GB2281096A - Driving device - Google Patents

Abstract

A device is operable to move a member against bias using a first force and to retain the member using a reduced force. In particular a locking element 26 mounted on a door is attracted against the bias of springs 30 by the action of a magnetic coil 48 located in an assembly 42 mounted on the door surround. A reed switch/magnet arrangement is used to sense when the door is closed and to actuate means supplying power to the coil to attract the element 26 so that pins 46 engage formations 34 to lock the door - reduced power then being supplied to the coil to maintain locking. A flux sensor indicates when the door is locked. An oscillating power supply is used to set the power levels. <IMAGE>

Description

DRIVING DEVICES DESCRIPTION The present invention relates to driving devices and in particular to the use of such devices in locking arrangements intended to give a high level of security to a particular area or facility.

Within this specification the term door is to be taken to encompass any door, gate, window, lid or other means of closing a portal or preventing access to an area or a facility There are many environments in which it is necessary to have a secure locking arrangement preventing unauthorised access being made to an area or facility.

Examples of these are certain laboratories, offices or parts of offices, and, notably, areas in banks and building societies where money is handled.

It is important that any locking arrangement provided to secure access to such an area or facility is readily operable - preferably automatically or semiautomatically. At the same time it is highly desirable that the locking arrangement be fail safe - that is to say if it becomes inoperable it will fail to a condition enabling people within the secure area or facility to leave it.

Mechanical locking systems have been known for some time and in general those in which a bolt is spring biased into a locking position are felt to be insufficiently secure for the purpose now envisaged - it being possible for an intruder to obtain access past the lock in certain circumstances by simply pushing the spring loaded bolt out of its locking engagement with the keeper in which it is received.

Alternative forms of mechanical locking systems including bars or bolts which may be rotated or slotted into positions offer security against such unauthorised intrusion, however, they can be cumbersome and it may be time consuming for them to be moved both into and out of an operative locking position.

As a result there has been a move in recent years to electrically powered locking arrangements - that is to say locking arrangements in which a bolt or bolts are driven to an operative, locking, condition upon closure of an electric switch.

Difficulties which can arise when using the electrically powered locking systems known to the applicant include the relatively high power required to maintain the lock in an operative condition - that is to say if the lock is to be arranged to fail safe (enabling escape to be made from the secured facility or area) in the event of a power failure, The level of power continuously consumed with such systems when operative can lead to premature failure of the circuitry of the lock bolt driving device, discolouration and possibly even damage to the door and/or surrounds in which the lock is mounted.

Other difficulties which arise include controlling the locking mechanism to ensure that it is operated only when the door is closed, and, after the lock has been operational and that controlled access to the protected area or facility is preserved.

Objects of the invention include the provision of a driving device particularly but not exclusively of use in locking arrangements and which alleviate and/or overcome the above noted problems.

In one aspect the invention provides a device operable to move a member from a first position to which it is normally biased, to a second position in which it is held by the device, said device being arranged to apply a first force to move the member from said first to said second position and a second, lesser, force to hold the member in said second position.

Said member is preferably resiliently biased to said first position.

Said member may comprise a lock element moveable from a first position enabling a door with which the element is associated to be opened to a second position engaging a further lock element and preventing the door being opened whilst the driving device is operational.

In a second aspect the invention provides a locking arrangement including a locking element movable between first and second positions and normally biased to said first position, and a device for driving the locking element from said first to said second position against said bias, said driving device being operable to apply a first force to move the locking element from the first to the second position and a second, lesser, force to hold the locking element in said second position.

The locking element is preferably adapted to be mounted on or in a door, or door frame adjacent a door, and when the door is closed said locking element is moveable from said first to said second position in which second position the locking element engages a further part of the lock.

Desirably, the locking element is carried in or on a part of a frame associated with a door and said further lock part is carried in or on the door.

Preferably, driving device is associated with further lock part.

Advantageously, said further lock part includes one or more bolt members engagable in individually associated apertures in said locking element when the door is closed and said driving device is operated to move said locking element from said first to said second position.

With advantage, said driving device includes first means operable to prevent operation of said device if a door with which the arrangement is associated is not fully closed.

