Patent Publication Number: US-7895814-B1

Title: Case loader and method

Description:
BACKGROUND OF THE INVENTION 
     The invention relates generally to case loaders or case packers for loading articles such as bottles or plastic jugs into boxes or cases. 
     A variety of case loading machines are known. In one general type, articles to be cased are delivered by a relatively upper article supply conveyor to a loading station and are moved onto a horizontal loading gate. At the same time, cases are delivered by a relatively lower case conveyor to and are moved into position over a support table or platform of an elevator, below the loading gate and also part of the loading station. During an operation cycle, the elevator and a case are raised toward the loading gate, which is then opened to allow articles to drop into the case. The elevator is then lowered, and the case is conveyed off. 
     As a more particular example of a case loading machine of that general type of case loading machine, articles such as bottles or jugs are conveyed to the loading station, by a pair of side-by-side relatively upper article conveyors. The conveyors run continuously, and slide by underneath the articles or cases when the bottles or cases are braked or stopped, such as prior to entering the loading station. The article conveyor stops just short of the loading station, and so the last few feet of travel of the articles to be loaded is over a pneumatically-actuated loading gate, which is essentially a smooth horizontal plate. Force for moving the articles onto the loading gate is provided by backed-up articles which are still on the article conveyor belt as the article conveyor continues to move, known as line pressure force. When articles and cases are in position, the pneumatically-actuated loading gate opens to drop the articles into the cases. 
     The lower part of the loading station, which handles the cases, includes the elevator which lifts the cases up so that the articles do not have as far to drop, and then lowers the filled cases to be conveyed downstream. 
     SUMMARY OF THE INVENTION 
     In one aspect, a case loader for forming arrays of articles and dropping the articles into upwardly open cases is provided. The case loader includes a loading station having an upstream end and a downstream end, a loading gate on which articles are supported prior to being dropped, and an elevator having lowered and raised positions for positioning cases below the loading gate. The loading gate has an entry end and an opposite end. An article supply conveyor includes a moving belt on which articles are carried and delivered to the loading station to be moved on to the loading gate. An article brake is included for holding articles from the article supply conveyor short of the loading station, causing an accumulation of articles on the article supply conveyor and producing line pressure force urging articles towards the loading station. At least one conveyor article sensor is employed to sense the presence of articles on the article supply conveyor a predetermined distance upstream of the loading station to ensure that articles are present on the article supply conveyor the predetermined distance upstream to develop sufficient line pressure force before releasing the article brake to allow articles to move onto the loading gate via the loading gate entry end urged by line pressure force. A case conveyor carries and at least delivers cases to the upstream end of the loading station to be moved into position over the elevator while the elevator is in the lowered position. During operation at least one case is allowed to move into position over the elevator while the elevator is in the lowered position. The elevator is subsequently raised to the raised position before the loading gate is opened to drop articles into the at least one case, and the elevator is subsequently lowered to the lowered position to allow a loaded case to exit via the downstream end of the loading station. 
     In another aspect, a case loader for forming arrays of articles and dropping the articles into a plurality of upwardly open cases at the same time is provided. The case loader includes a loading station having an upstream end and a downstream end, a loading gate on which articles are supported prior to being dropped, and an elevator sized to support the plurality of cases and having lowered and raised positions for positioning cases below the loading gate. An article supply conveyor includes a moving belt on which articles are carried and delivered to the loading station to be moved on to the loading gate. A case conveyor carries and at least delivers cases to the upstream end of the loading station to be moved into position over the elevator while the elevator is in the lowered position and a case spacing brake is included for holding cases from the case conveyor short of the loading station. In addition, a case stop is included for holding cases within the loading station in position over the elevator. An array of case sensors is employed to ensure that previously-loaded cases are sufficiently on their way exiting via the downstream end of the loading station before the case spacing brake is released to allow the plurality of cases to move into position over the elevator while the elevator is in the lowered position, employed to determine that the plurality of cases are at least nearly in position over the elevator before the case spacing brake is applied to hold subsequent cases short of the loading station, employed to ensure that the plurality of cases are in position over the elevator before the elevator is raised and before the loading gate is opened to drop articles into the plurality of cases, and employed to ensure the trailing end of the last of the plurality of cases has exited the loading station past the case stop before the case stop is engaged to hold the subsequent cases in position over the elevator. During operation the case spacing brake is released to allow the plurality of cases to move into position over the elevator and to be held by the case stop while the elevator is in the lowered position. The elevator is subsequently raised to the raised position before the loading gate is opened to drop articles into the plurality of cases, and the case stop is subsequently released. The elevator is subsequently lowered to the lowered position, and the plurality of cases are allowed to exit via the downstream end of the loading station. 
     In yet another aspect, a case loader for forming arrays of articles and dropping the articles into upwardly open cases is provided. The case loader includes a loading station having an upstream end and a downstream end, a loading gate on which articles are supported prior to being dropped, and an elevator having lowered and raised positions for positioning cases below the loading gate. The loading gate has an entry end and an opposite end. At least one pneumatic cylinder is located underneath the elevator for raising and lowering the elevator and for serving to provide shock absorbing cushioning as articles are dropped into cases. The at least one pneumatic cylinder has a piston area selected and the pneumatic cylinder is operated at a pressure such that the at least one pneumatic cylinder can raise and support the elevator and empty cases at the raised position, but allows the elevator to move towards the lowered position under the dynamic force of dropped articles even under operating pressure. An article supply conveyor includes a moving belt on which articles are carried and delivered to the loading station to be moved on to the loading gate. A case conveyor carries and at least delivers cases to the upstream end of the loading station to be moved into position over the elevator while the elevator is in the lowered position. During operation at least one case is allowed to move into position over the elevator while the elevator is in the lowered position. The elevator is subsequently raised to the raised position before the loading gate is opened to drop articles into the at least one case and move the elevator at least towards the lowered position. The elevator is subsequently lowered to the lowered position to allow a loaded case to exit via the downstream end of the loading station. 
