Abstract:
A transportation vending machine, and more generally a vending machine and cooling dispenser especially suited to environments in which there is limited space available. A serpentine path in the dispenser is formed from two-pieces of rotary-molded plastic having complimentary, serpentine surfaces which form a serpentine path when positioned against one another. Vending, without the need for selection buttons, is achieved by way of the cradles and an interlock system. Efficient cooling is provided by a thermoelectric cooling system that also consumes very little space.

Description:
FIELD OF THE INVENTION 
     The invention is directed toward a vending machine, and more particularly toward a vending machine for use in an environment with having reduced available space, such as would be found in a vehicle. 
     BACKGROUND OF THE INVENTION 
     Over thirty (30) years ago, it was known very generally to vend certain products in a vehicle. For example, the Rupert patent (U.S. Pat. No. 3,172,713), patented Mar. 9, 1965, was directed toward a vending machine apparatus to be used in conjunction with a vehicle seat structure. This invention was intended to vend small items such as cigarettes, candy, combs, or hand lotion, in a taxi cab. The vending machine was designed to fit into the backside of the front seat, so that it faced the passengers sitting in the rear seat. 
     Of the two (2) embodiments disclosed by the Rupert patent, the more space-efficient embodiment consisted of plural individual vending machines arranged side-by-side. To restock any one of these individual vending machines required its removal from the backside of the front seat. The less space-efficient embodiment took the form of a more conventional singular vending machine having a plurality of vended items. To restock the less space-efficient embodiment, it was necessary to open the entire face of the machine. 
     The Rupert patent did not disclose, nor did it envision, that it would be desirable to dispense, much less vend, refrigerated items in a moving vehicle. 
     In some countries, public transportation, especially inter-city transportation, takes place primarily on coach buses. Such buses seat approximately forty to sixty (40-60) people, and usually have a lavatory. The provision of a lavatory makes it possible to travel non-stop between cities, or to stop very infrequently. With few to no stops, there is little to no opportunity for a passenger on such a coach to obtain refreshments, such as soft drinks. 
     Typical vending machines are very large in size, which is impractical for the very limited space available in a coach bus. Also, the typical vending machine is cooled via a compressor driven by a motor. Such a cooling system consumes a great deal of energy, is very bulky, and generates a great deal of heat. Again, this is impractical for the typical coach bus, in terms of the volume of space consumed, the power consumed to run the compressor, and the large quantities of heat generated by the compressor. 
     It is not convenient to simply provide a cooler from which a passenger can withdraw a soft drink and pay an attendant. The profit margin for such a vending operation is small, so that the cost of paying an attendant would likely consume the profits from the sale of the beverage. The responsibilities of attendant and driver could be combined, but this presents a safety hazard if the driver is responsible for vending the soft drinks from the cooler. 
     SUMMARY OF THE INVENTION 
     A problem recognized by the Inventors is that there is no cooling dispenser suitable for use in a transportation environment such as a coach bus, much less a vending machine suited for such an environment. 
     Among other accomplishments, the invention solves the problem in the prior art by providing a cooling dispenser that is sufficiently small in size to be suitable for use on a coach bus. The invention can be of such small size because it incorporates a thermoelectric cooling system, and a vending system that does not require selection buttons. 
     The profit margin in the vending machine industry is very small, this being especially true for a vending operation in the environment of a coach bus or other vehicle. The invention improves the profitability of such an operation by providing a vending machine that is not only small in size, but is very economical to produce. This, in part, is made possible because the body of the vending machine is formed from two (2) molded plastic halves, each half having a complementarily-shaped serpentine surface. When the complimentarily-shaped serpentine surfaces are arranged against one another, a serpentine path is defined in between them. The stock of the vending machine is stored in one or more serpentine paths defined by the complimentarily-shaped serpentine surfaces. 
     It is an object of the invention to provide each of a dispenser and vending machine, preferably on a vehicle, having one or more two-part serpentine dispensing paths, the first of the two parts being complementarily-shaped with respect to the second of the two parts. 
