US2920473A - Combination lock - Google Patents

Description

, Jan. 12, 1960 HANSEN 2,920,473

COMBINATION LOCK Filed April 15, 1957 5 Sheets-Sheet l Jan. 12, 1960 E. H. HANSEN COMBINATION LOCK 5 Sheets-Sheet 2 Filed April 15, 1957 7%) I ward HHansen y v 27%? Jmdmv Jan. 12, 1960 E. H. HANSEN 2,920,473

COMBINATION LOCK Filed April 15, 1957 SSheets-Sheet 3 Jan. 12, 1960 Filed April 15, 1957 E. H. HANSEN 2,920,473

COMBINATION LOCK SSheets-Sheet 4 Edwargd Hansen I 3% Qa Q Jan. 12, 1960 HANSEN 2,920,473

COMBINATION LOCK Filed April 15, 1957 5 Sheets-Sheet 5 United StatesPatent O COMBINATION LOCK Edward H. Hansen, Elkhart, Ind.

Application April 15, 1957, Serial No. 652,770

4 Claims. (Cl. 70-498) This invention relates to combination locks and has as its principal object the provision of a combination lock for doors and the like wherein actuation of a movable dial-like operator through a predetermined sequence of motions which entails both rotary and axial sliding movement of the operator effects unlocking of a rotatable actuator to free the same for rotation from latching to unlatching positions.

In general it is an object of this invention to provide a combination type door lock having a movable indicia carrying dial mounted coaxially with a door knob and which is adapted to be moved through a predetermined sequence of motions to effect unlocking of a mechanism by which latch bolt retracting rotation of the door knob is normally prevented, and wherein incorrect manipulation of the dial efiects more secure locking of the mechawhich is simple and rugged, and thus capable of resisting attempts to defeat it by the application of force and wherein thecombination or sequence of movements by.

which the mechanism can be unlocked may be readily changed.

It is also an object of this invention to provide a combination lock of the character described which is,

simple and inexpensive to manufacture, particularly inasmuch as the several tumblers comprising a part ofthe lock mechanism may be made identical with one. another.

A further object of this invention resides in the provision of a combination lock of the character described wherein both the dial and resetting mechanism for the lock tumblers are disposed coaxially of an actuating shaft upon which the door knob is mounted.

Still another object of this invention resides in the provision of a lock mechanism of the character described wherein the elements of the lock mechanism are so shaped and combined as to inherently provide good protection against the entry of moisture into the movable parts of the lock mechanism to thus render the device well adapted for installation on outside doors and in similar exposed locations.

With the above and other objects in view, which will.

appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made 2,920,413 Patented Jan. 12, 1 960 ice Figure 1 is a view of a door with the lock of this invention installed thereon, the door being shown in horizontal section and the lock in elevation and in unlocked condition;

Figure 2 is a sectional view taken on the line 2-2 in Figure 1;

Figure 3 is a view similar to Figure 2, on an enlarged scale, with the lock mechanism shown in locked condition;

Figure 4 is a fragmentary elevational view of the tumbler mechanism of .the lock of this invention, showing the same in its unlocked condition;

Figure 5 is a view similar to Figure 4 but showing the tumbler mechanism in its normal locked condition;

Figure '6 is a view similar to Figure 5 but showing the tumbler mechanism in a more securely locked condition with certain of the tumblers in positions to which the plane of they have been moved byinco'rrect manipulation of the dial, as would be the case when the device is tamperedwith by a person not having knowledge of the correct combination; I

Figures 4a, 5a, and 6a are sectional views taken on the correspondingly numbered lines in Figures 4, 5 and 6 respectively;

Figure .7 is a partially disassembled perspective view, of the lock mechanism of this invention; and

Figure 8 is a disassembled perspective view of the tumbler carriers,.tumbler assembly and actuator of the lock mechanism of this invention.

Referring now more particularly to the accompanying drawings, inwhich like numerals designate like parts throughout the several views, the numeral 5 designates generally a door, such as the outside door of a house, having a large bore 6 therethrough near its upright free edge 5, in which is housed a lock mechanism 7 embodying this invention. A latch bolt 9 is axially slidably mounted in a lateral bore 8 in the door communicating with the bore 6 and opening to its free edge 5', and the latch bolt is engageable ina recess defining a keeper 10 in the door frame 11.

The latch bolt may be retracted to free the door for opening by rotation of either of a pair of knobsv 19 and.

20, accessible at the outer and inner sides of the door, respectively. The, latch bolt is notched along its outer and inner sides, as at 13 and 14, to provide shoulders facing toward the free edge 5 of the door and against which outer and inner downwardly projecting bolt re.- tracting levers 17 and 18, respectively, are engageable.

The knobs 19 and 20 are respectively secured to separate. but coaxial actuator shafts 22 and 23 and the bolt retract-T ing levers 17 and 18 are also respectively secured to these shafts so that rotation of either knob in the proper direction will swing the bolt retracting lever connected therewith to retract the latch bolt from its keeper and permit opening of the door. the latch bolt is substantially longer than the notch 14, and hence the latch bolt may always be retracted by means of the inner knob 20, even tho-ugh the bolt retract ing lever 17 which is connected with the outer knob 19; is confined against motion, as when the lock mechanism mechanism comprises, in general, a body consisting of a barrel or. outer housing member 26 by which the outwardly opening mouth of the bore 6 in the door is closed,

