Description of Invention

From one aspect, this invention relates to a lock of the kind, hereinafter called the kind specified, compri¬ sing two relatively movable juxtaposed members, a magnetic element movable along a track defined collect¬ ively by said members and respective abutment surfaces on each of said members, the abutment surfaces defining opposite boundaries of said track and there being in one of the abutment surfaces an opening in which the magnetic element can be at least partly received when the magnetic element occupies a releasing position along its track, whereby movement of said members in a direction to move the abutment surface towards each other is restricted by the magnetic element to a lesser degree when the magnetic element is in its releasing position than when the magnetic element is in some other position between the abutment surfaces. ^' The invention also relates to a method of manufacturing a lock of the kind specified.

One example of a lock of the kind specified is described in U.S. Patent Specification 2,177,996. The lock therein described comprises a hollow plug which is rotatably mounted in a hollow cylinder. The cylinder and the plug are formed at the interface between them with axially extending grooves which contain locking elements of magnetic material, one half of each locking element lying in a groove formed in the plug and the other half of that element lying in the adjacent groove formed in the cylinder. There is also formed in the cylinder a circumferential groove communicating with the. axially extending grooves. When the locking element is in its releasing position, it is aligned with this circumfer- entially extending groove and the plug can be rotated

relative to the cylinder. One end of the axially extending groove in the plug is open and an opposite end of the corresponding groove in the cylinder is open. At least when the key is absent, there is unobstructed communication between the grooves and the atmosphere outside the lock. This permits foreign matter, for example dust and ^' moisture, to enter the grooves along which the magnetic element is required to move.

Locks of the kind specified which have been proposed heretofore are so arranged and constructed that the magnetic elements are concealed within the lock structure when the lock has been assembled sufficiently to enable its operation to be tested.

According to a first aspect of the invention, there is provided ^" a lock of the kind speci ied wherein an aperture extends through one of said members .and forms a part of the track along which the magnetic element moves and there is associated with said one member a closure element which prevents escape of the magnetic .element from its track through said one member.

The closure element is preferably adapted to enable the magnetic element to be viewed through the closure element.

The closure element may be formed of transparent material.

Said one member is preferably of tubular form, the closure element being formed as a sleeve which, adjacent to its ends, is a sufficiently close fit on said member to prevent particles of solid foreign matter entering between the closure element and one member, and is a less close fit on said one .member in a region, between the ends.

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The sealing relation between said one member and the sleeve may be established at one end of the sleeve by -a ring having retaining elements which seat in recesses formed in the sleeve and, when so seated, are substan¬ tially flush with an external surface of the sleeve, the retaining elements being adapted to project radially out¬ wardly from the" external surface of the sleeve when engaged with the ^" sleeve but not seated in the recesses. With this arrangement, any one inspecting the assembled sleeve and ring can readily determine whether these parts are in the proper positional relation with each other. Furthermore, if the sleeve and ring are fitted into a bore formed in a body of the lock, the arrangement can ensure that the assembled ring and sleeve can be inserted into the bore only when the retaining elements are properly seated in their recesses.

In the preferred construction, each of said members is formed with an aperture in which a respective part of the magnetic element lies and there is associated with each member a respective closure element, the .closure elements overlapping with faces of the associated members adjacent to the apertures therein and extending across the apertures.

The track defined by said members and along which the magnetic element can move may be substantially parallel to one or both of said faces.

Opposite boundaries of both of the apertures are preferably spaced apart by a distance slightly greater than the corresponding dimension of the magnetic element, so that said boundaries guide the magnetic element when it moves along its track.

One of the closure elements may define a boundary of a key-receiving opening in the lock. This closure

element is preferably thin. The closure element may be thinner than the- adjacent one of said members and prefer¬ ably has a thickness within the range 0.1 to 1.75 mm.

The closure element which defines a boundary of the key-receiving opening may seal against ingress of foreign matter apertures ^' in the adjacent one of said members. The closure element may be in the form of a tube and sealed at least adjacent to its ends with respect to the adjacent member.

Each closure element may be fixedly secured to the adjacent one of said members.

In all of its positions, the magnetic element may be constrained to lie partly in the aperture in one of said members and partly in the aperture in the other member.

The magnetic element may move relative to .both of said members when it moves along its path.

According to a second aspect of the invention, there is provided a method of manufacturing a lock of the kind specified wherein said members are assembled together,, a cut is then made through one of ^* the members into the other member to remove material from both of the members and s.o form the track and a closure element is subse¬ quently associated with said one member to prevent escape of the magnetic element from the track through said one member.

