Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION: DRIVE SYSTEM FOR FOOD
SLICING MACHINE
BACKGROUND OF THE INVENTION
Field Of The Invention
The invention relates to drive systems, and
more particularly to drive systems for food slicing
machines in which a food product retaining carriage
is reciprocatingly driven.
Description Of The Related Art
In conventional food slicing machines, a
workpiece-retaining carriage is reciprocatingly
driven for the purpose of reciprocating a food
product workpiece, such as a cheese log, through a
cutter. The workpiece is cut, forming a slice that
falls downwardly due to gravity onto a conveyor, a
tray or another food product, such as a slice of
bread or pizza crust. After the slice is formed,
the workpiece is driven back across the cutter,
dropping downwardly so that another slice can be
formed. The operation of the slicing machine is
cyclical, with a cutting stroke during the first
half of the cycle and the return stroke in the
second half of the cycle.
The workpiece-retaining carriage is linked to
a drive mechanism. Conventional drive mechanisms
are hydraulic rams, and cranks connected to rotary
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motors, both of which are described in U.S. Patent
No. 4,436,012. Both of these drive mechanisms mount
to the workpiece-retaining carriage near where the
food product is retained. This configuration has
the disadvantage that drive system parts and
lubricants must be made of food grade materials, and
must be washable by the means used to wash the
carriage.
The displacement of the carriage by the rotary
motor and crank mechanism approximates sinusoidal
motion. This sinusoidal motion has large variations
in the speed of the workpiece during the formation
of slices. These large variations result in
inaccuracies in the formed slices.
Additionally, the width of the motor and crank
mechanism is greater than the width of the carriage.
This configuration makes placing multiple carriages
in a close, side-by-side relationship unfeasible.
Therefore, the need exists for a carriage drive
system that can be adjusted to control the accuracy
of formed slices. The drive system should also be
mounted in a position that keeps moving parts away
from the region of the food product workpiece to
avoid the necessity of expensive materials and
frequent washing. Furthermore, the drive system
should be narrow enough that several carriages can
be mounted in close proximity without interference
between moving parts.
SUMMARY OF THE INVENTION
The invention is an improved drive system for
a food product slicing machine. The slicing machine
with which the drive system cooperates has a frame,
and a workpiece-retaining carriage attached to the
frame. The carriage retains a food product
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workpiece therein, and reciprocates the workpiece
through a path including a cutter.
The drive system includes a drive member
pivotably mounted to the machine frame about a
pivot, such as a pivot pin. A support panel mounts
to the drive member, and has a curved surface spaced
from the axis . This space is substantially equal to
a radius of curvature of the curved surface. The
curved surface has first and second sides.
First and second idle pulleys are connected to
the machine frame, with the second idle pulley
spaced from the first, forming a gap. A drive pulley
is drivingly linked to a rotatably driven shaft of
a prime mover, preferably through a gear mechanism.
An elongated, flexible drive means, preferably a
belt, loops around the drive and idle pulleys. The
first end of the drive belt extends from attachment
to the drive member, near the first side of the
support panel's curved surface. The belt extends
through the gap between the first and second idle
pulleys, around the drive pulley, and through the
gap. The second end attaches to the drive member
near the second side of the support panel's curved
surface .
When the prime mover's shaft rotates in one
direction, the drive belt is driven in the same
direction, applying a force to one side of the
support panel and drive member. The drive member is
displaced in one direction, pivoting about the pivot
axis and swinging the workpiece-retaining carriage
through an arcuate path. Upon reaching its extreme,
the prime mover stops the drive shaft's rotation and
reverses its direction, thereby swinging the
workpiece-retaining carriage through the arcuate
path in the opposite direction.
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By continuously reversing the prime-mover's
direction of rotation, the workpiece-retaining
carriage is reciprocated through the arcuate path,
thereby reciprocating a food product workpiece
retained within the carriage through a cutting
blade, forming slices. The prime mover provides a
much more consistent velocity during cutting, which
results in consistent slice thickness and spacing of
multiple slices. Furthermore, because of the
configuration of the drive system, several
workpiece-retaining carriages can be mounted in a
small space.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a side view illustrating the present
invention.
Fig. 2 is a view in perspective illustrating a
portion of the present invention, and its mounting
position on the slicing machine.
Fig. 3 is a side view in section illustrating
the preferred tensioning pulleys and adjustment
mechanisms.
Fig. 4 is a side view illustrating the present
invention.
Fig. 5 is a top view illustrating the present
invention.
In describing the preferred embodiment of the
invention which is illustrated in the drawings,
specific terminology will be resorted to for the
sake of clarity. However, it is not intended that
the invention be limited to the specific~terms so
selected and it is to be understood that each
specific term includes all technical equivalents
which operate in a similar manner to accomplish a
similar purpose. For example, the word connected or
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terms similar thereto are often used. They are not
limited to direct connection but include connection
through other elements where such connection is
recognized as being equivalent by those skilled in
5 the art.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment is shown in Figs. 1
and 2, in which a workpiece-retaining carriage,
preferably the cluster box 12, is rotatably mounted
to the frame 10 of the food product slicing machine
14. The frame 10 encompasses many, but not all,
regions of the machine 14, and includes any of the
structural components that make up the base,
backbone or housing of the machine 14 (shown in Fig.
