US2197802A - Electromagnetic lock - Google Patents

Description

J. P. JAMES April 23, 1940.

ELECTROMAGNETIC LOCK Filed Aug. 9, 1938 5 Sheets-Sheet l April 23, 1940.

J. P. JAMES ELECTROMAGNETIC LOCK Filed Aug. 9, 1938 5 Sheets-Sheet 2 April 23, 1940. JAM 2.197.802

- ELECTROMAGNETIC LOCK Filed Aug. 9 1938 Q 5 Sheets-Sheet 3 April 23, 1940. J. P. JAMES 2,197,802

ELECTROMAGNETIC LOCK Filed Aug. 9, 1938 5 Sheets-Sheet 4 April 23, 1940.

J. P. JAMES 2,197,802 ELECTROMAGNETIC LOCK 5 Sheets-Sheet 5 Filed Aug. 9, 1938 IIIIIIIIIIIIIIIIIIIIIIII/J Patented Apr. 23, 1940 UNITED STATES PATENT OFFICE ELECTROMAGNETIC LOCK Jackfaterson James, Liverpool, England Application August 9, 1938, Serial No. 223,988 In Great Britain September 13, 1937 Claims.

The present invention relates to electromagnetic locks which-are releasedbythe energisation of a number of solenoids under the control of three or more manually operated switches or switch contacts and the invention is particularly suitable for use in connection with automobile vehicles for preventing'theitthereof.

The invention may/ be used for the locking of any desired element of apparatus and in connection-with automobile vehicles it may, for example, be used to lock thegear lever when the automobile is parked in a public space, in which case the locking member may consist of a slidable plate orbar which is forked so that in its released position it permits free manipulation of the gear solenoid and in the circuit of another to render the solenoids operable in predetermined sequence only to release the lock, a trip coil adapted when energised to render at least one of said solenoids inoperative to prevent release ofthe lock and so connected with "at least two of I said manually operatedswitches thatclosure of either of saidtwo manually operated switches prior to closure of the automatic switch in the circuit of the solenoid controlled by such manually operated switch would cause energisation of the trip coil.

It is 'a further object of the invention to embody in such an electrically releasable lockat least one additional switch, similar in appearance to such manually operated switches and connected to the trip coil so as to energise the. trip coll on closure of such additionalswitch.

More particularly, a lock is released by the energisation of at least three solenoids in predetermined sequence under the control of at least three manually operated switches, one in :the circuit of each solenoid, energisation of a .given one solenoid being adapted to cause closure of a break in the circuit of another solenoid, energisationof which, in turn, .isadapted to cause closure of a break in the circuit oi a third solenoid,-while at least the first solenoid is adapted to be rendered inoperative bythe-energisation of -a trip cell which is connected for energisationthereoi, with the manually operated switchesof said secand and third solenoids through contactswhich s are respectively opened on energisation of said first and second solenoids.

Preferably at leastone of said solenoidsior example, the first,has a break in its circuit which is normally closed but is adapted to be opened 110 by energisation of a trip coil. To render therelease of the lock more diillcult to an unauthorised person the trip coil. may be connected, for energisation thereof, with an additional manually operated switch or switches indistinguishable 5 from said first mentioned manually operated switches.

Operation ofsaid additional switch or any of said additional switches or of any ofsaid manually operated switches otherthanthe first in other than the predeterminedsequence may be adapted a to cause energisation of the trip coil and closure of a switch controllingan audible or visible alarm device. I

If desired threesolenoidsmay be-arranged in cascade. Preferably, the'armatures of the first two solenoids energised in correct sequence :are each adapted respectively toclose a break-in the circuit of the coil immediately succeeding and also to close a break'inza hold-on circuit adapted for maintaining energisation of its own coil, the hold-on circuits of both of said coils including a switch or switches which can be opened by opera- I tion of said trip coil.

The said manually operated'switches and said additional manually operatedswitch or switches may be embodied in a multipleswitch capable of selective operation at predetermined positions for manual closure of breaks in the circuits of the respective coils or solenoids andcapable of .operation at other positions for 'energisation of the trip coil, whereby the lock can be released. by selective operation of said multiple switch. at predetermined positions in correct order, while operation of said switch at other positions than said predetermined positions or at said predetermined positions in incorrect orderaszdescribed above with reference to saidmanually operated switches, is adapted to cause operation'of' said trip coil and of said alarm device.

