WO1999060235A2

WO1999060235A2 - Electrically controlled lock employing shape memory alloy

Info

Publication number: WO1999060235A2
Application number: PCT/US1999/010891
Authority: WO
Inventors: Dirk L. Bellamy
Original assignee: Slc Technologies, Inc.
Priority date: 1998-05-18
Filing date: 1999-05-17
Publication date: 1999-11-25
Also published as: AU3999099A; WO1999060235A3

Abstract

A lock changes between locked and unlocked states in response to changing the temperature of a shape metal alloy element (7) within the lock. In one embodiment, the alloy element is in the shape of a wire and is heated by passing an electrical current therethrough. In response, the wire contracts. This contractive movement is arranged to compress a spring (10), thereby intercoupling a normally free-spinning actuator knob (6) with an internal unlocking element, permitting a user to then turn the knob to unlock the lock. The shape memory alloy enables electronic actuation of locks without reliance on solenoids or motors, permitting very small electronic locks (e.g., cylinder locks sized to fit within three-quarters inch holes).

Description

ELECTRICALLY CONTROLLED LOCK EMPLOYING SHAPE MEMORY ALLOY

Field of the Invention The present application relates to electrically controlled locks, and more particularly relates to locks employing shape memory alloys.

Background and Summary of the Invention Shape memory alloys are compounds whose size contracts with increasing temperatures. An exemplary shape memory alloy is formed of nickel and titanium and is commonly known as nitinol.

U.S. Patent 5,868,013 (published after the present application's priority date) shows a lock that uses nitinol for various purposes, many of which rely on the metallurgical hardness of the alloy (e.g., to resist attacks with bolt cutters). The patent also discloses a nitinol lock actuator that is heated by a nearby heater element to controllably lock or unlock the lock. However, the arrangement shown in the patent suffers from various drawbacks.

In accordance with one aspect of the present invention, a shape memory alloy is employed in wire form as an actuator for a lock. The use of alloy wire avoids the need for a distinct heater element (thereby reducing cost and complexity), since the wire can be heated simply by passing an electrical current directly therethrough. Moreover, the relatively small thermal mass of the wire allows it to heat and cool quickly, providing faster state changes. Still further, the high surface-area-to-volume ratio of wire provides quick cooling when electrical current is removed from the wire, still further speeding lock operation.

In accordance with another aspect of the invention a shape memory alloy wire is configured in a non-linear form (e.g., bent-back on itself), to yield relatively more heat-induced movement within fixed space constraints.

In accordance with yet another embodiment of the invention, a manually- operated member is controllably coupled to an unlocking mechanism through a linkage mechanism, where the linkage mechanism is engaged or disengaged by action of a shape memory alloy. In one particular form of such embodiment, the manually- operated member is a normally free-spinning spinner knob that is controllably linked to the unlocking mechanism through a clutch assembly that uses a shape memory alloy. Only when the alloy is heated does the spinner knob become coupled to the unlocking mechanism, permitting the lock to be opened.

In accordance with still another embodiment, the invention is an electrically controlled lock that can fit in an opening for a standard cylinder lock (i.e. 0.75 inches in diameter), yet employs neither a solenoid nor an electric motor.

The foregoing and additional features and advantages of the preferred embodiment of the present invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.

Brief Description of the Drawings Fig. 1 is an exploded view of a lock according to one embodiment of the present invention.

Fig. 2 is a view of the lock of Fig. 1, assembled. Fig. 3 is an end view of the lock of Fig. 2.

Fig. 4 is a section view, taken on line 4-4 of Fig. 2, showing the illustrative lock in its locked state (i.e., with the main clutch spring in its latched, unactuated state).

Fig. 5 is a section view, taken on line 5-5 of Fig. 2, showing the lock as it is starting to close (after it has been opened and then unpowered), wherein the main spring is captured beneath the clutch cap.

Fig. 6 is a view of the lock in the Fig. 4 state, but showing the view on section 5-5.