2). The machine 14 includes the frame 10, and all
other parts connected to the frame 10.
The cluster box 12 is, in its operable
position, inserted into one of the chambers formed
between the panels 8, which are part of the frame
10. The cluster box 12 is rigidly mounted to the
pivot shafts 16, and the pivot bushings 17 are
mounted between the pivot shafts 16 and the panels
8. The cluster box 12 is driven in a pendulum
motion about the pivot shafts 16, and the food
workpiece, which could be one food log or several
food logs as shown in Fig. 5, is retained in the
cluster box 12, protruding from the lower end where
slices are formed in the food slicing area 6 shown
in Fig 4.
The drive member 20 is rigidly mounted to the
cluster box 12 at the pivot shafts 16, permitting
simultaneous oscillating rotation of the drive
member 20 and the attached cluster box 12 about the
axis of the pivot shafts 16. The drive member 20 is
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driven upwardly and downwardly in reciprocating
motion about the pivot shafts 16 as described below,
and this motion drives the cluster box 12 in its
slicing reciprocation.
The support panel 22 is rigidly mounted to the
end of the drive member that is preferably farthest
from the pivot shafts 16. The curved surface 24 of
the support panel 22 faces away from the pivot
shafts 16, and has a radius of curvature, R,
substantially equal to the distance between the
curved surface 24 and the axis of the pivot shafts
16. The radius, R, is preferably between about 12
and 18 inches, but could be larger or smaller.
Generally, a larger radius, R, permits greater
precision in moving the cluster box 12.
A prime mover, preferably, but not necessarily,
the servomotor and gear box 3 0 , is mounted to the
frame l0 at a point spaced from the pivot shaft 16.
The drive pulley 32 is connected to the gear box,
which attaches to the drive shaft of the servomotor,
preferably by directly mounting thereto, but
alternatively connecting through any conventional
linkage. The drive pulley 32 preferably has teeth
formed in its outer, circumferential surface for
inserting between, and engaging, the corresponding
teeth on the inner surface of the drive belt 34,
which is preferably a toothed timing belt. The
preferred drive belt 34 could be substituted by any
conventional flexible, or hinged, means, such as a
drive chain or rope, as long as the cooperating
structures accommodate it.
The drive belt 34 extends around the drive
pulley 32 into a gap between first and second idle
pulleys 40 and 42. The idle pulleys 40 and 42 are
rotatably mounted to the frame 10 between the
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support panel 22 and the drive pulley 32. A gap is
formed between the closest parts of the outer
circumferential surfaces of the idle pulleys. The
idle pulleys guide the opposing ends of the drive
belt 34, that extend through the gap in opposite
directions, toward opposite sides of the support
panel 22. The surfaces of the segments of the drive
belt 34 that extend between the idle pulleys and the
support panel 22 seat against the curved surface 24
of the support panel 22.
Tensioning pulleys 44 and 46 are mounted at
opposite sides of the support panel 22 for
grippingly engaging the toothed surfaces of the
opposing ends of the drive belt 34 between the
tensioning pulleys 44 and 46 and the clamps 48 and
50.
From one end to the other, therefore, the drive
belt 34 extends from gripping engagement between the
tensioning pulley 44 and the clamp 48, seating
2o against the upper side of the curved surface 24 of
the support panel 22, and into the gap between the
idle pulleys 40 and 42. The drive belt seats
against the circumferential surface of the idle
pulley 40 and spans the distance to the drive pulley
32, around which the drive belt 34 extends. From
the drive pulley 32, the drive belt extends the
distance back through the gap between the idle
pulleys, seating against the idle pulley 42. The
drive belt extends from the idle pulley 42 to the
curved surface 24 and seats against it, extending
along it to clamping engagement between the
tensioning pulley 46 and the clamp 50. Of course,
the drive belt 34 could be an endless loop that,
instead of attaching at opposite sides of the
support panel 22, attaches at one point at or
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between the tensioning pulleys 44 or 46.
During operation, the servomotor and gear box
30 apply a rotary force to the drive pulley 32 in
one direction. A tensile force is thus applied to
one end of the drive belt 34 by the drive pulley.
This tensile force is applied through the drive belt
to one of the tensioning pulleys gripping the belt
at one side, for example the tensioning pulley 44 on
the top side, of the belt support panel 22. The
tensile force applied to the end of the belt support
panel rotates the drive member 20 around the pivot
shafts 16, rotating the attached cluster box 12 in
one half of the cutting cycle, which is to the left
in the example and as shown in Fig. 1.
