Patent Publication Number: US-8966890-B2

Title: Method and arrangement for active make-up in an overrunning actuator

Description:
TECHNICAL FIELD 
     This disclosure relates generally to a hydraulic circuit for a double acting actuator, and, more particularly to arrangements for active fluid make-up in an overrunning actuator. 
     BACKGROUND 
     Dumping the load of a truck preferably occurs as a gradual evacuation. With certain materials, however, such as the materials collected from the Canadian oil sands, the contents of the bed can adhere together, and dump as a single unit, or a small number of relatively large units. This phenomenon is referred to as loafing. 
     The dumping of a load is accomplished by way of a plurality of actuators. In viewing the structure of an actuator, a rod extends from the one side of the piston and outward from the cylinder. When dumping, the actuators extend, that is, hydraulic fluid is evacuated from the rod chamber of the actuator and hydraulic fluid is moved to the head chamber. As a bed is moved to start the dumping motion, the force of the load acts to compress the actuators. As the load continues to shift toward the dumping end of the bed, however, a situation occurs that is commonly referred to as an overrunning load if the load does not proceed gradually to dump from the bed. That is, if the load acts as a loaf, the force of the shifting load causes a moment that exerts a force on the actuator in the extending direction of the actuator. 
     If the flow of fluid to the head chamber is inadequate to meet the demands of the forcibly extending actuator, an undesirable severe voiding results in the head end of the actuator. In other words, a vacuum develops in the head chamber as the volume of the head chamber extends beyond the volume of the hydraulic fluid flowing to the head chamber. As a result, when the load drops from the bed as a loaf, the vacuum formed in the head chamber causes the actuator to rapidly retract. This significant and undesirable dynamic event can result in discomfort, and even injury to a machine operator, or damage to the machine. 
     In prior art arrangements, a hydraulic tank is provided as an external source of make-up flow to the hoist valve of the actuator. Unfortunately, however, this passive arrangement is often inadequate to meet the needs of an overrunning actuator, and an alternative solution is desirable. 
     SUMMARY 
     In one aspect, there is disclosed a hydraulic system comprising an actuator having a piston disposed within a cylinder, and a rod extending from the piston and extending out of the cylinder. The piston defines a rod chamber and a head chamber within the cylinder. The piston and rod is adapted to move between a retracted position and an extended position. The hydraulic system also includes a first source of hydraulic fluid, and a first pump adapted to provide hydraulic fluid from the first source to the head chamber. The hydraulic fluid from the first pump is provided to the head chamber at a first pressure Ph. The hydraulic system also includes a second source of hydraulic fluid, and at least one selectively actuatable valve fluidly coupled to the second source. The second source is adapted to provide hydraulic fluid at a second pressure Pb. The at least one valve provide hydraulic fluid from the second source to supplement hydraulic fluid provided to the head chamber from the first pump when the second pressure Pb is greater than the first pressure Ph. 
     In another aspect, there is disclosed a machine for hauling a load. The machine comprises a chassis, and a bed pivotably mounted to the chassis and adapted to pivot between first position and a second position. The bed is disposed to hold a load in the first position, and to dump the load in the second position. The machine also includes a hydraulic system having an actuator, first and second sources of hydraulic fluid, a first pump, and at least one selectively actuatable valve. The actuator has a piston disposed within a cylinder, and a rod extending from the piston and extending out of the cylinder. The piston defines a rod chamber and a head chamber within the cylinder. The actuator being adapted to move between a retracted position and an extended position. The actuator being coupled to the chassis and the bed and disposed to move to the extended position to pivot the bed between the first and second positions. The first pump is adapted to provide hydraulic fluid from the first source to the head chamber at a first pressure Ph. The second source of hydraulic fluid is adapted to provide hydraulic fluid at a second pressure Pb. The at least one valve is fluidly coupled to selectively provide hydraulic fluid from the second source to supplement hydraulic fluid provided to the head chamber from the first pump when the second pressure Pb is greater than the first pressure Ph. 
