Method and Device for Zeroing a Scale

Abstract

A method and a scale for the performance thereof performs a zeroing process as soon as a product conveyed across a weighing platform leaves the weighing platform.

Claims

1-15. (canceled)

16. A method for automatic zeroing of a scale, the scale comprising a weighing platform supported by a load cell, the method including: (a) receiving a series of discrete products on the weighing platform and discharging the series of discrete products from the weighing platform, the series of discrete products being conveyed in a conveying direction to and from weighing platform; (b) performing a series of weighing cycles with the scale, each weighing cycle for weighing a set of one or more of the series of discrete products; (c) for each respective one of the series of weighing cycles, where a final one of the series of discrete products received on the weighing platform for that respective weighing cycle has been discharged from the weighing platform and the weighing platform is not loaded by a subsequent one of the discrete products in the series of discrete products after the final one of the series of discrete products for that respective weighing cycle, automatically triggering a zeroing function for the scale at an end of that respective weighing cycle; and (d) automatically canceling the triggered zeroing function where the subsequent one of the discrete products reaches the weighing platform before the triggered zeroing function has successfully concluded.

17. The method of claim 16 wherein two immediately successive discrete products in the series of discrete products form a gap therebetween and the zeroing function is triggered as soon as a front end of the gap has passed the weighing platform in the conveying direction.

18. The method of claim 16 wherein each discrete product has a leading edge in the conveying direction and a trailing edge in the conveying direction, and the method further comprises: (a) conveying a first product in the conveying direction, the first product comprising one of the series of discrete products; (b) determining a point in time at which the leading edge or the trailing edge of the first product reaches a target position downstream of the weighing platform in the conveying direction; and (c) triggering the zeroing function based on the point in time.

19. The method of claim 18 wherein: (a) the point in time is determined by means of a sensor positioned upstream of the weighing platform in the conveying direction, positioned downstream of the weighing platform in the conveying direction, or positioned at an intermediate location along a length of the weighing platform in the conveying direction; and (b) the sensor detects at least one of the leading edge of the first product and the trailing edge of the first product for use in determining the point in time.

20. The method of claim 19 wherein the point in time is determined taking into account at least one of the product length of the first product, a conveying speed of the first product, the length of the weighing platform in the conveying direction, and the length of a gap between the first product and a second product that is adjacent to the first product upstream in the conveying direction.

21. The method of claim 19 wherein the sensor is positioned upstream of the weighing platform in the conveying direction and detects the trailing edge of the first product for use in determining the point in time.

22. The method of claim 16 wherein a sensor is positioned upstream of the weighing platform in the conveying direction and further including terminating the triggered zeroing function in response to a detection of a leading edge of the subsequent one of the series of discrete products.

23. The method of claim 16 wherein a sensor is positioned upstream of the weighing platform in the conveying direction and the zeroing function is triggered if the sensor detects a leading edge of a respective one of the series of discrete products and if no previous zeroing function is running at that point in time.

24. The method of claim 16 wherein the triggered zeroing function is activated as a mode in case a zero-tracking function running up to that time can no longer operate.

25. The method of claim 16 wherein a zero-tracking function is performed through a device included in the load cell of the scale and the triggered zeroing function is performed through a control unit formed separately from the load cell.

26. An automatic scale comprising: (a) a weighing platform operable for receiving a series of discrete products at an upstream side and for discharging the series of discrete products from a downstream side, the series of discrete products being conveyed in a conveying direction, each discrete product in the series of discrete products having a leading edge in the conveying direction and a trailing edge in the conveying direction; (b) a load cell supporting the weighing platform, the load cell and weighing platform being operable to perform a series of weighing cycles, each weighing cycle for weighing a set of one or more of the series of discrete products; and (c) a control unit operable for (i) for each respective one of the series of weighing cycles, where a final one of the series of discrete products received at the weighing platform for that respective weighing cycle has left the weighing platform and the weighing platform is not loaded by a subsequent one of the discrete products in the series of discrete products after the final one of the series of discrete products, automatically triggering a zeroing function for the scale at an end of that respective weighing cycle, and for (ii) automatically canceling the triggered zeroing function where the subsequent one of the discrete products reaches the weighing platform before the triggered zeroing function has successfully concluded.

