Patent Description:
Some conventional door closers comprise a spring and a hydraulic cylinder containing oil. The spring may be increasingly compressed (or otherwise deformed) during opening of the door leaf. The hydraulic cylinder may provide a damping force proportional to the speed of the door leaf. The use of oil may however not be desired, for example due to poor fire safety, leakage and low sustainability. Moreover, such conventional door closers often have unsatisfactory reliability, for example due to temperature changes and wear.

<CIT> discloses a door closer comprising a force transmission shaft turning in accordance with the movement of a door, a spring element operationally connected with the force transmission shaft so that opening of the door takes place against the force of the spring element, and a dynamic machine comprising rotor means arranged in force transmission connection with the force transmission shaft and stator means operationally connected with the rotor means.

<CIT> discloses an electro permanent magnet, EPM, comprising a first permanent magnet, a second permanent magnet, a coil and a target object. An actuator comprising a plurality of EPMs is also disclosed. The actuator comprises a piston and a braking pad coupled to the piston. The piston is moved due to repulsive forces between two or more of the EPMs.

<CIT> discloses a brake device comprising a pivoting lever having a ratchet tooth and being pivotable about an axis, a tension spring, a locking wheel having ratchet teeth, a traction element coupled to a vehicle door and to a guide element fixed to the ratchet wheel, and an electromagnet.

In order to avoid hydraulics in a door closer, the door closer may comprise an electric machine and a closing spring forcing the door leaf towards a closed position. The electric machine can function as an electric generator when the door leaf is opened and/or closed to thereby harvest electric energy. In order to hold the door leaf still, the electric machine can function as an electric motor to hold the door leaf still against the force from the closing spring. For such operation, the electric motor must be supplied with a holding current. A considerable amount of energy is therefore consumed during the door leaf holding phase without performing any mechanical work.

For most types of energy harvesting based systems, the total energy budget should be a great concern. It is therefore as important to reduce the energy consumption as it is to increase the amount of energy harvested.

One object of the present disclosure is to provide a brake device having a low power consumption.

A further object of the present disclosure is to provide a brake device having no power consumption in each of a released state and a braking state.

A still further object of the present disclosure is to provide a brake device having small dimensions.

A still further object of the present disclosure is to provide a brake device having a less complex design.

A still further object of the present disclosure is to provide a brake device having a cost effective design.

A still further object of the present disclosure is to provide a brake device having a fail-safe operation.

A still further object of the present disclosure is to provide a brake device solving several or all of the foregoing objects in combination.

A still further object of the present disclosure is to provide an arrangement for controlling movements of an access member relative to a frame, which arrangement solves one, several or all of the foregoing objects.

A still further object of the present disclosure is to provide an access member system comprising a frame, an access member and an arrangement, which access member system solves one, several or all of the foregoing objects.

According to one aspect, there is provided a brake device comprising a hard magnet; a soft magnet configured to switch polarity between a first polarity and a second polarity when being subjected to a magnetic field and configured to maintain the polarity when the magnetic field is removed; an electric coil located around the soft magnet; an electric control system configured to apply a current pulse to the electric coil to generate the magnetic field for changing the polarization of the soft magnet; and a brake element comprising a magnetic target section, the brake element being arranged to move to a released position when the soft magnet adopts the first polarity, and arranged to move to a braking position due to a magnetic field generated by the hard magnet and the soft magnet in combination and acting on the magnetic target section when the soft magnet adopts the second polarity.

When a current pulse of a certain duration and level is applied to the electric coil wound around the soft magnet, the magnetic field generated by the current pulse flips the polarity of the soft magnet from the first polarity to the second polarity. Once the soft magnet has been flipped from the first polarity to the second polarity, the hard magnet and the soft magnet combine to generate a magnetic field. This magnetic field acts on the magnetic target section of the brake element (e.g. by means of an attractive or repulsive magnetic force) such that the brake element moves from the released position to the braking position. Once the polarity of the soft magnet has been switched from the first polarity to the second polarity and the brake element has moved from the released position to the braking position, the magnetic field generated by the hard magnet and the soft magnet in combination hold the brake element in the braking position without power supply. The released position and the braking position may constitute distinct positions for the brake element.

