SYSTEM

TECHNICAL FIELD

The present invention relates to the technical field of entrance systems. The present invention also relates to a safety mechanism for an entrance system.

BACKGROUND

An entrance system typically comprises one or more movable door members, each door member being arranged in a door frame, and an automatic door operator being arranged to move the door members. Entrance systems may be used in a variety of different private or public locations, for instance in garages, logistic facilities, airports, shopping malls or stores, to name a few. The door members may be, for instance, industrial vertical-lifting doors, overhead sectional doors, folding doors, swing doors, sliding doors or revolving doors.

In a conventional overhead sectional door system, an automatic door operator system is mounted generally in the ceiling above the door member and adapted to pull the door member by means of an elongated transmission element, e.g. wires, chains or belts, being attached to the door member. Such an overhead sectional door system often implements balancing springs to reduce the force required to open the door.

Other, more sophisticated, automatic door operator systems known in the art involve arranging an automatic door operator unit in conjunction with a transmission system, wherein the automatic door operator unit is mounted directly to the door member. The automatic door operator, which comprises a motor, drives a drivable member of the transmission system into connection with an elongated member. The elongated member is accordingly adapted to interplay with the drivable member such that the drivable member is driven along the elongated member on at least one side of the associated door frame. The door member can thus be driven up and down, i.e. between an open and closed position, with respect to the door frame.

In any automatic door operator implementation known in the art, there may be a risk of a transmission element being damaged, or even breaking. A common cause of transmission element breakage is that too much tension is applied to the transmission element during installation thereof. Too much tension in the transmission element can also be accumulated during operation for various reasons. Another source of transmission element breakage is rust. Rust can, for example, be caused by environmental factors. Transmission element breakage typically occurs as a direct cause of one or more individual sprockets or links in the transmission element breaking or being displaced from its intended position.

In the conventional overhead sectional door system, a known safety solution for managing chain breakage involves measuring the motor current and arranging a power switch in the automatic door operator unit disposed in the ceiling. Depending on the current level, a decision can be made regarding the operability of the door operator. If it is determined that the door operator is not operating as intended, the power switch can be activated. This solution is, however, unstable due to a lack of robustness caused by the sheer amount of electrical energy required to drive door members of an entrance system. This is particularly the case for door operator units using BLDC (Brushless DC) motors.

Other solutions involve arranging rotating gears or cogwheels being in contact with e.g. the transmission element upon chain breakage. However, due to the existence of rotating parts, such units can increase the risk of component failures. A safe operation thus cannot be guaranteed.

Another, more trivial, solution involves manual chain maintenance, e.g. performed by authorized personnel to determine the health of the chain. This can potentially be complemented with various sensor arrangements being installed to communicate identified chain breakage. This is obviously a very cost-inefficient solution.

There is thus no satisfactory solution in the prior art for managing chain breakage in entrance systems. This is particularly the case for entrance systems utilizing the more sophisticated door drive systems as discussed above.

The present inventor has identified the above-mentioned drawbacks of the prior art, and consequently developed a particularly insightful solution which aims to overcome, or at least mitigate, one or more of these drawbacks. SUMMARY

Accordingly, an object of the present invention is to provide a safety mechanism in an automatic door operator that is cheap, safe, effective and easy to install.

In this disclosure, a solution to the problems outlined in the background section is proposed. In a first aspect of the proposed solution, an entrance system is provided. The entrance system comprises one or more movable door members; an automatic door operator being mounted to the one or more movable door members, the automatic door operator comprising at least one motor being coupled to move the one or more movable door members between a closed position and an open position; a transmission system comprising a drivable member and an elongated member, wherein the at least one motor is coupled to drive the drivable member into connection with the elongated member to transfer power from the at least one motor to the one or more movable door members; and a safety mechanism, wherein, in the event that the elongated member breaks, the transmission system is arranged to activate the safety mechanism for terminating said power transfer from the at least one motor to the one or more movable door members.

In one or more embodiments, the safety mechanism comprises at least one biasing member being adapted to apply a pulling force to the transmission system.

In one or more embodiments, the at least one biasing member is mounted between the transmission system and a protruding portion of the automatic door operator.

In one or more embodiments, the pulling force is applied in a direction away from the transmission system and towards the protruding portion.