     In yet another aspect, a case loader for forming arrays of articles and dropping the articles into upwardly open cases is provided. The case loader includes a loading station having an upstream end and a downstream end, a loading gate on which articles are supported prior to being dropped, and an elevator having lowered and raised positions for positioning cases below the loading gate. The loading gate has an entry end and an opposite end. An article supply conveyor includes a moving belt on which articles are carried in a plurality of lanes and delivered to the loading station to be moved on to the loading gate. An article brake is included for holding articles from the article supply conveyor short of the loading station, causing an accumulation of articles on the article supply conveyor and producing line pressure force urging articles towards the loading station. A plurality of conveyor article sensors corresponding to the plurality of lanes are employed to individually sense the presence of articles on the article supply conveyor in each of the plurality of lanes a predetermined distance upstream of the loading station to ensure that articles are present on the article supply conveyor the predetermined distance upstream in all of the plurality of lanes to develop sufficient line pressure force before releasing the article brake to allow articles to move onto the loading gate in a plurality of lines corresponding to the plurality of lanes via the loading gate entry end urged by line pressure force. A case conveyor carries and at least delivers cases to the upstream end of the loading station to be moved into position over the elevator while the elevator is in the lowered position. During operation at least one case is allowed to move into position over the elevator while the elevator is in the lowered position. The elevator is subsequently raised to the raised position before the loading gate is opened to drop articles into the at least one case. The elevator is subsequently lowered to the lowered position to allow a loaded case to exit via the downstream end of the loading station. 
     In yet another aspect, a method of forming arrays of articles and dropping the articles into upwardly open cases at a loading station of the type having an upstream end and a downstream end, and including a loading gate on which articles are supported prior to being dropped, the loading gate having an entry end and an opposite end, and an elevator having lowered and raised positions for positioning cases below the loading gate is provided. The method includes the steps of employing an article supply conveyor including a moving belt on which articles are carried to deliver articles to the loading station; conveying cases to the upstream end of the loading station; holding articles from the article supply conveyor short of the loading station, causing an accumulation of articles on the article supply conveyor and producing line pressure force urging articles towards the loading station; and effecting a cyclical sequence of operations by ensuring that articles are present on the article supply conveyor a predetermined distance upstream to develop sufficient line pressure force before releasing articles to move onto the loading gate via the loading gate entry end urged by line pressure force, allowing at least one case to move into position over the elevator while the elevator is in the lowered position, subsequently raising the elevator to the raised position, and subsequently opening the loading gate to drop articles into the at least one case, and subsequently lowering the elevator to the lowered position and allowing a loaded case to exit via the downstream end of the loading station. 
     In yet another aspect, a method of forming arrays of articles and dropping the articles into a plurality of upwardly open cases at a loading station of the type having an upstream end and a downstream end, and including a loading gate on which articles are supported prior to being dropped, and an elevator having lowered and raised positions for positioning cases below the loading gate is provided. The method includes the steps of conveying articles to the loading station; conveying cases to the upstream end of the loading station; and effecting a cyclical sequence of operations by moving articles onto the loading gate, ensuring that previously-loaded cases are sufficiently on their way exiting via the downstream end of the loading station before releasing a case spacing brake to allow the plurality of cases to move into position over the elevator while the elevator is in the lowered position, determining that the plurality of cases are at least nearly in position over the elevator before applying the case spacing brake to hold subsequent cases short of the loading station, ensuring that the plurality of cases are in position over the elevator before subsequently raising the elevator to the raised position, and subsequently opening the loading gate to drop articles into the plurality of cases, and subsequently lowering the elevator to the lowered position and allowing the loaded plurality of cases to exit via the downstream end of the loading station, and ensuring that the trailing end of the last of the plurality of cases has exited the loading station past a case stop before engaging the case stop to hold the subsequent cases in position over the elevator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevational view of a case loader embodying the invention, in a somewhat schematic representation, but not showing a programmable controller portion thereof (shown in  FIG. 8 ); 
         FIG. 2  is a cross-sectional view taken on line  2 - 2  of  FIG. 1 , looking downstream from a point within the loading station of  FIG. 1 ; 
         FIG. 3  is an enlarged side elevational view of a portion of the loading station of  FIG. 1 , showing the elevator and a pair of cases in a lowered position; 
         FIG. 4  is an enlarged side elevational view similar to that of  FIG. 3 , except with the elevator and cases in a raised position; 
         FIG. 5  is a cross-sectional view taken on line  5 - 5  of  FIG. 1 , looking generally upstream towards the article conveyor from the entry end of the loading station; 
         FIG. 6  is a view taken on line  6 - 6  of  FIG. 1 , looking upstream from a point on the article conveyor towards a pair of conveyor article sensors; 
         FIG. 7  is a side elevational view taken on line  7 - 7  of  FIG. 6 , illustrating the conveyor article sensors; 
         FIG. 8  is a highly representative electrical schematic diagram of a programmable controller included as part of the case loader, showing various inputs to and outputs from the programmable controller; 
         FIG. 9  is a high level flowchart representing programming within the programmable controller of  FIG. 8 ; 
         FIG. 10  is a flowchart representing a “Process ‘A’” routine programmed within the programmable controller of  FIG. 8 , and called by the  FIG. 9  routine; and 
         FIG. 11  is a flowchart representing a “Process ‘B’” routine also programmed within the programmable controller of  FIG. 8  and called by the  FIG. 9  routine. 
