Abstract:
A triple slide assembly for a three panel door system that mounts on a two track header and allows the panels to slide easily and sequentially with an interlocking function that provides a means to align the panels. The outer rails or panels each have an inward facing track to support rollers mounted to the middle rail or panel in an alternating configuration. The track and roller assembly interlocks the three panels and has stops, positioned in the ends of the inward facing tracks, keep the panels interlocked. The inward facing tracks and middle rail or panel remain aligned with the header when the outer panels are adjusted to align with adjacent door jambs to provide a smooth sliding operation. The triple slide assembly can be used for a six-door, center opening enclosure and for a five panel sliding assembly mounted on a three track header.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority from U.S. provisional application Ser. No. 60/478,072 filed on Jun. 11, 2003, incorporated herein by reference in its entirety. 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not Applicable 
   INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
   Not Applicable 
   NOTICE OF MATERIAL SUBJECT TO COPYRIGHT PROTECTION 
   A portion of the material in this patent document is subject to copyright protection under the copyright laws of the United States and of other countries. The owner of the copyright rights has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the United States Patent and Trademark Office publicly available file or records, but otherwise reserves all copyright rights whatsoever. The copyright owner does not hereby waive any of its rights to have this patent document maintained in secrecy, including without limitation its rights pursuant to 37 C.F.R. § 1.14. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention pertains generally to track mechanisms for sliding doors, and more particularly to a track mechanism for a tri-panel door assembly that uses a header with two tracks and has an interlocking function that allows the movement of an outer door to guide the middle door with a smooth sliding operation. 
   2. Description of Related Art 
   There are many applications for sliding panels or doors to an enclosure, and the use of two sliding doors allows access to one side of an enclosure at a time. Two sliding doors on an enclosure can provide an access opening up to about 50 percent of the enclosure opening or about the width of one door. 
   Tri-panel sliding doors are used to provide a larger access opening to an enclosure. Three sliding glass doors can provide an access opening up to about 66 percent of an enclosure opening or about the width of two doors. 
   In many applications an interlock device is used to keep the doors from sliding past each other and damaging handles racks, etc., attached to the doors. In conventional sliding panel assemblies, an interlocking function is achieved by overlapping the door stiles to provide the drawing mechanism. In other conventional systems, an interlocking protrusion or stop is installed on the stile of adjacent doors. However, the sliding operation is less than desirable with these devices. 
   Furthermore, the header of a conventional tri-panel door system requires three independent tracks, one for each door, to allow the doors to slide without interference or misalignment. This arrangement requires a wider, more expensive header and can also reduce the available area of a small enclosure. A three track header adds to the complexity of aligning each door with the adjacent jambs, aligning three doors with respect to each other, and interlocking the three doors. 
   Therefore, there is a need for a triple slide assembly with an interlocking function that allows the panels to slide easily, align easily and which does not require a wider, more expensive, three track header. 
   BRIEF SUMMARY OF THE INVENTION 
   The invention is a triple slide assembly for a three panel door system that mounts on a two track header and allows the panels to slide easily and sequentially with an interlocking function that provides a means to align the panels. Outer rails or panels each have an inward facing track to support rollers mounted to the middle rail or panel in an alternating configuration. The track and roller assembly interlocks the three panels and has stops, positioned in the ends of the inward facing tracks, to keep the panels interlocked. The inward facing tracks and middle rail or panel remain aligned with the header when the outer panels are adjusted to align with adjacent door jambs to provide a smooth sliding operation. 
   One embodiment of the invention is a triple slide assembly for sliding doors, having first and second track members, first and second rail members attached to the first and second track members respectively, a third rail member slidably supported by the first and second track members, where the rail members are adapted to receive an upper edge of a sliding door panel, and the track and rail assembly is adapted to be slidably received by a header member. 
   An aspect of the invention is where the rail members interlock. 
   A further aspect of the invention is where movement of an outer door panel received by the first rail member will guide a center panel received by the third rail member in the direction of travel of the outer door panel. 
   A still further aspect of the invention is where the header member conceals interlocking of the rail members. 
   Another aspect of the invention is a triple slide assembly for sliding doors, comprising a header member, a first rail member adapted to slidably engage the header member, a second rail member adapted to slidably engage the header member, and a third rail member adapted to slidably engage the first and second rail members, where the first and second and third rail members are each adapted to receive an upper edge of a sliding door panel. 
