WO2000039541A1

WO2000039541A1 - Weighing apparatus including a planar load cell and method of use thereof

Info

Publication number: WO2000039541A1
Application number: PCT/US1999/031226
Authority: WO
Inventors: Judith Karabin
Original assignee: Spintek Gaming Technologies, Inc.
Priority date: 1998-12-31
Filing date: 1999-12-30
Publication date: 2000-07-06
Also published as: AU2221100A

Abstract

A weighing apparatus including a planar load cell (21) mounted to a base plate (20). The planar load cell (21) includes a strain gage (24) located at each of the four corners (23a, 23b, 23c, 23d) of the planar load cell (21) and two guide rails (22) for attaching a hopper (10) which may hold coins.

Description

WEIGHING APPARATUS INCLUDING A PLANAR LOAD CELL AND METHOD OF USE THEREOF

This application claims priority from U.S. Provisional Application No. 60/114,327, filed January 31, 1998, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a weighing apparatus that includes a planar load cell, and more particularly, to a weighing apparatus that includes a planar load cell that is particularly well suited for use in gaming, amusement and vending machines or the like.

2. Description of the Prior Art

For many years, slot machines have been a popular attraction at gambling casinos and other gaming establishments. Such slot machines typically include a colorful display of gaming indicia, such as cherries, plums, oranges, sevens, etc., arrayed in rows and columns across the front of the slot machine. These gaming indicia may be spun into motion for game play by the insertion of a coin into the slot machine and pulling the slot machine handle. During game play, the inserted coin is collected in a coin reservoir within the slot machine, which is commonly referred to as a "hopper." At the end of game play, the inserted coin will be retained in the hopper if there is a losing combination of gaming indicia shown or, alternatively, may be returned from the hopper to the slot machine player, perhaps with additional coins, if there is a combination of gaming indicia shown.

Periodically, slot machine hoppers must be serviced by casino technicians. For example, the hopper may have too few coins to pay out wins to players and must have its contents augmented by filling the hopper with additional coins. Also, coins might be jammed in parts of the hopper in such a way that the hopper cannot function properly. If so inclined, a dishonest technician may pilfer a few coins each time he services a slot machine. While each individual instance of such pilfering may not represent a significant threat to a casino's bottom line, the cumulative loss over time from such pilfering may be quite large. Casinos have tried to combat this problem by, among other things, assigning two or more technicians to each task requiring a slot machine to be opened. However, this approach leads lo additional labor costs and may not even help if each of the assigned technicians is dishonest.

An alternate existing solution is to seal the hopper so that only trusted money-handling employees working a cashier's cage may get to the coins. Nonetheless, slot machine hoppers are difficult to seal because such hoppers must typically give out coins after a winning play as well as receive them. Additionally, coins jamming in the hopper is also an ongoing concern. In those cases where the hopper is prone to jamming, sealing the hopper would inevitably result in greater down-time for the slot machines and create a loss of slot machine use, which could be more detrimental to the casino than the theft loss.

Thus, as should be apparent from above, merely counting coins as they go into the hopper and counting coins as they leave the hopper would not prevent theft, as a physical inventory would only indicate that coins are missing and not who took them. Prior art systems exist that count coins by weighing them. However, these devices are generally suitable for weighing coins in a money room and are generally unsuitable for weighing coins in a vibration-prone gaming machine environment where the hoppers being weighed must be enclosed to prevent theft by players.

Recently, attempts have been made to develop hopper weighing technology that utilizes load cells that include strain gauges. Generally, the load cell or load cells require both horizontal and vertical clearance. Unfortunately, in some applications, such clearance area may not be available. Furthermore, systems that utilize a load cell or load cells may be made obsolete at any time if the host device's manufacturer changes the device's interior design and hence the clearance area availability. Finally, in certain applications, a weighing system that uses a load cell or load cells, either in a retro-fit or original weighing system embodiment, may cost many times more than the hopper or coin repository being weighed and, thus, may cause the use of such a weighing system to be impractical. Hence, a weighing system that uses one or more load cells and thus achieves the accuracy benefits thereof is needed. Such a weighing system would be useful not only in slot machines, but also other gaming machines as well as amusement and vending machines that receive coins. Indeed, such a weighing system would also be useful in many manufacturing, retail and service industries for general weighing purposes.

