Patent Publication Number: US-2013228590-A1

Title: Sled driven queued item dispenser

Description:
PRIOR APPLICATION 
     This is a continuation of U.S. patent application Ser. No. 12/913,740 filed 2010 Oct. 27 which is a continuation-in-part of International Patent Application No. PCT/US2010/032618, filed 2010 Apr. 27 designating the United States, which is a continuation-in-part of U.S. Provisional Patent Application Ser. No. 61/234,606, filed 2009 Aug. 17, and a continuation-in-part of U.S. Provisional Patent Application Ser. No. 61/173,575, filed 2009 Apr. 28. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to mechanisms for propelling a queue of articles along a guide track. More specifically, the invention relates to dispensing mechanisms used in machines for automatically vending articles or substances packaged in symmetrical containers such as the ones commonly used in connection with individual servings of coffee, tea, sugar, shampoo, toothpaste, as well as medicines and cosmetics. 
     BACKGROUND OF THE INVENTION 
     In the coffee service industry, individual doses of coffee, tea or chocolate are often offered in small containers, packs, sachets or packets that are configured to be readily inserted in a brewing machine. Such packets sold under the brand name FLAVIA® are commercially available from the Mars Incorporated of McLean, Va. and are generally described in U.S. Pat. No. 7,258,061, Campbell et al., incorporated herein by reference. 
     Referring now to  FIGS. 1 and 2  there is shown a number of beverage container items or packaged articles of the prior art in the form of coffee packets  1  arranged in a queue  2  and slidingly held on a support track  3  for dispensing. Each of the packets  1  has a pouch portion  5  for holding ground coffee formed by a pair of foil-lined plastic sheets bonded along a periphery and is slightly pliable. Each packet uses a substantially rigid plastic, carrier structure  4  secured to the top of the packet which allows the packet to dangle below the track  3  while being slidingly secured to it. 
     Referring now to  FIG. 2 , the carrier structure, or simply carrier  4  has a substantially cylindrical shank  20  of given diameter extending upward from the middle of the top edge  21  of the packet  1  on a substantially vertical axis  22 . The top end of the shank widens to form a head  23  so that it has an undersurface  24  which slidingly bears against the upper surfaces of the track. The entire weight of the item is thus supported by the head while engaging the track. From the top, the head has a generally slightly elongated octagonal shape so that there are angled surfaces  25  which transition between the substantially flat front edge  26  of the head to the side edges  27  of the head, and from the side edges to the substantially flat back edge  28 . The top of the head also has a peripheral upwardly extending wall  18  surrounding an inner indentation  29 . In the middle of the indentation is a raised circular frangible nipple  17  providing access to the inside of the pouch. 
     An array of supports can be arranged in a housing and is usually placed next to the brewing machines for the convenience of employees and customers. In most cases, this type of beverage service is provided and paid for by the employer. 
     The system is subject to abuses, however. Unscrupulous employees may grab handfuls of containers for use at home. Unsupervised persons, such as maintenance and janitorial crews who frequent the premises during off hours may also be tempted to help themselves to undue quantities of goods. 
     U.S. Patent Application Publication No. US-2009-0057333, Simson et al., incorporated herein by reference, discloses a tamper resistant vending device having a detachable magazine containing an array of separately activatable cartridges for dispensing one of several queues of items in independent cartridges using a pneumatic driving means. Such a system is not readily adaptable to dispensing the carrier topped packets described above. 
     In many vending contexts, maintaining a large number of customer choices is preferred. For example, a single vending machine may seek to provide a variety of coffee selections. Depending on the vagaries of consumer habits, some varieties may run out quicker than others prompting restocking Restocking of a dispenser located at a customer site often requires the time-consuming task of manually loading of the packets onto their supports from the front of the support. It is generally preferred that restocking frequency of a machine is kept to a minimum because of the cost associated with an operator visit. 
     The items can be supplied in a queue on a storage or transportation rail oriented at an acute angle with respect to the major axis of the rail so that the width of the queue is reduced to facilitate greater packing density of a number of storage or transportation rails. 
     There is a need to find a convenient solution to the controlled presentation and dispensing of small packaged articles. 
     SUMMARY OF THE INVENTION 
     The invention provides a simpler, less expensive, and/or more efficient way to store, transport, restock, display and/or dispense small packaged items under some form of paid or verifiable accounting to authorized or paying customers. 