     It is an object of the invention to provide each of a dispenser and vending machine, preferably on a vehicle, that is formed of molded plastic, preferably rotomolded plastic. 
     It is an object of the invention to provide each of a dispenser and vending machine, preferably on a vehicle, cooled by a thermoelectric device. 
     It is an object of the invention to provide each of a dispenser and vending machine, preferably on a vehicle, having cradle-terminated dispensing paths, wherein movement of the cradles is electromechanically controlled. 
     It is an object of the invention to provide a vending machine, preferably on a vehicle, that is operable without the provision of selection buttons. 
     It is an object of the invention to provide each of a dispenser and vending machine, preferably on a vehicle, having multiple openings in the face, some of the openings being operable to convey dispensed items to a user/customer, and at least one other opening being operable to permit a stock of the dispenser and vending machine, respectively. 
     It is an object of the invention to provide each of a dispenser and vending machine, preferably on a vehicle, having a power quality circuit to interrupt power to a cooling system if power supplied by the vehicle is of unacceptable quality. 
     It is an object of the invention to provide each of a dispenser and vending machine, preferably on a vehicle, having debounced sensor circuitry to filter out spurious signals caused by vibration of the substrate to which the dispenser and vending machine are mounted, e.g. a vehicle. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus do not limit the present invention, and wherein: 
     FIG. 1 is a three-quarter perspective view of a transportation vending machine according to the invention; 
     FIG. 2 is a view of the embodiment of FIG. 1 located within the likely environment of a coach bus; 
     FIG. 3 is an exploded view of the embodiment of FIG. 1; 
     FIG. 4 is a three-quarter, cut-away view of the embodiment vending machine of FIG. 1; 
     FIG. 5 is a more detailed view of the cradles and a portion of the cooling system of the embodiment of FIG. 1 ; 
     FIG. 6 is a cross-sectional view taken along view lines VI-VI′ of FIG. 5; 
     FIG. 7 is a cross-sectional view taken along view line VII-VII′ of FIG. 5; 
     FIG. 8 is a more detailed view of an aspect of the cradle depicted in FIG. 7; 
     FIGS. 9A,  9 B and  9 C are a flowchart representing some of the processing performed by the vending machine according to the invention; and 
     FIG. 10 is a perspective view of an embodiment technique for biasing a cradle to a closed position, according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 depicts a transportation vending machine  100  having a front part  102 , a rear part  104 , a door  106 , and cradles  112 . A coin mechanism and/or debit card device  110  is located in the front part  102  and access thereto is found via an aperture  108  in the door  106 . The front door  106  pivots about an axis of rotation corresponding to the dashed circle  116 . The cradles  112  pivot (about an axis of rotation  316  (of FIG. 3) that is parallel to the axis  116 ) so as to convey a dispensed item, such as a container, e.g., of a soft drink. Mechanically controlled cradle technology is known, as in U.S. Pat. No. 4,576,272 to Morgan, Jr. et al., patented Mar. 18, 1986, U.S. Pat. No. 4,676,074 to Morgan, Jr. et al., patented Jun. 30, 1987, and U.S. Pat. No. 5,247,798 to Collard, Jr. (the Collard patent) the entire contents of each of which are hereby incorporated by reference. 
     FIG. 2 depicts the transportation vending machine  100  in a likely environment, a coach bus  200 . The coach bus  200  has seats  204  on either side of an aisle  202 . At the rear of the bus  200 , after the last row of seats  204 , there is a small shelf  206  adjacent to a lavatory door  208 . The transportation vending machine  100 , according to the invention, is small enough to fit on the shelf  206  without interfering with the motion of the door  208  to the lavatory. 
     FIG. 3 is an exploded view of the transportation vending machine  100  of FIG.  1 . FIG. 3 depicts each of the front part  102 , the back part  104 , the door  106 , and the cradles  112  in more detail. Again, the axis of rotation for the door  106  is denoted by item  116 . Also, the door  106  is depicted as having a lock mechanism  302  and an aperture  304 , within the recess  108 , corresponding to the coin mechanism and/or debit card device  110 . An axis of rotation  316  for the cradles  112  is depicted. 