SUMMARY OF THE INVENTION In accordance with the present invention, a weighing apparatus includes a base plate and a planar load cell coupled to the base plate. The planar load cell includes at least two strain gauges.

In accordance with one aspect of the present invention, the planar load cell includes four strain gauges.

In accordance with another aspect of the present invention, the four strain gauges are each located at a respective one of four corners of the planar load cell. In accordance with a further aspect, the weighing apparatus further includes two guide rails coupled to the planar load cell for positioning a receptacle.

In accordance with yet a further aspect of the present invention, the guide rails are adjustable. In accordance with yet another aspect of the present invention, the weighing apparatus includes ball bearings located between the base plate and the planar load cell.

In accordance with another aspect of the present invention, a method of weighing items includes providing a weighing apparatus that includes a base plate and a planar load cell coupled to the base plate. The planar load cell includes at least two strain gauges. The method further includes providing a receptacle and positioning it adjacent the planar load cell. Finally, the method includes receiving items within the receptacle and weighing the receptacle with the items therein with the planar load cell to determine a weight. In accordance with yet another aspect of the present invention, the method includes determining a count of the items within the receptacle based on the weight.

Thus, the present invention provides a weighing apparatus and method of use thereof wherein the size constraints of the interior of any slot, amusement, game or vending machine will have little effect on the size of the weighing apparatus due to its planar shape and relatively thin size. Generally, changes in the interior of the host device will be negligible. A weighing apparatus in accordance with the present invention may be moved about and secured in such a manner to accommodate the addition of transformers, additional electronic devices, currency validators, etc. within the host device.

Furthermore, since the weighing apparatus is basically a "fiat platform," embodiments with adjustable guide rails will allow for fewer models of the weighing apparatus to accommodate different types of host devices and their item receiving receptacle.

Also, the cost of manufacturing a weighing apparatus in accordance with the present invention is less than that for making weighing apparatuses using load cells in general due to its reduced size and amount of materials, thus allowing for a reduced sales cost to the end customer. A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a front view of a slot machine with its door open illustrating a coin hopper and a weighing apparatus in accordance with the present invention;

Figure 2 is a perspective view a weighing apparatus in accordance with the present invention;

Figure 3 is a side elevation view of the weighing apparatus illustrated in Figure 2; and

Figure 4 is a schematic diagram of a control system for a weighing apparatus in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EXEMPLARY EMBODIMENTS The present invention provides a planar load cell that is useful for weighing items in a variety of situations. As will be apparent to one skilled in the art, a planar load cell in accordance with the present invention may be designed and sized to weigh all types of items both large and small, and will have numerous applications in various industries and situations. For clarity and simplicity, a planar load cell in accordance with the present invention will be described in an embodiment for use in weighing coins in a gaming, amusement or vending machine, and more particularly, in an embodiment for use with a slot machine. Figure 1 illustrates a slot machine 10 that includes a coin hopper assembly

1 1. Coin hopper assembly 11 includes a coin weighing apparatus 12 in accordance with the present invention. Coin hopper assembly 1 1 includes a coin hopper 13 and hopper base plate 14. In order to illustrate the placement of the hopper assembly 1 1 in slot machine 10, hopper door 15 of slot machine 10 is shown in an open position. Nonetheless, during operation, hopper door 15 would ordinarily be locked shut to prevent theft of coins. As illustrated in Figure 1, hopper 13 is generally placed below a coin insertion slot 16 and above a coin pay-out tray 17.

To initiate play of the game, a player would insert one or more coins into coin insertion slot 16 and those coins would drop into coin hopper 13. Although not shown in Figure 1, the coins would typically pass through a coin handling unit on their way to coin hopper 13. This coin handling unit performs tests (size, weight, angular momentum, etc.) to determine if the coin is real and the proper denomination. The coin handling unit, or other device, will provide a signal, such as an electric "coin-in" pulse, to a logic board to indicate that a valid coin has been inserted. If the game is a winning game, or the player cashes out his or her credits, coin hopper 13 ejects the correct amount of coins from ejection slot 18 into pay-out tray 17. In some embodiments, such as so-called "slant-top" slot machines, the hopper 10 is actually located below the pay-out tray and an "elevator" or "escalator" mechanism is used to raise the paid-out coins higher than the pay out tray so that the coins will fall into the pay-out tray, and thus be accessible to the player. Typically, a motorized conveyor (not shown) of coin hopper 13 causes coins to be ejected to the pay-out tray or elevator and the conveyor assembly runs until a "coin-out" counter indicates that the correct number of coins have been ejected.