     One of the main advantages of some embodiments of the invention is the ability of loading a batch of products onto the dispensing mechanism from the back rather than from the front of the vending machine. This feature also allows the rapid transfer of a batch of products mounted on a temporary storage and transportation rail directly into the vending machine by way of a convenient coupler. 
     In some embodiments there is provided a device for selectively dispensing a plurality of items, wherein each of said items has a carrier uniformly shaped and dimensioned with respect to others of said items, said device comprises: at least one elongated track for carrying a queue of said items; and, a sled slidingly mounted to said track for pushing a last one of said items in said queue forward during a dispensing action for dispensing a front one of said items in said queue. 
     In some embodiments said at least one elongated track comprises: an elongated channel having a frontal dispensing aperture, a back loading aperture, and a cross-section commensurate with a cross-sectional dimension of said carrier; and, a ratcheting mechanism alternately allowing dispensing of a first one of said items through said frontal aperture and holding back a second one of said items next in line behind said first one; wherein said ratcheting mechanism comprises: a first rack slidingly and reciprocatingly secured with respect to said track, said first rack having a drive motion and a reset motion; said first rack carrying a plurality of spaced apart prominences; a drive sled arranged to successively engage at least one of said prominences and drive forward said carriers while said first rack moves in said drive motion; and, a friction structure retaining said carriers from moving backward while said first rack moves in said reset motion. 
     In some embodiments said sled comprises a retractable pawl having a pawl tip contacting said prominences. 
     In some embodiments each of said prominences are substantially sawtooth shaped. 
     In some embodiments said friction structure comprises a brake mechanism associated with said sled to successively immobilize said sled while said rack moves in a reset stroke. 
     In some embodiments said brake mechanism comprises a movable wedging post which wedges more tightly between said sled and said track during slight rearward movement of said sled with respect to said track, and wedges less tightly during forward movement of said sled with respect to said track. 
     In some embodiments the device further comprises a weighted swing arm hingedly connected to said sled, wherein rearward motion of said swing arm disengages said pawl tip from said drive rack and causes de-wedging of said post. 
     In some embodiments the device further comprises: a plurality of said tracks are assembled into a magazine; a base unit comprising a cradle shaped and dimensioned to lockingly nest a portion of said magazine; and means for selectively activating a drive stroke in one of said plurality of tracks. 
     In some embodiments said cradle provides a fulcrum surface oriented to bear against said magazine causing angular movement of said magazine. 
     In some embodiments said magazine is detachable from said base unit. 
     In some embodiments aid means for activating comprise a reciprocating motor driven bolt oriented to mechanically engage said rack and thereby cause said drive stroke. 
     In some embodiments the device further comprises: a motor having a rotatable shaft; a linkage between said shaft and said bolt, said linkage comprising: a substantially circular disk rotatively held within a bearing, said disk having an axis of rotation; a pin radially spaced apart from said axis; and, said bolt having an oblong slot slidingly and rotatively engaged by said pin. 
     In some embodiments said magazine comprises a modular arrangement of spaced apart plates and crosspieces mechanically securing said tracks within an array of cartridges, wherein an additional one of said plates adds either a row or column to said array. 
     In some embodiments said device further comprises: said at least one track having a C-shaped cross section, parallel side walls and inwardly extending support flanges; wherein said carrier includes a head engaged into said track and a shank projecting from said head between said flanges; wherein said first rack is a drive rack inserted into said track and having a plurality of substantially sawtooth-shaped prominences shaped and positioned to capture and propel a sled engaged into said track behind a last one of said items when said drive rack is moved axially in a first axial direction, and to course over said sled when said drive rack is moved axially in a second axial direction; wherein said friction structure comprises a braking mechanism associated with said sled; said braking mechanism resisting rearward motion of said sled when said rack is moved axially in said second axial direction; and a mechanism for alternately moving said drive rack in said directions. 
     In some embodiments the device further comprises: said items being mounted on a loading rail; a coupler mounted to said back loading aperture, said coupler having a first interface for releasably mating to an end of said loading rail, said coupler being shaped dimensioned and located to form a open interfacing channel between said loading rail and said elongated channel. 
     In some embodiments said ratcheting mechanism comprises: a spring resiliently biasing said drive rack toward one of said directions; and an actuator successively pulsing said rod against said spring. 
     In some embodiments said sled comprises: a body having an upper section including a pair of extensions extending laterally from opposite sides of said section sized to slidingly engage said track; a transverse brake post having first and second ends extending laterally from said body to contact an undersurface of said track; said brake post being slidingly and rotatively secured to said body; and, said body being shaped and dimensioned to have a transverse oblong foramen defining a range of motion for said post; said range of motion including a wedged position and a de-wedged. 
