Note: Descriptions are shown in the official language in which they were submitted.
CA 02339245 2008-04-29
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CA.Pat.Ap.No: 2,339,245
Substitute Specification
submitted April 2008
Title: FARM COMPOSTING SYSTEM
[001] This invention relates to the processing of animal and
vegetable waste by composting, on farms, and in particular to the
automation and improvement of agricultural composting.
BACKGROUND TO THE INVENTION
[002] The traditional systems for the disposal of waste
agricultural materials such as pig manure are being increasingly
criticised on environmental grounds. An aim of the invention is
to make it possible to dispose of animal manure, especially pig
manure, by adding the manure into a composting system. The
systems as described herein are aimed at converting pig manure
and other organic waste materials into useful material such as
fertiliser, in a manner that achieves the conversion more
economically and efficiently (and therefore more cost-
effectively) than has been the case hitherto.
[003] The mechanically-sophisticated composting systems as
described herein, though developed mainly for disposing of pig
manure, also dispose of the solid waste material, i.e the
material other than the pig manure, in the compost. The systems
can be utilised for disposing of vegetable and animal waste
generally, as compost.
GENERAL FEATURES OF THE INVENTION
[004] The scope of the invention is defined by the
accompanying claims.
[005] Composting systems of the type with which the
invention is concerned include bays or troughs, in which the
solid material to be composted is heaped. It is an aim of the
present invention to add mechanical sophistication to the
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processing apparatus, which makes it possible to control the
composting system parameters. It is an aim of the invention to
control and manipulate the process so closely that differences in
conditions between different areas of the batch of material can
be evened out, thereby rendering the batch more homogeneous.
Concentration can be brought to bear on those areas of the batch
where composting is proceeding only slowly, whereby all the
portions of the batch can gradually be brought to maximum
efficiency. In a conventional composting system, it is the
presence of slow-to-react regions that delay the completion of
the batch. An aim of the invention is to eliminate the slow-to-
react regions. That being done, the effect is to reduce the
overall time of an aerobic composting session from the usual
minimum thirty days to, often, as little as twenty days. With
conventional systems, only some regions of a batch were composted
at twenty days; with the invention, the aim is to have the whole
batch composted in that time.
[006] The invention is mainly intended for use with batch-
processing of compost, as distinct from continuous processing.
In continuous processing, typically, fresh material to be
composted is added at one end to the trough every day, and the
material gradually works its way along the trough (by mechanical
manipulation) to the other end of the trough, in a sufficient
number of days that composting is completed. However, it is
difficult to achieve a consistent output with a continuous
process, in that, since Tuesday's material remains separated from
Monday's material throughout the process, it is difficult to even
out variations in the material. With batch processing, the
material can be mixed together, which evens out the day-to-day
variations. An aim of the invention is to enable the mechanical
manipulation needed for mixing the material (which thereby evens
out variations in the material), to be combined with the
mechanical manipulation needed for turning, lifting, and aerating
the material (which thereby promotes the bio-chemical composting
reactions).
[007] The apparatus as described herein may be used
predominantly as a means for disposing of the pig manure. Pig
manure being mainly liquid, it is difficult and expensive to turn
pig manure into useful fertiliser. Pig manure generally will not
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compost itself of its own accord, but rather it has to be mixed
with some solid carbonaceous vegetable matter in order to create
the conditions in which the (aerobic) micro-biological composting
reactions can commence.
[008] In treating the pig manure, if the required
carbonaceous vegetable matter is available on the farm (corn
cobs, straw, etc), that can be used. If not, solid carbonaceous
material should be brought in. Brought-in material can be e.g
sawdust from a sawmill; carbonaceous material diverted from a
landfill, e.g leaves, paper, etc; or such other carbonaceous
degradable material as can be obtained cheaply.
[009] The mechanical sophistication needed for the tight
control of the process is achieved by arranging for an apron to
traverse back and forth through the composting material. The
apron carries moving blades for lifting and turning and aerating
the composting material. As described, the apron is two-sided;
that is to say, the apron can be set to operate in either
direction along the trough, and the blades are arranged for
direct contact with the material in both directions of traverse.