   A still further aspect of the invention is a triple slide assembly for sliding doors that comprises first and second track members, first, second and third rail members, where each rail member is adapted to receive an upper edge of a sliding door panel, and means for slidably coupling the track and rail members as an assembly adapted to be slidaby received by a header member, where the door panels received by the rail members interlock 
   Another aspect of the invention is a slide assembly for three sliding panels adapted to couple to a header having first and second header tracks that comprises first and second rail members adapted to slidingly couple to the first and second header tracks respectively, first and second track members adapted to couple to the first and second rail members respectively, a third rail member adapted to slidingly couple to the first and second track members, and where the third rail member is supported by the first and second track members. 
   A further aspect of the invention is where the first and second rail members are adapted to slidingly couple to the first and second header tracks with rollers. 
   A yet further aspect of the invention is where the third rail member is adapted to slidingly couple to the first and second track members with rollers. 
   Another aspect of the invention further comprises a plurality of stops coupled to the first and second track members, where the stops are positioned to guide the third rail member in the direction of movement of the first rail member or the second rail member. 
   A further aspect of the invention is where the first, the second and the third rail members support a door panel. 
   A still further aspect of the invention is where the alignment of the first and second rail members relative to the header is adjustable. 
   Another aspect of the invention is where the third rail member remains aligned with the header when the alignment of the first or the second rail members is adjusted. 
   A further aspect of the invention is where the first and second track members remain aligned with the header when the alignment of the first or the second rail members is adjusted. 
   A still further aspect of the invention is where the first and the second track members have a C shape cross section. 
   Another aspect of the invention is where the first and the second track members are straight. 
   Another embodiment of the invention is a slide door mechanism adapted to couple to a header member having first and second header tracks comprising first, second and third panels having an upper edge, first sliding means for slidably coupling the upper edge of the first and second panels to the first and second header tracks, second sliding means for slidably coupling the upper edge of said third panel, to the upper edge of the first and second panels, and where the third panel is supported by the first and second panels through the second sliding means. 
   Another aspect of the invention is interlocking means coupled to the first and second panels, where the interlocking means is configured to guide the third panel in the direction of movement of the first panel in response to movement of the first panel, and where the interlocking means is further configured to guide the third panel in the direction of movement of the second panel in response to movement of the second panel. 
   A further aspect of the invention is where the interlocking means is a plurality of stops mounted in the first and second track members. 
   A still further aspect of the invention is where the interlocking means is a plurality of overlapping protrusions coupled to the first, the second and the third panels. 
   A yet further aspect of the invention is where the upper edge of the first and second panels are concealed by the header. 
   Another aspect of the invention is where the first sliding means comprises a sliding member selected from the group consisting essentially of a roller, a bearing and a plastic slide. 
   A further aspect of the invention is where the second sliding means comprises a sliding member selected from the group consisting essentially of a roller, a bearing and a plastic slide. 
   A still further aspect of the invention is where the upper edges of the first panel, the second panel and the third panel comprise a rail. 
   Another embodiment of the invention is a slide door mechanism further comprising a fourth and fifth panels having an upper edge, where the fourth panel is adapted to couple to the first header track with the first sliding means, where the fifth panel is adapted to couple to the second header track with the first sliding means, third and fourth track members adapted to couple to the upper edge of the fourth and fifth panels respectively, a sixth panel, the sixth panel having an upper edge adapted to couple to the second sliding means, and where the sixth panel is supported by the third and fourth track members through the second sliding means. 
   Another aspect of the invention is a three door slide assembly comprising a header configured with first and second header tracks, first and second rail members adapted to slidingly couple to the first and second header tracks, first and second track members adapted to couple to the first and second rail members respectively, a third rail member adapted to slidingly couple to the first and the second track members, and where the third rail member is supported by the first and the second track members. 
   A further aspect of the invention is where the first and second rail members are interlocked to the third rail member by a plurality of stops mounted in the first and the second track members, and where movement of the first or the second rail member guides the movement of the third rail member. 
   A still further aspect of the invention is where the first, the second and the third rails members support a first, a second and a third door panel respectively. 
   Another aspect of the invention is where the first and the second door panels are interlocked to the third door panel by a plurality of overlapping protrusions mounted to the first and the second door panels, and where the first and the second door panels are further interlocked to the third door panel by a plurality of stops mounted to the first and the second track members. 