     In some embodiments said foramen is oval shaped. 
     The content of the original claims is incorporated herein by reference as summarizing features in one or more exemplary embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a diagrammatic perspective view of a queue of beverage item packets of the prior art each having a top carrier structure slidingly mounted to a dispensing support. 
         FIG. 2  is a close up diagrammatic perspective view of the carrier structure of the packet of  FIG. 1 . 
         FIG. 3  is a diagrammatic perspective view of beverage item dispensing machine according to an exemplary embodiment of the invention. 
         FIG. 4  is a diagrammatic left side view of the machine with the magazine cover closed. 
         FIG. 5  is a diagrammatic front elevational and partially exploded view of an array of cartridges forming a magazine. 
         FIG. 6  is a diagrammatic perspective view of a motor having an eccentric pin. 
         FIG. 7  is a diagrammatic front view of the actuation bolt in a retracted position. 
         FIG. 8  is a diagrammatic front view of the actuation bolt in a extended position. 
         FIG. 9  is an exploded perspective view of an embodiment of packet dispensing ratcheting mechanism. 
         FIG. 10  is a partial cross-sectional bottom plan view of the head of a carrier in the ratcheting mechanism. 
         FIG. 11  is a cross-sectional view of the assembled mechanism. 
         FIG. 12  is a diagrammatic top view of a queue of carriers being pushed forward by a drive stroke where the locking rack is pushed aside to an unlocking first crosswise position. 
         FIG. 13  is a diagrammatic top view of a queue of carriers held by the locking rack friction structure in the locking second crosswise position during a reset stroke. 
         FIG. 14  is a diagrammatic top view of a queue of carriers being pushed forward by the drive rack in a first transversal position during a drive stroke. 
         FIG. 15  is a diagrammatic top view of a queue of carriers where the drive rack has moved sideways to a second tranversal position during a reset stroke. 
         FIG. 16  is a diagrammatic top view of the support plate, the locking rack, the drive rack and the push rod. 
         FIG. 17  is a diagrammatic top view of an alternate embodiment of the support plate, the locking rack, the drive rack and the push rod. 
         FIG. 18  is a diagrammatic perspective view of an alternate embodiment of a rack transversal position biasing spring mechanism. 
         FIG. 19  is a diagrammatic cross-sectional view of the rack transversal position biasing spring mechanism in an uncompressed state. 
         FIG. 20  is a diagrammatic cross-sectional view of the rack transversal position biasing spring mechanism in a compressed state. 
         FIG. 21  is a diagrammatic bottom perspective view of an alternate queued item dispensing mechanism having a sliding, self-braking drive sled. 
         FIG. 22  is a diagrammatic cross-sectional end view of the track, drive rack and item head. 
         FIG. 23  is a diagrammatic perspective view of the sliding, self-braking drive sled. 
         FIG. 24  is a diagrammatic cross-sectional end view of the track, drive rack and sled. 
         FIG. 25  is a diagrammatic cross-sectional side view of the self-braking drive sled slidingly mounted on a track and being driven by a crenelated drive rack. 
     
    
    
     DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     Referring now to the drawing, there is shown in  FIGS. 3-4  a vending machine  31  particularly adapted to dispense a number of different items packaged in lightweight packets  32  made of pliable martial such as paper or plastic. In this particular embodiment, the machine is intended to dispense individual servings of coffee or other beverages such as FLAVIA® brand coffee, tea and chocolate packs commercially available from the Mars Incorporated of McLean, Va. The machine accommodates a removable magazine  33  that groups an array of cartridges  34  each potentially holding a different type of packeted product  32  in a queue dangling from a track  30 . 
     The base  35  of the machine forms a cradle  50  which is adapted to closely nest the magazine  33  in alignment with a rear plate  48  carrying a commensurate array of linkages  47  between each track and a dedicated actuating motor  49 . A fulcrum structure  51  is formed onto an upper surface of the cradle in the base unit  35  to bear against the undersurface  52  of the magazine. The magazine is installed by inserting its back end at a downward angle into a recess formed in front of the rear plate  48  so that a series of projections  53  extending from the upper surface near the rear of the magazine pass underneath the upper ledge  54  of the base unit overhanging the recess. The magazine is then rocked forward on the fulcrum in order to lower the front end and raise the back end, thereby engaging the projections into corresponding holes in the upper ledge. This causes the magazine to closely align itself with the rear plate so that the motor linkages are properly engaged. When the front of the magazine snaps down the magazine is thus locked into place and the cover  44  can be closed. Once the magazine  2  is installed on the machine and the cover has been shut and locked, the magazine cannot be removed. 