Preferably, both of said members are of tubular form, -one is disposed inside the other, the cut extends completely through the thickness of each member to form apertures therein and closure elements are applied subse¬ quently one to the inside of the inner member and one to the outside of the outer member.

After making the cut, the members may be separated and further material cut from one of the members to form the opening for receiving the magnetic element when in its .releasing position. The further material may be cut by means of a rotary cutter which penetrates through the thickness of the.one member by a distance such that the axis of rotation of the cutting tool does not pass through the thickness of the one member.

One example of a lock according to the first aspect of the invention which is manufactured by the method according to the second aspect of the invention will now be described with reference to the accompanying drawings wherei :-

FIGURE 1 shows a longitudinal cross-section of the lock;

FIGURE 2 shows a cross-section on the line II-II of Figure 1; and

FIGURE 3 illustrates a step in the manufacture of the lock.

The lock comprises a body 10 which, when the lock is in use, is normally disposed in a housing of a device to be controlled by the lock. Alternatively, the body 10 could be incorporated in the device to provide a housing for the lock. The function of the body 10 is to mount in a device to be controlled by the lock a lock mechanism contained in the body.There are mounted in the body, for rotation together about an axis 11, an inner member 12 and an outer member 13 in which the inner member is disposed.

The inner member 12 is adapted to transmit torque from a key (not shown) to a driven member 39 of the

device controlled by the lock. The inner member -is of tubular form, being open at both ends and adjacent to one end, called herein the axially outer end, is formed at one side of the axis 11 with an axially extending slot 14 for receiving a radially projecting lug on a key when the key is inserted into the inner member. An axially inner end of the inner member 12 projects beyond the outer member 13 and engages in torque-transmitting relation with the driven member 39

The outer member 13 constitutes a part of means for preventing rotation of the inner member 12 except when a proper key having a magnetic field of predetermined configuration is present in the inner member. The outer member is a sliding fit on the inner member and, when the proper key is present, can undergo limited axial movement relative to the inner ^' member. The outer member is const¬ rained to rotate with the inner member by ,a radially inwardly projecting tooth 15 on the outer member adjacent to the axially inner end thereof and engaging in an axially extending slot in the inner member.

• At axially spaced positions, there are formed in the outer member 13 three apertures 16, 17 and 18 respect¬ ively. Each of these apertures comprises an elongate portion 19, the length of which extends around the axis 11, and a communicating portion 20 which extends from the portion 19- in a direction along the axis. The communi¬ cating portion lies between the ends of the elongate portion. The inner member 12 has three elongate apertures 21, 22 • and 23 _> each of which lies directly radially ^' inwardly of a corresponding one of the elongate portions of the apertures 16, 17 and 18.

The apertures 16 and 21 collectively afford a track along which a first magnetic locking element 24 can move a limited distance around the axis 11. The pair of

apertures 17 and 22 and the pair of apertures 18 and 23 afford similar paths for magnetic locking elements 25 and 26 respectively. In the particular example shown, the locking elements are formed as rollers and are arranged to roll along their respective paths. Each roller has flat end surfaces which face along the axis 11 towards respective abutment- surface ^' s of the inner and outer members 12 and 13 which define opposite boundaries of the tracks along which, the magnetic elements can move. The axial dimensio of each of the apertures 21, 22 and 23 and of the elongate portion 19 of each of the apertures 16, 17 and 18 is slightly greater than the length of the locking elements so that relative axial movement of the inner and outer members 12 and 13 is obstructed, unless each one of the locking elements is in a releasing position in which it is aligned with the communicating portion 20 of the associated aperture in the outer member 13. These communicating portions are of a size such that they can receive a part of a magnetic element when the outer member moves relative to the inner member towards the axially outer end of the lock.

There is formed on the outer member 13 at its axially inner end an axially projecting cam formation 27 which is received in a complementary recess in a ring 28 carried on the axially inner end portion 29 of the inner member 12. The ring 28 is constrained against rotation relative to the ^" body 10 by a tooth 30 on the ring which engages in a slot formed in the body.

The inner member 12 is constrained against axial displacement relative to the body 10 by engagement of opposite end faces of the inner, member with adjacent surfaces of the body. The cam formation 27 is offset from the axis 11 so that when the inner and outer members 12 and 13 are turned about the axis, displacement of the outer member 13 along the axis towards the outer end of

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the body must occur. If such displacement is obstructed by one or more of the magnetic elements 24, 25 and 26, then rotation of the inner member 12 is prevented.