The invention is more particularly described with reference to the accompanying drawings which illustrate examples of the invention suitable for use in connection with an automobile vehicle and in which:

Figure l is a wiring diagram showing one form of electric circuit according to the invention, in which the lock can only be released by operation of the manually operated switches in predetermined sequence.

Figure 2 is a wiring diagram of an alternative electric circuit.

Figure 3 illustrates the main switch governing the current supply.

Figure 4 illustrates a switch governing the current supply to the alarm circuit.

Figures 5 and 6 are a sectional elevation and plan view of a manual multiple switch control.

Figure '7 is a side sectional view of the locking unit.

Figure 8 is a corresponding end sectional view on the line 3-8 of Figure 7.

Figure 9 is a sectional plan view on the line S-9 of Figure 7.

Figure 10 is a side sectional elevation being a modified arrangement for the control of the locking members as compared with that shown in Figure 7.

The mechanical part of the lock referred to generally as A shown in Figures 5, 8 or 9 has a main locking member 28 in the form or" a fiat plate, the main body 25a of which is freely shdable into guides ll, 22 formed in the sides 23, 24 of an inner casing, composed of the said side plates 23, and two end plates 25, 2G, and these plates are secured together by the housing 28 and base plate 25, the base plate being preferably welded to the housing 28, as indicated at 2911.

The locking unit A may be secured to the automobile vehicle by bolts 35 in such a position in relation to the gear lever 35 as to secure this lever in a given locked position usually the neutral position when the locking member 23 is in its projected or locked position when the V notch 232) of the locking member 23 is brought closely adjacent to or in contact with the said gear lever 3| as shown in Figure 9.

Referring to Figures '7 and 8 of the drawings, a spring actuated cross bar 32 is slidably mounted in vertical guides 33, 34 in the side plates 23, 4 and is adapted to abut against one end 29c of the locking member 25 to secure the gear lever 35 in the neutral position.

The bar 32 is secured to one end of the armature 48 of a solenoid il so that when the authorised user desires to unlock the gear lever 3i this may be done by the correct operation of the electrical switch means (to be hereinafter described) to cause the magnetic coll M to be energised and thereby to withdraw the armature 40 and the locking bar 32 connected therewith against the action of the spring M2, from contact with the locking member 2 4 to allow this to travel down its guide 2!, 22 by means of a spring H to release the gear lever 3i. Thus the locking member 20 is withdrawn from its projected position by means of the spring and may, if desired, be substantially horizontally disposed instead ill-- clined as shown in Figure '7. Alternatively the locking bar 23 may be adapted to be withdrawn by the armature of an electromagnetic coil, energised simultaneously with the solenoid 4!.

In the alternative form of construction shown in Figure 10 the locking member 2?] is locked in its projected position by means of a spring actuated lever 3'1 which is pivoted at 38 to the side plates of the inner casing and which has an upstanding projection 39 adapted to abut against the end 260 of the locking member 22 whereby to prevent movement of the gear lever from the neutral position.

The free end of the lever 31 is connected to one end of the armature 40 of a solenoid 4|. The lever 3'! is normally urged in an upward direction by means of a spring I42.

The electromagnetic coil or solenoid 4| and its armature 40 are diagrammatically shown in Figure 1 which illustrates one form of electromagnetic lock releasing circuit according to the invention. The energisation of the coil M is dependent upon the previous energisation of coils 42, 43 in correct order i. e. coil 42 first and coil 43 second. The coils 42, 43 and 4| are respectively in circuit with manually operable switches or switch contacts 52, 53 and 5|. If the switches 52, 53 and 5| are closed in the sequence 52, 53, 5i then the coils 42, 43 and 4| will be energised in correct sequence to release the lock. If the switches 53, 5i are operated in incorrect se quence then a coil 44 will be energised to operate an alarm and a trip coil 45 will be energised as will be described later.

In order to make it difficult for an unauthorised used to select the correct switches for operation, more manually operated switches are provided than are required for releasing the look.

In Figure 1 a switch 54 is shown as indicating either one or a number of additional switches arranged in parallel all of which are unnecessary for the correct operation of the lock.

The apparatus of the invention is operated by an electric accumulator which may be the ordinary accumulator of an automobile vehicle and it is also operable by an auxiliary accumulator 6| which may be concealed. The provision of a concealed auxiliary accumulator is not of course essential but is advisable since it would enable the warning device to be operated even though the ordinary accumulator were disconnected by an unauthorised person attempting to tamper with the lock.