     The base  35  can also house mechanisms that further control and protect the dispensing of the goods out of the cartridges. A dispensing pocket  42  for the goods is provided in the frontal portion of the base. The pocket is accessible by pushing a flap door  43 . The front of the machine is sealed by a cover  44  whose transparent face permits viewing of the first item in each cartridge. 
     An electronic control unit  36  provides an interface with the user of the machine by way of an alpha-numeric readout  37 , an electronic data media reader  38 , an alpha-numeric keypad  39 , and a cash acceptor  40 . 
     Each tubular quadrangular cartridge  34  has a substantially rectangular cross-section which loosely contains the symmetrical items  32  to be dispensed which are lined up one-behind-the-other in a queue. Each item has a carrier projecting vertically from the item which slidingly engages the ratcheting track  30  extending longitudinally along the ceiling of the cartridge, which will be described in greater detail below. 
     Referring now to  FIG. 5 , the array of cartridges  34  are formed by a number vertically oriented panels  60 , 61  which interlock with each of the tracks  30 . A pair of side panels  60  having smooth outer surfaces  62  form the side walls of the magazine  33 . A number of internal panels  61  are spaced apart equidistantly to define the lateral extent of each cartridge. Crosspieces  64 , 65  interlock with the tracks to define the vertical extent of each cartridge. Along the bottom of the magazine, spacers  66  are used to bond crosspieces to one another in place of unneeded tracks. Various tongue-in-groove, or other commonly used interlocking structures can be used on the parts of the panels, crosspieces, spacers and tracks which bond to one another in order to ruggedize the magazine. Each panel can be easily assembled from rigid durable sheets of plastic or metal interlocked with the rigid durable plastic or metal crosspieces. Those skilled in the art will readily appreciate the modular nature of the panel arrangement and its expandability to form additional rows or columns of cartridges. 
     Actuation of the ratcheting mechanism comprises a drive stoke, followed by a reset stoke. Although a solenoid-type actuation device can be used, the preferred actuation device uses a rotary motor. Referring now to  FIGS. 6-8 , there is shown a motor  49  for actuating a tracked dispenser associated with a particular cartridge. The motor has a turning shaft  67  connected to a disk  68  which has an axially extending pin  70  located a radial distance from the rotational axis  69  of the disk and this can be said to be a radially eccentric pin. The pin slidingly engages an oblong oval slot  71  in a bolt  72  slidingly mounted to a guideway  73 . The bolt has an engagement prong  74  oriented to contact the rear of the track and activate its ratcheting mechanism described below. 
       FIG. 7  shows the position of the bolt  72  after a reset stoke where the bolt is essentially in its fully retracted position. 
       FIG. 8  shows that during a drive stroke, after one half turn of the motor shaft, the pin  70  has coursed to the top of the slot  71  and back down again, and caused the bolt  72  to slide forward in its guideway  73 , and cause the engagement prong  74  to actuate the track ratcheting mechanism drive stroke which causes the queue of packets to move longitudinally forward ejecting the frontmost packet. In this way, a less powerful and hence inexpensive and lightweight rotary electrical motor can be used. In addition, the sliding bolt linkage can have a narrow cross section which allows it to operate in the restricted confines of the base unit. In addition, this type of linkage allows for a high degree of mechanical isolation between the motors and the rest of the machine, this decreasing the noise. 
     While the exemplary embodiment of the invention has been limited to a three-by-four array of cartridges, it must be understood that much larger magazine can be used with corresponding increase in motors and actuators. The cartridges can be shaped to accommodate a variety of packages not necessarily of a rectangular geometry. The spacing and dimensioning of the track mechanisms may be adjusted to accommodate differently shaped and sized carriers. 
     Referring now to  FIGS. 9-17 , there is shown the components of an embodiment of a ratcheting device  127  used to transport and dispense a series of packaged articles  128  supported by carriers  129 . 