The driving device may include second means operable to indicate when the door is fully closed and the locking element and lock part are in locking engagement.

The locking element is, advantageously, of a magnetic material and said driving device incorporates a magnetic coil forming part of or associated with said further lock part, said coil being operable, when energised, to move the locking element from said first to said second position.

The driving device, preferably, includes circuitry operable to provide power to the coil initially sufficient to move the locking element from said first to said second position and then sufficient to hold the element in said second position Said circuitry preferably includes third means enabled, after a door with which the locking arrangement is associated has closed, to apply electrical power to said coil and fourth means subsequently enabled to reduce the power supplied to said coil.

Said fourth means may be driven to oscillate between a first state enabling the output of said third means to be applied to said coil and a second state preventing the output of said third means being applied to said coil.

Desirably, the mark-space ratio of the oscillation of said fourth means is selected such that the average power supplied to said coil by the driving device is reduced from a first, full, level to a level approximating one quarter of that first, full, level when said fourth means is operational.

Said first means usefully comprises a reed switch mounted adjacent the locking element and a permanent magnet carried adjacent the lock part, the proximity of the permanent magnet to the reed switch when the door is closed causing the reed switch to close and couple a power supply to the driving device.

Said second means may comprise a magnetic flux sensor mounted adjacent or forming part of said further lock part, which sensor is adapted, when said locking element and said lock part are engaged one with the other, to trigger illumination of an indicator lamp.

Said third means may comprise an amplifier the output of which is driven to apply continuous power to said coil when said reed switch is closed.

Desirably, said amplifier is enabled after a predetermined time delay following closure of the reed switch.

Said fourth means may comprise a further amplifier the output of which oscillates between said two states.

Desirably, said further amplifier is rendered operational in response to the output of said first amplifier, a delay timer being coupled between the output of said first amplifier and an input of said further amplifier such that said further amplifier is rendered operational after a pre-determined time delay.

The delay timer may comprise a third amplifier the inputs to which incorporate a capacitive element which becomes fully charged before said third amplifier is rendered operational enabling operation of said further amplifier.

Figure 1, schematically illustrates a door incorporating a locking arrangement embodying the present invention, Figure 2, illustrates parts of the locking arrangement shown in Figure 1 in more detail, Figure 3, schematically illustrates a driving device for the locking arrangement of Figures 1 and 2, and Figure 4 is a more detailed circuit diagram of the driving device illustrated schematically in Figure 3.

With reference now to the Figures.

A door 10 is hingeably mounted in a frame 12 and incorporates a locking arrangement embodying the present invention. A first part 14 of the locking arrangement is carried in the edge of the door opposed to the hinged edge of the door whilst a second part 16 of the arrangement is mounted in the door frame 12 adjacent the position of the part 14 when the door 10 is fully closed.

The locking arrangement further incorporates a switch 18 and an indicator lamp 20 shows schematically, to be carried in the wall adjacent the door frame.

It will be appreciated that the positions of the first and second parts 14 and 16 of the locking arrangements (in the door and frame) may be varied. They may be placed anywhere desired along the edge of the door, in the top or the bottom of the door. Furthermore it will be appreciated that a locking arrangement embodying the invention may include more than one pair or parts 14 and 16 - a plurality of associated pairs of parts 14 and 16 may be provided along the peripheral edges, top and bottom of the door if desired.

Figure 2 shows the first part 14 of the lock to comprise an assembly 22 in the form of an armature frame mounted flush with the edge of the door. A substantially centrally located recess 24 in the frame 22 houses an armature 26 of a suitable, magnetisable, material (e.g.

mild steel).

Armature 26 is held in the central recess 24 of frame 22 by bolts 28. Springs 30 coupled beteween the armature 26 and the base of the frame hold the armature with its face 32 generally flush with the edge of the door.

The face 32 of armature 26 is pierced by two apertures 34 spaced apart as shown and extending for a short distance (less than 5 mm) into the body of the armature 26.

Assembly 22 further includes a permanent magnet 36 mounted, as shown, adjacent the central recess of frame 24.

The second part 16 of the arrangement comprises a frame 38 let into the edge of the door frame 12 such that its outer face is generally flush with the door frame.