     Apertures  306  are depicted in part  102  where the coin mechanism and/or debit card device  110  will be inserted. Also, apertures  308  are depicted where containers  114  are inserted. Apertures  310  are provided through which an operator can gain access to the serpentine paths and correct jams. The axis of rotation  316  for the cradles  112  is also correspondingly depicted relative to the front part  102  in apertures  314 . 
     The back part  104  is depicted as having serpentine surfaces  320 . Alongside the serpentine surfaces  320  are formed serpentine rails  318  that are perpendicular to the serpentine surfaces  320 . The front part  102  has a set of serpentine surfaces (not depicted in FIG. 3) corresponding to the serpentine surfaces  320  as well as a set of serpentine ridges (not depicted in FIG. 3) corresponding to the serpentine ridges  318 . When the front part  102  and back part  104  are positioned against each other, the serpentine surfaces and serpentine ridges together define a corresponding number of serpentine paths through which flow the containers  114 . The beginning of the serpentine paths corresponds to the apertures  308 . The end of the serpentine paths correspond to the cradles  112 . 
     Near the end of the serpentine paths is a preferably planar surface  322  against which is formed a portion of the cooling system, which will be described in more detail in regard to FIG.  5 . The substantially planar surface  322  has apertures  325  and projections  324 . The back part  104  has a front leg formation  326  and rear leg formations  328  (one of which is shown). 
     FIG. 4 is a three-quarter, perspective, cut-away view of the embodiment of FIG.  1 . FIG. 4 again depicts the serpentine surfaces  320  and the serpentine ridges  318  of the back part  104 . Corresponding serpentine surfaces  402  and serpentine ridges  404  on the front part  102  are depicted as being complimentarily-shaped relative to the services  320  and ridges  318  of the back part  104 . Again, when the back part  104  is positioned against the front part  102 , the complimentarily-shaped surfaces  320  and  402 , together with the complimentarily-shaped ridges  318  and  404  together define a plurality of serpentine paths. 
     When the serpentine ridges  404  on the front part  102  are positioned against the serpentine ridges  318  on the back part  104 , the ridges  404  preferably engage the ridges  318  to form, in effect, a two-part serpentine conduit. Fans  406  and  408  are depicted in FIG. 4 as being located at the bottoms of the conduits, respectively. The fans  406  and  408  are controlled by a controller  616  (to be discussed below) to blow air in preferably opposite directions. Where the ridges  404  engage with the ridges  318 , a poor seal is made. As a result, the air forced into the conduit can escape along the entire length of the conduit. However, the primary way in which the air is moved in not within the conduit. Rather, the air is simply agitated within the cavity of the transportation vending machine. The use of two or more fans is preferred but optional. 
     FIG. 5 depicts the cradles and a portion of the cooling system of the embodiment of FIG. 1 in more detail. The bottom of the serpentine paths is formed by a cooling plate  502  which can be flat, but preferably has a rippled surface  503 , that lies on the planar surface  322 . The radius of curvature of the ripples in the surface  503  corresponds to the radius of curvature of the containers  114  so that there is a relatively large amount of surface contact between the container  114  and the rippled surface  503 , e.g., 20% of the circumference of the container  114 , so as to promote cooling via conduction. However, the ripples are not so large as to significantly impede the flow of containers  114  through the serpentine paths toward the cradles  112 . 
     The end of the serpentine paths correspond to tongues  504  of the cooling plate  502 . The tongues  504  also have a radius of curvature corresponding to the radius of curvature of the containers  114 . An even greater amount of surface contact exists between the container and the tongues  504  than between the ripples in the surface  503  and the containers  114 . The tongues  504  terminate the rolling of the containers  114  down the serpentine path. 
     On either side of the tongues  504  are correspondingly curved ridges (or shoulders)  506  which, in effect, extend the curved surface defined by the tongues  504 . However, the curved ridges  506  are parts of the cradles  112 . When a customer grabs a handle  508  of the cradles  112  and rotates the cradles about the axis of rotation  316  (along which lies a pivot pin  510 ), the ridges  506  lift the container  114  off the tongue  504  and move it to a location outside the vending machine  100  where a customer can grasp the container  114 . 
