Abstract:
An improved method and apparatus for selection of vendible products provides designated product reference areas at a refrigerated double glass front vending machine for making viewable product selections thereon by applying a light tap at its outer glass pane and sensing the tap location by three or more spaced apart resilient members each having its first portion attached at the inner glass pane. The resilient member&#39;s second portion suspends an inertia mass that reciprocates at a predetermined rate due to the inertia mass weight and the resiliency of the suspending member. A sensor senses the reciprocating movement in response to the light tap. The predetermined reciprocating rate is designed to be less than the natural rear to front movement of the inner glass pane but greater than most of the other vibration times that occur due to the tap. The location of the tap is determined by measuring the arrival time of each predetermined signal produced by the first resonating alternation of its attached resiliently suspended inertia mass during the first rearward movement of the inner glass pane. A variation of the method incorporates attaching the first portions of three of more spaced apart resilient piezo sensor discs that have the second portions suspending an attached inertia mass which reciprocates at the predetermined rate when a light tap arrives and produces the predetermined signal. A further variation incorporates an independently suspended inertia mass to maintain its reference to the resilient member second portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to Provisional Application Ser. No. 61/034,483, filed on Mar. 6, 2008. The contents of this application are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The viewing of selectable products from within a refrigerated glass front vending machine typically include two spaced apart transparent glass panes for providing thermal insulation. The customer selects from among the designated viewable products by depressing designated selection buttons located off to one side of the viewing area, and having entered sufficient credit for the selection receives the vended product. 
       BACKGROUND OF THE INVENTION 
       [0003]    A customer enters the identification associated with one of the many viewable products within a glass front vendor and makes a two digit entry on a keypad or selection buttons located away from the viewed products. Many different selection methods are used to select products from a vending machine, ranging from depressing alpha-numeric marked buttons that activate sensors, to the touching of identified areas on a screen or panel. 
         [0004]    Many known technologies for identifying areas of touch on a screen could be utilized such as Acoustic Pulse Recognition (APR) which comprises a glass display overlay or other rigid substrate, with four piezoelectric transducers mounted on the back surface. The transducers are mounted on two diagonally opposite corners out of the visible area and connected via a flex cable to a controller card. The impact when the screen is touched, or the friction caused while dragging between a user&#39;s finger or stylus and the glass, creates an acoustic wave. The wave radiates away from the touch point, making its way to the transducers which produce electrical signals proportional to the acoustic waves. These signals are amplified in the controller card and then converted into a digital stream of data. The touch location is determined by comparing the data to a profile. The APR is designed reject ambient and extraneous sounds, as these do not match a stored sound profile. The key is that a touch at each position on the glass generates a unique sound. Four tiny transducers attached to the edges of the touch-screen glass pick up the sound of the touch. The sound is then digitized by the controller and compared to a list of prerecorded sounds for every position on the glass. The cursor position is instantly updated to the touch location. By using the sound generated when a finger or stylus touches the glass, APR allows users to touch the screen with practically anything, such as a fingernail, gloved hand, pen or corner of credit card. 
         [0005]    Dispersive Signal Technology (DST) represents a fundamentally different approach to touch. Unlike other solutions that recognize touch by the interruption of electrical fields, acoustic waves, optical fields, or infrared light, Dispersive Signal Technology recognizes touch by interpreting bending waves created in the overlay substrate via the impact of a touch. DST locates sensors in each corner of the touch screen, which measure the vibration energy. Advanced dispersion adjustment algorithms are then applied to the data, allowing accurate reporting of each touch. This approach helps eliminate issues with screen contaminants and surface scratches, and also allows a touch to be registered while a palm and/or object is resting on the screen&#39;s surface. A finger, gloved hand or stylus can initiate a touch while a person&#39;s palm and drink are on the surface. The touch creates a vibration, which radiates a bending wave through the substrate from the point of contact spreading out to the edges, and the resting items are ignored as they do not generate any vibration energy. 