Frame 38 includes a subsequently centrally located aperture 40 in which is mounted an assembly 42 held rigidly in position by screws 44. The outermost face of assembly 42 is generally flush with the edge of the door frame.

Two shear pins 46 are provided in assembly 42 and extend from the outermost face thereon by approximately 2 to 3 mm. the shear pins 46 are, when the door is fully closed, in register with the apertures 34 on the face 32 of armature 26.

The assembly 42 includes an electromagnetic coil 48 and a hall effect sensor 50. Adjacent the central aperture of frame 38 there is provided a reed switch 52 which, when the door is closed, is substantially opposed to and in register with the permanent magnet 36.

Figure 3 illustrates, very schematically operation of a driving device for the lock arrangement so far described.

Switch 18 is, desirably, of a type normally biased closed and couples a power supply (not shown) to the reed switch 52 which, in turn, when closed supplies power to a voltage regulator 54. When switch 18 is closed and door 10 is fully closed the reed switch 52 will close (due to proximity of magnet 36) and supply power to the voltage regulator 54.

When enabled in this way voltage regulator 54 supplies power to the rest of the circuitry of the driving device. The circuitry includes a first delay timer 60 operable, after a predetermined period of time (say, three to four seconds) to energise a first amplifier 62. The output of amplifier 62 is fed via a second amplifier 64 to coil 48 to cause that coil to be energised and move armature 26 against the action of the springs 30 such that the faces of the armature 26 and coil assembly 42 engage one another with the shear pins 46 received in the apertures 34.

The output of amplifier 62 is also fed, by via second delay timer 66, to the second amplifier 64 which, when energised, , acts to interrupt power supply from amplifier 62 to coil 48. Second amplifier 64 is configured to operate as an oscillator running at a frequency above that normally heard - that is to say above about 16KHz.

The mark-space ratio of the oscillator 64 is selected such that the average power supplied to coil 48 from amplifier 62 is reduced by approximately 75% The hall effect sensor 50, in the coil assembly 42, is also powered by voltage regulator 54 and will, in response to the increased magnetic field passing therethrough when the armature assembly 26 is in contact with the coil assembly 42 act to trigger a drive for the indicator lamp 20 so that lamp is lit to indicate the door is closed and that the locking arrangement is operational.

With the arrangement so far described switch 18 is normally CLOSED when the door 10 is fully closed the reed switch 52 will close energising voltage regulator 54 and so causing amplifier 62 to provide full power to the coil 48 after a time delay determined by the first time delay element 60.

Armature 26 is then pulled against the bias of the springs 30 so that the face 32 of the armature s contacts the face of the coil assembly 42. The shear pins 46 are received in the apertures 34 and the door carrying the locking arrangement is locked securely.

After a further short delay, caused by delay timer 66, oscillator/amplifier 64 becomes operational interrupting the power supply to the coil 48 from amplifier 62. the lower average power supply to coil 48 caused by operation of oscillator/amplifier 64 is sufficient to hold the armature assembly in contact with the coil assembly.

It is approximately 25% of that provided by amplifier 62 when running freely.

In order that the door be unlocked so that it may be opened it is simply necessary for switch 18 to be moved to its position, switched OPEN, so de-activating the driving device. All power to coil 48 is then cut off and the armature 26 moves away from the coil assembly 42 under the bias springs 30. Whilst switch 18 is held in the OPEN position door 10 may be opened.

Releasing switch 18 means that it will CLOSE once again re-arming the locking arrangement such that it becomes operational to lock and secure the door when the door is next fully closed.

Figure 4 shows a circuit diagram of the driving device schematically illustrated in Figure 3 in more detail.

As can be seen from Figure 4 coil 48 is shunted by a reverse surge diode 100 and is coupled between a positive supply rail 102 and the collector of a transistor 104, the emitter of which is coupled to a negative supply rail 106.

The base of transistor 104 is coupled to the centre tap of a voltage divider formed by resistors 108 and 110 in the emitter path of a transistor 112.

The collector of transistor 112 is coupled directly to the output of the voltage regulator 54 to which the base of transistor 112 is also coupled via a resistor 114.

