Door latch

Abstract: Lock for doors, for example door of homes, offices, hotel rooms or similar, as well as doors of motor vehicles, comprising lock opening control means, comprising a control device (5) located at a distance from the lock (3) and a mechanical transmission connecting the control device (5) to the lock (3). A shape memory actuator (6) being arranged in between said mechanical transmission, so that the lock (3) can be opened both by operating the shape memory actuator (6), and by operating said control device (5), in which case the shape memory actuator (6) works simply as a mechanical transmission element.

Description: This invention relates to locks for doors, for example doors of homes, offices, hotel rooms or similar, as well as doors of motor vehicles. Over the past years, electrically operated locks have been increasingly common, for example for hotel room doors. A similar diffusion of electrically operated locks is foreseen for the future for the doors of motor vehicles. Also in the case when an electrically operated lock is used, for reasons of safety, a mechanical device for opening the door from the inside must be provided. This is also the case of a door, a rear tailgate or rear lid of a motor vehicle, where required, to allow the occupant to exit by means of a mechanical action only. The purpose of this invention is to make a lock of the type described above which incorporates in a particularly simple and efficient way both the electrical operating means and the internal mechanical release means. In order to attain this purpose, this invention relates to a lock for doors, for example doors of homes, offices, hotel rooms or similar, as well as the doors of motor vehicles, comprising control means for opening the lock, wherein said control means include a shape memory actuator. Such a lock is known from DE-A-4 203 635. According to the invention, the control means of the lock includes a control device located at a distance from the lock and a mechanical transmission, which connects the control device to the lock, said shape memory actuator being arranged in between said mechanical transmission, externally with respect to the lock, in such as way that the lock can be opened both by operating the shape memory actuator, both by acting on said control device, in which case the shape memory actuator acts simply as a mechanical device belonging to said transmission. The use of actuating means made of shape memory metallic alloys, typically nickel and titanium, has been known for some time. Such elements deform when a predetermined transition temperature is reached, for example in the order of 100°C. In the preferred form of embodiment of this invention, said shape memory actuator comprises a shape memory metal wire, arranged in between said mechanical transmission, and means for supplying electrical current through the wire, thus heating it and causing it to contract. Thanks to said characteristics, as mentioned, the lock can be opened both electrically, causing electrical current to cross the shape memory wire, and mechanically, by acting on the remote control device, in which case the shape memory wire is simply a mechanical transmission device. Said electrical power means comprise a control unit for causing the passage of current through the shape memory wire following the operation of a control device, for example a device which can be operated by means of a mechanical or electronic key. Also in the case of the preferred form of embodiment of this invention, the electrical power means include a PTC component for cutting off the passage of current through the wire when a predetermined temperature is reached. Thanks to this characteristic, the control generated by said control unit causes the shape memory wire to warm up, after which the system automatically cuts off the passage of current through the wire. Again in a practical form of embodiment, the shape memory wire can be surrounded by an isolating sheath. Both extremities of this sheath may be connected to adjacent elements of said mechanical transmission, by which it contributes to transmitting the force when the lock is opened mechanically by operating the control device. A specific example of application of this invention refers to the case of a tailgate or rear lid of a motor vehicle, in which case the control device consists of, for example, an operating lever arranged near the driver's seat, and the shape memory wire is arranged in between the mechanical connection between said operating lever and the lock on the tailgate or rear lid. In alternative application, the control device is a safety wire arranged inside the tailgate for letting out occupants. Another possible application is that of a side door of a motor vehicle, in which case the control device consists of a handle for opening the door from the inside, while the control unit is controlled by the lock provided for opening the door from the outside. This invention will be better explained by the following detailed descriptions with reference to the accompanying figure as non-limiting example, whereas: figure 1 is a prospective schematic view illustrating a first form of embodiment of the lock according to this invention, applied to a tailgate of a motor vehicle, figure 2 is an extended scaled view of the lock arrangement and respective control in figure 1, figure 3 illustrates a second form of embodiment of this invention applied to the side door of a motor vehicle, figure 4 is an extended schematic view of the arrangement in figure 3 and With reference to figures 1, 2, numeral 1 indicates a motor vehicle with a tailgate 2 fitting a lock 3. The lock 3 can be operated either electrically or by means of a mechanical transmission 4, consisting of a flexible wire, which leads to an operating lever 5 arranged near the driver's seat. The electrical operation of the lock is permitted by a shape memory wire 6 (figure 2) which is connected in series between the flexible steel wire 4 and the mechanism of the lock 3. The lock can be controlled electrically from the outside, causing the passage of current through the shape memory wire 6. This result can be obtained by means of a control device arranged outside the tailgate, consisting of a lock which can be operated by means of a key, which supplies current to the shape memory wire 6. Naturally, the key may be electronic or replaced, for example, by an infrared or ultrasound remote control device. At the same time, the lock according to this invention can be opened from the inside by acting on the mechanical transmission 4 by means of the operating lever 5. In this case, the shape memory wire acts simply as a mechanical transmission device, transmitting the attraction impressed on the wire 4 to the controlled device inside the lock 3. Figure 3 refers to a second form of embodiment applied to a side door of a motor vehicle. The lock 3 is fitted on the door and is destined to co-operate with a striker fitted on the chassis of the motor vehicle. The lock 3 can be opened mechanically from the inside, by means of the control lever 5, connected to the mechanism of the lock 3 by a mechanical transmission consisting of a rod 4, arranged in series with a shape memory wire 6. As can be seen in figure 4, the rod 4 is connected both to the wire 6 and to a isolating sheath 6a surrounding said wire. On the opposite extremity, the shape memory wire 6 is connected to the device controlled by the lock. Furthermore, it is electrically connected to the battery of the motor vehicle by means of a PTC component, for cutting off the passage of current when a predetermined temperature is reached. The electrical power through the shape memory wire is controlled by an electronic control unit 7 which is operated following a signal 8 generated by introducing a key, electronic card, or any other control device (for example, a digital recognition device). The control unit 7 is also activated by a signal 9 generated by operating the handle on the outside of the door. Furthermore, a signal 9 and a signal 10 are sent by the control unit 7 to the dashboard instrument panel of the motor vehicle, respectively, for signalling the open or closed condition of the door and for signalling locked condition of the lock. Whenever a key is introduced in the lock on the outside of the door and the external handle of the door is operated, the shape memory wire 6 is rapidly heated following the passage of current. This passage is cut off by the PTC component when a predetermined temperature is reached. During this operating phase, the rod 4 is stopped and the shape memory wire 6 contracts, causing the lock 3 to open. Conversely, the lock 3 can be opened at any time by means of the mechanical transmission 4, in which case the shape memory wire 6 acts solely as a mechanical transmission device by operating the internal lever 5. A safety wire for mechanically opening the door from the inside can be provided inside the tailgate 2 for letting out the occupants locked inside. In this case, the wire is connected in series to a shape memory actuator. Naturally, numerous changes can be implemented to the construction and forms of embodiment of the invention herein envisaged, all comprised within the context of the concept characterising this invention, as defined in the claims.

