Patent Publication Number: US-2023158715-A1

Title: Apparatus and method for manufacturing reactor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese patent application No. 2021-189289, filed on Nov. 22, 2021, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND 
     The present disclosure relates to an apparatus and a method for manufacturing a reactor. 
     Japanese Unexamined Patent Application Publication No. 2013-149841 discloses a method for manufacturing a reactor including a primary molding step and a secondary molding step. According to the technique described in Japanese Unexamined Patent Application Publication No. 2013-149841, a common mold can be used for both primary and secondary molding. 
     SUMMARY 
     A plurality of positioning pins for positioning a core are arranged in a mold included in an apparatus for manufacturing a reactor. If the positioning pin cannot withstand a resin pressure during molding, there is a problem that the core is cracked by the resin pressure during molding. On the other hand, when a high pressure is applied to the positioning pins so as to withstand the resin pressure, there is a problem that the core is cracked during positioning due to a dimensional variation of the core. 
     The present disclosure has been made in order to solve such a problem, and an object of the present disclosure is to provide an apparatus and a method for manufacturing a reactor capable of both absorbing a dimensional variation of a core and preventing deformation due to a resin pressure during molding. 
     In an example aspect of the present disclosure, an apparatus for manufacturing a reactor provided with a core includes:
         a mold including a cavity for housing the core, wherein   the mold includes a plurality of pins protruding into the cavity,   when the core is disposed in the cavity, at least one of the plurality of pins is not fixed, and each of the pins functions as a positioning pin, and   when a molded article is molded, the at least one pin is fixed, and each pin functions as a core support pin for supporting the core against a resin pressure during molding.       

     In another example aspect of the present disclosure, a method for manufacturing a reactor provided with a core includes:
         disposing the core in a mold including a cavity for housing the core; and   molding a molded article by using the mold, wherein   the mold includes a plurality of pins protruding into the cavity,   in the disposing of the core, at least one of the plurality of pins is not fixed, and each of the pins functions as a positioning pin, and   in the molding of the molded article, the at least one pin is fixed, and each pin functions as a core support pin for supporting the core against a resin pressure during molding.       

     According to the present disclosure, it is possible to provide an apparatus and a method for manufacturing a reactor capable of both absorbing a dimensional variation of a core and preventing deformation due to a resin pressure during molding. 
     The above and other objects, features and advantages of the present disclosure will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a schematic top view showing an overview of a mold of a manufacturing apparatus according to related art; 
         FIG.  2    is a schematic top view showing an overview of a mold of a manufacturing apparatus according to a first embodiment; 
         FIG.  3    is a schematic side view showing a configuration of the mold of the manufacturing apparatus according to the first embodiment; 
         FIG.  4    is a schematic side view showing the mold of the manufacturing apparatus during positioning according to the first embodiment; 
         FIG.  5    is a schematic side view showing the mold of the manufacturing apparatus when an upper mold is lowered according to the first embodiment; 
         FIG.  6    is a schematic side view showing the mold of the manufacturing apparatus during molding according to the first embodiment; 
         FIG.  7    is a schematic side view showing the mold of the manufacturing apparatus when a molded article is taken out according to the first embodiment; 
         FIG.  8    is a schematic side view showing a mold of a manufacturing apparatus during positioning according to the second embodiment; 
         FIG.  9    is a schematic side view showing a mold of the manufacturing apparatus when an upper mold is lowered according to the second embodiment; 
         FIG.  10    is a schematic side view showing the mold of the manufacturing apparatus during molding according to the second embodiment; 
         FIG.  11    is a schematic side view showing the mold of the manufacturing apparatus when a molded article is taken out according to the second embodiment; 
         FIG.  12    is a schematic side view showing a configuration of a mold of a manufacturing apparatus according to a third embodiment; 
         FIG.  13    is a schematic side view showing the mold of the manufacturing apparatus during positioning according to the third embodiment; 
         FIG.  14    is a schematic side view showing a mold of the manufacturing apparatus when an upper mold is lowered according to the third embodiment; 
         FIG.  15    is a schematic side view showing the mold of the manufacturing apparatus during molding according to the third embodiment; and 
         FIG.  16    is a schematic side view showing the mold of the manufacturing apparatus when a molded article is taken out according to the third embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Study Leading to Embodiments 
     First, the contents of the study conducted by the inventor of the present application will be described.  FIG.  1    is a schematic top view showing an overview of a mold  200  of a related manufacturing apparatus. The related manufacturing apparatus is an apparatus for manufacturing a reactor provided with a core  10 . A resin is injected around the core  10  inserted into the mold  200  and a coil mold  20  molded with a resin, and insert molding is performed. A reference sign R 1  indicates the resin included in the coil mold  20 . A hole h is an insertion hole for a bolt or the like, and is formed of a resin. A resin flow path during molding includes inner flow paths  31   a  and  31   b  flowing inside the core  10  and outer flow paths  32  flowing outside the core  10 .  FIG.  1    shows an internal state of the mold  200  during insert molding. 
