AU2005272235A1 - Electrical lock actuable by variable current and/or variable voltage - Google Patents

Description

WO 2006/016822 PCT/NZ2005/000203 -1 Electrical lock actuable by variable current and/or variable voltage. FIELD OF INVENTION The present invention relates to an improved lock particularly though not solely limited to those that can be actuated electronically. 5 BACKGROUND OF INVENTION Many locks are known which rely upon an electrical drive for the purpose of enabling some remote travel of a locking device which has the effect of either locking or unlocking the lock to allow the door to be latched or unlatched. Most such locks have a power off failsafe (i.e. if power is lost the 10 lock is unlocked) or a power off fail secure (i.e. if power is lost the lock remains locked) situation reliant for example upon the ability of a bias to move the drive element of a solenoid assembly in the power off situation, that same drive component being able to override the bias when actuated in the power on situation. 15 Solenoids being one such electrical drive, hitherto have been actuated reliant upon a voltage based actuation of the solenoid thus meaning for different voltage availabilities there is the need to provide an inventory of different locks or at least different voltage solenoids to cover the variable voltage situations. Standard voltages in the industry and prior art for lock activation, control and 20 monitoring are nominally 12 and 24 volts DC (VDC). Such voltage controlled solenoids have another disadvantage in that quite apart from inventory requirements there is, even within a standard voltage situation, a great variation in voltage availability to a solenoid, when the lock is in a series of locks as may be the case in a hotel, motel, apartment block, 25 educational campus or prison. The locks, and hence solenoids, at the end of the series receive a significant voltage difference when compared to those locks at the head of the series due to the voltage drop along the cabling supply and/or across each lock. Such voltage drops can be accounted for, either by lower resistance cabling and or by voltage amplifiers along the series. However both WO 2006/016822 PCT/NZ2005/000203 -2 solutions are expensive and require extra installation. An example of a voltage controlled solenoid lock is that described in New Zealand Patent No. 517337. It is therefore an object of the present invention to provide a lock which will overcome at least one and preferably several, of any disadvantages in the 5 prior art or which will at least provide the public with a useful choice. BRIEF DESCRIPTION OF THE INVENTION Accordingly in a first aspect the present invention may be broadly said to consist in an actuator for a lock or a lock assembly comprising: a movable element, 10 drive means energisable to actuate said movable element from a first position to a second position, current sensing means for sensing the current supplied to said drive means, and a power supply for energising said drive means and providing current 15 control over the current in said drive means as sensed by said sensing means, in use supplying an actuating current to drive said moveable element from said first position to said second position, and thereafter providing a holding current to hold said member in said second position, said actuating current being higher than said holding current. 20 Preferably said current control is closed loop feedback. Preferably said current sensing means is a resistor. In a further aspect the present invention consists in an actuator for a lock comprising: a movable element, 25 drive means electrically energisable by a power supply to actuate said movable element between a first position and a second position, and a current controller to control the current supplied to said drive means, the controller having at least two current supply modes, a first current supply 30 mode (actuating current) to actuate the movable element via said drive WO 2006/016822 PCT/NZ2005/000203 -3 means from the first position to the second position and a second current supply mode (holding current) to hold said moveable element via said drive means in the second position, wherein the current supplied in the second mode is lower than the current supplied in said first mode. 5 Preferably there is a current sensing means arranged to sense the current supplied to said drive means. Preferably the current controller is arranged to control said current supplied to said drive means in response to the current sensed by said current sensing means. 10 in a second aspect the present invention may be said to broadly consist in a lock assembly that is electrically actuable by a drive means that operates at a voltage below the nominal line voltage of power supplied to said lock assembly, and controlling the actuation of said drive means by control of the current being made available to said drive means, said drive means directly or indirectly 15 controlling the locking and unlocking of said lock assembly. Preferably said drive means is a solenoid. Preferably said solenoid has a power off fail secure condition (e.g. under the action of a bias such as a spring) or a power off failsafe condition (e.g. under the action of a bias such as a spring). 20 Preferably said solenoid is an 8 volt rated solenoid which via current control can operate on a 12 to 24 volt direct current supply voltage. Preferably said solenoid is an 8 volt rated solenoid which via current control can operate on a 12 or 24 volt direct current supply voltage. Preferably said current is adjusted to maintain a constant force output 25 from said solenoid. Preferably said current is adjusted in relation to the stroke position of said solenoid to maintain a constant force output. Preferably said stroke position is monitored.

