US3850755A

US3850755A - Apparatus for pyrolytic decomposition or heat treatment of material

Info

Publication number: US3850755A
Application number: US00353711A
Authority: US
Inventors: J Welty
Original assignee: Individual
Current assignee: PYROWASTE Corp A CORP OF
Priority date: 1973-04-23
Filing date: 1973-04-23
Publication date: 1974-11-26
Anticipated expiration: 1991-11-26

Abstract

A wheel-supported frame carrying a reciprocating shaker conveyor is movable into and out of one end of an enclosed, air-tight, heated chamber. The chamber has removable side and top walls, lined with precast, high-temperature ceramic blocks on the sides and top to reflect heat down into material on the conveyor, said blocks being loose-fitting for expansion and keyed together. The top ceramic blocks rest on the side ceramic blocks and the sides stand on shelves fixed to the supporting structure of the chamber. The movable frame carries a transverse vertical panel that forms a removable end wall for the chamber. A motor and driving mechanism on the outside of said end wall reciprocates the shaker conveyor through a sliding pushrod passing through the wall. Material to be processed is fed to the receiving end of the conveyor through an air lock hopper, and charred residue is removed from the chamber at the other end through another air lock. Gas produced by pyrolytic decomposition is drawn off through a pipe.

Description

United States Patent [191 Welty [451 Nov. 26, 1974 1 APPARATUS FOR PYROLYTIC DECOMPOSITION 0R HEAT TREATMENT OF MATERIAL [76] Inventor: James A. Welty, 3964 Seventh St.,

Riverside, Calif. 92501 22 Filed: Apr. 23, 1973 21 Appl. No: 353,711

[52] US. Cl 202/119, 202/223, 202/267, 432/247 [51] Int. Cl Cl0b 7/04 [58] Field of Search 202/97, 98, 102, 103,117, 202/119, 145, 265, 267, 118, 223, 222, 224,

[56] References Cited UNITED STATES PATENTS 2,039,081 4/1936 lllingworth 202/119 2,809,154 10/1957 Storrs 202/119 3,707,355 12/1972 Anderson 202/119 Primary Examiner-Norman Yudkoff Assistant Examiner-David Edwards Attorney, Agent, or Firm-Herbert E. Kidder V l 1 Q /30 J 1 M0 2 .l. L 11 [57] ABSTRACT A wheel-supported frame carrying a reciprocating shaker conveyor is movable into and out of one end of an enclosed, air-tight, heated chamber. The chamber has removable side and top walls, lined with precast, high-temperature ceramic blocks on the sides and top to reflect heat down into material on the conveyor, said blocks being loose-fitting for expansion and keyed together. The top ceramic blocks rest on the side ceramic blocks and the sides stand on shelves fixed to the supporting structure of the chamber. The movable frame carries a transverse vertical panel that forms a removable end wall for the chamber. A motor and driving mechanism on the outside of said end wall reciprocates the shaker conveyor through a sliding pushrod passing through the wall. Material to be processed is fed to the receiving end of the conveyor through an air lock hopper, and charred residue is removed from the chamber at the other end through another air lock. Gas produced by pyrolytic decomposition is drawn off through a pipe.

9 Claims, 6 Drawing Figures PATENTED NOV 2 6 I974 SHEET 3 OF 3 FIG. 4.

FIG. 6.

APPARATUS FOR PYROLYTIC DECOMPOSITION OR HEAT TREATMENT OF MATERIAL BACKGROUND OF THE INVENTION:

fication, the term is intended to cover heat treatment of any material in a sealed chamber, wherein gas and/or vapor is released for further processing.

One of the major problems encountered with known apparatus for pyrolytic decomposition of material is that continuous exposure to high temperature causes the insulative lining to break down, and replacement of the deterioriated lining is an expensive project requiring that the apparatus be shut down for several days while it is cooledto allow workmen to enter and make the necessary repairs. Repairs are difficult and timeconsuming, because the insulation material is customarily laid up in the same manner as masonry, with the blocks of ceramic or material cemented in place, using a special heat-resistant cement. The deteriorated blocks must be knocked out, and the new blocks carefully cemented in place, which requires highly skilled labor. The extended down-time necessitated for repairs on any part of the apparatus is an item of considerable expense.