Fig. 7 is section view, taken on line 7-7 of Fig. 2, showing the illustrative lock in its locked state (i.e., the same state as Fig. 4).

Fig. 8 is a section view, like Fig. 7, but showing the lock in its activated state (i.e. the clutch is rotated so that the balls can rise up out of the body member, and the spring is activated to engage the spinner knob). Fig. 9 is a section view, like Fig. 7, but showing the lock in its fully open state (i.e., the body forces the balls to reside in the output member and the clutch).

Fig. 10 is a section view like Fig. 7, but showing the lock as it is starting to close (i.e., the same state as Fig. 5). Fig. 11 is a section view like Fig. 7, but showing the lock when it is closed but not locked (i.e., the mechanism is rotated to have the balls align with the channels in the body member, and the cam stop has encountered the body).

Fig. 12 is a section view like Fig. 7, showing the lock returned to its fully locked and closed position. Figs. 13-15 are views of a main body of the lock of Fig. 2.

Fig. 16 shows an output member of the lock of Fig. 2.

Figs. 17-18 are views of a clutch member of the lock of Fig. 2.

Figs. 19-20 are views of a clutch cap used in the lock of Fig. 2.

Detailed Description

The present specification illustrates the principles of the invention with reference to an illustrative example, namely an electronic cylinder lock. However, it should be noted that the principles of the invention are not so limited, but can be employed in connection with essentially any form of electronic lock. Referring to the figures, item 2 is the main body of the cylinder lock. This body maintains a standard "double-D" profile (i.e. 0.75 inch diameter, with 0.625 inch at the flats) so the illustrated lock can retrofit into existing cabinets. It contains a feature to mate with the locking balls 1 (or bars) to secure the output member 8 to the body in the lock's locked state. Body 2 is a cylinder with the a front opening for the input knob 6 to protrude through, and a rear opening for the output member 8 to extend through. A retaining ring (not shown) is used to hold the lock mechanism inside the body. Threads (not shown) on the outside of body 2 cooperate with a threaded fastener to mount the lock behind a panel.

The input knob 6 serves to transmit user-applied manual torque to the rest of the mechanism. Knob 6 resides at the very front of the lock mechanism. It contains features to capture the clutch mechanism 5 after it is actuated. Knob 6 is free spinning (to prevent vandalism) until the lock is activated.

The main clutch spring is shown by numeral 10 and includes two spring ends 10a. These legs 10a of the main clutch spring move toward the left in Fig. 1 upon actuation and are captured by the input knob 6 as the user turns the knob. Spring 10 is a double torsion spring.

The clutch cap 9 is fixed with relation to the output member 8. The purpose of the clutch cap is to fix the clutch spring legs 10a in place when the lock is locked, and to capture the legs in their actuated state once the clutch has begun rotation. Ears 25 on the clutch cap 9 engage corresponding notches 26 in the body member 8. The actuator 7 is a 2.5 inch length of shape memory alloy wire doubled back on itself (i.e. 1.25 inch length). This wire contracts when heated. When the lock is activated, the wire contracts and pulls the main clutch spring 10 so its legs are captured by the input knob 6. In the presently preferred embodiment, the shape memory alloy wire is a variety marketed under the Flexinol trademark by Dynalloy, Inc. The wire is .004 inches in diameter, has a transition temperature of 90° Celsius, and exhibits a contraction of between 5 and 8% between its martinsite and austenite phases.

