Abstract:
A hot runner system having a melt distribution system that is reusable and reconfigurable to vary drop or nozzle locations to meet various design requirements. The melt distribution system includes a melt distributor in fluid communication with a melt source, at least one melt conduit in fluid communication with the melt distributor, and at least one nozzle in fluid communication with the at least one melt conduit. The hot runner system also includes a backing plate; a manifold plate detachably connected to the backing plate; a melt distribution system positioned between the backing plate and the manifold plate and having at least one nozzle associated therewith. The hot runner system may be configured and reconfigured to accommodate various drop or nozzle locations.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This is a continuation-in-part patent application of prior U.S. patent Ser. No. 12/039,824, filed Feb. 29, 2008, which is a continuation-in-part application of prior U.S. patent application Ser. No. 12/022,226, filed Jan. 30, 2008 now abandoned. 

   TECHNICAL FIELD OF THE INVENTION 
   The present invention relates generally to the field of injection molding and more particularly to a reconfigurable hot runner. 
   BACKGROUND OF THE INVENTION 
   A hot runner is utilized to transfer molten material, typically plastic resin, from an injection unit of an injection molding machine to at least one cavity defined in a pair of mold plates. A hot runner typically includes a manifold plate, a manifold housed in the manifold plate, and a backing plate that supports the manifold and manifold plate. The hot runner routes molten material from a central sprue, which connects to an injection unit on an injection molding machine, to a plurality of nozzles which inject the molten material into cavities in the mold. The hot runner divides the flow of molten material into several branches as it flows from the central sprue to the nozzles. 
   Referring now to  FIG. 1 , a cross-section of a hot runner  8  is shown. A manifold  10  is located between a manifold plate  12  and a backing plate  14 . The manifold  10  has one or more melt channels  18  that communicate the molten material from a sprue  16  connected to the manifold  10  at a central location. The hot runner  8  has nozzles  6  in fluid connection with the manifold  10 . 
   One limitation of this prior art hot runner  8  is that the manifold  10 , manifold plate  12 , and backing plate  14  must be replaced each time a new hot runner  8  is desired. The possibility of a reusable and reconfigurable manifold  10  (or melt distribution system), manifold plate  12 , backing plate  14  represents a significant potential cost and time saving benefit. In addition to these cost and time benefits, lead times for a new hot runner  8  can be considerable and with the present invention significantly reduces lead time. 
   Therefore, it would be desirable to provide a hot runner  8  that is reusable and reconfigurable. Specifically, it would be very desirable to provide manifolds  10  (or melt distribution systems), manifold plates  12 , and backing plates  14  that are reusable and reconfigurable to different drop locations. Further, it would be desirable to have nozzles  6  that are reusable as well. 
   The present invention is directed to meeting one or more of the above-stated desirable objectives. 
   SUMMARY OF THE INVENTION 
   One aspect of the present invention is to provide a hot runner system or components thereof that may be reused and reconfigured for various drop or nozzle location, or design requirements. 
   In accordance with the above aspect of the invention, there is provided a hot runner system comprising a manifold plate, a melt distribution system positioned adjacent said manifold plate and having at least one nozzle associated therewith, said at least one nozzle having an outside diameter, and wherein said manifold plate defines at least one plate slot therein, said at least one plate slot allowing said at least one nozzle to extend through said manifold plate and having at least a first lateral dimension substantially larger than said outside diameter of said at least one nozzle. 
   In accordance with the above aspects of the invention, the melt distribution system further includes a melt distributor for receiving melt from a source, at least one melt conduit in downstream fluid communication with the melt distributor, at least one nozzle in downstream fluid communication with and operatively connected to the at least one melt conduit, and wherein the at least one nozzle is movable from a first position to a second position in the at least one plate slot while remaining operatively connected to the at least one melt conduit and while the at least one melt conduit remains in fluid communication with the melt distributor. 
   In one embodiment of the melt distribution system, the melt distribution system comprises a melt distributor for receiving melt from a source, at least one melt conduit in downstream fluid communication with the melt distributor, at least one nozzle in downstream fluid communication with and operatively connected to the at least one melt conduit, and wherein the at least one nozzle is movable from a first position to a second position while remaining operatively connected to the at least one melt conduit and while the at least one melt conduit remains in fluid communication with the melt distributor. 
