Abstrict An apparatus for grading crayfish is provided, comprising a tank
having a bottom and sides forming a cavity which will hold water;
and a grate assembly having multiple, vertically separated tiers
to form spaces between adjacent tiers of sufficient size to accommodate
a pre-determined amount of crayfish of pre-determined size. Each
tier comprises multiple, horizontally separated round bars, the
spacing between the bars in each succeeding lower tier being less
than the spacing in the upper tiers. A process for grading crayfish
of multiple sizes is also provided, comprising the steps of loading
crayfish onto a top tier of a grate assembly of the type described
above positioned in a water-filled tank, lifting the grate assembly
from the tank after a period sufficient in time to allow all crayfish
to seek the lowest level tier achievable in accordance with their
size, and removing all crayfish located between one set of adjacent
tiers separately from crayfish located between any other set of
adjacent tiers.
Claims I claim:
1. A process for grading crayfish of multiple sizes, comprising
the steps of:
(a) loading said crayfish onto a top tier of a grate assembly positioned
in a water-filled tank, said grate assembly comprising multiple,
vertically separated tiers forming spaces between adjacent tiers
of sufficient size to accommodate a pre-determined amount of crayfish
of pre-determined size, wherein each tier comprises multiple, horizontally
separated bars, the spacing between said bars in each succeeding
lower tier being less than the spacing in the upper tiers;
(b) lifting said grate assembly from said tank after a period sufficient
in time to allow all crayfish to seek the lowest level tier achievable
in accordance with the size of said crayfish; and
(c) removing all crayfish located between one set of adjacent tiers
separately from crayfish located between any other set of adjacent
tiers.
2. An apparatus for grading crayfish, comprising:
(a) a tank having a bottom and sides forming a cavity which will
hold water;
(b) a grate assembly having multiple, vertically separated tiers
to form spaces between adjacent said tiers of sufficient size to
accommodate a pre-determined amount of crayfish of pre-determined
size, wherein each tier comprises multiple, horizontally separated
bars, the spacing between said bars in each succeeding lower tier
being less than the spacing in the upper tiers; and
(c) wherein said grate assembly comprises:
(i) a frame;
(ii) a first tier attached to said frame wherein the spacing between
said bars is no greater than 0.938 inches and no smaller than 0.913
inches;
(iii) a second tier attached to said frame directly beneath said
first tier wherein the spacing between said bars is no greater than
0.912 inches and no smaller than 0.812 inches;
(iv) a third tier attached to said frame directly beneath said
second tier wherein the spacing between said bars is no greater
than 0.811 inches and no smaller than 0.688 inches; and
(v) a fourth tier attached to said frame directly beneath said
third tier wherein the spacing between said bars is no greater than
0.375 inches and yet large enough to allow the passage of water
during placement into and removal from said tank of said grate assembly.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to devices for grading live crawfish
according to their size.
2. Prior Art
As with the marketing of any commodity, farmers, producers and
distributors are required to comply with certain industry standards
relating to quality regarding size, shape, weight, freshness or
other such characteristics of the goods. Adherence to these standards
is necessary in order to accurately determine the price as well
as other conditions of marketing. In the case of produce, various
devices have been employed to grade fruits and vegetables, and most
have met with great acceptance in that industry. In the marketing
of crayfish, however, little has been done to provide an effective
grading method, perhaps due to the difficulty in handling these
live creatures. Attempts at grading crustaceans have ranged from
manual inspection by unskilled laborers to modification of existing
produce graders.
One of the methods currently in use involves vibrating a table
having spaced-apart horizontal bars wherein the distance between
adjacent prongs becomes continuously greater as the crayfish travel
horizontally away from the loading area. Another method uses a pair
of rotating cylinders spaced apart wherein the distance between
the cylinders becomes continuously greater as the crayfish travel
away from the loading area. Still another technique for grading
crayfish utilizes a single tier of horizontally spaced bars which
can be shaken to facilitate the crayfish passing between adjacent
bars. The problem with these techniques, however, is that each one
fails to yield the consistency and ease of use that are the goals
of an effective grading system.