         [0006]    An established technology using waves to detect contact is Surface Acoustic Wave (SAW), which generates high frequency waves on the surface of a glass screen, and their attenuation by the contact of a finger, is used to detect the touch location. This technique is “time-of-flight”, where the time for the disturbance to reach one or more sensors is used to detect the location. Such an approach is possible when the medium behaves in a non=dispersive manner i.e. the velocity of the waves does not vary significantly over the frequency range of interest. A contact sensitive device comprising a member capable of supporting bending waves, having a plurality (e.g. three or more) sensors mounted on the member for measuring bending wave vibration in the member, whereby each sensor determines a measured bending wave signal. A processor calculates a location of a contact on the member from the measured bending wave signals, in that the processor calculates a phase angle for each measured bending wave signal, and then calculates a phase difference between the phase angles of least two pairs of sensors from which the location of the contact is determined. Ultrasonic acoustic wave contact detecting apparatuses are in widespread use. Examples of their applications include operating screens of personal computers, ticket dispensers at train stations, copiers installed in convenience stores and ATM&#39;s at financial institutions. These acoustic wave contact detecting apparatus utilize transducers, including piezoelectric vibrators provided on a substrate (touch panel) formed of glass or the like. These transducers function both as generating means for bulk waves and as sensors for detecting acoustic waves which are scattered by a finger or the like that contacts the touch panel. The surface acoustic waves are scattered by a finger or the like. The scattering of the surface acoustic waves is detected by detection means. The detected signal is referenced against a clock signal of a controller, and the position at which the surface acoustic waves are scattered is determined. 
         [0007]    Another method for locating the positions of fingers knocking on a pane of glass is Acoustic Tap Tracking (ATT). The finger tap excitation can change considerably from one hit to the next. Variations occur depending on how the glass is struck, the type of glass used, and how the glass is supported. Contact pickups made of polyvinylidene fluoride (PVDF) piezoelectric foil  52 , are placed near the perimeter of a glass pane produce signals when the glass is hit. They are bonded with common adhesive to a glass window solidly supported by rubber anchors along its entire perimeter. To track taps more reliably, using a simple static threshold is generally not adequate. Amplitude dependence is one factor, because the leading edge for a knuckle-tap is not sufficiently abrupt. The characteristics of the first arrival can vary widely from transducer to transducer and impact to impact. A significant problem posed by the variable amount of low-amplitude, higher-frequency, dispersive deflection often arrives before the main wavefront. Likewise, sharp impacts (e.g., snapping a metal ring against the glass instead of one&#39;s knuckle) excite rapidly moving modes. A microcontroller continuously digitizes the analog signals, from four transducers into 10 bits at over 10 kHz enables a more detailed and robust embedded analysis to look at other waveform features (e.g., peak amplitudes and waveform shape) for each tap. The microcontroller continuously samples the signals from each transducer into a rotating buffer. Upon detecting a transducer signal above a noise threshold, a “knock” event is declared, and 10 millisecond (ms) worth of data are stored from all four inputs (including 3 ms of data before the trigger occurs). This buffer is then scanned for every significant peak in the absolute-value waveform produced by each transducer, and descriptive parameters (e.g., peak height, width, and mean arrival time relative to the initial trigger) are extracted for each peak including any small peaks arriving earlier. These parameters are sent, together with a count of the number of zero-crossings across the data acquisition interval (too many zero crossings indicate a sharp hit with different timing). A connected personal computer then processes the timing determined for each first peak by a second order polynomial that was obtained from a linear least-squares fit to a set of calibration to produce an estimate of the impact location in Cartesian coordinates. In addition to increasing the reliability of the results, the use of a microcontroller readily enables more channels of gestural input (e.g., measuring the strike intensity and classifying the type of strike). Also extracted is an estimate of accuracy or validity by crosschecking the detected waveform characteristics from the different sensors and examining the differences between the four position estimates obtained from the four different sensor triplets (since there are four pickups, there is one redundant degree of freedom). The sensor strips are very small and do not significantly block the window&#39;s view. 
         [0008]    The present invention provides a simple method to utilize the typical double glass pane construction of a refrigerated glass front vending machine for making product selections on the glass front without modifying the glass panes or their support, and without requiring sensors on the outer glass pane. It does not require the generation of high frequency waves, nor does it utilize the high frequency sounds from the touching of the outer glass pane. 
