US3874529A

US3874529A - Refuse loading apparatus

Info

Publication number: US3874529A
Application number: US475134A
Authority: US
Inventors: Cyril R Gollnick
Original assignee: Leach Corp
Current assignee: Leach Co Inc; Leach Corp
Priority date: 1974-05-31
Filing date: 1974-05-31
Publication date: 1975-04-01
Anticipated expiration: 1992-04-01
Also published as: CA1012931A

Abstract

Refuse loading apparatus for use in conjunction with a vehicle having a refuse storage body and a hopper for receiving refuse to be loaded includes a hydraulically operated packer plate for loading refuse from the hopper into the storage body. The packer plate is powered by means of a first pair of hydraulic cylinders which causes rearward and forward motion of the packer plate, and a second pair of hydraulic cylinders which controls the elevation of the packer plate in relation to the bottom of the hopper. A pair of hydraulic valves, mounted on the packer plate and operatively engaged to cam tracks on the side walls of the hopper, sense movement of the packer plate away from the bottom of the hopper and modulate the fluid outflow from respective ones of the second pair of cylinders to maintain the packer plate in close association with the bottom of the hopper for improved loading efficiency.

Description

United States Patent 1 Gollnick 111] 3,874,529 Apr. 1,1975

[ REFUSE LOADING APPARATUS [75] Inventor: Cyril R. Gollnick, Oshkosh, Wis. [73] Assignee: Leach Company, Oshkosh, Wis. 22 Filed: May 31, 1974 [21] Appl. No: 475,134

[52] US. Cl. 214/833 [51] Int. Cl B65f 3/00 [58] Field of Search 214/833, 503; 100/245 [56] References Cited UNITED STATES PATENTS 3.220.586 11/1965 Gollnick 214/833 l 249,243 5/1966 Hcrpick et al. 214/833 3.297.180 1/1967 Park ct al. 214/833 3,739.927 6/1973 Gollnick 214/833 Primary Examiner-David Schonberg Ass/slum E.\'aminer--R. Schrecengost [5 7 ABSTRACT Refuse loading apparatus for use in conjunction with a vehicle having a refuse storage body and a hopper for receiving refuse to be loaded includes a hydraulically operated packer plate for loading refuse from the hopper into the storage body. The packer plate is powered by means of a first pair of hydraulic cylinders which causes rearward and forward motion of the packer plate, and a second pair of hydraulic cylinders which controls the elevation of the packer plate in relation to the bottom of the hopper. A pair of hydraulic valves, mounted on the packer plate and operatively engaged to cam tracks on the side walls of the hopper, sense movement of the packer plate away from the bottom of the hopper and modulate the fluid outflow from respective ones of the second pair of cylinders to maintain the packer plate in close association with the bottom of the hopper for improved loading efficiency.

10 Claims, 10 Drawing Figures PATENIEDAPR 1197s '3 874 529 snansurs I REFUSE LOADING APPARATUS BACKGROUND OF THE INVENTION This invention relates in general to refuse collection and transport vehicles, and more particularly to an improved refuse loading apparatus for such vehicles.

Apparatus for loading refuse and garbage into the body of a refuse collecting and transporting vehicle generally employ a hopper attached to rear of the body into which refuse is dumped by hand, and a packer plate which is brought down and through the hopper to compact and push the refuse away from the hopper and toward the front of the vehicle body. The hopper is typically formed by a pair of spaced-apart side plates and a contoured bottom plate, and the packer plate is typically mounted within the hopper and driven over a defined operating path by means of a hydraulic actuator system which may include one or more pairs of hydraulic cylinders.

In performing the packing operation the bottom edge of the packer plate has heretofore been guided in close association with the bottom of the hopper during the packing portion of its operating cycle by means of opposed guide channels provided on the inside surfaces of the side plates of the hopper housing. Under continued use, these guide channels, which must necessarily resist and absorb the combined force of the hydraulic cylinders utilized to drive the packer plate, have been subject to becoming worn and requiring repair. Furthermore, under certain conditions of use these guide channels may tend to accumulate garbage and other refuse to the point that movement of the guide rollers along the channels may become difficult and undependable, eventually causing the mechanism to jam. The use of such guide channels has also necessitated the use of large load-bearing rollers on the packing plate, as well as a somewhat complex arrangement for spring-loading the rollers so that they may be cammed into and out of the guide channels as the packer plate proceeds through its operating cycle.