SUMMARY OF THE INVENTION The primary object of the present invention is to provide a new and improved apparatus for the pyrolytic decomposition ofwaste material, which is highly efficient in operation, relatively inexpensive to manufacture and install, and simple and inexpensive to service.

Another object of the invention is to provide an apparatus of the class described, wherein the chamber in which pyrolytic decomposition takes place comprises an outer shell made up'of a plurality of steel panels that are individually removable so that a workman can get at any specific area of the inner lining from the outside of the chamber, for the purpose of repairing the lining. The advantage of this feature is that it enables the workman to work on the damaged lining Without having to enter the chamber, and therefore the chamber need not be cooled down for repairs.

A further object of the invention is to provide a pyrolysis chamber having an inner lining made up of preformed ceramic blocks that are keyed together on their abutting side edges, so that no mortar or cement is required to hold the blocks in place. The blocks fit loosely together, with ample clearance for expansion as the blocks heat up. The blocks for the side and end walls stand on edge and are supported by shelves projecting inwardly from the supporting structure of the chamber. The blocks for the top of the chamber rest at their ends on the top ends of the side wall blocks, and are keyed together at their abutting side edges. All that is necessary to remove any specific block is to extract the key member from the keyways on both sides of the said block, and then lift the block out. A new block is then placed in position, and the key members are -inserted back into their respective keyways.

Still another object of the invention is to provide an apparatus for heat treatment of material, wherein the material is transported through the heated chamber on a conveyor supported by wheels running on tracks which enter the chamber at one end thereof, said conveyor including a transverse vertical panel near one end thereof that forms a removable end wall for the chamber. The actuating mechanism for the conveyor, including the motor and driving means, is mounted on the outside of the panel, and the drive to the conveyor is transmitted through the end wall. By virtue of this arrangement, the entire conveyor mechanism can be removed from the chamber by merely removing a few bolts from the outer panels, and rolling the conveyor out of the chamber on its wheels to a repair station where the necessary repair work can be done. A standby replacement conveyor is immediately rolled into the chamber, and the apparatus restored to service. The total down-time required to replace the disabled conveyor with another one may be as little as an hour or two, instead of several days, as hasheretofore been the BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cutaway side elevational view of an apparatus embodying the invention;

FIG. 2 is an enlarged cross-sectional view of the same, taken at 2-2 in FIG. 1;

FIG. 3 is an enlarged vertical sectionthrough the air lock feeder, through which material is fed into the apparatus;

FIG. 4 is an enlarged fragmentary sectional view through the side ceramic blocks, taken at 4-4 in FIG.

FIG, 5 is a cross-sectional view taken at 5-5 through FIG. 4, showing one of the key members that secure the edges of the ceramic blocks against relative movement; and

FIG. 6 is a perspective view of one of the side ceramic blocks.

DESCRIPTION OF PREFERRED EMBODIMENT In the drawings, the apparatus of the present invention is designated in its entirety by the reference nu-, meral 1'0 and comprises an elongated chamber 12 having generally rectangular sides, top and ends, said chamber being enclosed and substantially air-tight. At one end of chamber 12 is an entryway 14, which is .normally closed by a removable panel 16, the details of which will be described presently.

The chamber 12 has a structural framework consisting of spaced-apart, vertical posts 18 along both sides thereof. the bottom ends of which are embedded in a concrete floor 20. Posts 18 are arranged in pairs on opposite sides of the chamber and their top ends are connected by transverse beams (not shown). The outer side walls and end walls of the chamber are made up of rectangular upper panels 22 and lower panels 24, made of steel plates, the edges of which are turned outwardly to form flanges 26 that are secured together by bolts 28. Extending across the top of the chamber are horizontal top panels 30, which are bolted along their edges to the top edges of the upper side panels 22, and are therefore readily removable.

Within the outer shell formed by

panels

22, 24 and 30 is an inner lining 32 of high-temperature ceramic blocks, comprising side blocks 34 and top blocks 36. The top blocks 36 extend transversely across the width of the chamber and rest at their edges on the top edges of side blocks 34. The central portion of the top blocks projects for the short distance down into the space between the side blocks, and has a transversely arched underside 38.