     The cradles  112  can be weighted so as to return to a closed position under only the force of gravity. Alternatively, the cradles  112  could be biased to return to the closed position, e.g., with a spring. An example of a spring to bias the cradle to the closed position is depicted in the side perspective view of FIG.  10 . In FIG. 10, a cradle  112  is biased by a tension spring  1002 . The tension spring  1002  can be formed from a flat piece of plastic or metal rolled into a coil. A bail  1004  passes through the center of the spring  1002  and is attached to the back part  104  of the vending machine. The exposed end  1006  of the coil  1002  is attached to the cradle  112 . As the cradle  112  is rotated, the coil  1002  unrolls. The effect is to produce a substantially constant amount of force biasing the cradle  112  to the closed position. 
     In FIG. 5, the gaps between each tongue  504  and the corresponding curved ridges  506  are asymmetric. In FIG. 5, the right hand gap  512  is depicted as being larger than the left hand gap  513 . The larger size of the right hand gaps  512  permit a sensor  516 , preferably a mechanical switch having a movable arm  517 , to be positioned between the tongue  504  and the right hand curved ridge  506 . The switch  516  is located so that when a can is resting in the tongue  504 , the moveable arm  17  is depressed and the state of the switch is closed. When the cradle is rotated to withdraw a container, or when the column is empty, the switch  516  is biased so that the moveable arm  17  moves upward so that the switch  516  takes on the open state. 
     In FIG. 5, only one switch  516  has been depicted for simplicity. A signal line is depicted as going from the switch  516  to the controller  616  (to be discussed in more detail below). 
     FIG. 5 also depicts a solenoid  518  having a moveable pin  520  that engages within a triangular or sector-shaped recess  522  on one interior side of the cradle  112 . Again for simplicity, only one solenoid  518  and recess  520  are depicted. A signal from the controller  616  is depicted as coming into the solenoid  518 . When not energized, the pin  520  of the solenoid is extended so as to engage the recess  522 . When the pin  520  is engaged in the recess  522 , the cradle can be rocked a slight amount sufficient to lift the container far enough away from the tongue  504  so as to permit the switch  516  to take on the open state. However, the size of the triangular recess  522  is selected so that the cradle cannot be rotated far enough to permit a container to be withdrawn. When energized, the pin  520  of the solenoid  518  withdraws so as to no longer engage the recess  522 , which permits the cradle  112  to be rotated enough to withdraw a container. 
     The solenoid  518  is preferably mounted on the back part  104  (see FIG.  7 ). The triangular recess  22  is preferably oriented so that the apex points toward the front of the vending machine while the base is pointed toward the back part  104 . When the vending machine is disassembled, the front part  102  is separated from the back part  104 . Such disassembly usually takes place with the power off. When the power is off, the solenoid  520  returns to the default position in which the pin  520  is fully extended. Having the base of the recess oriented toward the back part  104  permits the fully extend pin  520  to be slid away from the cradle  112 . 
     Other shapes for the recess into which the pin  520  engages could be chosen. However, such a shape should have an opening like that of the triangular recess  522  in order to permit the front part  102  to be separated from the back part  104  even when the pin  520  is fully extended. An additional advantage of the choice and orientation of the triangular recess  522  is that the front part  102  and the back part  104  can be coarsely aligned and yet successfully slid together. In other words, the manner in which the sides of the triangular recess  522  taper toward the apex act to guide the pins  520  as the front part  102  is positioned against the back part  104 . 