WO 2006/016822 PCT/NZ2005/000203 -4 Alternatively said force is varied to conform to a pre chosen force displacement profile and said current is adjusted accordingly to produce said force-displacement profile. In a third aspect the present invention consists in a lock assembly which 5 is electrically actuable via electrical drive means whose force of actuation is current dependent, said current being controlled to actuate said electrical drive means. Preferably said electrical drive means is a solenoid. Preferably said current is adjusted to maintain appropriate force output 10 from said solenoid. As the solenoid retracts, the air gap reduces, and the current needed for a given force reduces. This allows a closed holding force to be maintained with a lower current, and thus lower total system power. Preferably the stroke position of the solenoid is monitored by a position feedback sensor. 15 Preferably said solenoid has a power off failsecure condition (e.g. under the action of a bias such as a spring) or a power off failsafe condition (e.g. under the action of a bias such as a spring). Preferably said solenoid is an 8 volt rated solenoid which via current control can operate on a 12 to 24 volt direct current supply voltage. 20 Preferably said solenoid is an 8 volt rated solenoid which via current control can operate on a 12 or 24 volt direct current supply voltage. Preferably said current is adjusted to maintain a constant force output from said solenoid. Preferably said current is adjusted in relation to the stroke position of 25 said solenoid to maintain a constant force output. Alternatively said force is varied to conform to a pre chosen force displacement profile and said current is adjusted accordingly to produce aid force-displacement profile.

WO 2006/016822 PCT/NZ2005/000203 -5 In a fourth aspect the present invention consists in a method of control of an electrical drive means for a lock assembly wherein actuation of the drive means is controlled by varying the current to the drive means. Preferably said electrical drive means is a solenoid. 5 Preferably said solenoid has a power off fail secure condition (e.g. under the action of a bias such as a spring) or a power off failsafe condition (e.g. under the action of a bias such as a spring). Preferably said solenoid is an 8 volt rated solenoid which via current control can operate on a 12 to 24 volt direct current supply voltage. 10 Preferably said solenoid is an 8 volt rated solenoid which via current control can operate on a 12 or 24 volt direct current supply voltage. Preferably said current is adjusted to maintain a constant force output from said solenoid. Preferably said current is adjusted in relation to the stroke position of 15 said solenoid to maintain a constant force output. Preferably said stroke position is monitored. In one embodiment the stroke position of the solenoid is monitored by a combination optical and mechanical system where by when the solenoid plunger is fully retracted in a mechanical arm breaks an optical sensor beam. 20 Alternatively said force is varied to conform to a pre chosen force displacement profile and said current is adjusted accordingly to produce said force-displacement profile. In a fifth aspect the present invention consists in a method of control as herein described with reference to one or more of the accompanying drawings. 25 In a sixth aspect the present invention consists in a lock assembly as herein described with reference to one or more of the accompanying drawings. In a seventh aspect the present invention consists in a door with a lock assembly, as herein described, fitted, with reference to any one or more of the accompanying drawings.

