Abstract:
A device and method for weighing eggs. The egg weighing apparatus includes a movable stem that supports an egg weighing platform. The stem is attached to a measuring device that is electronically and mechanically driven for precise measurement of an egg. The present invention uses a damper or alternatively, uses a tuned dynamic vibration absorber to yield precise measurement of an egg.

Description:
CROSS REFERENCE TO CO-PENDING APPLICATIONS  
       [0001]    This Utility Application claims priority from the filing date of Jan. 20, 2003, of U.S. Provisional Application S.No. 60/441,389, the contents of which are incorporated herein in its entirety. 
     
    
     
       BACKGROUND  
         [0002]    The present invention relates to an egg weighing apparatus.  
           [0003]    The handling of shell eggs for marketing has matured into a volume production business. Chicken farms housing hundreds of thousands and even millions of egg laying chickens utilize high speed collection systems which collect the eggs laid by the chickens, washes, candles, checks the egg shells for cracks, grades the eggs generally by weight, sorts the eggs into groups according to the grade or weight and then packages the eggs for shipping.  
           [0004]    While the grade contains several different categories, such as jumbo, large, medium, small and others, each grade is generally defined by a very small range of weights which may be set by government regulations or customer demand.  
           [0005]    The extremely large number and the high speed of the egg handling equipment necessitates that the weighing of each egg take place quickly, typically in less than one second.  
           [0006]    Generally, a high speed egg handling apparatus will utilize a weighing station which contains multiple scales which are capable of weighing each egg passing over the scale and generating an output signal to a computer which stores the weight with a particular egg identification to track the egg through the handling and sorting process.  
           [0007]    Known egg weighing apparatus or scales utilize damping means to reduce the oscillations caused in the scale as each egg drops into the weighing platform or perch. Damping is usually accomplished by shearing a viscous fluid. However, optimal damping can be difficult to maintain over extended time and temperatures. Further, all of the damping fluid must be contained from loss.  
           [0008]    In addition, the egg handling facility requires frequent washing to maintain a high level of sanitary conditions. The application of high pressure cleaning solutions or water may be used in most portions of the egg handling equipment, such as the conveyers, sorters, etc. However, the precision weighing apparatus have not heretofore been capable of being cleaned through high pressure fluid application due to the design of the scales themselves. This has necessitated gentle hand washing which slows the cleaning operation.  
           [0009]    Thus, it would be desirable to provide an egg weighing apparatus for high speed egg handling equipment which addresses the deficiencies of previously devised egg weighing apparatus.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention provides an apparatus for weighing an egg. The apparatus includes a housing, sensor means for weighing an egg, a tower mounted on the housing for supporting and surrounding the sensor means and a stem movably displaced through one open end of the tower and supporting an egg weighing platform.  
           [0011]    The egg weighing apparatus includes a force transmission member formed of a solid body with two legs, one leg carrying bores for receiving fasteners for attaching the transmission member to a transducer, and an angularly disposed second leg attaching the transmission member to the stem.  
           [0012]    One aspect of the invention encompasses usage of a tuned dynamic vibration absorber, wherein a mass element is attached to the force transmission member to diminish vibratory oscillation of a perch attached to the upper end of the stem, the oscillation is diminished by minimizing movement of the stem.  
           [0013]    One end of the stem is attached to the force transmission member and the other end of the stem is attached to the egg weighing platform.  
           [0014]    In one aspect of the invention, a water resistant sealing cap is releasably mounted on the outer surface of the stem between the tower and the egg weighing platform. The water resistant sealing cap includes a bore and the cap has a first end and a second end. The bore has a complimentary shape to the exterior shape of a collar in the tower and forms a labyrinth path through the second end of the cap.  
           [0015]    The present invention also defines a method for weighing an egg comprising the steps of placing an egg in a weighing platform, displacing a stem connected to the weighing platform in proportion to the weight of the egg wherein such displacement generates distortion of a force transmission member coupled to the stem in a measurable strain. Then supplying the measured strain to a control means in the form of a signal proportional to the displacement of the stem.  
