Multi-stage weight scale

Abstract

A weight scale having an operational weighing range, comprising an overall response characteristic having at least first, second and third discrete stages over the operational weighing range. The first, second and third stages are defined by first, second and third predetermined response characteristics, respectively. The weight scale further comprises first, second and third scale arrangements or mechanisms which establish the first, second and third response characteristics, respectively, of the three stages.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation-in-part of Application Ser. No. 09/354,740, filed Jul. 29, 1999.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to weighing scales, and is more particularly directed to a device for detecting and indicating changes in a small weight that is embedded within a much larger, i.e., heavier, residual weight.

[0003] It is difficult for the consumer to measure a small variable weight that is contained within a much larger weight, most of which is a relatively constant residual weight. It is also difficult to monitor and obtain an advance warning of the impending exhaustion of a given variable weight, which can be considered a critical weight.

[0004] A weight load can be considered to consist of two or more components, that is, an initial part, a critical part, and an end part. The critical part is typically significantly smaller than either of the other two components, but this is typically the component whose weight is of the most interest. Consequently, any weighing device that detects variations, i.e., gradual depletion, of the critical component should have a more sensitive scale for the critical part than for the other two parts. In many cases, the consumer needs to monitor only the critical part, and the weighing device or scale only needs to read and monitor the critical component, and not the initial or end parts.

[0005] A particular example of this is a cylinder of a consumable gas, such as propane or natural gas. The cylinder has an empty or residual weight which does not vary for that cylinder. Also, when completely filled with propane or natural gas, the cylinder has a full or initial weight, which also is a fixed value for that cylinder. The customer is interested in monitoring the weight of the cylinder so that he or she will be aware when the contents have been nearly consumed, and the cylinder is approaching an empty condition. Where the cylinder contains, for example, ten kilograms of propane, the consumer needs to know when it has emptied down to about the final one or two kilograms, which constitute the “critical weight.” Consequently, the weighing scale needs to monitor only for that range of zero to two kilograms, which lies somewhere between the cylinder's residual weight and the cylinder's full or initial weight. Thus, there is a need for a weighing device that monitors the critical part of the load.

[0006] There are many other applications as well, where the critical part of the load is embedded within the overall weight of the load, between the residual weight and the initial weight.

[0007] There may also be a need to monitor the fill, rather than the depletion of a container's contents, in which case the critical weight would be increasing instead of decreasing. The critical weight range can be close to the initial weight instead of close to the residual weight.

OBJECTS AND SUMMARY OF THE INVENTION

[0008] Accordingly, it is an object of this invention to provide a weighing and monitoring technique that avoid the drawbacks of the prior art.

[0009] It is another object to provide a weighing scale of simple design which accurately monitors the critical part of the weight load.

[0010] It is yet another object to provide a weighing scale that can be adjusted for its range and sensitivity in measuring changes within the critical weight range.

[0011] It is a further object to provide a weighing scale of rugged design and which can provide an audible and/or visible alarm.

[0012] In accordance with an aspect of the present invention, an embedded weight scale indicates variations in weight of an article wherein the variable weight is embedded within a heavier weight, and where the article has a base residual weight and a variable embedded weight. The scale has a base with first and second upstanding walls and a top pan adapted for supporting the article whose weight is to be monitored. There is a linkage, in this case formed of a pair of long levers and a pair of short levers. The long levers each have a first end pivotally supported on the first wall of the base and a second end, the second ends being joined together by a pivot pin or the like. The short levers each have a first end pivotally supported on the second wall of the base, and each has a second end that is pivotally joined to a midpoint of a respective one of the long levers. The top pan is supported at four points, i.e., at a respective position on each of the long levers and the short levers. There is a counterbalance pivot on said base, and this is preferably customer adjustable, i.e., by turning a wheel or screw. A counterbalance weight lever is joined at its first end to the second ends of said long levers, and this lever extends across the base, over the counterbalance pivot, to a second end. A counterbalance weight is supported on the second end of this counterbalance weight lever. The counterbalance weight lever has a range of movement that corresponds to the range of weight that includes the embedded weight, i.e., the critical weight, of the article.

[0013] An adjustable tensioning spring means permits the consumer to adjust the tension between the base and the long levers. Weight indicating means are also provided, including a sensor for sensing variation in the position of the counterbalance weight lever as it moves within its range, i.e., within the critical weight range of the embedded weight.

