US3545690A - Shredder type hammermill - Google Patents

Description

O United States Patent [1113,545,690

[72] Inventors Weneil J. Burials; 3,326,478 6/1967 Van Endert 241/186 Donald E. Herman; Robert M. Stepanek; 3,335,967 8/1967 Williams... IOU/97X Paul R. Vilian, Cedar Rapids, Iowa 3,426,674 2/1969 Testolin 100/95 1966 Primary Examiner-William S. Lawson [45] Pa Dec. 1970 Attorney Darbo, Robertson and Vandenburgh [73] Assignee Pettibone Corporation Chicaimmlm ABSTRACT In a shredder r or car bodies the bodies are fed a corporation of Delaware over a notched cutter bar. A rotor has swing hammers of two lengths, one set passing through the notches and the other [54] SHREDDER TYPE HAMMERMILL passing close to the teeth between the notches. Just beyond the cutter bar spaced bars and inward projections cooperate 13 Claims, 7 Drawing Figs.

to let bnttie material escape. Beyond these, escape of frag- [52] U.S. Cl. 241/186, mem is aided by sloping the sides of the bars which they will 3 241/190 241/193 241/194 241/285 strike outwardly and in the direction of movement. The bodies [5 l] int. Cl. ..B02c 13/04, are fed down a chute with feed controlled by a driven toothed B02: 13/286 roller which can move up and downwardly, being carried by a [50] Field olSearch 241/186, frame that is remotely pivotecL The rear upper portion of the 189, 190, 193, 194, 285, 295; lQ0/94- housing for the hammermill is a hood hinged at its rear edge and swinging past a balanced position. Hydraulic cylinder [56] References Cited means are provided for the feeder and the hood each double- UNITED STATES PATENTS acting. A joint hydraulic system is provided with separate 2,655,213 53 Anderson 4 /29 manual valves for the two functions and a selector valve for 2,869,793 l/l959 Montgomery 241/ 186X choice between the functions. The hood is closed by bolts held 3,202,369 8/1965 Judd 241/190 taut by wedges which rest on surfaces sloping in a direction 3,283,698 1 1/ 1966 Williams 100/95 such that vibration tends to tighten the wedges.

0 0 I3 I e 0 I9 E /a m m 7/ o if Z9 2 3545690 SHEET 1 BF 3 PATENTED DEC 8 I976 I NVEN TORJ BY 019% WWW PATENTEB on: 8|976 HOOD SHEET 3 OF 3 srmnnmm TYPE .HAMMERMILL INTRODUCTION The invention of which the present disclosure is offered for public dissemination in the event that adequate patent protection can be given relates to hammermill type shredders. The illustrated form of the invention is especially suitable for shredding junked automobiles, only slightly stripped.

Hammermills have long been used for shredding scrap steel but are better known in other uses such as crushing rock, grinding grain etc. Heavy hammers along the periphery of a rotor are rotated at high speed, their tips following a circular path known as the hammer circle. When a large piece of scrap metal is fed into the hammer circle, it is struck by hammers which tear off small pieces. The hammers may also sweep or throw a larger piece along within a cage of grate bars within which the hammer rotor rotates. Pieces which are small enough may escape through the grate openings, larger pieces being struck repeatedly until reduced to size.

In a US. Pat. application being filed approximately concurrently by Theodore A. berhellmann, Ser. No. 575,335, now US. Pat. No. 3,489,078 "certain features of the present preferred form of the invention are being claimed. The present application is directed toward the features of this preferred form of invention which may use, but which go beyond, the initial concepts which are the subject of the Oberhellmann application.

According to the present invention, improvements are made in the initial grate structure with a view to quick discharge of abrasive particles and other advantages. In addition, an improved gravity-tightened wedge clamping means is provided for holding the hood tightly closed. Also some improvements in the hydraulic system are provided, especially for greater safety. j j

The rear end of the hammermill, opposite the feed end, is a hood which may be opened for servicing. Safety features and quick-release clamps are provided.

Additional objects and advantages of the invention will be apparent from the drawings and from the following description.

DESIGNATION OF FIGURES FIG. 1 is a perspective view of an embodiment of the invention chosen for illustration, including adjacent related parts.

FIG. 2 is a fragmentary view similar to a part of FIG. 1 but showing the hood of the hammermill raised for servicing.

FIG. 2A is a view of a wedge clamp for the hood.