           [0016]    The present invention provides a high speed egg weighing apparatus that provides the user option of using a damper or not using a damper to provide precision egg weighing. An alternative aspect of the invention that is employed when damping is not used is inclusion of a tuned dynamic vibration absorber. The tuned dynamic vibration absorber is employed to diminish vibratory oscillations, the oscillations can not exceed the pre-determined mechanical limits of the transducer. The transducer is one alternative that can be chosen for the sensing means of the present invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0017]    The various features, advantages and other uses of the present invention will become more apparent by referring to the following detailed description and drawings in which:  
         [0018]    [0018]FIG. 1 is a longitudinal, cross sectional view of an egg weighing apparatus according to one aspect of the present invention;  
         [0019]    [0019]FIG. 2 is an enlarged, cross sectional view of a portion of the apparatus shown in FIG. 1;  
         [0020]    [0020]FIG. 3 is a cross sectional view of an egg weighing apparatus according to another aspect of the present invention;  
         [0021]    [0021]FIG. 4 is a graph depicting the output of an egg weighing apparatus starting from the application of an egg to the weighing platform;  
         [0022]    [0022]FIG. 5 is a perspective view of an egg weighing apparatus depicting a tuned dynamic vibration absorber formed by attaching a mass to a force transmission member; and  
         [0023]    [0023]FIG. 6 is a cross sectional view of an egg weighing apparatus according to another aspect of the present invention.  
         [0024]    [0024]FIG. 7 is a flowchart depicting an optional signal processing aspect of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0025]    Referring now to FIGS. 1 and 2, there is depicted an egg weighing apparatus  20  constructed according to one aspect of the present invention.  
         [0026]    The apparatus  20  includes a base or housing  22  on which a tower  24  is mounted for supporting and surrounding a sensor means or transducer  26 . A stem  28  is movably disposed through one open end of the tower  24  and supports a weighing platform or perch  30  at an upper end. The perch  30  is designed to receive an egg shown in phantom by reference number  32  during a weighing operation or cycle, with the egg  32  being transported to and from the perch  30  by means of transporting or conveying equipment, not shown.  
         [0027]    The housing  22  surrounds a control means  22 A, shown in phantom in FIG. 6, which forms the basis for the weighing operation of each egg  32 . The control means  22 A may comprise a suitable control means  22 A, such as a central processing unit operating a control program stored in memory as well as associated electronic circuits, analog/digital converters, signal conditioning circuits, etc. One or more connectors  34 ,  36  and  38  may be provided on the housing  22  to provide connection to external circuits, for supplying electric power to the control means  22 A, as well as to output a signal or signals containing the weight of each egg  32 .  
         [0028]    Although the sensor means  26  may be one of a number of different types of precision sensors, by example only, the sensor means  26  is a transducer which has one or more strain gauges mounted on thin, flexible webs  40  and  42 . The webs  40  and  42  are supported in a block  44  which is secured by suitable fasteners, such as by screws  46 , to the base or housing  22  and by fasteners, such as screws  48 , to a force transmission means or member  50 .  
         [0029]    In this aspect of the invention, the force transmission member  50  is formed of a solid body, having a generally L-shape, with one leg  52  carrying bores for receiving the fasteners  48  therethrough, and an angularly disposed second leg  54  which has a bore  56  for receiving a fastener, such as a screw, not shown, to attach the transmission member  50  to one end of the stem  28  as shown in FIG. 5. Attached on the top edge of the force transmission member  50  adjacent to the stem  28  is a mass element  41 . The attachment of the mass element  41  serves the function of diminishing vibratory oscillation of the perch  30  by minimizing movement of the stem  28 . The mass element  41  can be formed from a number of different types of material such as stainless steel, aluminum, tin, etc. The mass element  41  can be attached to the force transmission member  50  via a foam adhesive  43 , for example, that behaves as a spring and provides damping. The combination of a mass element  41  and foam adhesive  43  results in the generation of a tuned vibration dynamic absorber.  
         [0030]    An alternate tuned dynamic absorber can be formed by suspending a mass element  41  between springs  81  and  83  within a closed chamber  41 A containing a viscous fluid as shown in FIG. 6. The chamber  41 A is sealed with an o&#39;ring or other suitable sealing means. Such an arrangement protects against chemical exposure and lasts for an infinite duration of time.  
         [0031]    The stem  28  is a solid body formed of metal or high strength plastic and having a generally tubular configuration extending between one end  58  joined to the leg  54  of the force transmission member  50  and an opposed second end  60  joined by a fastener, not shown, to the perch  30 .  
         [0032]    The stem  28  has an intermediate shoulder  62  as well as a threaded end portion  64  for attaching the perch  30  extending from the upper end  60  of the stem  28 .  
         [0033]    In operation, an egg  32  deposited on the perch  30  will cause a displacement of the stem  28  in proportion to the weight of the egg  32 . This displacement will generate distortion of the leg  54  of the force transmission member  50  relative to the opposed leg  52  which will generate a measurable strain in the strain gauges mounted on the webs  40  and  42 . The strain gauges which may be two strain gauges on each web  40  and  42 , are connected in a Wheatstone bridge circuit, the output of which is supplied to the control means  22 A in the base  22  in the form of a signal proportional to the displacement of the stem  28  which is proportional to the weight of the egg  32 .  
