Bellows

The invention relates to a bellows in which the cover projects like a roof over the two arms and the apexes of the inner layer of the arms are supported on the inner layer of the cover. In this way a very robust and wear-resistant construction of the bellows is obtained.

BACKGROUND OF THE INVENTION 
This invention relates to a bellows of the type set out in U.K. patent 
application No. 2,113,123. Whilst the cover and the arms of this known 
bellows have a common continuous outer layer made from fabric, the inner 
layer which is provided for stiffening purposes consists of three 
individual parts formed by perforated sheets which are perforated along 
the edges of the pleats. 
FIG. 1 represents the prior art and shows the conventional construction of 
the inner layer in a schematic view. The inner layer of a bellows of the 
whole bellows consists of an inner layer 1 for the cover of the bellows 
and two inner layers 2 for the two arms of the bellows. The inner layers 1 
and 2 of the cover and the arms are cut in a triangular shape on the sides 
facing one another, so that the apexes 1a and 2a lie against one another 
but are not continuous. The inner layers 1 and 2 of the cover and the arms 
of the bellows are provided with perforations 3 in the region of the later 
edges of the pleats. 
The inner layers 1 and 2 of the cover and the two arms of the bellows are 
adhered to a continuous outer layer made from fabric, and this ensures 
that the three inner stiffening layers hold together. Then the two arms of 
the bellows are folded in and, if required, crosspieces can also be fixed 
between individual pleats for further stiffening. 
The main disadvantage of this known bellows according to FIG. 1 is that the 
apexes 1a, 2a of the inner layer of the cover and the arms pierce the 
outer fabric layer and damage this outer layer even after the bellows has 
been operating only for a comparatively short time. 
The object of the invention, therefore, is to provide a bellows which is 
distinguished by a very stable and lasting construction. 
In the bellows according to the invention the cover projects like a roof 
over the two arms and the apexes of the inner layer of the arms are 
supported on the inner layer of the cover, and therefore the grave danger 
of damage to the outer layer caused by the apexes of the inner layer of 
the arms, as occurs with the known bellows (FIG. 1), is avoided. Because 
of the particularly lasting and wear-resistant construction of these very 
critical parts of the bellows the construction according to the invention 
is distiguished by a long operating life. 
The construction of the bellows according to the invention is advantageous 
above all for applications in which lasting sealing of the bellows is 
required. 
Advantageous embodiments of the invention are the subject matter of the 
subordinate claims and are explained in connection with the description of 
two embodiments which are illustrated in the drawings.