       FIG.  1    shows a three-dimensional orthogonal coordinate system of XYZ for clarity of explanation. Note that a Z direction is a vertical direction. Therefore, the Z direction is a height direction. The resin is injected, for example, in a negative direction of a Z-axis. 
     The mold  200  includes a cavity for housing the core  10 . For example, a pair of E-shaped cores  10  are inserted into the cavity. The core  10  includes a base core  11 , a middle leg core  12 , and outer leg cores  13   a  and  13   b.  Hereinafter, when the outer leg cores  13   a  and  13   b  are not distinguished from each other, they may be referred to simply as the outer leg cores  13 . The middle leg core  12  and the outer leg core  13  project from the base core  11  in the same direction. A width of each of the outer leg cores  13  (e.g., a length thereof along the X-axis direction) is shorter than the width of the middle leg core  12 . In  FIG.  1   , an X-axis direction indicates a direction in which the base core  11  is extended, and a Y-axis direction indicates a direction in which the middle leg core  12  and the outer leg core  13  are extended. 
     The mold  200  includes pins P 11 , P 12 , P 13 , P 14 , P 21 , P 22 , and P 23  protruding into the cavity. The pins P 21  and P 22  are in contact with an end face of the core  10  on the negative direction side of the X-axis, and the pins P 11  and P 12  are in contact with an end face of the core  10  on the positive direction side of the X-axis. The pin P 23  is in contact with an end face of the core  10  on the negative direction side of the Y-axis, and the pins P 13  and P 14  are in contact with an end face of the core  10  on the positive direction side of the Y-axis. Since the resin is not injected into the parts of the core where the pins P 11 , P 12 , P 13 , P 14 , P 21 , P 22 , and P 23  are in contact with the core  10  during molding, windows corresponding to the pins P 11 , P 12 , P 13 , P 14 , P 21 , P 22 , and P 23  are formed in a molded article. 
     The pins P 11  to P 14  are connected to the mold  200  with springs S interposed therebetween and are not fixed. The pins P 21  to P 23  are fixed to the mold  200 . The springs S may be metal springs such as coil springs or leaf springs, fluid springs such as air springs, or springs made of an elastic material such as rubber or resin. Hereinafter, when the pins P 11  to P 14  are not distinguished from each other, they may be referred to simply as pins P 1 . Similarly, when the pins P 21  to P 23  are not distinguished from each other, they may be simply referred to as pins P 2 . The positions of the pins P 2  are held constant, and the positions of the pins P 1  may be displaced according to a pressure received from the core  10 . When the pins P 1  and P 2  are not distinguished from each other, they may be simply referred to as pins P. 
     Note that at least one of the pins P in contact with the end face of the core  10  on the positive direction side of the X-axis and the pins P in contact with the end face of the core  10  on the negative direction side of the X-axis may be connected to the springs S, respectively. Similarly, at least one of the pins P in contact with the end face of the core  10  on the positive direction side of the Y-axis and the pins P in contact with the end face of the core  10  on the negative direction side of the Y-axis may be connected to the springs S, respectively. 
     The pins P 11  and P 12  are displaced in the positive direction of the X-axis according to the length of the core  10  in the X-direction. The pins P 13  and P 14  are displaced in the positive direction of the Y-axis according to the length of the core  10  in the Y-axis direction. Thus, the pins P 11 , P 12 , P 13 , P 14 , P 21 , P 22 , and P 23  can position the core  10  while absorbing the dimensional variation of the core  10 . The outer leg core  13   b  of the core  10  is pressurized in the negative direction of the X-axis by the displacement of the pins P 11  and P 12 . 