     FIG. 6 is a cross-section of FIG. 5 taken along the view lines VI-VI′. FIG. 6 depicts in more detail the cooling system of the transportation vending machine  100 , which can be a compressor system, but is preferably a thermoelectric system. In FIG. 6, the cooling plate  502  is depicted as having a contact/bridge  604  that extends through one of the apertures  325  of FIG.  3 . Two apertures have been depicted in FIG.  3 . The desired number depends upon the cooling needs of a particular situation. The bridge  604  of the cooling plate  502  is a thermal conduit in contact with a thermoelectric device  606 . The thermoelectric device  606  functions according to the Peltier Effect as a heat pump that draws heat energy from one surface of the device to the opposite surface. To reiterate, thermoelectric cooling devices are known, reliable cooling devices that function without the need of refrigerants or compressors. See, for example, U.S. Pat. No. 5,469,708 to Harrison et al., patented Nov. 28, 1995, the entire contents of which are hereby incorporated by reference. The foregoing incorporation by reference of the Collard patent is reiterated here also for, among other reasons, its disclosure of thermoelectric cooling technology. Preferably two thermoelectric devices are used, however only one is depicted in FIG. 6 for simplicity. 
     The thermoelectric device  606  is also in thermal contact with a heat sink  608  having fins  610  formed opposite to the side that is in contact with the thermoelectric device  606 . An optional but preferred layer of insulation is depicted between the cooling plate  502  and the heat sink  608 . Optionally, and preferably, the layer of insulation  612  also protects the thermoelectric device  606  from condensation. A fan  614  is optionally, and preferably, provided for forcing air past the fins  610  of the heat sink  608 . Also optionally, a temperature sensor  620  is positioned on or near the heat sink and operatively connected to a controller  616  for selectively actuating the cooling fan  614 . 
     FIG. 6 also depicts the power quality monitoring circuitry  622  according to the invention. The vending machine according to the invention is intended to be used on a vehicle. The thermoelectric devices  606  and the fan  614  consume a significant amount of power. In a vehicle that is operating normally, the load represented by the thermoelectric devices  606  and the fan  614  does not present a problem. However, if the vehicle is malfunctioning, then this electrical load represented by the vending machine can be a problem. 
     A vending machine on a vehicle is a luxury, not a necessity. Hence, the power quality determination circuitry  622  is provided to for the purposes for shutting down the vending machine if the power supplied by the vehicle is too low. In addition, if the power supplied by the vehicle is too high, then the circuitry  622 , in conjunction with the controller  616 , can shut down the vending machine. 
     The circuitry  622  includes a first comparator  624  and a second comparator  626 . The comparator  624  receives a low reference voltage and the vehicle voltage. If the vehicle voltage drops below the low reference voltage, then the controller senses the change in output from the comparator  624 . The comparator  626  receives a high reference voltage and the vehicle voltage. If the vehicle voltage is greater than the high reference voltage, then the controller  616  senses the change in output of the comparator  626 . 
     The processing by the controller of the signals from the comparators  624  and  626  is debounced and exhibits hysterisis. It is debounced in the sense that the controller  616  samples these signals, e.g., every ten milliseconds. If the comparators  624  and  626  provide five consecutive samples indicating that the vehicle voltage is too low or too high, respectively, then the controller recognizes a true undervoltage or true overvoltage situation, respectively. Otherwise, the too low or too high indications are dismissed as transient. 
     If the controller  616  determines that the voltage is too low, then the controller shuts down the thermoelectric devices  606  and the fans  614 , disables the coin mechanism and controls the indicator on the vending machine to appear as though is off, as in step  908  of FIG. 9A, (discussed below). To exhibit hysterisis, the controller  616  will not restore power to the thermoelectric devices  606  and the fans  614 , reactivate the coin mechanism and reenergize the indicator for at least 30 seconds. A comparable hysterisis scenario is provided in the case where the controller senses a true overvoltage situation. 
     FIG. 7 depicts a cross-sectional view along the view lines VII-VII′ of FIG.  5 . It is noted that items not depicted in FIG. 5 (for simplicity) have been depicted in FIG. 7, such as the front and back parts  102  and  104 , and the door  106 . FIG. 7 depicts the serpentine path  700  created between the serpentine surfaces  320  and  402 , and the serpentine ridges  318  and  404 , when the parts  104  and  102 , respectively, are positioned against one another. An example of eighteen ( 18 ) containers  114  are depicted as capable of being stored in the serpentine path  700 . In FIG. 7, the closed position for the cradle  112  is depicted in full-lines, while an open position of the cradle  112  is depicted by dashed-lines denoted by item  706 . The cradle  112  includes a flange  710  formed so as to stop motion of the cradle  112  about a pivot pin  712  when the flange  710  comes into contact with a corner  714  of the front part  102 . A pivot pin  708  lying parallel to the axis of rotation  116  is depicted as attaching the door  106  to the front part  102 . 
