Safety bumper with signalling device

Safety bumpers provide flexible strips for making contact inside a hollow space in a foamed body. It is suggested to carry out the making of contact by way of a closed switching strip which is mounted in a hollow space bordered by a frame preferably designed as a U-profile. An elastic pressure strip having webs extending transversely with respect to the switching strip is assigned to this switching strip. As a result, making of contact is ensured in the case of an arrangement which is not susceptible to pollution and humidity influences and which also permits a pre-assembling.

BACKGROUND AND SUMMARY OF THE INVENTION 
The invention relates to a safety bumper having a bumper body consisting of 
an elastic foamed material and having a supporting plate and an electric 
switching device in the form of a strip-shaped contact arrangement which 
switches when outside pressure is exercised on the bumper body. 
Safety bumpers of this type are known (Safety Bumper Brochure of MAYSER 
Polymer Electric, Imprint SB/5/2.89/D). Safety bumpers of this type are 
used, for example, for being mounted on robots or unmanned transport 
systems in order to cause an immediate stoppage of such devices should 
these come in contact with persons in an unintended manner. The advantage 
of such safety bumpers is the fact that such shut-off devices, because of 
the construction of the foamed-material bumper, have no sharp edges and 
also cannot be bent. 
In the known constructions, the design is such that the switching device 
consists of two flexible strips. As a rule, one strip is fastened directly 
to a supporting plate arranged on the rear of the safety bumper while the 
other strip is arranged at the foamed bumper body at a corresponding 
distance to the first strip in a hollow space created for this purpose. 
Since, as a rule, the foamed bodies are covered toward the front with an 
airtight and watertight skin, it is necessary to leave the supporting 
plates open toward the rear so that the foamed material which is used as 
the elastic element for the approaching and moving away of the switching 
strip can be compressed in the desired manner while discharging part of 
its air volume and, mainly because of the returning air, can resume its 
initial position which had existed before a deformation. Safety bumpers of 
this type can therefore be used only to a limited extent at locations with 
high air pollution or high humidity because the relatively sensitive 
switching strips are affected in an undesirable manner. In addition, the 
fastening of one of the switching strips to the foamed body requires a 
relatively expensive manufacturing. 
It is an object of the invention to develop a safety bumper of the 
initially mentioned type in such a manner that the device becomes less 
sensitive to outside influences and its manufacturing is facilitated. 
For achieving this object, it is provided in the case of a safety bumper of 
the initially mentioned type that the supporting plate is equipped with a 
frame and in that the contact arrangement is constructed as a switching 
strip fastened to the supporting plate inside the hollow space formed by 
the frame, an elastically bendable pressure strip, which is arranged on 
the opposite wall of the hollow space and is provided particularly with 
elevations for the contacting of the switching strip, being assigned to 
the switching strip. By means of this design, the foamed material takes 
over only a shock absorber function and, at points at which it is pressed 
from the outside, exercises a force on the pressure strip which will 
elastically bend at this point. It touches the switching strip, which is 
completely sealed in itself, for the purpose of making contact. The 
elastic pressure strip restores itself automatically. In the case of the 
design according to the invention, the elastic pressure strip forms the 
elastic restoring element which, in the known arrangements was formed by 
the foamed material. By means of the new development, the making of 
contact cannot be disadvantageously affected by environmental influences 
(dusty or humid air) because the contact takes place inside the switching 
strip which is sealed off. Nevertheless, a sensitive triggering is 
maintained. The elastic pressure strip, in each case, provides the 
required switching pressure. In this case, it is advantageous that the 
switching strip is arranged inside a hollow space which is surrounded by 
firm walls and which is fixedly connected with the supporting plate 
carrying the switching strip. This permits an extensive pre-assembling and 
creates a robust construction. 
According to certain preferred embodiments, it is advantageous to provide 
the pressure strip with elevations for the contacting of the switching 
strip because the local pressure forces exercised on the switching plate 
can be increased in this manner and the reliability of the triggering of a 
switching operation becomes higher. Each bending of the pressure strip 
therefore, if the distances of the webs are selected correspondingly, will 
result in some sort of point contact of the pressure strip which reliably 
triggers the desired switching operation. 