     As described above, the resin flow paths during molding include the inner flow paths  31   a  and  31   b  passing through the inside of the core  10  and the outer flow path  32  passing through the outside of the core  10 . The inner flow path  31   a  passes around the coil mold  20 . When the resin is injected into the inner flow path  31   b  preferentially over the outer flow path  32 , the outer leg core  13   b  is pressurized in the positive direction of the X-axis by the resin of the inner flow path  31   b.  In order to prevent the deformation of the outer leg core  13  from the outside, the resin may be preferentially injected into the inner flow paths  31 . Normally, since the pressure applied by the pins P 11  and P 12  is smaller than the resin pressure, the deformation of the outer leg core  13   b  from the outside cannot be prevented, resulting in a problem that the core  10  is cracked. 
     Therefore, in order to prevent the core  10  from being cracked during molding, the outer leg core  13   b  needs to be strongly pressurized in the negative direction of the X-axis, for example, by increasing a spring coefficient of the springs S. However, if the pins P 11  and P 12  are configured to pressurize the outer leg core  13   b  strongly, the core  10  may be cracked when the core  10  is positioned. The inventor of the present application arrived at the present disclosure according to the embodiments based on the above study. 
     First Embodiment 
     Hereinafter, the present disclosure will be described through embodiments of the disclosure, but the disclosure according to the claims is not limited to the following embodiments. Further, not all of the configurations described in the embodiments are essential as means for solving the problem. 
     A manufacturing apparatus according to a first embodiment will be described below with reference to the drawings.  FIG.  2    is a schematic top view showing an overview of a mold  100  of the manufacturing apparatus according to the first embodiment. In the following description, differences of the mold  100  of the manufacturing apparatus according to the first embodiment from the mold  200  of the related manufacturing apparatus will be mainly described. 
     The upper drawing of  FIG.  2    shows a state of the mold  100  when the core  10  is disposed, and the lower drawing of  FIG.  2    shows the state of the mold  100  when a molded article is molded. A downward arrow between the upper and lower drawings indicate that the state of the mold  100  is changed. In the upper drawing of  FIG.  2   , the pins P 1  are connected to the springs S, respectively. However, in the lower drawing of  FIG.  2   , the pins P 1  are not connected to the springs S, respectively. Note that as described above, the pins P 1  indicate pins P 11  to P 14 . The upper drawing of  FIG.  2    shows that the pins P 1  are not fixed when the core  10  is disposed, and the pins P 1  are displaced by the pressure received from the core. When the core  10  is disposed in the cavity, each pin P functions as a positioning pin. 
     The lower drawing of  FIG.  2    shows that the pins P 1  are fixed to the mold  100  during molding. The pins P 11  to P 14  and P 21  to P 23  can prevent the core  10  from being deformed by the applied pressure indicated by the arrows. Note that the downward arrow indicates that the resin pressure is received from both of the two inner flow paths  31 . When a molded article is molded, each pin P functions as a core support pin for supporting the core  10  against the resin pressure during molding. 
     The state in which the pins P 1  are not fixed and the state in which the pins P 1  are fixed are switched according to whether the mold  100  is opened or closed. Since the core  10  is disposed with the mold  100  open, the pins P 1  are not fixed in the upper drawing of  FIG.  2   . Since the mold  100  is closed during molding, the pins P 1  are fixed in the lower drawing of  FIG.  2   . The specific configuration of the mold  100  will be described later. 
       FIG.  3    is a schematic side view of the mold  100  included in the manufacturing apparatus according to the first embodiment. Note that the manufacturing apparatus according to the first embodiment may include, in addition to the mold  100 , an opening/closing apparatus (not shown) for controlling opening/closing of the mold  100 , a resin injection apparatus (not shown), etc. 
     The mold  100  includes an upper mold  110  and a lower mold  120 . When the upper mold  110  is lowered, the mold  100  is closed, and when the upper mold  110  is raised, the mold  100  is opened. The upper mold  110  includes a wedge pressing pin  111  and a spring  112  extended in the Z-axis direction. 
