Abstract: In a cylinder lock, half tumblers are slidably arranged in pairs in the tumbler inserting holes formed in the key rotor in such a manner that, when the key is not inserted into the lock, the half tumblers are elastically urged in one direction to cause their engaging end portions to engage with the locking engagement grooves formed in the cylinder body to inhibit the rotation of the key rotor. When the key is inserted into the lock, the key engaging portions of the half tumblers engage the key crests to move the half tumblers to disengage their engaging end portions from the locking engagement grooves. When, instead of the key, a picking tool is used to disengage one of each pair of half tumblers from the locking engagement groove to thereby allow the key rotor to turn through a predetermined angle, the other half tumbler is engaged with the locking engagement groove deeper than usual, and the protruded portion of the key rotor covers the key engaging portion, thereby preventing the picking of the lock.

Abstract: A cylinder lock having a removable barrel that includes a control tumbler. The barrel is retained in the housing of the lock by a nib that is formed on either the barrel or the interior of the housing. A longitudinal nib slot is formed on the other of either the barrel or the interior of the housing. The nib and the nib slot are aligned with one another only when the barrel is in an unlocking position for permitting the barrel to be removed from the housing. In this manner, the barrel may be removed from the housing only when both the barrel is in the unlocked position and when a special control key has been inserted into the barrel for withdrawing the control tumbler into the barrel.

Abstract: A key-operable lock having a releasable plug which is rotatable from a locked condition to an unlocked condition. The plug is removable from a fixed mounting member only in the unlocked condition and is blocked for removal in the locked condition by the combined effects of a master key-operable tumbler which is slideable in the plug and a boss which is fixed to the plug. In the locked condition, the boss and one end portion of the control tumbler extend outwardly from the plug to engage a fixed mounting member and the diametrically opposite end portion of the tumbler is inside of the plug. When a master key is inserted into the lock and the plug is rotated to the unlocked position both end portions of the control tumbler are inside of the plug; the boss is aligned with a slot of the mounting member and the plug is free to be removed from the fixed mounting member.

Abstract: A flat key pick resistant cylindrical lock structure which comprises a plug, a sleeve and a housing. The housing is bored off center to receive the sleeve and thus make room for biased split pin tumblers embodying false segments and further, limited misleading internal rotational movement occurs when an attempt is made to pick the lock. Also two shear lines between the plug and sleeve and between the sleeve and housing must be cleared before an unlocking of the lock can be accomplished.

Abstract: A cylinder lock system employing a key having a projection extending from each opposing parallel edge of the key blade, the projections respectively operating an auxiliary pin tumbler stack and cooperating with a groove in the lock shell to retain the key in the lock after plug rotation from the key insertion position. The key retaining projection also cooperates with the driver pin of the auxiliary pin tumbler stack to prevent key trapping, i.e., the presence and size of the retaining projections keeps the auxiliary driver pin from engaging the keyway. The cooperation between the key retaining projection and the auxiliary driver pin is permitted by providing the lock with two shear lines, located on different diameters, which are simultaneously operable by a single key.

Abstract: A rekeyable lock includes a false bible which houses a retainer pin, the retainer pin engaging the lock core. The lock core has a pin tumbler located to selectively engage the retainer pin so as to cause disengagement thereof from the core. The false bible is not physically attached to the core and is configured to match the operating environment.

Abstract: The invention relates to a cylinder lock with a cylinder housing (1) and, rotatably mounted therein, a cylinder plug (2) comprising a key passage extending in its axial direction, with a lock bit (5) coupled to the cylinder plug and rotatably mounted in the cylinder housing (1), there being provided in the cylinder housing and in the cylinder plug a plurality of mutually aligned bores which extend into the passage and in which there are, by a spring force in the direction of the passage, plug pins which are of different lengths and housing pins which are preferably of the same length, there being formed between the cylinder housing and the cylinder plug a first separating joint traversed by the housing pins when the key is not inserted into the lock, the ends of the plug pins so co-operating with the locking notches of the key that when the key is inserted the pins are displaced in their axial direction into a position in which the bearing ends of all plug and housing pins are located in the first separating

Abstract: A cylinder lock system employs a key which has a pair of projections extending from opposing parallel edges of the key blade. The keyway of the lock has an enlarged slot portion for receiving the projections upon insertion of the key. One of the projections cams pins of an auxiliary pin stack to present a shear line between the pins to permit rotation of the key plug to an unlocked mode. The other projection is received in a groove formed in the shell and is engageable against a surface of the groove upon rotation of the key to retain the key within the keyway.