A particularly advantageous embodiment of the invention includes an 
arrangement wherein the frame is provided with an inwardly directed edge 
extending at least on the opposite longitudinal sides and wherein the 
pressure strip rests against the inner edge of this edge. In this case, 
the frame is simultaneously also used as a holding device for the pressure 
strip so that the complete switching device, comprising the switching 
strip, the supporting plate, the frame and the pressure strip, may be 
premounted without the foamed body. Despite the resting of the pressure 
strip against the lower edge of the edge of the frame, a flush contact 
with the foamed body takes place according to preferred embodiments 
wherein the pressure strip is provided with an elevation projecting into 
the area between the inner edges of the edge which face one another, and 
wherein the elevation has a height corresponding to the thickness of the 
edge. In certain preferred embodiments, the bumper body can be glued 
directly on the edge facing away from the switching strip. 
Certain preferred embodiments include an arrangement wherein the frame and 
the supporting plate are parts of a one-piece profiled strip having a 
C-shaped cross-section, and wherein the open faces of the profiled strip 
are closed off by inserted closing pieces. This arrangement permits a 
particularly simple and economical manufacturing because it is sufficient 
to cut the length of the profiled strip from an extruded profile which 
may, for example, be made of aluminum or plastic. The safety bumper, 
having a specific length, will then be produced in a simple manner by 
inserting closing caps on the face side, and the foamed body may then be 
glued on, in which case, this foamed body must be provided only with a 
smooth underside and not, as in the state of the art, with a hollow space. 
The new design therefore permits an economical series production which can 
also be automated. 
Certain preferred embodiments include an arrangement wherein the bumper 
body is covered by an impermeable skin which is tightly connected with the 
surrounding frame or the lateral walls of the profiled strip, and wherein 
a lattice-type fabric band is provided under the skin in the area of the 
lateral walls of the bumper body and the outer walls of the profiled 
strip, the fabric band being used for the fastening of the bumper body to 
the profiled strip, on the one hand, and, on the other hand, for the 
fastening of the skin to the bumper body and to the profiled strip. These 
features finally offer special advantages with respect to the fastening of 
the foamed bumper body on the pre-assembled switching device. 
The invention is illustrated in the drawing by means of embodiments and 
will be described in the following.

DETAILED DESCRIPTION OF THE DRAWINGS 
In FIGS. 1 to 3, a safety bumper 1 is illustrated which is provided with a 
bumper body 2 which consists of an elastic foamed material and which is 
provided on the outside with an impermeable skin 3 which is tightly 
connected with a surrounding metal frame 4 to which the foamed body 2 is 
also glued. The foamed body 2 has a rectangular recess 5 which, together 
with a supporting plate 6 forming the rear closure of the safety bumper 1, 
forms a hollow space 7 in the interior of the bumper body 2 in which, as 
will be described in the following, the switching device is arranged which 
triggers a contact when outside forces are exercised on the bumper body 2 
transversely to the plane of the supporting plate 6. The openings provided 
in it which are not shown and which permit the pressure compensation from 
the hollow space 7 when the foamed body 2 is deformed, are therefore 
provided on the side of the safety bumper 1 by which the safety bumper 1 
is mounted on the part to be secured. 
The switching device comprises a switching strip 8 which is known per se 
and which consists of an elastic hose-type profile held in a supporting 
profile 9, contact strips being arranged in the hose-type profile which 
are sealed off toward the outside and which come in contact with one 
another when the elastic profile of the switching strip 8 is touched on 
the outside. The switching strip 8 has electric leads 10 which in the 
embodiment are led out, in a sealed manner, between the supporting plate 6 
and the frame 4 with which the supporting plate 6 is tightly connected, 
for example, screwed together, welded together or made in one piece. 
An elastically bendable pressure strip 11 is mounted, for example, glued to 
the wall of the hollow space 7 which is opposite the supporting plate 6. 
The pressure strip 11 may, for example, consist of an elastic plastic 
strip which is glued directly to the foamed material of the bumper body 2. 
On this pressure strip 11, elevations are provided in the form of webs 12 
which--as shown in FIG. 3--extend transversely with respect to the 
longitudinal direction of the switching strip 8 and are arranged uniformly 
distributed along the length of the pressure strip 11 at a distance from 
one another. The length of the webs 12 is dimensioned to be such that, 
even if the bumper body 2 is deformed by external forces not completely 
perpendicularly with respect to the supporting plate 6, nevertheless a 
contact takes place between one of the webs 12 and the switching strip 8 
when the elastic pressure strip 11 bends as a result of the external 
forces exercised on the bumper body 2. The distance of the pressure strip 
ii from the switching strip is shown at an enlarged scale in the 
embodiment. The arrangement may also be made in such a manner that the 
webs 12 of the pressure strip 11 come in slight contact with the outer 
shell of the switching strip 8 so that the switching sensitivity is 
enhanced and the switching times are as low as possible. 