Still another problem of using guide channels is that the loading mechanism must be dimensioned according to the size of the hopper being used, which precludes a desired high degree of commonality of parts between different sized hopper assemblies and the obvious manufacturing economies attendant therewith. Thus, the need has developed for a refuse loading hopper apparatus which does not require guide channels on the side plates of the hopper and which is therefore less susceptible to wear and to jamming, and which is more economical to manufacture.

Accordingly, it is a general object of the present invention to provide a new and improved packing apparatus for a refuse vehicle or the like.

It is a more specific object of the present invention to provide a new and improved packing apparatus for a refuse vehicle which is less susceptible to wear and jamming.

It is a more specific object of the present invention to provide a new and improved packing apparatus for a refuse vehicle which does not require guide channels and load-bearing guide rollers and which is more readily adaptable to multiple hopper sizes and configurations.

SUMMARY OF THE INVENTION The invention is directed, in a refuse collection and transport vehicle of the type having a refuse storage body and a hopper for receiving refuse to be loaded therein, to loading apparatus for transporting batches of refuse from the hopper to the storage body. The loading apparatus comprises means including a packer plate for removing refuse from the hopper, and actuating means for urging the packer plate along a defined operating path wherein the packer plate passes through the hopper so as to scoop batches of refuse contained therein into the refuse storage body. Means are provided for sensing separation of the packer plate from the bottom of the hopper and producing a control effect indicative thereof, and means responsive to the control effect are provided for urging the packer plate downwardly toward the bottom of the hopper to maintain the packer plate is close association therewith for improved efficiency in transferring refuse into the storage body.

BRIEF DESCRIPTION OF THE DRAWINGS The features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The invention, together with the further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in the several figures of which like reference numerals identify like elements, and in which:

FIG. 1 is a side elevational view of a refuse receiving and transporting vehicle incorporating refuse loading apparatus constructed in accordance with the invention.

FIG. 2 is a rear elevational view of the refuse receiving and transporting vehicle of FIG. 1.

FIG. 3 is a skeletal perspective view of a portion of the refuse receiving and transporting vehicle showing the major components of the refuse loading apparatus of the invention.

FIG. 4 is a side elevational view of the refuse loading apparatus of the invention in an initial position wherein refuse can be loaded into the hopper.

FIG. 5 is a side elevational view of the refuse loading apparatus showing the primary components thereof in a first portion of the loading cycle.

FIG. 6 is a side elevational view of the refuse loading apparatus of the invention showing the primary components thereof in a second portion of the loading cycle.

FIG. 7 is a side elevational view of the refuse loading apparatus of the invention showing the primary components thereof in a third portion of the loading cycle.

FIG. 8 is a fragmentary rear elevational view of the packer partially broken away to show construction of the packer plate height control valves.

FIG. 9 is a cross-sectional view taken along lines 9-9 of FIG. 8.

FIG. 10 is an enlarged view, partially fragmentary and partially in cross-section, of the packer plate height control valve shown in FIGS. 8 and 9.

A DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIGS. 1 and 2, a refuse vehicle 10 incorporating a refuse loading apparatus constructed in accordance with the invention may be conventional in design and construction, comprising a large capacity storage body 11 of horizontally elongated generallyrectangular cross section which is closed at its rear end by an upwardly and forwardly curved tailgate housing 12. The tailgate housing is pivotably connected at its upper edge to the upper edge of the rear end of the storage body, thereby enabling the housing to be swung rearwardly and upwardly into an out-of-the-way position by means of hydraulic cylinders (not shown) or other suitable means when unloading the body.

The tailgate housing 12 is characterized by parallel

vertical side walls

13 and 14, a downwardly and rearwardly sloping rear wall 15, and a forwardly and upwardly sloping bottom wall 16, which together form an upwardly-opening transversely-elongated hopper 17 (FIG. 4) into which batches of loose refuse or garbage are initially dumped through an opening 18 in the rear wall of the housing. The opening 18 is adapted to be closed when not in use by an upwardly and downwardly movable door 20 slidably mounted adjacent the top wall 15. The hopper 17 terminates forwardly with its top, bottom and side walls in registration with like elements of storage body 11.