Abstract: A key blade having a longitudinal axis (A) of insertion and comprising an elongated, wave-like generally longitudinally extending code pattern (38) for cooperation with a row (23) of elevationally and rotationally movable locking tumblers (23a-23e) of a rotary cylinder type lock (18). Each of the locking tumblers is provided with a transversely projecting finger which engages with the code pattern (38) when the key blade is inserted into the lock. The code pattern (38) includes a number of concavity locations (40-44) which are displaced longitudinally and transversely so as to correspond to specific rotational and elevational positions of the locking tumblers which will permit releasing of the lock.

Abstract: A lock cylinder with mechanical and electromagnetic locking mechanisms, comprising a lock cylinder stator having a mechanical locking mechanism, a bolt movably mounted in a groove in the stator, and a lock cylinder rotor rotatably coupled to the stator and engaged by the mechanical locking mechanism. An electrical control mechanism controls movement of the bolt. A retaining mechanism coupled to the rotor releasably engages the bolt to permit and prevent movement between the stator and the rotor depending on the position of the bolt.

Abstract: A rotary cylinder lock and a corresponding key blade are disclosed. The cylinder lock comprises a cylinder shell (19), a key plug (20) rotationally mounted in the shell (19) to provide a shear line (21) between the shell and the key plug, a key slot (11) extending into the key plug (20) parallel to the rotational axis thereof for receiving a key blade (1), at least one locking tumbler (23b) including an elongated body portion guided in a complementary cavity (33b) in the key plug (20), the elongated body portion being capable of rotational movement about its longitudinal axis, and a fence member blockingly associated with the locking tumbler and shaped so that rotational positioning of said locking tumbler with a properly shaped key blade allows said fence member to clear the shear line.

Abstract: Pivotable tumblers mounted to a cylindrical plug prevent rotation of the plug unless a correct key in a keyway moves the tumblers to an unlocked position. If the tumblers extend too far into the keyway, pawls mounted in the body and acting on steps of the plug prevent rotation of the plug to an unlocked position. If the tumblers do not extend for enough into the keyway, the tumblers jam up against a reentrant shoulder of the body preventing the plug from reaching the unlocked position. A security keyway closure or door cams off a race in the body and closes the keyway with rotation of the plug. A slot in the key passes the door during operation.

Abstract: A card operated lock includes a lock box in which an inner card slit opened to the interior of a room and a outer card slit opened to the exterior of the room are disposed in substantially coplanar relationship with each other. A lock card having a predetermined pattern of punched engaging holes is inserted previously into the inner card slit while a key card comprising the same pattern of punched engaging holes as the lock card is inserted into the outer card slit when the lock is unlocked or opened. A plurality of rocking tumblers each of which is substantially in the form of a T-shaped plate are inserted into the lock box in the form of an array extended in the widthwise direction of the key card and perpendicular to the card slits. A horizontal bar portion of each T-shaped rocking tumbler is extended along both the inner and outer card slits.

Abstract: There is disclosed an improved rotatable cylinder lock of the type formed by a cylindrical housing and a removable elongated lock core, the cylinder housing including a tumbler block positioned within the cylindrical housing and extending inwardly with respect to the cylindrical housing, and a tumbler ledge having an interior peripheral surface mounted within the cylinder housing adjacent the tumbler block and extending circumferentially for a portion of the periphery of the cylinder housing, the lock core including a plurality of lock tumblers and a release tumbler which is positionally carried by the lock core to ride on a shoulder formed by the tumbler ledge throughout the rotational movement of the lock core, except in the unlocked position when the release tumbler is positioned such that it is free of blockage by the tumbler block thereby to permit removal of the lock core from the cylindrical housing, the lock core further including a block restrictor relief section formed therein which accommodates the

Abstract: A cylinder lock with key, incorporating a picking preventing means, comprises a plug mounted rotatably within the cylindrical seat of a lock cylinder and has a first set of holes lying on a radial plane. The holes accommodate pins which cooperate with tumbler pins accommodated in a second set of holes formed in the cylinder and being aligned with the first set of holes. A longitudinal key slot extends through the plug which is in communication with the first set of holes and has a longitudinal rib arranged to project thereinto to provide support for the pins. The rib conceals the ends of the pins resting thereon, and defines an intersection of the longitudinal key slot with the cylindrical portions of said first set of holes accommodating said pins. One of the pins has the same length as the hole accommodating it, thereby if deceitfully shifted, it will unavoidably engage the hole of the respective tumbler pin and produce a locked condition of the lock.