When the brake element adopts the released position, the brake device adopts a released state. Conversely, when the brake element adopts the braking position, the brake device adopts a braking state. The brake device is bi-stable. With bi-stable is meant that the brake device can be in any of the released state and the braking state without consuming energy, and that energy is only required to switch the brake device between the released state and the braking state.

The hard magnet, the soft magnet and the electric coil form an electropermanent magnet (EPM). The EPM provides a high magnetic force when the soft magnet adopts the second polarity and a zero magnetic force, or near zero magnetic force, when the soft magnet adopts the first polarity. The EPM may be stationary.

The soft magnet has a lower coercivity than the hard magnet. Due to its low coercivity, the polarity of the soft magnet is switched by the applied current pulse. Due to its high coercivity, the polarity of the hard magnet is not affected by the applied current pulse. The hard magnet may for example comprise a Neodymium alloy such as a Neodymium-Iron-Boron (NdFeB), or other alloy having a relatively high intrinsic coercivity. The soft magnet may for example comprise an Alnico alloy, Iron-Cobalt-Vanadium, or other alloy having a relatively low intrinsic coercivity.

Since the polarity of the soft magnet can be switched by a current pulse, only a very small amount of electric energy is required to switch the EPM to thereby effect movement of the brake element between the released position and the braking position. The brake device is therefore an ultra-low-power brake device. The brake device may only require a few mJ to switch between the released state and the braking state.

When the soft magnet adopts the second polarity, the brake element may be arranged to move to the braking position due to either an attractive magnetic force or a repulsive magnetic force.

The brake device may for example be used in a non-hydraulic arrangement for controlling movements of an access member relative to a frame, such as a door closer. Alternative uses of the brake device are however conceivable.

The brake element may be configured to brake an output member. To this end, the brake element may engage the output member in the braking position. The energy required to switch the EPM is much less than the energy required to hold the output member by means of an electric motor.

The brake device may be a frictional brake device. In this case, the brake element may frictionally engage the output member in the braking position.

The magnetic target section may be of any type for being influenced by a magnetic field of the EPM. The magnetic target section may close a magnetic circuit in the braking position of the brake element. The magnetic target section may for example comprise a ferromagnetic material, such as a soft magnetic material, in case the brake element is arranged to move to the braking position due to an attractive magnetic force. The brake element may for example comprise a permanent magnet in case the brake element is arranged to move to the braking position due to a repulsive magnetic force.

The brake element may be forced towards the released position. To this end, the brake device may further comprise a releasing spring arranged to force the brake element towards the released position. Alternatively, or in addition, the brake element may be arranged to be forced towards the released position by means of gravity.

The brake device may further comprise a brake hinge. In this case, the brake element may be rotatable about the brake hinge between the released position and the braking position.

The brake element may comprise a brake pad. The brake pad may be configured to frictionally engage a friction surface of an output member when the brake element adopts the braking position in order to effect braking.

The control system may comprise a driver for applying a first current pulse to the electric coil to switch the soft magnet from the second polarity to the first polarity, and for applying a second current pulse to the electric coil to switch the soft magnet from the first polarity to the second polarity. The control system may further comprise a capacitor for applying a first current pulse to the electric coil to switch the soft magnet from the second polarity to the first polarity; a normally open switch connected in series with the driver and the electric coil; and a normally closed switch connected in series with the capacitor and the electric coil.

The capacitor may have a capacitance sufficient for switching the soft magnet from the second polarity to the first polarity. The first current pulse may be a negative pulse and the second current pulse may be a positive pulse.

By means of the capacitor, the normally open switch and the normally closed switch, the first current pulse will be applied by the capacitor through the electric coil in case a power supply is lost. It can thereby be ensured that the brake device always adopts the released state when a power supply is lost. The control system according to this variant therefore provides a fail-safe operation. The power supply may for example be a battery or a mains power supply. By means of the power supply, a control voltage may be supplied so the control system.

According to a further aspect, there is provided an arrangement for controlling movements of an access member relative to a frame, the arrangement comprising a brake device according to the present disclosure arranged to brake the access member. The arrangement may be a door closer. The access member may be a door leaf.

The arrangement may further comprise an electromagnetic generator having a rotor arranged to be driven to generate electric energy by movement of the access member. The arrangement can thus be provided with energy harvesting functionality.

The generator may be constituted by an electric machine configured to function as an electric generator and as an electric motor. The electric machine may for example be of the BDC (brushed direct current) type or the BLDC (brushless direct current) type.