The opening 18 provided in the rear wall 15 of the tailgate housing 12 is preferably rectangular in shape and has margins spaced inwardly from

side walls

13 and 14 to provide margins 23 and 24 (FIG. 2) at either side for the purpose of guiding the packing plate as its moves across the opening 18, as will be seen presently. A sill 25 may be provided at a convenient height near the bottom of the tailgate so that garbage cans and other refuse containers can be rested at the lower edge of opening 18 prior to having their contents dumped into the hopper.

Referring to FIGS. 3 and 4, a movable packer plate 26 is mounted within tailgate housing 12 for the purpose of transferring from hopper 17 into the storage body 11 refuse which has been dumped into the hopper through the opening 18. The refuse thus transferred is compacted against an upwardly inclined slidably mounted compaction plate 27 within housing 11. Compaction plate 27, which may be positioned within storage body 11 by conventional means such as a hydraulic cylinder and ratchet assembly 29, serves the dual functions of compressing the refuse as it is loaded into the storage body, and of pushing the compacted refuse out the rear end of the storage body when the tailgate housing 12 is pivoted out of position for unloading.

Packer plate 26 comprises a transversely extending forwardly-curved spade-like blade portion 28 which extends from one side of tailgate housing 12 to the other and a pair of upwardly projecting

arms

30 and 31. The packer plate 26 is caused to move forwardly and rearwardly in the tailgate housing 12 by a pair of

hydraulic cylinders

32 and 33, henceforth termed the packer cylinders. The

packer cylinders

32 and 33 are pivotably connected to the packer plate 26 adjacent respective ends of the blade portion 28, and the

actuator rods

34 and 35 of the cylinders are pivotally connected at pivot points 29 to the sides of tailgate housing 12 near the top thereof.

The upwardly projecting

arms

30 and 31 of the packer plate 26 are pivotably connected to the free ends of respective ones of a pair of

torsion arms

36 and 37 through the intermediary of a transversely extending torque tube 38, which is rigidly attached to the free ends of the tortion arms and extends between the same. The other ends of the

arms

36 and 37 are pivotably connected to the

side plates

13 and 14 of the housing at pivot points 39. The movement of

torsion arms

36 and 37 is controlled by a pair of

hydraulic cylinders

40 and 41, henceforth termed the control cylinders.

Control cylinders

40 and 41 are pivotably connected at pivot points 22 to respective ones of the

side plates

13 and 14 of the housing, and the

actuator rods

42 and 43 of these cylinders are pivotably connected to respective ones of

arms

36 and 37 intermediate the ends thereof.

From the foregoing it will be understood that the packer plate 26 is suspended within the tailgate housing 12 in a generally vertical position, for both pivotal and transitory movement, and that the angular position assumed by the blade portion 28, of the packer plate 26, as well as the elevation of the lower edge of the packer blade with respect to the bottom 16 of hopper 17, can be controlled by suitably actuating

packer cylinders

32 and 33 and

control cylinders

40 and 41. To this end, a hydraulic system is provided in connection with the refuse loading apparatus of the present invention wherein the top and bottom ports of

packer cylinders

32 and 33 are connected to respective ports on one side of a four port three position hydraulic control valve 49. One of the ports on the other side of control valve 49 is connected to a hydraulic pump 44, which may be conventional in design and construction, and the remaining port is connected to the reservoir 45 of the hydraulic system. The hydraulic pump 44 may be powered by an electric motor 46, the vehicle engine, or other suitable means.

The bottom ports (closest to actuator rods 42 and 43) of

control cylinders

41 and 41 are connected through pressure relief or

restriction valves

47 and 48 to hydraulic reservoir 45.

Restriction valves

47 and 48, which open in the presence of a predetermined upline pressure, are connected back-to-back, i.e., in reverse directions, so that hydraulic fluid can flow either into or out of the bottom ports of

cylinders

40 and 41 when sufficient pressure is exerted on the pistons of these cylinders. The top ports of

control cylinders

40 and 41 are connected to reservoir 45 by reverse-flow check valves 50, and by respective ones of packer plate

height control valves

51 and 52.

