Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION:
Mobile Paper Shredder
NAME OF INVENTOR:
David Edward Rajewski
FIELD OF THE INVENTION
This invention relates to methods and
apparatus used in the shredding of paper, and
particularly to mobile paper shredders.
R~rYGROUND AND SUMMARY OF THE INVENTION
In the prior art of which the inventor is
aware, mobile and other paper shredders typically use
knuckle type devices to shred paper. So far as the
inventor is aware, mobile paper shredders, other than
those made by the inventor, achieve shredding rates of
less than 2000 lbs per hour. The slow rate is believed
to be due to the use of slowly rotating pairs of
shafts.
In a mobile paper shredder used commercially
in secret by the inventor and his company in the
United States more than one year before the filing of
this application, the inventor used a mobile paper
shredder using a hammer mill for the shredding of the
paper. The hammer mill included rotating hammers
mounted on a horizontal axis, with the horizontal axis
below a lower confining surface of a tub. The hammers
rotated up into the tub and down in an opening in the
tub, past impact surfaces located on a side of the
opening. Paper caught between the hammers and the
impact surfaces was shredded. Paper was fed to the
opening along the lower confining surface of the tub.
At impact, the striking angle was greater than 30.
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The striking angle in a hammer mill is the angle
between the direction of movement of the hammer at the
point of impact with paper being shredded and the
direction it is desired to send the shredded paper,
that is towards a discharge bin or chute. Since the
direction of feed of shredded paper is normally at
right angles to the direction of ejection of shredded
paper, this is typically equivalent to the angle
between the long axis of the hammers and the direction
of feed.
This design, with a striking angle greater
than 30, proved moderately successful, but was
subject to jamming as the hammers moved past the
impact surfaces. This is believed to be due to the
hammers imparting a component of movement to the paper
in the direction of the impact surfaces, and therefore
leading to bunching of paper between the impact
surfaces and the hammers, thus jamming the hammers.
For a striking angle greater than 30, the force
imparting a component of movement in the direction
towards the impact surfaces is greater than one-half
the force tending to shear the paper.
The inventor proposes a novel construction
of a paper shredder believed to be able to achieve a
shredding rate of up to 8,000 lbs per hour. In one
aspect of the invention, a paper shredding apparatus
including a paper feeder, paper shredder with hammers
and shredded paper unloader has its hammers mounted at
a striking angle of less than 30. It is desirable
that the striking angle be as low as possible (near
zero). However, the limitation that the axle on which
the hammers are mounted be lower than the lower
confining surface of the tub limits the angle to about
10 to 20 in many practical situations.
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Further improvements have also been made to
the design of the previously used paper shredder to
increase the throughput of the paper shredder.
Thus, in one aspect of the invention,
the feeder has a lower confining surface forming a
predominantly horizontal plane, the horizontal axis on
which the plural hammers are mounted lies below the
horizontal plane; and the direction of feed is along
the lower confining surface of the feeder towards the
opening in the shredder.
The unloader preferably includes a bin
formed of a base, first and second sidewalls spaced
from each other and separated by the base, a
reciprocating end wall disposed between the first and
second sidewalls, and an upwardly extending discharge
chute opposed to the reciprocating end wall; and a
motor operatively connected to the reciprocating end
wall such that reciprocation of the end wall compacts
shredded paper within the bin and forces it out of the
discharge chute.
The unloader may further include a shredded
paper storage area bounded by walls, one of the walls
being openable and forming an unloading gate, and one
of the walls being movable across the storage area
towards the openable wall, the discharge chute
disposed to discharge paper into the storage area
through one of the walls.
The paper feeder preferably includes a tub
formed of an encircling wall, and a lower and upper
confining surface, the inlet of the feeder being
formed in the upper confining surface and the outlet
being formed in the lower confining surface, the paper
feeder including a sweeping arm mounted for rotation
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in the tub and to sweep across the lower confining
surface between the encircling wall.
