MAGNETIC LOCK AND KEY

Abstract: A lock for operation by a magnetic key has a magnetic locking element (47) which moves in aligned, longitudinal grooves formed in inner (10) and outer (18) members of the lock. When the locking element is aligned with a transverse channel (57) in the inner member, limited relative rotation of the members can occur.

Description: r Title: "Magnetic Lock and Key" This invention relates to a lock and key, there being associated- with the key a permanent magnetic field and the lock comprising at least one magnetic locking element which can be moved from a locking position to a releasing position by the magnetic, field of the key, when the key is applied to the lock. A magnetic lock, and key are described in U.S. Patent No. 2,177,996. This lock comprises a hollow plug arranged for rotation within a sleeve. Axially extending grooves formed in the plug and sleeve collectively define a path along which a magnetic ball can be moved by the magnetic field of the key from a locking- position to a releasing position. In the locking position, the ball is engageable with, abutment surfaces at opposite sides of its path, these surfaces being formed on the plug, and sleeve, respectively, so that relative rotation of the plug and sleeve is restrained ' . • In the sleeve, there is formed a circurαferentially extending groove which communicates with the axially extending groove. When the ball is in its releasing position, it is aligned with the circumferentially extending groove so that relative rotation of the plug- and sleeve is possible. A second magnetic ball is disposed in a similar pair of axially extending grooves which communicate with • the circumferentially extending groove. The possibility of providing further magnetic locking balls is mentioned. One disadvantage of the lock described in the afore¬ said U.S. Patent is that manufacture of the lock becomes unduly complex if. the number of magnetic elements is increased. In order- to provide a sufficiently large number of different locks and keys to ensure proper security, a number- of locking elements exceeding two is required. The U.S. Patent proposes that the number of different locks and keys which can be produced should be increased by varying the position relative to the grooves of a driving lug of the key. However, this simple mechanical expedient does not. provide adequate security. According to a first aspect of the present invention, there is provided a lock comprising an inner member, a hollow outer member in which the inner member is mounted and a magnetic element, wherein the inner and outer members collectively define a path to which the magnetic element is confined and along which the magnetic element can move between a releasing position and a locking- position, the inner and outer members have respective abutment surfaces facing in opposit directions transverse to the length of said path and disposed at opposite sides of said path, said abutment surfaces are engageable concurrently with the magnetic element except when the magnetic element occupies its releasing position, whereby relative movement of the inner and outer members in said directions is restricted or prevented by engagement of the magnetic element with the abutment surface except when the magnetic element occupies its releasing position and wherein there is in the abutment surface of the inner member an opening which a part of the magnetic element can enter when the element is in its releasing position. According to a second aspect of the invention, there is- provided a lock comprising an inner member, a hollow outer member in which the inner member is mounted for turning relative thereto about an axis, a housing i which the outer member is .received, an element which i -movable by a key between a locking- position in which ' -i prevents relative turning of said members about the axi and a releasing position in which it permits at leas limited relative turning of the members, and a sto element which- releasably prevents turning of the oute member relative to the housing until the inner member ha been turned through a predetermined angle to effect release of the outer member fo -turning with the inne member. According to a third aspect of the invention, ther is provided a lock comprising an inner member, a hollo outer member in which the inner member is mounted and a magnetic element, wherein the inner and outer members collectively define a path to which the magnetic element is confined and along- which the magnetic element can move between a releasing position and a locking position, the ■ inner and outer members have respective abutment surfaces facing- in opposite directions transverse to the length of said path and disposed at opposite sides of said path, said abutment surfaces are engageable concurrently with the magnetic element except when the magnetic element occupies its releasing position, whereby relative move¬ ment of the inner and outer members in said directions is restricted or prevented by engagement of the magnetic element with the abutment surfaces except when the magnetic element occupies its releasing position, ■ the inner and outer members are each formed with a respective groove, respective parts of said grooves collectively form said path and wherein one of the inner and outer members has an element extending across its groove between the