   In another embodiment of the melt distribution system, the melt distribution system comprises a melt distributor for receiving melt from a source, at least one melt conduit in downstream fluid communication with the melt distributor, at least one nozzle in downstream fluid communication with the at least one melt conduit, and wherein in non-use, the at least one melt conduit permits movement of the at least one nozzle from a first position to a second position without disconnecting the at least one nozzle from the at least one conduit of the melt distribution system. 
   These aspects are merely illustrative of the various aspects associated with the present invention and should not be deemed as limiting in any manner. These and other objects, aspects, features and advantages of the present invention will become apparent from the following detailed description when taken in conjunction with the referenced drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Reference is now made to the drawings which illustrate the best known mode of carrying out the invention and wherein the same reference numerals indicate the same or similar parts throughout the several views. 
       FIG. 1  is a cross-sectional view of a hot runner showing the manifold, manifold plate, backing plate, and nozzles as is known in the prior art. 
       FIG. 2  is a plan view of one embodiment of the present invention showing the manifold plate with nozzles extending therethrough of a hot runner. 
       FIG. 3  is a cross-sectional view of the hot runner of  FIG. 2 . 
       FIG. 4  is a top view of a manifold plate according to an embodiment of the present invention. 
       FIG. 5  is a cross-sectional view of a hot runner according to an alternate embodiment of the present invention. 
       FIG. 6  is a bottom view of a manifold plate according to another embodiment of the present invention. 
       FIG. 7  is a bottom view of a manifold plate according to another embodiment of the present invention. 
       FIG. 8  is a cross-sectional view of a system according to another embodiment of the present invention. 
       FIG. 9  is a cross-sectional view of a system according to yet another embodiment of the present invention. 
       FIG. 10  is a cross-sectional view of a partial hot runner according to another embodiment of the present invention showing a nozzle insert in the manifold plate for a hot tip nozzle system. 
       FIG. 11A  is a cross-sectional view of a partial hot runner according to yet another embodiment of the present invention showing the nozzle insert and the piston cylinder insert in a first position. 
       FIG. 11B  is a cross-sectional view of a partial hot runner according to another embodiment of the present invention showing the nozzle insert and the piston cylinder insert in a second position, illustrating the resulting variance in nozzle positions between  FIG. 11A  and  FIG. 11B . 
       FIG. 12A  is a plan view of a manifold plate showing both the external geometry of the nozzle insert as well as a plurality of nozzle bore locations therethrough. 
       FIG. 12B  is a plan view of a manifold plate showing both the external geometry of the nozzle insert as well as a plurality of nozzle bore locations therethrough. 
       FIG. 13A  is a plan view of a manifold plate showing a plurality of nozzle inserts each having an insert slot and illustrating a plurality of positions of the nozzle therein. 
       FIG. 13B  is a cross-sectional view of the embodiment of  FIG. 13A  illustrating the insert slot of the nozzle insert. 
       FIG. 14  is a top view of a manifold plate according to an embodiment of the present invention which uses dowel holes adjacent to an insert slot to positively locate a nozzle. 
       FIG. 15  is a cross-sectional view of a reconfigurable hot runner in one position; 
       FIG. 16  is a cross-sectional view of a reconfigurable hot runner in another position. 
   

   DETAILED DESCRIPTION 
   In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. For example, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention. 
     FIGS. 2-7  illustrate a hot runner system  206  or parts and portions thereof according to a first embodiment of the present invention. The hot runner system  206  includes a manifold  110 , having manifold melt channels  112  therethrough for molten material to travel from a sprue  120  to nozzles  114 . The manifold  110  is surrounded and supported by a backing plate  116  and a manifold plate  118 . The manifold  110  is, in effect, “sandwiched” between the backing plate  116  and the manifold plate  118 . 
   Referring now to  FIG. 8 , the manifold  110  and nozzles  114  may be located in at least a portion of the manifold plate  118  that is either inserted or mounted to the mold plates (not shown) with the backing plate  116  taking the form of a mold plate (considered as part of the mold rather the hot runner). In another embodiment illustrated in  FIG. 9 , the backing plate (not shown) is eliminated and a machine platen  308  is used to contain the hot runner. Those of skill in the art will appreciate that the present invention is equally suitable for use with any of these different structural arrangements. 