[0014] The weight indicating means may take the form of a potentiometer having a rotary slider, and a lever connecting the slider with the counterbalance weight lever. A gear multiplier or other means can be employed to increase the sensitivity range of the potentiometer.

[0015] The adjustable tensioning spring means can employ a spring holder plate affixed to said base, a spring tension adjusting screw on the spring holder plate, and a tensioning spring positioned between the spring holder plate and the second ends of the long levers.

[0016] The counterbalance weight may be selectively adjustable in its position on the counterbalance weight lever, so as to adjust the critical weight range. Also, there are stops provided to limit the movement of the counterweight lever, with the positions of the stops being selected to affect the selection of the critical weight range.

[0017] As can be understood, the range of counterbalance movement is governed by the height of the unit, and the positions of the stops, whereas the range of the critical weight is governed by the settings of the counterbalance weight, the counterbalance pivot, and the spring.

[0018] The above and many other objects, features, and advantages of this invention will become apparent to persons skilled in the art from the ensuing description of a preferred embodiment, which is to be read in conjunction with the accompanying Drawing.

BRIEF DESCRIPTION OF THE DRAWING

[0019] FIG. 1A is perspective view of an embedded weight scale monitoring unit and load, in the form of a cylinder of propane or liquefied natural gas, according to an embodiment of this invention.

[0020] FIG. 1B shows the warning unit of this embodiment.

[0021] FIG. 2 is a schematic sectional elevation of the monitoring unit of this embodiment.

[0022] FIG. 3 is a schematic top view of this embodiment.

[0023] FIGS. 4A and 4B are schematic top plan and side views for explaining the operation of this embodiment of this invention.

[0024] FIGS. 5A and 5B are charts for explaining the dependency of counterbalance weight.

[0025] FIGS. 6A and 6B are charts for explaining the dependency of spring and stopper settings.

[0026] FIGS. 7A and 7B are charts for explaining sensitivity in the critical weight range.

[0027] FIG. 8 is a graphical chart for explaining the general principles of the counterbalance weight leverage system employed in this embodiment.

[0028] FIG. 9 is a schematic side view of the counterbalance weight lever for explaining this embodiment.

[0029] FIG. 10 is a top view of the counterbalance weight lever and sensor element of this embodiment.

[0030] FIG. 11 is an overall response characteristic of a Type D embodiment of the present invention, showing three discrete stages.

[0031] FIG. 12A-12D are a series of overall response characteristics for Types A, B, C and D embodiments, respectively, of the present invention.

[0032] FIG. 13 is a simplified schematic diagram of a Type B embodiment of the present invention.

[0033] FIG. 14 is a simplified schematic diagram of a Type C embodiment of the present invention.

[0034] FIG. 15 is a simplified schematic diagram of a Type D embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0035] With reference to the Drawing, an embodiment of the embedded weight measuring weighing scale of this invention is shown in FIGS. 1A and 1B. Here, a weighing scale device 10 has a rectangular or square base 12, and a top or weighing pan 14 supported over the base 12. A load 16 is shown here to take the form of a gas cylinder, with a fill of a compressed consumable gas, such as propane or liquid natural gas. This is only an example, of course, and the load 16 can be any load that has a basic, residual weight, and a larger total weight when filled. In this embodiment the tank or cylinder 16 is shown with a partial remaining fill 18 (shown in ghost lines), with the contents being depleted and approaching exhaustion. In this example, the empty weight of the cylinder or tank may be, for example ten KG, and the contents of the tank, when filled may be a similar weight, that is, another ten KG. The customer is interested in being alerted when the tank is nearing exhaustion, that is, when there are about two KG of gas remaining inside the cylinder 16. This last two KG of gas is considered the critical weight in this example. That is, the cylinder has an initial (filled) weight of twenty KG, a residual (empty) weight of ten KG, and a critical weight range between ten and twelve KG. A wire or cable 20 extends from the weighing or sensing unit 10 to an alarm or customer interface unit 22, which is shown in FIG. 1B. The unit 22 may have an audible alarm to alert the consumer when the critical weight is detected, and may also have visible indicators, here a green lamp 26A which lights to indicate that the weight is above the critical weight range, a yellow lamp 26B to provide a warning when the weight has dropped into the critical range, and a red lamp 26C to provide a warning when the weight has dropped below the critical range, i.e., the propane or natural gas is exhausted. The unit 22 contains batteries and electronic circuitry, which are not shown here.