27. The automatic scale of claim 26 further including at least one sensor for detecting at least one of the leading edge and the trailing edge of one of the series of discrete products conveyed in the conveying direction at a position of the sensor or at a target position spaced apart from the position of the sensor in the conveying direction.

28. The automatic scale of claim 27 wherein the target position is downstream of the weighing platform in the conveying direction.

29. The automatic scale of claim 28 wherein the control unit is operable to determine a point in time at which the leading edge or the trailing edge of one of the series of discrete products reaches the target position and triggering the zeroing function is based on the point in time.

30. The automatic scale of claim 27 wherein the control unit is operable to determine a point in time at which the leading edge or the trailing edge of one of the series of discrete products reaches the target position.

31. The automatic scale of claim 26 wherein the control unit is operable to at least one of (i) receive and process signals from at least one sensor, and (ii) control a conveying device associated with the weighing platform, and (iii) perform the zeroing function.

32. The automatic scale of claim 26 wherein the control unit is formed separately from the load cell.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0043] The FIGURE comprises a schematic side view of a scale embodying principles of the present invention.

DESCRIPTION OF REPRESENTATIVE EMBODIMENTS

[0044] The FIGURE shows a schematic side view of a scale W according to the invention, which is incorporated in the production of individual products P.sub.1, P.sub.2. To determine the weight of the products P.sub.1 and P.sub.2, they are fed one by one to the scale at an upstream end in a conveying direction X (from left to right in the FIGURE) and discharged after the weighing process at a downstream end. The conveying devices necessary for the scale W upstream and downstream are only suggested in the FIGURE and not identified in further detail.

[0045] The scale W includes a weighing platform M which is supported on a load cell D. The weighing platform M is configured as a belt conveyor and can be driven via a motor F. With the aid of the weighing platform M, the individual products such as product P.sub.2 can be conveyed across the weighing platform M in order for its weight to be detected by means of the load cell D in the process.

[0046] The products to be weighed have a leading edge A at the front end thereof viewed in the conveying direction, and a trailing edge B at the rear end. The product length L therefore corresponds to the distance between leading edge A and trailing edge B as viewed in conveying direction X. Downstream of the weighing platform M, a sensor S.sub.2 is arranged at a target position x.sub.T in order to detect the trailing edge B (in this illustrated example) of the product P.sub.1 conveyed downstream from the platform M. The sensor S.sub.2 is preferably a light barrier. A control unit C is provided for detecting the signals transmitted by the sensor S.sub.2. The control unit C is also connected to the load cell D and the motor F as well as to an encoder, not shown, and additionally controls the output of a weight value on a display E as well as zeroing functions. Alternatively, the sensor can be connected directly to the load cell D and the zeroing function can run directly in the load cell, particularly an intelligent or digital load cell having a suitable processing device.

[0047] A method according to the invention may run as follows:

[0048] A product P.sub.1 conveyed by the weighing platform leaves the weighing platform M after completion of the weighing cycle performed by scale W for that product. The trailing edge B thereof thus reaches the target position x.sub.T, which is detected by the sensor S.sub.2 and signaled to the control unit C. Because the weighing platform M is not loaded at this time (a sufficiently large distance between successive products P.sub.1, P.sub.2 is initially assumed in this case), the control unit C can trigger a zeroing function in order to set the display value associated with a non-loaded weighing platform M to “zero.” The zeroing function is preferably terminated before the subsequent product P.sub.2 reaches the weighing platform M. This subsequent product P.sub.2 can then be weighed. A further zeroing function can be started whenever the trailing edge B of the subsequent product P.sub.2 reaches the target position x.sub.T downstream of the weighing platform M.

[0049] Methods according to the invention permit the use of the time available between two successive products (“gap”) for a zeroing function immediately starting from the point in time at which the front product has left the weighing platform or an edge (A or B) thereof has reached a target position x.sub.T, which represents this state (that is, the state at which the front product has left the weighing platform). The zeroing function can then begin immediately (if necessary, an additional time buffer can be provided in order to wait for and ensure the settling of the weighing platform M or of the load cell D in the non-loaded state).