   As can be seen in  FIG. 5 , the sprue  120  delivers melt to the manifold melt channels  112  of the manifold  110 . Melt then passes through to the nozzles  114 , where it is delivered to each gate of the mold (not shown). 
   As can be seen most clearly in  FIGS. 3 and 5 , each nozzle  114  protrudes through and extends out of the manifold plate  118 . In prior art hot runner systems as shown in  FIG. 1 , a plate bore  24  is provided in the manifold plate  12  to accommodate each nozzle  6 , and the plate bore  24  is sized to match, with some clearance, the outside diameter of the nozzles  6 . In one embodiment disclosed herein, the manifold plate  118  is provided with plate slots  124 . For example as shown in  FIG. 4 , these plate slots  124  are provided with a first lateral dimension—the width—that matches, again, with some clearance, the outside diameter of the nozzles  114 . However, the plate slots  124  are provided with a second lateral dimension—the length—significantly longer than the diameter of the nozzles  114  such that the nozzles  114  may be positioned in multiple locations along that slot length, thus providing the desired positioning flexibility. The length of the plate slots  124  may utilize any number of dimensions and is limited only by the nozzle configuration used in the hot runner system and thermal considerations. 
   While an elongated slot has been previously described, it is contemplated as being within the scope of the present invention to use expanded openings in a variety of configurations.  FIGS. 6 and 7  illustrate a number of non-limiting examples including a multi-leg slot  202 , and an L-shaped slot  204 . Thus, the term “plate slots” is intended to be non-limiting as to the shape of the enlarged opening contemplated by the present invention. The rounded ends or corners of such shapes obviously being intended to accommodate the rounded diameter of the nozzles  114 . 
   It is typical in a hot runner system  206  for dowels  126  to be used to position the manifold  110 , and consequently the nozzles  114 , relative to the manifold plate  118  as is shown in  FIGS. 3 and 5 . These dowels  126  are frequently positioned between the nozzles  114  such that they do not directly relate to the plate bores or in the case of the present invention, plate slots  124 . However, in an alternate embodiment of the present invention illustrated in  FIG. 4 , an additional multi-position positive locating mechanism may be incorporated in the plate slots  124  previously described. In one version of this embodiment, a plurality of dowel holes  128  are provided along the perimeter of the plate slots  124  to accommodate additional dowels  130  associated with each individual nozzle  114 . The plurality of dowel holes  128  allow positive locating of the nozzles  114  relative to the plate slots  124  in the multiple positions within the plate slots  124 . 
   In another version of this embodiment, screws  132  are utilized as the positioning device rather than dowels  130 . In this version, a plurality of screw through holes  134  are positioned along the perimeter of the plate slots  124 , and the screws  132  are inserted into those holes  134  from outside of the manifold plate  118  and into a threaded hole (not shown) associated with each nozzle  114 . 
   In yet another embodiment of the present invention, the hot runner system  206  has nozzles  114  of the hot tip style configuration  415 . In this embodiment, the hot runner system  206  has a nozzle insert  400  used to locate each of the nozzles  114  within the manifold plate  118 . As illustrated in  FIG. 10 , the manifold plate  118  has at least one manifold plate cavity  405  to accept at least one nozzle insert  400 , the nozzle insert  400  having a nozzle bore  410  therethrough for installation of said nozzle  114 . The nozzle bore  410  is sized precisely to locate the nozzle  114  on its diameter to ensure exact alignment relative to the mold (not shown); however, the nozzle bore  410  may be located at a plurality of positions within the nozzle insert  400  to match the mold gate or location. 
   With the hot tip style configuration  415  in  FIG. 10 , the nozzle insert  400  need only be installed in the manifold plate  118 , whereas in the case of a valve gate style configuration  420 , as shown in  FIG. 11 , at least one piston cylinder insert  425  is also required to be installed in the backing plate  116 . The backing plate  116  has at least one backing plate cavity  435  to accept at least one piston cylinder insert  425 , the at least one piston cylinder insert  425  having a cylinder bore  440  therein for installation of a piston cylinder  445 , required to control actuation of a valve stem  430 . The at least one piston cylinder insert  425  is sized to fit the backing plate cavity  435 , and may have a plurality of external geometries  455  to match a plurality of internal geometries  465  of the backing plate cavity  435 . The at least one piston cylinder insert  425  may also be plumbed with a plurality of conduits  450  necessary to provide a driving force to actuate said valve stem  430 . 