       SUMMARY OF THE INVENTION 
       [0009]    This invention provides an improved vending machine apparatus and method for selecting viewable products through its glass front pane by applying a light tap at the relative product designation on the glass front pane. The designations are positioned relative to the products and require only one light tap of the finger to make the product selection, and without having to look away from the viewable product. The method provides a simple and effective way to determine a product selection at a typical refrigerated glass front vending machine having two spaced apart glass panes without requiring any apparatus at the outer glass pane. No changes are required for the glass panes, their mounting, and insulation design. A single light tap by the customer at the product designation on the outside glass pane transfers the lateral movement rearward to the inner glass pane through the insulated space there between and causes three or more spaced apart and resiliently suspended inertia masses to develop their unique rate of movement which are sensed and provide outputs which are used to determine the product selected. 
         [0010]    Thus according to one aspect of the invention there is provided a method of vending a viewable product within a refrigerated, double glass front vending machine comprising the steps of: (a) detecting a light tap by a customer on a selectable product reference area on the outer glass pane area by use of at least three or more spaced apart piezo discs with their resilient first portions attached to the inner glass pane and oriented in the same general plane therewith; (b) providing a suspended inertia mass attached to each of the piezo discs resilient second portions; (c) monitoring the resultant signals produced when the inner glass pane area is first moved rearward from its rest position and in respect to the suspended inertia mass movement and the resilient piezo disc attached first portions; (d) determining the arrival times of said signals; (e) comparing the arrival time intervals between the at least three sensors to the acceptable arrival time intervals stored in memory for each product reference area; (f) determining the selected product reference area; (g) determining the selected product and its value; (h) determining that the amount credited to the customer at least equals the selected product value; (i) vending the product selected; and (j) refunding any over credited amounts. 
         [0011]    According to yet another aspect of the invention there is provided a method of vending a viewable product within a refrigerated, double glass front vending machine comprising the steps of: (a) detecting a light tap by a customer on a selectable product reference area on the outer glass pane area by use of three or more spaced apart resilient members with their first portions attached about the inner glass pane and with a suspended inertia mass at its unattached second portion; (b) sensing the relative movement between the suspended inertia mass and the resilient member attached first portions, using piezo, resistive, capacitive, inductive, or optical sensors; (c) monitoring the resultant sensor signal produced when its inner glass pane area is first moved rearward from its rest position and in respect to the movement of its suspended inertia mass; (d) determining the arrival times of the sensor signals; (e) comparing the arrival time intervals between at least three sensors to the acceptable arrival time intervals stored in memory for each product reference area; (f) determining the selected product reference area; (g) determining the selected product and its value; (h) determining that the amount credited to the customer at least equals the selected product value; (i) vending the product selected; and (j) refunding any over credited amounts. 
         [0012]    According to yet another aspect of the invention there is provided a method of vending a viewable product within a refrigerated, double glass front vending machine comprising the steps of. (a) detecting a light tap by a customer on a selectable product reference area on the outer glass pane area by use of three or more spaced apart resilient members with first portions attached about the inner glass pane, each with a suspended inertia mass at its unattached second portion; (b) providing a suspended inertia mass and resilient member combination that resonates at a selected rate faster than the natural inner glass pane&#39;s lateral movement (c) sensing the relative movement between the suspended inertia mass and the resilient member attached first portion, using piezo, resistive, capacitive, inductive, or optical sensors; (d) monitoring the resultant sensor signal produced when its inner glass pane area is first moved rearward from its rest position and in respect to the movement of its suspended inertia mass; (e) determining the arrival times of said signals; (f) comparing the arrival time intervals between at least three sensors to the acceptable arrival time intervals stored in memory for each product reference area; (g) determining the selected product reference area; (h) determining the selected product and its value; (i) determining that the amount credited to the customer at least equals the selected product value; (j) vending the product selected; and (k) refunding any over credited amounts. 