The base of transistor 112 is further coupled by a diode 116 to the output of an operational amplifier 118.

Amplifier 118 has two inputs one of which, 118A, is coupled to the centre tap of a voltage divider formed by a pair of resistors 120 and 122 receiving the regulated voltage output of voltage regulator 54 by a resistor 124 and to the negative supply rail 106 by a capacitor 126. Resistor 124 is shunted by a diode 128.

The output of amplifier 118 is, as noted above, coupled to diode 116. This output is further coupled via a resistor 130 and capacitor 132 to the negative supply rail 106.

The junction of resistor 130 and capacitor 132 is taken to an input, 134A, of a second operational amplifier 134. Input 134A of amplifier 134 is further coupled by a diode 135 to the output of a voltage regulator 54.

The second input, 134B, to operational amplifier 134 is taken from the centre tap of the resistors 120 and 122.

The output of amplifier 134 is coupled via a diode 136 and capacitor 138 to the negative supply rail 106. The junction of diode 136 and capacitor 138 is fed to an input, 140A, of a third operational amplifier 140.

The other input, 140B, of amplifier 140 is coupled by resistor 142 to the centre tap of the voltage divider formed by the resistors 120 and 122.

The output of amplifier 140 is coupled by a resistor 144 to the input 140B, by a diode to the base of transistor 112 and by a diode 148 and resistor 150 to the input 140A of amplifier 140. As can be seen the junction of the diode 148 and resistor 150 is coupled to the negative supply rail by a resistor 152.

The Hall effect sensor 50 is coupled to a relay 154 in turn operable to light the indicator lamp 20 (not shown in Figure 4) whenever this sensor senses a flux level sufficiently high to indicate the coil and armature assemblies are in contact one with the other. The relay 154 although described as being operable to light a lamp 20 adjacent the door may, in certain circumstances, be arranged to operate a remote indicating lamp, counter or the like. Such an arrangement is desirable if the integrity of the door provided with the lock arrangement is being monitored centrally - i.e. remote from the door.

It will be appreciated that when switch 18 is OPEN no power is supplied to the driving device shown in Figure 4, transistor 104 will be OFF, and no power will be passed to the coil 48.

If one assumes now that switch 18 is CLOSED and, upon full closure of door 10, switch 52 closes, then voltage regulator 54 is energised and supplies power to the circuitry. In particular voltage regulator 54 sets reference voltages on the inputs 118A, 134B and 140B of the operational amplifiers 118, 134 and 140 respectively.

Immediately following switch 52 closing the output of amplifier 118 will be held LOW holding diode 116 conductive and pulling the base of transistor 112 LOW. As a result the base of transistor 104 will be held LOW and transistor 104 will be held OFF and no power will be supplied to coil 48.

The output of amplifier 134 will, at the same time, be held LOW holding diode 136 conductive (preventing capacitor 138 charging) and holding the input 140A of amplifier 140 LOW.

Whilst the voltage on input 140A of that amplifier 140 is less than the voltage of input 140B of that amplifier the output of amplifier 140 will be held HIGH. This HIGH voltage is blocked from passing to the base of transistor 112 by diode 146. Any current passing from the output of amplifier 140 will pass to the negative supply rail 106 via diode 148 and resistor 152.

After such a period of time (3 to 4 seconds) capacitor 126 will become charged (via resistor 124) to a level such that the voltage on input 118B of amplifier 118 is equal to or greater than the voltage on input 118A of that amplifier. As a result of change the output of amplifier 118 goes HIGH and diode 116 stops conducting.

Once diode 116 stops conducting the voltage on the base of transistor 112 goes HIGH (Being driven by the voltage regulator 54 via the resistor 114) and transistor 112 is biased conductive. As a result the voltage of the base of transistor 104 goes HIGH (it is coupled to the voltage divider formed by the resistors 108 and 110 in the emitter path of transistor 112).

Transistor 104 voltage will begin conducting and coil 48 will be energised.

