BACKGROUND OF THE INVENTION

Technical Field

The present invention relates to a sliding door system adapted for use in a doorway to a refrigerated storage room or the like.

Background Art

Insulated high speed sliding doors for sealing an opening or doorway between a refrigerated or freezer space and other areas of a warehouse are known in the art. Such doors generally include a header assembly spaced above the doorway, first and second side sections spanning the distance between the header assembly and the floor of the doorway, a support structure for supporting the panels making up the door, and a motor system for moving the panels between an open and a closed position. The sealing function of such doors is often inadequate, leading to leakage from the refrigerated or freezer compartment, which in turn leads to wasted energy. One source of this leakage is over the top of the panels in the closed position. Various means have been used to prevent this leakage, but none have been entirely successful. Leakage around the side of the panels is also a problem. Generally, a barrier is provided between the wall adjacent the doorway and the panel that projects perpendicularly away from the wall. In the closed position, the barrier extends beyond the edge of the panel to prevent leakage around the panel. When the panel is moved toward the open position, however, the barrier is still obstructing the door. The barrier must thus be made of a collapsible material that can be forced into a position between the wall and the moving panel to allow passage of the panel. The friction caused by such a system tends to slow down the door. As a result, a higher

torque motor must be used to achieve the same door speed.

High door speed is very desirable since fork lift trucks repeatedly pass through these door systems at high speeds.

Such doors often include two panels that are moved in opposite directions to open and close the door. Such systems suffer from misalignment of the panels at closing.

This results from a swaying of the panels into and out of the doorway as the panels are moving toward the closed position. If the doors are misaligned in the closed position, leakage through the resulting gap will occur.

SUMMARY OF THE INVENTION The present invention is directed towards overcoming one or more of the problems with existing sliding door systems described above.

In one embodiment of the present invention, a door system for a doorway into a controlled environment such as a refrigeration or freezer unit is provided. A door frame is provided which includes a header assembly mounted adjacent to and along a top section of the doorway. The system also includes first and second side frame sections extending from the floor to the header assembly. The door frame provides an enclosed area adjacent to the doorway. A pair of panels are provided having a combined width that is larger than the doorway. The panels are movable between an open and a closed position, and each includes a secured side and a free side. A flexed header sealing means is also provided, that is fixed to the header assembly. The flexed header sealing means is spring- biased so as to always maintain a sealing contact with the panels. A means for moving the panels between an open position and a closed position is also provided. The door system also includes a bottom sealing means attached to the bottom of the panels to prevent leakage from the controlled environment under the panels. Further, the door system includes a lateral sealing means. This lateral sealing means is attached between the secured end

of each panel and the wall in the enclosed space between the doorway and the side section closest to the panel to which the lateral sealing means is attached. The lateral sealing means thus prevents leakage around the panels. The lateral sealing means also prevents leakage through the header assembly in the space adjacent to the panels, when in the closed position, by extending above the height of the panels into the header assembly. The door system also includes a pair of sealing noses, one on each panel. The sealing noses run the length of the free side of the panels. The sealing noses each include a magnetic means for aligning the panels as they approach the closed position. One of the sealing noses includes a sealing flap to cover the gap between the panels in the closed position. Thus the gap between the panels is sealed when they are in the closed position.

DESCRIPTION OF THE DRAWINGS For a more complete understanding of the invention, reference is made to the drawings, wherein:

Fig. 1 is a perspective view of one embodiment of the sliding door system showing the panels in the closed position.

Fig. 2 is a perspective view of the sliding door system showing the panels in the open position.

Fig. 3 is an exploded perspective view of the sliding door system of the first embodiment.

Fig. 4 is a sectional view showing the trolley/track system. Fig. 5 is a top plan view of the belt and motor system.

Fig. 6 is a side sectional view of the sweep attached to the bottom of the panels.

Fig. 7 is a top sectional view of the panel, the fanfold curtains and the nose seals.

Fig. 8 is a side sectional view of the panels and the flexed header sealing means.

Fig. 9 is a top sectional view of the door system in the closed position.