Abstract: An improved, key-operated locking device using an axially fixed rotating arm, employing the anvil and rotating keeper arm concept with the anvil extending laterally from the housing. The keeper arm, with lock cylinder assembly, is firmly retained within the housing through the use of a retaining pin, and is rotatable within the lock housing to move from the lock-closed to lock-opened positions in order to confine or release the slide of a slide fastener on a zipper-type closing fabric bag, utilizing a lower detent pin having a stepped cylinder shape located axially in the tubular bore in the lock housing, which is resiliently biased against the distal end of the lock cylinder assembly, with the smaller diameter end projecting along the axis into the axial keyway just past the lowermost tumbler of the lock cylinder assembly. This pins serves to defeat attempts at unauthorized access by lock picking.

Abstract: A key comprises a key body provided with at least one translatably movable plunger able to be displaced in a housing provided in the key, the plunger being intended to co-operate with a positioning member provided in the recess of a rotor so as to project from its recess and to push a movable pin of the rotor into a position permitting rotation of the barrel rotor relative to the stator. The key comprises in its head a constricted zone, and the recess of the movable plunger is provided in this constricted zone.

Abstract: A piston type lock employs stepped diameter pistons or pins and bores to prevent fallout of pins on disassembly and also multilevel surfaces at the lock rotor and housing interface such that one or more of the pins serve to retain the rotor in the housing in the unlocked condition of the lock.

Abstract: A cylinder lock (1) has a normal locking mode (12 o'clock position) and a service locking mode (10 o'clock position). When the cylinder plug (3) is left in the service mode of the lock, with the aid of a standard key, the lock can be turned with the aid of a service key (9). The service key is latched against withdrawal in the normal mode of the lock, by means of an intermediate pin (7') of larger diameter than a corresponding upper pin (4) in the normal mode of the lock. The intermediate pin can be received in a widened part (3b') of a corresponding pin-channel (3a') in the cylinder plug, but is unable to enter the pin channel (2a) of the cylinder housing of smaller diameter, hence latching the service key (9). Subsequent to using the service key (9), the cylinder is returned to the normal locking mode (12 o'clock position) with the aid of the standard key, whereafter the lock can only be opened with the aid of the standard key.

Abstract: A cycle lock having at least one plurality of disc-like tumblers loosely mounted on a shaft parallel with the axis of rotation of the key rotated lock cylinder. Each tumbler has a two spaced lobes which, in the neutral state of the tumbler, contact the arcuate surface of the cylinder but one of the lobes may drop into the key slot in the cylinder if not occupied by a high segment on the key. A key is initially inserted into the lock at a special location at which all tumblers are in their neutral state, and the rotation of the key to its normal position of insertion and removal will set the lock tumblers according to the key coding. In one embodiment particularly useful for hotels, etc., two sets of tumblers are employed: one set for transient or guest keys, a second set for service personnel keys, and a third key, a grand master key, operates the second tumbler set and can reset both sets of tumblers for accepting new keys with different codings thereon.

Abstract: A magnetic bolt has a movable and electromagnetically operable locking member which, in conjunction with a locking part arranged on the rotor of a lock cylinder, blocks or releases the rotor, independently of the mechanical tumblers depending on whether the locking member is located in a free-running slot or a locking notch of the locking part. The magnetic bolt is arranged in a recess in the lock cylinder stator and provides an electromagnetic locking operation by energizing a field coil.

Abstract: A pick resistant lock includes a secondary hole in the cylinder which is turned into alignment with a driver pin as the lock is being opened. A shuttle pin slidably positioned in the secondary bore prevents the driver pin from entering the secondary bore when a key bit is inserted in the key way. However, when there is no key bit in the key way, the driver pin will drop into the secondary bore and prevent opening the lock. Two embodiments of the lock also include features to prevent the driver pin from being pushed out of the secondary bore without disassembling the lock. In one of these embodiments, the shuttle pin is locked against movement by a tertiary pin, and in another embodiment, the service pin blocks access to the shuttle pin to accomplish this result.