     In yet another aspect, there is disclosed a method of controlling a hydraulic system in a machine for hauling a load. The machine comprises a chassis with a bed pivotably mounted to the chassis and adapted to pivot between first position wherein the bed is disposed to hold a load and a second position wherein the bed is disposed to dump the load. The machine additionally includes a hydraulic system having an actuator, a first source of hydraulic fluid, and a a first pump. The actuator has a piston disposed within a cylinder, and a rod extending from the piston and extending out of the cylinder. The piston defines a rod chamber and a head chamber within the cylinder. The actuator is adapted to move between a retracted position and an extended position, the actuator being coupled to the chassis and the bed and disposed to move from the retracted position to the extended position to pivot the bed between the first and second positions. The first pump is adapted to provide hydraulic fluid from the first source to the head chamber. Hydraulic fluid from the first pump is provided to the head chamber at a first pressure Ph. The method comprising the steps of selectively fluidly coupling a second source of hydraulic fluid to at least one valve and the head chamber, and actuating the at least one valve to provide flow at a second pressure Pb from the second source to supplement hydraulic fluid provided to the head chamber from the first pump when the second pressure Pb is greater than the first pressure Ph. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING(S) 
         FIG. 1  is a side elevational view of a machine incorporating aspects of this disclosure. 
         FIG. 2  is a fragmentary schematic view of a hydraulic system according to a first embodiment of this disclosure. 
         FIG. 3  is a fragmentary schematic view of a hydraulic system according to a second embodiment of this disclosure. 
         FIG. 4  is a fragmentary schematic view of a hydraulic system according to a third embodiment of this disclosure. 
         FIG. 5  is a fragmentary schematic view of a hydraulic system according to a fourth embodiment of this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The truck  106  of  FIG. 1  includes a cab  108  that is supported on a chassis  110  that includes motivators  112 , such as wheels  114 . It will be appreciated, however, that the motivators  112  may alternately be a pair of tracks, or the like. The cab  108  includes an operator station  116  from which an operator may control the operations of the machine  100 . 
     The chassis  110  additionally supports a bed  118  that is pivotably supported on the chassis  110  at pivot location (shown generally as  120 ). It is noted that the bed  118  may include a dumping gate (not illustrated) that pivots out of position to allow a load contained within the bed  118  to dump from the bed  118  when the bed  118  is tilted. An alternate arrangement, such as the one illustrated need not include such a gate. 
     The machine  100  additionally includes components of a hydraulic system  122 , including hydraulic actuators  102 . Although only one hydraulic actuator  102  is visible in  FIG. 1 , the illustrated hydraulic system  122  includes a plurality of hydraulic actuators  102  that may be extended to cause the bed  118  to pivot around pivot location  120  to dump a load. As is conventional, the hydraulic actuators  102  are pivotably coupled to the chassis  110  at one end  124 , and to the bed  118  at the other end  126 . 
     Referring to  FIG. 2 , which shows a fragmentary schematic of an embodiment of the hydraulic system  122  for operating the actuator  102 , the actuators  102  may be of a conventional design, including a cylinder  130  in which a piston  132  is slidably disposed. A rod  134  is secured to the piston  132 , and extends from the cylinder  130 . In this way, the piston  132  divides the interior of the cylinder  130  into a rod chamber  136  and a head chamber  138 . In operation, as the actuator  102  is extended, hydraulic fluid flows out of the rod chamber  136  and hydraulic fluid flows into the head chamber  138  as the piston  132  and rod  134  slide within the cylinder  130  to telescope the rod  134  outward from the actuator  102 . Conversely, as the actuator  102  is retracted, hydraulic fluid flows into the rod chamber  136  and hydraulic fluid flows out of the head chamber  138  as the piston  132  and rod  134  slide within the cylinder  130  to retract the rod  134  into the cylinder  130 . The actuator  102  may include, for example, a one or a two stage rod, although a single stage rod  134  is illustrated in this embodiment. Flow of hydraulic fluid to and from the rod and head chambers  136 ,  138  proceeds through a rod side fluid connection  140  and a head side fluid connection  142 , respectively, that are fluidly coupled to respective ports  144 ,  146  opening in the rod or head chambers  136 ,  138  in the cylinder  130 . In an embodiment of a machine such as illustrated in  FIG. 1 , the ports  144 ,  146  may be both located at the rod end of the  124  of the actuator  102 , flow to the head chamber  138  progressing through a pipe (not shown) contained in the rod  134 . Ports  144 ,  146  also may be provided in opposite ends of the actuator  102 , as illustrated in  FIG. 2 . To dump a load contained within the bed  118 , the actuators  102  are extended to pivot the bed  118  about the pivot location  120  by evacuating fluid from the rod chamber  136  and adding fluid to the head chamber  138 . During extension of the actuator  102 , fluid under pressure is evacuated from the rod chamber  136  through the port  144  and rod side fluid connection  140  to, for example, a hoist valve  150 . Simultaneously, lower pressure fluid flows from a first pump  152  through the head side fluid connection  142  and the port  146  to the head chamber  138 . 