Side blocks 34 stand on their ends and are arranged side-by-side. Projecting from the bottom end of each block 34 is a horizontal ledge 40, and extending downwardly from the bottom surface of the ledge 40 is a small, wedge-shaped rib 42. A larger wedge-shaped rib 44 projects downwardly from the underside of the side block 34 at the inside edge thereof, and the two

ribs

42, 44 thus form an inverted V-shaped channel 45. Formed in the side edges of blocks 34 are vertical grooves 46 and horizontal grooves 48, which register with corresponding grooves in the next adjacent side blocks to form keyways 50 (see FIG. 4). The top blocks 36 have similar grooves 52 formed in their side edges, which register with corresponding grooves of the adjacent top blocks to form horizontal keyways for the top blocks.

Positioned within the keyways 50 are key members 54, each of which comprises an elongated ceramic rod of square cross-section, having a cylindrical bore 56. Disposed within bore 56 is a retainer member made up oftwo steel rods 58, having heads 60 at their inner ends which are inserted into opposite ends of a length of steel tubing 62. The ends ofthe steel tubing are swaged over at 64, to form internal shoulders that prevent the heads 60 from being pulled out of the tubing. The outer ends of the rods 58 pass through holes in steel endsplates 66, to which they are welded at 68. The purpose of this construction is to provide a steel retainer, or core, to hold the pieces of the ceramic key members together if the key member should be broken while in place. This enables the broken key member to be extracted in one piece from its keyway, by pulling the exposed end plate 66 outwardly. The inner ends of the rods 58 are free to telescope within the tube 62 so as to allow the retainer to extend and contract with the ceramic body of the key member, said ceramic body having a much greater coefficient of expansion than the steel of the rods. The retainer fits loosely inside the key member when the latter is cold, and as the ceramic heats up and expands in length, the retainer extends with it.

The key members 54 are inserted into the keyways 50 that are formed between abutting side edges of adjacent blocks, each of which side blocks has a short key member disposed within the horizontal keyway formed by horizontal channels 48, and another, longer key member inserted into the vertical keyway formed by vertical channels 46. Long key members 54 are inserted into the channels 52 in the abutting edges of top ceramic blocks 36. The key members 54 prevent relative movement between the side blocks, both in the vertical and horizontal direction, while the key members in the top blocks 36 prevent relative vertical movement between adjacent blocks.

The inner lining of the chamber, consisting of top blocks 36 and side blocks 34, is supported on a plurality of shelves projecting inwardly from the inner surfaces of the posts 18. Each of the shelves 70 has an upwardly facing, semi-cylindrical seat 71, in which the bottom end of the small, wedge-shaped rib 42 is seated. Thus, the ceramic blocks 34 are supported on the shelves 70 and the top blocks are supported. in turn, on the top ends of the side blocks. The side blocks are all keyed together by key members 54 seated in horizontal grooves 50, which prevents vertical movement of the blocks with respect to one another. There is a substantial space between the side blocks 34 and upper side plates 22, and between the top blocks 36 and top plate 30, and this space is filled with thermal insulation material of any suitable type. Passing through the posts 18 on one side of the chamber are U-shaped radiant heater tubes 74, which are heated internally by means of flames fueled by gas, oil, or other fuel. The radiant heaters 74 might also be in the form of electric resistance heaters, if desired.

Fastened down to the concrete floor 20 is a pair of laterally spaced tracks 76, which extend the full length ofthe chamber 12, and out through the entryway 14 for at least an equal distance. Running on the tracks 76 are wheels 78 supporting a frame 80, made up of lengthwise extending steel beams. The steel beams of frame 80 extend through the movable lower end wall 16, as shown in FIG. 1, and a portion of the frame, together with a pair of supporting wheels 78, lies on the outside of the end panel.

Frame 80 carries a shaker conveyor 82, which consists ofa flat table 84 made up of steel plates. The table 84 is supported on a plurality of spring legs 86, which are mounted, in turn, on the frame beams 80. A motor 88 vibrates table 84 through a flywheel pulley 90, driven by a belt 92, and the flywheel pulley 90 has a crank 94 which is connected to the left-hand end of table 84 by means of a link 96, pushrod 97 sliding through a bushing 98 in lower end wall 16, and a short link 99. Link 99 is connected to a bracket 100 fixed to the underside of the table 84. As the pulley 90 is rotated by motor 88, the table is driven back and forth on its longitudinal axis, the movement of the table being accommodated by the spring legs 86, which flex in the fore-and-aft direction. Material on the top surface of conveyor 82 spreads out evenly on the conveyor table and works its way along at a rate determined by the frequency of the back-and-forth movement of the table.