Abstract: A closure device has a cylinder core turnable in a housing and a key insertable into a key channel in the core. A ball provided in a circumferential groove in the inner wall of the housing cooperates with an edge portion of the key. A pin is arranged in the same plane and 180.degree. away from the ball.

Abstract: An improved locking device of combination lock comprises a combination lock having toothed combination wheels, a three-way locking means formed with the shaft of the combination lock, a three-extension key and a rear locking pin normally poking into the key hole of the locking means to prevent from turning the combination lock for enhancing security.

Abstract: A padlock is provided with bidirectional locking pins so that a key can be turned in either direction to operate the padlock. The padlock has a circular slot in the bottom portion to allow the insertion of a cylindrical key which has teeth and recesses corresponding with the lock pins. A locking ball holds a U-shaped lock bar in place. When the key is turned the ball moves inwardly to release the lock bar and to unlock the padlock. Turning the key in the opposite operation will lock the padlock.

Abstract: The cylinder lock includes, in addition to conventional segmented tumbler pins, auxiliary tumbler elements movable at an oblique angle relative to the keyway and being engageable at one end into arresting recesses in the housing; the other end of the auxiliary tumbler cooperates with a camming surface on a feeler pin, the end of which projects into the keyway and is controlled by corresponding recesses provided on lateral sides of the key.

Abstract: A duplex lock codable by a master key and releasable by a duplex key and comprising a first fixed hollow cylindrical body in which a second cylindrical body is rotatably mounted. An axially shiftable slider is firmly secured to the second cylindrical body for locking it relative to the first cylindrical body by insertion in a cavity provided at the bottom of the first cylindrical body. When the slider is withdrawn, the two cylindrical bodies are released. The slider is provided with a plurality of axially spaced recesses which by axial movement of the slider can be brought into alignment with a plurality of apertures in the rotatable cylindrical body. Each of the apertures accommodates a U-shaped rocker lever having a front U-shaped end facing the slider and a rear end attached to a helical spring tending to pull the rocker lever toward an abutment surface in the interior of the rotatable cylindrical body.

Abstract: A self-shut type lock device comprising a self-shut protector provided in the keyhole capable of hiding the lower tumbler segments from being picked through the keyhole.

Abstract: The invention relates to a tamper-resistant lock. The improved lock incorporates metal wafers which rest on the bottom pins in the inner cylinder of a cylindrical key lock. The wafers and the pins upon which they rest alternately incorporate holes in their topside. The wafers and the bottom pins cooperate with trap pins housed in the outer cylinder of the lock at a 45.degree. angle from the vertical insertion position of the key. The trap pins are urged into the holes in the wafers and bottom pins when tampering occurs. This apparatus prevents both the picking or impressioning of the lock, common alternative techniques for opening a key lock without the key. The improved lock also incorporates a feature to prevent unauthorized opening by rapid spinning of the lock by a spring-propelled insert placed into the lock cylinder after it has been picked.

Abstract: The invention relates to an improved construction for a cylinder lock and key, more particularly to a cylinder lock which has a plurality of pin tumblers of different lengths and diameters arranged radially about the axis of a rotatable cylinder, a pin tumbler longitudinally provided at the rear end of a stationary cylinder, a ball being further provided between said rotatable cylinder and stationary cylinder, and a matching key which comprises a tubular shank having thereon a plurality of depressions corresponding to said radially arranged pin tumblers.

Abstract: A pick-resistant-multiple-pin-tumbler cylinder for a lock is disclosed, the principal embodiments of which include an integral, key-displaceable, booby-trapped, lock-up element within the cylinder shell, and slidably mounted in relation to a portion of the rotationally displacable cylinder plug and in which the lock-up element contains a T-shaped peripheral notch which engages and receives a fixed pin or lug projecting from the bore and is thus both slidably and rotatively received in the shell and spring pressed axially for engagement of its shaped notch with the pin, whereby the peripheral dimension of the notch limits the rotation of the plug to a small angle until the lock-up trapping element is thrust towards the rear of the cylinder through the insertion into the plug's keyway of a properly profiled key, imparting a predetermined linear displacement effecting disengagement of the lock-up element.