In one or more embodiments, the at least one biasing member comprises a spring, a pneumatic device, a hydraulic device and/or a pulley assembly.

In one or more embodiments, the transmission system is connected to the automatic door operator by means of a movable connection and adapted to be movable between at least a first and a second position, wherein the elongated member is operative in the first position and wherein the elongated member is broken in the second position. In one or more embodiments, said movable connection comprises a hinged attachment, wherein, in the event that the elongated member breaks, the transmission system is arranged to rotate around its hinged attachment, from the first position to the second position, for activation of the safety mechanism.

In one or more embodiments, said movable connection comprises a sliding engagement, wherein, in the event that the elongated member breaks, the transmission system is arranged to slide via the sliding engagement with respect to the automatic door operator, from the first position to the second position, for activation of the safety mechanism.

In one or more embodiments, the safety mechanism comprises an electromechanical switch being activatable for terminating said power transfer from the at least one motor to the one or more movable door members.

In one or more embodiments, the electromechanical switch is disposed between the transmission system and the automatic door operator.

In one or more embodiments, the elongated member is one of an elongated belt or an elongated drive chain.

In one or more embodiments, the one or more movable door members comprises a plurality of horizontal and interconnected sections.

In one or more embodiments, the automatic door operator is arranged on an edge surface of the bottommost section of the one or more movable door members, and wherein the elongated member is vertically extending along a side of the one or more movable door members.

In one or more embodiments, the at least one motor is a brushless DC motor, a stepping motor, a DC motor and/or an AC motor.

In a second aspect, a safety mechanism is provided. The safety mechanism is for an entrance system comprising one or more movable door members; an automatic door operator being mounted to the one or more movable door members, the automatic door operator comprising at least one motor being coupled to move the one or more movable door members between a closed position and an open position; and a transmission system comprising a drivable member and an elongated member, wherein the at least one motor is coupled to drive the drivable member into connection with the elongated member to transfer power from the at least one motor to the one or more movable door members, wherein the safety mechanism is arranged to, in the event that the elongated member breaks, be activated by the transmission system for terminating said power transfer from the at least one motor to the one or more movable door members.

In one or more embodiments, the safety mechanism comprises the functionalities of the safety mechanism according to any of the embodiments of first aspect.

Other objectives, features and advantages of the present invention will appear from the following detailed disclosure as well as from the drawings. It is to be noted that the invention relates to all possible combinations of features.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to “a/an/the [element, device, component, means, step, etc.]” are to be interpreted openly as referring to at least one instance of said element, device, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed unless explicitly stated. As used herein, the term “comprising” and variations of this term are not intended to exclude other additives, components, integers or steps.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be described in the following; references being made to the appended diagrammatical drawings which illustrate non-limiting examples of how the inventive concept can be reduced into practice.

Fig. l is a schematic block diagram of an entrance system generally according to the present invention.

Fig. 2 shows an entrance system according to one embodiment in which some inventive aspects of the present disclosure can be applied.

Figs. 3a-b are schematic illustrations of a safety mechanism according to one embodiment.

Figs. 4a-b are schematic illustrations of a safety mechanism according to one embodiment. Figs. 5a-b are schematic illustrations of a safety mechanism according to one embodiment.

Figs. 6a-b are schematic illustrations of a safety mechanism according to one embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the invention will now be described with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the particular embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements.

With reference to Fig. 1, a schematic flowchart diagram illustrating an entrance system 100 according to one embodiment is shown. The entrance system 100 may be designed for installation in a building to control access into the building from the outside of said building, or between different sections of the building. The entrance system 100 comprises one or more movable door members 1 lOa-n and an automatic door operator 40 coupled to cause movement of the door members 1 lOa-n. The movement is typically caused between at least a closed position in which passage through said entrance system 100 is prevented, and an open position in which passage is admitted. Movement of the movable door members 1 lOa-n between intermediate positions in between the closed and opened positions may also be caused. A transmission system 30 is coupled with the movable door members 1 lOa-n to take part in their opening and closing movement.

The movable door members 1 lOa-n may be sliding door members, revolving door members, swing door members, industrial vertical-lifting door members, overhead sectional door members, folding door members and/or any combination thereof.

