The subject invention concerns a safety device, which is intended to be used particularly in roll-up doors for the purpose of causing reversal of the closing movement of the door when an object is obstructing its path of movement. The safety device is of the kind comprising at least one signalling means which is arranged to emit a beam of light, a beam of sound or another kind of signalling beam and which is supported by the door leaf some distance from the door leaf closing edge. One example of prior-art safety devices for doors is formed with a sealing strip which is positioned at the lower edge of the door leaf. The sealing strip consists e.g. of a hollow strip of soft rubber, the ends of which are sealed to enclose a quantity of air in the interior of the strip. Should the door leaf hit an obstacle, while moving downwards into its fully closed position, the air inside the sealing strip is compressed, resulting in actuation of a diaphragm valve to reverse the closing movements of the door 1-eaf. This construction does, however, suffer from the disadvantage that it is comparatively fragile and sensitive, since the slightest leakage makes the device inoperative.

Considering that doors of this kind are frequently damaged, for instance by trucks and other vehicles passing through the doorway, the use of highly sensitive sealing strips is not very advisable. Another serious drawback inherent in this prior-art structure is that reversal of the door leaf movements is not initiated until the leaf hits the object which is obstructing its path of movement.

In another prior-art structure the problem is solved thereby that instead of enclosing an air cushion inside the lower sealing strip a photoelectric cell is used the beam of which is arranged to pass through the strip. Although this structure is leakage-proof, it still depends on deformation of the strip for the initiation of the reversal of the door movements.

In accordance with a third prior-art structure which suffers from disadvantages identical with those inherent in the first two prior-art structures discussed in the aforegoing two copper rails are mounted on the strip which rails are kept apart by a spring of a non-conductive material .

Finally,-it is also known to use photoelectric cells which are positioned closely above the floor level. Although this structure _ -does not depend on contact between the door leaf and the obstructing object for its operation persons may easily climb over the beam of the 0 photoelectric cell and the forks of fork-lift trucks may pass over it, and so the device will fail to operate. This prior-art structure could be combined with any one of the structures referred to in the aforegoing which become operative to reverse the closing movement of the door leaf upon contact with an obstructing object. However, 5 combinations of this kind suffer from the disadvantage that also in such cases contact is required between the door leaf and the . obstructing object to make the safety device operative, in addition to which installation thereof is comparatively expensive because of the necessity to double the sensing means. The purpose of the subject invention is to provide an efficient safety device which is intended for door leaves and similar structures and which is designed so as to be able to cause reversal of the closing movement of the door leaf without having to touch the object obstructing the path of the movement of the door leaf. 5 In addition, the safey device in accordance with the invention is designed so as to positively exclude the possibility of anyone stepping across it by mi stake, hich results in failure to initiate operation of the device, and it is also designed to completely relieve the door leaf and effect positive stopping of the door leaf movements within five seconds, thus fulfilling the safety regulations laid down by the authorities.

For this purpose, the safety device in accordance with the invention is characterized therein that the signallig means emits a

beam of light or a beam of sound or a signalling beam of another nature across the width of the door leaf at such a distance from the lower closing edge of the door leaf that any object that interrupts the beam emitted by the signalling means causes reversal or standstill of the closing movement of the door leaf before the edge thereof hits the obstructing object and therein that the signalling means is arranged to be displaced towards the lower closing edge of the door leaf during the final closing movement of the latter.

A particularly advantageous embodiment of the invention will be described in the following with reference to the accompanying drawings, wherein

Fig. 1 is a front view of a roll-up door equipped with a safety device in accordance with the invention,

Fig. 2 is a lateral, partly broken view of the door which illustrates the device in accordance with the invention on an enlarged scale,supported by a door leaf, and

Fig. 3 is a front view of the details in accordance with Fig. 2.

The roll-up door in accordance with the invention and shown in Ffg. 1 essentially comprises a roll-up door leaf 1, two posts 2, a lower cross beam 3, an upper cross beam 4 onto which the door-leaf 1 is wound to open the door, a motor 5 to actuate the roll-up movements, and a safety device 6.

One half of this safety device 6 is shown in detail in Figs. 2 and 3. It essentially comprises a photoelectric cell 7, a displaceable cell support arm 9 which is slidably mounted in a tubular holder 8, a stop limit edge 10 designed to determine the lower position of the arm 9, and an abutment 11 which is designed to abut against the floor when the door leaf 1 is approaching and in its fully door-closing position. Figs. 2 and 3 illustrate the door leaf 1 in the position it occupies when it is so close to its door-closing position that the abutment 11 hits the floor.

The safety device 6 in accordance with the invention operates in the following manner. When the beam of light extending between the two photoelectric cells 7, one at either side of the door leaf, is interrupted during the closing movement of the door leaf 1 this movement is reversed i medi tely. The reversal occurs so rapidly that the lower edge of the door leaf 1 will not hit the object that obstructs the path of the beam of light.

In order to allow the photoelectric cells to be mounted at a sufficiently high level above the lower edge of the door leaf 1 without blocking the way when the door is closing, they are displaceable in the direction indicated by arrow A relative to the door leaf 1. Displacement of the photoelectric cells is achieved by arranging the photoelectric cell support arm 9 in such a manner that it sl des freely in the tubular hol er 8 which is formed integral with the door leaf 1. A stopper means ^" or limiting means 10 is attached to the upper end of the support arm 9 in order to retain the latter, inside the tubular holder 8 and to ensure that both photoelectric cells 7 assume a position at the same level above the lower edge of the door leaf 1. When the door leaf was progressed so far downwards that the photoelectric cells 7 approach the floor, the abutment 11 hits the floor whereby the arm 9 slides upwards relative to the door leaf. Furthermore, the device is connected in a manner ensuring that the operation thereof ceases immediately before the door leaf reaches it fully closed position. This avoids interruption of the beam of light between the photoelectric cells 7 by means of the sealing strip 12 which is mounted at the lower transverse beam 3 on the lower edge of the door leaf 1.

Finally, it should be mentioned that the invention is not limited to the embodiment described in the aforegoing but that several embodiments are possible within the scope of the appended claims. For instance it is possible to fit the support arm 9 with a series of vertically positioned photoelectric cells to remove the possibility that an object which is pushed in between_ the beam of light and the lower edge of the door leaf is hit by the door.