Patent Publication Number: US-2010114370-A1

Title: Conveyance apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation application of PCT/JP2007/063125, filed on Jun. 29, 2007. 
    
    
     FIELD 
     The embodiment discussed herein is related to a conveyance apparatus that conveys a work piece in an assembly line from the upstream side to the downstream side based on a tact system. 
     BACKGROUND 
     There is known a conveyance apparatus that conveys a work piece placed at the most upstream point and sequentially assembled in an assembly line, from the upstream side to the downstream side based on a tact system for each assembly process. As one of this type of conveyance apparatus, there is an apparatus having such a structure that any number of conveyance robots may be linked according to the number of processes in an assembly line. In this kind of conveyance apparatus, one conveyance robot is provided for each of sequential assembly processes, and the conveyance robots simultaneously reciprocate so that work pieces present at the respective sequential assembly processes are conveyed at the same time in a single mechanism based on a tact system. Incidentally, an assembly line includes many assembly processes. Therefore, in the following description, the words “upstream side” and “downstream side” may be referred to as “upstream process” and “downstream process,” respectively, to clearly indicate the order. 
       FIG. 1 ,  FIG. 2  and  FIG. 3  are diagrams that illustrate a conventional conveyance apparatus  1 . 
       FIG. 1  and  FIG. 2  illustrate the conveyance apparatus  1  that includes three conveyance robots  10  each of which is provided for three sequential assembly processes. In particular, the conveyance apparatus  1  having an assembly line that includes nine assembly processes for producing a hard disk drive (hereinafter referred to as HDD) is illustrated in  FIG. 1  and  FIG. 2 .  FIG. 2  also illustrates how control units incorporated in the respective conveyance robots  10  of the conveyance apparatus  1  illustrated in  FIG. 1  operate in an interlock manner.  FIG. 3  illustrates an internal structure of the conveyance robot  10  illustrated in  FIG. 1 . 
     As illustrated in  FIG. 1 , each of the conveyance robots  10  is provided to handle three sequential assembly processes and includes a mechanism  10 A. The mechanisms  10 A of the respective conveyance robots  10  convey work pieces W 1  through W 9  by simultaneously reciprocating based on a tact system. When the mechanisms  10 A reciprocate, the work pieces W 1  through W 9  are sequentially conveyed from the upstream side to the downstream side. Illustrated on the left side in  FIG. 1  is the most upstream point of the assembly line. For example, when a housing case of a HDD is placed at the most upstream point, a component is incorporated into the housing case in each of assembly processes that are downstream processes when viewed from the process at the most upstream point. The work piece into which the components have been incorporated at the respective assembly processes is sequentially moved to the downstream assembly processes (post-processes), and the HDD is finally assembled. Incidentally, the conveyance apparatus in  FIG. 1  has such a structure that when the number of assembly processes is more than nine, another conveyance robot  10  may be added. 
     Here, a time sequence from time t 1  to time t 6  will be described by referring to  FIG. 1 . 
     In order to describe the time sequence of each of the conveyance robots  10  provided in the conveyance apparatus  1 , each of parts (a) to (f) of  FIG. 1  illustrates: the positions of the respective mechanisms  10 A provided in the respective conveyance robots  10 ; and the positions of the respective work pieces W 1  to W 9  at each of the times t 1  to t 6 . Incidentally, each of parts (a) to (f) in  FIG. 1  also illustrates arrows each of which indicates a direction in which the mechanism  10 A moves until the next time arrives. 
     First, at the time t 1  corresponding to the initial state, the mechanisms  10 A of the respective conveyance robots  10  are located at the respective positions illustrated in part (a) of  FIG. 1 . When a command comes from a controller  110 , which will be described later, in the state where the mechanisms  10 A are located at these positions, the action of each of the conveyance robots  10  begins under the control of each PLC  100  which will be described later. 