FIG. 3 is a vertical sectional view through the hammermill, showing also the feeder.

FIG. 4 is an approximately horizontal sectional view through the hammermill of FIG. 3, without the feeder.

FIG. 5 is a hydraulic diagram for the hydraulic controls for the two pairs of hydrauliccylinders.

FIG. 6 is a'diagrammatic view of the feed roll drive.

semination is detailed to ensure adequacy and aid understanding, this is not intended to-prejudice that purpose of a patent which .is to cover each new, inventive concept therein no matter how others may later disguise it by variations in form or additions or further improvements. The claims at the end hereof are intended as the chief aid toward this purpose, as it is these that meet the requirement of pointing out the parts, improvements, or combinations in which the inventive concepts are found. u 1

An embodiment of the invention is shown as a whole in FIG. I. A car body 11 is placed on a feed chute 12 by a suitable lifting device such as a grapple I3, operated by cables 14, and controlled by a crane operator,- the crane not being shown. A feeder head 16, which includes a driven roller as will be described, may be raised and lowered by a pair of hydraulic cylinders 17 of which one is shown in FIG. 1. The raising and lowering and the drive of the feed roll may be controlled by an operator in booth 18, who "may view the feeding operation through a window 19. A powerful'motor in a motor shed 21 drives a shaft 22 on which the hammer rotor to be described is mounted. This hammer rotor is housed within the housing or body 23 of the hammermill which rests on a concrete foundation 24. The foundation 24 has a passage through it in which a discharge conveyor 26 runs, being driven by a chain drive within the guard 27. The conveyor 26 dumps into a hopper 28 which discharges onto a conveyor 29, leading to the next unit of the plant.

The inside of the hammermill is made quite accessible by opening the upper rear portion or hood 31 of the hammermill housing, by means of a pair of hydraulic cylinders 32, one of which is visible in FIGS. land 2. The hood 31 is shown in the raised or open position in FIG. 2. I

THE FEEDER As seen in FIG. 3 a feed roll 36 above the lower end of chute 12, is driven by a motor 37, preferably at a controllable speed. Also, it is important to have 'means for raising and lowering the feed roll 36, this means comprising hydraulic cylinders 17 which raise a feed roll frame 38 pivoted'to the chute at 39. Although the feed chute 12 is shown at a fairly steep pitch, this is primarily for the purpose of causing car bodies or the like to slide down to the feed roll 36. Accordingly, the approach surfaces to feed roll 36 need not be so steep or need not be inclined at all, if other meansis provided for moving the car bodies to a position at which they will be controlled by feed roll 36, preferably providing some feeding force to aid the feed roll in advancing the car bodies into the hammermill. This may be a vibratory feeder. The feed roll, according to one feature of the invention, can be raised to a point of sufficient clearance e.g. 4 inches) to receive under it the hood of an unflattened car body, is provided with a plurality of peglike pro jections 40' and can be powered down hydraulically.

The feed roll 36 functions not only to move the car bodies into the hammermill, flattening them at the same time, but also to prevent them from being dragged into the mill too fast by the rotating hammers 41 and 42.

Y ROTOR, BREAKER BAR AND GRATES The hammers 41 and 42 are a part of a rotor 40 carried and driven by shaft 22. More specifically, the hammers 41 are carried by arms 43, and hammers 42 are carried by arms 44 which are interspersed between arms 43 and extend perpendicularly to them. Preferrably the arms 43 and 44 are welded together, but in any event they are keyed to shaft 22 to be driven by it. The hammers 41 and 42 all swing on bolts 46. They tend to maintain the position shown in FIG. 3 due to their centrifugal force, but will swing slightly from this position as they strike heavy objects and preferably can swing 360 about the axes of hammerbolts 46.

The hammerbolts 46 are carried not only by the arms 43 or 44, but also by end disks 47, which are also keyed to shaft 22. End disks 47 rotate within side liners 48 which preferably provide a small clearance for rotation of disks 47. Shaft 22 is rotatably carried by sturdy bearing assemblies 49. According to common practice, all internal surfaces of the hammermill housing which would be subject to wear and abrasion are protected by removable liners such as the liner 48.