     As shown in  FIGS. 9 and 10  each carrier  129  comprises a head  138  from which projects along a substantially vertical axis  222 , a substantially cylindrical shank  220  secured at a distal end to the package  128 . The head includes an upper first section  140  and a lower second section  141  both centered on the axis of the shank  220 . The first section has a polygonal periphery  142  featuring at least three pairs of parallel sides preferably an oblong octagonal one as shown. The second section has a lesser diameter than the first. As shown in  FIG. 10 , the periphery of the second section  141  can be shaped to have a pair of tangentially and oppositely extending prongs  219 . A similar head is used on some FLAVIA® brand coffee packages commercially available from the Mars Incorporated of McLean, Va. This shape allows the packages to be queued on a loading rail in an orientation which is rotated approximately 45 degrees with respect to the axis of the shank This provides the queue with a narrower lateral cross section to help reduce lateral bulkiness during transport. 
     The carriers are engaged into a U-shaped oblong track  130  having parallel side walls  131 ,  132  and flanges  133 ,  134  projecting inwardly from the bottom edges of the walls. Each carrier shank  220  passes between the flanges  133 ,  134 . 
     As more specifically shown in  FIG. 11 , one of the flanges  134  extends approximately half way through the width of the track  130  and terminates in a small bead or ridge  135 . The area defined by the roof  136  of the track, the side wall  132  and the flange  134  houses the components of the ratcheting assembly  137 . In this way the ratcheting assembly essentially engages and operates on the packaged articles from a single direction, namely a single lateral side. 
     The head of each carrier is engaged in a channel  123  defined between the ridge  135  and flange  133  where the lower section  141  of the head rides along and in intermittent contact with a drive rack  143  in the shape of a plate, and the upper section  140  rides along and in intermittent contact with a friction structure in the form of a locking rack  144  also in the shape of a plate. The locking rack is substantially commensurate with and in sliding contact with the drive rack, and positioned immediately above it. 
     Referring now to  FIGS. 9 ,  11  and  14 - 16 , the drive rack  143  has a series of uniformly spaced apart sawtooth-shaped prominences  145  along the edge facing and contacting the lower sections  141  of the heads. The prominences are shaped, dimensioned and positioned to propel the carriers forward in a first axial direction, as indicated by arrow F, toward a distribution station as the drive rack is held in a driving first transversal position as shown in  FIG. 14 . 
     The locking rack  144  has a series of uniformly spaced apart indentations  146  separated by substantially trapezoidal teeth along the edge facing and contacting the upper sections  140  of the heads  138 . The indentations are shaped, dimensioned and positioned to capture the upper sections of the heads while the locking rack is held in a locking second crosswise location as shown in  FIG. 13 . 
     As shown in  FIG. 12 , during a drive stroke, the ramping front edges  147  of the indentations  146  of the locking rack  144  are contacted by the correspondingly angled surfaces  225  of the upper sections  140  of the carrier heads  138  as the latter are pushed forward which causes the locking rack to be translated obliquely sideways  139  to a unlocking first crosswise location shown in  FIG. 12 . This allows the side edges  227  of the upper sections  140  of the carrier heads to freely slide along the side edges  290  of the teeth. 
     As the upper sections  140  of the heads  138  reach the ends of the side edges  290  of the teeth, the locking rack  144  can snap back into a locking second crosswise location as shown in  FIG. 13  as the upper sections of the heads fall into the next successive indentation  146 . In this position the locking rack prevents the carriers from moving backwards as the drive rack  143  is withdrawn in a second axial direction opposite the first one during a reset stroke. 
     The movements of the drive rack  143  are controlled be a push rod  148  having a flat top surface  150  riding against the flat underside  149  of the drive rack. An opposite flat bottom surface of the push rod rides upon the flat upper surface  154  of the flange  134  of the track  130 . A pair of short, oblong nibs  153   a,    153   b  project upwardly from the top surface of the push rod into a corresponding pair of oblique grooves  151   a,    151   b  cut into the drive rack. The nibs and the grooves are slanted at an angle of about 45 degrees to the travel axis X-X′ of the rod and racks. 
     As shown in  FIG. 14 , during a drive stroke, as the push rod  148  moves forward, the nibs  153   a , 153   b  bear against the frontward ends  152  of their respective grooves  151   a , 151   b  thus pushing the drive rack  143  forward. The dimensioning of the nibs and grooves and the inertia of the carriers and appended packages prevent the drive rack from moving out of this driving first transversal position, thus keeping the drive rack engaged with the lower sections  141  of the heads during the drive stroke. The drive stroke completes when an endstop  164  on the push rod abuts against a surface  290  at the rear of the track  130  and a frontmost package  168  in the queue has been ejected. 
