Field of Invention

The invention refers to a device for detecting and indicating a door lock status, a kit of parts comprising a key, a door lock and a device for detecting and indicating a door lock status, and a method of operating a device for detecting and indicating a door lock status.

Prior Art

Locking a door is a routine operation that people carry out subconsciously. However, when we get away from the door, we often start wondering whether we have locked the door or not. This is a stressful situation and we sometimes go check whether the door is really locked. This is why devices have been developed, which detect and record a door lock status; we can be reassured to have locked the door thanks to an indicator in the device indicating the door lock status.

A device of this type is disclosed in document US 2009/0293567 Al. The device electronically tracks the use of a key to lock and unlock a door and retains information of the status. The user is able to query about the recorded door lock status. The device includes an actuating arrangement to allow tracking of the key position during a locking or unlocking motion of the key. These tracked signals are evaluated relative to at least two known signals indicative of a locking movement or an unlocking movement. The user is able to query the door lock status at a later point.

In locks that lock from both sides, rotation of a key to the right on one side of a door lock represents locking, while rotation of the key to the right on the other side represents unlocking of the lock and vice versa. Known devices do not allow detecting of a door look status depending on the side of the lock, from which the door was locked.

Technical Problem

The technical problem is how to configure a device for detecting and indicating a door lock status that would detect a correct status regardless of the side, from which a door lock was locked.

Solution to the Technical Problem

The technical problem is solved by a device for detecting and indicating a door lock status, comprising:

a housing that can be fastened to a key head by means of a first fastening means, and an electronic unit arranged within the housing and further comprising:

a printed circuit board,

at least one LED,

a motion sensor,

a magnetic field density sensor,

a microcontroller,

a battery, and

a push button.

When the device is in use, the housing is fastened to the key head. The motion sensor detects key orientation and a direction of key rotation within the lock. The magnetic field density sensor detects the magnetic field density and determines, from which side of the lock the door was locked in dependence on the detected magnetic field density. The magnetic field density sensor can detect the direction of key rotation within the lock instead of the motion sensor. A source of the magnetic field can be either the geomagnetic field or at least one permanent magnet. Prior to the first use, the device must be calibrated by keeping the push button depressed for several seconds in order to determine a threshold value of the magnetic field density. The detected direction of key rotation within the lock is recorded in a memory of the microcontroller. The lock status can be checked by pushing the push button and verifying the LED’s light signal.

The device can further comprise a permanent magnet that can be fastened to a lock or door by means of a third fastening means. Here, the magnetic field source is the permanent magnet.

In a further embodiment, the device comprises two permanent magnets, of which one is arranged on the external side of the door and the other on the internal side of the door such that they face each other with their opposite poles.

The invention further refers to a kit comprising a key, a door lock and a device for detecting and indicating a door lock status.

An advantage of the device of the invention over known devices lies in the fact that it correctly detects a change in the door lock status regardless of the side, from which the lock was locked/unlocked and also regardless of the number of keys used for locking and unlocking one lock. A further advantage is a simple, low-cost construction of the device and its reliable operation.

Figure 1 : Electronic unit housing fastened on a key

Figure 2: Key with the electronic unit, exploded view

Figure 3: Printed circuit board of the electronic unit from one side

Figure 4: Printed circuit board of the electronic unit from the other side

Figure 5: Lock and key with the device for detecting and indicating a door lock status The invention is described by way of several embodiments in more detail hereinbelow.

A device for detecting and indicating a door lock status comprises:

a housing 2 that can be fastened to a key 3 head by means of a first fastening means, and

an electronic unit arranged within the housing and further comprising:

a printed circuit board 5,

at least one LED 6,

a motion sensor 7,

a magnetic field density sensor 8,

a microcontroller 9,

a battery 10, and

a push button 11.

In a preferred embodiment, the housing 2 is disc-shaped. It comprises two plastic parts. A first portion 2a of the housing is intended to be fastened to a head of the key 3 by means of a first fastening means, such as a double-sided adhesive tape or a first screw 2d and a first nut 2e. The first nut can be integrated in the first portion of the housing. A hole on the key head can be used for the first screw to pass through. A second portion 2b of the housing functions as a detachable cover protecting the electronic unit and can be removed if needed (e. g. for replacing the battery). The first portion 2a of the housing and the second portion 2b of the housing can be coupled to each other by means of a second fastening means formed as a snap-in connection or of at least one second screw 2f and at least one nut 2h. The housing can further comprise an annular portion 2g, with which the housing can be connected to a keychain.

