Sliding folding door

A sliding folding door of double-walled construction with the sliding door including a plurality of leaves interconnected by shaped connecting rails. The doors are adapted to be foldable or pivotable about vertically extending pivots disposed inside the connecting rails. Each of the connecting rails includes two cylindrical walls that have a quarter-circle cross section and extend along the connecting rail, with center points of their radius of curvature being arranged in the pivots. Each cylindrical wall has opposed thereto a crosspiece that extends along a long side of the respective door leaves.

The invention relates to a sliding folding door whereof the double-walled 
leaves are interconnected by shaped connecting rails, about two vertical 
pivot shafts disposed inside the connecting rails. 
The proposed invention finds application in two- three- or multi-leaved 
sliding folding doors for industrial workshops and large garages. 
Considering the fact that there is an increasing energy scarcity and rising 
energy costs, the connecting or pivot points between the leaves of sliding 
folding doors are considered to be more and more of a problem. While there 
has been success in satisfactorily improving the thermal insulation of 
double-walled door leaves, there is still much to be desired in 
controlling the loss of heat through the gaps provided at the places of 
connection of the door leaves. These long gaps so far have not been sealed 
satisfactorily in any of the various known folding door constructions so 
that, especially when there is strong air movement, substantial thermal 
losses occur through the gaps. In addition, sufficient attention has 
frequently not been paid to the danger of accident, in the design of the 
connection and pivot places. Thus far the requirement that the unavoidable 
gaps at these points be so small that even children will not get their 
fingers caught has been inadequately met in many instances. 
A multi-leaf sliding folding door is known from German Pat. No. 1,509,252 
in which the leaves are articulatedly interconnected by means of cover 
strips having a U-shaped cross-sectional configuration, with the pivot 
axis of the leaves being within an outline of the cover strips. The 
proposed design of the long edges of the door leaves and of the cover 
strips, for technical reasons, is not suitable for avoidance of the 
disadvantages inherent in the long gap that is needed, between the 
pivotable parts. 
The invention deals with the problem of designing a sliding folding door in 
such a way that the long gap at the pivot point between the door leaves 
will be acceptably sealed in the closed position, and also in such a way 
that the gaps will be so small in any pivot position of the leaves so as 
to rule out any possibility of an accident caused by inserting fingers or 
the like into such gaps. 
The problem is solved in accordance with the present invention by a sliding 
folding door having a connecting rail provided between the respective door 
leaves with each connecting rail including two cylindrical walls having 
cross section of a quarter circle, extending along the connecting rail 
with a center of the radius of curvature of the cylindrical walls being 
disposed in the pivot axis. A crosspiece is disposed along the long side 
of the door leaf opposite each cylindrical wall. These cylindrical walls 
have a constant curvature and, in conjunction with the opposite 
crosspiece, have the effect that the gap at the pivot place can be made 
almost arbitrarily small, and the gap remains the same in any position of 
pivoting of the door leaf so that there is an excellent seal as well as 
avoidance of the risk of accidental injury. 
In a preferred embodiment of the invention, each connecting rail is also 
provided with two additional quarter-circle cylindrical walls extending 
lengthwise of the connecting rail, with the center of their respective 
radius of curvature also being disposed in the pivot axes. Two additional 
crosspieces respectively lie opposite the additional cylindrical walls. By 
this means, the seal is additionally improved because, in this way, each 
pivot point has two gaps one behind the other that enclose an air cushion. 
Moreover, with suitable proportions, an identical appearance of the inside 
and outside of the sliding folding door can be produced. 
For structural and also for visual reasons, the crosspieces advantageously 
are on the outer and inner walls respectively of the door leaf. 
Advantageously, the cylindrical walls are connected by crosspieces. 
An insulating material can be disposed between the cylindrical walls and, 
advantageously, packing strips are disposed along the crosspieces. 
According to another important characteristic of the invention, the 
elongated end of the cylindrical wall, in the closed position of the door 
leaf, abuts a sealing cushion or sealing pad fixed to the inner or outer 
wall of the door leaf. This sealing cushion serves as a stop to limit the 
pivoting movement of the door leaf in its open position and acts as a 
supplementary sealing means, because of an air cushion between the two 
gaps, disposed one behind the other, which is divided into two parts. 
A division of the air cushion in the pivot place into three parts, and 
therewith a further improvement of the seal and thermal insulation can be 
produced by a special design of the pivot articulation, in that strips are 
shaped onto the end pivot pins of the connecting rails which turn in a 
sleeve shaped on the inner or outer wall of the door leaf, said sleeve 
presenting a longitudinal slit.