The paper shredder preferably includes a
lifting arm mechanism for lifting and rotating
S initially upright paper containers to empty the paper
containers into the paper feeder, the lifting arm
mechanism including a lifting arm mounted about a
horizontal axis and rotatable from a lower position
for attaching a paper container onto the lifting arm
to an upper discharge position, the lifting arm having
a free end, a detachable latch for a paper container
on the free end of the lifting arm, and means to
rotate the paper container into an emptying position.
There is also preferably included according
to a further aspect of the invention a governor
connected to the paper feeder to regulate feeding of
the rate at which paper is fed into the paper
shredder.
According to an aspect of a method according
to the invention, the following steps are included:
feeding paper into a paper shredder mounted on a motor
vehicle; shredding the paper to produce shredded
paper; compacting the shredded paper to produce
compacted shredded paper; and periodically moving the
compacted shredded paper towards and out of the
unloading gate.
According to a further aspect of the method,
feeding the paper includes feeding the paper into the
paper shredder along a direction of feed; and
shredding the paper includes impacting the paper with
hammers whose striking angle is less than 30.
According to a still further aspect of the
method of the invention, the paper shredder is located
in a lower confining surface of a tub and feeding the
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paper into the paper shredder includes loading paper
into the tub by lifting the paper in a paper container
on a lifting arm to a point above the tub, and
rotating the paper container to discharge the paper
into the tub.
Feeding the paper into the paper shredder
preferably includes moving paper in the direction of
feed with a rotating arm mounted on a central vertical
axis in the tub. Compacting the shredded paper
preferably includes, according to a still further
aspect of the invention, depositing shredded paper in
a bin formed of a base, first and second sidewalls
spaced from each other and separated by the base, a
reciprocating end wall disposed between the first and
second sidewalls, and a discharge chute opposed to the
reciprocating end wall; and reciprocating the end wall
towards and away from the discharge chute.
Periodically moving the compacted shredded
paper includes according to a still further aspect of
the invention depositing compacted shredded paper on
one side of a moving wall; and periodically moving the
moving wall towards the unloading gate. Preferably,
the shredder is a hammer mill and the rate of feed of
paper into the hammer mill is regulated.
BRIEF DESCRIPTION OF THE DRAWINGS
There will now be described preferred
embodiments of the invention, with reference to the
drawings, by way of illustration, in which like
numerals denote like elements and in which:
Fig. 1 is a side elevation showing in
schematic form a mobile paper shredder according to
the invention;
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Fig. 2A is a side elevation of a lever arm
for use in loading paper into the mobile paper
shredder of Fig. 1;
Fig. 2B is a front view of a latch for
5securing a paper container onto the lever arm of Fig.
2A;
Fig. 2C is a detail in side section of the
latch of Fig. 2B;
Fig. 2D is a detail, front view, of the
10latch of Fig. 2D;
Fig. 2E shows the lever arm in an upper
position ready for the discharge of paper into the
paper shredder;
Fig. 2F shows the lever arm in an upper
15position showing the manner of discharge of paper into
the paper shredder;
Fig. 3 is a top view of a feeding tub with
sweeping arm for use with the mobile paper shredder of
Fig. 1;
20Fig. 4 is a top view of a paper shredder for
use with the mobile paper shredder of Fig. 1,
particularly showing the spacing of hammers;
Fig. 4A is a detail showing a governor
connected between the paper shredder shown in Fig. 4
25and the feeding tub sweeping arm shown in Fig. 3;
Fig. 5 is a side view of one set of hammers
in the paper shredder shown in Fig. 4;
Fig. 6A is a perspective view of a compactor
for use with the mobile paper shredder shown in Fig.