At the present time in Louisiana, there are at least four grades
of crayfish based on weight. The first grade (so-called "export"
size) are the largest and typically range from 7-14 crayfish per
pound. The second grade (so-called "live" size), being
slightly smaller, ranges from 15-22 crayfish per pound. The third
grade (so-called "processing" size) ranges from 23-30
crayfish per pound, and the fourth grade (so-called "culls")
is anything over 30 crayfish per pound. Based on statistical data
available to the inventor regarding the growth of crayfish, these
grades based on weight are accurately translatable into grades based
on size, i.e. physical dimensions, by measurement of the thoracic
cavity of the crayfish.
The present invention, therefore, accomplishes a dependable method
of grading crayfish using a multiple-tiered grate assembly whose
bar spacing is a function of the size of the crayfish thoracic cavity.
This invention also helps to alleviate problems seen in the related
art by using this grate assembly within a water environment. By
simulating their habitat, this novel technique allows the crayfish
to seek the lowest possible level on their own within the confines
of a static structure, thus resulting in "self-grading"
without the need for vibrating trays or rotating parts. Such a design
not only speeds up the grading process, but minimizes damage to
the crayfish.
SUMMARY OF THE INVENTION
Therefore, it is an object of this invention to provide an apparatus
for grading crayfish which allows the natural instincts and locomotion
of the crayfish to produce the grading effect.
It is another object of this invention to provide an apparatus
for grading crayfish which is quick and simple to use by having
no moving parts and requiring no intervention by an operator during
the grading period.
It is still another object of this invention to provide an apparatus
for grading crayfish which will minimize damage to the crayfish
during the grading process.
These and other objects and advantages of the present invention
will no doubt become apparent to those skilled in the art after
having read the following description of the preferred embodiments
and which are contained in and illustrated by the various drawing
figures.
Accordingly, an apparatus for grading crayfish is provided, comprising
a tank having a bottom and sides forming a cavity which will hold
water; and a grate assembly having multiple, vertically separated
tiers to form spaces between adjacent tiers of sufficient size to
accommodate a pre-determined amount of crayfish of pre-determined
size. Each tier comprises multiple, horizontally separated round
bars, the spacing between the bars in each succeeding lower tier
being less than the spacing in the upper tiers.
A process for grading crayfish of multiple sizes is also provided,
comprising the steps of loading crayfish onto a top tier of a grate
assembly of the type described above positioned in a water-filled
tank, lifting the grate assembly from the tank after a period sufficient
in time to allow all crayfish to seek the lowest level tier achievable
in accordance with their size, and removing all crayfish located
between one set of adjacent tiers separately from crayfish located
between any other set of adjacent tiers.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view of a preferred embodiment of the crayfish grading
apparatus in an assembled configuration.
FIG. 2 is a view of the tank, depicting the drain and transparent
portions.
FIG. 3 is a view of the grate assembly, depicting the multiple
tiers and horizontally spaced bars in each tier.
FIG. 4 is a close-up view of the bars as they are attached to a
preferred embodiment of the grate assembly.
FIG. 5 is a view of a crayfish showing the thoracic cavity.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
Shown in FIG. 1 is a three-dimensional view of a preferred embodiment
of the crayfish grading apparatus 1 in an assembled configuration.
The major components of the apparatus 1 are tank and grate assembly
8. FIG. 2 reveals that tank 2 includes sides 10 and bottom 16 formed
together to create tank cavity 3 which is capable of holding water.
Drain 7 is formed in bottom 16 in order to empty water from tank
2 for cleaning. Drain pipe 27 is attached to the underside of drain
7 and extends horizontally under bottom 16 until it forms a 90 degree
bend and continues up side 10 at a height level with the top of
tank 2. Tank 2 is supported by I-beams 31 or any other suitable
structure which allows the unobstructed use of drain pipe 27. Although
not required for proper operation of the present invention, each
of two sides 10 has a window 4 covered by a transparent sheet 5
which is made of a durable material such as clear plastic or some
other material sold under the tradename Plexiglass. The sheet 5
is attached to side 10 by screws 6 or any other equivalent fastener,
and when assembled should form a water-tight seal 17. Seal 17 can
be simply a continuous line of silicone or possibly a rubberized
strip between side 10 and sheet 5.