Referring now to the drawings wherein like reference numerals are used 
throughout the various views and, more particularly, to FIGS. 1 and 2, 
according to these Figures, a sliding folding door includes three leaves 
1, 2 and 3 disposed adjacent to one another in a vertical door frame 4. 
The two uprights 5 and the transom 6 comprise shaped steel pieces and are 
fixedly connected with the building wall 7. A supporting rail 8 is 
provided in transom 6 wherein supporting rollers 9 run, on which door 
leaves 2 and 3 are rotatably suspended. The three door leaves 1, 2 and 3 
are double-walled, whereby outer wall 10 and inner wall 11 are made of 
sheet steel, between which thermal insulating material is provided. When 
the door is closed inner walls 11 are applied or abut (see FIG. 2) against 
a stop rail 13 secured to the floor 12. A corresponding stop rail (not 
shown) is also provided on an underside of the transom 6. 
The three door leaves 1, 2 and 3 are interconnected on their long sides 14 
that are opposite each other by means of shaped connecting rails generally 
designated by the reference numeral 15, so as to be swingable respectively 
about two vertical pivot shafts 16 and 17 disposed inside the shaped 
connecting rails 15. A corresponding connecting rail generally designated 
by the reference numeral 18 is provided between the first door leaf 1 and 
door frame upright 5 for pivotably fastening the door leaf 1 to the 
upright 5. As shown in FIG. 1, the connecting rails 15 are in pivotable 
connection with door leaves 1, 2 and 3 by means of hinges 19 disposed at 
three different heights. When the sliding folding door is opened, door 
leaves 1, 2 and 3 move in the direction indicated by the arrow 20 and, at 
the same time door leaves 1, 2 and 3 pivot in the direction indicated by 
arrows 21 toward each other and also forward out of door frame 4 toward 
the front illustrated in dashed lines in FIG. 2, until the leaves 1, 2, 3 
are close together, parallel, and perpendicular to the plane of door frame 
4 secured on a wall 7 of a building. 
As shown most clearly in FIG. 3 the shaped connecting rail 15 according to 
the invention is made of extruded aluminum and includes two cylindrical 
walls 22, 22' which have a quarter-circle cross section, and two other 
cylindrical walls 23, 23' which likewise have a quarter-circle cross 
section. All cylindrical walls 22, 22' and 23, 23' extend in the 
longitudinal direction of connecting rail 15, and are interconnected in 
pairs along their long edges. In the case of cylindrical walls 22, 22', 
the connection is effected with a smooth transition by way of a straight 
connecting piece 24; whereas, in the case of cylindrical walls 23, 23', 
there is an acute-angled narrow joint 25 between them. The two cylindrical 
walls 22 and 22' have the same radius of curvature 27 on the outside and a 
center 28 of the curvature of the respective cylindrical walls 22, 22' is 
located in the pivot shafts 16 and 17. The other two cylindrical walls 23 
and 23' have a radius of curvature 30 that is also corresponding on their 
inside surface 29, with the centers 31 of the curvature of the walls 23, 
23' being respectively located in pivot shafts 16 and 17. As shown in FIG. 
3, the radius of curvature 27 is greater than radius of curvature 30. 
The long sides 14 of the respective leaves 1, 2, 3 are formed of extruded 
aluminum U-shaped pieces 34, with the inner wall 11 and outer wall 10 
being fastened to the legs of the U-shaped piece 34. The legs of the 
U-shaped piece 34 terminate, as shown in FIG. 3, in crosspieces 32, 32' 
and 33, 33' with the ends of the crosspieces 32, 32' and 33, 33' being 
disposed at a slight distance from and opposed to the two pairs of 
cylindrical walls 22, 22' and 23, 23', disposed along the long sides 14 of 
the door leaves 1, 2 and 3. The crosspieces 32, 32', 33 and 33' are 
applied to outer wall 10 or inner wall 11 of door leaves 1, 2 and 3, and 
they are essentially in the plane of outer wall 10 and inner wall 11. If 
radius of curvature 30 is selected to be substantially smaller than radius 
of curvature 27 and at the same time joint 25 is widened by a connecting 
piece (not shown), then the distance between pieces 32 and 32' and pieces 
33 and 33' can be made equal, which means that the front and back of the 
closed sliding folding door will have an identical appearance. 
Cylindrical walls 22, 22' and 23, 23' are interconnected by crosspieces 35, 
whereby a cavity 36 is produced between cylindrical walls 22, 22' and 23, 
23' wherein there is provision of insulating material 37. 
Sealing strips 38 are disposed along the free ends of pieces 32, 32', 33, 
33'. The sealing strips 38 include long narrow brushes that are thrust or 
clamped in grooves (not shown) provided at the free ends of the respective 
crosspieces 32, 32', 33, 33'. 
Sealing pads 39 are fastened on inner walls 10 of leaves 1, 2 and 3 that 
extend along the whole long side 14 of said leaves 1, 2 and 3. Cylindrical 
walls 22, 23' terminate in a short extended end section 40 which, in the 
closed position of leaves 1, 2 and 3 of the door, abut against sealing 
pads 39 and are sealingly applied thereto. 
One hinge plate 41 of the hinges 19 that serve for pivotable connection of 
connecting rails 15 with leaves 1, 2 and 3 of the door is screwed on a 
crosspiece 35 or on an extension that projects beyond cylindrical wall 22. 
The other hinge plate 43 is screwed to the leg of the U-shaped connecting 
piece 34 or on crosspiece 33. The hinge plates 41, 43 are connected for 
pivotable movement by a pin 42. In another embodiment of this joint shown 
in the right-hand side of FIG. 3 in the region of cylindrical wall 23' and 
crosspiece 33', instead of the hinges 19' a strip 44 is shaped on 
connecting rail 15 as an extension of crosspiece 35, which strip 44 
supports a pin 45 at the free end thereof, with the pin 45 likewise being 
shaped on the strip 44. This pin 45 is rotatably seated in a sleeve 46 
shaped on outer wall 10 of leaf 1, 2 or 3 or on crosspiece 33'. The sleeve 
46 includes a longitudinal slit 47 that has a center angle of at least 
90.degree.. The pin 45 is surrounded at a number of places distributed 
over the long side 14 of the leaves 1, 2, or 3 by a slitted bearing shell 
48 made of a plastic material, whereby lubrication of this joint becomes 
superfluous.