1;
Fig. 6B is a side view of a plunger for use
with the compactor of Fig.6A;
Fig. 6C is an end view of a plunger for use
with the compactor of Fig. 6A;
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Fig. 6D is a side section of a track for
carriage of the plunger of Fig. 6B in the compactor of
Fig. 6A;
Fig. 7A is a perspective of a moving wall
for use in an unloader forming part of the paper
shredder shown in Fig. 1;
Fig. 7B is a side section of a catch shown
in Fig. 7A used to link the moving wall to a drive
bar;
Fig. 8A shows a track and drive bar for
moving the moving wall shown in Fig. 7A;
Fig. 8B shows a detail of the drive bar of
fig. 8A; and
Fig. 9 shows a vacuum system for use with
the mobile paper shredder of Fig. 1 used to keep paper
debris to a minimum within the mobile paper shredder.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Fig. 1 shows a paper shredding apparatus
mounted on a truck 10. The major elements of the paper
shredding apparatus are a paper feeder 12, paper
shredder 14 and shredded paper unloader 16. Shredded
paper is discharged from the rear 18 of the truck 10.
The paper feeder 12 includes an inlet 22 and outlet
24.
Paper to be shredded is supplied into the
inlet 22 of the paper shredder through the lifting arm
mechanism shown in Fig. 1 and more particularly in
Figs. 2A-2F. The lifting arm mechanism is formed from
a lifting arm 26 mounted on a pivot 28 that creates a
horizontal axis for rotation of the lifting arm. The
pivot 28 is secured to a post 32 secured as by bolts
to the truck 10. In the example shown, the truck 10 is
a Mack~ truck and the post 32 is mounted between the
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cab 34 and cargo compartment 36. The lifting arm 26 is
rotatable from a lower position (Fig. 1, 2A) for
attaching a paper container (element 38 in Fig. 2E)
onto the lifting arm 26 to an upper discharge position
(Figs. 2E, 2F). The paper container 38 is attached to
free end 42 of the lifting arm 26, and latched onto
the lifting arm 26 by the latch mechanism shown in
Figs. 2B, 2C and 2D. The latch includes a bar 44 that
is pivotally secured to the free end of the lifting
arm 26 by a pin 46. The bar 44 has a depending frame
48 and upwardly directed tabs 52 extending from the
bar 44. A catch bar 54 is rotatably secured along a
pivot line 56 at the end of supports 58 extending
upwardly from bar 44. The catch bar 54 is manually
rotatable by lever 62. To secure a paper container 38
on the latch mechanism, the catch 54 is rotated up and
away from the tabs 5, the lip of the container is set
over the tabs 52, and the catch 54 is replaced. The
paper container 38 is prevented from swinging in
towards the truck by depending frame 48. The paper
container is thus easily detached from the latch by
rotating the catch and lifting the lip of the paper
container off the tabs 52. The lifting arm 26 is
rotated from the lower to upper position by hydraulic
ram 64, which may be conveniently powered through the
truck 10. In the lower position, the paper container
38 is initially upright.
The lifting arm 26 is used to lift the paper
containers 38 into a position ready for emptying.
Means is also provided to rotate the paper container
into an emptying position as shown in Figs. 2E and 2F.
A second hydraulic ram 66 is coupled between a pivot
68 on post 32 and a connector bar 72 that is rotatably
connected to the ram 66 and the free end of the
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lifting arm 66. The bar 44 and connector bar 72 are
rigidly connected to each other. When the lifting arm
26 is in the upper position shown in Fig. 2E,
operation of the ram 66 on the backwards stroke
rotates the paper container 38 into a partially
inverted emptying position shown in Fig. 2F. The lid
74 of the paper container 38 moves away under gravity
from the top of paper container 38 and paper is
disgorged into inlet 22 of the feeder 12 under cover
76.
Referring in particular to Fig. 3, the inlet
22 of the paper feeder 12 is located at one side of a
tub 78 formed of an encircling wall 82, and a lower
confining surface 84 and upper confining surface 86.
The inlet 22 is formed in the upper confining surface
86. The outlet 24 of the feeder 12 is formed in the
lower confining surface 22 spaced from the inlet 22.
