Single lever, double changeable safe deposit lock
BACKGROUND AND OBJECTS OF THE INVENTION 
     The present invention relates in general to key locks, and more particularly to key locks for safe deposit boxes and the like, wherein both a guard key or &#34;prep&#34; key and a renter&#39;s key having a proper configuration on the key bit must be inserted into the lock and rotated to effect retraction of the bolt, and wherein the lock is capable of being changed in the field for different guard or prep keys and for different renter keys. 
     It will be appreciated that safe deposit boxes in bank vaults and similar security installations are successively leased to different parties, to whom the lessor furnishes a renter&#39;s key adapted to open a given safe deposit box when the lock is partially operated or armed by a guard or prep key in the possession of the lessor. Often, lessees fail to return the renter&#39;s key at the expiration of their lease, or the lessee may lose the renter&#39;s key, and it becomes necessary in such cases to change the safe deposit key lock so that it can be operated by a renter&#39;s key bit having a different configuration. Also, even if the lessee returns the renter&#39;s key at the expiration of his lease, it is desirable to change the key bit configuration to which the lock is responsive whenever the lessee of the box is changed, to prevent the otherwise possible use of an unauthorized duplicate of the renter&#39;s key which may have been made before the renter&#39;s key was returned. 
     For this reason, certain safe deposit locks have been made in such a manner that the position of the gatings in the tumblers operated by the renter&#39;s key is changeable, so that the position of the gatings may be adjustably set to be opened by a different renter&#39;s key. The typical practice in this regard has been to provide a change key in the form of a non-round cross-section rod which is insertable into an opening in the safe deposit lock case or rear cover wall and through shaped openings in the renter&#39;s key tumblers, when the safe deposit lock has been activated by the old renter&#39;s key. The combination change key interfits into shaped openings in one of two pivoted companion tumbler sectors for each of the renter&#39;s key tumbler levers, all of which tumbler lever sectors are pivoted on a fixed tumbler post, to decouple the normally mated tumbler lever sections of each of these tumbler levers and permit them to be recoupled in a position corresponding to the configuration of the bit of a new renter&#39;s key. 
     It has become recognized that it is also desirable to provide for the setting of the guard key or prep key tumbler lever system in accordance with different guard key or prep key configurations (hereinafter generally referred to as the prep key), so that the prep key to be used with safe deposit locks can be changed from time to time to provide greater security or to reset the locks when the prep key is lost or when change of guard personnel occurs. Attempts to provide for changing the lock to accommodate different prep keys as well as different renter keys have generally involved use of renter&#39;s key tumbler levers which are either made up of two pivoted companion tumbler sectors which may be selectively decoupled when the lock is in a change mode to permit relative adjustment of one of the tumbler sectors with respect to the other to accommodate the configuration of the bit of the new renter&#39;s key, and also using an entirely different set of prep key tumbler levers disposed in a portion of the lock housing spaced from the renter&#39;s key tumbler levers and a plurality of independently adjustable fence members positioned relative to the prep key tumblers capable of being set to different positions in accordance with different guard key configurations. Such a construction requires a considerably larger space-consuming lock configuration and considerably increases complications and expense in the assembly of safe deposit lock units. 
     The present invention is directed to a double changeable safe deposit box key lock having a single set of tumbler levers operated by both a guard key and a renter key and coactive with a set of a number of slidable fences corresponding to the number of tumbler levers, as distinguished from many prior safe deposit box locks of the tumbler lever types which employ two sets of tumbler levers, one set for operation by the guard key and another set for operation by the renter key. The single lever function is worked by both the guard key and the renter key, the guard key setting the pivot point of the tumbler levers, and the renter key setting the slidable fences when the lock is in a change condition. A change screw is loosened at the change condition to enable the slidable fences to move in response to the key bitting on the renter key, and after setting of the position of the slidable fences by setting of the tumbler lever positions responsive to a renter key, the change screw is tightened to hold the fences in the position to which they are set by the levers and bitting on the new renter key and also responsive to the guard key setting of the pivot points of the levers. 
     An object of the present invention is the provision of a novel construction of a tumbler lever lock for safe deposit boxes and the like, having a single set of tumbler levers and a single set of a corresponding number of slidable fences, wherein the pivot points of the tumbler levers are set by a guard key and the tumblers levers are properly positioned by the bitting on the renter key so as to align gate recesses and edges of the tumbler levers confronting fence formations on the slidslidable fences to enable movement of the lock to unlocking position. Simplification is achieved by enabling both renter key change and guard key change of the tumbler lever positions by one change screw associated with the set of slidable fences, and either both the renter key and the guard key or one of the renter or guard keys can be changed as desired by use of the single change screw. 
     Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1 is a front perspective view of a changeable safe deposit box lock of the tumbler lever type embodying the present invention; 
     FIG. 2 is a horizontal longitudinal section view thereof taken along the line 2--2 of FIG. 1; 
     FIG. 3 is a front view with parts broken away, showing the stack of key operated tumbler levers positioned by proper keys for retraction of the bolt, and with the bolt retracted into unlocked position; 
     FIG. 4 is a front view similar to FIG. 3, but showing the components in locked position; 
     FIG. 5 is a front view similar to FIG. 3, but showing the components in change position for adjusting the tumblers to a new key; 
     FIG. 6 is a front view similar to FIG. 3, but showing the components in set-up position for withdrawal of old renter keys and insertion of new ones; and 
     FIGS. 3A, 4A, 5A, and 6A are fragmentary section views along line 3A--3A of FIG. 3, showing the clamp screw head position for FIGS. 3, 4, 5, and 6 positions for the bolt plate; 
     FIG. 7 is an elevational view of the bolt plate member; and 
     FIGS. 8A, 8B, 8C, and 8D illustrate fragmentary elevational portions of variations of the fence member configuration and the confronting portions of the coacting tumbler level portions for various modifications of the fence member and tumbler lever operating in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     Referring to the drawings, wherein like reference characters designate corresponding parts throughout the several figures, the key operable single lever, double changeable safe deposit box lock of the present invention in indicated generally by the reference character 10, and comprises a lock case 11 and a cover plate 12 assembled by screws with the case to form a box-like enclosure for the lock mechanism. In accordance with conventional practice, the lock case 11 is a generally rectangular housing in the form of a forwardly opening box-like structure to be forwardly closed by the cover plate 12, and comprises parallel top and bottom walls 13, 14, a rear wall 15, and end walls 16 and 17. The end wall 16 has an opening therethrough through which projects a locking bolt formation 19 which is integral with and extends from the elongated bolt plate 20. The front cover plate 12 includes a front panel or wall 21 having screw holes for receiving screws 22 therethrough to be threaded into tapped formations on the top and bottom walls 13, 14, for example as indicated at 13a in FIG. 3 for assembling the cover plate to the case 11. The lock case 11 also includes through holes 23 adjacent the four corners through which mounting screws can extend into tapped openings in the safe deposit box door or other security closure member on which the lock is to be mounted. 
     The cover plate 12 has a pair of forwardly projecting horns or annular bosses 24, 25, one of which serves as the horn for the renter&#39;s key, and the other which serves as the horn for the guard or prep key. In the illustrated embodiment, the horn 24 is the renter&#39;s key horn and the horn 25 is the guard key horn. These horns 24 and 25 serve as outwardly surrounding tubular bearings for hubs or plugs, indicated at 26 and 27, for the renter&#39;s key and guard key respectively, and extend through customary circular openings provided therefor in the door of the conventional safe deposit box compartment or chamber. Mounting screws, in the usual installation, are fitted through the corner holes 23 and project into tapped openings in the safe deposit compartment door to mount the assembled case and cover plate against the inner surface of the door. 
     The bolt plate member 20 includes the usual heavy bolt formation 19 in the form of a thick, generally rectangular block which projects from the lock case through the wall 16 into a conventional keeper recess in the locking or projecting position of the bolt, and includes an integral thinner bolt plate portion 28 extending rearwardly through the major portion of the lock mechanism chamber and includes an elongated slot 29 which receives a stationary guide post 30 extending forwardly from the rear wall of the lock case. The edges of the slot 29 bounding the fixed guide post 30 and the upper and lower edges of the opening 16a in case wall 16 receiving the bolt formation 19 coact to guide the bolt plate member in proper alignment along a horizontal rectilinear path, assuming the usual installation orientation of the lock, for rectilinear reciprocative movement between its projected, locked position and its retracted, unlocked position. The thinner bolt plate portion 28 of the bolt plate member 20 has appropriately shaped downwardly opening recesses to receive the hubs or generally cylindrical arbor portions of the plugs 26, 27 the renter&#39;s key plug 26 being a 2-part assembly having a front plug member 26p journaled in the horn 24 having a keyway or slot therein and a shaft portion 26s coupled against relative rotation with plug member 26p, also having a keyway and a driving tang or projection 26a interfitted in shaped recess 28a of the bolt plate 20. 