[0010] With the use of the apparatus as described herein,
because of the ability for close control of the composting
processes, it becomes worthwhile to monitor the parameters of the
composting reactions closely, and to make changes accordingly.
Treatment materials can be added, aeration can be applied,
traverse speeds and traverse frequency can be changed, and so
forth. The apparatus can be adapted for slowing down the
traverse speed of the apron in areas where aeration is not so
advanced, enabling an increased manipulation of the material, to
break the material up and expose it to the air to a greater
extent in those areas.
[0011] The apparatus can be set for traversing the apron back
and forth. That is to say, the apparatus is such that the apron
can be reversed. Now, in this kind of processing, the apron lies
at a substantial angle to the vertical, typically thirty degrees;
so, in order to reverse the apron, the apron has to go through a
position where the apron is upright. As such, the apron has to
be lifted (i.e raised up off the floor of the trough) to enable
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the apron to pass through the upright position. Means for
raising the apron, for reversing the apron, are provided in the
apparatus as described herein.
[0012] The ability to raise the apron means the apron can be
traversed back and forth over and through the composting
material. The system can be made very sophisticated, with
instrumentation, fine tuning of liquid spray to achieve moisture
content, air blasting to give the right oxygen content, and, as
mentioned, the means to render the batch as homogenous as
possible. With conventional systems, it was not possible to
refine the composting process, because close control of the
process was not available. It is an aim of the invention that
the system now can be refined to the extent as to make it
worthwhile to automate the control of the composting process.
[0013] Preferably, in the case where the composting process
is being carried out primarily as a way of disposing of liquid
manure, the spreading of the liquid manure onto the solid
carbonaceous material can be automated and controlled. The
material can be monitored for moisture content, and the liquid
sprayed accordingly.
THE PRIOR ART
[0014] Patent publications US-5,459,071 (Finn, Oct 1995);
US-5,405,780 (Hamilton, Apr 1995); and US-5,149,196 (Piacentino,
Sep 1992) might be considered relevant to the present invention.
However, the apparatus illustrated in these publications have not
had the ability for the close control of the parameters that
comes from back and forth movement of the apron, as described
herein.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0015] By way of further explanation of the invention,
exemplary embodiments of the invention will now be described with
reference to the accompanying drawings, in which:
Fig 1 is a pictorial view of a trough containing composting
_ . : ,.,.,..~..~q
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material, showing a composting system that is an embodiment
of the invention;
Fig 2 is view of a section of the trough of Fig 1;
Fig 3 is a diagrammatic side elevation of the trough of Fig 1,
showing some of the modes of movement of the apparatus;
Fig 4 is an end elevation of an apron of the apparatus;
Fig 5 is a side elevation of the apron;
Fig 6 is a side elevation of a carriage of the apparatus showing
the manner of mounting and moving the apron;
Fig 7 is a corresponding view to Fig 6, of a modified apparatus;
Fig 8 is an end elevation of the apparatus of Fig 7;
Fig 9 is a pictorial view of some of the components of the Fig 7
apparatus;
Fig 10 is a plan view of an area in which a number of troughs are
arranged side by side.
[0016] The apparatus shown in the accompanying drawings and
described below are examples which embody the invention. It
should be noted that the scope of the invention is defined by the
accompanying claims, and not necessarily by specific features of
exemplary embodiments.
[0017] Fig 1 shows a bay or trough 20 on a farm, in which is
received a body 23 of solid compost material. A batch of the
solid material is placed in the trough by means of a front-end-
loader or the like. Alternatively, placement of the material in
the trough 20 can be automated, e.g by conveyors, if desired.
The solid material is predominantly vegetable waste matter from
the farm, but solid material can be brought in if more is
required.
[0018] The trough 20 comprises a floor 24, and left and right
walls 25. Surmounting the walls are respective rails 26, for
guiding a carriage 27 for movement along the trough. The apron
28 for turning the material being composted is supported from the
carriage.
[0019] The carriage 27 has four flanged wheels 29, which run
on the rails 26. The wheels are driven by respective hydraulic
motors, shown diagrammatically at 31. Hydraulic fluid for the
motors (and other hydraulic components) can be derived from a
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source mounted on board the carriage, and controlled remotely; or
the hydraulic fluid can be pressurised elsewhere, and conveyed to
the motors via hoses.