The key can be inserted into and withdrawn from the inner member 12-only when the cam formation 27 is aligned with the complementary recess in the ring 28. A spring 31 is provided ^' for urging the outer member 13 inwardly along the axis 11. to the position shown in Figure 1, where the magnetic elements 2.4, '25 and 26 are free to move along their respective tracks around the axis 11 under the action of gravity.

The apertures in the inner and outer members 12 and 13 are formed by cutting material from these members. The inner and outer members are assembled together and held in the relative posi.tions shown in Figure 1. The aperture 21 and the elongate portion 19 of the aperture 16 are then cut in a single cutting operation by the same milling tool 32, in the manner shown in Figure 3. The milling tool has cutting teeth around its periphery and is moved towards the axis 11 until the periphery of the tool is approximately half way between the axis and the internal surface of the inner member 12. The cutting tool is then withdrawn, moved axially to the position of the aperture 22 and a further cut is made through the inner and outer members. A further cut is made at the position of the aperture 23- The inner and outer members are then dis-assembled and further material is cut from the outer member 13 to form the communicating portions 20 of the apertures therein.

After the apertures 21, 22 and 23 have been cut in the inner member 12, a closure element is applied to the inner member- to close these apertures - at the radially inner surface of the inner member. The closure element is in the form of a sleeve 33 which overlies the internal

surface of the inner member and completely covers each of the apertures therein.

Opposite end portions of the sleeve 33 are spread to form flanges on the ends of the sleeve. One or both of the flanges is or are formed after the sleeve has been inserted into the inner member 12. The -flanges co¬ operate with axially facing surfaces on the inner member to prevent axial movement of the sleeve relative to the inner member and also seal the sleeve to the inner member against the passage of dust or moisture along the inter¬ face between them.

The sleeve 33 is formed of non-magnetic material, typically brass, and is thin, as compared with the inner member 12. The sleeve preferably has a thickness in the range 0.1 to 1.75 mm. The sleeve defines the boundary of the key-receiving opening of the lock and, at. least when the key is present, supports the magnetic elements 24, 25 and 26 on its outer surface. It will be understood that the magnetic elements are spaced from the key only- by the thickness of the sleeve 33•

The magnetic elements 24, 25 and 26 are inserted into their respective tracks after the inner and outer members 12 and 13 have been assembled - with each other once more, the sleeve 33 being present in the inner member 12. A closure element is then applied over the outer member 13 to close the apertures therein at the outer periphery of the outer member and so prevent the magnetic elements falling out of their tracks. The closure element on the outer member 13 is in the form of a sleeve 34 formed of a transparent plastics material. This material is dimensionally stable under all tempera¬ tures to which the lock is likely to be subjected in use and has some degree of resilient flexibility.

The outer sleeve 3 is a tighter fit on the outer member 13 adjacent to the ends of the sleeve than it is mid-way between the ends.

As can be seen from Figure 1 , there is a small clearance space between the outer sleeve 34 and each of the magnetic elements 24, 25 and 26. At its axially inner end the outer sleeve is an interference fit on the outer member 13 so that a sealing relation is established between the. sleeve 34 and the outer member. This seal is at least effective to prevent particles of solid matter entering between the sleeve 34 and the outer member and is preferably fluid-tight.

At the opposite end of the sleeve, a sealing relation is established with the outer member by a sealing ring 35 of the outer- sleeve. The sealing ring is formed of a resiliently flexible plastics material and has an inner portion 36 which tightly embraces the outer member 13. The ring presents in the axially inward direction an annular groove in which a free-end portion of the main component of the outer sleeve 34 fits tightly. On the sealing ring there, are provided retaining elements 37 which extend in the axially. inward direction at the outside of the main component of the outer sleeve and have at their free ends radially inwardly directed protuberances. When the sealing ring, is' properly assembled with the main component, these protuberances seat in recesses formed in the main compon¬ ent and the retaining elements are substantially flush with the external surface of the main component. If the protuberances are not properly seated in their recesses, they cause the retaining elements to project radially beyond the external surface of the main component so that the sealing ring cannot enter the body 10.

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Alternatively, a one-piece a sleeve may be prov¬ ided, a sealing ^" relation being established between this sleeve and the outer member 13 adjacent to the axially outer end of the sleeve by an interference fit of the sleeve on the outer member. With this alternative arran- . gement, the outer member may be provided with a radially outwardly projecting rib adjacent to the axially outer end of the sleeve to limit axially outward movement of the outer sleeve relative to the outer member.