     As shown in  FIG. 15 , during a reset stroke, the drive rack  143  is intended to be axially withdrawn by moving in the rearward direction as indicated by the arrow R. During the reset stroke the locking rack  144  immobilizes the carriers as previously shown in  FIG. 13 . In order to allow the drive rack to pass over the lower sections  141  of the carrier heads which are being held in place by the locking rack, the ramping back edges  145   b  of the prominences  145  contact the lower sections of the carrier heads causing the drive rack  143  to be translated obliquely sideways  159  and progressively retracted toward a resetting second transversal position shown in  FIG. 15 . Simultaneously, the grooves  151   a,    151   b  slide angularly over the nibs  153   a,    153   b.  In this resetting second transversal position the flattened side edges  145   a  of the prominences freely slide along the side edges  229  of the lower sections  141 . As the prominences pass over the distal ends of the prongs  219 , the drive rack is allowed to snap back to its driving first tranversal position as shown in  FIG. 14 . 
     The drive rack is shifted back into its driving first transversal position in engagement with the carrier heads under the resilient movement of a pair of cantilever springs  155   a,    155   b  acting on a pair of corresponding stubs  157   a,    157   b  extending downward from the underside  149  of the drive rack into windows  160   a,    160   b  cut into the push rod. The springs  155   a,    155   b  consist of thin tongues projecting axially from a wall of each of the windows. 
     The push rod, drive rack and locking rack are stacked below a support plate  161 . The locking rack  144  and support plate are coupled together by a mechanism of nibs  163   a,    16   b , slanted grooves  162   a,    162   b,  stubs  165   a,    165   b  and springs  167   a,    167   b,  similar to the ones between the drive rack and the push rod. This mechanism conveniently controls the translation of the locking rack from a locking first crosswise location to an unlocking second crosswise location. It shall be understood that the drive rack and locking rack can slide independently from one another 
     Referring now to  FIG. 9 , a barrier plate  169  clipped to the distal end of the push rod  148  limits its withdrawing movement. The push rod is activated by a reciprocating actuator preferably of the type illustrated in  FIGS. 6-8 . The push rod is withdrawn under the resilient force of a coil spring  170  compressed between an endplate  182  at the edge of the push rod and a screw  183  through the flange  134  of the track  130 . 
     As shown in  FIG. 16 , a tamper resistant spring-loaded, deflectable gate  190  is formed into the proximal end of the push rod  148  to restrict it forward movement unless the gate is tripped. When untripped, the forward motion of the push rod is prevented by an endstop  191  at the distal end of the gate which contacts a surface on the track. However, when the push rod is activated by the actuator, and a force M is applied axially on the proximal end of the gate, the gate is deflected into a commensurate nook  192  in the push rod. Resilient deflection is accomplished using a thin spit of material forming a cantilever spring  193  between the gate and the push rod body. 
     Referring now to  FIGS. 17-20  there is shown an alternate embodiment of the ratcheting mechanism  337  using an alternate spring mechanism  301  for controlling the crosswise location of the locking rack and the transverse position of drive rack. 
     As shown in  FIG. 18-19  an alternate spring mechanism  301  is formed between the locking rack  344  and support plate  361 . The mechanism uses a pair of cooperating substantially semi-cylindrically shaped oblong trenches  302 , 352  formed into the opposing surfaces of the locking rack and support plate. The trench in the locking rack has a first semi-hemispherical end  303  and an opposite backstop structure  305 . 
     The backstop structure  305  extends upwardly beyond the top surface  350  of the locking rack  344  and has a flattened circular front surface  306  oriented substantially perpendicular to the elongation axis of the trench  302  and an opposite semi-hemispherically shaped back surface  307 . A similar trench  352  is formed into the undersurface  351  of the support plate  361  and oriented so that the backstop  355  of the support plate intimately and slidingly engages the trench  302  of the locking rack, and the backstop  305  of the locking rack intimately and slidingly engages the trench  352  of the support plate when the support plate and locking rack are brought together. The interface of the two mated trench and backstop structures forms a substantially cylindrical encasement for containing a coil spring  310  having ends  311  bearing against the circular inner surfaces of the respective backstops. 
     In this way, the spring  310  biases the locking rack  344  toward a second locking crosswise location where the coil spring is in an uncompressed state as shown in  FIG. 19  during a reset stroke. The resiliency of the spring is selected to allow compression of the spring and movement of the locking rack into a first crosswise location as shown in  FIG. 20  during a drive stroke. 