   A further aspect of the invention is where the first and the second door panels are interlocked to the third door panel by a plurality overlapping protrusions mounted to the first, the second and the third door panel. 
   A still further aspect of the invention is where the first and second track members are recessed in the first and the second door panels respectively. 
   Another aspect of the invention is where the alignment of the first and second rail members relative to the header is adjustable. 
   A further aspect of the invention is where the alignment of the third panel relative to the header remains fixed when alignment of the first or the second rail members is adjusted. 
   A yet further aspect of the invention is where the alignment of the first and second track members relative to the header remains fixed when alignment of the first or the second rail members is adjusted. 
   Another aspect of the invention is where the header is straight, and where the first and the second track members are straight. 
   Another embodiment of the invention is a center opening slide panel assembly adapted to couple to a header with a first track and a second track comprising a first panel member adapted to slidingly couple to the first header track, a first track member coupled to the first panel member, a second panel member adapted to slidingly couple to the second header track, a second track member coupled to the second panel member, a first middle panel member adapted to slidingly couple to the first track member and the second track member, where the first middle panel member is interlocked with the first panel member and the second panel member, a third panel member adapted to slidingly couple to the first header track, a third track member coupled to the third panel member, a fourth panel member adapted to slidingly couple to the second header track, a fourth track member coupled to the fourth panel member, a second middle panel member adapted to slidingly couple to the third track member and the fourth track member, where the second middle panel member is interlocked with the third panel member and the fourth panel member. 
   Another aspect of the invention is a plurality of stops mounted in the first, second, third and fourth track members, where the stops interlock the first middle panel member to the first and second panel member, and where the stops interlock the second middle panel member to the third and fourth panel member. 
   A further aspect of the invention is a plurality of protrusions mounted on the first, second, third and fourth panel members, where the protrusions interlock the first middle panel member to the first and second panel member, and where the protrusions interlock the second middle panel member to the third and fourth panel member. 
   A still further aspect of the invention is where alignment of the first, second, third and fourth panel members is adjustable relative to the header. 
   Another aspect of the invention is where alignment of the first middle panel member with the header remains fixed when the alignment of the first or second panel member is adjusted, and alignment of the second middle panel member with the header remains fixed when the alignment of the third or fourth panel member is adjusted. 
   Yet another aspect of the invention is a slide rail assembly adapted to couple to a header with a first track a second track and a third track comprising a first rail member adapted to slidingly couple to the first header track, a first track member coupled to said first rail member, a second rail member adapted to slidingly couple to the second header track, a second track member coupled to said second rail member, a third rail member adapted to slidingly couple to said first track member and said second track member, wherein said third rail member is interlocked with said first rail member and said second rail member, a third track member coupled to said second rail member, a fourth rail member adapted to slidingly couple to the third header track, a fourth track member coupled to said third rail member; and a fifth rail member adapted to slidingly couple to said third track member and said fourth track member; wherein said fifth rail member is interlocked with said third rail member and said fourth rail member. 
   Further aspects of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the invention without placing limitations thereon. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
     The invention will be more fully understood by reference to the following drawings which are for illustrative purposes only: 
       FIG. 1  is an assembled perspective view of a triple slide assembly according to the present invention with the rail and track portion shown in a partially extended position and shown separated from the header portion. 
       FIG. 2  is a partially exploded view of the triple slide assembly shown in  FIG. 1 . 
       FIG. 3  is an exploded view of the track and rail portion of the triple slide assembly shown in  FIG. 1  and  FIG. 2 . 
       FIG. 4  is a front view of two, triple slide doors on a two track header and configured to open in the center according to the present invention. 
       FIG. 5  is a cross section view of a three track header supporting a five rail, interlocked slide assembly, according to the present invention. 
       FIG. 6  is a schematic plan view of a three panel slide assembly with one stop in each track and stile protrusions on the outer panels according to the present invention. 
       FIG. 7  is a schematic plan view of the three panel slide assembly shown in  FIG. 6  with no stops in the tracks and six stile protrusions. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring more specifically to the drawings, for illustrative purposes the present invention is embodied in the apparatus generally shown in  FIG. 1  through  FIG. 7 . It will be appreciated that the apparatus may vary as to configuration and as to details of the parts, and that the method may vary as to the specific steps and sequence, without departing from the basic concepts as disclosed herein. 