The control system may be electrically powered by the generator. The arrangement may thus be an energy harvesting arrangement, such as an energy harvesting door closer.

The arrangement may further comprise an output member arranged to be contacted by the brake element when the brake element adopts the braking position. To this end, the output member may comprise a friction surface for being contacted by the brake element, such as by a brake pad of the brake element.

The output member may be rotatable or linearly movable. The output member may be driven by the rotor or may be fixed to the rotor. In any case, the brake element (e.g. a brake pad thereof) may engage the output member in the braking position to effect braking of the output member, and thereby also of the access member.

The arrangement may further comprise a transmission arranged to transmit a movement of the access member to a movement of the output member. The transmission may be a gear train comprising two or more gear wheels. In this case, one of the gear wheels may be fixed to the rotor. Alternatively, the transmission may be a belt transmission or a chain transmission.

The arrangement may further comprise an input member. The input member may be fixed to a door leaf. In this case, the input member may be concentric with a door hinge of the door leaf. The input member may form part of the transmission. In this case, the input member may be a gear wheel.

The arrangement may further comprise a closing spring for connection to each of the access member and a frame. The closing spring may be configured to force the access member towards a closed position in relation to the frame. The closing spring may thus be tensioned to store mechanical energy when the access member is opened.

The transmission may comprise a freewheel device configured to freewheel when the access member moves in an opening direction. The freewheel device may comprise a freewheel or a unidirectional clutch. The freewheel device enables the access member to always be opened, regardless of the state of the brake device. By means of the freewheel device, the access member can be moved to a more open position despite the braking adopting the braking position. This is advantageous for less strong people, like children or elderly people. When the brake device is in the braking state and the access member is in the closed position, the access member can be incrementally pushed (e.g. by several small pushes) to the open position.

When the transmission comprises the freewheel device, energy harvesting only takes place during closing movements of the access member. The freewheel device therefore enables the access member to be opened more easily, e.g. substantially only the force of a closing spring needs to be overcome.

The rotor may be arranged to be driven by the transmission.

The transmission may be a speed increasing transmission. In this way, a holding force required to hold the access member by braking the output member is significantly lower than a holding force required to hold the access member by directly braking the access member. This significantly lower holding force in turn enables the brake device to be reduced in size. A further advantage with the speed increasing transmission is that the rotor of the generator can be driven at higher speeds. This enables a more effective harvesting of electric energy and the generator to be reduced in size.

According to a further aspect, there is provided an access member system comprising a frame, an access member movable relative to the frame, and an arrangement according to the present disclosure. The access member may be a door leaf.

The arrangement may be configured to hold the access member in an open position during a selectable holding time. After this holding time, the brake device is commanded to adopt the released state such that the access member starts to close by means of the closing spring. During this closing movement of the access member, energy can be harvested by means of the generator. The load of the generator can be controlled in order to control a closing speed of the access member.

The access member system may further comprise a closing spring arranged to force the access member towards a closed position.

Further details, advantages and aspects of the present disclosure will become apparent from the following description taken in conjunction with the drawings, wherein:.

In the following, a brake device comprising a soft magnet, an arrangement for controlling movements of an access member, and an access member system comprising the arrangement, will be described. The same or similar reference numerals will be used to denote the same or similar structural features.

<FIG> schematically represents an arrangement 10a. The arrangement 10a of this example is a door closer. The arrangement 10a comprises a brake device 12a. The brake device 12a comprises an electropermanent magnet, EPM, <NUM>, an electric control system <NUM> and a brake element <NUM>.

The EPM <NUM> comprises a hard magnet <NUM>, a soft magnet <NUM> and an electric coil <NUM>. The soft magnet <NUM> is configured to switch polarity between a first polarity and a second polarity when being subjected to a magnetic field. In <FIG>, the soft magnet <NUM> has the first polarity.

The EPM <NUM> of this example further comprises pole pieces <NUM>. The hard magnet <NUM> and the soft magnet <NUM> are here arranged in parallel between the pole pieces <NUM>. The pole pieces <NUM> may be made of a ferromagnetic material. The electric coil <NUM> is wound around the hard magnet <NUM> and the soft magnet <NUM>.