     
    
    
     DETAILED DESCRIPTION 
     Referring initially to  FIGS. 1-4 , a case loader  20  embodying the invention includes a loading station  22  having upper  24  and lower  26  portions, a relatively upper article supply conveyor  28  including modular conveyor belts  30  and  32  ( FIGS. 1 ,  5 ,  6  and  7 ) on which articles in the representative form of one-gallon plastic milk jugs  34  are carried and delivered to the loading station  22 . Each of the modular conveyor belts  30  and  32  of the article conveyor  28  is a Rexnord style flat top chain, such as an “880 series” chain. The case loader  20  additionally includes a relatively lower case conveyor  36  which carries and at least delivers cases  38  to the loading station  22 . The representative cases  38  are made of corrugated cardboard, and each has a main body  40  and two longitudinally-extending side flaps  42  and  44  differentiated from the main body  40  by fold lines  46  and  48 , but no end flaps. The illustrated cases  38  are generally square in plan view, and are sized to each hold four articles. A belt-type downstream conveyor  50  receives loaded cases  38  and conveys the cases  38  for further operations, such as sealing the cases closed (not shown). The case loader  20  additionally includes a programmable controller  60  ( FIG. 8 ) to control operation of the case loader  20 . 
     It will be appreciated that  FIG. 1 , as well as the other FIGS., is a highly schematic representation which, for clarity of illustration, omits a number of conventional elements, in particular structural supports for the various sensors, brakes and actuators described in detail hereinbelow. In addition, for clarity of illustration, conventional article guides associated with the article supply conveyor  28  are not shown in  FIG. 1 , but are represented in the cross-sectional views of  FIGS. 5 and 6 . It will further be appreciated that case loaders embodying the invention may be constructed and adjusted so as to load articles of a variety of sizes, and with fewer or more articles packed into each case. 
     The loading station  22  more particularly, with reference to the direction of movement of cases  38  into and out of the loading station  22 , has an upstream end  70  and a downstream end  72 . (Although in the case loader  20  of  FIG. 1  the articles  34  move left to right in the same direction as the cases  38 , the invention may as well be embodied in case loaders in which the articles  34  and the cases  38  approach the loading station  22  from opposite directions, or even at right angles to each other.) 
     The article supply conveyor  28  of the particular case loader  20  illustrated and described herein carries and delivers articles to the loading station  22  in a plurality of lanes, in particular, in two lanes  74  and  76 . In addition, the case conveyor  36  of the case loader  20  illustrated and described herein delivers cases  38  to the loading station  22  a plurality at a time, in particular, two at a time, to be loaded at the same time. 
     Referring briefly to  FIGS. 5 and 6 , the two modular conveyor belts  30  and  32  the article supply conveyor  28  are separated by a center divider having a relatively higher portion  84  shown in  FIG. 5 , and a relatively lower portion  86  farther upstream, shown in  FIG. 6 . Articles on the modular conveyor belts  30  and  32  are confined by side panels  88  and  90  shown in cross-section in  FIG. 5 , and by side guide rails  92  and  94  farther upstream as shown in  FIG. 6 . For clarity of illustration, the side panels  88  and  90  and guide rails  92  and  94  are omitted from  FIG. 1 . 
     The article supply conveyor  28  stops short of the loading station  22 . Line pressure force is relied upon to move articles  34  into the upper portion  24  of the loading station  22 . 
     In contrast, the case conveyor  36  extends all the way into the lower portion  26  of the loading station  22  approximately up to the downstream conveyor  50 . With particular reference to  FIG. 2 , the case conveyor  50  includes a pair of flat top chains  100  and  102  or modular conveyor belts spaced apart approximately the width of a case  38  so that the two modular conveyor belts  100  and  102  together support and convey each of the cases  38 . The modular conveyor belts  100  and  102  also are each a Rexnord style “880 series” flat top chain, and are supported in respective longitudinal bearing guides  104  and  106 , made of a plastic material such as Acetal or UHMW which has a relatively low coefficient of friction. 
     Referring again to  FIGS. 1-4 , as its operative element, the upper portion  24  of the loading station  22  has a pair of pneumatically-actuated loading gates  110  and  112  onto which articles are delivered by the article supply conveyor  28  and on which the articles  34  are supported prior to being dropped into the cases  38 . Articles  34  are moved onto the loading gates  110  and  112  by “line pressure force,” described hereinbelow, in two lines  114  and  116  corresponding to the two lanes  74  and  76  of the article supply conveyor  28 . The loading gates  110  and  112  each have an entry end  124  and an opposite end  126 . The upper portion  24  of the loading station  22  is open at the entry end  124  of the loading gates  110  and  112 , but is blocked at the opposite end  126  of the loading gates  110  and  112  by an end wall  128 . 