[0020] The walls 25 of the trough are of concrete. The
concrete can be cast in-situ; preferably, however, the floor and
walls of the trough are formed as a pre-casting 30 (Fig 2).
Typically, the walls are 2 metres high, and the trough is 21/2 to
3 metres wide. A typical trough might be 30 metres long. It is
important that the walls of the trough be formed accurately:
first, because the rails need to be accurately aligned in order
to guide the flanged wheels; and second, because the apron should
be guided to run close to the side walls of the trough but
without actually touching. Achieving the required degree of
accuracy in the case of in-situ casting is very difficult -- and
it may be noted that correcting a mis-cast trough wall is next to
impossible.
[0021] The pre-cast concrete sections 30 are made in trough-
lengths of 3 metres, for easy transport (by truck) to the farm.
The sections 30 can be joined together by welding suitably
prepared extensions of the steel reinforcing-bars in the
concrete. Similarly, the rails 26 also are attached to
extensions of the reinforcing-bars.
[0022]- The sections 30 are provided with a central gutter 32,
for receiving excess liquid that might seep down from the
material being composted. Arrangements are made for draining the
liquid away from the gutters. The gutter is provided with access
ports 34, through which air can be blown to clear the gutters.
[0023] Suitable air-passageways 35 are provided in the
concrete to enable air to be conveyed periodically, as desired,
into the material contained within the trough, for aerating the
material.
[0024] Fig 3 shows the manner in which the apron 28 can be
moved and adjusted as to its position relative to the carriage
27. When the carriage is traversing from left to right in Fig 3,
the apron is set to position D, i.e with the bottom 36 of the
apron leading. When the carriage is traversing from right to
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left, the apron is set to position B, i.e with the bottom 36 of
the apron again leading. As to the motion of the rakes 37, for
traversing to the left in position B the rakes are driven
clockwise around the apron, and for traversing to the right in
position D the rakes are driven anti-clockwise around the apron.
[0025] The rakes 37 are coupled to chains 38, and driven
endlessly around the frame 39 of the apron. The rakes 37 lift
and turn the material, exposing the material to the air. The
ensuing mechanical agitation caused by the rakes also has the
effect of stirring the material, thereby tending to even out any
differences in the consistency thereof.
[0026] When reversing the direction of traverse of the
carriage 27, it is required to change the angle of the apron 28,
i.e from thirty degrees to the left to thirty degrees to the
right. The change in the angle of inclination of the apron is
performed by rotating the apron about an apron-pivot axis 40.
[0027] In changing the angle of inclination from B to D, the
apron passes though an upright position, being position C in
Fig 3. Given that the bottom 36 of the apron should run fairly
close to the floor 24 of the trough during traversing, the apron
has to be raised, i.e lifted up, as it passes through position C.
This lifting of the apron is achieved in the present instance by
raising the pivot 40. The angle of inclination during traversing
being 30 degrees, the pivot 40 has to be lifted a distance equal
to the radius of the apron, i.e the radius from the pivot 40 to
the bottom 36, multiplied by 0.27. Thus, where the apron 28 has
a radius of 2 metres, the lift distance should be 54 centimetres.
[0028] For effective manipulation of the material being
composted, the bottom 36 of the apron 28 should run close to the
floor 24 of the trough 20. However, preferably the bottom 36
should not actually touch the floor, since if it did the bottom
36 might snag on the floor, and that might tend to jam the apron.
Optionally, a slipper placed on the bottom 36 might reduce the
possibility of snagging. The direction of travel of the rakes is
set, in both directions of traverse, such as to lift the material
upwards, and the reaction to such lifting presses the apron
downwards. A slipper might be useful in relieving some of that
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reaction from the area of the pivot 40; however, the apparatus
preferably should be designed so as to support the reaction
forces in the apron-pivot area, and thereby avoid the need for
slippers on the bottom of the apron.