[0036] The construction of the weighing scale device 10 is illustrated in FIGS. 2 and 3. As shown, there is a linkage mechanism between the base 12 and the top pan 14, in this case formed of a pair of long levers 28 and a pair of short levers 30. The long levers 28 have one end pivoted on a back wall 32 of the base 12, and the short levers 30 have one end pivoted on a front wall 34 of the base, with another end pressing down at the midpoints of the long levers 28, respectively. The top or pan 14 is shown to have four legs 36 that extend down and rest upon locations along the long and short levers 28, 30, respectively. There is a pivot pin 38 through the second or free ends of the two long levers 28.

[0037] A counterbalance weight lever 40 has one end attached to the long levers at the pivot pin 38, and proceeds from there towards the back wall 32 of the base 12. A movable pivot 42 is positioned on the base 12 and the lever 40 rests upon the pivot 42. A pivot adjusting screw 44, which is user actuable, permits the user to adjust the position of the pivot relative to the lever 40. A counterbalance weight 46 is positioned at the rear end of the counterbalance weight lever 40, and may be adjustable in its position along the lever. Shown near the front wall 34 of the base 12 is a stopper 48 (which may be either factory-set or field-adjustable) that limits the downward motion of the second ends of the long levers 28 and the front end of the counterbalance weight lever 40.

[0038] An adjustable spring 50 is positioned at the second ends of the long levers 28, and its tension is user-adjustable by means of a spring tension adjusting screw 52. A spring holder plate 54 holds the spring in position at the front wall 34 of the base, so that there is a spring tension accorded between the base 12 and the counterbalance weight lever 40. Also shown is a sensor element 56, e.g., a potentiometer, which serves as an active detector and is sensitive to upwards or downwards motion of the counterbalance weight lever 40.

[0039] As shown in FIGS. 4A and 4B, the weight of the load 16, which is transmitted via the legs 36 to the long levers 28 and short levers 30, creates an image load or virtual load weight WL at the position of the pivot pin 38, i.e., at the end of the counterbalance weight lever 40. At the other end of the lever 40, the counterbalance weight has a weight WC. The pivot 42 is positioned to define a lever arm l between the pivot and the virtual weight WL, and a counterbalance lever arm L between the counterbalance weight 46 and the pivot 42. The virtual weight WL depends on the actual weight of the load 16, and the virtual weight WL is in balance with the counterbalance weight WC when this relation is satisfied: L×WC=l×WL. When the load 16 is above the critical range, the lever 40 is deflected to a maximum point d determined by the stopper 48. When the load weight drops into the critical range, the virtual weight WL is balanced by the counterbalance weight WC, and the lever 40 moves through a deflection range D, i.e., until the counterbalance weight 46 bottoms out and rests on the base 12. In this range, the lever 40 is free to move up and down, and changes in the virtual weight WL are balanced by increasing or decreasing the tension on the spring 50 under deflection of the lever 40. The sensitivity in this range depends on the spring setting, which the user can adjust by means of the adjusting screw 52. The lengths of the lever arms L and l can be adjusted by moving the pivot 42, and also by moving the counterbalance weight 46. Also, the size of the counterbalance weight 46 can be adjusted, i.e., by adding trim weights.

[0040] The initial weight value for the scale 10 can be set by adjusting the counterbalance weight value, and its position on the lever 40, i.e., from a relatively lower value x0 to a higher value x0′, as shown in FIGS. 5A and 5B. This does not affect the width of the critical range. The other bound of the critical range can be adjusted by adjusting the spring 50 and/or the stopper 48, i.e., from a relatively lower setting x1 (FIG. 6A) to a relatively higher setting x1′ (FIG. 6B). This can widen or narrow the range of interest, i.e., the critical range. The sensitivity to load weight variation within the critical range of deflection can depend on the sensitivity of the potentiometer 56, as well as various mechanical parameters, such as the spring constant (stiffness) of the spring 50.

[0041] FIG. 8 is a chart for explaining the operation of the unit 10, i.e., calibrated to sense the critical weight range 18 of the propane or natural gas cylinder 16 of FIG. 1. Here, the abscissa shows values of load weight values, with X0 corresponding to the residual weight, i.e., the empty weight of the tank or cylinder 16; XRCW corresponds to the critical weight range, i.e., the final two KG 18 of propane or natural gas in the cylinder, with X1 being the upper limit of the critical weight range XRCW. Above this is the residual weight range XRES, which is limited by the maximum rated weight XM for the scale. The expected full weight of the cylinder 16 would be somewhat smaller than this value XM. Deflection of the counterbalance weight lever 40 is depicted on the ordinate. This also corresponds to the scale sensitivity.