The HIGH output voltage from the output of amplifier 118 begins to charge capacitor 132 and after a further time delay (desirably 3 to 4 seconds) capacitor 132 becomes fully charged. As a result the voltage on the input 134B of amplifier 134. This charge in condition drives the output of amplifier 134 HIGH, blocking diode 136 and allowing capacitor 138 to charge (via diode 148 and resistor 150) until the voltage on input 140A of amplifier 140 becomes equal to or greater than the voltage on input 140B of that amplifier.

At this time the output of amplifier 140 will be driven LOW - causing diode 146 to conduct. Whilst diode 146 is conducting the voltage on the base of transistor 112 is pulled LOW and transistor 112 will be turned OFF. As a result the base of transistor 104 will be pulled LOW (to the level of the supply rail 106) and transistor 104 will be turned OFF. Coil 48 is therefore de-energised.

Capacitor 138 discharges (via resistors 150 and 152 to the negative supply rail 106) until the voltage on input 140A of amplifier 140 is less than the voltage on input 140B of that amplifier. Once that condition is reached the output of amplifier 140 is driven HIGH blocking diode 146 again and causing transistors 112 and 104 to turn ON. The HIGH output of amplifier 140 allows capacitor 138 to re-charge (via diode 148 and resistor 150) until the voltage on input 140A of amplifier 140 is again greater than the voltage on input 140B of that amplifier and once again the output of the amplifier 140 will be driven LOW.

This oscillator of the amplifier 140 output between HIGH and LOW voltages continues until switch 18 goes OPEN and the driving device de-energised.

The feedback of the output of amplifier 140 (via resistor 144) to the output 140B of that amplifier effectively provides hysteresis to the circuitry enabling the amplifier 140 to be operated - as described - as an oscillator to say above about 16KHZ Again by appropriate selection of these elements the mark - space ratio of the oscillating output of amplifier 140 is selected such that the average power supplied to coil 48 via transistor 104 when amplifier 140 is oscillating is about 25% of the full power supplied to the coil 48 by transistor 104 when amplifier 140 is not operational.

When switch 18 is OPEN, or there is a power failure, the output of voltage regulator 54 will fall to zero, capacitor 126 will discharge via the resistors 150 and 152.

It will be appreciated that in this condition coil 48 is no longer being supplied with power and the armature assembly 26 will be moved away from a position engaging the magnetic coil by the bias of the springs 30.

Thus it will be appreciated that the locking mechanism of the present invention will "fail safe" - that is to say fail to a condition enabling the door with which the locking mechanism is associated to be readily opened by anybody within the area secured by the door.

It will be appreciated that the arrangement now described has significant advantages over the known arrangement for securing doors, and indeed in other areas of activity.

In particular it will be seen that the particular arrangements described enables a very high locking force to be obtained for a relatively low power consumption. A high initial operating power consumption of say 24 watts needed to carry the armature assembly into engagement with the coil assembly - is reduced by the pulsed operation thereafter of the driving device to an average holding power of approximately 25% of the full power required. As a result of this the mean coil temperature rise is relatively low - less than 200C.

Providing the magnetic coil in a one piece solid core - incorporating steel shear pins, enables this part of the locking mechanism, if desired, to be Suitably plated thereby enabling the locking mechanism to be used readily on exterior doors.

The particular form of driving device described has utility not simply for the particular form of locking mechanism in which an initial, high loading force is required top move a member from a first to a second position which member they may thereafter be held in that position by a relatively low holding force.

It will be appreciated that with the particular configuration of the arrangements described it is possible for a locking mechanism embodying the invention to be provided, safely, in environments where locking mechanism cannot normally be located.

By potting or encapsulating the driving device in a suitable resin compound - or moving it to a position remote from a mechanical parts of the locking mechanism it is possible, for example for the locking mechanism to be used under water or in an environment where liquids or gases usually prevent the use of such devices.

It will be appreciated that many modifications may be made to the described arrangements without departing from the scope of the present invention

Claims (23)

1. A device operable to move a member from a first position to which it is normally biased, to a second position in which it is held by the device, said device being arranged to apply a first force to move the member from said first to said second position and a second, lesser, force to hold the member in said second position.

2. A device as claimed in Claim 1, wherein said member is resiliently biased to said first position.

3. A device as claimed in Claim 1 or Claim 2, wherein said member is a lock element moveable from a first position enabling a door with which the element is associated to be opened to a second position engaging a further lock element and preventing the door being opened whilst the driving device is operational.