ends thereof to limit travel of the magnetic element along ' the groove. According to a fourth aspect of the invention, there is provided a lock comprising a tubular inner element, a sleeve in which the inner element is. mounted and a magnetic element, wherein the inner- element and sleeve collectively define a path to which the magnetic element is confined and along which the magnetic element can move between a releasing position and a locking position, the inner element and the sleeve have respective abutment surfaces facing in opposite directions transverse to the length of said path and disposed, at opposite sides of said path, said abutment surfaces, are engageable concurrently with the magnetic element except when the magnetic element occupies its releasing position, whereby relative movement of the inner- element and sleeve in said directions is restricted or prevented by engage¬ ment of the magnetic element with the abutment surfaces except when the magnetic element occupies its releasing position and wherein the inner element and the sleeve- have respective channels extending along their entire lengths and each, containing a respective part of the magnetic element, the abutment surfaces being boundary surfaces of the channels. According-to-a-fif-th.- aaμ.ac_t__o___J:he_inventiσn, there is provided a lock and key whereof the lock has. an operating member which can be turned about an axis when the key is applied to the lock, said operating member can be locked in a selected-one of a plurality of alternative positions upon withdrawl of the key from the lock and the lock includes a. key-retaining member which also turns about the axis during operation of the lock and is adapted to retain the key except when the operating member is in one of said .alternative positions. 3ecause the key-retaining member participates in turning about the axis, it is not necessary to modify the shape of the key-retaining member according to the number of and relationship between the alternative positions in which the operating member can be locked. According to a still further aspect of the invention, there is provided a key with which there is associated a permanent magnetic field, the key comprising a shank formed at least partly of magnetic material and having a pole face which has a longer dimension extending along the shank and a shorter dimension extending around the shan . There is also provided in accordance with the invention the combination comprising a lock according to any one of the first, second, third and fourth aspects of the invention and- a key having a shank which presents a plurality of magnetic poles and is adapted to transmit torque to at least one of the inner and outer- members of the lock. One example of a lock and key embodying each aspect of the invention will now be described, with reference to the accompanying drawings wherein:- FIGURE " 1 shows an end view of the- lock, the key being- absent from the lock; FIGURE 2 shows an opposite 'end view of the loc ; FIGURE 3 shews a cross-section on the line III-III of Figure 1, together with a key of which the shank- is present in the lock; FIGURE 4 shows a cross-section on the line IV-IV of the lock and key, prior to rotation of the key; FIGURE 5 shows a cross-section on the line IV-IV of Figure 3 after the key has been rotated through an angle of 30°; FIGURE 6 shows a cross-section on the line VI-VI of Figure 3- prior to turning of the key; FIGURE 7 shows a cross-section on the line VI-VI after the key has been rotated through an angle of 30°; and FIGURE 8 shows a cross-section of the lock on the line VIII-VIII of Figure 3- -^-TE i - The lock illustrated in the accompanying drawings comprises an inner member 10 of generally cylindrical form having a longitudinal axis 11 about which the inner member is turned by means of a key 12 during operation of the lock. On an end portion 13 of the .inner member, called herein the rear end portion, there is formed a pair of flats 14 which engage an operating arm 15 within a non-circular opening of the arm. The arm is trapped on the inner member between a eirclip 16 and a nut 17. The arm 15 is used to control a device which is to be controlled by the lock. For example, the arm itself may be a latch. Alternatively, there may be formed on the arm a. cam surface which co-operates with an element (not shown) controlled by the lock. The lock further comprises a hollow outer member 18, also of generally cylindrical form, within which the inner .member 10 is mounted. The outer member is concentric with the inner member and is -a sliding fit on the inner member. The outer member- 18 is disposed within a housing 19, relative to which, the outer member can turn about the axis 11 when the proper key is used to operate the lock. The shape of the housing may be selected according to the intended use of the lock. As illustrated, the housing may be formed in a plurality of parts, at least some of which may be provided with screw threads to enable the parts of the housing to be releasably secured together. In the example illustrated, a front part 20 of the housing extends through an opening in a mounting plate 21 and is secured therein by a nut 22 screwed onto the front housing part. The entire housing will normally be fixed during use of the lock. A stop element 23 is provided for releasably preventing turning of the outer member 