Grate assembly 8 is depicted in FIG. 3 and includes frame 9 first,
second, third and fourth tube assemblies 11 12 13 14 and handles
15. Frame 9 is constructed of two vertical, parallel walls 18 which
are rigidly joined on each opposing end by first set 20 and second
set 21 respectively, of vertically-spaced horizontal support members
19. The number of support members 19 in each set 20 21 is equal
to the number of tube assemblies 11 12 13 14. In a preferred
embodiment, first set 20 is composed of channel stock where one
length-wise edge is directed vertically upward and the other edge
directed toward the interior of frame 9. Second set 21 is also composed
of channel stock, but positioned so that one edge is directed toward
the interior of frame 9 and the other edge directed vertically downward.
Furthermore, the outside horizontal edge of each support member
19 of second set 21 is level with the inside horizontal edge of
its corresponding support member 19 of first set 20. This construction
is used to support first, second, third and fourth tube assemblies
11 12 13 14 in such a way as to allow sliding of tube assemblies
11 12 13 14 in and out of frame 9 as well as to facilitate the
removal of crayfish 29 from each level.
First tube assembly 11 is used to collect those crayfish 29 qualifying
as "export" grade (Grade 1) as explained above. As shown
in FIG. 4 the construction of first tube assembly 11 includes aluminum
tubing sections 24 having holes 26 formed through the diameter of
each tubing section 24 near each end. Threaded rod 23 is placed
through holes 26 and lock nuts 25 are placed on each side of each
tubing section 24 in order to fix the position of each tubing section
24 with respect to the other tubing sections 24. The exact number
of tubing sections 24 in first tube assembly 11 is unimportant,
but it is essential that there be enough to fill the area where
first tube assembly 11 is to rest while in operation. Because of
the need to prevent the crayfish 29 from sitting on top of tubing
sections 24 the inventor has determined that the preferred outer
diameter size for tubing sections 24 is to be no greater than 3/4".
Likewise, tubing sections 24 should have an outer diameter of at
least 3/8" to prevent the crayfish 29 from attaching to them
by using their pinchers. Based on the dimensions of the thoracic
cavity 30 of crayfish 29 the maximum spacing between the outer
diameters of any two tubing sections 24 to retain Grade 1 crayfish
29 should be 15/16" (0.938"). To allow passage of Grade
2 crayfish 29 through first tube assembly 11 the minimum spacing
should be at least 0.913". Second and third tube assemblies
12 13 are constructed in exactly the same way, except that the
maximum spacing between tubing sections 24 in second tube assembly
12 is 0.912" and the minimum spacing is 0.812". The maximum
and minimum spacings for third tube assembly 13 are 0.811"
and 0.688", respectively. Fourth tube assembly 14 is similarly
constructed, except that tubing sections 24 have only 1/2"
outer diameters and are welded to rod 23 in such a way as to allow
a spacing of 3/8" or less, but with still enough spacing to
allow water to pass through with ease.
In operation, tank 2 is filled with water, while tube assemblies
11 12 13 14 are placed into grate assembly 8 with first tube
assembly 11 being in the uppermost position and with second, third
and fourth tube assemblies 12 13 14 being placed in order below
first tube assembly 11. Grate assembly 8 is lowered into tank cavity
3 until it rests on tank bottom 16. Crayfish 29 of various sizes
are then dumped into tank cavity 3 and allowed time to seek their
lowest possible level. Once the crayfish 29 are settled, grate assembly
8 is slowly lifted from tank cavity 3 to expose first tube assembly
11 and the Grade 1 crayfish 29 are removed by pushing them off the
unobstructed end of first tube assembly 11. The Grades 2-4 crayfish
29 are similarly procured by further lifting grate assembly 8 and
removing them in the same manner described above. Once all crayfish
29 have been removed, grate assembly 8 is lowered back into tank
cavity 3 and the apparatus 1 is ready for another load of crayfish
29 to be graded. If cleaning is necessary, drain pipe 27 is removed
from drain 7 in tank 2 so that the water is drained from tank 2.
Other embodiments of the apparatus and method of the invention
will occur to those skilled in the art, and are intended to be included
within the scope and spirit of the following claims. |