     FIG. 1  illustrates an assembled perspective view of a triple slide assembly  10  according to the invention. In  FIG. 1 , a two track header  12  is shown in cut away view as the support for the triple slide assembly  10  with front header track  14  and rear header track  16  in the walls of header  12 . Three slider rails, front rail  20 , middle rail  22  and rear rail  24  are shown interlocked together. Front rail  20  has front track  30  facing middle rail  22  and rear rail  24  has rear track  32  facing middle rail  22 . Middle rail  22  is interconnected with rails  20 ,  24  through front track  30  and rear track  32 . Front rollers  34  support front rail  20  in header track  14  and rear rollers  36  support rear rail  24  in header track  16 . 
     FIG. 2  illustrates a partially exploded view of triple slide assembly  10  shown in  FIG. 1 . Referring to  FIG. 2 , middle rail  22  has left end  40  with a middle front roller  42  aligned with front track  30  and a right end  44  with a middle rear roller  46  aligned with rear track  34 . Middle front roller  42  rides in front track  30  attached to front rail  20 . Middle rear roller  46  rides in rear track  32  attached to rear rail  24 . In this configuration, middle rail  22  is supported on left end  40  by front rail  20  through track  30  and roller  42  and on the right end  44  by rear rail  24  through track  32  and roller  46 . This configuration of alternating rollers on front and rear tracks provides two direction movement of the middle rail  22  and couples front, rear tracks  30 ,  32  to middle rail  22  to allow simultaneous gliding, interlocking and adjustability. Angled slot  48  is provided for adjustment of middle rail  22  in relation to header  12 . In one embodiment, tracks  30 ,  32  and all the rollers are concealed within header  12 . In another embodiment, the width of header  12  is approximately 2.5 inches. This is in contrast to conventional three panel slide systems where a triple track header for the same application is about 3.25 inches. In a further contemplated embodiment, header  12  has one or both header tracks  14 ,  16  positioned facing the same direction or positioned on the exterior of header  12 . 
   Removable, spring-loaded stop clips  50  are shown positioned in each end of tracks  30 ,  32  to keep the panels interlocked and prevent rollers  42 ,  46  from rolling past the ends of tracks  30 ,  32 . In other, less preferable modes, plugs, screws or pins are used as stops. 
     FIG. 3  is an exploded view of the track and rail portion of the triple slide assembly  10  shown in  FIG. 1  and  FIG. 2 . Front and rear rails  20 ,  24  each have an angled adjustment slot  52  at one end to allow for fine adjustments and alignment of front, rear rail  20 ,  24  on header rollers  34 ,  36  and relative to header  12  to create a flush application between panels supported by rails  20 ,  24  and the adjacent jambs or walls. In one mode, slots  52  have an angle of about 30 degrees. Tracks  30  and  32  have horizontal slots  54  at one end that align with adjustment slots  52 . As rails  20 ,  24  are aligned with adjacent walls or jambs, tracks  30 ,  32  and middle rail  22  remains aligned with the header, thereby eliminating contradicting angles between tracks  30 ,  32  and allowing for smooth sliding operation of middle rail  22 . Alignment of middle rail  22  with header  12  (see  FIG. 2 ) or adjacent rails  20 ,  24  can be adjusted separately with roller  42  in adjustment slot  48 . 
   In a highly beneficial mode, hex screws  56  are used to attach tracks  30 ,  32  to rails  20 ,  24  and to attach rollers  34 ,  36 ,  42  and  46 . Hex screws  56  are also used to secure the alignment of rails  20 ,  24  in adjustment slots  52 ,  54  and alignment of middle rail  22  in adjustment slot  48 . Other fasteners as are known in the art are used in other modes. Once rollers  34 ,  36  are supported in header tracks  14 ,  16  in header  12  (see  FIG. 1 ), and rollers  42 ,  46  are supported in tracks  30 ,  32 , assembly  10  nests together as shown previously in  FIG. 1 . Stops  50  are inserted in each end of tracks  30 ,  32  to keep the assembly interlocked and from separating during use. Stops  50  also guide middle rail  22  in the direction of movement of front rail  20  or rear rail  24   
     FIG. 3  illustrates one preferred mode where rails  20 ,  22 ,  24  are configured with slots  58  to support panels such as glass or plastic shower doors, mirrors or panels such as for a closet or a display cupboard. In another preferred mode (not shown), rails  20 ,  22  and  24  are adapted to support door panels such as for walk in closets, pocket doors or room partitions. In a still further mode (not shown), rails  20 ,  22  and/or  24  are configured for movement by piston, motor, chain drive or other remote or automated means. Tracks  30 ,  32  are illustrated with a preferable “C” cross section as an anti-jump feature to keep rollers  42 ,  46  positively locked in tracks  30 ,  32 . In another mode (not shown), tracks  30 ,  32  have a “J” cross section and rollers  42 ,  46  with middle rail  22  can be lifted up and out of J tracks  30 ,  32 . In a further mode, rollers  42 ,  46  are configured in tandem trucks to ride on top and bottom of a track with a “J” cross section as an anti-jump feature. In a still further mode, tracks  30 ,  32  are configured as an “H” and rollers  42 ,  46  are configured in tandem trucks to ride on top and bottom of a track with an “H” cross section as an anti-jump feature. It is to be appreciated that the header and triple slide assembly shown in  FIG. 1  through  FIG. 3  can be configured for curved openings, for example a quarter round shower door opening, in accordance with the invention. In a curved configuration, each rail and track is positioned on the circumference of a circle projected from a common center point. 