Inside the tub 78 is mounted a sweeping arm 88 mounted
for rotation about a vertical axis 92 in the tub 78
and to sweep around the tub above the lower confining
surface 84 within the encircling wall 82. The sweeping
arm 92 may also be powered by the truck 10, through
its power take off and gear 94, and is preferably
hydraulically powered. The sweeping arm 92 sweeps
paper to be shredded around the tub 78 towards the
outlet 24. Paper is thus fed into the outlet 24 in the
direction along the lower confining surface 84.
Referring in particular to Figs. 4 and 5,
the paper shredder 14 includes a rotating hammer mill
96 mounted on a shaft 98 just below the lower
confining surface 84 of the tub 78. The hammer mill 96
includes plural parallel circular plates 102 mounted
on the shaft 98. At 90 intervals around the periphery
of the plates 102, pins 104 are connected between
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adjacent plates 102. A pair of hammers 106 are
pivotally mounted on each pin 104. Each hammer 106 is
free to pivot on its pin 104. Due to rotation of the
hammer mill, the hammers 106 tend to be oriented
essentially radially during operation. Impact surfaces
108 on bars 112 are provided alony one side of the
outlet 24. The lower confining surface 84 of the tub
78 slopes gently down at an angle of about 15-17
towards the opening in the tub in which the hammer
mill sits thus forming a beach. The impact surfaces
108 protrude up from the beach. Paper to be shredded
is fed across the lower confining surface 84, and
ramps up across the impact surfaces 108 to the impact
position where the hammers 106 first pass the impact
surfaces 108. The direction of movement of the hammers
106 at the point of impact, hence also the direction
of the force exerted by the hammers at impact is shown
by the arrow B. The direction that the shredded paper
is desired to move is shown by the arrow A. The angle
a between A and B is the striking angle. Angle a
should be less than 30, and as close to zero as
possible. The direction of feed of the paper to be
shredded is shown by arrow C. The angle between the
direction of feed and the radial direction of the
hammer is a.
The hammer mill is rotated on shaft 98 by a
motor (not shown), which may for example be the truck
motor, with appropriate linkages, for example pulleys
100 and 101 (the belts on the pulleys 100, 101 are not
shown), between the truck power take off and the shaft
98. Power for the moving parts is conveniently taken
off the truck power take off, but other ways of
supplying power may be used as would be clear to a
person skilled in the art. The sweeping arm 88 must be
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mounted high enough to clear the hammers 106. The
sweeping arm rotates slowly below about ~ rpm.
It is preferred that the hammer mill rotate
at about 2000 rpm. If the rotation of the hammer mill
drops below a certain rate, for example 1800 rpm, it
is likely this is due to jamming of paper against the
hammer mill, and it is preferred that the sweeping arm
88 rotation be dropped substantially (perhaps to zero
rpm) in order to allow the jam to clear. Therefore, it
is desirable that a governor 103 be supplied that is
attached to the shaft 98, as for example by pulley 105
on the shaft 98 and pulley 107 on the governor 103
connected by a belt (not shown). The governor 103
contains a switch to close and open a hydraulic line
109 powering the gear 94 to turn the sweeping arm 88
off when the rpm of the hammer mill drops below a
given amount, say 1800 rpm, and thus regulate the rate
of feed of paper into the paper shredder. The actual
trigger speed for the governor 103 depends on such
factors as the kind of paper being shredded and the
size, speed and sharpness of the paper shredder.