     Each of the loading gates  110  and  112  is operated or moved by a pair of pneumatic cylinders, for a total of four loading gate actuator cylinders  130 ,  132 ,  134  and  136 , all of which are schematically represented in  FIG. 8 . In the side elevational views of  FIGS. 1 ,  3  and  4 , loading gate actuator cylinders  130  and  132  are visible. In the cross-sectional view of  FIG. 2 , loading gate actuator cylinders  132  and  136  are visible. 
     In addition to the loading gates  110  and  112 , the upper portion  24  of the loading station  22  includes a pair of side guide panels  138  and  140  for laterally confining articles  34  on the loading gates  110  and  112 , as well as a center divider  142 . The side guide panels  138  and  140  of the upper portion  24  of the loading station  22  are extensions of the side panels  88  and  90  at the downstream end of the article supply conveyor  28  shown in  FIG. 5  but not shown in  FIG. 1 . Likewise, the center divider  142  is an extension of the portion  84  of the conveyor  28  center divider shown in  FIG. 5 . A plurality of grid fingers  144 , in the illustrated embodiment twelve grid fingers  144 , are provided for guiding the articles  34  as the articles  34  are dropped into the cases  38 . 
     The lower portion  26  of the loading station  22  includes a loading platform  150  or elevator  150  over which cases  38  to be loaded are moved while the elevator  150  is in a lowered position as illustrated in  FIGS. 1-3 . With particular reference to  FIG. 2 , in its lowered position the elevator  150  is below and spaced from cases  38  supported on the tracks  100  and  102  of the case conveyor  36 . Accordingly, when the elevator  150  is in its lowered position, cases  38  can be moved into position over the elevator  150  by the case conveyor  36 , and as well can be carried off by the case conveyor  36  to exit via the downstream end  72  of the loading station  22  onto the downstream conveyor  50 . Since the cases  38  have side flaps  42  and  44  only, the cases  38  are free to be conveyed under the upper portion  24  of the loading station  22 , without interference by the grid fingers  144 . Thus, and with reference to  FIGS. 2 and 3 , the main body  40  of each case  38  clears the grid fingers  144 , while the side flaps  42  and  44  travel to the outside of the grid fingers  144 . During operation, cases  38  are moved by the case conveyor  36  into position over the elevator  150  while the elevator  150  is in the lowered position of  FIGS. 1-3 . The elevator  150  subsequently is raised to a raised position illustrated in  FIG. 4 . The loading gates  110  and  112  subsequently are opened to drop articles  34  into the cases  38 . The elevator  150  subsequently is lowered to the lowered position to allow loaded cases  38  to exit via the downstream end  72  of the loading station  22 . 
     For raising and lowering the elevator  150 , a pair of pneumatic cylinders  152  and  154  are provided, located underneath the elevator  150  or loading platform  150 . In order to provide shock absorbing cushioning as articles  34  are dropped into cases  38 , the pneumatic cylinders  152  and  154  each have a piston area selected and the pneumatic cylinders  152  and  154  are operated at a pressure such that the pneumatic cylinders  152  and  154  can fully raise and support the elevator  150  and empty cases  38  in the raised position of  FIG. 4 , but which allows the elevator  150  and loaded cases  38  to “sink” or move towards the lowered position of  FIG. 3  under the dynamic force of dropped articles  34 , even while the pneumatic cylinders  152  and  154  are under operating pressure. In other words, even though the programmable controller  60  of  FIG. 8  is directing or commanding the pneumatic cylinders  152  and  154  to raise the elevator  150  to the fully-raised position of  FIG. 4 , the operating pressure is not sufficient to overcome the dynamic force of the dropped articles  34 . As a result, shock absorbing cushioning is inherently provided as the articles  34  are dropped into the cases  38 , resulting in less potential for damage. 
     As a particular example, the pneumatic cylinders  152  and  154  are each Parker FW2C111631X06.00 double acting cushioned pneumatic cylinders having a piston area of 4.90 square inches and a stroke of six inches, and designed to be operated at a pressure of 250 psig, to provide a force of 1225 pounds. In the disclosed embodiment, the pneumatic cylinders  152  and  154  are operated at a pressure of 18 psig, which provides a force sufficient to lift 88 pounds each. The elevator  150  and empty cases  38  weigh approximately thirty pounds, and the two pneumatic cylinders  152  and  154  accordingly together raise the elevator  150  and empty cases  38  to the fully raised position of  FIG. 4 . However, when four articles  34  in the form of one-gallon milk jugs are dropped into each of two cases  38  on the raised elevator  150  (approximately seventy dropped pounds total), the dynamic force developed overcomes the force exerted by the cylinders  152  and  154 , and, in a cushioning action, the elevator  150  sinks towards the lowered position of  FIG. 3 , but without actually setting the loaded cases  38  down on the case conveyor  36 . Thereafter, the  FIG. 8  controller  60  commands or directs the pneumatic cylinders  152  and  154  to move the elevator  150  to the fully lowered position of  FIG. 3 , which sets the loaded cases  38  onto the case conveyor  36  to exit via the downstream end  72  of the loading station onto the downstream case conveyor  50 . 