     FIG. 4  illustrates an elevation view of an embodiment of the invention with opposing triple slide panels, generally designated  100 , that provide center access to an enclosure opening. Details of the triple slide assembly as previously described in  FIG. 1  through  FIG. 3  are omitted for clarity. Two track header  102  defines an enclosure and right panels  104 ,  106  and  108  are positioned on header  102  where front panel  104  is supported by a front header track and rear panel  108  is supported by a rear header track as shown previously in  FIG. 1  and  FIG. 2 . Middle panel  106  is supported by panels  104  and  108  as shown previously in  FIG. 1  through  FIG. 3 . Left panel doors  110 ,  112  and  114  are similarly positioned on header  102  with front panel  110  supported on the front header track and rear panel  114  supported on the rear header track. Front panel  110  is shown in an open configuration and can slide open to about the position of rear panel  114  positioned against the left jamb. In this center open position, the center access opening can be up to about two thirds of the full enclosure opening. Panels  108  and  114  are configured to slide towards the center to provide an access opening to each end of the enclosure. Note that the panels can be positioned all on one side to provide a side access opening of up to about two thirds of the enclosure opening. 
   In one mode, this configuration provides access to a display area such as a stage, vignette, bulletin board or white board. In another mode, this configuration provides access to a centrally positioned audio visual screen, such as a TV or projection screen, positioned behind panels  104 ,  106 ,  110  and  112  and access to equipment or media storage positioned behind panels  108  and  114 . In a further mode, a wardrobe is configured with a clothes rod behind panels  104 ,  106 ,  110  and  112  and shelves or drawers behind panels  108  and  114 . In a still further mode (not shown), center opening triple slide assembly  100  is configured as a double pocket door with panels  108  and  114  configured to slide into the side door pockets. Additional modes of this embodiment, such as for room dividers, privacy screens, cabinets, cupboards or pantries, are contemplated. Center opening triple slide assembly  100  can also be configured for a curved enclosure opening such as a stage or display area (not shown). 
   Although the panels in  FIG. 4  are illustrated to all be about the same width, slide assemblies with panels or rails of different widths (not shown) are contemplated for particular applications. 
     FIG. 5  illustrates a cross section view of a triple track header and five slider panels, generally designated as  200 , and in accordance with the present invention. In this illustration, left is the front of the assembly unless otherwise specified. Triple track header  202 , such as is used with conventional three slide panel systems, has front header track  204 , middle header track  206  and rear header track  208 . Five rails are shown in the assembly and are designated left to right, first rail  210 , second rail  212 , third rail  214 , fourth rail  216  and fifth rail  218 . First rail  210  is supported on front header track  204  by header roller  220 , third rail  214  is supported on middle header track  206  by header roller  222  and fifth rail  218  is supported on rear header track  208  by header roller  224 . First rail  210  has first inner track  230  facing third rail  214  and third rail  214  has second inner track  232  facing first inner track  230 . Rail  212  is supported by first roller  234  in first track  230  and second roller  236  in second track  232  configured as previously described in  FIG. 1  through  FIG. 3 . Rail  214  further has third inner track  240  facing fifth rail  218  and fifth rail  218  has a fourth inner track  242  facing third inner track  240 . Fourth rail  216  is supported by third roller  244  in third track  240  and by fourth roller  246  in fourth track  242 . In this configuration, each rail is interlocked with the adjacent rail as shown previously in  FIG. 3 . In one mode, stops (not shown) are positioned at each end of track  230 ,  232 ,  240 ,  242  to interlock the rails and guide the inner rails as shown previously in  FIG. 3 . Sliding all the rails to one side can provide an access opening up to a maximum of about 80% of an enclosure opening as compared to a maximum of about 66% for conventional triple side assemblies on a triple track header. 