Current is fed to the electrical apparatus of the invention through a switch 63 which is normally open, and closed only when the locking member 20 is in its projected position. This switch is shown in more detail in Figure 3 wherein the locking member 20 is in its withdrawn or unlocked position. When the locking member is moved towards the left into its projected position the switch lever 64 is angularly displaced in an anticlockwise direction under the influence of a spring 65, operating through an arm 66 rigidly connected to the lever 64, whereby the terminals 6'! are brought into contact with the terminals 68 which feed the circuit. A similar switch 69 controls the supply of current to an alarm device 10 shown in Figure 1. The switch 69 is shown in more detail in Figure 4 and normally remains open when the locking member 20 is withdrawn to unlocked position. When the locking member 20 is projected the switch 59 is available for closure but is not actually closed until the coil 44 is energised to cause a downward movement of the armature 10a as viewed in Figure 4 and angular displacement of the switch lever in an anticlockwise direction. The switch levers of the switches 63 and 69 are provided respectively with insulating sheaths 63a, 69a where they contact with the locking member 20.

Assuming that the locking member 20 is in its projected position, thereby allowing switch as shown in Figure 3 to close the correct operation of the switch gear shown in Figure l is as follows:

' The switch- 52 is first otallclosedand the circuit of the coil 42 is completed from the return ""II through the conductor I2, switch 52, conductor- 52a, contact 13a, armature head I3, contact "13b and conductor 14. The energisation of the coil 42 moves armature head I6 down to close contactpair IT and contact pair I8 whereupon the manual switch 52 can be released-and the return circuit of the coil 42 is maintained through conductor I4, contact 13b, armature head 13, contact 13a, conductor I9, contact pair I8 and conductors 90 and 12 to the return ll. The closure of contact pair I1 prepares thecircuit of coil 43 for energisation by closure of the switch53, whereupon the circuitof'coil 43 is completed from the return -'I| through a conductor I2, switch 53, conductor 53a contact pairs 11 andthe conductors 8| and 82. The armature head 03 of coil 43 then moves down to close contactpairs 84 and 85, whereupon the switch 53 can be released and the return circuit of coil 43 is maintained through conductors '82 and 02a, contact pair 95, conductor 8'5, contact pair 18 and conductors and 12 to return I I.

The closure of contact pair 84 prepares the circuit of'coil 4| for energisation by closure of switch whereby the circuit of coil 4| is completed from TI through conductor I2, switch 5|, conductor fl, contact pair 84 and conductor 88 It will be appreciated that there is a potentialcurrent supply to all the coils shown in Fig ure 1 when the switch 63 is closed, this current supply takingplace through conductors shown in dotted lines. It will be appreciated that in order to release the lock, the switches 52, "53, 5| must be operated in the order 52, 53, 5| andv if for example, theswitch 5| had been closed immediately after energisation' of the coil 42, the coil 42 would have been'de-energised by energisation of the trip coil 45, through conductors 90, 9| and 92, contacts 93 and the'top contact 84, conductor 81, switch 5|, conductor I2 and return II, causing movement of the armature head I3 downwards to disconnect the contacts 13a and 13b which are normally bridged by the armature head 13 thereby breaking the hold-on return circuit of the coil 42. Moreover such closure of switch 5| would also have formeda return for the coil 44 through conductor 81 the contact pairs 93, conductors 92, 9I and 9Ia, thereby closing the switch 99 and putting the alarm device I0 into operation which may of course be either optical or audible or both.

If the switch 5| 'were closed prior to closure of the switch 52, the alarm device would be put into operation, and the trip coil 45 energised but of course the energisation of the trip coil would be of no efiect' if no other coil had been previously energised.

. Again, if the switch 53 were closed prior to closure of switch 52 and energisation of coil 42,

the coil 45 would be energised through conducprior to release of the lock and prior to opening of the switch 53 the coil 44 would be energised through conductors 9Ia, 9| switch 54, conducitor 12 to return 'll andmoreover ifithecoil 42 bridged by armature head I6, conductor or the coils 42 and" had been previously encrgised they would be de energised by energisation of the trip coi1 45 and movement of the armature" downwards, since the return of coils 44 and 45 are permanently interconnected through conductors 9Ia,9|,and 90. Thus, with the switch '63 closed operation of -the switch 53 prior to operation of the switch 52 or operation of the switch 5| prior to operation of switches 52, 53 in the order 52, 53, or operation. of the switch or switches 54 at any time, would cause energisation of the coil 44 and operation'ot the warning device and moreover any such incorrect operation would cause energisationof the coil and de-energisation of the coil 42' Mei the'colls 42 and 43 if previously energised by successful operation of the switch 52 or ofthe switches 52 and 53.