         [0013]    According to yet a further aspect of the invention there is provided a method of vending a viewable product within a refrigerated, double glass front vending machine comprising the steps of: (a) detecting a light tap by a customer on a selectable product reference area on the outer glass pane area by use of three or more spaced apart resilient members with first portions attached about the inner glass pane, each with a suspended inertia mass at its unattached second portion; (b) providing a suspended inertia mass and resilient member combination that resonates at a selected faster rate than the natural inner glass pane&#39;s lateral movement (c) sensing the relative movement between the suspended inertia mass and the resilient member attached first portion, using piezo, resistive, capacitive, inductive, or optical sensors; (d) monitoring the resultant sensor signal produced when the inner glass pane is first moved rearward from its rest position and in respect to the movement of its suspended inertia mass; (e) identifying the first alternation of each suspended inertia mass to determine the arrival times of said signals; (f) comparing the arrival time intervals between at least three sensors to the acceptable arrival time intervals stored in memory for each product reference area; and (g) communicating the selected product to a microprocessor. 
         [0014]    According to yet a further aspect of the invention there is provided a method of vending a viewable product within a refrigerated, double glass front vending machine comprising the steps of (a) detecting a light tap by a customer on a selectable product reference area on the outer glass pane area by use of three or more spaced apart resilient members with first portions attached about the inner glass pane, each with a suspended inertia mass at its unattached second portion; (b) providing a suspended inertia mass and resilient member combination that resonates at a selected faster rate than the natural inner glass pane&#39;s lateral movement (c) sensing the relative movement between the suspended inertia mass and the resilient member attached first portion, using piezo, resistive, capacitive, or optical sensors; (d) monitoring the resultant sensor signal produced when the inner glass pane is first moved rearward from its rest position and in respect to the predetermined movement of its suspended inertia mass; (e) identifying a designated threshold level of the first alternation of each suspended inertia mass to determine the arrival times of said signals; (f) comparing the arrival time intervals between at least three sensors to the acceptable arrival time intervals stored in memory for each product reference area; and (g) communicating the selected product to a microprocessor. 
         [0015]    According to yet a further aspect of the invention there is provided a method of vending a viewable product within a refrigerated, double glass front vending machine comprising the steps of: (a) detecting a light tap by a customer on a selectable product reference area on the outer glass pane area by use of at least three space located apart resilient members on the inner glass pane, having their first portions attached thereto, and each with a suspended inertia mass at its unattached second portion; (b) providing a suspended inertia mass and resilient member combination that favors the direction of the inner glass pane&#39;s natural lateral movement but designed to resonate at a faster rate (c) sensing the relative movement between the suspended inertia mass and the attached resilient member&#39;s first portion, using piezo, resistive, capacitive, or optical sensors; (d) monitoring the resultant sensor signal produced when the inner glass pane is first moved rearward from its rest position and in respect to the movement of its suspended inertia mass; (e) identifying a designated threshold level of the first alternation of each suspended inertia mass to determine the arrival times of said signals; (f) comparing the arrival time intervals between at least three sensors to the acceptable arrival time intervals stored in memory for each product reference area; and (g) communicating the selected product to a microprocessor. 
         [0016]    According to yet a further aspect of the invention there is provided a method of indicating a viewable item within a glass front vending machine comprising the steps of. (a) detecting a light tap by a customer on a selectable product reference area on the glass pane area by use of at least three space located apart resilient members having their first portions attached thereto, and each with a suspended inertia mass at its unattached second portion; (b) providing a suspended inertia mass and resilient member combination that favors the glass pane&#39;s natural lateral movement but resonates at a faster rate (c) sensing the relative movement between the suspended inertia mass and the resilient member attached first portion, using piezo, resistive, capacitive, inductive, or optical sensors; (d) monitoring the resultant sensor signal produced when the glass pane is first moved rearward from its rest position and in respect to the movement of its suspended inertia mass; (e) identifying a designated threshold level of the first alternation of each suspended inertia mass to determine the arrival times of said signals; (f) comparing the arrival time intervals between at least three sensors to the acceptable arrival time intervals stored in memory for each product reference area; and (g) communicating the selected item. 