Fig. 10 is a perspective view of a spring steel section. Fig. 11 is a perspective view of the flexed header sealing means.

Fig. 12 is a top sectional view of the door system in the open position.

Fig. 13 is a perspective view of the single panel embodiment of the present invention.

Fig. 14 is a perspective view of the single panel door system in the open position.

Fig. 15 is a top sectional view of the single panel.

Fig. 16 is a top sectional view of the single panel system in the closed position.

Fig. 17 is a top sectional view of the bi-parting door system in a freezer application.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and more particularly to Fig. 1, a preferred embodiment of the sealed door system 20 according to the present invention is shown, and its structure will be generally described. The sealed door system 20 is adapted to be installed adjacent to a doorway formed in the wall W separating a controlled environment such as a refrigerated space from a non- controlled space in a warehouse. The unique features of the door system 20 allow it to effectively seal the doorway when in the closed position. The system 20 is particularly suitable for use in a facility wherein forklift trucks or similar material handling equipment repeatedly pass through the doorway under normal working conditions. Since the door is sealed in the closed position, leakage is at a minimum, and less energy is wasted. The door is also adapted, however, to be capable of rapidly opening for an approaching forklift, and of rapidly closing and sealing once the forklift is passed.

Referring to Fig. 1, the door system 20 includes a door means. In the present embodiment, the door means is a pair of panels 25, 26 that are designed to cover the entire doorway when in the closed position. The panels 25, 26 are made of insulating material and their combined width is larger in width than the doorway. The panels 25, 26 are attached to and supported by a header assembly 28. The header assembly 28 is secured proximate to the top of the doorway, and is supported by a pair of upright, substantially parallel side sections 29, 30. The side sections 29, 30 are secured to opposite sides of the doorway and extend from the header assembly 28 to the floor. From Fig. 2, which shows the panels 25, 26 in the open position, the position of the side sections 29, 30 relative to the doorway and panels 25, 26 can be seen.

The location of the side sections 29, 30 allows for the panels 25, 26 to move to a position where they not obstructing any of the doorway in the fully open position.

Returning to Fig. 1, the door system 20 also includes a lateral sealing means. The lateral sealing means are located on the sides of the panels 25, 26 closest to their respective side sections 29, 30. Each of the lateral sealing means is a curtain, as at 35, 36 made of a moisture-resistant material, and formed into a fanfold shape. One end of the curtain 35 is attached to the wall between the side section 29 and the secured side of the panel 25. The other side is attached to the secured side of the panel 25, with the other curtain 36 being similarly attached. The secured side of each panel 25, 26 is the side to which the curtains 35, 36 are attached, while the other side of each panel is the free side. With the panels 25, 26 in the closed position, the curtains 35, 36 prevent leakage of cold air around the panels 25, 26 from the refrigerated section behind the door. Leakage between the two panels 25, 26 is prevented by means of a sealing nose 38. The sealing nose 38 is included on both panels 25, 26. In Fig. 2, the sealing nose 38 on panel 26

can be seen. The sealing nose 38 is made of moisture resistant material and is attached to the free side of each panel. It includes both a magnetic means for insuring alignment of the two panels 25, 26 in the closed position and a sealing flap 39 to cover the gap between the two panels 25, 26 in the closed position. Leakage under the panels 25, 26 is prevented by a bottom sealing means in the form of a sweep 40. The sweep 40 is a piece of water resistant material attached to the bottom of the panels 25, 26 that extends all the way to the floor. Leakage over the panels 25, 26 is prevented by a flexed sealing means, not shown in Figs. 1 and 2. As will be discussed in greater detail below, the flexed sealing means is disposed in the header assembly 28, and runs along the length of the header assembly 28. The flexed sealing means is located such that it maintains a sealing contact with the panels 25, 26 regardless of their position. The curtains 35, 36 shown in Fig. 1 extend above the panels 25, 26 and in to the header assembly 28. This extension of the curtains 35, 36 prevents cold air from leaking out of the header assembly 28 in that area when the panels 25, 26 are in the closed position. Thus, with the panels 25, 26 in the closed position, the doorway is fully sealed and leakage is prevented. The mechanical operation of the door system will now be described in greater detail with reference to Fig. 3, which shows an exploded view of the invention according to the present embodiment. The header assembly 28 includes a rear framework 50, on which is mounted a supporting member 52. The supporting member 52 is attached to the rear framework 50 by means of gussets 54. As can be seen more clearly from Fig. 4, the supporting member 52 has suspended from it a track means 56. Illustratively, the track means 56 is an I beam that spans the distance between the two side sections 29, 30 of the door system. Engaging the track, and movable longitudinally along the I beam track 56 are a plurality of trolleys 60.