     The wedge pressing pin  111  is connected to the upper mold  110  with the spring  112  extended and contracted in the Z-axis direction interposed therebetween. When the mold  100  is closed, the wedge pressing pin  111  pushes down a wedge  124  described later, puts the wedge  124  between the pin P 1  and a slide core block  122  described later to thereby fix the pin P 1 . The spring  112  imparts a force for pressing the wedge  124  to the wedge pressing pin  111 . A load of the spring  112  is larger than a load of the spring  125  described later. 
     The lower mold  120  includes a projection  121 , the slide core block  122 , a spring  123 , the wedge  124 , the spring  125 , the pin P 1 , and the spring S. The projection  121  has a projection in the Z-axis direction and is movable in the Z-axis direction. 
     The slide core block  122  is connected to the lower mold  120  with the spring  123  extended and contracted in the X-axis direction interposed therebetween, and is movable forward and backward in the X-axis direction. The slide core block  122  has a through hole into which the projection  121  can be inserted. When the projection  121  is inserted into the through hole, the slide core block  122  moves in the positive direction of the X-axis. When the projection  121  is retracted from the through hole, the slide core block  122  moves in the negative direction of the X-axis by an elastic force of the spring  123 . 
     The wedge  124  is connected to the slide core block  122  with the spring  125  extended and contracted in the Z-axis direction interposed therebetween. The wedge  124  has a wedge shape whose width (e.g., the length thereof along the X-axis direction) becomes narrower toward the negative direction of the Z-axis. The wedge  124  is retracted to a position where the wedge  124  does not interfere with the pin P 1  when the core  10  is disposed by an action of the spring  125  described later. During molding, the wedge  124  enters between the pin P 1  and the slide core block  122  to fix the pin P 1 . 
     The spring  125  floats the wedge  124  by an elastic force after the mold  100  is opened and the wedge pressing pin  111  is retracted after the molding is completed. Then, the pin P 1  returns to a state in which the pin P 1  is not fixed, that is, a state in which the pin P 1  can be displaced by a pressure. 
     The pin P 1  functions as a positioning pin when the core  10  is disposed. The pin P 1  functions as a core support pin for supporting the core  10  against the resin pressure during molding. A base end of the pin P 1  is connected to the slide core block  122  with the spring S extended and contracted in the X-axis direction interposed therebetween (such a spring is also referred to as a lateral spring). 
     The pin P 1  is extended from the base end thereof in the negative direction of the X-axis and in contact with an end surface of the core  10  on the positive direction of the X-axis. The pin P 1  is extended from the base end thereof in the positive direction of the X-axis. The pin P 1  has an inclined end surface that can be engaged with an end surface of the wedge  124  on the negative direction side of the X-axis. The length of the spring S may be set appropriately so that the pin P 1  and the wedge  124  do not engage when the wedge  124  is not pressed. 
     Since the pin P 1  is not fixed by the wedge  124  when the mold  100  is open, that is, when the upper mold  110  is raised, the spring S can absorb the dimensional variation of the core  10 . On the other hand, when the mold is closed, that is, when the upper mold  110  is lowered, the wedge  124  is pressed by the wedge pressing pin  111 , and thus the pin P 1  is fixed by the wedge  124 . Therefore, the manufacturing apparatus according to the first embodiment can both absorb the dimensional variation of the core  10  and prevent deformation of the core  10  due to the resin pressure during molding. 
     Next, a manufacturing method according to the first embodiment will be described in detail with reference to  FIGS.  4  to  7   .  FIG.  4    is a schematic side view showing the mold  100  during positioning. The core  10  is disposed in the lower mold  120  in a state where the upper mold  110  is raised. When the projection  121  is moved in the negative direction of the Z-axis, the slide core block  122  moves in the negative direction of the X-axis as indicated by the arrow. The core  10  is positioned by the pin P 1 . 
       FIG.  5    is a schematic side view showing the mold  100  when the upper mold  110  is lowered. The upper mold  110  is lowered as indicated by the arrow. The wedge pressing pin  111  starts pressing the wedge  124  in response to the lowering of the upper mold  110 . The force of the wedge pressing pin  111  pressing the wedge  124  may be appropriately configured so that the core  10  will not be broken. For example, the wedge pressing pin  111  may press the wedge  124  with a predetermined force. 