A breaker bar or cutter bar 151 is positioned at the discharge end of feed chute I 1. Preferably this bar extends fairly close to the hammer circle. It is also preferred that the breaker bar 51 be provided with notches 52 through which the hammers 41 swing. These notches separate projecting teeth or tongues 53 on the breaker bar which are located in the planes of rotation of the hammers 42. It will be observed that the hammers 42 have an effective length shorter than that of hammers 41. By this is meant that their outer tips are not as far from the axis of shaft 22 as are the outer tips of hammers 41. It is desired that the longer hammers 41 chop slugs out of an entering car body,

and that then the shorter hammers 42 chop off the intervening tongues. Cutter bar 51 rests on a table 54 on which it may slide. At present its position on table 54 is adjusted by screws 56 and the breaker bar is clamped in place by bolts 57. Adjustability is not believed to be necessary however, because when wear is excessive bar 51 is turned. Breaker bar 51 is preferably reversible, having notches 52 and tongues 53 along the unused edge of the breaker bar, as seen at the lower right in FIG. 4. Since also either face can be up, it has four wear surfaces.

A series of fixed grate bars 61 and 67 with discharge openings therein extend around the rotor 40. The first of these openings is as close to the breaker bar 51 as is practicable, separated only by a lower breaker bar 62, which is immediately adjacent a support wall 63 for breaker table 54. Each grate bar is supported only at its ends and hence its main body forms a sturdy beam. Each grate bar 61 has welded to it a series of spacer blocks 64 which project inwardly to provide teeth 66 which help shred the car bodies in case any large pieces escape the chopping action of the hammers on breaker bar 51. According to the present invention the spacers 64 also provide relatively narrow openings to help release glass fragments and other abrasive dirt for immediate discharge, aided by the tendency of such materials to explode on impact.

The second type of grate bar 67 begins approximately oneeighth of a revolution beyond the breaker bar 51. These bars 67 are cast of manganese steel with integral spacer lugs 68 and 68'. According to the present invention, the surfaces of bars 67 facing against the hammer rotation slope outwardly and rearwardly so that metal pieces which strike them will be deflected outwardly to escape quickly from the hammer action. The quick escape of metal pieces after they have been reduced to size is desirable to reduce wear on the hammers and other parts. The rearward faces of beams 69 slope somewhat outwardly and rearwardly also, but this is incidental to other considerations such as providing adequate openings between the grate bars. However, with the sloping grate bars of the present invention, the openings are preferably somewhat smaller than they might be with radially disposed grate bars, inasmuch as the sloping of the grate bars facilitates the passage of the metal pieces through the smaller openings. Hence, more or sturdier grate bars can be provided, with some reduction in the need for replacement due to wear.

When hood 31 of the housing is swung open on its hinges 71, by hydraulic cylinders 32, worn bars 67 and 61 and lower breaker bar 62 may be removed and replaced. Also access is given for easy replacement of hammers or building them up with welding. Cutter bar 51 may be removed endwise (parallel to the rotor axis) for turning or replacement.

At the end of the series of grate bars 67, there is preferably provided an inwardly projecting deflector impact bar 72 which preferably has ears welded to it for securing by bolts 70. A substantial number of metal pieces which have not escaped the hammer area prior to reaching the impact bar 72 will be deflected by it and ejected into the discharge area 73. A reinforcing beam 74 is positioned above the cover plate 76 in the vicinity most frequently struck by such pieces.

An additional removable breaker plate 77 is located in a position to be struck by pieces passing the breaker plate 72. This breaker plate may be replaced by being raised nearly vertically, after withdrawing one securing rod 78.

Feed roll 36 cannot only be raised and lowered as will be described, but also it is driven at a variable speed which is subject to both manual and automatic control. So long as the rotor of the hammermill rotates at nearly full speed, the manual control of the drive of feed roll 36 will prevail. This speed is controlled by a knob 81 on the operator's panel in control booth 18. By experience, the operator will learn the most desirable speeds for different conditions of feed. Through a control system 82, the speed of drive of roll 36 is controlled by variations in the energization of a magnetic clutch 83 of eddy current type through which motor 37 drives speed reduction gears 85, by which roll 36 is driven. If the hammermill rotor encounters such heavy feeding that its speed is materially reduced, a current transformer 84 on one of the main current supply lines to hammermill motor 86 will detect an increased current flow and cause control system 82 to reduce the speed of drive of feed roll 36, and if necessary, to stop this drive. The operator can control the sensitivity with which the speed is reduced by adjusting a knob 87, which may be more remotely located, Another remote knob, not shown, can control the maximum speed attainable by knob 81. The main portion of the control system 50 is 1, Louis Allis SCR Type MD-2 controller.