     As shown in  FIG. 17 , a similar spring biasing mechanisms can be used between the drive rack  343  and the push rod  348  by forming angled trenches  371  in the drive rack, and forming interfacingly located and oriented angled trenches  381  in the push rod. In this way, the mechanisms can bias the drive rack toward a driving first transversal position where the coil spring is in an uncompressed state during a drive stroke, while allowing the drive rack to move into a resetting second transversal position during a reset stroke. Thus, the mechanisms can conveniently control the translation of the drive rack between transversal positions and the locking rack between crosswise locations. 
     Referring now to  FIG. 17 , there is shown an alternate embodiment of a tamper resistant spring-loaded, deflectable gate  390  is formed into the proximal end of the push rod  348  to restrict it forward movement unless the gate is tripped. When untripped, the forward motion of the push rod is prevented by an endstop  391  at the distal end of the gate which contacts a surface  290  on the track. However, when the push rod is activated by the actuator, and a force M is applied axially on the proximal end of the gate, the gate is deflected into a commensurate nook  392  in the push rod. Resilient deflection is accomplished using a hinge connection  393  between the gate and the push rod. The gate is biased toward the untripped state by a coil spring  394 . In this embodiment the space  383  in the push rod for containing the reset coil spring is located near the distal end of the track for easier access. 
     Referring now to  FIGS. 21-25 , there is shown an alternate embodiment of the ratcheting, queued item dispensing mechanism  400  which uses a self-braking drive sled  405  for pushing the queue  401  of items such as single serving coffee packets  407  forward  408  along a support track  409  under the longitudinal reciprocating movement  460  of a crenelated drive rack  410 . The track  409  has a generally oblong extruded structure along a longitudinal axis  402  shaped and dimensioned to form a longitudinal internal elongated channel  411  having a longitudinal bottom opening  412  for slidingly accommodating and supporting the queue of items by their top-mounted carriers  415 . 
     Referring now to  FIG. 22  there is shown a cross-sectional view of the track  409  supporting the widened head  416  of a carrier  415  having a substantially cylindrical shank  417  secured to and projecting from an upper end of each packet  407  along a substantially vertical axis  418 . The generally quadrangular C-shaped cross-section of the track is formed by a pair of substantially parallel, spaced apart side walls  421 , 422  extending substantially orthogonally downward from a substantially planar upper roof  423 . A pair of lower flanges  425 , 426  project laterally and inwardly from the bottom ends of the side walls. The lower flanges are laterally spaced apart to form a central opening  412  through which the shank  417  of each of the carriers passes. The shape and dimension of the flanges and opening are selected to accommodate uninhibited passage of the packet carriers therethough. Therefore, the width of the opening is at least as large as the diameter of the carrier shank. 
     Thus the upper surfaces  427 , 428  of the lower flanges form a bearing surface for the undersurface  419  of each carrier head  416 . The undersurfaces  429 , 430  of the lower flanges form a bearing surface against which the sled braking mechanism operates, described in detail below. In this embodiment it is intended that the carriers slide freely longitudinally within the elongated channel in absence of any enhanced friction-inducing structure between the heads and the flanges, or other parts of the track, which would serve to inhibit backward motion of the packets during a reset motion of the drive rack. The presence of the self-braking sled  405  eliminates this requirement. In this way the friction of the track in the forward direction against the queue of items can be kept to a minimum. 
     The track  409  also has a pair of internal upper shelves  431 , 432  extending laterally inwardly from a medial portion of the sidewalls  421 , 422  toward one another to form support for the longitudinally reciprocating drive rack  410 . The upper shelves are laterally spaced apart to form a gap  433  through which extends a plurality of equidistantly longitudinally spaced apart rigid ratcheting prominences  406  from the bottom surface  435  of the crenelated drive rack. The drive rack and prominences can be made from a unitary piece of rigid plastic to enhance durability. The width of the gap  433  is at least as large as the lateral width of the ratcheting prominences  406 . The upper surfaces of the upper shelves form a bearing surface for bearing against the undersurface of the side ledges  438 , 439  of the drive rack. The drive rack ledges slide freely longitudinally against the upper surfaces of the upper shelves as the rack moves forward  408  during a drive stroke and backward  480  during a reset stroke. Lateral movement of the drive rack, carrier heads, and drive sled are restricted by the inner surface of the track side walls. 
     The drive rack  410  is moved longitudinally forward  408  during a drive stroke by the push on its rear, or proximal end  440  by the prong in the motor linkage as described earlier in connection with  FIGS. 6-8 . The rack is moved backward during a reset stroke through the force of one or more coil compression springs housed within the track as described earlier in connection with  FIG. 9  and the spring  170 . A tamper resistant spring-loaded deflectable gate  441 , described earlier in connection with  FIG. 17 , is formed onto the proximal end  440  of the drive rack to restrict forward movement of the drive rack unless the gate is tripped by the force of drive motor linkage. 