   The interchangeability of a plurality of nozzle inserts  400  in a manifold plate cavity  405 , or at least one piston cylinder insert  425  in a backing plate cavity  435 , renders said manifold plate  118  and said backing plate  116  reusable when married to a plurality of molds (not shown) as the nozzle  114  can be located at a plurality of locations as illustrated in  FIGS. 11A and 11B  by dimension ‘X’. 
   As illustrated in  FIGS. 12A and 12B , the nozzle insert  400  may have a plurality of external geometries  455  to match a plurality of internal geometries  465  of the manifold plate cavity  405 . Additionally, within the nozzle insert  400 , the nozzle bore  410  may be installed in a plurality of lateral positions thus offering flexibility of positioning a nozzle  114  within the manifold plate  118  by replacing the nozzle insert  400 . 
   An extension of the aforementioned embodiment is illustrated in  FIG. 13A  wherein the nozzle insert  400  has at least one insert slot  460  which allows the nozzle  114  to extend through the nozzle insert  400 . In this embodiment, the insert slot  460  is provided with a first lateral dimension—the width—that matches, again, with some clearance, the outside diameter of the nozzle  114 . However, the insert slot  460  is provided with a second lateral dimension—the length—significantly longer than the diameter of the nozzle  114  such that the nozzle  114  may be positioned in a plurality of locations along the length of the insert slot  460 , thus providing the desired positioning flexibility. The length of the insert slot  460  may utilize any number of dimensions and is limited only by the configuration of the nozzles  114  and thermal considerations. Additionally, the nozzle insert  400  may be rotated within the manifold plate cavity  405  allowing for yet another variation of positioning of the axis of the nozzle  114 . A cross sectional view of a hot tip style configuration  415  shown in  FIG. 13B  shows the nozzle  114  as it is engaged in an insert slot  460  of  FIG. 13A . 
   While an insert slot  460 , which is elongated, has been previously described, it is contemplated as being within the scope of the present invention to use expanded openings in a variety of configurations. Referring back to  FIGS. 6 and 7 , a number of non-limiting examples including a multi-leg slot  202 , and an L-shaped slot  204  are illustrated and may be interpreted for the same use within the nozzle insert  400  itself. Thus, the term “insert slot”  460  is intended to be non-limiting as to the shape of the enlarged opening contemplated by the present invention. Again, the rounded ends or corners of such shapes obviously being intended to accommodate the rounded diameter of the nozzles. 
   In  FIG. 14 , yet another embodiment of the present invention illustrates that an additional multi-position positive locating mechanism may also be incorporated in the nozzle insert  400 , and more specifically, in the insert slot  460  previously described. In one version of this embodiment, a plurality of dowel holes  128  are provided along the perimeter of the insert slot  460  to accommodate additional dowels  130  associated with each individual nozzle  114 . The plurality of dowel holes  128  allow positive locating of the nozzle  114  relative to the insert slot  460  in multiple positions within the insert slot  460 . 
   In yet another version of this embodiment, screws  132  are utilized as the positioning device rather than utilizing a dowel  130 . In this version, a plurality of screw through holes  134  are positioned along the perimeter of the insert slot  460 , and the screws  132  are inserted into said through holes  134  from the outside of the nozzle insert  400  and into a threaded hole (not shown) associated with each nozzle  114 . 
   Turning now to yet another embodiment of the present invention,  FIGS. 15 and 16  illustrate the hot runner system  206  with a melt distribution system  500  that can be reused and reconfigured to accommodate various drop or nozzle  114  locations. The previous discussions dealt with manifold plates  118  and backing plates  116  that provided the flexibility of varying the location of the drops or nozzles  114 . The following discussion will describe the melt distribution system  500  that complements the manifold plates  118  and the backing plates  116  that are adjustable, reconfigurable, and reusable, thereby providing a complete hot runner system that provides the flexibility of varying drop or nozzle  114  locations. Therefore, it will become apparent to those skilled in the art after reading the following description that this embodiment encompasses a hot runner system  206  that is fully reconfigurable and reusable to different drop or nozzle  114  locations. 