In the illustrated embodiment, the wire is activated by controllably passing a current of 200 milliamperes therethrough. The switching circuitry to apply this current to the actuator wire is not shown, but can be of conventional design (e.g. a relay or semiconductor switching circuit). The switching circuitry is activated in response to an unlock signal generated by a lock controller (which may be of the touchpad-, magnetic stripe-, electronic key-, biometric-, etc. -type). In an exemplary embodiment, the lock forms part of a security system like that sold by the present assignee under the TRACcess trademark and described, e.g., in U.S. patents 5,550,529, 5,705,991, 5,475,375, 5,280,518, 5,046,04, 4,800,255, 4,851,652, 4,864,115, and 4,967,305, and in copending applications 08/748,194 (allowed), 08/846,040, 08/746,322, and 09/067,353, the disclosures of which are incorporated by reference. Clutch 5 is the part of the assembly which retains the main clutch spring 10. When the input knob 6 captures the clutch spring 10, clutch 5 is driven by input knob 6. The primary purpose of clutch 5 is to hold the locking balls 1 (or bars in alternative embodiments) out so they can interact with a groove 11 defined in the main body 2. When the clutch 5 begins to sweep around under user manipulation, features 12 in the clutch become oriented such that the locking balls 1 are allowed to rise up out of the track 11 in the body and reside fully in a hole 13 in the output member and in the clutch.

The output member 8 is attached directly to the cam 3. The output is the member which locks to the body 2 via the locking balls 1. When user input is transmitted to the clutch 5 and the clutch sweeps around, allowing the balls 1 to rise out of the body features 11, the user input is transmitted to the output member by the clutch. Now the output is allowed to turn until it reaches its fully open state. This is when a cam stop 4 encounters a stop tab 14 on the body. The cam stop 4 allows the lock to be opened to a user specified point

(typically 90 or 180 degrees). The cam stop 4 encounters the stop tab on the body in the lock's fully locked state and in the lock's fully open state. The lock will operate either clockwise or counter-clockwise.

The cam 3 is the member which, in the end, is moved by the user. It is what secures a drawer or door in its closed and locked state in known fashion.

Initially the lock is in a stable, locked state. Locking balls 1 internally lock the output member 8 to the body 2. These are held in place by scallop features 12 on the clutch. The input knob 6 is free-spinning until the lock is activated.

Upon activation, the shape memory alloy wire actuator moves the clutch spring 10 so that the legs 10a thereof can interact with the input knob 6. Then, as the knob turns, features 16 on the knob contact the spring legs and thus move the clutch. The clutch 5 then sweeps through some small arc until some features 18 contact mating features 19 on the output member. When the clutch has contacted the output member, the legs of the main clutch spring are captured between the clutch cap so they remain in the activated state. At this point the clutch is turned such that the locking balls 1 can ramp up out of the body as the lock rotation continues. Now, the entire mechanism is rotated by the user until the cam stop 4 (attached to the output member) contacts a feature in the body 2. The user can leave the lock in its open state for whatever period of time is desired. The legs 10a are captured between features 21 in the clutch cap (instead of being in feature 20 when not activated) and are therefore ready for the user to turn the mechanism back to its stable locked position.

When the user begins to rotate the lock from its fully open position, the parts interact somewhat differently. The input knob 6 sweeps around, as before, and captures the clutch spring legs 10a. However, now the balls have locked the clutch in place with respect to the output. Therefore, the user transmits torque to the input, then to the clutch legs, then to the clutch, then to the balls, then finally to the output member.

When the mechanism sweeps around fully to its locked location, the cam stop 4 prevents the output member 8 from rotating further. The clutch then continues to rotate, forcing the balls 1 back into their stable, locked positions. At this point, the clutch continues its path until the clutch spring legs 10a once again line up with features 20 in the clutch cap and the legs are allowed to leave their actuated state. Now the mechanism is fully locked, and the input is again free- spinning.

The shape memory allow actuator wire is looped over the crossed legs 10a of spring 10. The other end of the wire is fixed to an end 15 of clutch 5. When the wire contracts, it pulls on this spring, compressing the legs toward the clutch. So doing engages the spring ends 10a with drive dogs 16 in the knob, coupling the knob to the clutch.

As shown in Fig. 7, there is about 30° lost motion 17 in which the scallop 12 is positioned under ball 1 to provide clearance for the ball to move in.