Abstract: The plug of a cylindrical lock includes at each side of its key channel a blind boring communicating with a conical recess in an arresting plate secured to the housing of the lock. The blind boring intersects cylindrical rotary control members arranged for rotation in the plug and each having a diametrical passage coinciding in one angular position thereof with the blind boring. A series of arresting balls is arranged in the blind boring and in respective passages in such a manner as to resume in the aligned position of the members a blocking position in which the terminal ball is in engagement with the conical recess. During the rotation of the plug by a correct key the arresting balls are shifted by the inclined surfaces of the conical recess into the blind boring and the plug is free to rotate. By the insertion of a wrong key at least one passage is misaligned and consequently the terminal arresting ball cannot be removed from its arresting recess.

Abstract: A single key-operated keeper lock for a zipper-type slide fastener includes a barrel assembly of a tubular barrel and an anvil fixed to and projecting radially from the barrel, a plug assembly of a lock cylinder rotatably received in the barrel and a keeper arm fixed to and projecting radially from the cylinder adjacent to a proximal end thereof, the plug assembly being rotatable relative to the barrel assembly between alternate positions for alternately securing a fastener element between the keeper arm and the anvil, and releasing the element, tumblers carried by the cylinder, movable into engagement with the barrel to prevent the relative rotation, and movable out of such engagement by insertion of a key in the cylinder in the direction of the axis of rotation, a locking bar reciprocally movable in the barrel rectilinearly along such axis between a base portion of the barrel and a distal end portion of the cylinder, the base portion defining a recess receiving the locking bar in each of the several positio

Abstract: Apparatus and method for a secure multi-level key system. A multi-level key system utilizes ribs of known width upon the higher level keys to properly displace obstruction pins corresponding to selected locking pins of the lock housing. A two-part cylinder pin is utilized in order that a higher level key may equalize the spring-biased locking pin with a shallower groove than is necessary for a subordinate key to equalize the same locking pin. The obstruction pins sense the presence or absence of the ribs associated with the high order keys. Subordinate keys, lacking ribs, depend on the additional displacement of the cylinder pin to properly position the obstruction pins to unlock the lock. Creation of a higher order key requires a two-step process of reducing the depth of the groove corresponding to a given cylinder pin of the lock as well as building up the ribs required to offset the obstruction pins associated with the same cylinder pin of the lock.

Abstract: The invention contemplates a cylinder lock and associated flat-key configuration, the lock being virtually pick-proof and the key being virtually imitation-proof. These features arise from a particular employment of supplementary lateral ribs or cams on the key, of predetermined height and longitudinal location, coacting with a system of supplementary pins guided by transverse bores in the cylinder core, and one or more case pins of the conventional pin-tumbler components of the lock will dog the cylinder against key-operation beyond a limiting angle, should the supplementary rib or cam profile of the inserted key be incorrect.

Abstract: A key-actuated security entry system for an inwardly opening door to prevent unauthorized opening of the door. The system includes a pivotal, floor-engaging doorstop mounted on the door inside surface near its base, a key-actuated tumbler lock mounted through the door, preferably below the doorknob handle, the lock including a rotatable shaft protruding from the inside lock housing surface, and a cable connected to the shaft and the pivotal doorstop. The shaft includes a rachet lock requiring a proper key to disengage the shaft from the lock housing to permit shaft rotation by the key. Shaft rotation lifts the doorstop permitting entry through the doorway.

Abstract: A pick-proof lock of the cylinder type primarily intended for use in doors, which includes a locking collar or sleeve slidably mounted around a portion of the cylinder plug and which contains a notch to receive a spring pressed pin which is contained in the cylindrical shell of the lock. The collar or sleeve is slidably and rotatively received in the shell and spring pressed for engagement of its notch with the pin, whereby rotation of the plug within the shell can only be accomplished to effect unlocking of the lock when the spring urged locking collar has been displaced rearwardly of the lock from a projected locking position to a retracted unlocking position. Since the locking collar and the pin which locks said collar to the shell do not communicate with the keyway of the plug, tools and other instruments normally used for picking locks are ineffective in picking the lock.

Abstract: An actuating mechanism for actuating electrical switches to insure coordinated connection of circuits vital to safe operation of a mass-transit vehicle includes a frame upon which are mounted one or more electrical switches. Also included is a cam rotatably mounted on the frame for actuating engagement with the switches upon rotation of the cam by key or similar device. The actuating mechanism further includes a toggle mechanism that is connected at one end to the frame and at the other end to the cam at a point spaced from the point of mounting of the cam to the frame. Secured to the toggle mechanism is a spring whose dead center position does not coincide with the point of actuating contact of the cam with the switch such that upon rotation of the cam, the spring resists movement of the cam until the dead center position of the spring is reached.