The source of the magnetic field is the geomagnetic field. Alternatively, the magnetic field source can be a permanent magnet. In this case, the device further comprises a permanent magnet 4 that can be fastened to a lock or door by means of a third fastening means.

In a further embodiment, the device comprises two permanent magnets, of which one is arranged on the external side of the door and the other on the internal side of the door such that they face each other with their opposite poles.

The permanent magnet 4 is intended for fastening to a lock or door by means of a third fastening means such as a double-sided adhesive tape or a third screw and is intended to designate the side of the lock/door.

All other components of the electronic unit are connected by means of a printed circuit board 5.

The motion sensor 7 is configured to detect orientation of the key. The motion sensor can be selected among an accelerometer, a combination of a gyroscope and an accelerometer, a gyroscope. A direction of key rotation within a lock can be detected by a motion sensor or a magnetic field density sensor.

A push button 11 is configured for calibrating the device prior to first use. The device is calibrated as follows: the key is inserted into a lock, the push button is kept depressed for a predetermined period of time (e. g. 5 seconds), and the key is rotated within the lock by 360° in direction of door lock locking, wherein at least one LED signalizes calibration start/stop (e. g. by a blink). The push button 11 is further configured to check the door lock status which is signalized by means of at least one LED 6.

The battery 10 (e. g. CR1632) supplies all components of the electronic unit. By means of its standard function of the controller (e. g. LVD - low voltage detection), the device can perform a function of detecting whether the battery will soon be empty and signalizes it by blinking the LED 6 when the door lock status is checked.

The microcontroller 9 manages the signals. It receives signals from the motion sensor 7, the magnetic field density sensor 8 and the push button 11, processes them and sends them to at least one LED 6. The microcontroller can comprise a non-volatile memory to preserve data in case of power failure (e. g. EEPROM). In this case, the calibration data are preserved even in case of power failure (e. g. upon battery replacement) and re-calibration is not necessary. The microcontroller is adapted to store the door lock status data for a predetermined period of time (e. g. 4 hours), the data is then deleted. The purpose of this function is to prevent storage of obsolete data in the event of a plurality of keys for the same lock and used by various users.

The microcontroller 9 can function in three operating modes: normal mode, low- power mode, sleep mode. The normal operating mode is active in locking, unlocking and calibration when signals from the sensors are obtained. It functions in the low- power mode, in which the internal clock of the microcontroller functions when the user wants to retrieve the data on a door lock status. The microcontroller passes from the low-power mode to the normal operating mode at a certain condition, e. g. when an interruption signal is received from the motion sensor, which indicates that the key is oriented in a direction identical to the direction of the key when inserted in the lock. The microcontroller can pass to a low-power mode when the key is oriented for a certain period of time (e. g. 3 seconds) in a direction indicating that the key cannot be in the lock or when the key is still for a certain period of time (e. g. 10 seconds); it returns to the operating mode when it receives an interruption signal from the motion sensor signalizing vibrations. The microcontroller can pass to a sleep mode when the device for detecting and indicating the door lock status on the key is still for a certain period of time and leaves this mode when the key is lifted/moved from a standstill. The LED 6 is intended to indicate the door lock status. There may be only one (e. g. a white LED) which emits light when the user pushes the push button and the lock is locked. There are preferably two LEDs (e. g. green and red). When the user pushes the push button and the lock is locked, the green diode goes on, otherwise the red one goes on if the lock is unlocked. If the diode blinks twice, it indicates that a predetermined time has elapsed, in which the microcontroller memorizes the door lock status. The diodes also signalize other statuses, such as battery status (almost empty), calibration start/end, etc.

The magnetic field density sensor, e. g. a Hall sensor or a MEMS magnetic field density sensor, can be used to detect, from which side of the lock the key is inserted.

The magnetic field density sensor can measure the geomagnetic field polarised in north-south direction, while the sensor detects the direction, in which the key is oriented, for example: the key is oriented towards north on one side of the lock, while it is turned to the south on the other side. With the key inserted in the lock, the observed axis is parallel to the key axis and the sensor detects a direction in all conditions unless the door is oriented in the east-west direction. In this case, the microcontroller detects upon calibration that the measured value of the magnetic field density is weak in this direction and uses another axis oriented in the north-south direction. So, when the observed axis is perpendicular to the direction of the key insertion, the position of the key inserted in the lock should be taken into consideration (either identically as during calibration or oriented by 180°). The information is obtained from the third axis of the magnetic field density sensor or the accelerometer.