     According to an embodiment of this disclosure, supplemental flow is provided to the head chamber  138  from an additional source  154  of pressurized fluid. In this embodiment, supplemental flow is provided from an existing pump  156  of an alternate hydraulically operated function or operation  158  that can tolerate an interruption in flow during the hoisting operation. In this embodiment, the flow is provided from a cooling pump  160 , which, during normal operation, pumps hydraulic fluid from a fluid source  162 , such as a sump  164 , to an oil cooler  166 , by way of a plurality of conduits  168 ,  170 ,  172 . It is noted that when fluid in conduit  170  reaches a preset pressure, poppet valve  173  may be triggered by a pilot control line  174  to allow fluid to be returned to the fluid source  162 . 
     In order to control the flow of fluid from the pump  156  to the actuator  102  or the alternate operation  158 , a diverter valve  180  is provided. In this embodiment, the diverter valve is pilot operated and includes first and second poppet valves  182 ,  184 . Flow from the additional source  154 , here, the pump  156 , is provided through conduit  170  to poppet valves  182 ,  184 , which are both normally in their closed positions, as illustrated in  FIG. 2 . Fluid pressure provided to the poppet valves  182 ,  184  will be at pressure Pb, that is, the pressure Pb as fluid leaves the pump  156  and travels along conduit  170 . 
     In operation, a pilot signal is provided by way of pilot line  186  from the rod side fluid connection  140  connected to the rod chamber  136 . The pilot line  186  is coupled to a pair of pilot valves  190 ,  192 , valve  190  being normally open, and valve  192  being normally closed. In this way, pressure from the rod side fluid connection  140  is provided as pressure Pr to valves  190 ,  192 , that is, the pressure Pr of the fluid leaving the rod side chamber  136  and traveling through conduit  140 . 
     In operation, if pressure Pr provided to pilot line  186  from the rod side fluid connection  140  is relatively low, pilot valve  190  remains in the open position, and pilot valve  192  remains in a closed position. A bleed orifice  194  allows any residual pressure in the pilot line  186  to vent to a drain  196 . It is noted that drain  196  and sump  164  may be the same structure or otherwise connected. With the pilot valve  190  in the open position as illustrated, when pressure Pb builds in conduit  170 , a pilot line  198  from conduit  200  extending from conduit  170  applies pressure Pb to the poppet valve  182  to move the poppet valve  182  from the illustrated closed position to an open position. As the poppet valve  182  moves from the closed to the open position against the force of a spring  202 , pressure within line  204  is vented through the pilot valve  190  to the drain  196 . 
     Turning to the poppet valve  184 , with the pilot valve  192  in the closed position, pressure on the backside of the poppet valve  184  is unable to vent, and pilot line  206  does not move the poppet valve  184  to an open position against the force of spring  208 . As a result, all of the flow from conduit  170  proceeds to conduit  200 , flowing through open poppet valve  182  to conduit  172 , and on to the alternate operation  158 , here, an oil cooler  166 . It will be appreciated by those of skill in the art that the structure various acting surfaces of the valves  182 ,  184  may be designed such that the force of fluid on the surfaces results in movement providing the desired flow direction. 