     As part of an orderly sequence of operation, an article brake, generally designated  160 , is provided for holding articles from the article supply conveyor  28  short of the loading station  22 . Among other things, this causes an accumulation of articles  34  on the article supply conveyor  28  producing line pressure force urging articles  34  towards the loading station  22  as the tracks  30  and  32  of the continuously-moving article conveyor  28  slide by underneath braked (stopped) articles. 
     Similarly, a case spacing brake  162  is provided for holding cases  38  from or conveyed by the case conveyor  36  short of the lower portion  26  of the loading station  22 . The brake  162  is referred to as a “case spacing” brake because one of its functions is to achieve spacing between cases  38  on the case conveyor  36  and cases  38  within the loading station  22  in position over the elevator  150 . In addition, a case stop  164  is provided, for holding cases  38  within the lower portion  26  of the loading station  22  in position over the elevator  150  and directly under the loading gates  120  and  122 , particularly when the elevator  150  is in the lowered position as shown in  FIG. 3 . 
     Further details and operation of the article brake  160 , the case spacing brake  162  and the case stop  164  are described in greater detail hereinbelow. 
     With reference to  FIGS. 1 and 5 , the article brake  160  more particularly takes the form of a vertically driven article stop  170  which descends to block the passage of articles (the position shown in  FIGS. 1 and 5 ), and which is raised to allow the passage of articles  34 . The vertically driven article stop  170  more particularly includes a pair of vertical rods  172  and  174 , one for each of the two lanes  74  and  76 . The vertical rods  172  and  174  pass through respective apertures  176  and  178  in a plastic bearing block  180 , and are interconnected by a cross piece  182 . The cross piece  182  is in turn driven by the rod  184  of a pneumatic cylinder  186 . The pneumatic cylinder  186  is also represented in  FIG. 8 . 
     With reference to  FIGS. 1 ,  3  and  4 , the case spacing brake  162  takes the form of a pneumatic cylinder  190  (also represented in  FIG. 8 ), having a cylinder rod  192 . The cylinder rod  192  of the pneumatic cylinder  190  is arranged so as to either engage the side of a case  38  as illustrated in  FIGS. 1 ,  3  and  4 , (either by friction or aided by a projecting point  194  ( FIG. 8 ) on the end of the rod  192 ), or by projecting out in front of into the path of the case  38  to serve as a barrier (not specifically shown). Which mode of holding cases  38  short of the loading station  22  occurs depends upon whether or not a case  38  happens to be positioned directly in front of the pneumatic cylinder  190  serving as the case spacing brake  162  when the pneumatic cylinder  190  is actuated. 
     The case stop  164  at the downstream end  72  of the loading station similarly takes the form of a pneumatic cylinder  200  (also represented in  FIG. 8 ). The pneumatic cylinder  200  has a rod  202  which, as represented in  FIG. 2 , projects out into the path of oncoming cases to provide a positive barrier when actuated (in contrast to engaging the side of cases  38  as can occur during operation of the case spacing brake  162 ). 
     Although the representation of  FIG. 1  implies steady and continuous supply of both articles  34  to be loaded and cases  38  into which the articles are to be loaded, as a practical matter, during actual operation, such is not always the case. The upstream supply of articles  34  (e.g. filled milk jugs) can be interrupted for a variety of reasons, depending upon other processes within the facility in which the case loader  20  is employed. Moreover, the supply of articles  34  may be interrupted in one of the lanes  74  or  76 , but not the other. Likewise, for a variety of reasons, the upstream supply of empty cases  38  may be interrupted. 
     Accordingly, to achieve smooth and reliable operation the controller  60  of  FIG. 8  directs the operation of the various actuated or controlled elements in an appropriate manner. The controlled elements include the article brake  160 , case spacing brake  162  as well as the case stop  164 , the pneumatic cylinders  152  and  154  which raise and lower the elevator  150 , and the pneumatic cylinders  130 ,  132 ,  134  and  136  which open and close the loading gates  110  and  112 . Inevitably, mis-positioning of articles  34  and cases  38  occurs, interrupting smooth loading operation and requiring manual intervention. However, embodiments of the invention minimize such occurrences. 
     As one particular aspect, the case loader  20  implements what is herein termed “line pressure control” to ensure that a sufficient number of articles  34  are backed up in each lane  74  and  76  of the article supply conveyor  28  to reliably push articles  34  onto the loading gates  110  and  112  of the loading station  22  when the article brake  160  is released. 
     So long as articles  34  are present on the article supply conveyor  28  in both lanes a predetermined distance “d” ( FIG. 1 ) upstream of the loading station  22 , there is sufficient line pressure force to reliably move articles  34  onto the loading gates  110  and  112  of the loading station  22 . Although the terminology “predetermined distance” is employed herein, it will be appreciated that the predetermined distance “d” as a practical matter is a minimum distance, determined at least in part by experimentation; a “predetermined distance” may be conservatively established which is in fact greater than would be actually be required. By way of example, and not limitation, in one particular example, for a relatively slow line, the predetermined distance “d” is established as three feet nine inches, which is equivalent to the length along the article supply conveyor  28  occupied by eight one-gallon milk jugs (one more than the seven milk jugs which happen to be illustrated in  FIG. 1 ). The “predetermined distance” varies based on line speed and bottle type. 