         [0034]    The stem  28  should move freely through the open end  70  of an end collar  72  of the tower  24  so as to have a displacement precisely proportional to the weight of the egg  32  in the perch  30 . This requires a small clearance or gap between the outer surface of the stem  28  and the inner surface  74  of the bore extending through the sleeve  72  of the tower  24 . This gap must be closed to the external environment to prevent the entry of water or fluid typically employed during a cleaning operation.  
         [0035]    To provide a seal, and at the same time, a seal which is resistant to the application of high pressure cleansing fluids, the present invention uniquely utilizes a sealing cap  80  which is releasably mounted on the stem  28 . As shown in greater detail in FIG. 2, the collar  72  of the tower  24  is formed with at least one and preferably two or more annularly extending, axially spaced ribs or flanges  82  and  84 . The sealing cap  80  is formed of a suitable water resistant, easily formed material. Although metals, such a stainless steel may be employed, in one example of the present cap  80 , the cap  80  is formed of a polymeric material, such as Delrin.  
         [0036]    The sealing cap  80  is formed of a generally tubular shape having a first end  86 , an opposed second end  88 , and a sidewall  90  extending between the first and second ends  86  and  88 . A portion of the sidewall  90  adjacent the first end  86  may be tapered or formed as a conical surface  92  for weight reduction. An annular recess  94  is formed in the first end  86  adjacent to a bore  96  extending through the first end  86  of the cap  80 .  
         [0037]    The small diameter bore  96  extending through the first end  86  transitions into a larger bore denoted by reference number  100 . The bore  100  is formed with a configuration generally complementary to the exterior shape of the collar  72  of the tower  24  to form a labyrinth or serpentine path from an enlarged diameter aperture or opening  102  at the second end of the cap  100  to a closed inner end  104  at an opposite end of the bore  100 .  
         [0038]    The cap  100  is formed with axially spaced, alternating smaller and larger diameter cavities  106 ,  108 ,  110 ,  112 , and  114  extending axially from the first opening  102  to the opposed end  104  of the bore  100 . The smaller diameter cavities  108  and  112 , which may be as few as one and preferably two or more, by example only, are formed by annular flanges  116  and  118  which extend radially inward from the sidewall  90  of the cap  100 .  
         [0039]    As shown in FIG. 2, the larger diameter and larger volume cavities  106  and  110  are concentric with the annular flanges  82  and  84 , respectively, on the collar  72  of the tower  24 . The smaller diameter and smaller volume cavities  108  and  110  are disposed adjacent to and axially spaced from the flanges  82  and  84 . In conjunction with the radially inward extending end flange  120  which forms the aperture  102  in the second end  88  of the cap  100 , as can be clearly seen in FIG. 2, the bore  100  defines a labyrinth or serpentine shaped path from the aperture  102  to the opposed closed end  104  which is disposed adjacent to the upper end of the gap between the outer surface of the stem  28  and the inner surface  72  of the collar  72  of the tower  24 . This labyrinthian path blocks the entry of cleaning fluids, such as water, through the aperture  102  for any significant axial distance along the length of the bore  100  thereby preventing the entry of such cleaning solutions through the opening in the end  70  of the collar  72  into the gap between the stem  28  and the collar  72 .  
         [0040]    In this manner, the sealing cap  80  of the present invention uniquely enables the egg weighing apparatus  20  to accurately weigh eggs and, at the same time, to be rapidly and efficiently cleaned using cleaning solution applied with a high pressure.  
         [0041]    The sealing cap  80  is fixedly mounted on the stem  28  by means of a fastener, such as an internally threaded nut  126  which is threaded over external threads  128  formed on the end portion of the stem  28 . A metal or plastic washer  130  may be employed with the nut  126 . A sealing member, such an O-ring  132 , is mounted in the recess  94  to seal the connection between the stem  28  and the cap  80 . In this manner, the cap  80  is unitarily mounted on the stem  28  and moves with deflection of the stem  28  when an egg  32  is introduced into the perch  30 .  
         [0042]    Turning now to FIG. 3, there is depicted a modification to the egg weighing apparatus  20 . This aspect of the apparatus  20  includes dampening of deflection or movement of the stem  28  when an egg  32  is deposited on one end. In this aspect, a force transmitting member  150 , having a generally U-shape formed of a first end leg  152  fixed by means of a threaded fastener  154  to one end of the stem  28 , extends angularly from an intermediate leg  156 . An opposed second leg  158  extends angularly from the intermediate leg  156 . A shaft  160  extends from one end of the second leg  158  into a recess or well  161  formed in the upper end of the base  22 . The shaft  160  slidably extends through a larger diameter shaft  162  formed as part of the tower  24 . The shaft  160  is spaced by a small gap from the inner surface of the bore in the shaft  162 .  