[0042] The stopper 48 blocks any deflection of the counterbalance weight lever 40 for weights in the range XRES, and the counterbalance weight 46 is bottomed out in its range for load values at or below the residual value X0. For loads in the critical range XRCW, the action of the spring 50 determines the deflection of the lever 40.

[0043] As shown in FIG. 9, a virtual load bearing point 58 is shown on the counterbalance weight lever 40 to the right of the pivot 42. At the position shown, the scale is at or below the residual weight, and the counterbalance weight 46 is fully descended. The beginning of the critical weight range, i.e., the value X1, is characterized by the right end of the lever 40 being descended into contact with the stopper 48. The weight values where these occur depends on the size of the weight 46 and its position along the lever 40, and also on the position of the pivot 42. These depend to some extent as well on the stiffness of the spring 50, and its tension. Thus, the customer or user can field-adjust the scale 10 to adjust the weight values in which an alarm or warning is received.

[0044] As shown in FIG. 10, the sensor element for this weighing scale can be a potentiometer 56, here of the rotary type, with a rotor stem 60 for moving the rotary wiper of the potentiometer. The rotor stem 60 has attached to it a potentiometer lever arm 62, whose distal end is coupled to a mover element 64 on the lever 40, so that the potentiometer rotor stem 62 follows the up and down motion of the counterbalance weight lever 40. This can be mechanically arranged for optimal sensitivity. In one possible arrangement, a planetary gear multiplier can be used to increase the angular response of the potentiometer 56 to motion of the lever 40. Also, instead of a potentiometer, other devices may be used, such as a magnetic sensor (i.e., Hall device), optical indexer, or other known arrangement. Also, instead of the coil spring 50 shown here, another spring arrangement, e.g., a leaf spring or a torsion spring could be employed. In addition, the spring 50 could include an air bladder or other resilient means within the ambit of the present invention. The spring 50 may be positioned either above or below the lever 40.

[0045] Also, the scale need not have the square or rectangular shape as shown. Also, in some versions, rather than using the stopper 48 to limit the motion of the lever 40, the lever 40 and the counterbalance weight 46 can be limited in their upward direction by the height of the unit.

[0046] Well known systems, such as levers, hydraulics, springs and others, are used to reduce, proportionally, the actual weight of a load into a fraction of that weight. Spring leverage systems and adjustable counterbalance weight systems are the most commonly used, in ordinary consumer scales. It is a common practice in the art to use the leverage principles (or equivalent) in conjunction with either spring or adjustable counterbalance weight principles to obtain a scale weighing action (i.e., “single action”).

[0047] In the preferred embodiment of the weighing scale of the present invention, a leverage system principle in combination with an adjustable counterbalance weight principle is used for one stage of the scale's weighing operation (hereinafter “counterbalance weight arrangement”); a leverage system principle in combination with a tension spring is used for another stage of the scale's weighing operation (hereinafter “leverage spring arrangement”); and another counterbalance weight arrangement is used to provide a third stage of the scale's weighing operation. In the preferred embodiment of the present invention, the two arrangements are incorporated to work together, independently, in three sequences, i.e., in three discrete stages. Thus, the present invention can be considered as three different scales, each one independent of the other, but working in sequence.

[0048] With reference to FIG. 11, an embodiment of the weight scale of the present invention will now be described. In the following description, we start from zero load and end at full load. FIG. 11 shows a three-stage response over the operational range of the scale. In a first stage, the scale will measure a constant or variable weight (for example, an initial load) according to a predetermined units-vs.-weight characteristic or proportionality 102. In a second stage, the scale will measure a constant or variable weight (for example, critical load) according to another predetermined units-vs.-weight characteristic or proportionality 104. In a third stage, the scale will measure a constant or variable weight (for example, end load, maximum load, exhausted load, etc.) according to yet another predetermined units-vs.-weight characteristic or proportionality 106.