DETAILED DESCRIPTION 
FIG. 2 shows the inner layer of a first embodiment of the bellows according 
to the invention. A common continuous inner layer 4 is used for the cover 
and the two lateral arms of the bellows. Only part of one half of the 
inner layer 4 is shown in FIG. 2; the longitudinal axis of the inner layer 
4 is designated by 5. 
The inner layer 4 is made from a plastics sheet which has perforations 6 
running at right angles to the longitudinal direction of the bellows in 
the region of the later pleat edges. Perforations 7 are also provided 
which run in the longitudinal direction of the bellows and mark the side 
edges of the cover. Finally, a perforation 8 running in a zig-zag pattern 
is provided between the lateral arms and the cover of the bellows. 
In the region between the later inner pleats of the arms and the cover the 
inner layer 4 is provided with triangular stampings 9 which do not meet 
each other. These stampings 9 have the shape of an isosceles triangle in 
which the apex 9a of the triangle coincides with the (later) upper end of 
the inner pleats of the arms and the length of the sides 9b, 9c of the 
triangle is smaller than the distance "a" between the upper ends of the 
(later) inner and outer pleats of the arms of the bellows. 
At individual points 10 the perforations 6 on the pleat edges are widened 
like slots so that flap strips 11 can be drawn into the inner layer 4 in 
the manner shown in FIG. 2. Thus these strips each run above the inner 
layer 4 in the region of one double pleat and below the inner layer 4 in 
the region of the next double pleat. The flap strips 11 are advantageously 
made from fabric and are coated on the outer surface with a sheet which is 
perforated along the pleat edges. 
In order to produce the bellows, first of all the inner layer 4 is provided 
with all the said perforations and stampings. Then the flap strips 11 are 
drawn into the inner layer 4, preferably so that in each case there is one 
flap strip in the region of each arm and two flap strips in the region of 
the cover. 
Then the inner layer 4 with the flap strips 11 drawn into it is placed on 
an outer layer 12 which is preferably made of fabric and the two layers 
are connected firmly together, preferably by adhesion. The flap strips 11 
are only adhered to the outer layer 12 in the parts located between the 
inner layer 4 and the outer layer 12. Figure 3 shows the multi-layer wall 
construction thus obtained: The flap strips 11 run between the inner layer 
4 and the outer layer 12 but in each case in the region of adjacent pleats 
pass through the aforementioned slots at the points 10 of the pleat 
perforations 6 to the inner face of the inner layer 4. 
After the inner and outer layers 4, 12 have been connected, the two arms of 
the bellows are folded in along the perforations 7 and 8. This results in 
the construction which can be seen in FIGS. 4, 5 and 6 in which the cover 
13 of the bellows projects laterally, i.e. like a roof, over the two arms 
14 by the dimension b (cf. FIGS. 2 and 4). 
Before the two arms are folded in, the flap strips 11 on the inner face of 
the inner layer 4 are preferably divided up at the points provided for the 
fixing of cross-pieces 15 (e.g. at the point 1b, cf. FIG. 2) so that 
individual flaps 17 (cf. FIG. 4) are produced to which the crosspieces 15 
can be fixed (for example by adhesion or by riveting). 
FIGS. 5 and 6 show schematically the function of the triangular stampings 9 
in the extending movement of the bellows. 
In the region of the triangular stampings 9 of the inner layer 4 the wall 
thickness of the arms of the bellows only consists of the outer layer 12, 
i.e. fabric, and therefore the bellows does not put up any great 
resistance against the initial extending movement (transition from the 
state shown in FIG. 5 to the state shown in Figure 6). However, in the 
further extending movement (for instance, beyond the state shown in FIG. 
6) the surface regions of the inner layer 4 adjoining the triangular 
stampings 9 increasingly resist any further deformation so that a desired 
progressive extension stop is produced. By selection of the size of the 
stampings 9 it is possible to influence as required the time at which an 
extension stop comes into effect during the extending movement. It will be 
recognised from a study of FIGS. 2, 5 and 6 that the extension stop comes 
into effect all the more early the smaller the triangular stampings are 
chosen to be 
The cover 13 of the bellows according to the invention can be provided on 
its upper surface (and possibly also on its lower surface in the region 
which projects like a roof) with reinforcement made from metal wires and 
plastic fibres. The metal wires advantageously run parallel to the pleat 
edges and the plastic fibres at right angles to the pleat edges. 
The perforations of the inner layer 4 can be filled with plastic coating 
material after the bellows has been produced and the pleats have thus been 
converted from the plane position to the pleated position. If the plastic 
coating material is introduced and hardened with the bellows in a more or 
less compressed state, when the bellows is later extended a desired 
additional resistance to the extending movement will be put up by the 
plastic coating material present in the perforations. 
The plastic coating material introduced into the perforations of the inner 
layer also provides a stiffening of the pleats which makes it possible if 
required to allow the pleats to rest directly on the bench. In this case 
the arms of the bellows can be fixed for example by angles. 
Within the scope of the invention it is of course also possible for the 
perforations of the inner layer to be formed by a pre-marked broken line 
which is weakened by cut-outs. 
As can be learned from the above description and can be seen in particular 
from FIG. 2, the edge of the inner layer 4 of the arms facing the cover is 
in the form of triangles the apexes 20 of which each form the upper end of 
an outer pleat 21 (FIG. 4) of the arms 14. As the view of the bellows from 
below in FIG. 4 shows, the cover 13 projects like a roof over the two arms 
14. The apexes 20 of the inner layer 4 of the arms 14 are accordingly 
supported on the inner layer 4 of the cover 13. In this way the apexes of 
the inner layer of the arms and the cover are prevented from lying 
directly opposite one another in the manner shown in FIG. 1 and thus 
causing a high degree of strain and rapid wear on the outer layer 12. 
FIG. 7 shows a second embodiment of the invention in which the same 
reference numerals are used as in FIG. 2 for the same elements. 
In the construction according to FIG. 7 the cover 13 and the arms 14 each 
have a separate inner layer 4 and 4' respectively which are separated from 
each other by arrow-shaped spaces 9'. Thus the spaces 9' are defined on 
the side of the arms 14 by two straight edges 9'b and 9'c and on the side 
of the cover 13 by the edges 8'a, 8'b and 8'c. 
In this embodiment too the cover 13 projects over the two arms like a roof. 
The apexes 20 of the inner layer 4' of the arms 14 are supported on the 
inner layer 4 of the cover 13.