       FIG.  6    is a schematic side view showing the mold  100  during molding. When the lowering of the upper mold  110  is completed, a mold clamping force is applied to the mold  100 , and the pin P 1  is fixed by the wedge  124  and the wedge pressing pin  111 . Then, the wedge  124  is inserted between the pin P 1  and the slide core block  122 . When the resin is injected into the mold  100 , the core support pin P 1  is pressurized in the positive direction of the X-axis as indicated by the arrow. The wedge  124  converts the resin pressure into a force in the vertical direction, and the wedge pressing pin  111  presses the wedge  124  in the vertical direction. For example, the pin P 1  can be fixed by setting the spring coefficient of the spring  112  sufficiently high. 
       FIG.  7    is a schematic side view showing the mold  100  when the molded article is taken out. After the resin molding is completed, the upper mold  110  is raised as indicated by the upward arrow. By doing so, the wedge pressing pin  111  is retracted, and the wedge  124  floats by the spring  125 . Next, the slide core block  122  is moved in the positive direction of the X-axis by moving the projection  121  in the positive direction of the Z-axis, and the molded article is taken out. Note that a reference sign R 2  indicates a resin molded into a molded article. 
     The manufacturing apparatus according to the first embodiment performs positioning while absorbing the dimensional variation of the core. At this time, the pins P 1  can be displaced by the springs S. In the manufacturing apparatus according to the first embodiment, the pins P 1  are fixed by a wedge mechanism when a molded article is molded. Therefore, deformation of the core is reduced without moving the pins P 1  subjected to the resin pressure, and cracking of the core can be prevented. 
     Second Embodiment 
     Next, a manufacturing apparatus according to a second embodiment will be described with reference to  FIGS.  8  to  11   . Hereinafter, differences of the second embodiment from the first embodiment will be mainly described. A mold  100   a  of the manufacturing apparatus according to the second embodiment includes, in place of the spring  112 , an air cylinder  113  for vertically driving the wedge pressing pin  111 . A load applied by the air cylinder  113  is larger than a load applied by the spring  125 . 
       FIG.  8    is a schematic side view showing the mold  100   a  during positioning. First, the core  10  is disposed in the lower mold  120 . Then, the slide core block  122  is moved in the negative direction of the X-axis as indicated by the arrow, and the core  10  is positioned by the pin P 1 . 
       FIG.  9    is a schematic side view showing the mold  100   a  when the upper mold  110   b  is lowered. As indicated by the arrow, the upper mold  110   b  is lowered. When the lowering of the upper mold  110   b  is completed, a mold clamping force is applied to the mold  100   a.  At this point, the wedge  124  is not yet pressed by the wedge pressing pin  111 . 
     It is known that each part of the mold  100   a  is slightly deformed on the order of microns by clamping the mold  100   a.  Therefore, if the wedge pressing pin  111  presses the wedge  124  when the lowering of the upper mold  110   b  is completed, there is a possibility that the pin P 1  may push the core  10  and breaks it due to the deformation of each part. Therefore, the timing at which the lowering of the mold  100   a  is completed is shifted from the timing at which the wedge  124  is pressed. 
       FIG.  10    is a schematic side view showing the mold  100   a  during molding. After the lowering of the upper mold  110   b  is completed, the air cylinder  113  is operated to move the wedge pressing pin  111  in the negative direction of the Z-axis. When the mold  100   a  is closed and the wedge pressing pin  111  is lowered by the air cylinder  113 , the wedge  124  is pressed by the wedge pressing pin  111 . Thus, the wedge  124  is inserted between the pin P 1  and the wedge pressing pin  111 , and thus the positions of the pins P 1  are fixed. The air cylinder  113  may, for example, pressurize the wedge pressing pin  111  with a predetermined load. After that, the resin is injected into the mold  100   a,  and the wedge  124  converts the resin pressure into a force in the vertical direction. The core  10  is pressed by the wedge pressing pin  111  through the pins P 1  and the wedge  124 . 
       FIG.  11    is a schematic side view showing the mold  100   a  when the molded article is taken out. When the upper mold  110   a  is raised as shown by the arrow, the wedge pressing pin  111  is retracted, and the wedge  124  floats by the spring  125 . The upper mold  110   a  may be raised after the wedge pressing pin  111  is raised by using the air cylinder  113 . After the slide core block  122  is moved in the positive direction of the X-axis, a molded article is taken out. 