Control systems of this type are old, and have been used previously in controlling the feed to rock crushers. Accordingly, they need not be described in detail. Here, however, feed roll 36, aided by gears 35 with a ratio of about 50 to l, additionally restrains the bodies from being drawn in too fast.

HYDRAULIC SYSTEM The preferred hydraulic system is shown in FIG. 5. A hydraulic pump 91 is driven by a motor 92, with the usual gage, relief valve, etc. A manual valve 93 selectively connects pump pressure (through line 94) to either line 96 leading to the feed roll elevation control or to line 97 leading to the control for swinging open the rear housing portion or hood. in a third position valve 93 can connect pressure line 94 directly to return or discharge. The valve 93 is in the nature of a safety feature so that it will be impossible for the operator to inadvertently elevate the hood and the feed roll at the same time.

The line 96 leads to a second manual valve 98 which is the valve the operator ordinarily operates for controlling the elevation of the feed roll 36. This valve has four positions. In the position shown the oil is ordinarily locked in the cylinders 17 holding them at whatever position they are in. The pump pressure is bypassed to return. This is the position to which the spool of the valve (which is connoted by the showing 98) is spring biased. When the spool is moved in one direction, outwardly of the valve (downwardly in FIG. 6) the pump pressure line 96 and the return line will be connected to the cylinders 17 in a direction to lower the roller 36. Oil pressure, varied with the amount of spool movement, can thus be added to the weight of the roller and the frame 38 to help flatten or mash down a car body or to grip it more firmly for feed. A gage 99 shows the amount of applied pressure.

When the spool of valve 98 is moved in the opposite direction, it. approaches a first position in which the pump pressure line 96 and the return line are connected oppositely to cylinders 17 so that the feed roll is raised. With movement of the spool beyond this position, the two ends of cylinders 17 are connected to each other so that the float" condition is achieved and, subject to the weight of roller 36 and its frame 38, the roller 36 may rise and fall as may be determined by the force exerted on it by a car body passing through. A weight 101 may be added to give the desired amount of pressure on a car body in this float condition.

A relief valve 102 may be set to determine the maximum pump pressure which will be delivered to cylinders 17.

When the valve 98 is in its position of rest, the position at which the cylinders 17 are hydraulically locked, the feed roll 36 may nevertheless be lowered by energizing a solenoid 103 to operate valve 104 to connect the lower ends of cylinder 17 to discharge, a check valve 106 permitting the upper ends of cylinder 17 to draw oil so that there will be no cavitation.

When the selector valve 93 is moved in the direction to permit raising the hood, control of the hood is achieved in much the same manner by manual valve 111. However, in this instance, the float" position is not provided. A relief valve 112 to be restrained so as not'to slam shut. Accordingly, a counterbalance valve or pilot valve 114 is provided. When the spool of 111 is moved in the direction to apply pump pressure to the upper ends of cylinders 32 to lower the hood, and the hood passes the point at which it is balanced and begins to exert a pressure in the closing direction, the counterbalance valve 114 will close the line from the bottom of cylinders 32, or partially close it to control the speed. Although the operation of such valves is well known, it may be explained that a spool represented by pointer 1 l6 prevents downward flow from the line 117 through line 118' to discharge line 119 except when a predetermined pressure is applied to the spool through line 121, known as the pilot line. A suitable pressure for opening the connection represented byarrow 1 16 is 200 pounds on the pilot line 121. Thus, whenvalve spool 111 is moved toward the position for lowering the hood, pump pressure is applied to line 122 leading to the upper ends of cylinders 32. However, the cylinders cannot lower the hood until line 117 is connected to discharge. Thisis accomplished as soon as the pressure in line 122 builds upjto'200 pounds by virtue of the pilot line 121 which actuates the pilot or cushion valve 114 to make the connection represented by swinging arrow 116 into alinement with connecting line 118; For raising the hood, check valve 123 permits the pump pressure to be delivered to line 117 regardless of the condition of the valve represented by the arrow .1 16.