It will be noted that, adjacent to its axially inner end, the outer sleeve 34 is formed with a radially inwardly projecting rib which engages a shoulder on the outer member 13 to retain the sleeve thereon. As the sleeve is moved onto the outer member from the axially . inner end thereof, this rib 40 is expanded radially until it clears the shoulder so that the sleeve is a snap fit ^' on the outer member.

It will be appreciated that all parts of the lock, excepting the magnetic elements 24, 25 and 26, are prefe¬ rably formed of non-magnetic materials. It will be further noted that the apertures 21, 22 and 23 do not extend completely around the axis 11. Thus, reliance -is not placed solely upon the inner sleeve 33 to maintain a mechanical connection between opposite end portions of the inner member. Further magnetic elements may be disposed in further tracks which are offset from the tracks of the elements 24, 25 and 26 angularly about the axis 11 but occupy the same positions along the axis.

Each of the tracks of the magnetic elements prefer¬ ably subtends at the axis 11 an angle within the range 90 to 150 . In a case where two tracks are provided at the same position along the axis and spaced from each other angularly about the axis ^' , material of the inner member 12 lying between these two tracks provides an

' adequate mechanical connection between parts of the inner member lying on-opposite sides of these tracks.

The communicating portion 20 of each of the apertures 16, 17 and 18 is preferably formed by removing material from the outer member 13 by means of teeth on the periphery of a milling cutter which rotates about an axis parallel to the axis 11. The milling cutter is moved towards the axis until it penetrates the inner -surface of the outer member 13 along an arc slightly greater than the diameter of the magnetic elements 24, 25 and 26. The communicating portion thus formed has a pair of. opposite boundary surfaces of part-cylindrical form with the axis of curvature being disposed outside the . outer member. The separation between these surfaces increases in a direction from the inside towards the out¬ side of the outer member. As can be seen from Figure 2, the abutment surface of the elongate portion 19 of the aperture has, adjacent to the communicating portion 20, an approximately triangular part 38, the apex of which lies at the interface between the inner and outer .members 12 and 13 and at approximately the same distance from the axis 11 as does the centre of the associated magnetic locking element. <

The magnetic elements, 24, 25 and 26 preferably have recesses in their end surfaces or are hollow. If. an attempt is made to turn the inner member 12 about the axis 11 whilst a magnetic element of this form is only partly aligned with the communicating portion 20 of the associated aperture in the outer member, the approxi¬ mately triangular portion 3 _. 8 of the outer member will bear against the magnetic element and twist the magnetic element slightly about an axis perpendicular to the axis 11. This twisting will enable the acute apex of the part 38 to enter slightly into the interior of the magnetic element and thereby prevent movement of the magnetic element fully into its releasing position.

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The inner sleeve 33, inner member 12, outer member 13, outer sleeve 34, sealing ring 35 and magnetic elements 24, 25 ' and 26 can be assembled together to provide a unit which can easily be handled without risk of the components of the unit becoming separated from, each other. Furthermore, the tracks of the magnetic elements in the.unit are sealed against entry of foreign matter which would interfere with free rolling of the magnetic elements along their tracks. The number of magnetic elements ^' - in the unit and the positioning of these elements by the proper key can be checked visually through the transparent outer sleeve 34.

^• If required, the spring 31 ma be disposed adjacent to the axially inner end of the outer member 13 and the cam 29 disposed adjacent to the axially outer end of the outer member. In this case, upon operation of the lock, the outer member would move axially outwards.and it would be necessary for the communicating portions -20 of the openings to extend from the associated portions 19 in the direction opposite to that illustrated in Figure- 1.

In "the example of lock illustrated, the body ^' 10 comprises 3 components 40,41 and 42 which are assembled together. If required, these components may be formed of. steel since the body is not directly adjacent to the magnetic rollers, 24,25 and 26. Alternatively, the outer sleeve 34 may be omitted, the body component 41 fitting onto the outer member 13 to retain the magnetic rollers 24,25 and 26 therein. .

If required, the body components 40 and 41 may be integral with each other. In order to reduce the risk of moisture penetrating to the interior of the lock, the inner member 12 may be sealed to the body 10. Thus, at the interface between the body component 40 and the inner

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member 12 there is a resilient sealing ring. It will be noted that the inner member 12 is rotated relative to the body by means of the key but is not required to move axially relative to the body. Sealing of the inner ^• member to the body does not interfere with axial movement ^■ of the outer member 13 under the influence of the spring 31. If required, . a further seal could be provided between the body and the inner, member adjacent to the axially inner end of the latter.

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