[0049] FIG. 11 shows characteristics 102, 104 and 106 as being linear; however, they may be a single value (a point), a constant (flat line), or a non-linear response. In the example shown in FIG. 11, the load is increasing in all three stages. Of course, the scale function is the same in either direction, whether the load is increasing or decreasing. It is apparent from the above description and FIG. 11 that the scale's overall response is defined by three discrete responses or stages.

[0050] The embedded weight scale of the present invention can be configured in different types of embodiments. One embodiment, which we refer to as “Type A,” is suitable for a consumable gas cylinder or tank scale, the application described above with reference to FIGS. 1-10. Other types, which will be referred to as Types B, C and D, will be described hereinbelow. The response characteristics (weight units vs. load weight) of Types A, B, C and D scales are shown in FIGS. 12A-12D, respectively. Again, the responses are from zero to full load.

[0051] In a Type A embodiment, a counterbalance weight arrangement and a leverage spring arrangement are utilized. An example of this embodiment is shown in FIGS. 2 and 9. Lever 40 is initially biased down by counterbalance weight 46 (unbalanced), and needs a force WL at bearing point 58 large enough to induce upwards movement of counter weight 46 (See FIG. 9). The magnitude of WL is dependent on the weight of counterbalance weight 46, its distance from pivot point 42, and the distance of point 58 from pivot 42. These are the controlling factors in determining a first stage R1 of the Type A scale's response (FIG. 12A). As shown in FIG. 12A, the response is zero units over first stage (or weight range) R1. At this stage, spring 50 is still under its predetermined state of tension, and it will remain so until forced to expand. Once lever 40 begins to move upwards (actuated by force WL at point 58), spring 50 will begin to expand. This expansion marks the beginning of a second stage R2 in the Type A embodiment (FIG. 12A). The second stage continues until lever 40 hits stopper 48, at which point a third stage R3 in the scale's response begins (FIG. 12A). Third stage R3 has a flat constant unit response, which may have an upper weight limit where the load at point 58 could damage or destroy the scale (i.e., maximum mechanical limit).

[0052] With further reference to FIG. 12A, first stage R1 could be made smaller or larger (i.e., varying WL), according to the specific application, by altering one or more of the controlling factors mentioned above. Second stage R2 can be altered by altering the specifications of spring 50 and pre-tensioning spring 50 using adjustment screw 52 (FIG. 2). Second stage R2 is limited by the distance lever 40 can travel without exceeding the expansion limitation of spring 50. Stopper 48 is used to limit the lever travel distance in this embodiment. Thus, in the second stage of a Type A scale, a critical weight (or embedded weight), defined for a gas cylinder, can be measured at a higher sensitivity (units-vs-weight proportionality) than the other variable weights (weight ranges) associated with the gas cylinder. (In this example, the scale has a nil response as to these other variable weights). From this example, it is seen that three stages of weighing a load is obtained and controlled independently.

[0053] In a Type B embodiment, an adjustable counterbalance weight arrangement and a leverage spring arrangement are utilized. As shown in FIG. 12B, the scale of this embodiment also has a three-stage response—two linear responses (during a first and a second stage R1 and R2) and one nil response (during a third stage R3). A simplified schematic diagram of a Type B scale is shown in FIG. 13. FIG. 13 represents a scale identical to that shown in FIG. 2, except that lever 40 and counterbalance weight 46 have been replaced with a lever 140 and an adjustable counterbalance weight 146. Lever 140 is initially maintained in equilibrium over a pivot 142, and counter weight 146 is allowed to slide across lever 140 automatically (by means well known in the art) to maintain the equilibrium (balance) of lever 140. This action defines the first stage (R1) of this embodiment (FIG. 12B).

[0054] Referring again to FIG. 13, when a load or force WL is applied at a virtual load bearing point 158, lever 140 is forced off balance, causing the system to re-adjust (or balance itself). Counterbalance weight 146 slides to a new position until balance is re-established. The sliding action of weight 146 will continue as load WL increases, but ultimately weight 146 will reach a limit and stop, as shown in broken lines in FIG. 13. At this point, the first stage (R1) of the scale's response ends and the second stage (R2) begins (FIG. 12B). A spring 150, like spring 50, comes into play during the second stage (R2). During stage R2, spring 150 expands until lever 140 hits a stopper 148. At the point when lever 140 hits stopper 148, the third stage (R3) begins. During stage R3, load WL can increase up to an allowable maximum mechanical limit for the scale. Stage R1 is altered by altering the distance counter weight 146 is able to slide along lever 140 (dWC), by changing the weight of counter weight 146, and by changing the distance of bearing point 158 from pivot 142.