[0029] It is possible that too heavy a force might be placed
on the apron during traversing of the carriage, such that the
trailing wheels 29 of the carriage 27 might tend to lift off the
rails 26. If the designer wishes to avoid that possibility, a
sensor can be placed in the trailing wheels, whereby, if the
component of the weight acting on the trailing wheels should get
too close to zero, the speed of traverse can be slowed down.
[0030] The structure of the apron is shown in Figs 4 and 5.
The frame 39 comprises a triangulated lattice of bars, to which
are attached side plates 42, and face plates 43 which merge into
curved end plates 45. The rakes 37 are fixed to chains 38.
Chain wheels 46 guide the chains 38 for endless motion. A chain
tensioner may be included. The chain wheels 46 are driven by a
hydraulic motor 47.
[0031] The apron can be in two (or more) sections (divided
along a vertical line) the rakes in the different sections being
drivable at different speeds. This refinement permits a degree
of enhancement in the manner of manipulating the compost
material.
[0032] Support for the forces acting on the apron are
transferred to the carriage through the apron-pivot 40. The
pivot is formed from co-axial stubs 48, which are bolted to the
side plates 42 of the apron. The stubs carry respective gear
pinions 49, which are keyed against rotation relative to the
stubs 48. Changes in the angle of inclination of the apron are
effected by rotating the gear pinions 49. Changes in the height
of the apron are effected by raising the stubs 48.
[0033] The mechanisms for rotating the pinions 49, and for
raising/lowering the stubs 48, are located in the carriage 27,
and will now be described.
[0034] The carriage 27 (Fig 6) includes a slideway 50, in
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which a slide 51 is guided for vertical up/down movement. A
hydraulic slide-ram 52 controls the height of the slide 51. The
slide includes a bearing 53, in which is mounted the appropriate
one of the stubs 48 of the apron. The pinion 49 is assembled to
the stub 48 after the stubs have been mounted in the bearing 53
(and in the corresponding bearing on the other side of the
carriage).
[0035] Mounted on the slide 51 is a guideway 54, which guides
a rack 56 for up/down movement relative to the slide. The height
of the rack 56 is controlled by a rack-ram 57. The rack 56 is in
mesh with the pinion 49, and as the rack is driven up/down, the
pinion is driven to rotate. It will be noted that, the rack 56
being mounted on the slide 51, the pinion can be rotated (and
thus the angle of inclination of the apron 28 can be changed) at
any height of the slide 51.
[0036] As intimated above, components corresponding to the
slide, slideway, rack, pinion, bearings, rams, etc, as just
described, are repeated on the other side of the carriage.
[0037] Figs 7 to 9 show a different type of mechanism for
raising/lowering the apron 28, and for changing the angle of
inclination of the apron. Here, the carriage is provided with an
arm 58, which pivots about an arm-pivot 59. The arm 58 is
raised/lowered by means of an arm-ram 60. The arm 58 is also
provided with a bearing 62, which carries the stub 48 of the
apron. A rack-ram 63 is mounted along the length of the arm 58,
and is coupled to a rack 64, which is guided in a guideway 65,
whereby actuation of the rack-ram 63 is effective to rotate the
apron, again independently of the height at which the arm might
be set. The compactness of the pivoting-arm design is an
attractive feature of this version, as shown in Fig 7.
[0038] In use of the apparatus, the material to be composted
is loaded into the trough in some suitable manner, for example by
a front-end-loader, or by a conveyor, etc. At first, the batch
of material is non-homogenous, including pockets or clumps of
wet, solid, compacted material, clumps of dry material, heavy
pieces, light pieces, and so on. The micro-biological composting
reactions start to get under way, however, provided the
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constituents of carbon, nitrogen, moisture, etc are present.
[0039] Periodically, the apron is passed through the batch of
material in the trough. The carriage can be set to traverse
along the trough at a speed of about a metre per minute. The
rakes 37 are set to move over the face of the apron at a speed of
about 2 metres per minute, lifting and turning the material, and
transporting the material up and over the apron. From there, the
material falls down, and forms a heap behind the apron. It will
be noted that the apron extends upwards to a height above that of
the trough walls, so the material is tossed quite high in the air
as the apron passes, which gives good aeration. The material
then falls gently down behind the apron, i.e the material is not
compacted in any way, whereby the material remains loose, and
open to the air. Air can be blown in through the air-passageways
35, as well.