According to the present embodiment, each panel has one trolley 60 associated with it. As can be seen from Fig. 4, each trolley 60 is of like construction, and includes a generally u-shaped body 62, having a pair of upwardly extending leg sections 64, and a bail section 66, the bail section subtending the lower flange of the I beam track 56. Each leg 64 has a segment 68 which is offset towards the web of the I beam track 56. The inner surface of each offset segment 68 has rotatably mounted thereon a roller 70 which is in rolling contact with the upper surface of the lower flange of the I beam track 56 which projects laterally from the web. Mounted on the underside of the bail section 66 is a downwardly facing clip 72. The clip 72 is designed to attach the trolley 60 to a panel 25, 26 as will be described below.

The features common to each panel 25, 26 will be described in relation to one of the panels only, but it will be understood that both panels 25, 26 have the same features. Returning to Fig. 3, the panel 25 is provided with a supporting track 80 across the top edge. The supporting track 80 is illustratively a metal sleeve designed to snugly fit over the top edge of the panel 25. The supporting track 80 may be affixed to panel 25 by means of a hex screw or the like. The supporting track 80 serves to give the panel 25 lateral support. The supporting track 80 is also permanently attached to the bottom of a trolley 60 by the clip 72. Fig. 4 shows that the clip 72 is designed to engage the supporting track 80 in a fixed manner. Thus, movement of the trolley 60 causes movement of the panel 25 to which the supporting track 80 is attached.

Movement of the panels 25, 26 between the open and closed position may be effected by a belt 84, and a motor drive assembly. In Fig. 3, the motor drive assembly is comprised of the motor 86, the drive pulley 88 and the idle pulley 90. The motor 86 is illustratively a reversible D.C. motor having a plurality of operating

speeds. The drive pulley 88 is fixedly attached to, and rotates with the motor 86 about a vertical axis. According to the present invention, the motor 86 is mounted in an inverted position in the header assembly 28. This allows greater flexibility in the placement of the door system 20, since the header assembly 28 can be placed without need to allow for clearance above it for the motor 86. That is, the motor 86 does not extend beyond the frame of the door system 20 as defined by the side sections 29, 30 and the header assembly 28. The idle pulley 90 is attached to the header assembly by means of a secured spindle. The idle pulley 90 is freely rotatable about the spindle, and the spindle and the vertical axis about which the drive pulley 88 turns are parallel. The continuous friction belt 84 is stretched between the drive pulley 88 and the idle pulley 90. Movement of the panels 25, 26 is effected by securing the trolleys 60 to the continuous friction belt 84, and driving the motor 86. This is done by means of pressure plates 94. The belt 84 is secured between the pressure plate 94 and the trolley 60 on one side.

The arrangement of the trolleys 60 and the belt 84 can be seen in Fig. 5. Since the two legs 95, 96 of the belt 84 move in opposite directions, and the panels 25, 26 must move in opposite directions, each trolley 60 is attached to a different leg of the belt 84. Assuming Fig. 5 is a top view of the belt and motor drive assembly, clockwise motion of the drive pulley 88 would correspond to the panels 25, 26 moving from the closed position to the open position. The leg 95 of the belt 84 will be moving to the left, as will the panel 25 attached to it. Similarly, the leg 96 of the belt 84 will be moving to the right as will the panel 26.