[0050] In order to determine the arrival of a product (more precisely: the arrival of the leading edge A or the trailing edge B thereof) at the target position, it is not necessary to arrange a sensor provided for this purpose at the target position x.sub.T. For this purpose, it is instead possible to evaluate a sensor S.sub.1 provided upstream of the weighing platform, or a sensor S.sub.e arranged alongside the weighing platform M, which sensor is connected to the control unit. Even with such a sensor, the time T at which the trailing edge B of the product will have left the weighing platform M can be determined in order to start the zeroing function. For example, a sensor S.sub.1 arranged upstream of the weighing platform at a sensor position x can be provided to detect the leading edge A of a product P, for example. Starting from this moment, the time required for the trailing edge B of the product to have left the weighing platform results from the distance between the sensor position x and the target position x.sub.T, the conveying speed, the product length L and optionally a conveying pause in case the product is to be weighed at a reduced speed or while immobile.

[0051] At the same time or alternatively, the sensor S.sub.1 could also be used to cancel and disregard a still-running zeroing function or zero-tracking function if a subsequent product has prematurely reached the weighing platform or the sensor S.sub.1. Specifically, it is conceivable and even probable that the distance between two successive products frequently will not suffice to be able to carry out a zeroing function therebetween. If the arrival of a subsequent product P.sub.2 at the sensor position x upstream of the weighing platform M is not detected by this sensor S.sub.1 upstream of the weighing platform M while a zeroing function triggered by a preceding product P.sub.1 is still running, the process can be canceled. In this case, the subsequent product P.sub.2 is weighed, without a zeroing function having been successfully carried out for the previous product. The invention is thus based on the deliberate acceptance of a high cancellation rate in return for securely “capturing” every sufficiently long gap.

[0052] As used herein, whether in the above description or the following claims, the terms “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” and the like are to be understood to be open-ended, that is, to mean including but not limited to. Also, it should be understood that the terms “about,” “substantially,” and like terms used herein when referring to a dimension or characteristic of a component indicate that the described dimension/characteristic is not a strict boundary or parameter and does not exclude variations therefrom that are functionally similar. At a minimum, such references that include a numerical parameter would include variations that, using mathematical and industrial principles accepted in the art (e.g., rounding, measurement or other systematic errors, manufacturing tolerances, etc.), would not vary the least significant digit.

[0053] Any use of ordinal terms such as “first,” “second,” “third,” etc., in the following claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another, or the temporal order in which acts of a method are performed. Rather, unless specifically stated otherwise, such ordinal terms are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term). Rather than using an ordinal term to distinguish between commonly named elements, a particular one of a number of elements may be called out in the following claims as a “respective one” of the elements and thereafter referred to as “that respective one” of the elements.

[0054] The term “each” may be used in the following claims for convenience in describing characteristics or features of multiple elements, and any such use of the term “each” is in the inclusive sense unless specifically stated otherwise. For example, if a claim defines two or more elements as “each” having a characteristic or feature, the use of the term “each” is not intended to exclude from the claim scope a situation having a third one of the elements which does not have the defined characteristic or feature.

[0055] The above-described preferred embodiments are intended to illustrate the principles of the invention, but not to limit the scope of the invention. Various other embodiments and modifications to these preferred embodiments may be made by those skilled in the art without departing from the scope of the present invention. For example, in some instances, one or more features disclosed in connection with one embodiment can be used alone or in combination with one or more features of one or more other embodiments. More generally, the various features described herein may be used in any working combination.

REFERENCE CHARACTERS

[0056] A Leading edge [0057] B Trailing edge [0058] C Control unit [0059] D Load cell [0060] E Display [0061] F Motor [0062] L Product length [0063] M Weighing platform [0064] P.sub.1, P.sub.2 Product [0065] S.sub.1 Sensor [0066] S.sub.2 Sensor [0067] S.sub.e Sensor alongside the weighing platform [0068] T Point in time [0069] W Scale [0070] X Conveying direction [0071] x Sensor position [0072] x.sub.T Target position