     As the pressure Pr within pilot line  186  builds, however, pilot valve  190  shifts to its closed position, terminating the vent from line  204  to the drain  196 , but continuing to allow venting to drain  196  through orifice  194 . With pilot valve  190  in the closed position, pressure Pb from conduit  200  additionally is transmitted through pilot line  210  and orifice  212  such that the forces, including that of the spring  202 , move the poppet valve  182  to the illustrated closed position, shutting off flow to the alternate operation  158 , i.e., the oil cooler  166 . 
     As pressure continues to build, the pilot valve  192  is also shifted from its normally closed position illustrated to its open position, connecting the backside of the poppet valve  184  to conduit  214  by way of line  216 . It will be appreciated that pressure Ph from the first pump  152  is applied to one side of the pilot valve  192  by way of conduits  142 ,  214 , line  216 , and pilot line  218 . In this way, pressure Ph, which is the pressure Ph of fluid leaving the first pump  152  and traveling through head side fluid connection  142 , along with the force of biasing spring  220  act on one end of the pilot valve  192 , while pressure Pr from pilot line  186  acts on the other side of pilot valve  192 . Here, pressure Pr from pilot line  186  is the same as pressure exiting the rod chamber  136  and traveling through the rod side fluid connection  140 . Thus, when Pr exceeds Ph, pilot valve  192  shifts from the closed to the open position. 
     With the pilot valve  192  in the open position, as pressure Pb from the alternate source  154  increases, pressure Pb is applied to the poppet valve  184  through conduits  170 ,  222  and pilot line  206 . As pressure Pb builds, the pressure Pb asserted on poppet valve  184 , including by way of conduit  222  and pilot line  206 , overcomes the pressure Ph from the first pump  152  asserted on the poppet valve  184 . The poppet valve  184  then moves from the closed position illustrated to the open position, connecting flow from conduit  222  to conduit  214  to provide flow supplemental to the head chamber  138  by way of conduit  142  and port  146 . This flow to the head chamber  138  from the first pump  152  and the supplemental source  154  is a relatively high flow at a relatively low pressure, while the flow from the rod chamber  136  is at a relatively high pressure, providing maximum tension force in the cylinder  130 . It will be appreciated by those of skill in the art, that this supplemental flow to the head chamber  138  provides fluid to the void that may otherwise be created in the head chamber  138  as a result of an overrunning situation. 
     Turning now to the embodiment of  FIG. 3 , the same numbers preceded by the number 1XXX are utilized to identify the various elements. Those elements identified by such corresponding numbers in  FIG. 3  that are not explained in detail below may be the same or similar to the structure explained with regard to  FIG. 2 . It is noted, however, that flow of hydraulic fluid to and from the rod and head chambers  1136 ,  1138  proceeds through a rod side fluid connection  1140  and a head side fluid connection  1142 , respectively, but the respective ports  1144 ,  1146  opening in the rod or head chambers  1136 ,  1138  are both disposed in the rod end  1124  of the actuator  1102 , flow to the head chamber  1138  progressing through a pipe (not shown) contained in the rod  1134 . As with the first embodiment, to dump a load contained within the bed  118 , the actuator  1102  is extended by evacuating fluid from the rod chamber  1136  and adding fluid to the head chamber  1138 . 
     During extension of the actuator  1102 , fluid under pressure is evacuated from the rod chamber  1136  through the port  1144  and rod side fluid connection  1140  to a hoist valve  1150 , from which the fluid may be directed, for example, to a tank  1164  via conduit  1141 . Simultaneously, a first pump  1152  pumps lower pressure fluid through the hoist valve  1150  to the head side fluid connection  1142  and the port  1146  to the head chamber  1138 . 
     According to this embodiment, supplemental flow is provided to the head chamber  1138  from the fluid source  1162 , or tank  1164  from an additional fluid source (shown generally as  1154 ) by way at least one existing pump  1156  from an alternate operation  1158  that can tolerate an interruption in flow during the hoisting operation. In this embodiment, flow is provided from a pair of cooling pumps  1160  that service the rear brakes  1166 . In this embodiment, low and high pressure valves  1182 ,  1184  may be provided separately, as opposed to being contained in a single diverter valve  180 , such as the one illustrated in the embodiment of  FIG. 2 . 