The upper contact 11 is electrically connected with the lower contact 11a and bothare insulatedly mounted on the armature head I6. Similarly the upper contact 84 is connected with the lower contact 93 and both are insulatedly mounted on the armature head83. Thecontacts 13a, 13b are'notimounted upon the armature'head I3 but contact with and are bridged bythe head 13 when the head is inits normal projected position shown in Figure 1.

Figure 2 illustrates a different arrangement ofthe coils 4I, 42, 43, 44 and 45 which'enables the results achieved by the arrangement of Figure 1 to be obtained but necessitates the provision of three additional coils 99; 99 and I90. The elements of Figure 2 which correspond'to elements of Figure l are similarly referenced.

The correct operation of the apparatus of Figure 2 is as follows:

The switch 52 is first of all closed to energise the coil 42 and the return from coil 42 takes place first of all through conductors-I00, |0I- contacts I9| and armature head I92 and switch 52 to return 'II, whereupon the armature head I6 bridges the contacts I02 so that the switch 52 can be released the return being established through conductors I90, I03, contacts I02 I04, contacts "95 bridged by trip coil armature head I3 and through conductor I05, to return'll.

The'energisationof coil 42and thebridging of contacts I02 closes one break in the circuits of '98. The energisation of 'coils' 43 and 99 is dependent upon prior energisation of coil 42 and of coil 98, the armature head I06 of which bridges contacts I0I to provide return for coils 99 and 43 through conductors 101a, I0"), I08

contacts I01 bridged by armature head I06, conductors I09, IIO, I03, contacts I02 bridged by armature head 16, conductor I04, contacts '95 bridged by armature head 13 and conductor 105 to return II. As soon as armature head 930i coil 43 is closed the switch 53 can be released,

the returnfor coils99 and 43 being then established through conductors I0Ia, I0Ib, II2 armature head 83, conductors H3, I I0, I03, armature'head I5, conductor I04, armature head I3 and conductor I05, to return II. As soon as switch 53 is released the armature head I05 of coil 99 will move out of contact with contacts I0'I, the hold-on circuits of coils 43 and 99 be- 'ing now completed independently of armature head I06. a The coil 4| 'is 'now prepared 'for energlsation and can be energised by depression of switch 5I which establishes a return circuit for coil 4I through conductor II4, contacts IIIa, bridged by armature head III, conductor H5 and switch 5I to return II.

Similarly as in Figure 1, if any of the switches 54 is depressed or if either of the switches 53, 5| is depressed in incorrect sequence, the coil 44 will be immediately energised to close the alarm supply switch 69 and moreover the trip coil 45 will be energised to break any return hold-on circuit which may have been previously established and maintained through bridging of the contacts 95 by armature head I3. Thus if the coil 42 or the coils 42, 43 and 99 had been previously energized they would immediately be de-energised.

As will be observed the return ends of coils 44 and 45 are connected by conductors I20, I2I and I22 which conductors are connectable to the return 'II either directly through switch 54 or through switch 5I ii coils 43 and 99 have not been energised, or through switch 53 if coil 42 has not been energised.

In connection with both Figure l and Figure 2 the returns 'II in the case of a two pole wiring system would be constituted by or connected to a common bus bar which would be connected through the manual control of the present invention, with that pole of the accumulator, whether positive or negative, opposite to that connected to the switch 63. In the case of single pole wiring systems the returns II would be constituted by or connected through the control to the metallic casing or framework of the apparatus of the vehicle in which it is installed, such casing or framework being connected to that pole of the accumulator opposite to that connected to the switch 63.

In both Figures 1 and 2 the switches 5|, 52, 53, 54 are understood to be spring-loaded so as normally to remain open. The armatures of coils 42, 43, 45, 98, 99 and I are spring-loaded so as remain in a projected position.

The locking bar 32 connected to armature 40 of coil M is spring loaded so as normally to maintain armature 40 in its projected position. The armature 10a of coil 44 is counterbalanced by the lever of switch 69 so as normally to keep the armature 10a in its projected position. When energisation takes place the movable blades of switch 69 engage the fixed spring blades thereof, the interengagement of such blades preventing return of the armature 10a to its projected position until the locking member 20 is withdrawn.