     Firstly, when a command comes from the controller  100  at the time t 1 , the mechanisms  10 A are moved in the directions indicated with the arrows illustrated in part (a) of  FIG. 1 . Subsequently, as illustrated in part (b) of  FIG. 1 , the mechanisms  10 A are located at the respective positions in part (b) of  FIG. 1  at the time t 2 . Next, at the time  3 , the mechanisms  10 A are moved upward as illustrated in part (c) of  FIG. 1  to lift the work pieces W 1  to W 9  on mounting stages  10 B. Further, at the subsequent time t 4 , the mechanisms  10 A are moved to the respective positions illustrated in part (d) of 
       FIG. 1  while keeping the work pieces W 1  to W 9  lifted. After the mechanisms  10 A are moved to the respective positions illustrated in part (d) of  FIG. 1 , i.e. every one of the work pieces W 1  to W 9  is moved to the subsequent downstream process, the mechanisms  10 A are moved downward to place the work pieces W 1  to W 9  respectively on the mounting stages  10 B of the subsequent downstream processes as illustrated in part (e) of  FIG. 1  at the subsequent time t 5 . Next, as illustrated in part (f) of  FIG. 1 , each of the mechanisms  10 A comes back to the initial position illustrated in part (a) of  FIG. 1  and thereafter, a series of conveying motions from part (a) to part (f) of  FIG. 1  are repeated until all the work pieces W 1  to W 9  reach the final process after conveyed. 
     Here, with reference to  FIG. 2 , there will be described how control units of the conveyance apparatus  1  operate in an interlock manner. 
     As illustrated in  FIG. 2 , PLCs (Programmable Logic Controllers)  100  are incorporated into the conveyance apparatus  1  illustrated in  FIG. 1 , as the control units. These PLCs  100  are linked by a network NW. Also, a controller  110  for providing commands to each of the PLCs  100  is connected to the network NW. Further, a touch panel  111  for operation is connected to the controller  110 . When a start button  1111  provided in the touch panel  111  is operated, the operation of the start button  1111  is transmitted to each of the PLCs  100 . Subsequently, under the control of the PLCs  100 , reciprocating motions of the mechanisms  10 A of the respective conveyance robots  10  are repeated, so that the work pieces W 1  to W 9  of the respective assembly processes are conveyed based on a tact system. Incidentally, a sequencer illustrated in  FIG. 2  is used as the PLC  100 . In  FIG. 2 , a word “CONNECTABLE” represents a fact that when another conveyance robot  10  is additionally connected, another PLC  100  for controlling this additional conveyance robot  10  may be connected to the network NW. 
     Further, provided inside the conveyance robot  10  illustrated in  FIG. 3  are: a conveyance motor M 1  for causing the mechanism  10 A of the conveyance robot  10  to reciprocate; and a lifting-lowering motor M 2  for causing the mechanism  10 A to lift and lower the work pieces W 1  to W 9 . Furthermore, although not illustrated in  FIG. 3 , there is provided a ball screw (not illustrated) extended along a horizontal direction; so that the mechanism  10 A linked to the conveyance motor M 1  is able to reciprocate. There is also provided a ball screw linked to the lifting-lowering motor M 2  and extended along a vertical direction in  FIG. 1 , so that the mechanism  10 A is lifted and lowered. 
     A driver unit DR is connected to these motors M 1  and M 2 . When a drive command is provided by the PLC  100  to the driver unit DR, the motors M 1  and M 2  are supplied with driving signals corresponding to the drive command provided by the PLC  100 , so that the motors M 1  and M 2  are rotated, which enables the mechanism  10 A linked to the ball screws (not shown) to move vertically and reciprocate. 
     Also, when causing the conveyance robots  10  to move vertically and reciprocate by giving a command to the driver units DR, the PLCs  100  are unable to allow the respective conveyance robots  10  to carry out interlocking movement unless the positions for lifting and lowering and the positions for reciprocating of the mechanisms  10 A of the respective conveyance robots  10  are known. Therefore, each of the PLCs  100  receives position information from encoders ENC 1  and ENC 2  of the motors M 1  and M 2 , respectively, thereby causing the motors M 1  and M 2  to stop or operate. 
     Note that in the conveyance apparatus described above, typically, when, for example, an operator has dropped a work piece from the mounting stage in any of the assembly processes, the operator pushes a temporary-stop button  100 S provided at the conveyance robot  10  (single temporary-stop button  100 S for single conveyance robot  10 ), thereby halting the conveyance robots  10  for all the remaining assembly processes. Subsequently, after carrying out a recovery work such as putting the dropped work piece back on the mounting stage, the operator allows all the conveyance robots  10  to resume the reciprocating movement. However, it is quite inefficient to stop the conveyance robots  10  of all the assembly processes at a time just because a trouble has occurred in any of the assembly processes. 