Shredded paper falls between the impact bars
112 into space 114 below the hammer mill, and then by
gravity into bin 116 which forms part of the unloader
16. A mesh screen 120 is provided in the space 114
below the hammer mill. The size of mesh in the mesh
screen 120 can be selected according to the size of
paper particle it is desired to have exit the paper
shredder. Referring to Fig. 1 and also in particular
to Figs. 6A-6D, the bin is formed by a base 118, first
sidewall 122 and second sidewall 124 spaced from each
other and separated by the base 118, a reciprocating
end wall 126 disposed between the first sidewall 122
and second sidewall 124, and an upwardly extending
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discharge chute 128 opposed to the reciprocating end
wall 126. A gear 132 connected to the truck power take
off for example through a chain, sprocket and flywheel
linkage (not shown) is operatively connected to the
reciprocating end wall 126 such that reciprocation of
the end wall 126 compacts shredded paper within the
bin and forces it out of the discharge chute 128. The
end wall 126 is mounted on wheels 134 that run in
tracks 136 that extend along each of the sidewalls
122. Shaft 138 connects the reciprocating end wall 126
with motor 132. The end wall 126 is given structural
rigidity by top plate 142 and strut 142 providing
reinforcement between them.
The bin with reciprocating end wall forms a
compactor for compacting shredded paper received from
the shredder 14. The compactor forms part of the
unloader 16. Compacted shredded paper is pushed by the
compactor up and into a shredded paper storage area
148 formed in the rear of the truck 10 and bounded by
wall 154, 156 and side walls 160 (one shown in Fig.
2E) of the cargo compartment 36 of truck 10. Referring
now to Figs. 7A and 7B there is shown a device for
unloading paper from truck 10. The discharge chute 128
lies protruding through an opening 152 in wall 154
formed of panels 154A-154E during paper shredding,
such that shredded paper discharges into the volume
148 between the wall 154 and wall 156 at end 18 of the
truck. Wall 154 is mounted on angle irons 158, whose
lower edges slide in slots 162 formed between an upper
one of staggered plates 164 and the floor 166 of the
storage area 148. The wall 154 is moved across the
storage area 148 by a ratchet mechanism. Drive I-bar
168 slides in slots 172 formed between the floor 166
and the upper one of staggered plates 174. The I-bar
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168 is notched with notches having a steep side and a
shallow side. In alternating notches 176, 178, the
steep side is reversed in direction from the previous
notch. Pawl 182 is suspended on a pivot from a lower
portion of wall 154. Enough room is left between the
point of suspension of the pawl 182 and the wall 154
to allow the pawl 182 to be flipped over from one side
or the other. The pawl 182 drops down into one or
another of the notches 176, 178. Depending on which
notch 176, 178 the pawl 182 falls into, the wall may
be moved towards or away from the unloading wall 156.
The unloading wall 156 is openable in conventional
fashion and forms an unloading gate.
To avoid clogging the apparatus with
particles of paper, a vacuum 182 is mounted on the
floor 166 of the truck and powered by a motor 184
underneath the floor of the truck. The vacuum is
preferably located adjacent the shredder out of the
storage area 148.
The manner of operation of the mobile paper
shredder will now be described. The method begins with
the step of feeding paper into the mobile paper
shredder, followed by shredding the paper to produce
shredded paper. Paper is preferably fed to the paper
shredder through tub 78. Paper feeding is preferably
accomplished by loading paper into the tub 78 by
lifting the paper in paper container 38 on a lifting
arm 26 to a point above the tub, and rotating the
paper container 38 to discharge the paper into the tub
26. After paper is shredded by action of the hammers
passing between the impact surfaces, the next step is
preferably compacting the shredded paper to produce
compacted shredded paper; followed by periodically
moving the compacted shredded paper towards and out of
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the unloading gate 156. The rotating arm 88 of the tub
moves paper in the direction of feed within the tub 78
towards the opening in the lower confining surface 84
of the tub 78. The rotating hammers 106 of the hammer
mill plunge down between the impact surfaces 108,
shredding the paper and forcing it down and depositing
it into the bin 116. Within the bin 116, the paper is
compacted by the plunger 126 and forced out of the
discharge chute 128 into the storage area 148 behind
the wall 154. Once the storage area 148 is filled, the
compacted shredded paper can be unloaded by moving the
wall 154 towards the unloading gate 156 at the rear 18
of the truck.
A person skilled in the art could make
immaterial modifications to the invention described
and claimed in this patent without departing from the
essence of the invention.