     Referring now to  FIGS. 23-25 , there is shown the self-braking drive sled  405  for successively pushing the queue of items forward  408  during each drive stroke. The sled has a substantially quadrangular body  450  housing mechanisms for allowing the sled to be successively engaged by and pushed forward by the drive rack  410  during a drive stroke, and disengaged from the drive rack and remain substantially stationary on the track  409  during a reset stroke. A pair of ears  451 , 452  extend laterally from the top edge  453  of the body. The ears are shaped and dimensioned to slidingly engage the elongated channel of the track  410  in a manner similar to the heads of the carriers. 
     During a drive stroke the crenelated drive rack  410  is caused to slide forward  408  along the track  409 . The sled  405  uses a spring loaded pawl  455  which is biased upwardly against the rack by a compression spring  456  loaded in opposing hollow cylindrical trenches in the pawl body and sled body. The distal tip  457  of the pawl is sized, shaped, oriented and located to catch in the crook  458  of one of a series of spaced apart prominences  459  extending downwardly from the bottom surface  411  of the drive rack  410 . Each of the prominences has a substantially sawtooth-shaped cross-section to facilitate grabbing hold of the sled pawl during the drive stroke, and sliding over the sled pawl during a reset stroke. Thus the sled is pushed forward along with the drive rack, pushing the queue of items from behind and resulting in the ejection of the front-most item in the queue. 
     During a reset stroke, the sled  405  is immobilized with respect to the track  409  by an automatically engaging brake mechanism  461  formed by a transversely oriented substantially cylindrical wedging post  462  having a major axis  463 . The post is made from a material that can frictionally wedge against the underside  429 , 430  of the lower flanges  425 , 426  of the track. The post is mounted through a pair of aligned oval foramen  464 , 465  through the lateral side walls of the sled body  450  so that the major axis  463  of the post is transverse to the longitudinal axis  402  of the track. The oval foramen are oriented at an angle A with the horizontal so that the front end  466  of the foramen is upward and the rear end  467  of the foramen is downward. A leaf spring  470  biases the post toward the front, upper end of the foramen so that the post rests against the underside of the lower flanges. The leaf spring contacts the post along a central circumferential groove  471  to prevent movement of the post along its major axis  463 . The leaf spring is held in place by engaging a hole  469  through the sled body. During a reset stroke, any slight rearward movement of the sled causes the post to ride further up the foramen and wedge more tightly against the undersurface  419 , 420  of the track. This acts to increase friction between the post and track and thus brake the rearward motion of the sled. With the sled remaining in place, the reset motion  480  of the drive rack  410  moves the angled ramp  481  of the next successive prominence  482  onto the pawl  455  causing it to retract into its passageway  459 . The rack continues to slide over the stationary sled until the pawl tip  457  snaps back into the next gap  483  between adjacent prominences. 
     During a drive stroke on the other hand, contact between the post  462  and track  409  causes the post to move substantially rearwardly  480  in the foramen and thus downwardly away from the track, thereby de-wedging it and reducing friction, thereby allowing the sled  405  to be driven forward  408  in an un-braked manner. 
     A swing arm  490  is hingedly mounted at its upper end  491  to the sled body  450 . A weight  492  is secured to its lower end  493  to keep the swing arm in a substantially vertical orientation. An endstop  494  prevents the lower end of the swing arm from swinging forward. Rearward swinging of the lower end causes the swing arm to contact the post  462  and push it rearward  480  in the oval slot toward an unlocking position. An arcuate notch  495  in the swing arm adjusts when that contact will occur. Simultaneously, rearward swinging of the swing arm will also cause a prong  496  projecting forwardly from the upper end  491  of the swing arm to contact a lower ledge  497  on the hinged pawl  455 , and push it downwardly, thus retracting the pawl into its passageway  459  and away from the prominences  459 , 482  of the drive rack  410 . This effectively disengages the pawl and braking mechanisms on the sled allowing it to slide freely along the track. The weighted swing arm also effectively disengages the sled from the drive rack when the track is tilted in a front up orientation. This allows the sled to slide freely off the back of the track to facilitate a cartridge refill operation. The swing arm also acts as an easily graspable handle for a service person to manually remove or change the position of the sled. 
     While exemplary embodiments of the invention have been described, modifications can be made and other embodiments may be devised without departing from the spirit of the invention and the scope of the appended claims.