US 5,749,252 AGranted

Manipulation resistant combination lock and method

AssigneeSargent & Greenleaf, Inc.

InventorMartin Richard Rhoades

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Abstract

A manipulation resistant combination lock includes a housing, a drive cam attached a drive shaft, a moveable bolt, a fence attached to a fence lever, and tumbler wheels. A fence lever is pivotally attached to the bolt, and has a nose portion engageable with a drive cam gate in the drive cam which is keyed to the drive shaft and includes two spaced multi-surface contact rollers of magnetically attractable material on opposite sides of the drive cam gate. Each contact roller has a plurality of non-identical surfaces which is uniquely radially positioned and oriented relative to the axis of rotation of each contact roller. A permanent magnet is mounted in the nose portion of the fence lever thereon to assert an attraction force which rotates the contact roller as the contact roller approaches the nose portion of the fence lever due to rotation of the drive cam. The nose portion physically contacts the contact roller and causes it to rotate to a new position of rotation in which a different surface of the roller is positioned to contact the nose during subsequent rotation of the cam, so as to defeat successful manipulation of the lock.

Claims18

Dependent claims

An improved manipulation resistant combination lock including manipulation defeating means for impeding unauthorized opening of the combination lock through manipulation of the lock components, wherein said lock includes:

a housing;
a bolt slidably mounted for movement in the housing between a locked extended position and an unlocked retracted position;
a pivotably mounted movable fence lever having a nose portion;
a fence member mounted on said fence lever;
a drive cam mounted for rotation in said housing and having an outer periphery in which a drive gate having a pulling surface and a pushing surface is provided;
said nose portion of said movable fence lever being urged into contact with the outer periphery of said drive cam;
a plurality of tumbler wheels that are alienable with said fence member when said tumbler wheel gates are positioned in a predetermined manner;
a pulling side multi-surface contact roller mounted for rotation about a roller rotation axis on said rotary drive cam adjacent the outer periphery of said rotary drive cam and also adjacent said pulling surface of said drive gate and positioned to engage said nose portion in response to rotation of said drive cam;
a pushing side multi-surface contact roller mounted for rotation about a roller rotation axis on said rotary drive cam adjacent the outer periphery of said drive cam and also adjacent said pushing surface of said drive gate and positioned to engage said nose portion in response to rotation of said rotary drive cam;
a first one of said multi-surface contact rollers having a plurality of non-identical nose contact surfaces each of which is uniquely radially positioned and oriented relative to the rotation axis of said first multi-surface contact roller so that said nose portion will engage one of said nose contact surfaces in response to rotation of said one drive cam and cause rotation of said multi-surface contact roller to position another one of said nose contact surfaces for engagement by said nose portion during a subsequent rotation of said drive cam so that the angular position of the drive cam at each time of contact of said one multi-surface contact roller is randomly variable for each such contact so as to prevent repetitive manually detectable characteristics during subsequent rotation of the drive cam.

7 more elements

In a combination lock having a pivotal fence lever having a nose portion urged against a dial driven rotary drive cam having an outer periphery adjacently facing the fence lever and an inwardly extending drive gate having first and second sides, the improvement comprising:

a rotatable contact roller mounted for unlimited rotation on a support pin having an axis and having an outer periphery including discrete surfaces extending about and defining the outer periphery of said contact roller each oriented differently to the other and with each discrete surface being spaced a different distance from the axis of the support pin;
said support pin being mounted on the drive cam adjacent the periphery of said drive cam and adjacent one side of said drive gate so that one of said discrete surfaces contacts said nose portion during rotation of said rotary drive cam so that said drive cam rotates the contact roller sufficiently so that the nose portion contacts another one of said discrete surfaces during subsequent rotation of said drive cam so as to create a different feel at the dial and reduce the possibility that manipulation of the lock cam reveals the combination.

A method of preventing successful manipulation of a combination lock having a dial driven drive cam having a peripheral surface and a drive gate and a pivotal fence lever with a nose portion urged into contact with the peripheral surface of the drive cam, said method comprising the steps of:

(a) rotating the drive cam to cause the drive gate to approach said nose portion so that the nose portion engages a first surface of a multi-surface contact body mounted on the drive cam in a first relative position to said drive cam at a time when said drive cam is in a first angular position of rotation to result in a first manual feel at the dial and (b) continuing rotation of said drive cam so that said nose portion rides over and moves said multi-surface contact body to a second position relative to said drive cam following which the nose portion moves out of contact with said multi-surface contact body, said second position being such that a second surface of said multi-surface contact body is then positioned so as to be subsequently engageable by said nose portion when said drive cam is in a second angular position of rotation so as to result in a second manual feel at the dial different from said first manual feel so as to prevent a manipulator from manually determining the position of the drive gate.

Dependencies are inferred from the claim text.