The present embodiment also includes sensing and control mechanisms for controlling the motion of the panels 25, 26. In Fig. 3, a support rod 100 is shown attached to the underside of the supporting member 52.

Spaced along this support rod 100 are a pair of limit switches 102. The limit switches 102 are of conventional design, and are tripped by passage of the trolley 60. In this way, a control electronics, not shown, but located in proximity to the doorway, is given a signal representative of the position of the panel 25. This allows the control electronics to change the speed of the motor 86, and to provide for braking as the panels 25, 26 approach either the fully open or the fully closed position. One skilled in the art will appreciate that this sensing and control mechanism is not limited to limit switches, nor to a single type of electronic control. On the contrary, a variety of position sensing means may be used with a variety of control means. The mechanical means for moving the panels between the open and closed position offers several advantages. As noted above, the use of a motor 86 in an inverted position allows for tighter clearance above the header assembly 28. Further, because of the use of the track/trolley system, the projection of the header assembly away from the doorway is smaller than in conventional systems. This allows not only for reduced weight of the system, but also allows the door (here the panels 25, 26) to be located in closer proximity to the doorway being covered. This in turn allows the doorway to be effectively sealed according to the present invention.

The means by which the present invention provides for sealing of the doorway will now be described in reference to the preferred embodiment, as shown in Fig. 3. The sealing offered by the door system 20 prevents leakage from the refrigerated unit it encloses, thus saving energy. At the same time, the door system 20 offers effective opening and closing operation as shown in the above description of the mechanical movement system. One aspect leading to the sealing offered by the door system 20 is the composition of the door panels 25, 26. Each

panel is made of a low temperature core, illustratively polyvinylchloride (PVC) , surrounded by 2 layers of insulating material, illustratively Reflectex brand insulating material. This core is enclosed in a casing of 16 oz. hypalon moisture resistant material. This construction of each panel gives excellent thermal characteristics along with light weight. Further, this construction yields semirigid panels that are capable of maintaining a planar shape when moving between the open and closed positions, but that are deformable when outside force is applied. According to the present embodiment, the panels 25, 26 also include windows 25a, 26a that are properly insulated. The windows 25a, 26a allow for enhanced viewing of both the contents of the refrigerated compartment, and any possible obstructions beyond the doorway.

Leakage around the outer sides of the panels 25, 26 is prevented by a lateral sealing means. In Fig. 3, the lateral sealing means are the fanfold curtains 35, 36 extending from each panel 25, 26. The fanfold curtains 35, 36 are of similar design. Each curtain is, illustratively a sheet of 35 oz. hypalon, having a height larger than the height of the doorway, and a width equal to the width of the panel to which it is attached. Beading is sewn to the fanfold curtains 35, 36 at spaced intervals in order to achieve the fanfold effect. Each fanfold curtain is then secured between the wall adjacent the doorway and the secured edge of the panel to which it is attached. The curtain 35 is secured to the wall by means of a pressure strap 106 as secured, for example, by rivets. By securing the curtains 35, 36 to the wall in this fashion, lateral leakage along the wall is prevented. In the present embodiment, the place on the wall where the curtains 35, 36 are attached is selected such that the curtains will be stretched the maximum amount when the panels 25, 26 are in the closed position. Thus, when the panels 25, 26 are in the closed position, the curtains 35,

36 prevent leakage around the outside of the panels 25, 26. According to the present invention, the curtains 35, 36 also serve to prevent leakage in the area adjacent to the panels 25, 26 in the header assembly 28, as will be discussed in detail below.