The brake element <NUM> comprises a magnetic target section <NUM>. The magnetic target section <NUM> is here exemplified as an arm of a material strongly responsive to magnetic fields, such as a ferromagnetic material. The magnetic target section <NUM> may be made of a soft magnetic material with no or low remanence. As an alternative example, the magnetic target section <NUM> may form only a part of an arm or other type of member.

The brake element <NUM> of this example further comprises a brake pad <NUM>. The brake pad <NUM> is fixed to the magnetic target section <NUM>. The brake pad <NUM> may for example be made of rubber.

The brake device 12a further comprises a brake hinge <NUM>. The brake element <NUM> is rotatable about the brake hinge <NUM>.

The brake device 12a of this example further comprises a releasing spring <NUM>, here exemplified as a coil spring. One end of the releasing spring <NUM> is connected to a stationary structure (not denoted) and the other end of the releasing spring <NUM> is connected to the brake element <NUM>.

The brake device 12a of this example further comprises a mechanical stop <NUM>. The mechanical stop <NUM> is here exemplified as a stationary pin.

The arrangement 10a of this example further comprises an output member 38a. The output member 38a of this example is a toothed rack. The output member 38a is linearly movable along its longitudinal axis.

When the soft magnet <NUM> has the first polarity according to <FIG>, the hard magnet <NUM> and the soft magnet <NUM> have opposing magnetizations. As a consequence, the EPM <NUM> is in an off state producing no, or substantially no, net external field across the pole pieces <NUM>.

In <FIG>, the brake element <NUM> is in a released position <NUM>. In the released position <NUM>, the brake element <NUM> is pulled by the releasing spring <NUM> to rotate about the brake hinge <NUM> until the brake element <NUM> (here the magnetic target section <NUM> thereof) contacts the mechanical stop <NUM>. In the released position <NUM>, the brake pad <NUM> is separated from the output member 38a. The releasing spring <NUM> thus ensures that the output member 38a is not braked when the EPM <NUM> is in the off state.

The arrangement 10a of this example further comprises a door leaf <NUM>. The door leaf <NUM> is one example of an access member according to the present disclosure. In <FIG>, the door leaf <NUM> is in a closed position <NUM>. The door leaf <NUM> is rotatable from the closed position <NUM> to an open position.

The arrangement 10a of this example further comprises a transmission 46a. The transmission 46a is configured to transmit a movement of the door leaf <NUM> to a movement of the output member 38a. In this example, the transmission 46a is configured to transmit a rotation of the door leaf <NUM> (clockwise in <FIG>) to a linear movement of the output member 38a (to the left in <FIG>).

The transmission 46a is a speed increasing transmission, here exemplified as a gear train. In this specific example, the transmission 46a comprises a first gear wheel <NUM>, a second gear wheel (not visible), a third gear wheel <NUM>, a fourth gear wheel <NUM> and a fifth gear wheel <NUM>. The second gear wheel is fixed to, and concentric with, the third gear wheel <NUM>. The first gear wheel <NUM> meshes with the second gear wheel. The third gear wheel <NUM> meshes with the fourth gear wheel <NUM>. The fourth gear wheel <NUM> meshes with the fifth gear wheel <NUM>. The fifth gear wheel <NUM> meshes with the output member 38a. The second gear wheel is smaller than the first gear wheel <NUM>, the third gear wheel <NUM> is larger than the second gear wheel, the fourth gear wheel <NUM> is smaller than the third gear wheel <NUM>, and the fifth gear wheel <NUM> is smaller than the fourth gear wheel <NUM>.

The first gear wheel <NUM> is fixed to the door leaf <NUM>. The first gear wheel <NUM> is one example of an input member according to the present disclosure.

The arrangement 10a of this example further comprises an electromagnetic generator <NUM>. The generator <NUM> comprises a stator (not shown) and a rotor <NUM>. In this example, the fifth gear wheel <NUM> is fixed to the rotor <NUM>. The rotor <NUM> is thereby driven by the transmission 46a. The rotor <NUM> is thus arranged to be driven to generate electric energy by rotation of the door leaf <NUM>. By means of the transmission 46a, the rotor <NUM> rotates at a high speed compared to the rotational speed of the door leaf <NUM> to thereby improve the energy harvesting capacity of the generator <NUM>. When the brake element <NUM> is in the released position <NUM>, the door leaf <NUM> can be manually opened and closed as desired.