The automatic door operator 40 may comprise a controller 48 having an associated memory 49 and program instructions 49a stored therein, a power supply 46, a drive unit 44 and at least one motor 42, typically an electric motor 42. The electric motor 42 may be a BLDC (brushless DC) motor, a stepping motor, a DC motor or an AC motor. The automatic door operator 40 is however not restricted to having these particular components. Other arrangements may alternatively be realized.

In the embodiment shown in Fig. 1, the controller 48 is adapted to cause controlled actuation of the drive unit 44 by means of electrical power from the power supply 46. The drive unit 44 is configured to feed electricity into the motor 42 in varying amounts and at varying frequencies, thereby indirectly controlling the speed and torque of the motor 42. The motor 42 is connected to the transmission system 30, and more specifically to a drivable member 32 of the transmission system 30. Upon actuation of the motor 42, torque is transmitted to the drivable member 32 of the transmission system 30 such that it is rotated. A gearbox may be arranged between the motor 42 and the drivable member 32. The drivable member 32 is thus driven into connection with an elongated member 34. The connection of the drivable member 32 and the elongated member 34 may be obtained in that the elongated member 34 at least partially wraps around the drivable member 32. The drivable member 32 may engage with the elongated member 34 when the elongated member 34 at least partially wraps around the drivable member 32. The elongated member 34 thus translates the motion of the drivable member 32 into a movement of the movable door members 1 lOa-n.

The drive procedure can be interpreted as the automatic door operator 40 “climbing” along the elongated member 34 by means of the transmission system 30. One end of the elongated member 34 may thus be generally arranged at the opening of the door member 110 by the automatic door operator 40 or transmission system 30. The other end of the elongated member 34 may be generally arranged on an upper or lower end of the door member 110, or any side of the door member 110, depending on the type of entrance system 100.

In some embodiments, the transmission system 30 may alternatively be in the form of an endless-loop transmission system wherein the elongated member 34 is an endless-loop member adapted to endlessly rotate around at least one side of the door member 110. The elongated member 34 may be in the form of a suspended bendable member. The elongated member 34 may be a substantially straight member. In one embodiment, the elongated member 34 is a belt. The belt may be a timing belt. The belt may be provided with teeth. The drivable member 32 may be a toothed pulley configured to transmit a large amount of torque and force to the belt. The belt and the toothed pulley thus have a movable connection such that they interplay with one another. The toothed pulley and belt may together transmit high speeds. Such transmission is reliable and requires a small amount of maintenance. Such transmission is also compact and requires little space.

In one embodiment, the elongated member 34 is a drive chain. The drivable member 32 may be a sprocket configured to transmit a large amount of torque and force to the drive chain. The drive chain and the sprocket thus have a movable connection such that they interplay with one another. The sprocket and drive chain may together transmit high speeds. Such transmission is reliable and requires a small amount of maintenance. Such transmission is also compact and requires little space.

The controller 48 is configured for performing different functions of the automatic door operator 40. The controller 48 may be implemented using instructions that enable hardware functionality, for example, by using computer program instructions executable in a general-purpose or special-purpose processor that may be stored on a computer-readable storage medium (disk, memory, etc.) to be executed by such a processor. The controller 48 is configured to read the instructions 49a from the memory 49 and execute these instructions 49a to control the operation of the automatic door operator 40. The controller 48 may be implemented in any known controller technology, including but not limited to microcontroller, processor (e.g. PLC, CPU, DSP), FPGA, ASIC or any other suitable digital and/or analog circuitry capable of performing the intended functionality. The memory 49 may be implemented in any known memory technology, including but not limited to E(E)PROM, S(D)RAM or flash memory. In some embodiments, the memory 49 may be integrated with or internal to the controller 48.

The entrance system 100 comprises a safety mechanism 50. The safety mechanism 50 comprises functionalities for terminating power transfer between the motor 42 and the one or more movable door members 1 lOa-n. More specifically, the safety mechanism 50 is arranged to terminate power transfer between the automatic door operator 40 and the transmission system 30. The safety mechanism 50 may be operatively connected to the controller 48 such that the controller 48 can be instructed by the safety mechanism 50 of a termination of power transfer between the automatic door operator 40 and said transmission system 30.

Termination of power transfer may further involve generating a failure report indicating the cause, including any potentially related parameters, of the elongated member 34 breakage. The controller 48 may be configured to generate such a report in response to the safety mechanism 50 being activated.