The table 84 has upstanding side walls 102, and end walls 103, and covering the top of the table is a layer of insulation 104, which is overlaid by a ceramic lining 106. The conveyor 82 has thus a channel-shaped configuration, as shown in FIG. 2, with the sides extending up into the inverted V-shaped channels 45 in the bottom ends of side blocks 34. The wedge-shaped ribs 44 projecting downwardly from the inner sides of the side blocks overlap the upper edges of the conveyor sides, with sufficient clearance between them so that the conveyor table can reciprocate without rubbing against the ceramic blocks. The overlapping configuration provides a radiant heat guard, which prevents loss of heat at this point. The end walls 103 of the conveyor table 82 are somewhat lower than the side walls 102, so as to provide clearance to enable the ends to pass under the downwardly projecting ribs 44 of the side and end blocks 34 when the conveyor is rolled into or out of the chamber 12.

The end wall to the left-hand end of chamber 12, as viewed in FIG. 1, is like the side walls in the respect that it is made with two panels; an upper panel 22 and the removable lower end panel 16', the horizontal line of separation between them being somewhat higher than on the side walls, to permit the conveyor 82 to pass through. As seen in FIG. 2, the side walls of the conveyor extend upwardly above the line of separation of the upper and

lower side panels

22 and 24. Except for this difference, and the fact that the lower end panel 161s attached to the conveyor frame 80 and removable therewith, the ends of chamber 12 are constructed the same as the sides.

Material to be treated in the apparatus is fed into the chamber 12 through an airlock feeder 108, the internal construction of which is shown in FIG. 3/Feeder 108 comprises a hopper 110, which empties into a cylindrical chamber 112, with a discharge chute 114 at the bottom thereof, which drops the material onto the receiving end of the conveyor 82. Rotatably disposed within the chamber 112 is a spider 116 mounted on a shaft 117, the said shaft being driven slowly by a motor (not shown) in either direction of rotation. The spider 116 has pockets 118 into which waste or other material is dumped, and shearing cutters 120 at the bottom end of hopper 110 cooperate with the companionate cutters 120 on the spider so as to cut any of the material that may be partly in the pockets 118 and partly in the hopper 110 as the spider revolves. If the spider should become jammed, it can be reversed, so that the jam can be elcaredsGas injection ports 124 are provided in the sides ofthe chamber 12 at 2,468 and 10 oclock. Ports at 2,4,8 and 10 oclock are connected to a suction line (not shown) and as the pockets 118 pass these ports, air entrained in the pockets is partially exhausted by suction, so that the amount ofair entering the chamber at this point is held to a minimum. The'port at 6 oclock is connected by a pipeline to a blower (not shown) which blows some of the gas generated within the chambber 12 into the pocket 118, so as to dislodge any material clinging to the pocket and cause it to fall into the chamber.

At the discharge end of the conveyor 82 is a discharge chute 126, which extends downwardly from the bottom end of table 84, and this empties into a hopper 128 at one end ofa conveyor tube 130. The hopper 128 is cut away on the left-hand side (as viewed in H0. 1) to provide clearance for the discharge chute 126 as the latter moves into place or out of place with the conveyor 82 and frame 80. Rotatably disposed within the tube 130 is a worm screw conveyor 132, which is driven by a motor 134 and gears 136. The conveyor tube 130 passes through the bottom end ofa water tank 138 which cools the tube and its contents; said water tank being located outside of the chamber end wall 24'. The charred residue discharged from the conveyor 82 after being pyrolyzed within chamber 12 is thus cooled down to a temperature suitable for handling, and is discharged through an airlock discharger 140, which is essentially the same as airlock feeder 108.

Gases generated by pyrolytic decomposition of the waste material, or vapors distilled from ore, are removed from chamber 12 by ducting 142, which-is connected to one end of the chamber. Ducting 142 goes to a blower (not shown) and to a scrubber or other processing apparatus, depending upon the nature of the gas being generated.

During normal operation of the apparatus 10, the conveyor 82 and its supporting frame 78 are enclosed within the chamber 12, as shown in FIG. 1, and end wall 16 is securely fastened in place, forming a substantially airtight seal at that point. The interior of the chamber is heated up to pyrolyzing temperature by the radiant heater tubes 74, and carbonaceous waste material or ore to be processed, is fed into the chamber through the airlock feeder 110, while the atmosphere within the chamber is exhausted through the outlet ducting 142. Waste material discharged by the airlock feeder 108 lands on the receiving end of conveyor 82, which is being reciprocated by motor 88 and connected driving equipment, and by reason of such reciprocation of the table, the material works its way gradually down to the other end of the conveyor table, spreading out uniformly over the table as it goes.