         [0017]    According to yet a further aspect of the invention there is provided a method of indicating a viewable item within a glass front vending machine comprising the steps of. (a) detecting a light tap by a customer on a selectable product reference area on the glass pane area by use of three or more spaced apart resilient members having their first portions attached thereto, and each with a suspended inertia mass at its unattached second portion; (b) providing a suspended inertia mass and resilient member combination that favors the glass pane&#39;s natural lateral movement but resonates at a faster rate; (c) providing a suspended inertia mass and resilient member combination that is resilient enough to resist responding to the glass movements that are less than the expected light tap of a finger and to oscillate the suspended inertia mass when it equals or exceeds it; (d) sensing the relative movement between the suspended inertia mass and the resilient member attached first portion, using piezo, resistive, capacitive, inductive, or optical sensors; (e) monitoring the resultant sensor signal produced when the glass pane is first moved rearward from its rest position and in respect to the movement of its suspended inertia mass; (f) identifying a designated threshold level of the first alternation of each suspended inertia mass to determine the arrival times of said signals; (g) comparing the arrival time intervals between at least three sensors to the acceptable arrival time intervals stored in memory for each product reference area; and (h) communicating the selected item. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a front view of a refrigerated glass front vending machine door showing a typical placement of components for a customer to view, deposit credit for, select, and receive a vended product; 
           [0019]      FIG. 2  is a front view of a preferred embodiment showing the glass front of a vendor with product designations located thereon and in relationship to products visible therein; 
           [0020]      FIG. 3A  is a diagrammatic cross sectional side view depicting the natural lateral movement of the two spaced apart glass panes when a tap occurs, and the interaction with a resilient suspended inertia mass shown with dashed tracings depicting the movements; 
           [0021]      FIG. 3B  is a sketch of the glass front and inertia mass movements of  FIG. 3A , superimposed; 
           [0022]      FIGS. 4A ,  4 B, and  4 C are drawings of typical output signals from a sensor detecting the interaction of a resiliently suspended inertia mass when a light tap occurs on the glass pane when it is nearby, about the middle, and beyond the middle; 
           [0023]      FIG. 5  is a drawing depicting output signals from two sensors arriving at two different times, and shown in relationship to the inner glass pane movement; 
           [0024]      FIG. 6  is a drawing depicting a sensor output signal that may be altered by a superimposed glass pane movement while that developed by the predetermined resilient suspended inertia mass; 
           [0025]      FIG. 7  through  FIG. 12  show drawings representing light taps occurring at various product designations on the glass front relative to six sensor placements; 
           [0026]      FIGS. 13A and 13B  are sketches showing the cross sectional side and front views, respectively, of a piezo disc sensor having its first portion attached to a glass pane and its unattached second portion pressed against by an separately suspended inertia weight; 
           [0027]      FIGS. 14A and 14B  are sketches showing the cross sectional side and front views, respectively, of a resilient member of a piezo disc with its first portion attached to a glass pane and its second portion having an inertia weight affixed thereto; and 
           [0028]      FIG. 15  is a chart showing time intervals in milliseconds, when a light tap occurs at various product designations, according to the principals of  FIGS. 7 through 12 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0029]    Referring to the figures there is generally illustrated therein a preferred embodiment of a glass front vending machine that incorporates the principles of this invention. While the preferred embodiment of this invention will be described with its applicability to a glass front vending machine for refrigerated products, it will be understood that the broad principles of the invention are not limited to such product selection application or to the specifics of the preferred embodiment disclosed. The described disclosure represents one clear example of a selection system incorporating the principles of the claimed invention, but the invention is not intended to be construed in a limiting manner as a result of the preferred embodiment disclosure. 
         [0030]    Referring now to  FIG. 1 , there is generally illustrated a glass front vending machine  20 , with its glass front  22  for viewing the available identified products for selection, the keypad  24  for making a double digit entry of the selected product, the credit entry portion  26  for depositing bills and/or credit cards, the coin entry portion  27 , and its product delivery port  28 . The coin return  30  provides the location for coin refunds to be made. The customer typically determines the available products by viewing them through the glass front  22  and determines the double digit product identifier and then looks over to the keypad  24  and depresses the appropriate two keys in proper succession. If the amount of credit he has deposited at the credit entry portion  26  at least equals the value assigned to the product he has selected, then the vending machine transfers the product to the customer to the delivery port  28 . 