     The manufacturing apparatus according to the second embodiment uses the air cylinder to shift the timing at which the lowering of the mold is completed from the timing at which the pins P 1  are fixed by the wedge. This prevents the core from being cracked due to the deformation of the parts caused by the mold clamping force of the mold. 
     Note that an electric drive mechanism or a hydraulic drive mechanism may be provided in place of the air cylinder  113 . However, the drive mechanism shall be capable of withstanding the temperature of the mold  100   a.  Further note that, instead of driving the wedge pressing pin  111  in the vertical direction, a pin pressing member described later may be driven in the vertical direction. 
     Third Embodiment 
     Next, a manufacturing apparatus according to a third embodiment will be described with reference to  FIG.  12   . A mold  100   b  of the manufacturing apparatus according to the third embodiment includes an upper mold  110   b  and a lower mold  120   b.  Comparing  FIG.  3    with  FIG.  12   , the upper mold  110   b  does not include the wedge pressing pin  111 , and instead includes a pin pressing member  114 . The pin pressing member  114  presses a pin P 1   a  described later by closing the mold  100   b.  The pin pressing member  114  may be fixed to the upper mold  110   b.    
     Furthermore, the lower mold  120   b  does not include the wedge  124 , and the pin P 1  is replaced by the pin P 1   a.  The pin P 1   a  includes a contact surface that is in contact with a lower surface of the pin pressing member  114 . The pin P 1   a  is fixed to the mold  100   b  by a frictional force between the pin pressing member  114  and the pin P 1   a.  An upper surface of the pin P 1   a  may include, for example, a friction member. 
     In such a case, in a manner similar to the first embodiment, the dimensional variation of the core  10  can be absorbed by the springs S, and the deformation of the core  10  can be prevented by fixing the pin P 1   a  subjected to the resin pressure by the frictional force. 
     Next, a manufacturing method according to the third embodiment will be described with reference to  FIGS.  13  to  16   .  FIG.  13    is a schematic side view showing the mold  100   b  during positioning. The core  10  is disposed in a lower mold  120   b  in a state where the upper mold  110   b  is raised. When the slide core block  122  moves in the X-axis negative direction, the core  10  is positioned by the pin P 1   a.    
       FIG.  14    is a schematic side view showing the mold  100   b  when the upper mold  110   b  is lowered. As indicated by the arrow, the upper mold  110   b  is lowered. When the lowering of the upper mold  110   b  is completed, a mold clamping force is applied to the mold  100   b.  At this time, the pin pressing member  114  presses the upper surface of the pin P 1   a  in the negative direction of the Z-axis, and thus the position of the pin P 1   a  in the X-axis direction is fixed by friction. 
       FIG.  15    is a schematic side view showing the mold  100   b  during molding. A resin is injected into the mold  100   b,  and thus the pin P 1   a  receives the resin pressure in the direction indicated by the arrow. The pin P 1   a  receives a frictional force in the negative direction of the X-axis from the pin pressing member  114  and then fixed. 
       FIG.  16    is a schematic side view showing the mold  100   b  when the molded article is taken out. When the resin molding is completed, the upper mold  110   b  is raised as indicated by the upward arrow, and the pin pressing member  114  is retracted. Simultaneously with the retraction of the pin pressing member  114 , the pin P 1   a  returns to a state where it is supported displacably by the spring S. After the slide core block  122  is moved in the direction indicated by the rightward arrow, the molded article is taken out. 
     The manufacturing apparatus according to the third embodiment performs positioning by absorbing the dimensional variation of the core. At this time, the pin P 1   a  is supported displacably by the spring S. On the other hand, during molding, the pin P 1   a  is fixed by the frictional force, and the core can be prevented from being deformed and broken. 
     The first to third embodiments may be combined as appropriate. For example, in the third embodiment, the pin pressing member  114  may be driven by the air cylinder  113 . 
     Note that the present disclosure is not limited to the above-described embodiments, and may be suitably modified without departing from the spirit. 
     From the disclosure thus described, it will be obvious that the embodiments of the disclosure may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure, and all such modifications as would be obvious to one skilled in the art are intended for inclusion within the scope of the following claims.