     FIG. 8 depicts the interlock aspect of the cradle of FIG. 7 in more detail. In FIG. 8, the cradle  112  is in the closed position so that the moveable arm  517  of the switch  516  is also in the closed position. The solenoid  518  is shown as being positioned on a projection  802  of the back part  104 . 
     FIGS. 9A,  9 B and  9 C are a flow chart representing some of the processing performed by the controller  616 . Flow through the chart begins at step  902  and proceeds to the initialization step  904 . This can include checking the status of the coin mechanism, the thermoelectric device (TEDs) and determining the prices of the products being sold. For example, the controller can be provided with post-jumpers (not shown) or dual inline package (dip) switches (not shown), i.e., low cost non-volatile memory, the configuration of which can represent the price of the vended products. 
     From the initialization step  904 , flow proceeds to the decision step  906 , where it is determined whether the power being supplied to the vending machine is of acceptable quality (see FIG.  6  and associated description for further details). If the power is not of acceptable quality, flow proceeds to step  908 , where the thermoelectric devices and the fan are turned off, the coin mechanism is disabled and the indicator lights (not shown) on the vending machine are made to appear as though power to the machine is off. Flow proceeds from step  908  back to the decision step  906  to await the resumption of acceptable power quality. 
     If the power quality is acceptable, flow proceeds from step  906  to the decision step  910 , where it is determined whether any of the columns are sold out. If so, flow proceeds to step  912  where the respective sold out flags SOF 1 , SOF 2  and SOF 3  are set to true if necessary. Previously, during the initialization step  904 , these flags had all been set to false. Flow proceeds from step  912  to the decision step  914 , where it is determined whether all of the columns are sold out. If so, flow proceeds back to step  908 . If not all of the columns are sold out, then flow proceeds to step  915 , where the thermoelectric devices and the fan are turned on, the coin mechanism is enabled and the indicator lights (not shown) on the vending machine are made to appear as though power to the machine is on. From step  915 , flow proceeds to the decision step  916 . Back at step  910 , if it is determined that none of the columns are sold out, flow proceeds directly to step  915 . 
     It is noted that the determination at step  910  is debounced, i.e., the process is sufficiently sophisticated to filter out noise. For example, the controller  616  actually samples the state of the switches  516  every ten milliseconds, preferably sampling only one switch  516  at a time in a polling fashion. If the controller  616  receives five consecutive open state indications from a switch, then that switch is considered to truly be open. Similarly, if the controller  616  receives five consecutive closed state indications, then that switch is considered to be truly closed. On a vehicle, bumps in the road are transmitted through the suspension system to the contents and occupants of the vehicle. This transmitted noise may cause the cradles  112  to rotate enough to momentarily open the switches  516 , especially in view of the ability of the cradles  112  to rotate slightly when the moveable pins  520  are extended to engage the triangular recess  522 . 
     At the decision step  916 , it is determined whether a customer has deposited sufficient credit via the coin mechanism in order to dispense a product/container. If not, flow proceeds back to step  906 . If sufficient credit has been deposited, then flow proceeds to step  918  of FIG. 9B, where the controller  616  again polls the switches  516 . Flow proceeds from the polling step  918  to the decision step  920 , where it is determined whether any switch has been opened. If none of switches are open, then flow proceeds back to the polling step  918 . However, if at least one of the switches is open, flow proceeds from step  920  to the decision step  922 . 
     The determination at step  920  is a debounced determination for the purposes of filtering out road-vibration-induced false switch indications. Similar to the description above, e.g., a truly open switch is one for which the controller  616  receives five consecutive open state indications, while a truly close switch is one for which the controller  616  receives five consecutive closed state indications. 