     Considering this inefficiency, it is conceivable to stop any of the conveyance robots by pushing the temporary-stop button  100 S and let the remaining conveyance robots keep operating. 
     However, there is a possibility that a collision might occur between the stopped conveyance robot and the conveyance robot in the upstream process and between the stopped conveyance robot and the conveyance robot in the downstream process. It is easy to avoid the collision by using, for example, a technique described in Japanese Patent Laid-open Publication No. H06-155186 or Japanese Patent Laid-open Publication No. H07-261841. However, the techniques described in these documents are not related to a conveyance robot and are unable to let, when at least one of conveyance robots is stopped, the remaining conveyance robots keep operating while avoiding collision. 
     SUMMARY 
     According to an aspect of the invention, a conveyance apparatus includes: 
     a plurality of conveyance robots each of which is provided at each of a plurality of sequential assembly processes and conveys, based on a tact system, a plurality of work pieces by simultaneously reciprocating the plurality of work pieces by using a single mechanism, the plurality of work pieces respectively existing for the plurality of sequential assembly processes and sequentially assembled on an assembly line after placed at a most upstream side of the assembly line; and 
     a plurality of control units respectively provided for the plurality of conveyance robots and control time sequences for reciprocating motions of the respective conveyance robots, 
     wherein the plurality of control units control the time sequences for the reciprocating motions of the respective conveyance robots in a linked manner, and 
     each of the plurality of control units controls the time sequence of a first conveyance robot among the conveyance robots and receives, from another control unit controlling the time sequence of a second conveyance robot among the conveyance robots, position information of the second conveyance robot positioned frontward in a moving direction of the first conveyance robot, thereby detecting presence of a risk of a collision with the second conveyance robot, and causing the first conveyance robot to act to avoid the collision when the risk of the collision is present. 
     The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram that illustrates a conventional conveyance apparatus; 
         FIG. 2  is a diagram that illustrates an internal structure of the conveyance apparatus illustrated in  FIG. 1 ; 
         FIG. 3  is a diagram that illustrates an internal structure of a conveyance robot of the conveyance apparatus illustrated in  FIG. 1 ; 
         FIG. 4  is a diagram that illustrates a conveyance apparatus according to an embodiment of the present invention; 
         FIG. 5  is a diagram that illustrates a flow of a program describing a procedure carried out by a PLC  100 P; 
         FIG. 6  is a diagram that illustrates actions taking place when the program in  FIG. 5  is run by a sequencer which is the PCL  100 P; 
         FIG. 7  is a diagram that illustrates the actions taking place when the program in  FIG. 5  is run by the sequencer which is the PCL  100 P; and 
         FIG. 8  is a diagram that illustrates a structure in which a recovery button  100 PR is added to the structure in  FIG. 4 . 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     An embodiment of the present invention will be described below. 
       FIG. 4  is a diagram that illustrates a conveyance apparatus  1 P according to an embodiment of the present invention. 
     The structure of the conveyance apparatus  1 P in  FIG. 4  is similar to that of the conveyance apparatus  1  in  FIG. 1 ,  FIG. 2  and  FIG. 3 , except that communication lines  1000  are added and a program running inside each PLC  100 P is different from that of the PLC  100 . 
     Each of the three PLCs  100 P illustrated in  FIG. 4  is a sequencer. These three sequencers are interconnected like those in  FIG. 2  by a network NW, and control a sequence of reciprocating motions of three conveyance robots  10  in conjunction with one another through communications via the network NW. Also, in the present embodiment, each of the three PLCs  100 P is connected, with communication lines  1000 , to two PLCs  100 P for controlling the two conveyance robots  10  next to and located on both sides of its own conveyance robot  10 . To these two PLCs  100 P, the PLC  100 P transmits the position information of the conveyance robot  10  controlled by this PLC  100 P. Further, each of the three PLCs  100 P operates such that the PLC  100 P for controlling the first conveyance robot  10  receives the position information of the second conveyance robot  10  positioned forward in the moving direction of the first conveyance robot  10 , from the PLC  100 P for controlling the second conveyance robot  10 . 