         [0031]    Referring now to  FIG. 2  wherein is depicted a front view of a glass front pane  32  with double digit product references placed thereon for a customer to select by a single light tap. Eight product references are shown arranged in the top row beginning with the product identifiers  10  thru  17 , and down to the last row marked  50  through  57 . 
         [0032]    A cross sectional side view in  FIG. 3A  depicts a double pane glass front with a finger  34  applying a light tap at the outer glass pane  36  with its upper end  38  and lower end  40  secured by the upper frame  42  and lower frame  44 , respectively. The glass pane  36  is approximately 50 inches high by 24 inches wide. When the tap occurs, the resilient outer glass pane  36  moves back away from the applied tap and presses against the inert gas  46  sealed between the outer glass pane  42  and the spaced behind inner glass pane  48 . The resultant pressing of the sealed inert gas  46  causes the inner glass pane  48  to begin to move rearward (away) beginning directly behind the tap location and moving outwardly from that point. For purposes of illustration there is shown an attachment  50  to the inner glass pane  48  right in line with the tap coming from the finger  34  which is then abruptly moved rearward (away) and has attached to it the lower portion of a resilient member  52 , having its upper portion  53  attached with an inertia mass  54 . The inertia mass  54  characteristic tendency to remain in its present state causes the resilient member  52  to flex in overcoming the inertia mass. While the inner glass pane  48  is in the process of its rearward movement from the tap, the rate of deflection of the inertia mass and its energy storing resilient member  52  is designed to oscillate more than once during the rear inner glass pane  48  movement from its rest position, to its furthest rearward position. The rate of oscillation of the inertia mass  54  provides a distinguishable signal from others that may occur with various tap types, locations and magnitudes thereof. The rearward movement of the inner glass pane  48  and the attachment  50  is depicted moving away and returning back through its initial position by the tracing  56 . During the reward movement shown by the tracing  56 , portion  58 , the imparted movement through the resilient member  52  with its suspended inertia mass  54  causes its oscillation to occur more than once during that time as depicted at the tracing  60 . In this preferred embodiment there is utilized a piezo sensor comprised of its resilient member  52  and the piezo element  68 . Wires  70  and  72  provide the connection for the piezo sensor output signal developed by the inertia mass  54  with its resilient member  52 . It is very important to note that the resilient member  52  should be resilient enough to resist the glass movements that are less than the expected light tap of a finger and respond to the light tap to oscillate the suspended inertia weight. This eliminates most of the unnecessary vibrations that may occur, and utilizes the primary tap energy to operate the resiliently suspended inertia mass. 
         [0033]    In  FIG. 3B  the tracings  56  and  60  are shown in a combined tracing  62 . The indication of the very first predetermined rate of oscillation of the inertia mass  54  in  FIG. 3A , is the alternation  64  of the tracing  60 , shown also in  FIG. 3A . 
         [0034]    In the present invention the initial sounds produced within and around the outer glass pane by a tap are somewhat isolated from the spaced apart inner glass pane by the space between them. The two rectangular glass panes are sealed and suspended at their outer edge. The rate of natural lateral movement of the edge supported inner glass pane of a typical refrigerated glass front vending machine may occur in the vicinity of 60 to 100 times per second, whereas the frequency of the sounds produced by an initial impact within and about the surface of the outer glass pane can range up to thousands of times per second. An applied perpendicular tap causes the glass pane to bend away (backward) from the applied tap and then return (forward) at its natural lateral movement rate, which is primarily dependant on the glass pane dimensions, thickness, resilience and edge mounting. A further variable can be attributed to the location of the tap, as well as the temperature of the glass pane. Using an assumed rate of 70 times a second, with a time period of about 14 ms (milliseconds), the total time of its bending backward from rest position would be approximately 7 ms and the total time of bending forward would also be approximately 7 ms. 