Leakage below the panels is prevented by a bottom sealing means attached to the bottom of the panels 25, 26. As can be seen from Fig. 1, the height of the panels 25, 26 is not sufficient to completely cover the doorway in the fully closed position. The sweeps 40 make up for this by extending from the bottom of the panels 25, 26 to the floor. A side sectional view of sweep 40, is shown in Fig. 6. The top portion of the sweep, shown at 41, is permanently attached to the bottom of the panel 25. The top portion is illustratively 35 oz. hypalon material. The bottom portion 42 of the sweep 40 extends from the top portion 41 to the floor, and is also made of 35 oz. hypalon. According to the preferred embodiment, the bottom portion 42 is attached to the top portion 41 by means of a hook and loop fastener such as the Velcro brand fastener. This allows for replacement of the bottom portion 42 in the event of undue wear on the bottom portion 42. In an alternative embodiment, the entire sweep 40 may be a single piece of hypalon. Returning to Fig. 1, it can be seen that the sweeps 40 prevent leakage under the panels 25, 26. Further, leakage under the fanfold curtains 35, 36 is prevented by their length, since they have lengths that are larger than the door and extend to the floor. When the panels 25, 26 are in the closed position, leakage between them is prevented by a sealing nose configuration. The sealing nose configuration also provides for alignment of the panels 25, 26 in the closed position. As mentioned above in reference to Fig. 3, the supporting track 80 across the top of the panels 25, 26 prevents lateral movement of the panels. However, the panels 25, 26 are susceptible to a limited amount of

swaying motion into and out of the doorway as they are moving. If this swaying is not accounted for, the panels

25, 26 may be out of alignment in the closed position, resulting in undue leakage. To prevent this, each panel 25, 26 is provided with a nose seal 110, 111 as can be seen in Fig. 3. The nose seals 110, 111 run the length of the free side of the panels 25, 26 and provide an extended perpendicular mating surface. Each nose seal also houses a series of magnets 116 or metal plates 118 to provide for panel alignment. One of the nose seals further includes a sealing flap 39. In the closed position, the sealing flap 39 extends across the joint formed by the panels 25,

26. The sealing flap 39 prevents any leakage between the panels 25, 26. The nose seal configuration can be seen in greater detail in the sectional view of Fig. 7. There, it can be seen that the two nose seals 110, 111 are of like construction. Each includes a support plate 114 which extends from the top to the bottom of the panel to which the nose seal is attached. At spaced intervals along the support plate 114 are attached metal plates 116, 118. According to the present embodiment, only the metal plates 116 are magnetized, but it would be possible to use magnets of opposite polarity for both metal plates 116 and 118. Either way, the metal plates 116, 118 are magnetically attracted to each other and serve to align the panels 25, 26 as they approach the closed position. Both the support plate 114 and the metal plates 116, 118 are held in place and secured by the nose seal cover 120. The nose seal cover is illustratively a piece of 35 oz. hypalon. According to the present embodiment, the nose seal cover 120 is fixed to the front of the panel to which it is attached. On the back of the panel, however, the nose seal cover 120 is only attached to the panel by means of a hook and loop material, as at 122. Use of a non- permanent fastener 122 allows for access to the support

plate 114 and the metal plates 116, 118 in the event adjustment or replacement is necessary.

The nose sealing configuration also includes a sealing flap 39 for preventing leakage between the panels in the closed position. As can be seen from Fig. 7, the sealing flap 39 is a loop of material that is attached to the front of one of the panels 26. Illustratively, the sealing flap 39 is made of 35 oz. hypalon and is permanently fixed to the front of the panel 26. When the panels 25, 26 are in the closed position, the sealing flap 39 extends across the gap between the panels 25, 26 to seal the gap. The sealing flap 39 only runs along the portion of the panels below where the flexed header sealing means, discussed below, contacts the panels. The door system 20 according to the present invention is also uniquely adapted to prevent leakage of refrigerated air in the space above the panels 25, 26 and in the adjacent header assembly 28. Toward that end, there is provided a flexed header sealing means 130, as can be seen in Fig. 3. The flexed header sealing means 130 is attached to a header shroud 132, which is a part of the header assembly 28. When the header assembly 28 is assembled, the flexed header sealing means 130 extends down from the header assembly to make a sealing contact with the panels 25, 26. In the closed position, this arrangement prevents leakage above the panels. Leakage through the header assembly in the areas adjacent to the panels 25, 26 is prevented by the fanfold curtains 35, 36. The fanfold curtains 35, 36 extend above the panels, 25, 26 as shown in Fig. 3. Thus, when the panels 25, 26 are in the closed position and the fanfold curtains 35, 36 are stretched, the curtains 35, 36 extend up into the header assembly 28 and prevent leakage there. In this way, leakage above the panels 25, 26 and curtains 35, 36 is prevented when the panels 25, 26 are in the closed position.