     At least one conveyor article sensor, generally designated  210 , is employed to sense the presence of articles  34  on the article supply conveyor  28  the predetermined distance “d” upstream of the loading station  22 . With particular reference to  FIGS. 6 and 7 , in the illustrated embodiment, in which articles are carried in a plurality of lanes, in particular the two lanes  74  and  76  of the article supply conveyor  28 , a corresponding plurality of conveyor article sensors are employed, in particular, conveyor article sensors  212  and  214 . 
     The conveyor article sensor  210  includes two side supports  216  and  218 , the lower structural connections for which are not shown. A pivot rod  220  extends between the side supports  216  and  218  near the upper ends thereof. A pair of swinging sensor arms  222  and  224  pivotally hang from the pivot rod  220 . The two sensor arms  222  and  224  may be viewed as the individual conveyor article sensors  212  and  214  corresponding to the two lanes  74  and  76 . When no articles  34  (e.g. milk jugs) are present, both sensor arms  222  and  224  hang vertically. However, when an article is present, as is best seen in  FIG. 7 , the sensor arms  222  and  224  pivot away from the vertical position. As each article  34  (milk jug) passes, the sensor arms  222  and  224  pivot further as required to allow unrestricted passage. 
     In order to prevent free swinging of the sensor arms  222  and  224  in a direction towards the upstream end of the article supply conveyor  28 , a backstop bar  226  extends between the side supports  216  and  218  below the pivot rod  220 . 
     The conveyor article sensor  210  additionally includes an optical sensor  228  defining a viewing or sensing line  230  extending from the side support  216  to the side support  218  directly under and parallel to the pivot rod  220 . The optical sensor  228  is positioned so that both of the sensor arms  222  and  224  must be deflected for the optical sensor  228  to indicate the presence of articles. Thus, a logical “AND” function is provided in part by the mechanical arrangement, and the signal from the optical sensor  228  is a combined signal, responsive to both of the sensor arms  222  and  224  or conveyor article sensors. If an article  34  is present in one of the lanes  74  or  76  the predetermined distance “d” upstream of the loading station  22 , but not in the other lane  74  or  76 , then the sensor  228  does not provide a “true” signal. For adjustment purposes, the optical sensor  228  is mounted through a vertical slot  232 . 
     A suitable sensor for the optical sensor  228  is an Allen-Bradley 42CA, 42CF, 42CM or similar photoelectric sensor. 
     To ensure that articles  34  are in position at the opposite end  126  (against the end wall  128 ) before the loading gates  110  and  112  are opened, a loading gate article sensor generally designated  240  is provided. Thus, at least one loading gate article sensor and, in the illustrated embodiment, a pair of loading gate article sensors  242  and  244 , is provided to sense the presence of articles  34  at the opposite end  126  of the loading gates  110  and  112  against the end wall  128 . 
     With particular reference to  FIG. 2 , the loading gate article sensor  240  includes a pair of side supports  246  and  248  extending downwardly from support structure above (not shown), and a pivot rod  250  extends between the side supports  246  and  248 . A pair of levers  252  and  254  hang from the pivot rod  250 , and are positioned so as to be deflected when articles  34  are present. The levers  252  and  254  have respective lower arms  256  and  258  which are actually contacted by the articles  34  when present and are thereby moved in a downstream direction, and respective upper arms  260  and  262  which are pivoted in an upstream direction when articles are present. To sense the position of the upper arms  260  and  262 , and thus whether articles  34  are present in the two lines  114  and  116  on the loading gates  110  and  112 , respective inductive proximity sensors  264  and  266  are employed. When articles  34  are not present, then the levers  252  and  254  hang vertically, and the inductive proximity sensors  264  and  266  sense the proximity of the upper arms  260  and  262 . When articles  34  are in position on the loading gates  110  and  112 , the inductive proximity sensors  264  and  266  sense that the upper arms  260  and  262  have moved away, which is the signal condition indicating article presence. Suitable sensors for the inductive proximity sensors  264  and  266  are Allen-Bradley 871™ or similar inductive proximity sensors. 
     Significantly, use of the loading article sensors  242  and  244  in combination with line pressure control effected by use of the conveyor article sensors  212  and  214  for each of the lanes  74  and  76  provides a high degree of reliability in ensuring that articles are properly moved onto the loading gates  110  and  112  and in proper position before the loading gates  110  and  112  are opened to drop articles  34  into cases  38  below. 
     Another aspect of the case loader  20  is that sensors are employed as described hereinbelow in detail and the case loader  20  is operated in a manner which ensures that cases  38  are in position before the elevator  150  is raised and before the loading gates  110  and  112  are opened. In addition, sensors are provided (again, as described in detail hereinbelow) and the case loader  20  is operated in a manner such that loaded cases are sufficiently on their way out of the loading station  22  onto the downstream conveyor  50  before the case spacing brake  162  is released, allowing empty cases  38  to enter the lower portion  26  of the loading station  22 . In addition, sensors are provided (again, as described hereinbelow) and the case loader  20  is operated in a manner such that cases  38  are at least nearly in position before the case spacing brake  162  is reapplied. Moreover, in the illustrated embodiment a plurality of cases, in particular two cases  38 , are loaded at the same time. 