Inasmuch as substantially all of the air is exhausted from the chamber through ducting 142, there is not enough oxygen to support combustion, and any carbonaceous material is broken down by pyrolytic decomposition, forming carbon-containing gas. which is removed by the ducting. In the case of cinnabar ore, mercury vapor would be released by the ore as the ore is roasted at high temperature, and such mercury vapor is then withdrawn and condensed by conventional condensing apparatus. The charred residue (or spent ore) is discharged from the discharge chute of conveyor 82 onto conveyor 130, where the worm screw conveyor 132 moves it. endwise to the airlock discharger I40, where it is dumped out onto the ground for disposal.

If the conveyor mechanism 82, or its operating mechanism, should become disabled, the removable end wall 16 is released from its chamber walls, and the entire conveyor with the attached end wall 16 is pulled out of the chamber on tracks 76 and moved off to a suitable repair station. A standby conveyor can be immediately wheeled into the waiting chamber 12, and the apparatus can be back in operation with only a relatively short interruption, and without cooling the chamber 12.

Should any of the ceramic blocks 34 or 36 become damaged or deteriorated by long exposure to the high temperature within the chamber, it is a simple matter to remove and replace any one or more of the blocks by merely removing the corresponding side panel 22 or top panel 30, taking out the insulation 72, and replacing the damaged or deteriorated ceramic blocks. The ceramic blocks are removed by first extracting the key members 54 from their channels on both sides of the block to be removed, which permits any one of the side blocks 34 to be withdrawn from between its next adjacent side blocks. When the new ceramic block has been inserted in place and keyed to its adjacent blocks, the insulation 72, and

outer panels

22 and 30 are replaced.

While I have shown and described in considerable detail what I believe to be the preferred embodiment of my invention, it will be understood by those skilled in the art that the invention is not limited to such details, but may take various other forms within the scope of the following claims.

What I claim is:

1. Apparatus for pyrolytic decomposition of organic material, comprising:

an enclosed chamber comprising a structural framework, an air-tight outer shell, and an inner ceramic lining for thermal insulation and to reflect heat;

said outer shell being made up of a plurality of plates mounted on said framework and separately removable therefrom to provide access from the outside to any desired portion of said lining for repair purposes;

said lining comprising a plurality of separate ceramic blocks which are loose-fitting for expansion, and the blocks forming the side walls of said chamber being joined together at their abutting edges by removable keys seated in grooves in the blocks;

the blocks forming the side walls of said lining having portions thereof standing on supports formed by said framework;

said blocks being individually removable for replacement purposes by first withdrawing said keys from opposite side edges of the block to be removed;

means for heating the interior of said chamber up to a temperature at which pyrolytic decomposition of said material takes place;

a conveyor mounted within said chamber and extending the length thereof, said conveyor having a receiving end and a discharge end;

supply means, including a first air lock, for introducing material from outside said chamber to said receiving end of said conveyor;

discharge means, including a second air lock, for receiving the charred residue from said discharge end of said conveyor, and removing it from said chamber; and

means for drawing off gases generated by the pyrolytic decomposition of said material.

2. The apparatus of claim I, wherein said chamber includes vertical supporting posts between laterally adjacent pairs of steel plates. said supporting posts having shelves projecting horizontally inward, and the bottom edges of said ceramic blocks resting on said shelves for support.

3. The apparatus of claim 2, wherein said means for heating the interior of said chamber comprises radiant heating tubes passing through said supporting posts above said conveyor and extending transversely across the interior of the chamber.

4. The apparatus of claim I, wherein each of said side ceramic blocks has horizontal and vertical channels formed in their abutting edges, which cooperate to form horizontal and vertical keyways between each pair of blocks; and

removable key members inserted into said vertical keyways and into said horizontal keyways, whereby each pair of abutting blocks is held against horizontal and vertical movement with respect to one another.

5. The apparatus of claim 1, wherein said conveyor has a ceramic lining on its top side, said ceramic lining including upwardly projecting side flanges that extend above the bottom edges of the side blocks on the outside thereof, in an overlapping manner, whereby a radiant heat shield is provided at this point.