<FIG> schematically represents the arrangement 10a when the door leaf <NUM> has moved in an opening direction <NUM> from the closed position <NUM> to an open position <NUM>. By means of the transmission 46a, the output member 38a is thereby caused to move linearly. More specifically and with reference to <FIG>, the door leaf <NUM> and the first gear wheel <NUM> rotate together in a clockwise direction, the second gear wheel and the third gear wheel <NUM> rotate in a counterclockwise direction, the fourth gear wheel <NUM> rotates in a clockwise direction, the fifth gear wheel <NUM> rotates in a counterclockwise direction, and the output member 38a moves linearly to the left.

During the movement of the door leaf <NUM> in the opening direction <NUM>, electric energy may or may not be harvested by means of the electric generator <NUM>. In order to hold the door leaf <NUM> in the open position <NUM>, the EPM <NUM> is activated to an on state, as described in the following.

<FIG> schematically represents the arrangement 10a when the brake element <NUM> adopts a braking position <NUM>. In <FIG>, the control system <NUM> has sent a second current pulse through the electric coil <NUM>. A second magnetic field is thereby generated that causes the soft magnet <NUM> to change polarity or flip from the first polarity to a second polarity. Since the hard magnet <NUM> has a higher coercivity than the soft magnet <NUM>, the polarity of the hard magnet <NUM> is not affected by the magnetic field. When the soft magnet <NUM> adopts the second polarity, the magnetization directions of the hard magnet <NUM> and the soft magnet <NUM> are aligned. As a consequence, the hard magnet <NUM> and the soft magnet <NUM> combine to produce an external magnetic field. The EPM <NUM> thereby adopts the on state. Once the soft magnet <NUM> has switched to the second polarity, no energy is required to keep the EPM <NUM> in the on state.

The external magnetic field generated by the EPM <NUM> acts on the magnetic target section <NUM>, here by magnetic attraction. The brake element <NUM> is thereby forced into the braking position <NUM> against the force of the releasing spring <NUM>, which is extended. The EPM <NUM> thus pulls the brake element <NUM> such that the brake pad <NUM> is forced against the output member 38a. In the braking position <NUM>, the brake pad <NUM> contacts and frictionally engages the output member 38a. The brake element <NUM> thereby brakes the output member 38a by friction. In this way, the door leaf <NUM> can be held in the open position <NUM> without energy consumption. The door leaf <NUM> is not closed until the brake device 12a again adopts the released state.

Since the transmission 46a is a speed increasing transmission, the holding force acting on the output member 38a by the brake element <NUM> is substantially lower than if the brake element <NUM> would act on the door leaf <NUM> directly. This enables the rating of the brake device 12a to be reduced.

In this example, the brake element <NUM> (here the magnetic target section <NUM>) is in contact with the pole pieces <NUM> in the braking position <NUM>. The mechanical stop <NUM> and the pole pieces <NUM> thus define two distinct positions for the released position <NUM> and the braking position <NUM>, respectively.

In order to release the brake device 12a, the control system <NUM> sends a first current pulse through the electric coil <NUM>. A first magnetic field is thereby generated that causes the soft magnet <NUM> to change polarity or flip from the second polarity back to the first polarity. When the soft magnet <NUM> adopts the first polarity, the hard magnet <NUM> and the soft magnet <NUM> again have opposing magnetizations such that the EPM <NUM> adopts the off state producing no net external field across the pole pieces <NUM>. The magnetic force from the EPM <NUM> acting on the magnetic target section <NUM> thereby ceases and the releasing spring <NUM> forces the brake element <NUM> to move from the braking position <NUM> back to the released position <NUM>. When the door leaf <NUM> moves from the open position <NUM> back to the closed position <NUM>, electric energy is harvested by the generator <NUM>.

<FIG> schematically represents the EPM <NUM> and the control system <NUM>. In <FIG>, the stator <NUM> of the generator <NUM> can also be seen. The control system <NUM> further comprises a driver <NUM>. The driver <NUM> is configured to apply the first current pulse and the second current pulse to the electric coil <NUM> for switching the polarity of the soft magnet <NUM>.

The control system <NUM> further comprises a capacitor <NUM>, a normally open switch <NUM> and a normally closed switch <NUM>. Also the capacitor <NUM> is configured to apply a first current pulse to the electric coil <NUM> to switch the soft magnet <NUM> from the second polarity to the first polarity, i.e. to switch the EPM <NUM> from the on state to the off state. The capacitor <NUM> is used for emergency closing of the door leaf <NUM>.