     More particularly, an array, generally designated  270 , of case sensors is employed to ensure that previously-loaded cases  38  are sufficiently on their way exiting via the downstream end  72  of the loading station  22  before the case spacing brake  162  is released to allow the plurality of cases to move into position over the elevator  150  while the elevator  150  is in the lowered position, employed to determine that the plurality of cases  38  are at least nearly in position over the elevator  150  before the case spacing brake  162  is applied to hold subsequent cases short of the loading station  22 , employed to ensure that the plurality of cases  38  are in position over the elevator  150  before the elevator is raised and before the loading gates  110  and  112  are opened to drop articles  34  into the plurality of cases  38 , and employed to ensure that the trailing end of the last of the plurality of case  38  has exited the loading station  22  past the case stop  164  before the case stop  164  is engaged to hold the subsequent cases in position over the elevator  150 . 
     Although cases are generally designated  38 , embodiments of the invention load a plurality of cases  38  at the same time, in the illustrated embodiment two cases. In the following description of the array  270  of case sensors, reference is made to two cases designated  272  and  274  ( FIGS. 3 and 4 ) being loaded at the same time. Case  272  is the relatively downstream or first case, and case  274  is the relatively upstream or second case. 
     With particular reference to  FIGS. 1 ,  3  and  4 , four case position sensors  282 ,  284 ,  286  and  288  are employed, respectively designated case position sensors # 1 , # 2 , # 3  and # 4 . For clarity of illustration, supports for the case position sensors  282 ,  284 ,  286  and  288  are not shown. The case position sensors  282 ,  284 ,  286  and  288  are located just off to the side as indicated by the positioning of the case position sensor  286  (sensor # 3 ) in  FIG. 3 . The case position sensors  282 ,  284 ,  286  and  288  (sensors # 1 , # 2 , # 3  and # 4 ) are positioned such that cases  272  and  274  are sensed, if present, whether in the lower position ( FIG. 3 ) or upper position ( FIG. 4 ). The case position sensors  282 ,  284 ,  286  and  288  are optical sensors, and may be Allen-Bradley 42SRP or similar photoelectric sensors. 
     Additionally, an elevator position sensor  290  is provided. The elevator position sensor  290  is employed to sense when the elevator  150  is raised, to ensure that the loading gates  110  and  112  are not opened unless the elevator  150  is in its raised position. As shown in  FIG. 2 , the line of sight  292  of the elevator position sensor  290  is angled downwardly so as to view an empty space underneath the elevator  150  when the elevator  150  is raised, as is also apparent by contrasting  FIG. 4  (elevator  150  raised) with  FIG. 3  (elevator  150  lowered). 
     The exemplary cases  272  and  274  are each twelve inches long. Case position sensor  282  (# 1 ) is positioned so as to be very near the leading end of the first case  272  when the case  272  is against the case stop  164 , such as one inch from the case stop  164 . Case position sensor  284  (# 2 ) is located several inches upstream, such as six inches upstream. Case position sensors  286  and  288  (# 3  and # 4 ) are respectively positioned very near the leading and trailing ends of the second case  274  when the second case  274  is in proper position. For twelve-inch cases  272  and  274 , sensors # 3  and # 4  are 11½ inches apart. Moreover, the case position sensor  286  (# 3 ) is located so as to sense a gap (the absence of a case) in the event two cases  272  and  274  on the elevator  150  are too far apart, in which case operator intervention is required to correct the mis-positioning to allow operation to continue. 
     A final sensor illustrated in  FIGS. 1 ,  3  and  4  is a case clear sensor  294 , likewise an optical sensor employed to ensure that loaded cases  38  (e.g. cases  272  and  274 ) have completely exited the loading station  22  before the case stop  164  is reengaged. 
     The overall operation of the case loader  20  is controlled by the programmable controller  60 , represented in  FIG. 8  by various sensor inputs and control outputs. A suitable programmable controller is an Allen-Bradley “MicroLogix 1000” programmable logic controller. It will be appreciated that conventional interfacing devices such as optical isolators and drivers are omitted from  FIG. 8 . Likewise, it will be appreciated that the various pneumatic cylinders are operated from a compressed air supply, controlled via conventional solenoid valves which likewise are not specifically shown. 
     Programming within the  FIG. 8  programmable controller  60  to effect overall operation is represented in the program flowcharts of  FIGS. 9 ,  10  and  11 . The  FIG. 9  flowchart represents the overall operation, which loops continuously during operation of the case loader  20  to effect a cyclical sequence of operations. In the event of a malfunction, such as articles  34  or cases  38  being mis-positioned as inevitably happens from time to time, operation pauses while an operator manually corrects the condition, and operation resumes with minimal disruption or loss of product. 
     With particular reference to  FIG. 9 , the program enters at  300 . In box  302 , an initialization sequence occurs. The controller  60  ensures that the article brake  160  is applied, ensures that the case spacing brake  162  is applied, ensures that the loading gates  110  and  112  are closed, ensures that the elevator  150  is lowered, and ensures that the conveyors  28 ,  36  and  50  are running. 