ADDITIONAL FEATURES AND FURTHER DISCLOSURE Most operators desire thehood 31 to be securely fastened during operation. Heretofore, it has usually been secured by a series of threaded screws or nuts and bolts which had to be removed by the slow process of unscrewing. According to the present invention quick opening clamp means are provided. As seen in FIG. 2A, a headed bolt 126 is slipped through passages in support flange 127 and flange 128, which is part of hood 31. A wedge 129 is slipped through a slot in stem 131 of bolt 126, and driven tight'so that it wedges flange 128 against flange 127. If bolt 126 is vertically arranged as shown, there would be danger that vibration would loosen the wedge 129. This loosening is avoided by providing a sloping seat 132 for wedge 129, so that (under the influence of gravity and vibration) wedge 129 tends to move downwardly to the right, as seen in FIG. 2A so as to maintain itself in wedging position. At locations where the bolt 126 is horizontally disposed the pin 129 will be inserted, downwardly and the seat 132 is not needed. In either event, the end of the slot in stem 131 will be shaped to engage full face against the side of the wedge 129. Where the seat 132 is provided it has an aperture through which stem 131 passes as it is inserted through flanges 127 and 128.

Fabricated grate bars 61 and breaker bar or cutter bar 51 are preferably formed of a very hard steel alloy of an abrasion resistant class such as the US. Steel T-l class, quenched and tempered. At present, a 321 minimum Brinnel hardness is specified. Because the more abrasive materials, such as glass fragments, are usually discharged through the first grate section (bars 61) the following bars 67 need not be as hard, although they may work-harden.

The teeth 53 of cutter bar 51 present a severe problem in resisting bending and wear. In the present use they should not be less than 3 inches in width, 2% inches having been known to bend laterally. Assuming that a thickness is chosen suitable for the job they should be substantially as wide as their thickness. For the teeth 53 to be 3 inches, or the preferred 4% inches wide, it follows that the hammers 41 must be spaced still further apart. It is partly because of this wide spacing of the hammers 41 that a second set of interspersed hammers 42 is desired. The teeth should not be too long, 3% inches having been found to be satisfactory at least when reinforced along part of their length by resting on the table 54.

Although there might seem to be danger of breakage of the teeth if they were made too hard, it has been found that the increased surface hardening resulting from torchcutting of bar 51 without subsequent tempering does not cause breakage, and reduces wear. 1

In one metal shredder according to the present invention the maximum speed of the feed roll 36 is set at about 55 peripheral feet per minute. A speed over 50 is rarely used, however, while the shredding is taking place. The rotor speed in that machine is 720 r.p.m. Theoretically, these comparative speeds would result in nipping the steel successively with such slight movements between nips that the desired action of chopping off slugs of moderate size would not be achieved. However, for some reason the theoretical action of merely nipping off toothpick like pieces does not occur. This is probably because the hammers, as they strike the metal are moving in a'direction to seize the metal and draw it inwardly somewhat. Because of the tendency of the hammers to draw the metal in, it is important that the feed roller 36 be capable of restraining the metal, so as not to overload the hammermill.

A 2,000 horsepower motor is preferred for driving the rotor 40, assuming the rotor to have a 74 inch outer hammer circle and to be 1 12 inches long, measured from the outside faces of the disks 47. Much higher horsepower motors have been used heretofore for shredders of comparable output. As a matter of fact, an even smaller motor, 1,500 horsepower has been used successfully with the present machine.

ACHIEVEMENT In this field in which motors capable of delivering thousands of horsepower have been required, substantial savings of power use and motor size have been made. Wear has also been reduced. Of course, wear is inevitable on the cutter bar, the hammers and the grate bar's, but'the cutter bar may easily be turned to present successively four faces to wear, and replacement of the others is made easy by the hydraulic opening of the hood 31 and by quick opening clamps.

Car bodies with frames and axles and which have not been previously flattened can be drawn into the machine, and simultaneously progressively flattened or mashed down, by the driven and power-lowered feed and compressions roll. Because of its restraining action and partially automatic control of its speed, the bodies can be fed at a good speed without danger of overloading the hammermill.

In addition to making valuable scrap metal from junk which is mostly steel, such as car bodies, the present invention is useful in disposal of solid waste, such as the contents of city dumps, rubble from wreckage of buildings in which metal is often encountered, and the like. Of course, the feed roll clearance will usually not need to be as large for such uses, and some uses of some features of the invention may not need the feed roll at all or may use it differently located.

