Accurate, high speed weighing apparatus and method

• US 6,963,036 B1
• Filed: 11/01/2002
• Issued: 11/08/2005
• Est. Priority Date: 11/01/2002
• Status: Expired due to Fees

• Current Assignee: Heinz Zicher
• Original Assignee: Heinz Zicher
• Inventors: Zicher, Heinz
• Primary Examiner(s): Gibson, Randy W.
• Application Number:
  US10/286,067
• Time in Patent Office: 1,103 Days
• Field of Search: 177/185, 177/199, 177/200, 177/210.FP
• US Class Current: 177/185
• CPC Class Codes: G01G 11/04 having electrical weight-sensitive devices
• CPC Class Codes: G01G 23/10 by electric or magnetic means

Abstract

The static or dynamic weighing apparatus for weighing an object or item, comprising a weighing assembly that includes a base with four (4) load cells attached to it, two (2) active load cells and two (2) passive load cells. Each active load cell has a mounting side and a weighing side. They are mounted to the base and to each other via a rigid weighing platform and are rotated 180° with respect to each other in the horizontal plane, thereby generating respective inverse error signals when an object or item is placed on or passes over the weighing platform. The two (2) passive load cells are mounted in the same manner. A combination of the voltage outputs from each of the respective two (2) load cells pairs negates all horizontally and vertically induced errors thus yielding a highly accurate two (2) times normal weight signal of the object or item being weighed. Error voltages felt by the passive assembly, representing any present vertical vibration, is removed via electrical circuitry from the actual active weighing voltage output, resulting in a true weight of the object or item being weighed. The resulting output voltage over the designated time interval then represents the true weight of the object or item being weighed. A voltage-to-frequency converter is employed to transmit the corrected true frequency output due to the actual analog output voltage resulting from the active weight being measured to a binary counter over a pre-specified time period. By counting a pulse train that varies directly to the applied voltage over a specified period of time results in a natural averaging weight and the resulting count is the average and true count of the representative weight of the object or item being weighed.

Claims

1. In a static or dynamic weighing apparatus for weighing an object or item statically or moving in a linear path comprising:

a weighing assembly including a base, two identical first and second active load cells rigidly mounted on the base, and

a weighing platform rigidly mounted on both of the load cells,

the improvement residing in said second active load cell being spaced from said first active load cell and having a 180°

orientation relative to the first active load cell, and said apparatus further including a first and a second passive load cells spaced from each other and spaced from said first and second active load cells, said first and second passive load cells being mounted on said base, a rigid member rigidly fixed to said first and second passive load cells and said first and second passive load cells being inline with and spaced from said first and second active load cells and having the same orientation as first and second active load cell and and a passive load being fixed to said weighing platform and said load being representative of the weight of an object to be weighed by said first and second active load cells, and circuitry for subtracting the voltage waveform generated by the passive load on said first and second passive load cells from a voltage waveform generated by the weight of an object weighed by said first and second active load cells to obtain a more accurate weight of the object being weighed and for converting the voltage indicative of the weight of the object to an always present frequency train a portion of which is counted over a selected time period to obtain an averaged count indicative of the weight of the object weighed.

4. The weighing apparatus of claim 1, wherein each active load cell and each passive load cell has a mounting side and a weighing side, said active load cells being parallel spaced from each other beneath said weighing platform and arranged 180°

degrees relative to each other thereby to produce inverse error weighing signals in the horizontal Plane when weighing an object.

5. The weighing apparatus of claim 1, wherein each of said active and passive load cells has a load capacity of X gm for weighing items having 15% X gm or less of the load capacity of the load cell to minimize hysteresis, ringing, and deformation.

7. The weighing apparatus of claim 1 wherein said circuitry includes an operational amplifier having an adjustable input whereby the adjustable input can be set to a value to offset the weight of said platforms, and the passive load.

16. The weighing apparatus of claim 1, wherein said circuitry is operable to count a portion of said frequency train over a fixed time period interval thereby to perform an averaging function of the weight of the item being weighed.

