Cutting – By endless band or chain knife – With means to guard the tension
Reexamination Certificate
1999-07-06
2004-01-20
Choi, Stephen (Department: 3724)
Cutting
By endless band or chain knife
With means to guard the tension
C083S814000
Reexamination Certificate
active
06679149
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to tensioning mechanisms and more particularly to a tensioner assembly installable in a food product band saw apparatus for tensioning of a band saw blade.
BACKGROUND OF THE INVENTION
In the food processing industry large upright band saws such as band saw
10
of
FIG. 1
are commonly used for cutting meat products of a variety of sizes. Such band saws typically include a frame
12
upon which is mounted a support surface
14
for positioning meat products to be cut. A housing portion
16
extends above support surface
14
and a housing portion
18
extends below support surface
14
. A band saw blade
20
passes though a plane defined by support surface
14
and extends around wheel members (not shown) located with housing portions
16
and
18
for being drivingly rotated by such wheel members. In particular, a drive motor
22
may be connected for rotating a drive wheel in housing portion
18
.
In the food processing industry the band saw, including the blade, has to be cleaned each day and each time the food product being cut is changed. Therefore, such band saws preferably include a system which allows easy removal of the saw blade and simple reinstallation and retensioning the saw blade. Further, food product band saws preferably run as quiet as possible since they may operate in supermarket settings. As the noise produced by the band saw can vary according to the tension of the saw blade, it is desirable to enable a user to establish the appropriate saw blade tension in a simple manner. A properly configured tensioner and tensioning system may achieve the above goals.
A tension of the band saw blade may be adjusted by adjusting the position of a drive mount which supports the drive motor
22
and accordingly the drive wheel in housing portion
18
. Referring to
FIG. 2
, and exemplary drive mount
24
is illustrated and is pivotably connectable to a frame
26
of the band saw by pivot pin
28
. The drive motor
22
is connected to the drive mount and a drive shaft extends to the lower drive wheel
30
for rotation and support thereof. Thus, the lower drive wheel
30
is also supported by the drive mount
24
. A tensioner
32
may be connected between the drive mount
24
at connection point
34
and the frame at a connection point
36
, enabling adjustment of the pivotable position of the drive mount
24
and thus the position of the lower drive wheel
30
and/or the tension force of a saw blade
20
extending thereabout.
Tensioner
32
represents a known prior art tensioner which is illustrated schematically in FIG.
3
and includes a mounting bushing
38
with a shaft
40
extending therethrough. A mounting nut
42
is threaded onto the shaft
40
and a spring
44
extends from the mounting bushing
38
to the mounting nut
42
. A handle
46
enables rotation of the shaft
40
. In operation the mounting bushing
38
is connected to connection point
36
of the frame and the mounting nut
42
is connected to connection point
34
of the drive mount
24
. Spring
44
provides a shock and vibration absorbing feature for the lower drive wheel
30
and associated drive motor
22
. Tension on the blade (represented schematically at
48
) is increased by rotating handle
46
to increase the distance between the mounting bushing
38
and the mounting nut
42
. The spring
44
is pre-compressed to assure the blade
48
is properly tensioned when the mounting nut
42
is positioned at the far end of the threaded shaft
40
. The pre-compressed force on spring
44
is typically very large since the blade
48
needs a large tension force. To maintain the condition where the handle
46
abuts against the mounting bushing
38
at all times, the spring
44
must be compressed at all times. Unfortunately the compressive force of the spring
44
is largest when the blade
48
is placed in the slack, non-tensioned condition resulting in high spring forces which must be overcome in order to remove the blade
48
.
In order to remove a saw blade from a band saw the lower drive wheel
30
must be raised by rotating handle
46
to decrease the distance between the mounting bushing
38
and the mounting nut
42
. With the above tensioner
32
arrangement in order to decrease the distance between the mounting bushing
38
and the mounting nut
42
the compression force of the spring
44
must be overcome. Further, the downward weight of the drive motor
22
and lower drive wheel must also be overcome. Accordingly, rotation of the handle
46
can be difficult.
Accordingly, in one embodiment, the present invention is directed to an improved tensioner assembly.
SUMMARY OF THE INVENTION
A tensioner assembly includes a mounting bushing having an opening therethrough and a shaft having at least one threaded region along its axial length, the shaft extending through the opening. A mounting nut is threaded onto the shaft. A seating surface extends from the shaft at a position intermediate the mounting bushing and the mounting nut. A spring is disposed around the shaft between the mounting bushing and the seating surface. A first end of the spring is positioned against the seating surface so as to be fixed at the intermediate position along the shaft regardless of a distance between the mounting bushing and the mounting nut, a second end of the spring is positioned toward the mounting bushing.
In another embodiment a method of tensioning a blade of a band saw apparatus including a frame, a drive mount including a first portion pivotably connected to the frame, a rotatable wheel supported by the drive mount and movable therewith, the blade extending about said rotatable wheel, involves: (a) providing a tension bolt assembly including a mounting bushing having an opening therethrough, a shaft extending through the opening and having at least one threaded region along its axial length, a mounting nut threaded onto the threaded region of the shaft and spaced from the mounting bushing, a spring disposed around the shaft and positioned between the mounting bushing and the mounting nut, a first end of the spring positioned against a seating surface located intermediate the mounting bushing and the mounting nut such that said first end of said spring is spaced from the mounting nut, a second end of the spring positioned against a first side of the mounting bushing; (b) connecting the mounting bushing to the frame; (c) connecting the mounting nut to a second portion of the drive mount; and (d) rotating the shaft until the shaft moves through the mounting bushing opening and the spring is compressed, such that a tension force of the blade is balanced with a compression force of the spring.
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patent: 3194284 (1965-07-01), Walker
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patent: 4576077 (1986-03-01), Titus
patent: 4803804 (1989-02-01), Bryant
patent: 5030173 (1991-07-01), Bryant
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McGriff Lynn Alan
Yan Gongpu
Choi Stephen
Premark FEG L.L.C.
Thompson Hine LLP
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