It will be appreciated that while only the hydraulic circuits associated with

hydraulic cylinders

33 and 41 are shown in FIGS. 4-7 for the sake of clarity, in practice

hydraulic cylinders

32 and 40 will also be provided with hydraulic circuits for controlling movement of the other side of the packer plate. These circuits may be separate but identical to the circuits for

cylinders

33 and 41, or may be combined with the circuits for

cylinders

33 and 41 to make common use of one or more circuit components.

In operation, packer plate 26 initially assumes the load-retaining position shown in FIG. 4, its blade portion 28 being forward of hopper 17 for ease of loading. Control valve 49 is positioned in its middle or neutral position at this time, causing the upper and lower ports of

packer cylinders

32 and 33 to be plugged so as to hold packing plate 26 in position.

After the hopper 17 has been loaded with refuse, the packing cycle is initiated by the operator by actuating control valve 49 to its up or right side position, as shown in FIG. 5. This causes hydraulic fluid to be pumped into the bottom ports of

packer cylinders

32 and 33 as hydraulic fluid is allowed to escape from the top ports of these cylinders, so that the cylinders exert an expansive rearward force on the packing plate 26. The effect of restriction valves 47 at this time is to cause

control cylinders

40 and 41 to resist the expansion of

packer cylinders

32 and 33, thereby causing the packer plate 26 to pivot about torque tube 38 upwardly against the top wall of the tailgate housing 12 during this initial portion of the packing cycle. Once the bottom edge of the packer plate has contacted top wall 15, as shown in FIG. 5, the pressure exerted by the

packer cylinders

32 and 33 on the control cylinders is sufficient to open the two restriction valves 47 so that control cylinders and 41 can expand as the packer plate is forced downwardly along the rear wall 15 of the tailgate housing. A pair of rounded

skids

53 and 54 are mounted at opposite sides of packer blade 28 to assist in guiding the packer blade through this portion of the operating cycle. The upper ports of

control cylinders

40 and 41 draw hydraulic fluid from reservoir at this time through check valves 50.

Referring to FIG. 6, after packer plate 26 has swung rearwardly and into contact with the

margins

23 and 24 of the rear wall 15 of the tailgate housing, the continued expansion of

packer cylinders

32 and 33 causes the packer plate to move rearwardly downwardly with its

skids

53 and 54 in guided engagement with

margins

23 and 24. Hydraulic fluid continues to enter the top ports of

control cylinders

40 and 41 at this time by way of check valves 50, as hydraulic fluid exits from the lower ports of these cylinders by way of restriction valve 47, the pressure developed at the outlet ports as a result of the continued expansion effort of

cylinders

32 and 33 continuing to be sufficient to overcome the threshold settings of the restriction valve.

When the packer plate 26, after having swung rearwardly as shown in FIG. 5, and after having moved downwardly as shown in FIG. 6, reaches its lowermost position behind the load of material in the hopper 17, the flow of hydraulic fluid into

packer cylinders

32 and 33 is reversed by actuation of the three-position control valve 49 to the position shown in FIG. 7, whereupon hydraulic fluid flows into the upper ports of

packer cylinders

32 and 33. This brings about a contractive effort from these cylinders as hydraulic fluid now escapes the bottom ports ofthe two cylinders through control valve 49 to reservoir 45. The pull exerted by

packer cylinders

32 and 33 causes packer plate 26 to move forward as shown, forcing the refuse load forward from hopper 17 into housing 11.

As the packer plate 26 is drawn forward by

packer cylinders

32 and 33, it is necessary that the bottom edge of the blade portion 28 of the packer plate be maintained in close association with the bottom wall 16 of the hopper 17 to insure that substantially all of the refuse in the hopper will be scooped into storage housing 11. To this end, and in accordance with the invention, the actuator stems of the packer plate

height control valves

51 and 52 are provided with

rollers

55 and 56, respectively, which operatively engage

cam tracks

57 and 58 mounted in opposing relationship on the inside surfaces of

side plates

13 and 14.