18 relative to the housing 19 until the inner member 10 has been turned by - means of the key 12 through a predetermined angle to effect release of the outer member. The stop element is in the form of a bolt having a central opening through which the rear end portion 13 of the inner member protrudes. The bolt is held against a rea end face 24 of the outer member 18 by a bolt carrier 25- The .bolt carrier is of hollow, generally cylindrical form having one end wall and an external diameter equal to that of the outer membe 18. The bolt carrier has three limb3 26, 27, 28 which project from the end wall of the carrier in the forward direction through the central aperture of the bolt. Five grooves are formed in the external surface of the inner member 10, each of these grooves being rectilinear, parallel to the axis 11 and extending along the entire, length: of the inner member. The limbs 26, 27 and 28 of the bolt carrier engage in respective ones of these grooves indicated by the reference numerals 29, 30 and 31« The bolt carrier is thereby constrained to turn about the axis 11 with the inner member relative to the bolt and the outer member. There is formed in the wall of the -outer member 18 adjacent to the rear end. thereof an opening 32. Openings having dimensions extending ' c rcumf rentially of the axis 11 similar to the corresponding dimension of the opening 32 are formed in a rear part 33 of the housing 19 adjacent to a rear wall 3 of the housing. In the example illustrated*, there are four of these openings in the housing identified by the reference numerals 35 to 38. ,The bolt 23 has a nose 39 which can protrude through the opening 32 into any selected one of the openings 35 to 38 and thereby restrain turning of the outer member 18 about the axis 11 relative to the housing. The bolt is urged into the active position .illustrated in Figure 3 by a leaf spring 40 having a mid portion which bears against the bolt and end portions which bear against the internal face of the outer member 18. Engagement of the nose 39 of the bolt in the opening 32 prevents turning of the bolt relative to the outer member. Fro the nose 39 there projects into the central " opening of the bolt 23 an abutment 41 of the bolt. When the key is absent from the lock, the abutment 41 is aligned with the limb 27 of the bolt carrier 25 as shown in Figure 4 so that complete withdrawal of the bolt from the opening of the housing is prevented by engagement of the abutment 41 with the limb 27 which constitutes an abutment of the bolt carrier. If the key 12 is inserted into the inner member 10 and the key and inner member are then turned in either direction about the axis 11, the limb 27 is moved out of alignment with the abutment 41 so that the nose 39 of the bolt can move towards the axis 11. Turning of the inner member in either direction also brings one or other of the limbs 26 and 28 into engagement with a respective surface 42 or 43 on the bolt which faces generally in a direction away from the leaf -spring 40 and towards the nose 39. Further turning of the inner member causes the bolt to slide between, the end face 24 of the outer member and the end wall of the bolt carrier in a direction transverse to the axis 11 until 'the nose 39 is substanti¬ ally withdrawn from the opening of the housing. As shown, the nose 39 may be provided with a rounded tip which will automatically be forced out of the opening in the housing upon rotation of the bolt and outer member relative to the housing, provided the nose is substanti¬ ally withdrawn from the opening of the housing before rotation of the outer member commences. Thus, by turning of the inner member 10 the bolt can be moved to the releasing position illustrated in Figure 5 in which it no longer restrains rotation of the outer member 18. The outer member 18 consists of a tubular element 44 and an end cap 45 secured on the front end of the element 44. In the internal surface of the element 44,_ there is formed a number of grooves equal to the number of grooves provided in the external surface of the inner member 10. The circum rential extent and 'spacing between the grooves 46 of the outer member are the same as those of the grooves of the inner member so that each of the grooves 46 can be aligned .with a corresponding groove of the inner member. The grooves 46 also extend along the entire length of the element 44 and are parallel to the axis 11. Three magnetic elements 47, 48 and 49 are each disposed partly in the groove 30.of the inner member and partly in the corresponding groove 46 of the outer ' member. In the particular example illustrated, each magnetic element is in the form- of a hollow cylinder having flat end faces which are engageable with boundary surfaces of the grooves 30 and 46. In the example illustrated, each of these grooves has a transverse cross-section of rectangular shape with flat abutment surfaces at opposite sides of the grooves. The groove 30 extends through a major part of the thickness of the inner member 10, almost to the central bore 50 thereof. There are also formed in the outer surface of the inner member 10 a plurality of relatively shallow circum rentially extending grooves 51 contain¬ ing respective rings 52 to 55. The ring 52 lies adjacent to the rear end of the inner member. The rings 53 to 55 lie between the ends of the groove 30 and are spaced apart from each other along the axis 11. As shown in Figure 3- the magnetic elements 47 to 49 lie between respective different pairs of the rings 52 to 55 so that travel of the magnetic elements along the groove 30 is limited to prevent two or more magnetic elements occupy¬ ing the same part of the groove. In the absence of the key, each magnetic element is free to move along a respective path defined collectively by the boundary surfaces of the grooves 30 and 46, these paths being co- linear and parallel to the axis 11. 