2. In a static or dynamic weighing apparatus for weighing an object or item, statically or moving in a linear path, comprising:

a weighing assembly including a base,

four identical load cells rigidly mounted to the base comprising a first active load cell and a second active load cell, a first passive load cell and a second passive load cell,

a first weighing platform rigidly mounted to both said first active load cell and said second active load cell, and a second weighing platform rigidly mounted to both said first passive load cell and said second passive load cell,

each of said four load cells having a mounting side and a weighing side with said mounting side for all four load cells being rigidly fixed to said base,

the improvement residing in said first weighing platform being rigidly fixed to said first active load cell and said second active load cell, and said second weighing platform being rigidly fixed to said first passive load cell and said second passive load cell, respectively, said second active load cell being horizontally rotated 180°

relative to said first active load cell, and said second passive load cell being horizontally rotated 180°

relative to said first passive load cell, respectively, said first and second active load cells being spaced from each other, said first and second passive load cells being spaced from each other by the same separation as established between said first and second active load cells, the centerlines of said active and passive weighing platforms being parallel to each other, both said passive load cells being spaced from said active load cells with said passive weighing platform containing a passive load comparable to that of an object or item to be weighed on the active weighing platform, thereby to generate inverse signals between the first and second active load cells, and between the first and second passive load cells, respectively, in the horizontal plane when an object is placed on or passes over said first weighing platform, and circuitry associated with said active load cells and said passive load cells for adding output signals from both said first and second active load cells and for subtracting a passive output signal from said first and second passive load cells from the added active output signals to obtain a highly accurate voltage signal indicative of an object or item being weighed, thereby also eliminating any normal forces due to vertical vibration since any vertical vibration introduced into said apparatus will be equally transmitted to both said active and passive weighing platforms, and circuitry for converting the voltage indicative of the weight of the object or item to an always present frequency train a portion of which is counted over a selected time period to obtain an averaged count indicative of the weight of the object or item weighed.

6. The weighing apparatus of claim 2, wherein each of said active and passive load cells has a load capacity of X gm for weighing items having 15% X gm or less of the load capacity of the load cell to minimize hysteresis, ringing, and deformation.

3. A method for weighing an object or item, individually or sequentially, statically or moving in a linear path, with two, spaced apart, first and second active load cells, comprising the steps of:

mounting the two active load cells on a base;

rigidly fixing an active weighing platform to both the active load cells;

orienting the second active load cell 180°

horizontally with respect to the first active load cell;

mounting two additional passive load cells to the same base;

orienting the second passive load cell 180°

horizontally with respect to the first passive load cell, the two passive load cells being spaced identically as the two active load cells and spaced from and in-line with respective ones of the two active load cells;

rigidly fixing a passive weighing platform to both passive load cells;

providing a passive load rigidly connected to the passive weighing platform;

providing the passive load cell arrangement with a passive weight attached to same simulating a comparable load to an object or item to be weighed and to negate any externally introduced vibrations subjected onto the weighing apparatus resulting from any horizontal or normal forces presented to the weighing apparatus in the weighing environment;

subtracting a passive voltage signal generated by circuitry associated with the passive load cells from an active voltage signal generated from circuitry associated with the active load cells with differential amplifiers knowing that any externally introduced forces must be equally transmitted to both the active weighing platform and the passive weighing platform;

weighing an object or item;

obtaining a first voltage signal due to the load over the active load cells and converting the resulting voltage signal to an always present frequency train a portion of which is counted over a selected time period to obtain an first average count indicative of the weight of the object or item weighed;

supplying the first averaged count to a computer;

obtaining a second voltage signal without an object or item on or over the active load cells;

converting the resulting voltage signal to an always present frequency train a portion of which is counted over a selected time period to obtain a second averaged count indicative of no weight;

supplying the second averaged count to the computer; and

,

subtracting the second averaged count (tare weight) from the first averaged count (gross weight), to determine the true weight (net weight) of the object or item being weighed.

8. The method of claim 3 including the step of only using 15% or less of the capacity of the active load cells in performing weighings to minimize hysteresis, ringing, and deformation.

9. The method of claim 3 including the step of adding the respective voltages generated by the two active load cells to each other.

10. The method of claim 3 including the step of adding the respective voltages generated by the two passive load cells to each other.

11. The method of claim 3 including the step of subtracting the respective voltages generated by the two passive load cells from the respective voltages generated by the two active load cells to obtain a clean accurate voltage indicative of the weight of the object.

12. The method of claim 11 including the step of converting the resulting voltage to the always present frequency train using a voltage to frequency converter.

13. The method of claim 12 including the step of counting the always present frequency train in an area where the count over a selected time interval is a stable representation of the voltage signal from which the frequency train was generated.

14. The method of claim 13 including the step of only using 15% or less of the capacity of the active load cells in performing weighings to minimize hysteresis, ringing, and deformation.

15. The method of claim 3 including the step of modifying said resultant voltage signal relative to the weight of the active and passive weighing platforms, and the passive load.