     As with the first embodiment, flow from the additional source  1154 , here, the pumps  1156 , is provided through conduit  1170  to low and high pressure poppet valves  1182 ,  1184  by way of conduits  1200 ,  1222 , respectively. Fluid pressure provided to the poppet valves  1182 ,  1184  by way of conduits  1200 ,  1222  will be at pressure Pb, that is, the pressure of the hydraulic fluid leaving existing pumps  1156  and traveling through conduit  1200 . 
     A pilot connection  1186  from the rod connection  1140  connected to the rod chamber  1136  provides pressure Pr to the poppet valves  1182 ,  1184  by way of pilot connections  1187 ,  1188 . Pressure Pr in this embodiment is the pressure of fluid leaving the rod chamber  1136  and traveling through the rod side fluid connection  1140 . As with the poppet valves  182 ,  184  of  FIG. 2 , the high pressure poppet valve  1184  will be closed and the low pressure poppet valve  1182  will be open to provide passage of hydraulic fluid when pressure Pr provided by way of pilots  1186 ,  1187 ,  1188  is relatively low. That is, when the pressure Pr in the rod side fluid connection  1140  is low, as in normal operation, fluid from the at least one existing pump  1156  will be directed to its operation  1158  through the open low pressure poppet valve  1182 , i.e., fluid from the cooling pumps  1160  will be directed from conduit  1200  through open poppet valve  1182  and conduit  1172  to the rear brakes  1166 . 
     Conversely, when the pressure provided by the pilots  1186 ,  1187 ,  1188  is increases, the low pressure poppet valve  1182  closes and the high pressure poppet valve  1184  opens. When the pressure Pr is relatively high, the high pressure poppet valve  1184  will be open to allow passage of hydraulic fluid and the low pressure poppet valve  1182  will be closed to prevent passage. That is, when pressure Pr in the rod side fluid connection  1140  is relatively high, as during an overrunning load situation, fluid from the at least one existing pump  1156  will be directed to the head chamber  1138  through the open high pressure poppet valve  1184 , i.e., fluid from the cooling pumps  1160  will be directed to the head chamber  1138  through conduit  1222 , open poppet valve  1184 , conduit  1214 , and head side fluid connection  1142  to supplement the flow from the first pump  1152 . 
     Turning now to  FIG. 4 , the same numbers preceded by the number 2XXX are utilized to identify the various elements. Those elements identified by such corresponding numbers in  FIG. 4  that are not explained in detail below may be the same or similar to the structure explained with regard to  FIGS. 2  and/or  3 .  FIG. 4  illustrates an example of a pilot valve  2180  in conjunction with a make-up valve  2184 . The pilot valve  2180  is of a spool type in this embodiment, while the make-up valve  2184  is of a poppet type. 
     In the implementation of  FIG. 4 , a spool  2230  is provided within a valve body  2232 , and biased to the illustrated position by spring  2202 . In the position illustrated, the spool  2230  is disposed to direct flow through port  2200  from an existing pump  2156  to port  2172  and on to an alternate operation  2158 , here, from a brake cooling pump  2160  to an oil cooler  2166 . In this way, pressure Pb is applied at port  2200 , pressure Pc is applied at port  2172 , that is, the pressure Pb from the existing pump  2156  is applied at port  2200 , and the pressure Pc from the alternate operation  2158  is applied at port  2172 . In order to shift the spool  2230  from the illustrated position against the force of the spring  2202  and existing flow through the valve body  2232 , a pilot signal of pressure Pr is applied to a spool  2230  at port  2186 . Thus, when pilot pressure Pr is relatively low, the spool  2230  will be disposed in the illustrated position, directing flow from the existing pump  2156  to the alternate operation  2158 . When pilot pressure Pr builds, however, the spool  2230  will shift from the illustrated position to cut off flow to the alternate operation  2158 , and direct flow to the port  2221 , through conduit  2222 , and on to make-up valve  2184 . It will be appreciated that, once in the shifted position, the pressure at port  2221  and in conduit  2222  will be the same as the pressure Pb entering the valve body  2232  at port  2200 . 