Figures 2 and 3 illustrate weighing apparatus 12. Weighing apparatus 12 includes a base plate 20 and a planar load cell 21. Base plate 20 may consist of any suitable material such as, for example, metal, metal alloy, plastic or ceramic. Preferably, two guide rails 22 are also provided. Guide rails 22 are used to properly position coin hopper assembly 11. Guide rails 22 may be adjustable to accommodate hoppers of different sizes.

Guide rails 22 are preferably mounted in parallel with suitable fasteners, such as hex bolts 25. Guide rails 22 are preferably mounted in parallel such that they face one another. Alternatively, guide rails 22 may be arranged differently in order to accommodate different types of coin hopper assemblies 11 and other receptacles. Guide rails 22 arc used to firmly hold base plate 14 of coin hopper assembly 1 1 in its correct position. As previously mentioned, one of guide rails 22 may be laterally adjustable to accommodate different sizes of hopper base plates, or other receptacle base plates, 14. Guide rail 14 may be made laterally adjustable by machining a lateral slot or series of holes within planar load cell 21 to allow such a guide rail to be affixed with fasteners to load cell 21 at a variety of positions.

Load cell 21 generally consists of some type of metal alloy, such as, for example, aluminum. Each corner 23a, b, c, d of load cell 21 preferably includes some type of "cut-out" design. As can be seen in Figure 2, a preferred design is a substantially rectangular shape and two opposed semi-circles defined about halfway along the length of the rectangle as well as two opposed circles defined within each corner. Obviously, other shapes may be designed by those skilled in the art.

Each corner includes an electronic wafer circuit 24 that is affixed thereto. The wafer circuit may be affixed internally within the cut-out design or on the surface of the alloy. The four wafer circuits measure changes within the cut-out corners, such as deflections or "bendings" due to force applied to the load cell when weight is placed thereon. Thus, the four corners serve as four strain gauges that cooperate to create planar load cell 21. An example for dimensions for planar load cell 21 for use in a gaming machine is approximately 9-10 inches by 8.5-9.5 inches and a thickness of approximately .65-.85 inches. The strain gauges are approximately 3-4 inches long and .3-.7 inches wide. The circles and semi-circles have approximately .15-.35 inches. Obviously, those skilled in the art realize that these dimensions will vary based upon the application, the size requirements and the amount of weight the load cell needs to support as well as the accuracy desired and the material with which the load cell is made. Thus, these dimensions are merely examples. While the preferred embodiment includes a strain gauge at each corner, more or fewer strain gauges may be used as designed by one skilled in the art. Indeed, as many as sixteen strain gauges have been successfully used in creating a weighing apparatus in accordance with the present invention. As few as two have also been used. In fact, as development with ceramic strain gauges continues, it may be possible to create a load cell 21 in accordance with the present invention that only uses one strain gauge.

Additionally, while the planar load cell is illustrated as substantially square in shape, other shapes may be used. However, when creating planar load cell 21, those skilled in the art will realize that the strain gauges must be coordinated or "balanced" in order to ensure the desired accuracy for the load cell since the strain gauges work together to measure the deflections within the load cell when weight is applied thereon.

In a preferred embodiment, the four strain gauges are arranged in a "wheatstone bridge" configuration. Since the four strain gauges cooperate and work together to eventually form a load cell, one signal or channel of information is transmitted from logic board or weight control board 31. Currently, logic board 31 is capable of transmitting three channels of information to the host device's control system. Hence, with the present invention, two channels are available for other purposes.

The strain gauges, through the wafer circuits, emit an analog, voltage differential as they sense the change in the load cell's shape due to deflection caused by weight. The voltage potential increases as more weight is applied to the load cell. The analog, voltage differential is transmitted via communication channel 30, which may be, for example, metal wiring, fiber optics, or other suitable communication channels that are well known, to logic board 31 , which translates the analog signal into a standard digital signal. This digital signal is used by proprietary software to indicate, via user interface, the precise amount of weight being applied to the load cell.

The ability of the load cell to be precise in weighing assessment is primarily a function of the consistent metal alloy throughout the load cell. A consistent alloy, without impurities or random anomalies deflects or "bends" according to the malleability/tensile indices of the alloy. Also, the contraction and expansion of the consistent alloy due to temperature changes is a known index. These temperature changes may be compensated for by software (either in the strain gauge or logic board 31 or within the host device itself). Conversely, an inconsistent alloy, or an alloy with varying density due to imprecise forging, cannot provide for concise measurable deflection or consistent temperature or induced contraction/expansion.