1u ln the abutment surfaces at opposite sides of th groove 30, there are formed openings 56 which ar sufficiently large to receive that part of a magneti element 47 to 49 which is normally disposed in the groov 30. In the example illustrated, there is in each abut ment surface a single opening- for the element 47, single opening for the element 48 and two axially space openings for the element 49. The openings 56 are forme by the provision of transversely extending channels i the external surface of the inner member 10. A The boundary surface of each transverse channel 5 which faces away from the axis 11, that is the base o the channel, is. such that there can be drawn on the bas of the channel" a rectilinear line transverse to th length of the groove 30. At the position where transverse channel 57 intersects the groove 30, the dept of the transverse channel is equal to that of th.e groove. The depth of the transverse channel decreases graduall in both, directions away from the groove 30 until the transverse channel runs out onto the. external surface of the inner member-. In the particular example illustrated, the base of each transverse channel is flat. When any one of the magnetic elements 47, 48 and 49 is not aligned with a corresponding one of the transverse channels 57, that element is said to be in a locking position and, by engagement with opposed abutment surfaces of the inner and outer members, it prevents or restricts turning of the inner member about the axis 11 relative to the outer member._ When the key is absent from the lock, at least some and usually all of the magnetic elements will occupy locking positions. It will be noted that the depth of the groove 30 significantly exceeds one half of the corresponding dimension of the magnetic elements and that the depth of the grooves 46 is similar to that of the groove 30. However, the depth of these ' grooves is significantly less than the corresponding dimension of the magnetic elements. There is associated with the key 12 a permanent magnetic field such that, when a shank 58 of the key is introduced into the central bore 50 of the inner member, each of the magnetic elements is biased by the magnetic field into a releasing position where it is aligned with a respective one of the transverse channels 57. Thus, the magnetic elements are no longer engaged between oppositely facing abutment surfaces and the inner member can be turned about the axis 11 in either direc¬ tion relative to the outer member 18. Since a part of each magnetic element remains in the groove 4β, such turning causes each magnetic element to move along the base of the corresponding transverse channel and there¬ fore to move further away from the axi.s 11. Before such movement is interrupted by engagement of the magnetic elements with a radially inwardly facing surface of the outer member, the outer member itself is freed for turning movement with the inner member by retraction of the nose 39 of the bolt from the opening in the housing 19. Continued turning of the inner member 10 is then accompanied by turning of the outer member relative to the housing. The inner member is turned sufficiently to bring about operation of an associated device by means of the arm 15. The arm 15 can be locked in a selected angular position by turning the inner member 10 in the reverse direction relative to the outer member 18 whilst the nose 39 of the bolt is aligned with a selected one of the openings 35 to 38 in the housing 19- Such alignment is indicated to a user by noticably increased resistance to turning of the inner member 10 which is necessary to force the rounded tip of the nose 39 out of one of the openings in the housing, against the action of the spring 40. t will be understood that reverse rotation of the inner member 10 relative to the outer member 18 causes the magnetic elements 47, 48 and 49 to move along their respective transverse channels 57 into alignment with the groove 30 once more. Withdrawal of the key then displaces the magnetic elements along their respective paths of movement into locking positions. In the end cap 45, there are formed three recesses 59 having- open sides facing alon -the axis 11 towards the inner member 10. In each, of these recesses there is disposed. a freely rotatable- ball 60. of hardened steel. These balls prevent the drilling away of the end cap so that the inner member 10 can be withdrawn from the outer member 18. The end cap also defines a non-circular opening 61 through which the key shank can be introduced into the bore 50 of the inner member. The opening βl comprises a circular portion having the same diameter-as, and being- aligned with, the bore 50 and a rectangular extension 62 of the circular portion. The shank .58 of the key is of generally cylindrical form but . has, adjacent to a handle of the key, a radially projecting lug 63 having dimensions