[0040] The rakes can be selected to apply a cutting or
shredding action to the material, or merely a lifting action; and
the selection of the rakes can be made in accordance with
determinations as to the conditions of the material being
composted. The traverse speed of the carriage can be adjusted in
response to the nature of the material. If the material is heavy
and difficult to manipulate, that fact is reflected in the
pressure supplied to the wheel hydraulic motors, and the speed of
the carriage can be arranged to slow down where such heaviness is
encountered. Where the material is lighter, however, the
carriage can be advanced at a faster speed. The designer can
also arrange for the speed of the rakes over the apron to be
adjustable, e.g in response to measurements of the consistency of
the material.
[0041] As mentioned, the fact that the traverse speed of the
apron along the trough can be controlled and adjusted gives rise
to improvements in the efficiency of the composting system.
Preferably, the designer should arrange that the speed of
traverse of the apron is a function of the resistance force on
the apron. If resistance is large, which arises if the material
is heavy, the apron slows down.
[0042] The traverse speed of the apron, being the speed of
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the apron 28 along the rails 26, is determined by the hydraulic
motor 31. The speed of the rakes 37 over the face of the apron
28 is determined by the hydraulic motor 47.
[0043] In the preferred control system, the speed of the
rakes over the apron, and therefore the speed of the rake motor
47, is kept constant. The driving forces on the rake motor 47
are measured; that is to say, the power supplied to the motor as
required in order to maintain the speed of the rakes is measured.
The power supplied to the motor may be measured either by
measuring the hydraulic pressure to the hydraulic motor 47, or by
measuring the electric current to the electric motor 47A that
drives the pump 47B that supplies the motor 47 with hydraulic
pressure.
[0044] As the power supplied to the rake motor increases
(indicating a rise in the heaviness of the compost material) so
the speed of the apron traverse motor 31 is reduced. By slowing
the rate of traverse of the apron through the compost material,
so the distance the rakes bite into the compost material per pass
of the rakes is made smaller, and therefore the more finely the
material is shredded and/or aerated.
[0045] The apparatus includes a control system which, by
adjusting the speed of traverse of the apron (via motor 31),
adjusts the distance the rakes advance or bite into the compost
material. The adjustment of the speed of the apron motor 31 is
done in such a manner as to keep constant the force on the rakes
motor 47, i.e the force needed to drive the rakes motor at the
set speed.
[0046] The intent is to homogenise the compost material. In
this context, it may be noted that materials would be classed as
homogenous if, for a given rake speed, the force required to
drive the rakes at that speed is constant, whereby the traverse
speed of the apron through the material would also be constant.
It has been found that, by adjusting the speed at which the apron
traverses in response to changes in the force needed to drive the
rakes at a set speed, the condition is soon reached at which the
force required to drive the rakes at that speed is constant
throughout the batch of material. After that, the apron
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traverses the whole batch of material at more or less constant
speed.
[0047] As mentioned, the designer should arrange the control
system of the apparatus such that the traverse speed of the apron
is a function of the force needed to drive the rakes at the set
speed. This can be done by means of an automated feedback
control system. In the apparatus as described, the hydraulic
rake motor 47 is supplied with hydraulic pressure from a pump
47B, powered by an electric motor 47A. The electric motor 47A
would be sized in the 40HP region.
[0048] The power needed at the apron motor 31 is much smaller
(e.g 4 HP), but again, the power may be derived from a pump 31B
driven by an electric motor 31A. The speed of the hydraulic
apron motor 31 is controlled by a hydraulic valve 80.
[0049] Current to the 40HP electric motor 47A that drives the
apron pump 47B is monitored by means of a current-sensor 82. The
output of this sensor is in the form of a DC signal voltage.
This signal can be fed, via a conventional programmable logic
controller, in which the signal is processed and co-ordinated
with other parameters, to the hydraulic control valve 80. The
heavier the compost material, the larger the current to the motor
47A, the smaller the hydraulic flow to the motor 31, and the
slower the apron advances through the compost material.