   In this embodiment, the melt distribution system  500  has a melt distributor  502  that is used in place of the sprue  120  previously described. In addition, the melt distribution system  500  has a melt conduit  504  for each drop or nozzle  114 . The melt conduits  504  in this embodiment replace what is referred to as the manifold  110  in the previously described embodiments. The melt conduits  504  operatively and fluidly connect the melt distributor  502  to nozzle headers  556  of the nozzles  114  of the melt distribution system  500 . The melt distribution system  500  also includes outlets  544  that are operatively connected to a first end  548  of the melt conduit  504 , and the melt distributor  502 . The melt distribution system  500  also includes inlets  546  that are operatively connected to a second end  550  of the melt conduit  504 , and the nozzle headers  556 . Non-limiting embodiments of how the inlets  546  and the outlets  544  are attached to the melt distributor  502 , melt conduits  504 , nozzle headers  556  are described in more detail hereinafter. Those having ordinary skill in the art will understand that the inlets  546  and the outlets  544  are just one example of fittings that may be used to connect the melt conduits  504  to the melt distributor  502  and nozzle headers  556 . In another embodiment, for example, first ends  548 , and second ends  550  of the melt conduit  504  are soldered, brazed, welded, or affixed directly to the melt distributor  502  and nozzle headers  556 . Those having ordinary skill in the art will appreciate that the number of inlets  546  and the number of outlets  544  will preferably coincide with the number of the melt conduits  504 . In summary, the main components of the melt distribution system  500  include the melt distributor  502 , the outlets  544 , the melt conduit  504 , the inlets  546 , the nozzle headers  556 , and the nozzles  114 . 
   The nozzle headers  556  are removably and adjustably mounted between the manifold plate  118  and the backing plate  116 , and more specifically between the nozzles  114  and the backing plate  116 . Spacers  590  and screws  560  are used to firmly position the nozzles  114  and nozzle headers  556 . The nozzles  114  are operatively mounted to the nozzle headers  556  in much the same way that nozzles  114  are operatively mounted to manifolds  110  as is known by those having ordinary skill in the art, which includes but is not limited to sliding connections, screwed-in connections, and mechanically fastened connections. In an alternative embodiment, each nozzle  114  and nozzle header  556  pair are one-piece or a unitary structure. The nozzle headers  556  are used to direct the flow of molten material from the melt conduit  504  to the nozzles  114 , which is typically, but not required, at a 90 degree offset. The nozzle headers  556  are movable between the backing plate  116  and the manifold plate  118 . This allows the nozzle headers  556  and thus the nozzles  114  to be moved to various locations. For example in  FIG. 16 , the nozzle headers  556 , nozzles  114 , and melt conduits  504  are placed in a fully extended position. Thereafter for example, the nozzle headers  556 , nozzles  114 , and melt conduit  504  may be moved into one of the “relaxed” or not fully extended positions (hereinafter referred to as “intermediate positions”). The intermediate positions are any position between the melt distributor  502 , and the nozzles  114  in the fully extended position. 
   Those having ordinary skill in the art will appreciate that the melt distribution system  500  described with respect to  FIGS. 15 and 16 , having the movable nozzle headers  556  and nozzles  114  along with the reconfigurable melt conduit  504 , may be used with the flexible plate systems (i.e., manifold plates  118  and backing plates  116  having means for varying drop or nozzle  114  locations) described with respect to  FIGS. 2-14 . For example in the embodiment described with regard to  FIG. 4 , the plate slots  124  are provided with a first lateral dimension—the width—that matches with some clearance, the outside diameter of the nozzles  114 , and a second lateral dimension—the length—significantly larger than the diameter of the nozzles  114  such that the nozzles  114  may be positioned in multiple locations along that slot length, thus providing the desired positioning flexibility. The melt distribution system  500  described with respect to  FIGS. 15 and 16 , having the movable nozzle headers  556  and nozzles  114  along with the reconfigurable melt conduits  504 , may be moved along the length of the second lateral dimension of the plate slots  124  to accommodate the desired drop or nozzle  114  location. Those having ordinary skill in the art will appreciate that the foregoing provides a melt distribution system  500  that can be reused and reconfigured to accommodate various designs having varying drop or nozzle  114  locations such as those locations along the second lateral dimension (length) of the plate slots  124  in  FIG. 4 . 