such that it can pass through the extension 62 of the opening in the end cap. Immedi¬ ately adjacent to the opening 61 and between that opening and the inner member IQ, there is in the end cap 45 an arcuate recess 64 which accommodates the lug 63 of the key when the key is turned relative to the outer member 18 through an angle of 30° in either direction after the lug has passed through the opening 61. After the key has been turned through an angle of 30° relative to the outer member, torque can be transmitted from the key to the outer member by engagement of the lug 63 with boundary surfaces of the recess 64. The lug 63 also transmits torque to the inner member 10 by engaging in a recess 65 at the front end thereof. ,-»° ' There is only a small clearance between the ' lug- 63 and the boundary surfaces of the- recess 65 so that no significant turning, of the key relative to the inner member 10 is permitted. It will be seen that portions of the end cap 45 bordering the rectangular extension 62 of the opening therein trap the key in the bore 50 of the inner member whenever the nose 39 of the bolt is with¬ drawn or substantially withdrawn from the openings 35 to 38 of the housing. Only when the nose 39 is engaged in an opening of the housing can be the. limb 27 be moved into alignment with the abutment 41 to align the lug 63 with the extension 62 of the opening in the end cap and thereby permit extraction o " the key from the lock. The end cap 45 may include flaps 66 which substanti¬ ally close the opening of the end cap when the key is absent from the lock. The end cap is preferably formed of a resilient plastics material by a moulding process. The inner member 10 and the tubular element 44 of the outer member are preferably formed of a non-magnetic metal, for example aluminium or. brass. Since the groove 30 and other grooves of the inner member and the grooves 46 of the outer member are rectilinear and extend along the entire lengths of the inner member and element 44 respectively, these grooves can conveniently be formed by an extrusion process. This has the advantage that smooth abutment surfaces on the inner and outer members can be achieved without careful machining of the inner and outer members. The other grooves and openings in the inner and outer members are formed by machining extruded tubular workpieces. It will be noted that each transverse channel 57 can be formed by a single straight cut across the inner member 10. The inner member 10 is preferably formed by extrusion with " a central opening 67 of smaller diameter than the bore 50, the bore subsequently being formed in the inner member by machining-. It will be noted from Figure 3 that the bore 50 does not extend into the rear end. portion 13 of the inner member. The key shank 58 is provided with magnetic pole faces at positions corresponding to respective paths of the magnetic elements. Each pole face has a length, measured along the axis 11, which exceeds its width, measured circumferentially of the axis 11 and a maximum flux density at a position corresponding to the releasing position of the associated magnetic element. In the example illustrated, the magnetic element 49 has two releasing positions and is moved into one of these positions by a master key and into the other position by another key. It will be understood that the number of magnetic elements in each groove of the inner member can be varied. In the particular example described, only one groove of the inner member contains magnetic elements but generally more than one groove will contain at least one magnetic element. Locks will also d iffer one from the other in respect of the relation between the releasing position of each magnetic element and the ends of its path of movement. By appropriate choice of the relative positions of the paths of the magnetic elements, the magnetic pole faces of the key can be spaced well apart. This facilitates the establishment of high flux densities at the magnetic poles so that reliable operation of the lock by the key is assured even under adverse conditions. O PI

Claims: CLAIMS 1. A lock comprising an inner member (10), a hollow outer member (18) in which the inner member is mounted and a magnetic element (47), wherein the inner and outer members collectively define a path to which the magnetic element is confined and along which the magnetic element can move between a releasing position and a locking position, the inner and outer members have respective abutment surfaces facing in opposite directions trans- , verse to the length of said path and disposed at opposite sides of said path and said abutment surfaces are engageable concurrently with the magnetic element except when the magnetic element occupies its releasing position, whereby relative movement of the inner and outer members in said directions is restricted or prevented by engagement of the magnetic element with the abutment surface except when the magnetic element occupies its releasing position, characterised in that there is in the abutment surface of the inner member an opening (56) which a part of the magnetic element (47) can enter when the element is in its releasing position. 