[0050] Because the apron can be operated in both directions,
the traversing of the apron can be utilised to control the
conditions of the composting material to a high degree. The
speed of the traversing can be controlled, as mentioned, as can
the frequency with which the traverses are done.
[0051] Liquid manure is sprayed onto the solid composting
material as the apron passes. The liquid manure is fed to the
carriage via a hose pipe 67. The volumetric flow rate of the
liquid manure is controlled in response to the moisture content
of the material. In a case where the main purpose of the
apparatus is to dispose of the liquid manure, the size of the
installation should be such as will absorb all the manure
generated on the farm. In that case, it would be preferred that
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the system be designed so that the available manure would not be
quite enough, and the extra liquid requirement would be supplied
as water. On the other hand, if an excess of manure is present,
and is more than can be applied to the solid material being
composted, and if that excess has to be disposed of separately,
the quantity of the excess now should be quite small, with the
present apparatus. (It may be noted that, prior to installation
of the present apparatus, all the pig manure had to be disposed
of separately.) The composted material from the present
apparatus, into which the liquid manure has been assimilated, can
be used as fertiliser, either on the farm, or for sale. The
organic fertiliser material is in the form of easy-to-handle
solid particles, and is non-smelly, non-polluting, easy to
spread, weed-free, pathogen-free, easily mixed with other
fertilisers, and inexpensive.
[0052] The ability to traverse the apron back and forth
through the material in the trough, coupled with monitoring and
control of the various parameters, enables the composting
reactions to proceed at an even rate throughout the batch of
material. As such, the overall time taken to process a batch of
material is minimised. When the trough reactions are completed,
the material is taken out of the trough, again by front-end-
loader, conveyor, etc. The apron with the moving rakes thereon
can be used as an element in a conveyor system, to transfer the
material out of the trough.
[0053] Because the composting reactions can be made to
proceed so efficiently, by the use of the apparatus as described,
the reactions can cause the temperature in the material to rise
to 60 or 65 degC. If the composting is done in a building, this
can cause the temperature in the air in the building to be too
hot; the heat can be removed by heat exchanger, and can be used
to warm nearby pig-pens, for example.
[0054] It will usually be convenient, on a farm, to provide
more than one trough. Thus, several batches of material can be
processed simultaneously, each at a different reactive stage. On
the other hand, just one trough (i.e just one batch) might be
acceptable where the main purpose of the system is to dispose of
pig manure; the pig manure can be sprayed onto the solid material
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at almost any stage of the composting reaction, whereby the
liquid manure can be disposed of continuously, as it is
generated, whereas the solid material is supplied in batches, say
once a month.
[0055] When a plurality of troughs are provided, just one
apron can be made to serve the several troughs, a means being
provided to retrieve the carriage and apron assembly from one
trough, and transfer it to the next trough. Fig 10 shows a
trolley 68, which is provided with rails to receive the carriage
from the rails of one of the troughs. The trolley is on wheels,
on which it can be moved to transfer the carriage to the next
trough. Fig 10 also diagrammatically shows a post 69 to which is
attached a jib 70. The jib is used to lift the carriage, and
swing it from one trough to the next. The post 69 is removably
attached to the end of the appropriate wall between the troughs.
[0056] It has been determined that extra mechanical agitation
of the composting material can be achieved by attaching a
vibration unit 72 to the apron. The unit is powered
hydraulically, and includes a rotating weight, which imparts a
rapid shaking motion to the apron. These extra modes of movement
have been found efficacious, especially in the initial physical
or mechanical breaking down of the solid material.
[0057] As shown particularly in Fig 1 and Fig 8, the carriage
27 is supported on the tops of the walls 25 of the trough 20, and
bridges or straddles across the trough. The various moving
components and mechanisms for guiding and moving the carriage
along the trough are located above, and out of, the compost
material heaped in the trough. Similarly, the various moving
components and mechanisms for guiding and moving the apron 28
relative to the carriage, both for up/down or height setting of
the apron, and for setting the angle of inclination of the apron,
are located above, and out of, the compost material heaped in the
trough.
[0058] German patent publication number DE-4,236,138 might be
considered relevant background art.