The flexed header sealing means 130 are shown in Fig. 11. The flexed header sealing means 130 is made of a water resistant material, illustratively 35 oz. hypalon. The flexed header sealing means has a bent cross-sectional shape, which is achieved by sewing beading at the bends. The flexed header sealing means 130 also includes pockets 131 spaced approximately 2 feet apart along its length. These pockets 132 receive sections of spring steel 134, shown in Fig. 10, which give the flexed header sealing means its flexing ability. These sections of spring steel 134 are machined such that their cross-section is similar to that of the hypalon material making up the flexed header sealing means 130.

The sealing action of the flexed header sealing means 130 can be seen more clearly in Figs. 8 and 9. Fig. 8 shows a section of one of the panels as sealed by the flexed header sealing means 130. The contact portion 140 of the flexed header sealing means is maintained in a sealing relationship by means of the spring steel sections. In its relaxed state, when the panel 25 is not present, the contact portion 140 of the flexed header sealing means 130 extends to the left of the position shown in Fig. 8. The panel 25, however, forces the contact portion 140 to the right to the position shown in Fig. 8. The spring steel sections, in turn, bias the contact portion 140 against the panel 25, so as to maintain a sealing relation between the panel and the flexed header sealing means regardless of the position of the panel 25. Fig. 9 also shows how the flexed header sealing 130 means seals the top of the panels 25, 26 in the closed position. Fig. 9 shows a sectional view taken just above the panels 25, 26 in the closed position. The flexed header sealing means 130, as biased by the spring steel sections, is held against the panels 25, 26. Sealing in the header assembly in the regions to the left and right of the panels 25, 26 is achieved by the fanfold curtains

35, 36. As mentioned above, the fanfold curtains 35, 36 extend above the height of the panels 25, 26 and into the header assembly 28. This extension into the header assembly reduces leakage through the header assembly over the top of the fanfold curtains 35, 36.

The unique design of the curtains 35, 36 also allows smooth movement of the panels 25, 26 between the open position and the closed position. The panels 25, 26 are shown in the closed position in Fig. 9. As the panels 25, 26 begin to separate and move toward the closed position, the fanfold curtains 35, 36 fold up on themselves like an accordion. When the part of the door to which the curtains 35, 36 are attached passes the point on the wall where the curtains 35, 36 are attached, the curtains 35, 36 are in the fully compressed condition. Further movement of the panels toward the closed position causes the fanfold curtains 35, 36 to begin to unfold until the panels 25, 26 reach the fully open position as shown in Fig. 12. There, it can be seen that the curtains 35, 36 are again stretched between the attachment point on the wall and the attachment point on the panels 25, 26. It should be noted that, according to the present embodiment, the stretching of the curtains 35, 36 is less in the open position than in the closed position, since they are not attached to the wall exactly in between the edge of the panels 25, 26 in the closed position and the side sections 29, 30.

In an alternative embodiment, the door system according to the present invention is configured to have a door means comprised of a single panel. This embodiment is shown in Fig. 13 in the closed position. The operation and structural detail of the single-panel configuration is basically the same as for the bi-parting configuration described above. The single-panel configuration, however is different from the bi-parting model in the ways discussed below.

Fig. 14 shows the single-panel configuration in the open position. From that figure, it can be seen that the arrangement of the side sections 29', 30' is different than in the bi-parting configuration. The side section 29' is basically in the same position. However, the side section 30' is now adjacent to the doorway as opposed to being located remote from the doorway. This is because the single panel 25' extends across the entire doorway in the closed position. The single door is shown in cross-section from above in Fig. 15. It can be seen there that the single panel 25' can be viewed as a modification of the bi-parting doors. Instead of being joined by the nose seals, however, the two panels are semi-permanently connected together to be a single panel 25'. This connection may illustratively be achieved by means of a hook and loop fastener. In Fig. 15, the hook fastener 150 forms a fork configuration to fit over the loop fastener 152. When the two fasteners 150, 152 are mated, two panels becomes a single panel 25'. This embodiment is not limited, however, to this particular configuration, and a single panel of unitary construction could also be used.