It will be appreciated that for the successful operation of the apparatus of the present invention to release the lock three switches 5|, 52, 53 only are necessary but in order to make it more difiicult for an unauthorized person to release the lock a large number of similar switches are preferably provided, for example, there may be twenty or more switches 54 which are identical in appearance to the switches 5|, 52 and 53. A number of such switches are illustrated in Figures 7, 8 and 10 as being disposed at the top of the casing 28, each switch consisting of a fixed contact I30 and a movable contact I3I forming the end of a depressible plunger I32.

Preferably however such switches are embodied in a single control unit illustrated in Figures 5 and 6 wherein the fixed contacts of all the switches 54 are replaced by a conducting ring I35 whilst the fixed contacts of the switches 5|, 52, 53 are replaced by contact elements I5I, I52 and I53 which are mounted in but insulated from the conducting ring I35. The movable contacts of all the switches 5|, 52, 53, 54 are embodied in a rotatable contact arm I35. The ring I35, contacts I5I, I52, I53 and the rotatable contact arm I33 are concealed within a casing I3'I which contains an insulating ring or block I38 in which the contact ring I35 is mounted. The contact arm I36 is connected to a central spindle I39 which is operable from the exterior of the casing I31 by a knob I40 which is provided with a pointer MI. The engagement of the contact arm I36 with the contact ring or with any of the contacts is rendered effective by axial movement of the spindle I39 against the action of spring I42 to bring the end I43 of the spindle I39 into contact with the metallic closure disc I44 of the casing I 31. Thus selection of contacts is effected by rotation of the spindle I39 while the actual closure of a circuit through such contact is effected by axial displacement of the spindle I39.

The casing I3! is provided on its exterior with a scale I50 to enable an authorised user to locate the contacts I5I, I52, I53. The effect of providing a large number of graduations or numerals on the scale I50 is similar to the efiect of providing a large number of contact switch plungers I32 as shown in Figures 7, 8 and 10.

In connection with the arrangement shown in Figure 1, it is obvious that if desired, the coil 44 operating the alarm switch 59 may be eliminated and the alarm switch 59 operated by the armature of the trip coil 45.

I declare that what I claim is:

1. In an electrically releasable lock, at least three solenoids, at least three manually operated switches arranged one in the circuit of each solenoid, and electrical connections for the said solenoids whereby energisation of a given one ofsaid solenoids is adapted automatically to close a break in the circuit of a second solenoid which in turn is adapted to close a break in the circuit of a third solenoid whereby the lock can be released by energisation of said solenoids in predetermined sequence, a trip coil which is adapted, when energised, to render said first mentioned solenoid inoperative and which is normally connected, for energisation thereof, with the manually operated switches of said second and third solenoids and contacts automatically operated between said trip coil and the manually operated switches of said second and third solenoids, said contacts being opened on energisation of said first and second solenoids respectively in order to disconnect the trip coil from said respective manually operated switches.

2. In an electrically releasable lock, at least three manually operated switches, a number of solenoids under the control of said switches, a trip coil which is normally connected, for energisaticn thereof, with at least two of said manually operated switches and adapted, on energisation thereof, to render at leastone of said solenoids inoperative and electrical connections including automatically operated contacts between said switches, coil and solenoids whereby the lock can be released by correct operation of said manually operated switches in predetermined sequence only and provided there is no intermediate operation in its wrong order of a manually operated switch, not previously operated in the sequence, said solenoid which is adapted to be rendered inoperativepbysaid trip coilhaving a break in its? circuit which'is' normally closed but opened on energisation of the trip coil.

3. In an electrically releasable look, at least three solenoids, at least three manually operated switches arranged one in the circuit of each solenoid, and electrical connections for the said solenoids whereby energisation of a given one of said solenoids is adapted to close a break in the circuit of a second solenoid which in turn is adapted on energisation automatically to close a break in the circuit of a third solenoid whereby the lock can be released by energisation of said solenoids in predetermined sequence, a trip coil which is normally connected, for energisation thereof, with the manually operated switches of said second and third solenoids, automatically operated contacts between said trip coil and the manually operated switches of said second and third solenoids, said contacts being opened on energisation of said first and second solenoids respectively in order to disconnect the trip coil from said respective manually operated switches and contacts in the circuit of the first mentioned solenoid, which contacts are normally closed but opened on energisation of the trip coil to render said solenoid inoperative.