   In another non-limiting example, the melt distribution system  500  discussed in relation to  FIGS. 15 and 16  may be used with the multi-leg slot  202  and the L-shaped slot  204  discussed with respect to  FIGS. 6 and 7 , respectively. It should be noted that the previously described elongated slots or openings are non-limiting examples. The melt distribution system  500  may be used with other slots, shapes of slots, and expanded openings in a variety of configurations. 
   In another non-limiting example, the melt distribution system  500  discussed in relation to  FIGS. 15 and 16  may be used with the nozzle inserts  400  described with respect to  FIGS. 10 ,  12 A, and  12 B. Thus, when the nozzle inserts  400  are installed in a plurality of lateral positions, the melt distribution system  500  including the nozzle headers  556 , nozzles  114 , and the melt conduits  504  may be moved or adjusted to accommodate the drop or nozzle  114  locations. 
   In another non-limiting example, the melt distribution system  500  discussed in relation to  FIGS. 15 and 16  may be used with the nozzle inserts  400  having the insert slots  460  therein described with respect to  FIGS. 13A , and  13 B. The insert slots  460  are provided with a second lateral dimension—the length—significantly larger than the diameter of the nozzles  114  such that the nozzles  114  may be positioned in a plurality of locations along the length of the insert slots  460 , thus providing the desired positioning flexibility. The length of the insert slots  460  may utilize any number of dimensions and is limited only by the configuration of the nozzles  114  and thermal considerations. Additionally, the nozzle inserts  400  may be rotated within the manifold plate cavity  405  allowing for yet another variation of positioning of the nozzles  114 . Thus, when the insert slots  460  location are selected from the plurality of lateral positions, the melt distribution system  500  including the nozzle headers  556 , nozzles  114 , and melt conduit  504  may be moved or adjusted to accommodate the drops or nozzles  114  location. 
   It should be noted that the aforementioned examples are not meant to be limiting but rather to give examples of how the melt distribution system  500  allows for movement of the nozzles  114  to various gate locations. Obviously, one melt distribution system  500  may be used to accommodate various backing plates  116  and manifold plates  118  having different nozzle  114  locations instead of purchasing a manifold  110  and associated nozzles  114  for each and every set of backing plate  116  and manifold plate  118  configurations having different gate locations. 
     FIG. 16  illustrates the melt conduits  504  in a fully extended position. With regard to  FIG. 15 , the melt conduits  504  are shown in two of the intermediate positions. In the intermediate positions, the melt conduits  504  may have a generally S-shaped configuration, C-shaped configuration, U-shaped configuration, or other shaped configuration for accommodating various lengths of the melt conduits  504  required for movement into the fully extended position as is shown in  FIG. 16 . The melt conduits  504  are bendable or flexible for movement from one position to another (i.e., from the fully extended position to any one of the intermediate positions or vice versa). 
   In one embodiment of the melt conduits  504 , the melt conduits  504  may be electrically heated high temperature and pressure Teflon core hoses, such as the Electraflo II, Series D Hoses and specifically Model DTM Standard Hose Core sold by Diebolt &amp; Company, who is located at 17 Charles Street, Old Lyme, Conn. 06371. 
   The melt conduits  504  may be permanently attached or removably attached to the melt distributor  502  and nozzle headers  556 . With regard to the removably attached embodiment, the inlets  546  have first threaded ends  554  for mating with threaded ends  558  of the nozzle headers  556 . The outlets  544  have first threaded ends  552  for mating with threaded ends  586  of the melt distributor  502 . The inlets  546  have second threaded ends  564  for mating with threaded ends  568  of the melt conduits  504 . The outlets  544  have second threaded ends  562  for mating with the threaded ends  566  of the melt conduits  504 . The threaded ends  566 ,  568  of the melt conduits  504  are threaded onto the second threaded ends  562 ,  564  of the outlets  544  and the inlets  546 , respectively. 
   Other objects, features and advantages of the present invention will be apparent to those skilled in the art. While preferred embodiments of the present invention have been illustrated and described, this has been by way of illustration and the invention should not be limited except as required by the scope of the appended claims and their equivalents.