The safety mechanism 50 may be any component suitably configured to instruct termination of power transfer between the motor 42 and the movable door members 1 lOa-n. The safety mechanism 50 is adapted to be activated by the transmission system 30 in the event that the elongated member 34 breaks.

In one embodiment, the safety mechanism 50 comprises an electromechanical switch. The electromechanical switch is activatable for terminating said power transfer from the motor 42 to the movable door members 1 lOa-n. The electromechanical switch may be a toggle switch, push-button switch, reversing switch, relay, or a circuit breaker. The safety mechanism 50 may be in wired or wireless connection with the automatic door operator 40, more specifically the controller 48. If wireless connection is utilized, the connection may be based on any known wireless communication technologies known in the art, e.g. Bluetooth or WiFi.

In one embodiment, the safety mechanism 50 comprises an optical sensor, such as a photoelectric sensor or a magnetically induced sensor, such as a Hall effect sensor. The optical sensor and/or magnetically induced sensor may be arranged to operate generally according to the electromechanical switch, i.e. being activatable for terminating said power transfer between the motor 42 and the movable door members HOa-n.

With reference to Fig. 2, an entrance system 100 according to one embodiment is shown. The entrance system 100 comprises one movable door member 110 being an overhead sectional door member 110. The door member 110 is arranged in a door frame 112 comprising a set of upper frame sections 113a-b, each being connected to a respective lower frame section 114a-b. The door member 110 comprises a plurality of horizontal and interconnected sections 11 la-e, in this example five. The door member 110 is adapted to be driven between a closed and an open position by means of the automatic door operators 40a-b and the transmission systems 30a-b. Note that in the provided example, two identical and individually arranged sets of automatic door operators 40a-b, transmission systems 30a-b, and safety mechanisms 50a-b are arranged on a respective side of the door frame 112. The present disclosure can involve one or more such sets. The automatic door operators 40a-b are arranged on edge surfaces of the bottommost interconnected section I l la, although they may be arranged on other appropriate sections 11 Ib-e in other embodiment. As seen in the figure, the elongated members 34a-b are arranged on and extending along a respective side of the door member 110, wherein at least a portion of each elongated member 34a-b is extending into connection with a corresponding automatic door operator 40a-b.

As seen in Fig. 2, the safety mechanisms 50a-b are arranged in close proximity to a corresponding automatic door operator 40a-b. If the safety mechanisms 50a-b are in wired connection with the automatic door operators 40a-b, it is desired that said wired connection is easy to install and can guarantee a safe operation. The shown arrangement effectively eliminates the need for excessive wiring. Moreover, in cases wherein the safety mechanisms 50a-b are in wireless connection with the automatic door operators 40a-b, a more reliable communication can be established the higher the spatial proximity between the safety mechanisms 50a-b and the automatic door operator 40a-b is. The spatial proximity between the safety mechanisms 50a-b and the automatic door operators 40a-b is not only desired in the embodiment shown in Fig. 2, but also in other embodiments as realized in the present disclosure. The present inventor has identified that some prior art solutions having an automatic door operator in the ceiling and a safety mechanism somewhere along a transmission member, for instance where the transmission member is attached to a door member, would not involve a satisfactory solution with regards to the considerations explained above.

As further seen in Fig. 2, the safety mechanisms 50a-b are arranged in conjunction with the transmission systems 30a-b and adapted to be activated by the transmission systems 30a-b. Activation of a safety mechanism 50 according to different embodiments will now be thoroughly explained with further references to Figs. 3a-b, 4a-b, 5a-b and 6a-b.

In each one of the embodiments shown in Figs. 3a-b, 4a-b, 5a-b and 6a-b, three different chain breakage scenarios can be realized: 1) during door movement between a closed and an opened position; 2) during door movement between an opened position and a closed position; or 3) during no door movement. Although not expressly seen in the figures, it is implicit that the automatic door operator 40 is mounted directly to a door. In either one of the scenarios, termination of power transfer between the automatic door operator 40 and the door will be activated. In some embodiments, the entrance system is provided with an auxiliary drive mechanism which, in response to breakage of the elongated member 34, is activated to force a door into a closed or opened position. Nevertheless, it is important that the transmission system 30 does not continue to operate once termination of power transfer has been triggered by the safety mechanism 50.