[0055] In a Type C embodiment, an adjustable counterbalance weight arrangement replaces stopper 48 in the Type A embodiment, and the remaining arrangements of the Type A embodiment are unchanged. Thus, the Type C embodiment has a counterbalance weight arrangement, a leverage spring arrangement, and an adjustable counterbalance weight arrangement. The response for the Type C embodiment is shown in FIG. 12C. It has three stages—a nil response (during a first stage R1) and two linear responses (during a second and a third stage R2 and R3). A simplified schematic diagram of a Type C scale is shown in FIG. 14. FIG. 14 represents a scale identical to that shown in FIG. 2, except that stopper 48 has been replaced with an adjustable counterbalance weight arrangement 248. The Type C embodiment of FIG. 14 further includes a lever 240, a pivot 242, a counterbalance weight 246, a spring 250, and a virtual load bearing point 258.

[0056] In the Type C embodiment, the response of first stage R1 is identical to the response of the first stage in the Type A embodiment (compare FIGS. 12A and 12C). The response of the second stage R2 is identical to the response of the second stage in the Type A embodiment until lever 240 pushes down against adjustable counterbalance weight arrangement 248. Adjustable counterbalance weight arrangement 248 functions in the same manner as the adjustable counterbalance weight arrangement described above with respect to the Type B embodiment.

[0057] As shown in FIG. 14, arrangement 248 includes a lever 248a, a load bearing point 248b, a counterweight 248c, and a pivot 248d. The force of lever 240 against bearing point 248b causes an imbalance in lever 248a. Counterbalance weight 248c slides toward the left end (FIG. 14) of lever 248a to reestablish balance or equilibrium of lever 248a. The displacement of counterbalance weight 248c will eventually be limited by a stop at the end of lever 248a or by the action of a stopper (like stopper 48) located under the right side (FIG. 14) of lever 248a. Of course, the responses of each of stages R1, R2 and R3 can be altered as described above with respect to Type A and B embodiments.

[0058] A Type D embodiment was already introduced with reference to FIG. 11. A Type D embodiment is the fullest version of the present invention. It includes an adjustable counterbalance weight arrangement, a leverage spring arrangement, and another adjustable counterbalance weight arrangement. The response for the Type D embodiment is shown in FIG. 12D. It has three stages R1, R2 and R3, with linear responses in each stage. It functions like the Type B embodiment for the first two stages and like the Type C embodiment for the third stage (compare FIGS. 12B and 12C with 12D). A simplified schematic diagram of the Type D scale is shown in FIG. 15. FIG. 15 represents a scale identical to that shown in FIG. 2, except that lever 40 and counterbalance weight 46 has been replaced with an adjustable counterbalance weight arrangement 340, 346, and stopper 48 has been replaced with an adjustable counterbalance weight arrangement 348. The operation of the Type D embodiment of FIG. 15 is self-evident in view of the descriptions of the Type B and C embodiments.

[0059] Each one of the stages in a Type A, B, C or D embodiment may be equipped with its own controlling and sensing elements. These elements can be of a conventional type, well known in the art, or especially designed, depending on the particular weighing application.

[0060] It should now be understood that an appropriate proportionality (or sensitivity) and range can be predetermined for each operational stage of the weight scale of the present invention.

[0061] While the preferred embodiments of the invention have been particularly described in the specification and illustrated in the drawings, it should be understood that the invention is not so limited. Many modifications, equivalents and adaptations of the invention will become apparent to those skilled in the art without departing from the spirit and scope of the invention, as defined in the appended claims.

Claims

1. A weight scale including: an operational weighing range; and an overall response characteristic having a plurality of discrete stages over the operational weighing range, each stage being defined by a predetermined response characteristic.

2. A weight scale having an operational weighing range, comprising:

an overall response characteristic having at least first and second discrete stages over the operational weighing range, the first stage being defined by a first predetermined response characteristic and the second stage being defined by a second predetermined response characteristic;

first scale means for establishing the first response characteristic of the first stage; and

second scale means for establishing the second response characteristic of the second stage.

3. The weight scale of claim 2, wherein said overall response characteristic further includes a third discrete stage within its operational weighing range, the third stage being defined by a third predetermined response characteristic; and wherein said weight scale further comprises third scale means for establishing the third response characteristic of the third stage.