     In this way, pressure Pb is applied at port  2223  of the make-up valve  2184 . The outlet port  2214  of the make-up valve  2184  is open to the flow to the actuator (not illustrated in this embodiment). Consequently, the pressure applied at port  2214  is the pressure Ph from the first pump (not illustrated in this embodiment). As pressure Pb applied to make-up valve  2184  at port  2223  builds and eventually becomes greater than the force applied by the spring  2185  and pressure Ph, the make-up valve  2184  opens to allow flow to port  2214 . That is, when make-up valve  2184  opens, flow through valve  2180  from the existing pump  2156  is directed supplement flow to the cap chamber (not illustrated in this embodiment) during an overrunning operation. 
     Turning now to  FIG. 5 , the same numbers preceded by the number 3XXX are utilized to identify the various elements. Those elements identified by such corresponding numbers in  FIG. 5  that are not explained in detail below may be the same or similar to the structure explained with regard to  FIG. 3 .  FIG. 5  illustrates an example of a regenerative system wherein an accumulator  3156  is utilized as an additional source of pressurized fluid  3154  to supplement flow from a first pump  3152 . As in the embodiment of  FIG. 3 , the first pump  3152  directs fluid from a tank  3164  to the head chamber  3138  by way of a hoist valve  3150  and head side fluid connection  3142 . It is noted that the cooling pumps  3160  in this embodiment direct fluid to the oil cooler  3166 , but are not involved in the provision of supplemental fluid to the head chamber  3138 . 
     In the embodiment of  FIG. 5 , return flow from the rod chamber  3136  may be directed by rod side fluid connection  3140  through the hoist valve  3150  and conduit  3141  to the tank  3164 . Return flow from the rod chamber  3136  may alternatively or additionally be directed from rod side fluid connection  3140  through conduit  3186  and check valve  3185  to the accumulator  3156 . A flow limiter  3183 , illustrated here as a compensated orifice, may be disposed in the path of charge conduit  3186 . 
     In operation, supplemental flow from the accumulator  3156  may be may be directed to head side fluid connection  3142  by way of operation of valves  3192  and  3184 . Turning first to the operation of the valve  3184 , pressure Ph from head side fluid connection  3142  is applied to valve  3184  by way of conduit  3214 , while pressure Pr from rod side fluid connection  3140  as a result of flow from the rod chamber  3136  is applied to valve  3184  by way of pilot line  3188 . Generally speaking, when the pilot pressure Pr at pilot line  3188  is greater than pressure resulting from flow to the head chamber  3138 , valve  3184  will open to permit flow therethrough. 
     With valve  3184  in the open position, pressure Ph will be applied to one side of the valve  3192 , while pressure Pa from the accumulator  3156  will be applied to the other side of valve  3192 . When the pressure Ph from the valve  3184  applied to the valve  3192  drops, pressure applied at pilot line  3218  drops, allowing the valve  3192  to move under the force of spring  3220  from the normally closed position illustrated to an open flow position. With valve  3192  in the open position, fluid from the accumulator  3156  passes through the conduit  3222 , valve  3192 , valve  3184 , and conduit  3214  to the head side fluid connection  3142 , and on to the head chamber  3138  through port  3146 . Valve  3192  may be a pressure reducing valve such that valve  3192  reduces the pressure of fluid flowing from the accumulator  3156  before passing the fluid on to valve  3184 . It will be appreciated by those of skill in the art that valve  3184  and, consequently, valve  3192  will return to their respective closed position when the difference between the pressure Ph applied at conduit  3214  and the pressure Pr applied at pilot line  3188  reduces. 
     Industrial Applicability 
     The present disclosure is applicable to machines  100  that haul materials that are subject to massing together as one or more larger units. The disclosure may be particularly applicable to machines  100  which experience high forces that may result in overrunning and potential voiding in the head chamber of  138  of an actuator  102  during extension. The present disclosure may be applicable to such machines that are otherwise susceptible to rapid removal of such high forces, as may occur with “loafing” during unloading of a load. The systems and method disclosed herein may reduce or minimize the possibility of such loafing. The systems and method may also minimize or reduce the effects of such loafing on machinery components, as well as on the operator. 
     It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated. 
     Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. 
     Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.