We claim:

1. Apparatus for shredding metal including a feeder for feeding metal to be shredded at a controlled speed with restraining action on the metal, and a hammermill for receiving the metal fed by the feeder; said harm'nermill including:

a cutter bar over which the metal is fed, a grate cage extending initially downwardly and generally arcuately from said cutter bar, and a driven rotor having hammers thereon, rotating within the curvature of said cage with its axis so positioned that the hammers move close to the cutter bar and across the direction of entry of metal into the hammermill to chop pieces from it;

said cutter bar having a series of notches therein opening toward the rotor and said rotor having one set of hammers disposed to pass through said notches, and another set of hammers terminating closer to the rotor axis and disposed axially between the hammers of the first set to cooperate with the portions of the cutter bar between the notches thereof; and

the grate cage having a seriesof relatively small discharge openings extending from substantially adjacent the cutter bar in the direction of rotor rotation to discharge abrasive particles, and a series of 'larger openings extending therefrom to a point in which the radial discharge direction is steeply upward, surfaces of this latter series which face against the direction of rotation sloping outwardly and in the direction of rotation to deflect outwardly metal pieces su'iking said surfaces.

2. Apparatus for shredding metal, including feeding means for feeding scrap metal at a controlled speed and restraining it against being drawn in at higher speed, rotor means carrying a plurality of swing hammers, cutter bar means extending parallel to the axis of said rotor means and cooperating with said hammers to break up the scrap metal, and a grate partially surrounding said rotor means; said grate comprising:

a first portion beyond said cutter bar including a plurality of relatively closely spaced and parallel bars, each extending generally parallel with said axis, spacer means between said bars for maintaining same in spaced relationship, said spacer means including toothed means projecting inwardly of said bars toward said rotor means to aid in the quick release of brittle inclusions in said scrap and their discharge through said first portion; and

a plurality of relatively widely spaced-apart bars forming a second grate portion beyond said first grate portion, each of said second plurality also extending parallel to said axis.

3. Apparatus for shredding metal as set forth in claim 2, wherein the bars in said second grate portion form discharge openings sloping outwardly and in the direction of rotor rotation to facilitate discharge of said scrap and reduce wear thereof.

4. Apparatus for shredding metal including a feeder for feeding metal to be shredded, and a hammermill for receiving the metal fed by the feeder; said hammermill including:

a cutter bar, a grate cage extending initially downwardly and generally arcuately from said cutter bar, and a driven rotor having hammers thereon, rotating within the curvature of said cage with its axis so positioned that the hammers move close to the cutter bar and across the direction of entry of metal into the hammermill to chop-tear pieces from it;

said cutter bar being removable endwise and insertable in each of four positions to present different wear surfaces toward the hammer approach, said grate cage being formed of separate bars slidable about the rotor axis to a point of removal, the hammermill including a hood hinged to give access to the point of removal; and

hydraulic means for raising the hood and wedge-type quickopening clamps for securing the hood in its closed position, at least one of said clamps including a vertically extending bolt, a wedge drawing said bolt into position, and a seat on which said wedge rests and slides, said seat sloping in a direction to gravitationally bias said wedge in the wedging direction.

5. Apparatus for shredding metal including a feeder for feeding metal to be shredded, and a hammermill for receiving the metal fed by the feeder; said hammermill including:

a cutter bar, a grate cage extending initially downwardly and generally arcuately from said cutter bar, and a driven rotor having hammers thereon, rotating within the curvature of said cage with its axis so positioned that the harnmers move close to the cutter bar and across the direction of entry of metal into the hammermill to chop-tear pieces from it;

said grate cage being formed of separate bars slidable about the rotor axis to a point of removal, the hammermill including a hood hinged to give access to the point of removal; and

hydraulic means for raising the hood and wedge-type quickopening clamps for securing the hood in its closed position, at least one of said clamps including a vertically extending bolt, a wedge drawing said bolt into position, and a seat on which said wedge rests and slides, said seat sloping in a direction to gravitationally bias said wedge in the wedging direction.

6. Apparatus for shredding metal including a hammermill having an access hood, adriven feed and crushing unit for feeding metal to the hammermill, and a hydraulic system for raising and lowering the hood and for raising and lowering the feed unit, including a pump for providing pump pressure, first and second hydraulic actuators for the feed unit and hood respectively, first and second manual control valves for the first and second actuators, and a selection valve for connecting the hydraulic pressure selectively to one only of first and second manual control valves.