Abstract: An augmented key and cylinder lock has a housing with a bore therein concentric about an axis. A plug in the bore is rotatable about the axis and has a flange on one end. There is a radial pin tumbler mechanism in the plug and housing access to which is afforded by a keyway in the plug which extends through the flange leaving a notch therein. A key serrated along one edge to operate the pin tumbler mechanism is receivable in the keyway to occupy an operating position. In that position, a shoulder adjacent the serrated edge of the key substantially abuts the end face of the flange. In that position another, axially elongated shoulder on the key adjacent its other edge axially displaces a spring pressed detent, supported on the housing, out of the notch. This frees the plug from rotational restraint by the detent.

Abstract: An axial tumbler type lock having a split cylinder within a stationary lock casing contains a set of regular spring-urged split tumblers which bridge the shear line to render the lock active and which are depressed to the shear line by a tubular key to allow turning of the lock to a release position. A modified split tumbler with a reduced forward pin extension also bridges the shear line of the lock and responds only to a special key having a forward pin extension for depressing the special split tumbler to the shear line. Additionally, the lock possesses one or more hidden tumblers in the non-rotational lock cylinder section which are spring-urged and have the capability of moving forwardly into the pocket for the special tumbler or into the pockets of any of the regular tumblers if the proper key is not employed to depress the special tumbler to the shear line, or if the rotational section of the lock cylinder is somehow turned without the proper key in place.

Abstract: A lock which includes a barrel member for mounting to a lockable article, such as a door, and which carries a rotatable plug. The plug includes spring biased tumblers. A key is inserted into the plug and engages the tumblers to release the plug for rotation relative to the barrel member, with one of the tumblers interlocking with the key to prevent its removal from the plug when the plug is rotated to an unlocked position.

Abstract: A lock device comprising a housing having a plurality of rotatable cylindrical members therein, one of said cylindrical members being integral with a latch operating member, each of said cylindrical members having one or more tumblers, said tumblers normally holding said cylindrical members in a locked non-rotatable position, said cylindrical members being inter-engaged with each having limited relative movement, and an operating member engaging and operating said tumblers in a given order to rotate said cylindrical members in a like order, said cylindrical members progressively joining together in rotation until all of said tumblers have been engaged and operated at which time all of said cylindrical members will be inter-engaged to rotate as a unit to move said latch operating member to an unlock position.

Abstract: An automobile ignition lock includes a plug with a plurality of tumblers. The plug is rotatably mounted in a cylinder and includes a slot for receipt of a tumbler actuating key. A key bolt is positioned at the inner end of the key slot and is movable in response to insertion of the key in the key slot from a plug locking to a plug unlocking position. Excessive longitudinal transfer or movement of the key bolt relocks the plug and cylinder and prevents relative rotation. Thus, a key with appropriate bitting and of appropriate length must be used to effect unlocking of the plug from the cylinder. As an additional security feature of the lock, the plug is designed with a circumferential slot that fractures and separates the plug into two separate portions when an attempt is made to forceably rotate the plug relative to the cylinder.

Abstract: A turnover key with indentations on both sides for operation of bolt keepers of a cylinder lock, and with a sloped keyway at the tip of the key. The sloped keyway, which is situated before each row of indentation, runs almost to the opposite broad side of the key and into it.

Abstract: A highly safe, relatively pick-proof lock to be used as a replacement for standard lock cylinders in conventional doors. A plurality of independently operating locking means serving to enhance the difficulty of picking a lock including split keyways, locking cams, shear line blocking means and a hardened steel face plate.

Abstract: A pick-proof lock of the cylinder type primarily intended for use in doors, which includes a locking collar or sleeve slidably mounted around a portion of the cylinder plug and which contains a notch to receive a spring pressed pin which is contained in the cylindrical shell of the lock. The collar or sleeve is slidably and rotatively received in the shell and spring pressed for engagement of its notch with the pin, whereby rotation of the plug within the shell can only be accomplished to effect unlocking of the lock when the spring urged locking collar has been displaced rearwardly of the lock from a projected locking position to a retracted unlocking position. Since the locking collar and the pin which locks said collar to the shell do not communicate with the keyway of the plug, tools and other instruments normally used for picking locks are ineffective in picking the lock.