         [0043]    A disk  164  is carried on one end of the shaft  160  and is positioned in the bottom of the recess or well  161 . The well  161  will be filled with a suitable damping material, such as silicone, which fills the well  161  to a height below the end  166  of the shaft  162  to prevent the entry of the silicone or other fluid into the gap between the shaft  160  and the shaft  162 .  
         [0044]    The weight of an egg  32  deposited on one end of the stem  28  will cause deflection of the stem  28 , the force transmitting member  150  and the disk  164 . Oscillation of the shaft  160  caused by such deflection will be dampened by dampening material surrounding the disc  164  which has a much larger surface area than the cross section of the shaft  160 .  
         [0045]    One feature of this construction is that no separate, mechanical sealing means is required to maintain the damping fluid within the recess  160 . The damping fluid flows like water such that any tilting of the base  22  from its normal mounting position shown in the orientation shown in FIG. 3 will immediately cause the damping fluid to flow to one side or the other of the well  161  away from the end  166  of the shaft  162 . This prevents entry of the damping fluid into the gap between the shaft  162  and the shaft  160 .  
         [0046]    Even if the entire weighing apparatus  20  was inverted, such as prior to mounting in a fixed position in an egg handling system, the damping fluid would quickly flow to one or both sides of the shaft  162  before it could enter the opening at the end  166  of the shaft  162 .  
         [0047]    Thus, the use of the well or recess  160  eliminates the need of a seal which could cause seal friction and result in measurement error.  
         [0048]    [0048]FIG. 6 illustrates the aspect of the apparatus  20  that includes dampening movement of the stem  28  when an egg  32  is deposited on one end. In this aspect, the mass element  41  is located upon a bottom spring  83  that is attached to the force transmission member  50  and the mass element  41 . At the top of the mass element  41  is another spring  81  that is attached to the mass element  41  and the stem  28 . The cavity  41 A may contain fluid used to damp the motion of the mass element  41  with respect to the stem  28  motion. Together, the mass element  41 , the springs  81  and  83  and the fluid in the cavity  41 A form a tuned dynamic vibration absorber that serves the function of diminishing vibratory oscillation of the egg scale perch  30  by minimizing movement of the stem  28 .  
         [0049]    Referring now to FIG. 4, there is illustrated a pictorial representation of the displacement of the stem  28  from the instant an egg  32  is deposited on the perch  30 . As can be clearly seen in FIG. 4, the displacement of the stem  28  exhibits oscillations due to the momentum of the egg as it contacts the perch  30  as well as further movement of the egg  32  on the perch  30  due to the typical non-roundness of an egg.  
         [0050]    As shown in FIG. 4, an offset of  0 . 004  inches is preset into the apparatus  20 . The stem  28  will settle at this displacement without any weight being applied to the perch  30  at one end of the stem  28 .  
         [0051]    When an egg  32  is deposited on the perch  30 , the displacement of the stem  28  rapidly increases to a first peak magnitude  200 , then transitions to a first valley magnitude  202  before returning to a second peak magnitude  204 , less than the first peak magnitude  200 , and continuing as the oscillations asymptotically or exponentially die off with decreasing magnitude.  
         [0052]    The typical prior art egg weighing apparatus would normally wait until the oscillations reach a minimal value before executing a weighting operation. However, this is time consuming.  
         [0053]    According to this aspect of the present invention, signal processing in lieu of complete mechanical damping is employed. The magnitude of the first peak  200  and the magnitude of the first valley  202  are first measured and then averaged. A continuing average is then made with the second peak magnitude  204  and the following second valley  206  to further refine the cumulative average. These averages of each peak and valley pair, such as peak and valley pair  200  and  202  and peak or valley pair  204  and  206 , can be integrated over a predetermined measurement time period to create an average value for the stem displacement which is proportional to the weight of the egg  32  on the perch  30  on one end of the stem  28 . This displacement can be correlated through a lookup table or other means to a known weight of the egg  32 . Thus, the stem  28  displacement measured by the transducer  26  can generate an output signal used to precisely measure the weight of the egg  32  in only a few oscillations thereby significantly reducing the time for making an accurate measurement of the weight of an egg  32  to further increase production efficiency.  
         [0054]    The above described averaging technique can be implemented digitally, as described above, or in a combined analog and digital manner. In an analog calculation, the instant that an egg  32  is deposited on the stem  28  a settle time which can last for a predetermined time, such as  50  to  60  milliseconds, is timed. At the conclusion of the settle time, the stem displacement is measured by an analog filter which has the effect of creating a continuing average between alternating peaks and valleys in the oscillating displacement signal. This analog output can be integrated over time by digital processing circuitry or in a central processing unit to generate a digital average signal which is proportional to the weight of the egg  32 .