6. The apparatus of claim 1, wherein said conveyor is reciprocably mounted on a supporting frame having wheels that run on tracks extending the length of said chamber and out through one end thereof, said one end of said chamber having an opening through which said conveyor and its supporting frame can pass;

a vertical wall mounted on said supporting frame near one end thereof, said vertical wall cooperating with the edges of said opening in said one end of said chamber to form an airtight closure therefor that is removable with said conveyor and its supporting frame; and

means mounted on said supporting frame on the outside of said vertical wall for reciprocating said conveyor, said means being connected to said conveyor by motion-transmitting means passing through said vertical wall.

7. The apparatus of claim 6, wherein said conveyor is supported on said frame by means of a plurality of generally vertically extending spring legs that bend in the fore-and-aft direction to provide reciprocating support for the conveyor; and

said motion-transmitting means comprises a push-rod passing through said vertical wall and slidably supported thereon, the inner end of said push-rod being connected to said conveyor, and the outer end thereof being connected to said conveyorreciprocating means. 7

8. The apparatus of claim 1, wherein the top ceramic blocks forming the ceiling of said chamber are elongated and span the full width of said chamber, with their ends resting on the top ends of said blocks forming the side walls of the chamber, said top blocks being loose-fitting for expansion and being secured to one another by keys inserted in horizontal grooves formed in the facing edges of adjacent blocks.

9. The apparatus of claim 1, wherein said discharge means includes a water-cooled conveyor for cooling the hot charred residue prior to discharging the same.

Claims

1. Apparatus for pyrolytic decomposition of organic material, comprising: an enclosed chamber comprising a structural framework, an airtight outer shell, and an inner ceramic lining for thermal insulation and to reflect heat; said outer shell being made up of a plurality of plates mounted on said framework and separately removable therefrom to provide access from the outside to any desired portion of said lining for repair purposes; said lining comprising a plurality of separate ceramic blocks which are loose-fitting for expansion, and the blocks forming the side walls of said chamber being joined together at their abutting edges by removable keys seated in grooves in the blocks; the blocks forming the side walls of said lining having portions thereof standing on supports formed by said framework; said blocks being individually removable for replacement purposes by first withdrawing said keys from opposite side edges of the block to be removed; means for heating the interior of said chamber up to a temperature at which pyrolytic decomposition of said material takes place; a conveyor mounted within said chamber and extending the length thereof, said conveyor having a receiving end and a discharge end; supply means, including a first air lock, for introducing material from outside said chamber to said receiving end of said conveyor; discharge means, including a second air lock, for receiving the charred residue from said discharge end of said conveyor, and removing it from said chamber; and means for drawing off gases generated by the pyrolytic decomposition of said material.

2. The apparatus of claim 1, wherein said chamber includes vertical supporting posts between laterally adjacent pairs of steel plates, said supporting posts having shelves projecting horizontally inward, and the bottom edges of said ceramic blocks resting on said shelves for support.

4. The apparatus of claim 1, wherein each of said side ceramic blocks has horizontal and vertical channels formed in their abutting edges, which cooperate to form horizontal and vertical keyways between each pair of blocks; and removable key members inserted into said vertical keyways and into said horizontal keyways, whereby each pair of abutting blocks is held against horizontal and vertical movement with respect to one another.

6. The apparatus of claim 1, wherein said conveyor is reciprocably mounted on a supporting frame having wheels that run on tracks extending the length of said chamber and out through one end thereof, said one end of said chamber having an opening through which said conveyor and its supporting frame can pass; a vertical wall mounted on said supporting frame near one end thereof, said vertical wall cooperating with the edges of said opening in said one end of said chamber to form an airtight closure therefor that is removable with said conveyor and its supporting frame; and means mounted on said supporting frame on the outside of said vertical wall for reciprocating said conveyor, said means being connected to said conveyor by motion-transmitting means passing through said vertical wall.

7. The apparatus of claim 6, wherein said conveyor is supported on said frame by means of a plurality of generally vertically extending spring legs that bend in the fore-and-aft direction to provide reciprocating support for the conveyor; and said motion-transmitting means comprises a push-rod passing through said vertical wall and slidably supported thereon, the inner end of said push-rod being connected to said conveyor, and the outer end thereof being connected to said conveyor-reciprocating means.