Once the cluster box 12 is displaced a
predetermined distance to the left, the servomotor
and gear box 30 rapidly stops rotating the drive
pulley. The drive pulley is then driven in the
opposite direction. The drive pulley 32 applies a
tensile force to the opposite end of the belt,
thereby applying a tensile force to the opposite
side, for example the tensioning pulley 46 on the
lower side, of the belt support panel 22. This
produces an upwardly directed force that displaces
the cluster box 12 in the opposite direction for the
other half of the cutting cycle, which is to the
right in the example and as shown in Fig. 1.
The length of the stroke the cluster box 12 is
driven through is controlled by the servomotor. The
degree of rotation of the servomotor's drive shaft
determines the distance the drive member 20 is
displaced, and therefore the distance the cluster
box 12 is displaced. A center sensor, which is not
shown, detects the center point of the stroke, and
signals a central computer of the presence of the
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cluster box 12 at the center point. This sensor is
used to calibrate the system, so that the
servomotor's driveshaft position is noted at the
moment the computer is signalled that the cluster
box is centered. Then the distance the drive member
20 must be driven from center can be determined
mathematically by the computer based upon the
geometric dimensions (such as the radius, R, the
gear box ratio, etc.) of the drive system. The
distance the cluster box 12 is driven is then
controlled by the computer controlling the degree of
rotation of the servomotor's driveshaft.
Sensors at opposite extremes of the center
signal the computer if the cluster box 12 has
exceeded the normal path, or if, to avoid damage,
the cluster box 12 must be stopped from further
motion in the present direction. It is preferred
that the stroke of the present invention be variable
from four to 12 inches.
The drive belt 34, once adjusted in tension by
rotating the tensioning pulleys 44 and 46, does not
loosen or tighten during the operating cycle. This
is due to the relationship between the curvature of
the curved surface 24 of the support panel 22 and
the motion of the drive member 20. Because the
radius of curvature, R, of the curved surface 24 is
substantially equal to the distance from the curved
surface 24 to the axis of the pivot shafts 16, and
because the drive belt between the idle pulleys 40
and 42 and the curved surface stays seated against
the curved surface 24, the drive belt 34 maintains
the same tension during the movement of the drive
member 20 from one extreme to the other.
The outer circumferential surfaces of the idle
pulleys 40 and 42 that are closest to the curved
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surface 24 are spaced slightly from the curved
surface 24 to permit the drive belt 34 to pass
through the spaces. The close proximity of the idle
pulley surfaces and the curved surface 24 prevents
5 slackening of the drive belt 34 during operation,
which would occur if the spaces were significantly
greater than the thickness of the drive belt 34.
The tensioning pulleys 44 and 46 have tension
adjustment screws 60 and 62, respectively, as shown
10 in Fig. 3. Once the opposite ends of the drive belt
are positioned between the tensioning pulleys 44 and
46 and the clamps 48 and 50, the screws 60 and 62
can be adjusted to change the tension on the drive
belt 34. The ends of the screws 60 and 62 contact
curved inner cam surfaces on the tensioning pulleys,
which causes slight rotation of the tensioning
pulleys upon rotation of the screws 60 and 62. Of
course, other adjustment mechanisms are contemplated
as being equivalent to the preferred structure.
One advantage of the drive system of the
present invention is the ability to create a
trapezoidal velocity curve with the servomotor.
Conventional drive systems, such as a crank and
motor, approximate sinusoidal motion, which does not
provide slices that are as accurately patterned as
with the trapezoidal velocity curve. This is
because variations in workpiece velocity are minimal
or nonexistent except at the extremes of the cycle,
whereas with a sinusoidal motion variations are
significant throughout.
The advantage of a trapezoidal velocity curve
is most apparent when slicing a group of food logs,
such as those shown in Fig. 5. Because the velocity
of the cluster box is essentially constant during
cutting, the food slices that fall from the cluster
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box fall onto a substrate, such as a pizza crust, in
an even slice pattern. Without the constant
velocity, the spacing would be uneven, resulting in
an uneven slice pattern. Sinusoidal motion of the
prior art machines produces a slice pattern with
closely spaced slices formed initially, greater
spacing between the middle slices, and close spacing
nearer the end of the slice. Such spacing is more
noticeable the longer the stroke. With the present
invention, slice patterns are significantly
improved.
Additionally, the drive system of the present
invention is narrower than conventional drive
mechanisms, and this permits several cluster boxes
to be grouped very closely together.
Furthermore, each drive system can be housed in
the drive system region 2 shown in Fig. 2, which is
separated from the food slicing area 6, shown in
Fig. 4. This separation allows the drive system
parts to be made of any material, and eliminates the
need to clean the drive system in the same manner as
food-contacting parts of the slicing machine.
While certain preferred embodiments of the
present invention have been disclosed in detail, it
is to be understood that various modifications may
be adopted without departing from the spirit of the
invention or scope of the following claims.