4. In an electrically releasable look, at least three solenoids, at least three manually operated switches arranged one in the circuit of each solenoid, normally open hold-on circuits for at least two of said solenoids, and electrical connections for the said solenoids whereby energisation of a given one of said solenoids is adapted to close its own hold-on circuit and to automatically close a break in the circuit of a second solenoid which in turn is adapted on energisation to close its own hold-on circuit and automatically to close a break in the circuit of a third solenoid whereby the lock can be released by energisation of said solenoids in predetermined sequence, a trip coil which is adapted, when energised, to render said first mentioned solenoid inoperative and which is normally connected, for energisation thereof, with the manually operated switches of said second and third solenoids and contacts between said trip coil and the manually operated switches of said second. and third solenoids, said contacts being opened on energisation of said first and second solenoids respectively in order to disconnect the trip coil from said respective manually operated switches.

5. In an electrically releasable lock, at least three solenoids, at least three manually operated switches arranged one in the circuit of each solenoid, normally open hold-on circuits for at least two of said solenoids, at least one additional switch similar in appearance to said manually operated switches, and electrical connections for the said solenoids whereby energisation of a given one of said solenoids is adapted to close its own hold-on circuit and to close a break in the circuit of a second solenoid which in turn is adapted to close its own hold-on circuit and to close a break in the circuit of a third solenoid whereby the lock can be released by energisation of said solenoids in predetermined sequence, a trip coil which is adapted, when energised, to render said first mentioned solenoid inoperative and which is normally connected, for energisation thereof, with said additional switch and with the manually operated switches of said second and third solenoids, contacts between said trip coil and the manually operated switches of said second and third solenoids,

said: contacts being opened on energisation of said first and second solenoids respectively .in. order to disconnect the trip coil from said respective manually operated switches, a warning device and aswitch controlling said warning device and solenoid and in the circuit of another to render the solenoids operable in predetermined sequence only to release the look, a trip coil adapted, when energised, to render at least one of said solenoids inoperative to p event release of the lock and so connected with at least two of said manually operated switches that closure of either of said two manually operated switches prior to closure of the automatic switch in the circuit of the solenoid controlled by such manually operated switch would cause energisation of the trip coil.

7. In an electrically releasable lock, manually operated switches, a number of solenoids under the control of said switches, automatically operated switches each under the control of one solenoid and in the circuit of another to render the solenoids operable in predetermined sequence only to release the lock, a trip coil adapted, when energised, to render at least one of said solenoids inoperative to prevent release of the lock and so connected with at least two of said manually operated switches that closure of either of said two manually operated switches prior to closure of the automatic switch in the circuit of the solenoid controlled by such manually operated switch would cause energisation of the trip coil and at least one additional switch, similar in appearance to said manually operated switches, connected to said trip coil to energise'the trip coil on closure thereof.

8. In an electrically releasable look, a multiple switch embodying a number of manually operated switch elements, a number of solenoids under the control of said switch elements, automatically operated switches each under the control of one solenoid and in the circuit of another to render the solenoids operable in predetermined sequence only to release the look, a trip coil adapted, when energised, to render at least one of said solenoids inoperative to prevent release of the lock and so connected with at least two of said manually operated switch elements that closure of either of said switch elements prior to closure of the auto matic switch in the circuit of the solenoid con trolled by such manually operated switch element would cause energisation of the trip coil.

9. In an electrically releasable look, a multiple switch embodying manually operable lock releasing switch elements and at least one manually operable additional switch element, a number of solenoids under the control of said lock releasing switch elements, automatically operated switches each under the control of one solenoid and in the circuit of another to render the solenoids operable in predetermined sequence only to release the look, a trip coil adapted, when energised, to render at least one of said solenoids inoperative to prevent release of the lock and so connected with at least two of said lock-releasing switch elements that closure of either of said two lock-releasing switch elements prior to closure of the automatic switch in the circuit of the solenoid controlled by such lock releasing switch element would cause energisation of the trip coil, said trip coil being also connected to said additional switch element so that closure of said additional switch element is adapted to energise the trip coil.

10. In a lock according to claim 7, a multiple switch embodying said manually operated switches and said additional switch comprising a contactor ring forming part of the additional switch, anumber of contacts insulatedly mounted in said contactor ring and serving as parts 0! the respective manually operated switches, a casing concealing said contactor ring and contacts, a rotary control operable from the exterior of the casing and a contactor arm connected to said 5 control and adapted selectively to form the complementary part of said respective switches.

JACK PATERSON JAMES.

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