2. A lock according to Claim 1 wherein said opening (56) is formed by the intersection of a tranverse channel (57) and said path, one boundary of the transverse channel being a surface of the inner member which faces towards the outer member and contains a rectilinear line transverse to said path. 3. A lock according to Claim- 2 wherein the transverse channel (57) extends from said path in opposite directions . 4. A lock according to Claim 2 or Claim 3 wherein said surface of the transverse channel (57) is flat. 5. . A lock according to any preceding claim wherein, when the locking- element (47) is in its releasing position, the inner and outer members (10, 18) can undergo limited relative rotation about an axis (11) parallel to the length of said path. 6. A lock according- to Claim 5 further comprising a housing (19) for the outer member (18) and a stop element (23) which releasably prevents turning of the outer member (18) relative to the housing until the inner member has been turned through a predetermined angle to effect release of the outer member for turning with the inner member. 7. A lock according to Claim 9 wherein the stop element (23) is a slidable bolt which is movable transversely of the axis between an active position and an inactive position- in its active position the bolt engages in respective openings in the outer member and. in the hous¬ ing- and the inner member (10) has an abutment (27) which, when the locking element (47) is in its locking position, is engageable with the bolt to. prevent movement of the bolt from its active position to its inactive position. 8. A lock according to Claim 7 wherein the housing (19) has a plurality of openings (35, 36, 37, 38), in any selected one of which the bolt (23) can engage to. restrain turning of the outer member relative to the housing. 9. A lock according to any preceding claim wherein the inner member (10) has a bore to receive a shank (58) of the key (12), the outer member (18) defines a non- circular aperture through which the key shank can be introduced into the bore of the inner member and there is adjacent to the aperture a space (64) which can accommodate " a non-circular part (63) of the key shank comple entary to said ap » - c<_re after such part has been passed through the aper ture and then turned about the axis to trap the key shank in the outer member. 10. A lock according to any preceding claim wherein at least one of said inner and _outer members is formed by an extrusion process with respective channels each extend—- ing from one end of the member to the other end and a part of the magnetic element is received in the channel. 13. A lock comprising an inner member, a hallow outer member in which the inner member is mounted and a magnetic element, wherein the inner and outer members collectively define a path to which the magnetic element, is confined and along ' which the magnetic element can move between a releasing position and a locking position, the inner and outer members have respective abutment surfaces fac-ing in opposite directions transverse to the length of said path and disposed at opposite sides of said path and wherein said abutment surfaces are engageable concur¬ rently with the magnetic element except when the magnetic element occupies'-- its releasing position, whereby relative movement of the inner and outer members in said directions is restricted or prevented by engagement of the magnetic element with the abutment surfaces except when the magnetic element occupies its releasing position, wherein the inner and outer members are each formed with a respective groove, respective parts of said groove collectively form said path and wherein one of the inner and outer members has an element extending across its groove between the ends thereof to limit travel of the magnetic element along the ' grooves. 14. A lock comprising a tubular inner element, a sleeve in which the inner element is mounted and a magnetic element, wherein the inner element and the sleeve collectively define a path to which the magnetic element is confined and along which the magnetic element can move between a releasing position and a locking position, the inner element and the sleeve have respective abutment surfaces facing in opposite directions transverse to the length of said path " and disposed at opposite sides of said path, said abutment surfaces are engageable con¬ currently with the magnetic element except when the magnetic element occupies its releasing position, whereby relative movement of the inner element and sleeve in said directions is restricted or prevented by engage¬ ment of the magnetic element with the abutment surfaces except when the magnetic element occupies its releasing - position and wherein the inner element and the sleeve have respective grooves extending along: their entire lengths and each containing a respective part of the magnetic element, the abutment surfaces being boundary surfaces of the grooves. 15.. A lock and key whereof the lock has an operating member whieh can be turned about. n axis when the key is applied to the lock, said operating member can be locked in a selected one of a plurality of alternative positions upon withdrawl of the key from the lock and the lock includes, a key-retaining member which also turns about tne axis during operation of the lock and is adapted to retain the key except when the operating member is in one of said alternative positions. *.-->.

Inventors: HERRIOTT L
Applicants: HERRIOTT L, LOWE & FLETCHER LTD
Application year: 1981
Main classification: E05B47
IPC codes: E05B47