   In one beneficial mode, this embodiment is contemplated for room partitions or pocket doors. In another mode, this embodiment is contemplated to provide a larger access opening to enclosures such as showers or rooms, or to accommodate wider access opening requirements, such as individuals with wheel chairs or walking aids. In a further mode, this embodiment provides a wider access opening to a restricted enclosure opening such as a cupboard, wardrobe or shower enclosure in an RV. 
     FIG. 6  illustrates a schematic plan view of an embodiment of a triple slide assembly  300  for door panels. Details of roller hangers and associated hardware are omitted for clarity. Front panel  302  has left edge  304  and right edge  306 . Front track  308  (shown in phantom for clarity) is shown recessed into panel  302  near the top edge. Header rollers  310  are positioned to mate with a front track of a two track header (as shown previously in  FIG. 1 ) Note that header rollers  310  may be mounted on a hanger or bracket near the centerline of the top edge of front panel  302  but are shown extended to the side for clarity. In this embodiment, the alignment of header roller  310  near left edge  304  is adjustable relative to panel  302  and interlocked with the left end of front track  308  as described previously in  FIG. 3 , but not shown here for clarity. Rear panel  312  has left edge  314  and right edge  316 . Rear track  318  (shown in phantom) is recessed into panel  312  near the top edge. Header rollers  320  are positioned to mate with a rear track of a two track header (as shown previously in  FIG. 1 ). In this embodiment, the alignment of header roller  320  near right edge  316  is adjustable relative to panel  312  and interlocked with the right end of rear track  318  as described previously in  FIG. 3 . Middle panel  322  has left edge  324  and right edge  326 . Front roller  328  is positioned near left edge  324  and mates to front track  308 . Rear roller  330  is positioned near right edge  326  and mates to rear track  318 . 
   In this embodiment, a protrusion (or handle)  332  is positioned on left edge  304  of front panel  302  and aligned to contact the left edge  324  of middle panel  322 . A stop  334  is positioned near the right edge  306  in front track  308 . Protrusion  332  eliminates a need for a stop near the left edge  304  of front track  308 . Similarly, a protrusion  336  is positioned near the right edge  316  of panel  312  and aligned to contact middle panel  332  at right edge  326 . A stop  338  is positioned near the left edge  314  in rear track  318 . Protrusion  336  eliminates a need for a stop near right edge  316  of rear track  318 . 
     FIG. 7  illustrates the triple slide assembly  300  for door panels shown in  FIG. 6  with no stops positioned in front track  308  or rear track  318 . A protrusion  340  is positioned near the left end  314  of rear panel  312  and facing middle panel  322 . Another protrusion  342  is positioned near right end  306  of front panel  302  and facing middle panel  322 . A protrusion  344  configured to contact protrusion  342  is positioned on the left edge of middle panel  322  facing front panel  302 . This configuration of protrusions keeps front roller  328  in front track  308  and front panel  302  interlocked with middle panel  322 . Similarly, a protrusion  346  is positioned near right end  306  of front panel  302 , facing middle panel  322  and configured to contact protrusion  340 . This configuration of mating protrusions keeps rear roller  330  in rear track  318  and rear panel  312  interlocked with middle panel  322 . In one mode, protrusions  340 ,  342 ,  344 , or  346  are configured as vertical gaskets for insulation, infiltration or as splash guards for a shower door enclosure. 
   In a further embodiment (not shown), protrusions  344 ,  346  are pins that mate with aligned closed end grooves (not shown) in adjacent panels to limit the travel of the middle panel and eliminate a need for protrusions  332 ,  342 ,  336  and  340  and for stops in tracks  308 ,  318 . In another embodiment (not shown), stops in tracks  308 ,  318  are replaced by chains, cords, bands or other interlocking means connected between front panel  302  and middle panel  322  and between rear panel  312  and middle panel  322 . In a still further contemplated embodiment (not shown), magnets oriented with opposing fields are attached to the edges of the panels to provide an interlocking force between adjacent panels without stops in the tracks or protrusions. 
   Although the description above contains many details, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for.”