Thus, planar load cell 21 is created from a consistent metal alloy, which in a preferred embodiment is aluminum. Corners 23 a, b, c, d, are then "forged" appropriately and affixed with wafer circuits 24 to thereby create the strain gauges.

Planar load cell 21 is coupled to base plate 20 via small, stand-off studs 32. In a preferred embodiment, ball bearings 36 arc placed between planar load cell 21 and base plate 20 to support load cell 21 in a more freestanding manner, thus improving accuracy. The distance between planar load cell 21 and base plate 20 may be as little as a few millimeters, thus allowing weighing apparatus 12 to be relatively thin.

Communication channel 34 is provided to transmit information from planar load cell 21 to the host device, in this instance, slot machine 10. Communication channel 34 may once again be any suitable communication channel that is well known in the art, such as metal wiring, fiber optics, radio waves, etc. Referring now to Figure 3, a schematic of a preferred control system for use in the present invention is illustrated.

Logic board 31 preferably includes an analog-to-digital converter 40 coupled to load cell 21 to convert a load signal from an analog signal to a digital load cell sample. In the preferred embodiment, the digital load cell sample has a resolution of 20 bits, but other resolution analog-to-digital converters may also be used (e.g. 14 bits or greater). With a lower resolution 14 bit digital load cell, an integer corresponding to the digital load cell sample may range from 0 to 16,383. With proper calibration and proper design of planar load cell 21, a fully loaded hopper will cause a reading near the top end of the range so as to have the best resolution. Analog-to-digital converter 40 provides its output to an input-output controller 41, which in turn provides samples, as requested, to a central processing unit 42. A suitable I/O controller for the present invention would be a 75HTC245 chip. Central processing unit 42 executes programs stored in program memory 43 and uses a variable memory 44 to store data incident to the execution of those programs. In some embodiments, a central processing unit with built-in input/output functions and/or memory may be used.

In use, the coin hopper assembly is coupled to planar load cell 21 via the hopper base plate 14 and guide rails 22. The system is essentially "zeroed" or calibrated, and as coins are received within coin hopper 13, planar load cell 21 is deflected or bent from the additional weight. Corners 23 a, b, c, d, serving as strain gauges, measure the deflection of planar load cell 21 and transmit signals to logic board 31. Logic board 31 converts these analog signals to digital signals and arrives at a weight. Logic board 31 may also be calibrated to know the weight per coin and thus, may determine a total number of coins by dividing the total weight by the weight per coin.

The present invention thus provides a thin, yet accurate load cell for weighing items. Currently, a .006 accuracy has been achieved. Current standards in the gaming industry require at least a .004 accuracy. Based upon the ability of the present invention to determine an accurate coin count within coin hopper 13, the present invention is able to inform the operator of slot machine 10 that the hopper is close to empty. Hence, hopper "empties" and thus slot machine down-time for filling may be reduced since the hoppers may be filled when slot machine 10 is actually idle and its coin count is low rather than waiting until the coin hopper is actually empty.

The present invention allows the amount of the fill to be verified without anyone actually counting the coins. During a fill, as the weight changes, the number of coins added to the hopper may be determined. Accordingly, a hopper may be weighed periodically and that weight may be used, combined with an automatically per coin weight, to detemiine a number of coins in the hopper. In use with slot machines, coins may be counted as the hopper door is opened and then counted again when the hopper door is closed and this difference may be compared to an authorized difference to determine if an unauthorized removal of coins from the hopper while the hopper door was opened occurred. While the weighing apparatus has been illustrated as a "platform," those skilled in the art will understand that the planar load cell may be configured in a vertical configuration such that the receptacle would hang from the planar load cell at the side or from above. The planar load cell would then bend or deflect due to "pulling" forces as opposed to "pushing" forces. Although the invention has been described with reference to specific exemplary embodiments, it will be appreciated that it is intended to cover all modifications and equivalents within the scope of the appended claims.

Claims

WHAT IS CLAIMED IS: 1. A weighing apparatus comprising: a base plate; and, a planar load cell coupled to the base plate, the planar load cell including at least one strain gauge.