With reference to Figs. 3a-b, a safety mechanism 50 is shown according to one embodiment. An automatic door operator 40, including a motor 42, and a transmission system 30, including a drivable member 32 and an elongated member 34, are arranged generally according to the subject-matter as explained with reference to Figs. 1 and 2. In Fig. 3a, the components are operating as intended, i.e. the elongated member 34 is not broken. In Fig. 3b, the elongated member 34 has, for some reason, snapped. The different arrows shown in the figures are indicators of forces acting on the components.

During normal operation, as shown in Fig. 3a, the force acting on the elongated member 34 is directed vertically upwards. The force acting on the elongated member 34 is therefore counteracting the downwardly directed force as caused by the weight of the transmission system 30. The automatic door operator 40 being mounted directly to the door is consequently adapted to cause controlled movement of said door between different positions.

In the event that the elongated member 34 breaks, as shown in Fig. 3b, the upwardly directed force acting on the elongated member 34 is (at least substantially) cancelled, and the weight of the transmission system 30, caused by the gravitational force, will be the dominating acting force. The transmission system 30 is thus adapted to trigger activation of the safety mechanism 50, the safety mechanism 50 thereby terminating power transfer between the motor 42 and the door member.

With reference to Figs. 4a-b, a safety mechanism 50 is shown according to one embodiment. An automatic door operator 40, including a motor 42, and a transmission system 30, including a drivable member 32 and an elongated member 34, are arranged generally according to the subject-matter as explained with reference to Figs. 1 and 2. In Fig. 4a, the components are operating as intended, i.e. the elongated member 34 is not broken. In Fig. 4b, the elongated member 34 has, for some reason, snapped. The different arrows shown in the figures are indicators of forces acting on the components.

The safety mechanism 50 may comprise at least one biasing member 52. In Figs. 4a-b, the safety mechanism 50 comprises one biasing member 52. The biasing member 52 is adapted to apply a pulling force, as indicated by the downwardly directed arrow, to the transmission system 30.

The biasing member 52 may be mounted between the transmission system 30 and a protruding portion 40a of the automatic door operator 40. The protruding portion 40a is in this example disposed vertically below the transmission system 30, although other arrangements may be realized. For instance, different mounting arrangements can be realized for different types of entrance systems, e.g. sliding door systems or revolving door systems, to name two. Regardless of the type of entrance system, the pulling force is exerted in a direction away from the transmission system 30 and towards the protruding portion 40a.

The biasing member 52 may be connected to the transmission system 30 by means of any appropriate fastening units, e.g. screws, pins, knobs, adhesives, and so forth, at a first fastening portion 52a. Similar fastening units may be used for connecting the biasing member 52 to the automatic door operator 40 at a second fastening portion 52b. The second fastening portion 52b is appropriately disposed at the protruding portion 40a of the automatic door operator 40.

The biasing member 52 may comprise a spring, a pneumatic device, a hydraulic device, a pulley assembly, and/or any other means appropriately arranged to apply a pulling force to the transmission system 30. In the examples shown, a spring is used as the biasing member 52. Accordingly, during the normal operation of the entrance system, i.e. upon the drivable member 32 being driven into connection with the transmission system 30, the spring is assuming an extended position.

Upon breakage of the elongated member 34, as seen in Fig. 4b, the driving force on the elongated member 34 is (at least substantially) cancelled. As a consequence, the pulling force established by the biasing member 52 will force the spring to return to its initial state, thereby pulling the transmission system 30 towards a safety switch 54 of the safety mechanism 50. The transmission system 30 is adapted to trigger activation of the switch 54, for instance via a push button 54a, thereby terminating the power transfer between the motor 42 and the door.