The normally open switch <NUM> is connected in series with the driver <NUM> and the electric coil <NUM>. The normally open switch <NUM> is an electrically controlled switch. With no voltage applied, the normally open switch <NUM> is open. With a (positive) voltage applied to its control pin, the normally open switch <NUM> is closed. The normally open switch <NUM> can be implemented using an enhancement mode MOS transistor.

The normally closed switch <NUM> is connected in series with the capacitor <NUM> and the electric coil <NUM>. The normally closed switch <NUM> is an electrically controlled switch. With no voltage applied, the normally closed switch <NUM> is closed. With a (positive) voltage applied to its control pin, the normally closed switch <NUM> is open. The normally closed switch <NUM> can be implemented using a depletion mode MOS transistor.

<FIG> further shows a control voltage V+. The control voltage V+ may for example be +<NUM> V.

The control system <NUM> of this example further comprises a normally closed manual switch <NUM>. The manual switch <NUM> may be used to manually close the door leaf <NUM> and also to test the functionality of the control system <NUM>.

The control system <NUM> further comprises a diode <NUM> and an electric resistor <NUM>. The resistor <NUM> functions to set a proper charging current for the capacitor <NUM>.

In <FIG>, the control system <NUM> is in a normal mode where a power supply is available, e.g. from a battery or a mains power supply. In the normal mode, the normally open switch <NUM> is closed and the normally closed switch <NUM> is open. The EPM <NUM> is thereby connected to the driver <NUM>, and the capacitor <NUM> is charged and disconnected from the EPM <NUM>.

The control system <NUM> of this example further comprises a data processing device <NUM> and a memory <NUM>. The memory <NUM> comprises a computer program stored thereon. The computer program comprises program code which, when executed by the data processing device <NUM> causes the data processing device <NUM> to perform, or command performance of, various steps as described herein. The data processing device <NUM> may for example command the driver <NUM> to send the first pulse and the second pulse to effect the switching of the EPM <NUM> to the off state and the on state, respectively. Moreover, the data processing device <NUM> may monitor a time period during which the brake device 12a should be in the braking state to hold the door leaf <NUM> in an open position <NUM>.

The control system <NUM> further comprises energy harvesting electronics including an electric energy storage device, here exemplified as a harvesting capacitor <NUM>, and four harvesting diodes <NUM> arranged in a diode bridge. The harvesting diodes <NUM> are arranged to rectify the voltage from the generator <NUM>.

The control system <NUM> further comprises a disconnection switch <NUM> and a shorting switch <NUM>. Each of the disconnection switch <NUM> and the shorting switch <NUM> is controlled by the driver <NUM>. <FIG> further shows a positive line <NUM> and a ground line <NUM>. The positive line <NUM> and the ground line <NUM> are connected to respective terminals of the generator <NUM>. In this example, the disconnection switch <NUM> is provided on the positive line <NUM>. Each of the disconnection switch <NUM> and the shorting switch <NUM> may be implemented using a transistor, such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor).

The disconnection switch <NUM> is arranged to selectively disconnect the generator <NUM>. When the disconnection switch <NUM> is open, the electric resistance becomes high, and the door leaf <NUM> moves relatively easily, in comparison with when moving the door leaf <NUM> to harvest electric energy.

The shorting switch <NUM> is arranged to selectively short-circuiting the terminals of the generator <NUM> over an electric harvesting resistor <NUM>. When the shorting switch <NUM> is closed, the harvested electric energy is converted to heat in the harvesting resistor <NUM>. The door leaf <NUM> then moves heavily in comparison with when the door leaf <NUM> moves to harvest electric energy. Thus, when the shorting switch <NUM> is closed, a high counter torque is provided in the generator <NUM>, making the rotor <NUM> heavy to rotate by means of movement of the door leaf <NUM>.

By selectively controlling the disconnection switch <NUM> and the shorting switch <NUM>, the control system <NUM> can selectively change an electric load of the generator <NUM> to control the movement of the door leaf <NUM>. The generator <NUM> thereby functions as an electronic brake.

<FIG> schematically represents the EPM <NUM> and the control system <NUM> when a power supply is lost. The power loss may for example be caused by a fire alarm system, a power outage or a burglar alarm. The normally closed switch <NUM> is thereby closed and the normally open switch <NUM> is thereby opened.