WO 2006/016822 PCT/NZ2005/000203 -6 In an eighth aspect the present invention consists in a building with a lock assembly as herein described, fitted, with reference to any one or more of the accompanying drawings In a ninth aspect the present invention consists in a lock including an 5 actuator as herein described. In a tenth aspect the present invention consists in a building including a door with a lock as herein described. In an eleventh aspect the present invention consists in a plurality of locks as herein described wherein the locks have a common power supply supplying 10 electricity to each lock in series. The term 'comprising' as used in this specification and claims means 'consisting at least in part of, that is to say when interpreting statements in this specification and claims which include that term, the features, prefaced by that term in each statement, all need to be present but other features can also be 15 present. BRIEF DESCRITPION OF THE DRAWINGS The present invention will now be described with reference to the accompanying drawings wherein, Figure 1 is a front view of an electrically activated lock assembly with 20 the solenoid driving means in a contracted position, Figure 2 is a front view of an electrically activated lock assembly with the solenoid driving means in an extended position under the action of a biasing means, Figure 3 is an electronic block diagram of the present invention, 25 Figure 4 is a graph of a typical current and force displacement profile using the present invention, Figure 5 shows the typical current verses time profile for the present invention, and Figure 6 shows a building with a lock of the present invention installed 30 in a series of doors, and WO 2006/016822 PCT/NZ2005/000203 -7 Figure 7 shows a voltage verses distance profile for the door set, showing the voltage drop over the wiring and each door, and thus the requirement to have an able nominal operating voltage at the series beginning, to compensate for the drop over the series. 5 DETAILED DESCRIPTION OF THE INVENTION Preferred embodiments of the present invention will now be described. The actuator is generally indicated by 16. The actuator 16 comprises the movable element (which in the preferred embodiment is the locking bar 8), the drive means (which in the preferred embodiment is the solenoid 13, 300) and 10 current sensing means and power supply. This is all within the lock assembly 1. The power supply is remote from the lock assembly 1. The lock assembly 1 has a lock face 2 which is presented to be at the peripheral edge of the door (not shown). This allows the engagement of the latch bolt 19 within a complimentary receiving member in the door jamb. The lock 15 assembly 1 has a back region 4. The lock assembly 1 from the lock face 2 to the back 4 is or is to be recessed into the door periphery. This is also known as a mortice lock. The lock is reliant on an electrical power supply for its actuation (and control). The power supply can be internal or external. In the preferred 20 embodiment the power supply is externally supplied by wire. The lock assembly 1 consists of a lock housing 3 within which are housed the components of the lock assembly. Housed are a locking bar actuation means 5 which in this case is an electrically actuable drive means, solenoid 13 which consists of an external coil 14 and an internal core 15 which upon 25 application of electrical power to the external coil 14 drives the internal core 15 up into the external coil 14 (i.e. retraction, the said second position). Upon removal of power, such as when selectively removed or in the instance of a power failure, there is no attraction of the internal core 15 into the external coil 14 and under the action of a biasing means 6, in this case a coil spring, the 30 internal core 15 is urged out from the solenoid to extend there from (i.e. such WO 2006/016822 PCT/NZ2005/000203 -8 extension being, the said first position). Carried or actuated by the internal core 15 of the solenoid 13 is a drive plate 7 which is guided by a spigot 10. This enables rendering of the lock as failsafe or failsecure. The drive plate 7 in turn activates a locking bar 8 via a pinion gear 9 and 5 rack 11 selectively to block or unblock the latch bolt actuating means 12 dependent upon whether the lock is in a "failsafe" or "failsecure" configuration. Failsafe is defined as the lock being unlocked (and thus the lock is able to be actuated) when power is removed from the lock. Failsecure is defined as the lock being in a condition which is locked and thus the lock is unable to be 10 actuated) when power is removed from the lock. These states preferably are when the door is on the jamb (i.e. closed) but is not necessarily so. The locking bar 8 may prevent the latch bolt actuating means 12 from actuating the latch bolt 19. In the position shown in Figure 1 the locking bar 8 is withdrawn and not blocking the latch bolt actuator 12 and therefore the latch bolt 15 actuator 12 is unlocked, whilst in Figure 2 the locking bar 8 is blocking the latch bolt actuator 12 and thus the lock is in a locked condition. By locked is meant that a key or handle or other external device in the normal operation of the lock is unable to actuate the lock. We have determined that there is a significant performance variation 20 where identical locks are installed between the beginning of the series and the end of the series. This is due to the drop in voltage over the supply wire runs and the not insignificant drop in voltage across each lock itself. Due to the direct relationship between the voltage applied to the solenoid 13 and the force output as a result, varying voltage will result in varying force 25 applied by the solenoid 13. This can lead to, in a force sensitive application, the force applied being outside acceptable upper and/or lower limits to effect movement or reliable or desirable movement of the solenoid 13. This difference in force application means that in some situations there can be excessive wear of parts driven by the solenoid 13 due to excessive force and in other situations a 30 prospect of a lack of response because of a less than acceptable force being WO 2006/016822 PCT/NZ2005/000203 -9 capable of being provided by the voltage experienced. The result may be an increased force (and premature wear) on the solenoids 13 in the series already operating correctly and/or increased temperature rises in the solenoids 13, and/or a failure of the lock assembly 1 to operate correctly. 5 Another factor that we have determined is detrimental in the performance of voltage control solenoids 13 in such locking situations is that temperature changes greatly affect the force produced by even a constant voltage. The relationship of force to the turns in of a solenoid and temperature (when expressed as a relative change in degrees Celsius) can be expressed as follows: 10 F =f(N, I) where I= V/(R +aT) where a = Ohms/degree Therefore, when the number of turns (N) and voltage (V) is fixed, an increase in temperature (T) results in a decrease in applied force (F) by the solenoid (I decreases). We have determined that an operational lock typically might experience relative temperature variations of from 600C to 700C and these 15 variations can affect the relationship expressed above by at least 25% and sometimes at least 30% thereby in turn giving rise to significant variations in the force. Referring now to Figure 3 a circuit diagram illustrating the control of the solenoid 300 is shown. The solenoid 300 includes a magnetic coil 314 (the 20 external coil 14) to generate a magnetic field and movable magnetic member or plunger 315 (the internal core 15) which moves in response to the magnetic field operating thereon. The magnetic coil is operated by DC supply such that the plunger 315 is forced in a single direction and is biased by a spring 6 which forces the plunger 315 back in the opposite direction when the magnetic field is 25 not present. The DC supply voltage is supplied by controller 310 which in the preferred embodiment is by linear current regulation. The controller includes an N channel MOSFET transistor using negative feedback. The error voltage (difference between the reference Vref and voltage Vactu across the sense resistor 30 (current sensing means) ) is amplified by Av, and then applied to the MOSFET WO 2006/016822 PCT/NZ2005/000203 - 10 GATE terminal in such a polarity as to create a linear, stable operating point. The governing equation is normally Vg = Av * (Vref- Vactual); Taking a simple, typical example with a Gate voltage Vg of 2.5V, a linear 5 loop gain Av of 50 results in an error voltage of 50mV, which with a Ref Voltage Vref of 550mV, will give voltage drop Vactual of 500mV across the sense resistor. The resistance of the sense resistor is chosen to give 500mV drop at the appropriate current. A drop in the 500mV results in an increase in the gate voltage Vg, which works to increase voltage drop Vactual across the sense resistor 10 to compensate. In an alternative, the voltage supplied is a pulse width modulated (PWM) voltage which is varied in order to achieve a given set point current. The current sensing means is by methods known in the art. In the preferred embodiment current sensing means is by a sense resistor 311 (low value series resistor) 15 connected last in the series chain connected to the circuit ground OV and the