The effect of the height control valves, as seen in FIG. 7, is to control the discharge of hydraulic fluid from the top ports of

control cylinders

40 and 41, the check valves being closed to flow in this direction. By shaping cam tracks 57 and 58 to generally correspond to the shape of the bottom wall 16 of the hopper 17, and by mounting these cam tracks at a fixed vertical spacing therefrom, the packer plate 26 is made to follow at a predetermined close spacing the contour of the hopper bottom. Should the packer blade 28 be forced up for any reason during the packing cycle, as by an obstruction in the hopper, packer plate

height control valves

51 and 52 reduce the outflow of hydraulic fluid from the top ports of

control cylinders

40 and 41 to cause these cylinders to oppose further forward movement of the packer plate. As a result, the packer plate is forced downwardly toward the hopper bottom as

packer cylinders

32 and 33 continue to draw the packer plate forwardly. When the packer plate again obtains the desired spacing from the hopper

bottom valves

51 and 52 open to allow sufficient hydraulic fluid to escape from the top ports of the control cylinders to enable the

packer cylinders

32 and 33 to draw the packer blade 28 smoothly forward.

A possible construction for the two packer plate

height control valves

51 and 52 is shown in FIGS. 8-10. In FIG. 8 the valve actuator rollers and 56 are journaled on the ends of short shafts and 61, which in turn are pivotably mounted behind

protective housings

62 and 63 to the shoulders of the blade portion 28 of the packer plate. The

shafts

60 and 61 operatively engage the actuator stems of

valves

51 and 52 when the idler wheels are raised by

cam tracks

57 and 58. The shafts are urged downwardly away from their associated height control valves by individual helical compression springs 64 which prevent actuation of the valves except in the presence of the cam track surfaces. Hydraulic fluid is carried to and from

valves

51 and 52 by means of hydraulic lines 65, which may contain one or more flexible sections for connection to reservoir 45 and the ports of

control cylinders

40 and 41.

A significant advantage of the present invention is the relative simplicity of the hydraulic circuit associated with

control cylinders

40 and 41. This circuit requires no source of hydraulic pressure, but rather relies on the suction effect produced during the extension of the control cylinders to fill the cylinders, and the contraction effort of the packer cylinders to force oil out of control cylinders during the compression portion of the packing cycle. Since a minimum amount of additional hydraulic components are required, maintenance is minimized and maximum economy in manufacture and operation is achieved.

Since the loading apparatus of the invention utilizes a cam track instead of a channel, the guide rollers are not called upon to support heavy loads, and therefore offer extended life and reduced maintenance. Furthermore, the cam tracks are not susceptible to accumulating refuse and garbage in the manner of a guide channel, making the loading apparatus easier to keep clean and more reliable in operation.

While one particular type of hydraulic circuit has been shown, it will be appreciated that other types of circuit arrangements can be used as well. Furthermore, the invention can be practiced with other types of linkages and cylinder arrangements and with other sizes and shapes of refuse hoppers.

While a particular embodiment of the invention has been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

I claim:

1. In a refuse collection and transport vehicle of the type having a refuse storage body and a hopper for receiving refuse to be loaded therein, loading apparatus for transporting batches of refuse from said hopper to said storage body, said loading apparatus comprising, in combination:

means comprising a packer plate for removing refuse from said hopper;

actuating means for urging said packer plate along a defined operating path wherein said packer plate passes through said hopper so as to scoop batches of refuse contained therein into said refuse storage body;

means for sensing separation of said packer plate from the bottom of said hopper and producing a control effect indicative thereof; and

means responsive to said control effect for urging said packer plate downwardly against the bottom of said hopper to reduce the separation of said packer plate therefrom for improved efficiency in transferring refuse into said storage body.

2. Refuse loading apparatus as defined in claim 1 wherein said actuating means comprise a hydraulic actuator system, and said means for sensing separation of said packer plate from the bottom of said hopper comprise a cam track and a hydraulic valve having an actuating member operatively engaged to said cam track,

3. Refuse loading apparatus as defined in claim 2 wherein said cam track corresponds in shape to the bottom of said hopper, and wherein said actuating member of said hydraulic valve is disposed to move along said cam track as said packer plate moves through said hopper.

4. Refuse loading apparatus as defined in claim 3 wherein said hydraulic valve is carried on said packer plate and movable therewith, and said cam track is disposed at a fixed location relative to the bottom of said hopper.

5. Refuse loading apparatus as defined in claim 2 wherein said actuating means comprise at least a first hydraulic cylinder for urging said packer plate through said hopper, and at least a second hydraulic cylinder for urging said packer plate into engagement with the bottom of said hopper, and wherein said control effect controls the flow of hydraulic fluid relative to said second hydraulic cylinder.