     In the decision step  922 , it is determined whether switch number  1  is open. If not, flow proceeds to step  936  of FIG.  5 C. If switch number  1  is opened, then flow proceeds to the decision step  924 , where it is determined whether the sold out flag for serpentine column  1 , namely SOF 1 , has been set to the logical true state. If so, i.e., if the column which switch number  1  monitors is sold out, then flow proceeds to step  936  of FIG.  9 C. However, if SOF 1  is set to the logical false state, i.e., if the corresponding column is not sold out, then flow proceeds to step  926 , where the solenoid number  1  is energized, i.e., is set on, and the solenoids number  2  and  3  are set to the off state, which is the default state. 
     Flow proceeds from step  926  to step  928 , where a count down timer is set to 1.5 seconds and is started counting down. Flow proceeds from step  928  to the decision step  930 , where it is determined whether the timer has finished counting. If not, flow loops back to the step  930 . If so, flow proceeds to step  932  of FIG. 9C, where all of the solenoids are set to the off state. In other words, once a customer has deposited sufficient credit in the coin mechanism and has chosen one of the cradles, here cradle number  1 , then the controller  616  gives the customer 1.5 seconds in which to rotate the cradle far enough to withdraw the products/container. However, the timer will not start until the customer moves one of the cradles  112 . 
     Flow proceeds from step  932  to step  934 , where the credit is reset to zero. Flow proceeds from step  934  to step  906  of FIG.  9 A. As mentioned above, flow can proceed from steps  922  or step  924  to the decision step  936 , where it is determined whether switch number  2  is open. If not, flow proceeds to step  942 . However, if switch number  2  is open, then flow proceeds to the decision step  938 , where it is determined whether the sold out flag for the serpentine column corresponding to switch number  2 , i.e., SOF 2 , is set to the true state. If the second column is not sold out, then flow proceeds to step  940 , where the solenoid number  2  is set to the on state, i.e., solenoid  2  is energized, while the solenoid numbers  1  and  3  are set to the off state. Flow proceeds from step  940  to step  928  of FIG.  9 B. 
     As noted above, flow can proceed from steps  936  and  938  to the decision step  942 , where it is determined whether switch number  3  is open. If not, then flow proceeds to step  918  of FIG.  9 B. However, if switch number  3  is open, then flow proceeds to the decision step  944 , where it is determined whether the sold out flag, SOF 3 , for the serpentine column corresponding to the third switch is set to the true state. If so, i.e., if the serpentine column corresponding to the third switch is sold out, then flow proceeds again to step  918  of FIG.  9 B. However, if the third column is not sold out, then flow proceeds to step  946  where the solenoid number  3  is set to the on state, i.e., is energized, while the solenoid numbers  1  and  2  are set to the off state. Flow proceeds from step  946  to step  928  of FIG.  9 B. 
     The process of FIGS. 9A-9C ensures that only one product/container is dispensed for one purchase price. The time of 1.5 seconds was chosen to be short enough in duration to prevent a customer from withdrawing multiple products/containers. However, the time of 1.5 seconds is also long enough to protect a slippery-fingered customer from loosing his credit if the drawer slips out of his fingers after he first moves it. The time of 1.5 seconds could be either increased or decreased depending upon the environment in which the vending machine is intended to be located. 
     The process of FIGS. 9A-9C assume that the price of the product/containers in each of the three columns will be the same. However, the prices could be different. One of ordinary skill in the art would understand the minor modifications to the process of FIGS. 9A-9C that would be needed for such different pricing. 
     The location of the switches  516  has been chosen so that switch  516  serves a dual purpose. First, upon initialization, the switches  516  are indicative of whether any of the columns are sold out of product/containers. Second, after sufficient credit has been deposited by a customer, the switches  516  indicate whether the cradles  112  have been moved. Separate sensors could be provided to indicate the sold out status of a serpentine column and to indicate whether the cradle has been moved. However, in the very cost sensitive vending machine industry, the cost savings achieved by the dual functions fulfilled by careful location of each switch  516  is an advantage. 