Compared to the embodiment shown and explained with reference to Figs. 3a-b, the biasing member 52 has some additional advantages. First, a more reliable safety mechanism 50 is provided. Since the behavior of the biasing member 52 is predictable, e.g. according to Hooke’s law for springs in particular, the biasing member 52 can be customized. The customization can be adapted according to the prevailing operating conditions of the automatic door operator 40, and more specifically to the mechanical energy produced by the motor 42. For instance, the number of biasing members 52 or the resilience, flexibility or strength of the biasing members 52 can be adapted in order to provide safe operational conditions and effective power termination. Secondly, by mounting a biasing member 52, the automatic door operator 40 and the transmission system 30 can be utilized in other types of entrance systems, e.g. sliding door systems. This is due to the fact that the triggering of the safety mechanism 50 by the transmission system 30 is not reliant on gravitational force since the biasing member 52 is capable of biasing the force produced by the motor 42 during operation. Thirdly, a biasing member 52 according to the embodiment shown and explained with reference to Figs. 4a-b is a very cheap safety solution which is both easy to install, efficient, and not reliant on moving parts.

With reference to Figs. 5a-b, a safety mechanism 50 is shown according to one embodiment. An automatic door operator 40, including a motor 42, and a transmission system 30, including a drivable member 32 and an elongated member 34, are arranged generally according to the subject-matter as explained with reference to Figs. 1 and 2. In Fig. 5a, the components are operating as intended, i.e. the elongated member 34 is not broken. In Fig. 5b, the elongated member 34 has, for some reason, snapped. The different arrows shown in the figures are indicators of forces acting on the components. The embodiment of Figs. 5a-b may be complemented with one or more biasing members 52 as discussed in the embodiment of Figs. 4a-b.

In Figs. 5a-b, the transmission system 30 is connected to the automatic door operator 40 by means of a movable connection 36. Accordingly, the transmission system 30 is adapted to be pivotally moved with respect to the automatic door operator 40. Although the embodiment of Figs. 4a-b describes that the transmission system 30 moves towards the protruding portion 40a of the automatic door operator 40, the movement is enabled by means of the biasing member 52. In this case, the movement is enabled by the movable connection 36 between the automatic door operator 40 and the transmission system 30 in itself. The movement is enabled between a first position, wherein the elongated member 34 is operative (Fig. 5a), and a second position, wherein the elongated member 34 is broken (Fig. 5b).

The movable connection 36 may be any type of suitable connection that enables the transmission system 30 to move towards the safety mechanism 50 by itself, with respect to the automatic door operator 40, when the elongated member 34 breaks.

In Figs. 5a-b, the movable connection 36 comprises a hinged attachment. The hinged attachment is disposed on a second protruding portion 40b on the automatic door operator 40, the second protruding portion 40b being different from the protruding portion 40a. The hinged attachment enables the transmission system 30 to, in the event that the elongated member 34 breaks, rotate around its hinged attachment, from the first to the second position, for activation of the push button 54a on the safety switch 54. In one embodiment, the transmission system 30 is mounted to a hinge plate (not shown), wherein the hinge plate is hingedly attached to the hinged attachment for enabling the rotation of the transmission system 30.

With reference to Figs. 6a-b, a safety mechanism 50 is shown according to one embodiment. An automatic door operator 40, including a motor 42, and a transmission system 30, including a drivable member 32 and an elongated member 34, are arranged generally according to the subject-matter as explained with reference to Figs. 1 and 2. In Fig. 6a, the components are operating as intended, i.e. the elongated member 34 is not broken. In Fig. 6b, the elongated member 34 has, for some reason, snapped. The different arrows shown in the figures are indicators of forces acting on the components.

The difference between the embodiments shown in Figs. 5a-b and 6a-b is that the movable connection 36 in Figs. 6a-b comprises a sliding engagement instead of the hinged attachment in Figs. 5a-b. Moreover, the safety mechanism 50 of Figs. 6a-b comprises a biasing member 52 configured according to the subject-matter described with reference to Figs. 4a-b. The sliding engagement comprises a sliding track 38 being disposed at the second protruding portion 40b of the automatic door operator 40. A sliding member 39 disposed at the transmission system 30 is arranged to be in sliding connection with the sliding track 38 such that the transmission system 30 can slide with respect to the automatic door operator 40 in the event that the elongated member 34 breaks. Hence, the push button 54a of the safety switch 54 can be activated in response to the elongated member 34 breaking. The embodiment of Figs. 6a-b may be complemented with a hinged attachment as discussed in the embodiment of Figs. 5a-b, i.e. a movable connection 34 comprising both a hinged attachment and a sliding engagement.

The invention has been described above in detail with reference to embodiments thereof. However, as is readily understood by those skilled in the art, other embodiments are equally possible within the scope of the present invention, as defined by the appended claims.