6. Refuse loading apparatus as defined in claim 5 wherein one port of said second hydraulic cylinder is connected to a reservoir of hydraulic fluid by way of said hydraulic valve whereby the flow of hydraulic fluid relative to said second hydraulic cylinder is modulated according to the separation of said packer plate from the bottom of said hopper.

7. Refuse loading apparatus as defined in claim 6 wherein said one port of said second hydraulic cylinder is also connected by way of a check valve to said hydraulic fluid reservoir whereby said second hydraulic cylinder allows said packer plate to freely move toward engagement with the bottom of said hopper, but opposes movement away from the bottom of said hopper except when said hydraulic valve is operatively engaged with said cam track.

8. Refuse loading apparatus as defined in claim 7 wherein said second hydraulic cylinder has a second port, and wherein said second port is connected to said hydraulic fluid reservoir by way of a pair of opposed pressure relief valves which provide flow into or out of said second port when the fluid pressure thereat exceeds a predetermined threshold level.

9. In a refuse collection and transport vehicle of the type having a refuse storage body and a hopper for receiving refuse to be loaded therein, loading apparatus for transferring batches of refuse from said hopper to said storage body, said loading apparatus comprising, in combination:

means comprising a packer plate for removing refuse from said hopper;

actuating means for moving said packer plate along a defined operating path wherein said packer plate passes through said hopper so as to scoop batches of refuse contained therein into said refuse storage body, said actuating means comprising a hydraulic actuator system having at least a first hydraulic cylinder for urging said packer plate through said hopper, and at least a second hydraulic cylinder for urging said packer plate into engagement with the bottom of said hopper;

means comprising a cam track and a hydraulic valve having an actuating member operatively engaged to said cam track for sensing separation of said packer plate from the bottom of said hopper, the position of said valve being dependent thereon; and means including said hydraulic valve for controlling the flow of hydraulic fluid relative to said second hydraulic cylinder according to the separation between said packer plate and the bottom of said hopper whereby said packer plate is maintained in close engagement with said bottom of said hopper.

10. Refuse loading apparatus as defined in claim 9 wherein said cam track is disposed at a fixed location relative to the bottom of said hopper and corresponds in shape thereto, and wherein said hydraulic valve is carried on said packer plate so as to move along said cam track as said packer plate moves through said hopper.

Claims

1. In a refuse collection and transport vehicle of the type having a refuse storage body and a hopper for receiving refuse to be loaded therein, loading apparatus for transporting batches of refuse from said hopper to said storage body, said loading apparatus comprising, in combination: means comprising a packer plate for removing refuse from said hopper; actuating means for urging said packer plate along a defined operating path wherein said packer plate passes through said hopper so as to scoop batches of refuse contained therein into said refuse storage body; means for sensing separation of said packer plate from the bottom of said hopper and producing a control effect indicative thereof; and means responsive to said control effect for urging said packer plate downwardly against the bottom of said hopper to reduce the separation of said packer plate therefrom for improved efficiency in transferring refuse into said storage body.

2. Refuse loading apparatus as defined in claim 1 wherein said actuating means comprise a hydraulic actuator system, and said means for sensing separation of said packer plate from the bottom of said hopper comprise a cam track and a hydraulic valve having an actuating member operatively engaged to said cam track.

9. In a refuse collection and transport vehicle of the type having a refuse storage body and a hopper for receiving refuse to be loaded therein, loading apparatus for transferring batches of refuse from said hopper to said storage body, said loading apparatus comprising, in combination: means comprising a packer plate for removing refuse from said hopper; actuating means for moving said packer plate along a defined operating path wherein said packer plate passes through said hopper so as to scoop batches of refuse contained therein into said refuse storage body, said actuating means comprising a hydraulic actuator system having at least a first hydraulic cylinder for urging said packer plate through said hopper, and at least a second hydraulic cylinder for urging said packer plate into engagement with the bottom of said hopper; means comprising a cam track and a hydraulic valve having an actuating member operatively engaged to said cam track for sensing separation of said packer plate from the bottom of said hopper, the position of said valve being dependent thereon; and means including said hydraulic valve for controlling the flow of hydraulic fluid relative to said second hydraulic cylinder according to the separation between said packer plate and the bottom of said hopper whereby said packer plate is maintained in close engagement with said bottom of said hopper.