     In other words, in the structure illustrated in  FIG. 4 , the adjacent PLCs  100 P are connected to each other with the communication line  1000 , and encoder signals from encoders ENC 1  and ENC 2  (similar to those in  FIG. 3 ) are also transmitted to the PLC  100 P for controlling the conveyance robot  10  in the upstream process via the communication line  1000 . Incidentally, each of the PLCs  100 P may include a parallel data communication device or a serial data communication device. In either case, these communication devices are connected to each other via the communication line  1000 . 
       FIG. 5  is a diagram that illustrates a flow of a program describing a procedure carried out by the PLC  100 P. The processes in the flow illustrated in  FIG. 5  are repeatedly carried out by the sequencer  100 P which is the PLC. Now, the flow illustrated in  FIG. 5  will be described. 
     In step S 501 , each of the PLCs  100 P transmits a ready signal indicating that an internal communication device is operable to the PLC  100 P in the upstream process and the PLC  100 P in the downstream process. 
     Subsequently, in step S 502 , each of the PLCs  100 P reads a current position A based on an encoder signal from the encoder ENC in the conveyance robot  10  controlled by this PLC  100 P. Next, in step S 503 , current position information is transmitted to the PLC  100 P controlling the conveyance robot  10  in the upstream process. 
     Subsequently, in step S 504 , the PLC  100 P in the upstream process receives current position information B transmitted by the process in step S 502  of the PLC  100 P controlling the conveyance robot  10  frontward in the moving direction. However, at this point, there is a case where the current position information has not yet been transmitted from the PLC  100 P in the downstream process through the communication line  100  and thus, the PLC  100 P in the upstream process is unable to receive the current position information B. In this case, the current position information is received in step S 504  of the next cycle. Subsequently, in step S 505 , when the current position information B is received in the process at step S 504 , the PLC  100 P subtracts the current position information A of the conveyance robot controlled by this PLC  100 P from the current position information B and obtains a positional difference B−A. The positional difference B−A is a difference between the travel distances of the respective conveyance robots  10  when these respective conveyance robots  10  are reciprocating. Normally, the conveyance robots reciprocate in the same manner and thus the positional difference is zero. However, when the conveyance robot  10  in the downstream process has been stopped in response to the operation of its temporary-stop button  100 PS, the positional difference corresponds to a distance traveled by the conveyance robot in the upstream process during the time (50 msec. for two cycles) required for receiving the current position information from the PCL  100 P in the downstream process at step S 504 . Therefore, assuming the moving speed of the conveyance robot  10  is 1000 mm/sec., the determination criterion at step S 505  is set to be “50 msec.×1000 mm/sec.=50 mm”. The detailed description will be provided later when explaining  FIG. 6 . 
     Subsequently, in step S 506 , it is determined whether the positional difference is equal to or more than the criterion 50 mm. When it is determined that the positional difference is larger than 50 mm in step S 506 , the flow proceeds to “No”, and returns to step S 502  and the series of processes from step S 502  to step S 506  are repeated. At this point, the flow returns to step S 502  and the series of processes from step S 502  to step S 506  are repeated unless a not-ready signal is transmitted from the communication device of the PLC  100 P controlling the conveyance robot  10  positioned frontward in the moving direction in step S 506 . 
     In step S 506 , when it is determined that the positional difference is 50 mm or less, or a not-ready signal has been transmitted from the communication device of the PLC  100 P in the downstream process, the flow proceeds to “Yes” and the PLC  100 P in this flow causes its own conveyance robot  10  to stop or decelerate by controlling this conveyance robot  10  in step S 507 . 
     This completes the processing for avoiding a collision, and the processing for resuming the linked motions begins afterward. 
     The processes from step S 508  to step S 511  are the same as the processes from step S 502  to step S 505 , respectively. However, the determination process in step S 512  is different from the process in step S 507 . After repeating the processes from step S 502  to step S 506 , each of the PLCs then carries out the process in step S 507 . Subsequently, after repeating the processes from step S 508  to step S 512 , each of the PLCs carries out the process in step S 513  and then returns to step S 502  to repeat the processes from step S 502  to step S 505  again. 