Alternatively, the magnetic field density sensor 8 can measure the magnetic field of the magnet which, when used, is attached to the lock or the door. A further embodiment comprises two permanent magnets, of which one is arranged on the external side of the lock or door and the other on the internal side of the lock or door such that they face each other with their opposite poles.

In one of the embodiments, the magnetic field density sensor assumes the role of a motion sensor. In this case, the magnetic field density sensor is a triaxial magnetic field density sensor. The microcontroller computes the direction of key rotation based on the magnetic field density measurements in individual axes.

The motion sensor is configured to detect whether the key orientation conforms to the key orientation when the key is in the lock, or to detect a direction of rotation.

When the motion sensor is selected as a combination of a gyroscope and an accelerometer, the first one detects a direction of rotation, while the latter detects orientation (if the key is in the lock).

When an accelerometer is selected as the motion sensor, it detects a direction of the key rotation and the orientation of the key when the key is in the lock.

When the magnetic field density sensor assumes the role of a motion sensor, the latter is a triaxial magnetic field density sensor 8 detecting both the key orientation and the direction of rotation. It also detects, from which side of the lock the key is inserted.

When a combination of an accelerator and a triaxial magnetic field density sensor is selected as the motion sensor, the first one detects key orientation, while the latter detects the direction of rotation and also detects, on which side of the lock the key is inserted.

When a combination of a gyroscope and a magnetic field density sensor is selected as the motion sensor, the magnetic field density sensor detects key orientation and also the side of the lock, from which the key is inserted. The gyroscope detects the direction of key rotation within the lock. The method for calibrating the device for detecting and indicating a door lock status comprises the steps:

- insertion of the key 3 into a lock of an unlocked door, holding the push button 11 for indicating the door lock status until the LED 6 starts blinking,

- detection of a direction of rotation by means of the motion sensor 7,

- detection of a value of the magnetic field density by means of the magnetic field density sensor 8,

- input of the value of the magnetic field density and the direction of rotation into the memory of the microcontroller 9.

The method for operation of the device for detecting and indicating a door lock status comprises the steps:

- switching the microcontroller 9 to the operating mode when the motion sensor 7 detects a horizontal orientation of the key 3, i. e. when the axis of the lock and the axis X are parallel, as a consequence of the key being inserted into the lock,

- measuring a value of the magnetic field density by means of the magnetic field density sensor 8,

- comparing the measured value of the magnetic field density with a predetermined threshold value of the magnetic field density by means of the microcontroller,

a) in case the geomagnetic field density is measured

- if the measured value of the geomagnetic field density is within the predetermined tolerance around the value of the geomagnetic field density measured during the calibration, this is interpreted as the key is inserted in the lock, wherein the sign of the measured value of the geomagnetic field density is indicative of the side of the door, from which the key is inserted into the lock,

b) in case one permanent magnet is used - if the measured value of the magnetic field density is higher or identical to the threshold value, this controller interprets it as if the key is inserted into the lock from the side, on which the permanent magnet 4 is fastened,

- if the measured value of the magnetic field density lies below the threshold value, this controller interprets it as if the key is inserted into the lock from the side which is opposite to the side, on which no permanent magnet 4 is fastened, or

c) in case two permanent magnets are used

- if the measured value of the magnetic field density is higher or identical to the threshold value, this controller interprets it as if the key is inserted into the lock, wherein the sign of the measured value of the geomagnetic field density determines the side of the door, from which the key is inserted in the lock,

- detecting motion by means of the motion sensor 7 while the key 3 in the lock is turned, wherein the microcontroller 9 changes the recorded door lock/unlock status provided that the motion sensor 7 has detected the key being rotated by 360° and depending on the side of the lock detected in the preceding step,

- switching the microcontroller 9 from the normal operating mode to a sleep mode when the motion sensor 7, after the key has been removed from the lock, detects that the axis X of the lock and the axis X are no longer parallel, i. e. the key is no longer in a horizontal position.

The predetermined threshold value is determined as 10% to 90%, preferably 40% to 60%, most preferably around 50% of the value of the magnetic field density measured at calibration.

The device for detecting and indicating a door lock status can further comprise Bluetooth for establishing connection with a smart phone via suitable application. The Bluetooth enables:

- transfer of data on the door lock status to a smart phone, - searching for the key in the vicinity by means of the smart phone and a dedicated software/application uploaded on the phone (the key location can be determined within a radius of 20 to 30 m),

- notification on the changed door lock status in case of several users (e. g. notification to a parent that the child has locked the door), etc., and

- wireless (e. g. Qi or AirFuel technologies) or contact charging of the device.