7. Apparatus for shredding metal according to claim 6, including an additional valve for at-will lowering the feed roll independently of the selection valve.

8. Apparatus for shredding metal including a feeder for feeding metal to be shredded, and a hammermill for receiving the metal fed by the feeder; said hammermill including:

a cutter bar, a grate cage extending initially downwardly and generally arcuately from said cutter bar, and a driven rotor having hammers thereon, rotating within the curvature of said cage with its axis so positioned that the hammers move close to the cutter bar and across the direction of entry of metal into the hammermill to chop-tear pieces from it;

said grate cage including separate bars slidable about the rotor axis to a point of removal, the hammermill including a hood hinged to give access to the point of removal and swingable about the hinge across a position of dead center balance; and

hydraulic means for raising the hood and wedge-type quickopening clamps for securing the hood in its closed position, at least one of said clamps including: a vertically extending bolt, a wedge drawing said bolt into position, and a seat on which said wedge rests and slides, said seat sloping in a direction to gravitationally bias said wedge in the wedging direction.

9. Apparatus for shredding metal including a hammermill having an access hood, a driven feed and crushing unit for feeding metal to the hammermill, and a hydraulic system for raising and lowering the hood and for raising and lowering the feed unit, including a pump for providing pump pressure, first and second hydraulic actuators for the feed unit and hood respectively, first and second manual control valves for the first and second actuators, and a selection valve for connecting the hydraulic pressure selectively to one only of first and second manual control valves; and quick opening clamps for securing the hood in its closed position, at least one of said clamps including a vertically extending bolt, a wedge drawing said bolt into position, and a seat on which said wedge rests and slides, said seat sloping in a direction to gravitationally bias said wedge in the wedging direction.

10. Apparatus for shredding large metal objects such as automobile bodies, including a rotor having swing hammers thereon, feed means positioned generally to one side of the rotor, a housing enclosing the rotor, opening on the forward side to the feed means, and having arcuate channels extending along the hammer circle of the rotor approximately from the feed means around rearwardly of the rotor approximately to a horizontal plane through the axis of the rotor, grate bars carried in said channels and removable rearwardly of the rotor, the portion of said housing above said plane and rearwardly of the rotor comprising a hood hinged approximately along one edge thereof to be opened for exposing the rotor and channels; said feed means including active portions which can be raised and lowered, hydraulic cylinder means for actuating said active portions, double acting hydraulic cylinder means for the hood, a source of hydraulic fluid under pressure, and valve means for selectively controlling hydraulic flow to the first mentioned or last mentioned cylinders.

l 1. Apparatus for shredding metal according to claim 10 in which the hood, in opening, swings past a dead center balanced position whereby its being maintained open is independent of maintaining hydraulic pressure.

12. Apparatus for shredding metal including a feeder for feeding metal to be shredded, and a hammermill for receiving the metal fed by the feeder; said hammermill including:

a cutter bar, a grate cage extending initially downwardly and generally arcuately from said cutter bar, and a driven rotor having hammers thereon, rotating within the curvature of said cage with its axis so positioned that the hammers move close to the cutter bar and across the direction of entry of metal into the hammerrnill to chop-tear pieces from it;

said grate cage including separate bars slidable about the rotor axis to a point of removal, the hammermill including a hood hinged to give access to the point of removal and 10 swingable about the hinge across a position of dead center balance;

hydraulic means for raising the hood and wedge-type quickopening clamps for securing the hood in its closed position, at least one of said clamps including:

a vertically extending bolt, a wedge drawing said bolt into position, and a seat on which said wedge rests and slides, said seat sloping in a direction to gravitationally bias said wedge in the wedging direction; and

the cage including grate bars along the rear upper quadrant of the rotor carried by the hood and moved with it.

13. Apparatus for shredding metal including a hammermill having an access hood, a driven feed and crushing unit for feeding metal to the hammermill, and a hydraulic system for raising and lowering the hood and for raising and lowering the feed unit, including a pump for providing pump pressure, first and second hydraulic actuators for the feed unit and hood respectively, first and second manual control valves for the first and second actuators, and a selection valve for connecting the hydraulic pressure selectively to one only of first and second manual control valves; the hydraulic actuator for the hood being double acting cylinder means; and said hood swinging across a dead center balanced position to be stable in either open or closed position independently of hydraulic pressure.

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