Various countermeasures can be included to prevent defeat of the lock by externally applied heat. For example, if a thief uses a torch to heat the front face of the lock, with the expectation that the shape memory alloy wire 7 will contract and the lock will open, such attack can be defeated by employing (typically nearer the front of the lock) a second shape memory alloy (e.g. wire) or bi-metallic member which — when it changes configuration with heat — prevents the lock from opening. This preventive action can be effected by moving (or permitting spring biased movement of) locking features from the interior of the lock into the body member 2, preventing rotation of the lock internals (i.e. independently keying the lock internals from rotation), or by interfering with the coupling of components between the input knob 6 and the locking cam 3 (e.g. by preventing the clutch from engaging), or by counteracting the compressive force applied by wire 7 to the legs 10a of spring 10. Other techniques can rely on a heat sink to dissipate frontally-applied heat, or a heat- activated switch to trigger an alarm, or to power a backup-lock or a miniature electronic cooling unit. etc. Many such techniques will be apparent to the reader based on the foregoing.

Having described the principles of my invention with reference to a preferred embodiment, it should be apparent that the invention can be modified in arrangement and detail without departing from such principles. For example, shape metal alloy forms other than wires can be employed. Similarly, if wire is used, it need not be straight but can be serpentined, etc., to increase its length change.

Although the preferred embodiment has been described as including certain combinations of features, my invention includes alternative embodiments that include other combinations of the features disclosed herein and in the documents incorporated by reference.

More generally, it will be recognized that the use of shape memory alloy as an actuator element in a lock opens up myriad possible implementations ~ many radically different than the illustrative embodiment discussed above — but all sharing the common operational principle of changing the state of a lock in response to temperature. Cam locks, cabinet locks, rim locks, plug locks, cylinder locks, and all manner of latches are examples of some of the diverse forms of lock to which the present technology may be applied.

Accordingly, it should be recognized that the foregoing embodiments are illustrative only and should not be taken as limiting the scope of the invention. Rather. I claim as my invention all such modifications as may come within the scope and spirit of the following claims and equivalents thereto.

Claims

I CLAIM:

1. A lock having first and second states, one of said states being locked and the other of said states being unlocked, characterized in that the lock includes a shape memory alloy whose shape changes with temperature, wherein the lock is in the first state at a relatively cooler temperature, and the lock is in the second state at a relatively warmer temperature.

2. The lock of claim 1 wherein the lock is in the first state at an ambient temperature, and is in the second state when the shape memory alloy is heated above a transition temperature.

3. The lock of claim 1 including an electrical heating element to controllably change the temperature of the shape metal alloy, and thereby to controllably change the state of the lock between the first and second states.

4. The lock of claim 3 in which the electrical heating element comprises the shape memory alloy, wherein at least a portion of the shape memory alloy is in wire form.

5. The lock of claim 1 in which the second state is the unlocked state.

6. The lock of claim 1 further including a manually-movable input member and an unlocking member, wherein the shape memory alloy is configured to controllably couple or uncouple the manually-movable input member to the locking member.

7. The lock of claim 6 further including a clutch assembly to controllably link the manually-movable input member to the unlocking member, wherein the clutch assembly includes the shape memory alloy.

8. The lock of claim 1 wherein the shape memory alloy includes at least a portion in the form of a wire, and the wire is disposed within the lock to controllably change the tension in a spring.

9. The lock of claim 8 wherein the shape memory alloy wire serves to compress the spring in response to an electrical current passing through the wire.

10. The lock of claim 1, further comprising means for preventing unlocking of the lock in response to heat externally applied to a face of the lock

11. The lock of claim 1 wherein the shape memory alloy comprises nitinol.

12. The lock of claim 1 wherein the shape memory alloy exhibits a contraction of between 5% and 8% between its martinsite and austenite phases.

13. A lock having a generally cylindrical body sized to fit in a hole having a diameter of one inch or less, and having a shape memory alloy therein.