The single-panel configuration also has a sealing loop to seal one edge of the panel in the closed position. The sealing loop 125' is illustratively made of 35 oz. hypalon and is permanently attached to the edge of the panel 25' that is against a side section in the closed position. The sealing loop 125' only runs along the portion of the panel below where the flexed header sealing means contacts the panel.

The operation of the lateral sealing means in the form of the fanfold curtain 35' of Fig. 16 is the same as in the bi-parting configuration. Further, the flexed sealing means 130' also operates in a similar fashion. The belt and drive mechanism would be nearly identical, except for the fastening of the trolleys 60 to the belt 84 in Fig. 5. There, both trolleys 60 would be attached to

the same side of the belt 84, so that they would move together in the same direction.

Despite the differences in the two configurations, the two door systems share several characteristics of the present invention. The trolley/track system provides for a small projection of the header assembly away from the wall. This leads to weight reduction of the system as well as allowing for closer placement of the panels to the doorway. The inverted motor also allows for tighter clearances over the header assembly. Both configurations also share the sealing characteristics of the present invention. The possible sources of leakage over, under and around the panels are all accounted for. The lateral sealing means prevents leakage around the panels while still allowing for smooth, unobstructed movement between the open and closed positions. The unique fanfold design of the curtains comprising the lateral sealing means provides for this. The curtains also extend up into the header assembly to prevent leakage through the header assembly in the regions adjacent to the panels. The nose seal in the bi-parting configuration and the sealing loop in the single panel configuration prevent leakage past the part of the panels not attached to the lateral sealing means. The nose seal in the bi-parting model includes the further function of aligning the panels as they approach the fully closed position. This also leads to a greater sealing effect between the two panels. Sealing above the panels is achieved by the header sealing means in both configurations as well. The spring steel inserts ensure that the header sealing means maintains a sealing contact with the panels at all times and positions.

In a further alternative embodiment, both the bi- parting and the single panel configuration can be adapted for use in a doorway where the controlled environment is a freezer as opposed to a refrigerator. Two minor modifications are necessary for this use. The fanfold curtains that make up the lateral sealing means are

insulated. Thus, instead of merely being one layer of 35 oz. hypalon, they include a core of Reflectex material sandwiched between two layers of 35 oz. hypalon. In a freezer application, blowers must also be employed in the header assembly to prevent undue condensation. The blowers are shown in Fig. 3 at 160. They are mounted in the supporting member 52 adjacent to the blower holes 162. The blowers 160 then blow warmed air into the area of the header assembly adjacent to the trolley/track means to evaporate condensation that could degrade performance. A door system for use in a freezer application has the same function and characteristics as the door systems previously described.

A further modification may optionally be used in a freezer environment, as in Fig. 17. Leakage in the header assembly 28 in the area adjacent to the panels is prevented by the fanfold curtains 35, 36. In freezer applications, preventing leakage is ever more critical. Toward that end, a side sealing means may be employed. The side sealing means, in the present embodiment, is a side seal 160. The side seals 160 are made of metal tubing 162 running from inside the header assembly 28 to the floor. On the face of the tubing 162 facing the curtains 35, 26 a foam seal 164 is included. The foam seal 164 maintains contact with the curtains 35, 36 when the panels 35, 36 are in the closed position. Further, the position of the side seals 160 is such that they would not obstruct the panels 25, 26 moving between the closed and open position. While the invention has been described in connection with the preferred embodiments, there is no intent to limit it to these embodiments. On the contrary, the intent is to cover all alternatives, modification, and equivalents, included within the spirit and scope of the invention as defined in the appended claims.