         [0035]    The majority of the energy imparted by a tap to the outer glass pane is generally perpendicular to it and provides a resulting natural glass flexing movement. In the preferred embodiment the initial rearward deflection caused by the tap is transferred to the inner glass pane having a number of spaced apart piezo sensors affixed thereto, each with a suspended inertia mass and its resilient disc as its reference. The piezo sensors each produce a signal caused by the initial lateral glass movement connected to its first portion in relationship to its reference mass attached to its second portion. The initial motion is stored in the flexing of the piezo&#39;s resilient disc relative to its suspended reference mass and provides a reciprocating rate established by the mass and the flexing of the resilient piezo disc. The reciprocating rate is designed to further differentiate from other glass pane movements that may occur. 
         [0036]    An object at rest tends to remain at rest, and an object in motion tends to remain in motion (in a straight line). This is also known as the law of inertia. A change in state (rest, or motion) is called acceleration a, which is proportional to the net force F net  applied to the An object at rest tends to remain at rest, and an object in motion tends to remain in motion (in a straight line). This is also known as the law of inertia. A change in state (rest, or motion) is called acceleration a, which is proportional to the net force F net  applied to the object from outside: F net =m a. The proportionality “constant” m is what physicists call mass. For every action (a force applied to an object from the outside) there is always an equal-and-opposite reaction (the object pushes back on whatever pushed on it). 
         [0037]    Newton&#39;s Second Law essentially defines mass: it is the numerical size of an object&#39;s inertia; that intrinsic property of matter which makes it resist to being accelerated. The more mass an object has, the less acceleration it will have when pushed or pulled by a given size of force. The amount of mass is a measure also of the quantity of matter that makes up an object. The more mass (more matter) in an object, the harder it is to get it moving and the harder it is to stop it once it is moving. The translational inertia is just another name for mass. We can define translational inertia, m, as follows: translational inertia, m, is a measure of an object to a change in its motion. 
         [0038]    Referring to  FIG. 4A  showing the predetermined typical waveform  74  from a sensor when a tap occurs within about two or three inches from its suspended inertia mass. The waveform begins at the zero reference point  76  and goes above the threshold level  78  for a predetermined time indicated by arrows  80 . The returning of the inertia mass by its resilient support begins the oscillation to develop into sinusoidal wave shapes which continue (not shown) during the initial rearward movement of the glass pane when lightly tapped. Represented in  FIG. 4B  is the predetermined typical waveform  74  when the tap occurs about part way across from the sensor. The duration above threshold level  78  shown by arrows  80  is the same as in  FIG. 4A , but it is preceded by a sine wave  82  of lesser amplitude and duration. Represented in  FIG. 4C  is the predetermined typical waveform  74  when the tap occurs across at the opposite side of the glass pane. The preceding sine wave  84  is greater but never the predetermined duration of that produced by the resiliently suspended inertia mass. When a tap occurs from a distance from the sensor, the warping movement of the glass due in response to the tap travels faster and is of a shorter duration than the natural lateral movement of the edge mounted glass pane. A preferred embodiment of this invention employs a predetermined inertia duration that is shorter than the natural glass lateral movement, but longer than the glass pane warping durations. For example, the duration of the glass pane extending away from the tap and returning back to rest position (an alternation) may be about 7 milliseconds. A completed cycle which includes the returning fully toward the tap and back to point of rest would be 14 milliseconds. The warping alternations of the glass pane are mostly below 1.5 milliseconds. Using a resiliently suspended inertia movement with alternations of about 3.5 milliseconds and oriented to favor perpendicular light taps provides a consistent and unique signal for the purpose of determining the tap locations. 
         [0039]    Referring now to  FIG. 5  showing the sensor output signal  86  which starts at the point  88  before the start point  90  of the sensor output signal  92 . The threshold level  94  is used to determine the sensor outputs created by the inertia mass resisting the initial rearward thrust by the resilient support attached to the inner glass pane. The signal is valid when it remains above the threshold level  94  for the predetermined signal duration  96  of the inertia mass and its resilient support. The point  88  of the signal  86  crossing the threshold level  94  is the time chosen for the arrival of the light tap at that sensor. The sensor output signal  92  at point  90  would indicate the time of arrival at its sensor location. The time interval is shown by the arrows  97 . 