     In the illustrated embodiment, a single stack or set of tumbler levers are provided, indicated generally by the reference character 31, each of the levers being of a distorted generally T-shaped configuration having a shortened vertical leg, providing a horizontally elongated body having a vertically elongated slot 32 in the mid-portion thereof receiving the post 30 projecting from the rear wall of the case. The opposite ends of the tumbler levers 31 define a gated end 31a and a guard key activating tail end 31b. The gated end 31a has a fence receiving gate 33 therein of generally teardrop configuration opening through oppositely inclined edge portions 34a, 34b of the gated end 31a which converge forwardly toward the gates 33, the gates 33 and the adjacent edges 34a, 34b being disposed in confronting relation to a pack of selectively adjustable slide fence members 35. The tumbler levers 31 have spring wire members 36 fixed in the guard key actuated tail end portions 31b of the tumbler levers, for example by seating an end portion of each spring wire member 36 in an inclined narrow cut in the side of the tumbler lever tail end portion 31b near the rearmost end thereof which is stamped or deformed to substantially closed condition at the side of the lever through which the narrow cut opens to fix the spring wire therein. The spring wire extends in a forwardly and upwardly inclined path to bear against the top wall or a formation such as the screw receiving boss 13a, of the lock case to resiliently bias the tumbler levers 31 about the post 30 to assume a rest position wherein lift edge surfaces 34d of the tail end portion 31b of the tumbler levers abut the smaller diameter rearwardly projecting cylindrical arbor or shaft portion 27a of the guard key plug 27. 
     The slide fence members 35 are generally L-shaped plates having a vertically elongated, generally rectangular thicker main body portion 39 and a rearwardly projecting, fence forming foot portion 40 which projects horizontally in the direction of the gated portions of the tumbler levers 31 to be received in the gates 33 when the proper keys are inserted in the lock and shifted to unlocking position. The main body portion 39 of the fence members 35 has a vertically elongated slot 41 therein to receive a clamp screw 42, and are restrained in vertical alignment for sliding movement only along a vertical axis perpendicular to the horizontal reciprocating axis of the bolt member by a clamping bracket 43 having a pair of parallel vertical sides 44 which embrace and guide the opposite vertical edges of the main body portions 39 of the fence members 35 and one of which extends rearwardly into a slot 28s therefor in the bolt plate portion 28 of the bolt plate member 20. The clamping bracket 43 is of substantially U-shaped configuration in top plan view and the forwardmost wall 45 thereof includes a thickened portion 45a having a threaded opening therethrough into which the shank portion of the clamp screw 42 extends. In the embodiment illustrated, the clamp screw 42 is an Allen head screw, whose shank portion extends through and is journaled in an appropriately sized opening in the bolt plate 28 and has an enlarged head 42a movable with the bolt in a horizontally elongated shaped cavity 46a in the rear wall 15 of the lock case, arranged to expose the clamp screw head 42a to receive an Allen head wrench or similar manipulating tool to adjust the clamp screw 42 to clamping and release positions relative to the fence members in the clamping bracket 43 when the bolt plate reaches its change position and unlocked position as later described. 
     In the normal condition of the lock, the clamp assembly formed of the clamp screw 42 and clamping bracket 43 for the pack of fence members 35 will be in tightened clamping position holding the vertically elongated rectangular main body portions 39 at vertical positions such that the foot-like fence formations 40 thereof are properly disposed to be received in the gates of the associated tumbler levers 31 when the tumbler levers are adjusted angularly about the posts 30 by the proper renter&#39;s key and guard key for which the slide fence members 35 have been previously adjusted. When the lock is in the locked condition, the bolt plate member 20 is in the projected position of FIG. 4 wherein the fence formations 40 of the fence members are withdrawn from the gates 33 of the tumbler levers 31 and the lower lift surface edges 34c of the portions of the fence levers adjacent the gated end 31a are biased by the spring wire members 36 against the surface of the generally U-shaped arbor or shaft portion 26s of the renter`s key plug 26, and the mounting post 30 bearing against the uppermost end portions of the vertical slots 32 in the tumbler levers. 
     In normal operation to unlock the lock, the guard key is first inserted in the keyway of the guard key plug 27 and rotated clockwise, as viewed in FIGS. 4 and 3, to the unlocking position illustrated in FIG. 3, during which the bitting of the guard key engages the lift edges 34d of the tail end portions 31b of the tumbler levers and establish the pivot points for the tail end portions 31b of the tumbler levers. The appropriate renter key is then inserted into the renter key plug 26 and rotated in a clockwise direction as viewed in FIGS. 4 and 3 to the unlocking position shown in FIG. 3, bringing the bitting on the renter&#39;s key into engagement with the lift edges 34c of the tumbler levers and pivoting the tumbler levers about the contact points of the tail end portions 31b with the guard key to adjust the vertical positions of the gates 33 in the tumbler levers so as to be horizontally aligned in receiving position relative to the fence formations 40 of the fence members 35. Immediately after the renter&#39;s key positions the fence lever gates in proper alignment with the fence formations to receive the latter, the driving cam projection 26a of the driving cam portion 26s engages the shoulder 28b the shaped opening 28a of the bolt plate portion 28 to drive the bolt plate to the retracted position shown in FIG. 3 during the remainder of rotation of the renter&#39;s key to the final unlocking position of FIG. 3. 