     Beginning the main loop of the program, execution proceeds to two concurrent processes, represented by boxes  304  and  306 , both of which must be completed before operation continues from “AND” junction  308 . Box  304  represents a process “A” represented by the flowchart of  FIG. 10 , to sense the presence of articles  34  on the article supply conveyor  28  and to allow the articles  34  to move onto the loading gates  110  and  112 . More particularly, as part of the cyclical sequence of operations, articles  34  on the article supply conveyor  28  are held short of the loading station  22  by the article brake  160 . Sensors are employed to ensure that articles  34  are present in both lanes  74  and  76  of the article supply conveyor  28  the predetermined distance “d” upstream of the loading station to develop sufficient line pressure force before releasing the article brake  160  thereby releasing the articles  34  to move onto the loading gates  110  and  112  urged by line pressure force. Box  306  represents a process “B” represented in the flowchart of  FIG. 11 , which positions two cases  38  over the elevator  150 . More particularly, a part of the cyclical sequence of operations, sensor # 2  is employed to ensure that previously-loaded cases are sufficiently on their way exiting via the downstream end  72  of the loading station  22  before releasing the case spacing brake  162  to allow a plurality of cases (e.g. the two cases  272  and  274 ) to move into position over the elevator  150  while the elevator is in its lowered position. The case clear sensor  294  is employed to ensure that the last of the plurality of cases has exited past the case stop  164  before engaging the case stop  164  to hold subsequent cases in position over the elevator  150 . 
     When both those conditions are satisfied, then execution proceeds from “AND” junction  308  to box  310  where the pneumatic cylinders  152  and  154  are actuated to raise the elevator  150 . At the same time, the case stop  164  is released, since cases lifted by the elevator  150  are not subject to being conveyed by the case conveyor  36  while raised off the conveyor  36 , and the case stop  164  is not needed. 
     Next, in box  312 , represented as a delay process, the elevator position sensor  290  is employed to ensure the elevator  150  is raised. In addition, all four case position sensors  282 ,  284 ,  286  and  288  (sensors # 1 , # 2 , # 3  and # 4 ) are employed to ensure that both cases  272  and  274  are in position on the elevator  150  as the elevator  150  is raised to the position of  FIG. 4 . 
     In box  314 , the programmable controller  60  commands the loading gate actuator cylinders  130 ,  132 ,  134  and  136  to open the loading gates  110  and  112 , to drop articles  34  into the cases  38  on the raised elevator  150 . As described hereinabove, the dynamic force as articles  34  are dropped into the cases  38  causes the elevator  150  to immediately lower, even though the controller  60  is commanding the elevator  150  to be in the raised position, because the pneumatic cylinders  152  and  154  are operated at a reduced pressure as described hereinabove. Thus, shock absorbing cushioning is provided, while the cases  38  are still held above the case conveyor  36 . 
     Finally, in box  316 , the loading gates  110  and  112  are closed, and the pneumatic cylinders  152  and  154  are deactuated to allow the elevator  150  to fully lower. Since the case stop  164  has previously been released, loaded cases  38  immediately begin to move off upon contact with the case conveyor  36 . 
     As indicated by lines  318  and  320 , execution then loops back to process “A” box  304  and process “B” box  306 , and the cycle continues. 
     With reference to  FIG. 10 , process “A” enters at box  330 . In box  332 , represented as a delay process, the combined signal from the optical sensor  228  and the individual conveyor article sensors  212  and  214  is employed to ensure that articles  34  are present the predetermined distance “d” upstream from the loading station  22 , ensuring sufficient line pressure force in both lanes  74  and  76 . If there has been an interruption in the upstream supply flow of articles  34 , execution simply waits until articles are present. 
     Next, in box  334 , the article brake  160  is released to allow articles  34  to enter the upper portion  24  of the loading station  22 , and to move in the two lines  114  and  116  onto the loading gates  110  and  112  under line pressure force. 
     Next, in box  336 , again represented as a delay process, the loading gate article sensors  242  and  244  are employed to ensure that articles are present on the loading gates  110  and  112  in both lines  114  and  116 . 
     At that point, in box  338 , the article brake  160  is reapplied, and execution returns at  340  to the main routine of  FIG. 1 , entering the “AND” junction  308  from the left side. 
     With reference to the flowchart of  FIG. 11 , process “B” enters at  350 , and then splits to two concurrent processes, both of which must be satisfied in “AND” junction  352  before execution continues. 
     In the left hand branch, box  354  the controller  60  employs case position sensor  284  (# 2 ) to ensure or determine that previously-loaded cases have sufficiently moved off. Then, in box  356 , the case spacing brake  162  is released to allow empty cases  38  to enter (which may or may not enter at that time, depending upon whether empty cases are present on the case conveyor  36 ). 
     The right hand branch begins with box  358 , represented as a delay process, where the case clear sensor  294  is employed to ensure or determine that previously-loaded cases have completely exited the loading station  22  then, in box  360 , the case stop  164  is engaged. 
     When both branches are satisfied, execution proceeds from “AND” junction  352  to box  362 , represented as another delay process, to wait for case position sensors  284 ,  286  and  288  (sensors # 2 , # 3  and # 4 ) to sense incoming cases, and also to ensure that the case clear sensor  294  is still clear. 
     At that point, in box  364 , the case spacing brake  162  is applied to prevent additional cases from entering the loading station  222 . If cases are continuously present on the case conveyor  36 , then likely the case spacing brake  162  will engage the side of a case depicted in  FIG. 1 . Otherwise, the case spacing brake  162  will project out in the path of oncoming cases, to block the next case to arrive. 
     In box  366 , again represented as a delay process, case position sensors  282  and  286  (sensors # 1  and # 3 ) are employed to ensure that two cases are in position. The  FIG. 11  process then exits at  368 , to enter the “AND” junction  308  of the  FIG. 9  flowchart from the right side. 
     While specific embodiments of the invention have been illustrated and described herein, it is realized that numerous modifications and changes will occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit and scope of the invention.