         [0040]    Referring now to  FIG. 6  wherein is drawn a signal waveform  98  that is more complex, containing both the desired predetermined inertia duration signal with an additional signal  100  superimposed. This is due to the glass pane&#39;s natural rearward movement having superimposed vibrations traveling across it while the predetermined signal is occurring from the suspended inertia mass. Even so, the duration of the signal above the threshold level  94  can distinguish the predetermined signal duration  96  of the inertia mass and its resilient support. 
         [0041]    Referring now to  FIG. 7  showing a tap occurring at product location  16   102  in proximity to its closest sensor B  104 , secondly to its next closest vertical sensor D  106 , and thirdly to its horizontal sensor A  108 . The first sensor to detect the genuine arrival signal starts a Y (vertically tracking) timer and an X (horizontally tracking) timer which are stopped by the vertical and horizontal sensor signals, respectively. The time intervals recorded as associated with the sensor locations are compared to stored acceptable ones in memory to determine the customer product selected. 
         [0042]    In  FIG. 8 , when a tap occurs at  13   110 , the sensor A  112  signal starts the Y and X timers, and are stopped by the sensor C  114  and B  116  signals, respectively. 
         [0043]    In  FIG. 9 , when a tap occurs at  24   118 , the sensor D  120  signal starts the Y and X timers, and are stopped by the sensor B  122  and C  124  signals, respectively. 
         [0044]    In  FIG. 10 , when a tap occurs at  31   126 , the sensor C  128  signal starts Y and X the timers, and are stopped by the sensor E  130  and D  132  signals, respectively. 
         [0045]    In  FIG. 11 , when a tap occurs at  47   134 , the sensor F  136  signal starts the Y and X timers, and are stopped by the sensor D  138  and E  140  signals, respectively. 
         [0046]    In  FIG. 12 , when a tap occurs at  50   142 , the sensor E  144  signal starts the Y and X timers, and are stopped by the sensor C  146  and F  148  signals, respectively. 
         [0047]    In  FIG. 13A  there is shown a side view of a resilient piezo disc  150  with its lower portion  152  attached to the mounting  154  which is attached to the glass pane  156  and its upper portion  158  pressed against by a projection  160  of the inertia weight  162 . The inertia weight  162  is suspended by the flexible support  164  which connects to an attachment  166  on the mounting  154 . The piezo disc  150  sensor leads  168  and  170  provide for connection at terminals  172  and  174  respectively. The front view of  FIG. 13A  is shown in  FIG. 13B  with corresponding parts having corresponding reference numbers. 
         [0048]    A preferred method in  FIG. 14A  shows a side view of a resilient piezo disc  176  is with its lower portion attached to a mounting  178  which is attached to the glass pane  180  and an inertia weight  182  attached to the upper portion  184  of the resilient piezo disc  176 . The sensor leads  186  and  188  connect to the resilient piezo disc  176  and its piezo element  190 , respectively. The front view of  FIG. 14A  is shown in  FIG. 14B  with corresponding parts having corresponding reference numbers. The dashed lines  192  with arrows  194  indicate the directions of movement of the resilient piezo disc  176  when it bends upon sufficient rearward movement of the mounting  178  and the tendency of the inertia weight  182  to resist movement and thereby flexing the resilient piezo disc  176  to the predetermined rate. The signal developed at the leads  186  and  188  are predominately at a predetermined rate and amplitude as controlled by the inertia weight and the resilient member. 
         [0049]    The chart of  FIG. 15  shows the relative location of sensors A  190 , B  192 , C  194 , D  196 , E  198 , capacitive, inductive, hall effect device or optical sensors can be utilized to sense a resiliently suspended inertia mass movement in respect to its attachment to the glass pane. The inertia mass can be suspended by a resilient member portion, or independently weighted against it. 
         [0050]    The same methods work very well when only one glass pane is used for viewing items to be selected by a user, such as in a non refrigerated vendor, and is anticipated. Also anticipated is the use of any of the taught methods and apparatus disclosed which would include the optional use of the prior art product entry methods and apparatus.