Claims: Lock for doors, for example doors of homes, offices, hotel rooms or similar, as well as doors of motor vehicles, comprising lock opening control means, wherein said control means include a shape memory actuator (6), characterised in that said control means include a control device (5) located at a distance from the lock (3) and a mechanical transmission (4) connecting the control device (5) to the lock (3), said shape memory actuator (6) being arranged in between said mechanical transmission (4), externally with respect to said lock (3), so that the lock (3) can be opened both by operating the shape memory actuator (6), and by operating said control device (5), in which case the shape memory actuator (6) works simply as a mechanical element belonging to said transmission (4). Lock according to claim 1, characterised in that said shape memory actuator (6) comprising a shape memory wire arranged in between said mechanical transmission (4) and means for supply electrical current through the wire (6), so to heat it and make it contract. Lock according to claim 2, characterised in that said electrical power means comprise a control unit (7) for causing the passage of current through the shape memory wire (6) following the operation of a control device, for example a device which can be operated by means of a mechanical key, an electronic key or similar. Lock according to claim 2, characterised in that said electrical power means comprise a PTC control for cutting off the passage of current through the wire (6) when a predetermined temperature is reached. Lock according to claim 2, characterised in that the wire is surrounded by an isolating sheath (6a). Lock according to claim 5, characterised in that both extremities of the sheath (6a) are connected to adjacent elements of said mechanical transmission (4), by which said sheath (6a) contributes to transmitting the force when the lock is mechanically operated by means of said control device (5). Lock according to claim 2, characterised in that it is associated to the tailgate or rear lid (2) of a motor vehicle, said control device (5) being destined to be arranged near the driver's seat and said mechanical transmission consisting of a flexible wire (4) connected in series to the shape memory wire (9). Lock according to claim 3, characterised in that it is associated to a side door of a motor vehicle, said control device (5) consisting of a handle for opening the door from the inside, said electronic control unit being activated by means of a control device consisting of a lock arranged on the outside of the door. Lock according to claim 2, characterised in that it is associated to the tailgate or rear lid (2) of a motor vehicle, said control device (5) consisting of a control wire arranged inside the tailgate and connected in series to a shape memory actuator (9).

Inventors: ALACQUA STEFANO, BUTERA FRANCESCO, ALACQUA, STEFANO, BUTERA, FRANCESCO
Applicants: FIAT RICERCHE, C.R.F. SOCIETA CONSORTILE PER AZIONI
Application year: 2001
Main classification: E05B47
IPC codes: E05B47, E05B53, E05B65