When the power supply is lost, the control system <NUM> enters an emergency mode. The control voltage is then <NUM> V. In the emergency mode (or if the manual switch <NUM> is opened), the EPM <NUM> is disconnected from the driver <NUM> and the capacitor <NUM> is connected to the EPM <NUM>. The discharge current from the capacitor <NUM> will ensure the soft magnet <NUM> adopts the first polarity, regardless of its initial polarity. The EPM <NUM> will thereby adopt the off state. As a consequence, it is ensured that the brake element <NUM> is in, or adopts, the released position <NUM> to release the door leaf <NUM>. The diode <NUM> blocks the capacitor voltage from activating the normally closed switch <NUM> and the normally open switch <NUM>.

The brake device 12a will always adopt the released state and the door leaf <NUM> will always be closed when the power supply is lost. By switching the manual switch <NUM>, the same event as during power loss takes place.

In order to provide a safeguard against single component failure (both open circuit and short circuit failures), most components of the control system <NUM>, such as the normally closed switch <NUM>, the normally open switch <NUM> and the capacitor <NUM>, may be quadrupled and be arranged in a serial-parallel configuration.

<FIG> schematically represents an access member system <NUM>. The access member system <NUM> comprises the arrangement 10a which in turn comprises the brake device 12a. In addition to the door leaf <NUM>, the access member system <NUM> further comprises a frame <NUM> and a door hinge <NUM>. The door leaf <NUM> is rotatable relative to the frame <NUM> about the door hinge <NUM>. In <FIG>, the door leaf <NUM> is in an open position <NUM>. The first gear wheel <NUM> is here concentric with the door hinge <NUM>. The brake device 12a is provided inside the frame <NUM>.

As shown in <FIG>, the arrangement 10a further comprises a closing spring <NUM>. One end of the closing spring <NUM> is connected to the door leaf <NUM> and one end of the closing spring <NUM> is connected to the frame <NUM>. The closing spring <NUM> forces the door leaf <NUM> towards the closed position <NUM>. The door leaf <NUM> can thus be opened against the force of the closing spring <NUM>. The holding time during which the brake device 12a is in the braking state to hold the door leaf <NUM> may for example be <NUM> to <NUM>.

<FIG> schematically represents a further arrangement 10b comprising a further brake device 12b. Mainly differences with respect to <FIG> will be described.

The arrangement 10b comprises a transmission 46b. The transmission 46b differs from the transmission 46a in that the transmission 46b comprises a freewheel device <NUM>. The freewheel device <NUM> of this example comprises a drive member <NUM> and a driven member <NUM>. The drive member <NUM> is fixed to the door leaf <NUM>. The driven member <NUM> is fixed to the first gear wheel <NUM>. When the drive member <NUM> rotates in the clockwise direction (according to <FIG>), the driven member <NUM> is not driven by the drive member <NUM>. When the drive member <NUM> rotates in the counterclockwise direction (according to <FIG>), the driven member <NUM> is driven by the drive member <NUM>. The freewheel device <NUM> is thus configured to freewheel when the door leaf <NUM> moves in the opening direction <NUM>.

By means of the freewheel device <NUM>, it is always possible to open the door leaf <NUM>. Moreover, the freewheel device <NUM> enables the door leaf <NUM> to be opened more even if the brake device 12b is in the braking state.

Claim 1:
A brake device (12a, 12b) comprising:
- a hard magnet (<NUM>);
- a soft magnet (<NUM>) configured to switch polarity between a first polarity and a second polarity when being subjected to a magnetic field and configured to maintain the polarity when the magnetic field is removed;
- an electric coil (<NUM>) located around the soft magnet (<NUM>);
- an electric control system (<NUM>) configured to apply a current pulse to the electric coil (<NUM>) to generate the magnetic field for changing the polarization of the soft magnet (<NUM>); and
- a brake element (<NUM>) comprising a magnetic target section (<NUM>), the brake element (<NUM>) being arranged to move to a released position (<NUM>) when the soft magnet (<NUM>) adopts the first polarity, and arranged to move to a braking position (<NUM>) due to a magnetic field generated by the hard magnet (<NUM>) and the soft magnet (<NUM>) in combination and acting on the magnetic target section (<NUM>) when the soft magnet (<NUM>) adopts the second polarity.