voltage across the sense resistor 311 is provided to the controller 310. Thus, for the example given in Figure 5, when the solenoid 13 is desired to be actuated, a first current lactuate is provided for a period taotuate. Once the solenoid 13 has moved to its' operable position the current is reduced to I hold to hold tile solenoid 13 in 20 the operable position. The primary reason for different current levels, is the air gap that exists in the solenoid 13, on open (i.e. internal core 315, 15 extended), and is largely non-existent when closed as seen in Figure 4. Thus magnetic path efficiency is widely different. Holding force needs to be greater the net sum of spring force, 25 plus all mass-moments of the mechanism. It is different in the fail safe and fail secure configurations. The values for both the actuating current and holding current can be determined empirically, calculated depending on the solenoid used or alternatively by the use of a position sensor, and may be determined in real time. 30 In the preferred embodiment the parameters of the solenoid are known in WO 2006/016822 PCT/NZ2005/000203 -11 advance. An actuating current lactuate is calculated to give an even actuation until the position sensor indicates the solenoid 13 is fully actuated. The current is then reduced to a holding current I hold calculated as the minimal current required to hold the solenoid 13 actuated within specified operating conditions. 5 The position sensor 312 for the solenoid in the preferred embodiment is an optical sensor although one skilled in the art will appreciate that other forms of position sensor could be applicable, this sensor may either only sense whether the internal core 315, 15 is fully retracted (eg by breaking of a light beam), or may sense the exact position of the internal core, by for example means of a 10 series of sensors arrayed down the path of travel the of the internal core's 315, 15 travel. Alternatively the position of the internal core 15, 315 can be inferred by current feedback. Turning to Figures 6 and 7 there can be seen a building 18 with a series of doors 20 installed having electrically actuated locks 1 in accordance with the 15 present invention. The nominal operating voltage for example in a typical prior art installation would be 12 volts for the solenoid. However as can be seen in Figure 7 there is a gradual drop in the voltage over the voltage supplied over the series of doors 20 due to the resistance of the wiring and also the resistance of the cross of the lock 1 of each door 20. Thus whilst a 12 volt nominal operating 20 voltage would be required in a prior art installation in actuality 14 volts must initially be supplied so that there is a sufficient voltage present over the series of doors 20. If the sensitivity of the solenoid is inside of 12 volts plus or minus 2 volts (as is sometimes the case) then the first two doors 20 (from the left) will receive operating voltage higher than that required and thus the solenoid will 25 produce excessive force on both itself and the lock 1 internal parts, the third door 20 from the left will be the only door 20 in the series to receive the nominal operating 12 volt voltage, and the last two doors 20 will receive lower than 12 volts with the last door 20 receiving somewhere in the vicinity of 10 volts. Therefore these last two doors 20 may not receive sufficient voltage to actuate 30 the lock 1 with the correct force. However in the present invention the nominal WO 2006/016822 PCT/NZ2005/000203 -12 operating voltage is preferably in the vicinity of 8 volts of the solenoid. Thus even if the voltage profile over the doors 20 exists as in figure 7 due to the current control nature of the present invention the solenoid will still receive an operating voltage of 8 volts. Thus the required force will always be present 5 regardless of the location of the lock in a series of doors 20. Whilst in the present invention operating voltages of 12 to 24 volts have been mentioned and that the solenoid of the present invention operates at 8 volts it is of course to be envisaged that any operating voltage above the nominal operating voltage of the solenoid or electrically drive means of the present 10 invention could be employed. It is merely a relative values of the operating voltage and the electrical drive means operating voltage together with the current control means of the present invention which is important. Each of the doors 20 is supplied by cabling from a power supply 21. The foregoing description of the invention includes preferred forms 15 thereof. Modifications may be made thereto without departing from the scope of the invention as defined by the accompanying claims.