2. A weighing apparatus in accordance with claim 1 wherein the planar load cell includes two strain gauges.

3. A weighing apparatus in accordance with claim 2 wherein the planar load cell includes four strain gauges.

4. A weighing apparatus in accordance with claim 3 wherein the four strain gauges are each located at a respective one of four comers of the planar load cell.

5. A weighing apparatus in accordance with claim 1 further comprising two guide rails coupled to the planar load cell for positioning a receptacle.

6. A weighing apparatus in accordance with claim 5 wherein at least one of the guide rails is adjustable.

7. A weighing apparatus in accordance with claim 1 further comprising ball bearings located between the base plate and the planar load cell.

8. A weighing apparatus for a coin receptacle in a gaming, amusement or vending machine the weighing apparatus comprising: a base plate; and a planar load cell adjacent the base plate, the planar load cell including at least one strain gauge and two guide rails coupled to the planar load cell for positioning the coin receptacle.

9. A weighing apparatus in accordance with claim 8 wherein the planar load cell includes at least two strain gauges.

10. A weighing apparatus in accordance with claim 9 wherein the planar load cell includes at least four strain gauges.

11. A weighing apparatus in accordance with claim 8 further comprising ball bearings located between the base plate and the planar load cell.

12. A weighing apparatus in accordance with claim 1 1 wherein the planar load cell includes eight strain gauges.

13. A weighing apparatus in accordance with claim 12 wherein the planar load cell includes sixteen strain gauges.

14. A weighing apparatus in accordance with claim 8 wherein the four strain gauges are each located at a respective one of four comers of the planar load cell.

15. The weighing apparatus of claim 8 wherein the gaming, amusement or vending machine is a slot machine.

16. A weighing apparatus in accordance with claim 8 wherein at least one of the guide rails is adjustable.

17. A method of weighing items, the method comprising: providing a weighing apparatus comprising: a base plate; and, a planar load cell coupled to the base plate, the planar load cell including at least one strain gauge; providing receptacle; positioning the receptacle adjacent the planar load cell; receiving items in the receptacle; and weighing the receptacle with the items therein with the planar load cell to determine a weight.

18. The method of claim 17 further comprising determining a count of the items within the receptacle based on the weight.

19. A method of weighing coins received in a slot machine, the method comprising: providing a slot machine including a coin hopper adjacent a weighing apparatus, the weighing apparatus comprising: a base plate; and, a planar load cell coupled to the base plate, the planar load cell including at least four strain gauges and two guide rails coupled to the planar load cell for positioning the coin hopper; receiving coins in the coin hopper; and weighing the coin hopper with the coins therein with the planar load cell to detennine a weight.

20. The method of claim 19 further comprising determining a count of the coins within the coin hopper based on the weight.

21. A planar load cell comprising a substantially flat, planar plate of metal configured to deform and at least one strain gauge.

22. A planar load cell in accordance with claim 21 wherein the planar load cell comprises at least two strain gauges.

23. A planar load cell in accordance with claim 22 wherein the planar load cell comprises at least four strain gauges.

24. An integrated item receptacle and item weighing apparatus comprising: an item receptacle; a base plate; and a planar load cell including at least one strain gauge inteφosed between and coupled to the item receptacle and the base plate.

25. An integrated item receptacle and item weighing apparatus in accordance with claim 24 wherein the planar load cell includes at least two load cells.

26. An integrated item receptacle and item weighing apparatus in accordance with claim 25 wherein the planar load cell includes at least four strain gauges.

27. An integrated item receptacle and item weighing apparatus in accordance with claim 26 wherein the four strain gauges arc each located at a respective one of four comers of the planar load cell.

28. An integrated item receptacle and item weighing apparatus in accordance with claim 24 further comprising two guide rails coupled to the planar load cell for positioning the item receptacle.

29. An integrated item receptacle and item weighing apparatus in accordance with claim 28 wherein at least one of the guide rails is adjustable.

30. An integrated item receptacle and item weighing apparatus in accordance with claim 24 further comprising ball bearings located between the base plate and the planar load cell.

31. An integrated item receptacle and item weighing apparatus in accordance with claim 24 further comprising an analog-to-digital converter coupled to the at least one strain gauge.

32. An integrated item receptacle and item weighing apparatus in accordance with claim 24 wherein the item receptacle is a coin hopper and the weighing apparatus is a coin weighing apparatus.