     When it is desired to change the renter&#39;s key for the safe deposit box lock, the proper guard key is inserted in the keyway 27a of the guard key plug 27 and is rotated to the approximately 12:30 position shown in FIG. 3 to position to the bitting on the key to establish the proper pivot points for the lift edges 34c of the tail end portions 31b of the tumbler levers 31. The old renter key for which the lock is presently set is then inserted in the keyway 26b of the renter&#39;s key plug 26 and rotated clockwise to the change position shown in FIG. 5, wherein the head 42a of the clamp screw 42 is exposed through the opening 46b of the cavity formation 46a in the rear wall 15, but is not moved so far as to abut or jam against the shelf formation 46c adjacent the rear end of the cavity 46a. A change wrench, such as an Allen wrench, is then inserted through the tool opening 46b into the socket of the clamp screw 42 and rotated through the appropriate range to move the enlarged head 42a rearwardly to a position where it will rearwardly clear the shelf formation 46c. This action also loosens the set of fence members 35 so that they are free to slide vertically to different positions from their present setting, although they do not move at this point because their relative vertical positions are set by the fence formations 40 thereof being disposed in the fence lever gates 33. However, since the head 42a of the clamp screw 42 is now clear of the abutment shelf 46c, the renter&#39;s key and the driver cam projection 26a associated therewith are free to move a further distance in a clockwise direction, further retracting the bolt plate member 20 therewith, until the renter&#39;s key and renter key plug 26 reach the setup position of FIG. 6, where the renter&#39;s key aligns with the change key slot 24s in the horn 24, permitting withdrawal of the old renter key from the key plug 26 while the fence members 39 are still loose. A new renter&#39;s key is then inserted in the keyway of the plug 26 and rotated back to the change position where the clamp screw head 42a abuts the shoulder 46d in the rearwardly enlarged portion of the cavity 46a. The Allen wrench is then reinserted in the head of the clamp screw 42 and rotated to tighten the clamp screw back to tightened condition shown in FIGS. 3A and 4A where it is positioned forwardly at a location to clear the shoulder 46d of the cavity 46a and permit the renter key to be returned to the initial locked position of the renter key horn 26 where it is aligned with the slot 24b of the horn 24 allowing key withdrawal from the lock. 
     The procedure for changing the guard key is similar, in that the guard key and renter&#39;s key are inserted in the appropriate plugs 26 and 27 and rotated to the stop position where the clamp screw head 42a abuts the shelf 46c. The change wrench is then inserted through the opening 46b into the head of the clamp screw 42 and rotated to release the fence members 39. The guard key is then rotated back to locked position where it is aligned with the entry slot 25d of the horn 25 and is withdrawn from the plug 27, the new guard key is inserted and rotated to unlocked position, the clamp screw 42 is then tightened, and the renter key is rotated to the locked position and removed, and the guard key then removed. 
     FIGS. 8A, 8B, 8C, and 8D show various modifications of the configuration of the slide fence members corresponding to the member 35 of the previously described embodiment and the confronting edge portions of the tumbler levers corresponding to the tumbler levers 31 of the preceding embodiment, with the fence members of these variations indicated by the reference character 35 followed by the alphabetical character designating that figure and the adjacent portions of the tumbler lever indicated by the reference character 31 followed by the alphabetical character corresponding to the figure. It will be noted that in the case of FIGS. 8A, 8B and 8C, the slide fence members 35a and 35c are provided with corresponding slots 41A, 41B and 41C coacting with suitably shaped clamping brackets like the clamping bracket 43 with a clamp screw 42 extending therethrough, and have a gate recess, as indicated at 35A-g and 35C-g in FIGS. 8A and 8C and have a projecting foot 35B-f in the case of FIG. 8B, of truncated triangular configuration, coacting with projecting male fence foot formations 31A-f 31C -f in FIGS. 8A and 8C projecting from the tumbler levers, or coacting with gate 31B-g in the case of FIG. 8B. In FIG. 8B, the foot formation 40D is provided on the slide fence member 35D but is located at an intermediate level between the upper and lower ends of the main body portions and coacts with a truncated triangular shaped gating recess 33D in the tumbler levers 31D. The operation of these variations will be well understood from the description of the preferred embodiment illustrated in FIGS. 3-6 and 3A-6A. 
     In the preferred embodiment, the tumbler levers are coined on opposite sides along the key lift edges 34c and 34d, to allow the key levers to fit scissor lock key bitting. This allows one tumbler lever to be used in place of two tumbler levers on scissor-type locks. Also, if desired, the lock construction can be set up for single key operation with a stationary arbor simply replacing the guard key horn 27 and eliminating the guard key horn and guard key plug, so that no guard key is used during set up changing to set the fence members for a particular renter&#39;s key.