     In the process at step S 508 , in a manner similar to the processes from S 502  to step S 506 , each of the PLCs  100 P reads a current position D based on encoder signals from the encoders ENC in the conveyance robot  10  controlled by the PLC  100 P in this flow and then, in the next step S 509 , this PLC  100 P transmits the current position information to the PLC  100 P controlling the conveyance robot  10  in the upstream process. In the subsequent step S 510 , the PLC  100 P receives the current position information E transmitted from the PLC  100 P controlling the conveyance robot frontward in the moving direction. In the next step S 511 , the PLC  100 P subtracts the current position information D of the conveyance robot  10  controlled by this PLC  100 P from the current position information E of the conveyance robot  10  positioned frontward in the moving direction, and obtains a positional difference E−D. 
     Subsequently, it is determined in step S 512  whether the positional difference is larger than a set value that is 25 mm in this example. When it is determined in step S 512  that the positional difference is smaller than 25 mm, the flow proceeds to “No” and returns to step S 508  to repeat the processes from step S 508  to step S 511 . When it is determined in step S 512  that the positional difference is 25 mm or more, the flow proceeds to “YES” and the conveyance robot  10  stopped or decelerated is caused to start moving in step S 513 . Afterwards, the flow returns to step S 502  to repeat the series of processes. Incidentally, in the process at step S 512 , the operation may be resumed assuming that the positional difference is zero, but the determination criterion is set as 25 mm assuming occurrence of a displacement corresponding to one cycle of the program. 
     By performing the processes in the flow of  FIG. 5  in this way, the PLC  100 P automatically carries out the processing for avoiding collision and the processing for recovery. Therefore, even if any of the conveyance robots  10  is stopped by the operation of its temporary-stop button  100 PS, the remaining conveyance robots  10  are allowed to keep reciprocating, and the stopped conveyance robot  10  also is allowed to start reciprocating in conjunction with these remaining conveyance robots  10  after a work piece is put on the stage. 
       FIG. 6  and  FIG. 7  are diagrams for explaining actions taking place when the program in  FIG. 5  is run by the sequencer which is the PCL  100 P. 
     In  FIG. 6 , a velocity curve of each of the conveyance robots  10  in the upstream and downstream processes controlled by the respective two PLCs  100 P is illustrated in the form of a line graph.  FIG. 7  illustrates that when the sequencer that is the PCL  100 P in the upstream process runs the program in  FIG. 5  thereby reciprocating the conveyance robot  10  controlled by this PCL  100 P, the position information of this PCL  100 P and the position information of the conveyance robot  10  positioned frontward in the moving direction are acquired with a displacement in between corresponding to one cycle. The vertical axis of the line graph illustrated in  FIG. 6  indicates the speed, while the horizontal axis indicates the time. 
     In an upper part of  FIG. 6 , there is illustrated the state of a change in the speed of the mechanism of the conveyance robot in the upstream side (i.e., upstream process) and a change in the speed of the mechanism of the conveyance robot in the downstream side (i.e., downstream process). 
     As described above, as long as all the conveyance robots are in the active state and reciprocating together, no collision occurs. However, when the conveyance robot  10  in the downstream side is stopped near a position T in the vicinity of the origin of its reciprocating motion in response to the operation of the temporary-stop button  100 PS, i.e. when the conveyance robot  10  in the downstream side is stopped at a position shifted by 150 mm from the origin of the reciprocating motion of the conveyance robot in the upstream side, the conveyance robot in the upstream side collides against the stopped conveyance robot. Therefore, the PLC  100 P in the upstream process acquires the position information of the conveyance robot  10  controlled by this PLC  100 P and the position information of the conveyance robot  10  positioned frontward in the moving direction (i.e., downstream process), thereby detecting the presence or absence of a collision between the conveyance robot  10  at a halt in the downstream process and the conveyance robot  10  in the upstream process. When there is a risk of occurrence of a collision, the PLC  100 P causes the conveyance robot  10  in the upstream process to carry out the processing for avoiding collision. 
     First, with reference to  FIG. 6 , there will be described motions of the conveyance robot  10  in the upstream side (upstream process) assuming that the conveyance robot  10  in the downstream process is stopped at the position T in the most upstream side. 
     Firstly, normal motions of the conveyance robot  10  in the upstream side will be described. 