     The controller  616  could be implemented with numerous commercially available processors. However, in the very cost sensitive vending machine industry, it is preferable to choose a processor that is low in cost. An example of a suitable processor is the model number PIC16C57 processor from the PICmicro™ family of microcontrollers marketed by Microchip Technology Inc. 
     If the cradle  112  is open after the timer has timed out, causing the associated solenoid to be deenergized, the cradle  112  can be returned to the closed position. The solenoid  518  and the cradle  112  are arranged as a one-way catch or ratchet so that the cradle can always return to the closed position regardless of whether the solenoid is energized or not, i.e., whether the vending machine defaults to a locked configuration. 
     The PIC16C57 processor is an EPROM/RAM-based 8 bits CMOS programmable micro-controller. The controller  616  could also be implemented as a programmable logic array (PLA). However, because the vending machine industry is very cost sensitive, the PLA implementation is currently less preferred than the use of the PIC16C57 microcontroller. 
     To provide a robust design at a minimum cost to form the parts  102  and  104  of the transportation vending machine  100  according to the invention, the parts  102  and  104  are preferably formed of molded plastic, and more preferably formed of rotational-molded (or rotomolded) plastic. Rotomolding of plastic is a known technique for making large plastic components that are hollow inside. The voids (not depicted) inside the parts  102  and  104  can be filled with a thermally insulating material. Similarly, the door  106  can be formed by injection-molding, or more preferably by, rotomolding, and preferably will also be filled with a thermally insulating material. Filling the voids of the parts  102 ,  104 , and  106  with the thermally insulating material helps preserve the containers  114  in a refrigerated state. Alternatively, the insulating material in the form of sheet can be provided on the inside surfaces of the parts  102 ,  104 , and  106 . 
     The door  106  is arranged on the front surface of the front part  102  so that restocking can take place by simply opening the door sufficiently to gain access to the apertures  308 , or to the apertures  310  in the event of a jam in the serpentine path  700 . It is to be recalled that prior art vending machines required the entire front face of the vending machine to be opened. Here, the door  106  can be operated without interfering with the cradles  112 . Moreover, the door  106  can be fully opened in a smaller volume than could the entire face of the machine, which is especially useful in, e.g., the cramped confines of a vehicle. 
     The thermoelectric cooling system is very efficient at maintaining the containers at a predetermined temperature, but is not especially efficient at cooling the containers from room-temperature down to a desired serving temperature. Thus, it is preferable that the containers  114  be pre-chilled prior to being inserted into the serpentine paths  700  via the apertures  308 . 
     If the containers  114  remain in contact with the rippled surface  503  of the cooling plate  502  for an extended period of time, the thermoelectric cooling system is capable of freezing those containers  114 . Thus, the fans  902  and  904  are provided to circulate air within the interior of the vending machine  100 . This has the effect of retarding the freezing of the containers  114  that are in contact with the rippled surface  503  of the cooling plate  502 , while at the same time, providing cooled air to the container  114  in the upper portion of the serpentine paths  700 . Again, the cooling process can also be controlled (optionally but preferably) via the selective actuation of the cooling fan  614  in response to the sensor  620  sensing a predetermined temperature on the heat sink  608 . Similarly, if the temperature sensed by the sensor  620  drops below another predetermined temperature, the controller  616  can turn off the fan  614 . 
     The invention has been described in terms of a vending machine (or vender). However, many aspects of the vending machine are applicable to a cooling dispenser (or cooler). For example, it is possible to provide the two-piece molded serpentine-path-based dispenser in connection with a cooler rather than a vending system. Similarly, the thermoelectric cooling system can be provided for a dispenser having cradles without the provision of the associated vending machine system that includes the interlock controller. The example of three serpentine columns has been presented because, for dispensing soft drink containers, this fits well within the space typically available on a coach bus. However, any number of serpentine columns can be implemented. 
     While the invention is especially suited to a cooling dispenser or vending machine that is to be used on a vehicle such as a coach bus, plane, train, or limousine, it is also suitable for a non-transportation environment such as a small kitchen or break room in an office or a recreation room or bar in a home. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art were intended to be included within the scope of the following claims.