The punctiform contact between the switching strip 8 and one of the webs 12 
leads to the triggering of the switching operation if pressure is 
exercised on the foamed body 2 from the outside. For example, the drive of 
an unmanned floor conveyor cart, to which the safety bumper 1 is fastened 
at the front, can then be switched off. If this type of a floor conveyor 
cart then unintentionally drives against a person crossing its travelling 
path, the drive of the cart will be switched off immediately. Naturally, 
the new safety bumpers may be used in all conditions in which safety 
bumpers have already been used previously. The relatively robust 
construction is advantageous which nevertheless does not result in any 
disadvantages with respect to the response sensitivity of the safety 
device. 
The robust construction may still be improved considerably according to the 
embodiment of FIG. 4 and 5. In the embodiment of FIG. 4 and 5, the 
supporting plate 6' on which the switching strip 8' is mounted and the 
frame 4' is each part of an integrally constructed profiled strip 15 which 
may, for example, be made of aluminum and is extruded in a known manner 
and then only has to be cut into lengths. This profiled strip 15 has a 
C-profile and, on the upper edge of the lateral frame parts 4', has an 
edge 16 directed toward the inside which therefore partially covers in the 
upward direction the hollow space 7' in which the switching strip 8' is 
arranged. The pressure strip 11' rests on both sides on the interior side 
of this edge 16 facing the hollow space 7' and, in the embodiment, as 
indicated particularly in FIG. 5, is constructed as a continuous web 
profile provided with curved-out areas 17, these curved-out areas 17 
forming the webs 12' which rest against the switching strip 8'. As a 
result of this construction, the pressure strip 11' is elastically pressed 
against the edge 16. The dimensions of the pressure strip and the webs 
12', the height of the switching strip 8' and the clearance height (h) of 
the profiled strip 15, in this case, can be coordinated in a simple manner 
in such a way that the desired contact is caused of the pressure strip 11' 
on the edge 16, on the one hand, and by means of the webs 12' on the 
switching strip 8' on the other hand. 
As shown in FIG. 4, the profiled strip 15 is provided with two ribs 18 in 
its center which extend in parallel to one another and form a groove 
between one another for receiving the switching strip 8'. 
In order to ensure a snug contact of the pressure strip 11' on the bumper 
body 2', an elevation of the pressure strip 11' is provided in the area 
between the free ends of the edges 16 facing one another which, in the 
embodiment, has the shape of a flat strip 19 which is glued together with 
the pressure strip 11'. Naturally, it would also be possible to produce 
the pressure strip 11' in one piece with the elevation strip 19 if this 
seems more expedient. As a result of the selected embodiment, the pressure 
strip 11' rests directly on the underside 20 of the bumper body 2' which, 
by means of this underside 20, in its lateral outer areas, is glued on the 
top side of the edges 16 which faces it. The bumper body 2', which is a 
foamed body, in a very simple manner, can be provided with the lower 
straight end side 20. The connection with the profiled strip 15 also does 
not present any problems. 
In the embodiment, the bumper body 2' is also provided with a skin 3' 
sealing it off toward the outside. This skin reaches into the area of the 
lateral walls 15a of the profiled strip 15. In this area, it is connected 
with the lateral wall 15a by way of a lattice-type fabric band 21 provided 
between the profiled strip and the lateral wall 15a, this fabric band 2i 
also extending into a part of the lateral walls of the bumper body 2' and 
also being connected with them, particularly being glued to them. This is 
illustrated in detail in FIG. 4a. For this purpose, the two parallel 
lateral walls 2a' of the bumper body 2' of the safety bumper 1' 
illustrated in FIGS. 4 and 5 are in alignment with the outer walls 15a of 
the profiled strip 15. The arrangement of the fabric band 21 ensures an 
intimate connection between the bumper body 2' and the profiled strip 15, 
on the one hand, and the skin 3' and the whole safety bumper 1', on the 
other hand. This type of lateral fastening therefore aids the glued 
connection of the bumper body 2' on the top side of the edges 16. 
As easily recognizable in FIGS. 4 and 5, the shown embodiment permits a 
complete pre-assembling of the switching device comprising the profiled 
strip 15, the switching strip 8' and the pressure strip 11'. The face-side 
closure takes place in a simple manner by end face stoppers which are 
adapted to the profile of the profiled strip 15 and which, in the area of 
the ribs 18 and of the switching strip 8' guided in it, may have a 
corresponding recess. The stoppers fit on the end shown in FIG. 4. These 
stoppers may also easily be equipped with outlet openings for the electric 
lines The whole, already pre-assembled switching device may then, in a 
simple manner, be glued together with the bumper body 2' as described.