4. A locking arrangement including a locking element movable between first and second positions and normally biased to said first position, and a device for driving the locking element from said first to said second position against said bias, said driving device being operable to apply a first force to move the locking element from the first to the second position and a second, lesser, force to hold the locking element in said second position.

5. An arrangement as claimed in Claim 4, wherein the locking element is adapted to be mounted on or in a door, or door frame adjacent a door, and when the door is closed said locking element is moveable from said first to said second position in which second position the locking element engages a further part of the lock.

6. An arrangement as claimed in Claim 5, wherein the locking element is carried in or on a part of a frame associated with a door and said further lock part is carried in or on the door.

7. An arrangement as claimed in Claim 5 or Claim 6, wherein said driving device is associated with further lock part.

8. An arrangement as claimed in any one of claims 5 to 7, wherein said further lock part includes one or more bolt members engagable in individually associated apertures in said locking element when the door is closed and said driving device is operated to move said locking element from said first to said second position.

9. An arrangement as claimed in any one of claims 4 to 8, wherein said driving device includes first means operable to prevent operation of said device if a door with which the arrangement is associated is not fully closed.

10. An arrangement as claimed in any one of claims 4 to 8, wherein the driving device includes second means operable to indicate when the door is fully closed and the locking element and lock part are in locking engagement.

11. An arrangement as claimed in any one of claims 4 to 9, wherein the locking element is of a magnetic material and said driving device incorporates a magnetic coil forming part of or associated with said further lock part, said coil being operable, when energised, to move the locking element from said first to said second position.

12. An arrangement as claimed in Claim 11, wherein said driving device includes circuitry operable to provide power to the coil initially sufficient to move the locking element from said first to said second position and then sufficient to hold the element in said second position.

13. An arrangement as claimed in Claim 12 wherein said circuitry includes third means enabled, after a door with which the locking arrangement is associated has closed, to apply electrical power to said coil and fourth means subsequently enabled to reduce the power supplied to said coil.

14. An arrangement as claimed in Claim 13, wherein said fourth means is driven to oscillate between a first state enabling the output of said third means to be applied to said coil and a second state preventing the output of said third means being applied to said coil.

15. An arrangement as claimed in Claim 14, wherein the mark-space ratio of the oscillation of said fourth means is selected such that the average power supplied to said coil by the driving device is reduced from a first, full, level to a level approximating one quarter of that first, full, level when said fourth means is operational.

16. An arrangement as claimed in any one of claims 9 to 15, wherein said first means comprises a reed switch mounted adjacent the locking element and a permanent magnet carried adjacent the lock part, the proximity of the permanent magnet to the reed switch when the door is closed causing the reed switch to close and couple a power supply to the driving device.

17. An arrangement as claimed in any one of claims 10 to 16, wherein said second means comprises a magnetic flux sensor mounted adjacent or forming part of said further lock part, which sensor is adapted, when said locking element and said lock part are engaged one with the other, to trigger illumination of an indicator lamp.

18. An arrangement as claimed in Claim 16, or Claim 16 and Claim 17, wherein said third means comprises an amplifier the output of which is driven to apply continuous power to said coil when said reed switch is closed.

19. An arrangement as claimed in Claim 18, wherein said amplifier is enabled after a predetermined time delay following closure of the reed switch.

20. An arrangement as claimed in any one of claims 14 to 19, wherein said fourth means comprises a further amplifier the output of which oscillates between said two states.

21. An arrangement as claimed in Claim 20, wherein said further amplifier is rendered operational in response to the output of said first amplifier, a delay timer being coupled between the output of said first amplifier and an input of said further amplifier such that said further amplifier is rendered operational after a predetermined time delay.

22. An arrangement as claimed in Claim 1, wherein said delay timer comprises a third amplifier the inputs to which incorporate a capacitive element which becomes fully charged before said third amplifier is rendered operational enabling operation of said further amplifier.

23. A locking arrangement as claimed in Claim 4 and substantially as hereinbefore described with reference to the accompanying drawings.