Claims (31)

1. An actuator for a lock comprising: a movable element, drive means electrically energisable by a power supply to actuate said 5 movable element between a first position and a second position, and a current controller to control the current supplied to said drive means, the controller having at least two current supply modes, a first current supply mode (actuating current) to actuate the movable element via said drive 10 means from the first position to the second position and a second current supply mode (holding current) to hold said moveable element via said drive means in the second position, wherein the current supplied in the second mode is lower than the current supplied in said first mode.

2. An actuator as claimed in claim 1 further comprising a current sensing 15 means arranged to sense the current supplied to said drive means.

3. An actuator as claimed in claim 2 wherein the current controller is arranged to control said current supplied to said drive means in response to the current sensed by said current sensing means.

4. A lock assembly that is electrically actuable by a drive means that 20 operates at a voltage below the nominal line voltage of power supplied to said lock assembly, and controlling the actuation of said drive means by control of the current being made available to said drive means, said drive means directly or indirectly controlling the locking and unlocking of said lock assembly. 25

5. A lock assembly as claimed in claim 4 wherein said drive means is a solenoid.

6. A lock assembly as claimed in either claim 4 or 5 wherein said solenoid has a power off fail secure condition or a power off failsafe condition.

7. A lock assembly as claimed in claim 6 wherein either said fail safe or fail 30 secure condition is under the action of a bias such as a spring. WO 2006/016822 PCT/NZ2005/000203 -14

8. A lock assembly as claimed in any one of claims 4 to 7 wherein said solenoid is an 8 volt rated solenoid which via current control can operate on a 12 to 24 volt direct current supply voltage.

9. A lock assembly as claimed in any one of claims 4 to 8 wherein said 5 solenoid is an 8 volt rated solenoid which via current control can operate on a 12 or 24 volt direct current supply voltage.

10. A lock assembly as claimed in any one of claims 4 to 9 wherein said current is adjusted to maintain a constant force output from said solenoid.

11. A lock assembly as claimed in any one of claims 4 to 10 wherein said 10 current is adjusted in relation to the stroke position of said solenoid to maintain a constant force output.

12. A lock assembly as claimed in claim 11 wherein said stroke position is monitored.

13. A lock assembly as claimed in claim 11 wherein said force is varied to 15 conform to a pre chosen force displacement profile and said current is adjusted accordingly to produce said force-displacement profile.

14. A lock assembly as claimed in either claim 12 or 13 wherein said stroke position of the solenoid is monitored by a position feedback sensor.

15. A method of control of an electrical drive means for a lock assembly 20 wherein actuation of the drive means is controlled by varying the current to the drive means.

16. A method of control as claimed in claim 15 wherein said electrical drive means is a solenoid.

17. A method of control as claimed in either claim 15 or 16 wherein said 25 solenoid has a power off fail secure condition (e.g. under the action of a bias such as a spring) or a power off failsafe condition (e.g. under the action of a bias such as a spring).

18. A method of control as claimed in any one of claims 15 to 17 wherein said solenoid is an 8 volt rated solenoid which via current control can 30 operate on a 12 to 24 volt direct current supply voltage. WO 2006/016822 PCT/NZ2005/000203 - 15

19. A method of control as claimed in any one of claims 15 to 18 wherein said solenoid is an 8 volt rated solenoid which via current control can operate on a 12 or 24 volt direct current supply voltage.

20. A method of control as claimed in any one of claims 15 to 19 wherein 5 said current is adjusted to maintain a constant force output from said solenoid.

21. A method of control as claimed in any one of claims 15 to 19 wherein said current is adjusted in relation to the stroke position of said solenoid to maintain a constant force output. 10

22. A method of control as claimed in any one of claims 15 to 21 wherein said stroke position is monitored.

23. A method of control as claimed in claim 22 wherein said stroke position of said solenoid is monitored by a combination optical and mechanical system where by when the plunger of said solenoid is fully retracted in, a 15 mechanical arm breaks an optical sensor beam.

24. A method of control as claimed in any one of claims 15 to 22 wherein said force is varied to conform to a pre chosen force displacement profile and said current is adjusted accordingly to produce said force-displacement profile. 20

25. A method of control as herein described with reference to one or more of the accompanying drawings.

26. A lock assembly as herein described with reference to one or more of the accompanying drawings.

27. A door with a lock assembly, as herein described, fitted, with reference 25 to any one or more of the accompanying drawings.

28. A building with a lock assembly as herein described, fitted, with reference to any one or more of the accompanying drawings

29. A lock including an actuator as claimed in claim 1.

30. A building including a door with a lock as claimed in claim 29. WO 2006/016822 PCT/NZ2005/000203 -16

31. A plurality of locks as claimed in claim 29 wherein the locks have a common power supply supplying electricity to each lock in series.