     Under the control of the sequencer  100 P that has received an operation starting command from the controller  110  (see  FIG. 4 ) via the network NW, the mechanism  10 A of the conveyance robot  10  is first controlled to accelerate and reaches the maximum speed 1000 mm/sec. after 0.1 sec. to move 50 mm from the initial position. Subsequently, while maintaining the maximum speed 1000 mm/sec. for 0.17 sec., the mechanism  10 A moves 170 mm. Afterwards, the mechanism  10 A is controlled to decelerate for 0.1 sec. and then stops at a distance of 270 mm in total. 
     Here, for example, assume the conveyance robot  10  in the downstream process is stopped at the most frontward position in response to the operation of the temporary-stop button  100 PS. 
     In this case, the PLC  100 P in the upstream process detects a risk of occurrence of a collision in step S 506  of the program that is repeating the processes in the flow of  FIG. 5 . When the risk is present, the PLC  100 P carries out the process for stopping the conveyance robot in step S 507 . 
     As illustrated in  FIG. 7 , the time for one cycle (“one scan” in  FIG. 7 ) of the program of the sequencer  100 P is 25 msec. However, as illustrated in  FIG. 7 , there is a case in which after acquiring the current position information during the first cycle, the sequencer  100  obtains the position information at the time of running the program for the subsequent second cycle as previously described. 
     For this reason, when the sequencer  100 P performs the process for stopping, a maximum time difference of 25 msec.×2 (for two cycles)=50 msec. occurs, causing a positional difference: 50 msec.×maximum speed 1000 mm=50 mm between the travel distance of the conveyance robot in the upstream process and the travel distance of the conveyance robot in the downstream process. 
     Considering this fact, to determine the presence or absence of a collision in step S 506  when the program in  FIG. 5  is run by the sequencer  100 P, whether the conveyance robot in the downstream process is stopped or not is determined by setting 50 mm mentioned above as a criterion. 
     When the above-mentioned 50 mm is set as a criterion to determine whether to avoid a collision, even if the time for two cycles is required to obtain both pieces of position information, the conveyance robot of the upstream process is stopped with reliability before colliding against the conveyance robot in the downstream process. Also, when the above-mentioned 25 mm is set as a criterion to determine whether to carry out a recovery, the stopped conveyance robot is allowed to reciprocate in conjunction with the reciprocating motions of the remaining conveyance robots. 
     In other words, in the above-described conveyance apparatus, upon execution of the processes in the flow illustrated in  FIG. 5  by each of the PLCs (sequencers) serving as a control unit, at the time when one of the conveyance robots operating in conjunction with one another is stopped, the remaining conveyance robots are allowed to keep operating in a range where no collision occurs, while avoiding occurrence of a collision. Further, when the stopped conveyance robot becomes movable while avoiding a collision, the stopped conveyance robot is allowed to resume operation in conjunction with the remaining conveyance robots. 
     As described above, there is realized a conveyance apparatus capable of causing, at the time when one of conveyance robots operating in conjunction with one another is stopped, the remaining conveyance robots to keep operating in a range where no collision occurs, while avoiding occurrence of a collision. 
     Incidentally, since the above-described embodiment is based on the assumption that dropping of a work piece that is a small problem occurs, the embodiment has been described as having such a structure that operation is automatically resumed by providing only the temporary-stop button. However, a recovery button may be provided to resume the operation. 
       FIG. 8  is a diagram that illustrates a structure in which a recovery button  100 PR is added to the structure in  FIG. 4 . 
       FIG. 8  illustrates a modified example in which the recovery button  100 PR is provided to enable the conveyance robot  10 , which is stopped in response to the operation of the temporary-stop button  100 PS, to resume the operation in response to the operation of the recovery button  100 PR. 
     In this structure, even when, for example, a trouble a little more complicated than the above-described dropping of a work piece occurs in any of the conveyance robots  10 , the stopped conveyance robot  10  is allowed to resume the operation in conjunction with the other conveyance robots  10  by pressing the recovery button  100 PR, after pressing the temporary-stop button  100 PS and then resolving the trouble by taking some time. Incidentally, even in this modified structure, the flow in  FIG. 5  may be employed as it is. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiment of the present invention has been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.