppositely rotating rotors having interdigitated tire cutting discs keyed thereon and replaceable abrasion resistant wearing plates at opposite sides of said disc, an improved means for locking said plates in operative positions on said discs, whereby worn plates may be replaced by new plates from externally of the rotors without requiring costly disassembly and reassembly thereof.

BACKGROUND AND OBJECTS OF THE INVENTION 
This invention relates to apparatus for mechanically chopping, shearing or 
shredding solid materials such as scrap automobile and truck tires; scrap 
insulated electrical conductors; beverage cans; and other solid waste 
materials required to be reduced to substantially uniform smaller 
particulate sizes for efficient permanent disposal, commercial recycling, 
or other utilization. Typically, systems for such purposes include 
conveyor means for carrying materials to be processed from ground level to 
the in-feed of a chopper or shredding machine (which for convenience will 
hereinafter be referred to as the shredder); a screening (or 
"classifying") device for receiving the produce from the shredder and 
passing to discharge product fragments of prescribed sizes; and elevator 
means for returning oversized products to the shredder mechanism. Machines 
for similar purposes are disclosed for example in U.S. Pat. Nos. 
3,578,252; 3,656,697; 3,727,850; 3,841,570; 3,931,935; 4,134,556; 
4,156,508; 4,216,916; 4,363,45O; 4,684,070 and 4,684,071. 
The shredder component of such systems typically comprises a multiplicity 
of spaced apart discs carried by parallel mounted counter-rotating drive 
shafts in such manner that the discs of one shaft interdigitally project 
at their perimetral regions in between the discs carried by the other 
shaft. The discs mount around their perimetral rims successions of canted 
cutting blades as shown for example at 26 in U.S. Pat. No. 4,684,071 and 
at 174 in U.S. Pat. No. 4,374,573. As best shown at FIGS. 10 and 11 of 
U.S. Pat. No. 4,374,573, replaceable abrasion resistant wearing plates 172 
are mounted on opposite sides of the discs under the "cutter segments" 
174. Whereas the provision of rotating disc protecting replaceable wearing 
plates for such purposes has proven to be of important economic advantage, 
the means shown therein for exchanging new plates for worn plates on the 
cutter discs has proven to require difficult and time-consuming and 
therefore unduly expensive maintenance work; and it is the object of the 
present invention to provide an important improvement in the means for 
installing such plates to the cutter discs, and for facilitating the 
replacement of plates for worn plates.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
As shown by way of example in the drawing herewith, the shredding machine 
frame structure includes a pair of oppositely disposed sill members 10,12 
from which vertically extend corresponding side wall members 14,16. A pair 
of drive shafts 18,19 are journalled at their opposite ends in the side 
walls 14,16 and carry in keyed relation thereon a pair of rolls 20,21, 
each of which mounts thereon spaced apart discs 22,24, respectively. The 
rolls 20,21 are so disposed and the parts are so dimensional that the rim 
portions of alternate discs slide-fit interdigitally to provide a 
scissor-like cutting action on the feed material as the discs rotate. A 
plurality of wearing plates 26 are mounted against opposite sides of the 
rim portions of each of the discs, and corresponding cutter plates 30 are 
mounted thereon by means of machine screws 32, so as to cap the assembly 
and lock down the cutter and wearing plates as best shown at FIGS. 2 and 
3. 
A "tongue and groove" arrangement is employed in order to maintain the 
wearing plates 26 against the sides of the discs at the bottom ends of the 
plates. As shown at FIGS. 2, 2A, 3 and 5, a preferred arrangement includes 
snap rings 34 of spring steel which are disposed in grooved portions 36 of 
the discs, and the bottom surfaces of the wearing plates 26 are similarly 
grooved as best shown at FIG. 2A so as to straddle the snap rings. Note 
that the snap rings are C-shaped and discontinuous as shown at 35 (FIG. 5) 
to permit their assembly on the discs 22,24. In order to maintain the 
wearing plates at their upper ends against the discs, a novel form of 
transversely disposed holding pins are employed as shown by way of example 
at FIGS. 2 and 3. As shown, the pins 40 are semi-circular in sectional 
form and are enlarged at the opposite ends thereof by semi-circular flared 
out end portions 42. These pins are disposed within semi-circular grooved 
portions of the discs 24, and their flared end portions nest into 
complementarily shaped hollowed portions 43 of the wearing plates 26. 
However, it is to be understood that the pins 40 may be of any other 
sectional form instead of semi-cylindrical as shown. 
Thus, it will be appreciated that when the wearing plates 26 are radially 
inwardly inserted into registry with the snap rings 34 at their lower 
ends, and the locking pins 40 are settled in place at their upper ends, 
and the cutting blades 30 are locked downwardly thereupon by the screws 
32, the assembly is firmly fastened in place. However, it is a particular 
feature of the present invention that whenever the wearing plates 26 are 
due for replacement, the entire repair operation may be performed without 
any special tools and from externally of the rotor assembly. A standard 
socket wrench need only be applied to the heads of the machine screws 32 
for withdrawal of the cutter bars 30 from the top of the assembly. 
This frees the lock pins 40 for removal and withdrawal of the worn wearing 
plates from their bottom end anchorages on the snap rings 34. Replacement 
wearing plates are thereupon inserted; and locking pins 40 and either 
previously used or new cutting blocks 30 are reinstalled in assembly 
locking position by machine screws 32. Because the rim portions of the 
discs are sandwiched between similar disc rim portions of the opposite 
rotor, in the case of the prior art whenever a wearing plate replacement 
is required it is only feasible (but time and cost wise expensive) to take 
the rotors out of the machine for transport to a shop facility for 
replacements of the worn wearing plates by means of special tools. Such 
tools would need to be adapted to reach in between adjacent discs and to 
manipulate the plate locking means such as the bolts 188 of U.S. Pat. No. 
4,374,573. FIG. 2B shows how a simple form of tongue and groove 
arrangement may be employed in lieu of the plate anchoring means including 
the snap rings 34. In this case, the discs 22 and the bottom edges of the 
plates 26 are sectionally shaped so as to fit together in complemettary 
tongue and groove fashion. Instead of the V-shaped sectional form as shown 
at FIG. 2B, any other polygonal or curvilinear shape may be employed. 
Selection of the preferred form may depend upon the machining method to be 
used. 
Accordingly, the present invention provides an improved wearing plate 
mounting and replacement system for machines designed for shredding scrap 
tires or the like. When machines embodying the present invention are 
operating upon materials of a plastic nature, the initially open spaces 
about the heads of the machine screws 32 may in time become impacted by 
remnants of the material being processed. However, for example a hand held 
rotating cylindrical saw may then be employed to clear away such debris 
from the heads of the screws and a conventional socket wrench may then be 
employed from externally of the rotor incidental to a wearing plate 
replacement operation as described hereinabove.