front and rear tumbler carriers 28 and 29-, respectively, which house a number of shiftable elongated tumblers 30, and front and rear . toothed discs 31 and 32, respec tively, both non-rotatably secured to the actuator shaft 22 to which the outer knob 19 is attached. The mechanism" also includes a movable operator or dial 34 which is However, the notch 13 inadapted to be manipulated through the unlocking combination or sequence, and a tumbler resetting device 35 by which the tumblers may be moved from rearwardly actuated toforward positions at which the mechanism is in a normal lockedcondition As best seen in Figures 3 and 8, the barrel portion2 6 of the lock body comprises a cup-shaped shell having a cylindrical side wall with an external flange 37 thereon intermediate its ends to provide for securement of the lock bodyto the outer or frontfac'e of the door and to provide an escutcheon by which the bore 6 through the door is closed and trimnted. Screws 38 pass through the door from the rear or inner face thereof, into rearwardly opening threaded wells 39 in the flange 37, so as. to secure the lock body tothe door in a manner which virtually nullifies the possibility of its. being removed from thefouter side of the door but enables it to be readily reniov ed'by a person working fror n the'inside of the door.

The bottom wall 4% of'the cup-shaped barrel is spaced a slight distance outwardly, of the adjacent face of the door, and has a central bore 41 therein which accomrnodates the actuator shaft, and has a plurality of smaller bores 42, equispac'ed circumferentially around acircle concentric with the shaft and through which the tumblers 3B are made accessible for rearward actuation, as hereinafter described. i

The front and rear tumbler carriers 28 and 29, respectively, are housed within the barrel of the lock body and are secured to one another and to the barrel, inside the cylindrical side wall of the latter, as by means of screws 44 and 45 (see Figures 7 and 8), so that these three members are held in unitary fixed relationship to one another and to the door in which the lock mechanism is mounted. The actuator shaft 22 is rotatably carried by the lock body for rotation coaxially with the cylindrical side wall of the barrel, and the shaft bearing is provided by coaxial bores 46 and 47 in the two tumbler carriers 28 and 29, respectively. The tumblers 30 are slidably carried by the lock body for endwise motion relative thereto along paths disposed lengthwise of the shaft 22, and for this purpose the carriers 28 and 29 are provided with a plurality of tumbler bores 50 and 50', respectively, coaxial with the small bores 42 in the front wall 40 of the barrel. These tumbler bores mount the tumblers 30 for axial sliding motion between forward positions wholly within the lock body and rearwardly actuated positions.

The rear toothed disc 32 is coaxially secured to the actuator shaft 22 for rotation therewith, and those tumble'rs which must be actuated rearwardly to free the door for opening cooperate with the disc 32, in a manner described hereinafter, to lock the shaft against rotation except when the dial has been manipulated through the proper sequence of motions. The disc 32 is accommodated in a shallow rearwardly opening well 51 in the rear of the outer tumbler carrier 28, the radius of which well is smaller than the distance from the carrier axis to the axes of the tumbler bores 50 but larger than that of a circle tangent to the inner surfaces of the tumbler bores, so that the well 51 partly breaks into all of the tumbler bores. The disc 32 is axially confined between the bottom of the well 51 and the adjacent front face of the rear tumbler carrier 29, and because the disc 32 is anchored to the actuator shaft 22, axial displacement of the latter is thus precluded, although it will be understood that there is sufiicient clearance between the opposite faces of the disc and the adjacent tumbler carrier surfaces to permit the disc and shaft to be freely rotatable. It will also be understood that the diameter of the rear disc is 'very slightly less than that of the well in which it is confined.

The disc 32 has a number of arcuate equispaced notches 53 in its periphery, one for each of the tumbler bores in the tumbler carriers, the radius of each notch being substantially equal to, or very slightly greater than, that of the tumbler bores. The axes of the notches 53, moreover, coincide with those of the tumbler bores when the actuator shaft is in its predetermined latching position shown, so that a tumbler in any one of the bores 50, may engage in one of the notches 53.

The tumblers 30 are identical, each having large diameter opposite ends 55 and 56 of unequal length slidably received in the tumbler bores in the carriers to serve as guide means for the ttunblers. The guidelike ends of the tumblers are defined by a circumferential groove 57 in the medial portion of the tumbler, which groove has an axial length slightly greater than the. thickness of the disc 32 and a depth sufficient to permit rotation of the disc 32 when all of the tumbler grooves align radially therewith.

In their forward positions, the tumblers are wholly received in the lock body with their rear ends flush with the rear face of the carrier 29, but they are shiftable in their bores to rearward positionsat which the inner portions of the tumblers project rearwardly from the rear tumbler carrier 29.

The longer end portion 55 of each tumbler has a circumferential groove therein in which is received a resilient O-ring 58, and that part of the long end of each tumbler which lies between the O-ring groove and the groove 57 constitutes the locking portionS l of the tumbler. The O-rings cooperate with the waits of the tumbler bores to frictionally restrainthetumblers against displacement out of any position to which they may be moved.

With the type of tumblers described, each tumbler at all times has one large diameterend portion engaged in the front tumbler carrier and its other large diameter end portion carried by the rear tumbler carrier. However, as may be seen best in Figures 4, 5 and 6, certain of the tumblers, designated 30", are normally disposec in the tumbler bores with their longer end portions 55 to the front, in the carrier 28, and with their locking portions 54 clearing the notches in the disc 32. In the locked condition of the mechanism, the remaining turnblers, designated 30', have their longer end portions rearmost, in the carrier 29 and have their locking portions 54 engaged in notches in the disc 32. These latter turnblers 30' are those which normally lock the mechanism and which must be moved from their forward to their rearward positions at which theirloc ki ng portions clear the notches in the disc 32 in order to effect unlocking of the mechanism and free theactuating shaft for rotation from latching to unlatching position. Although three of these tumblers 30 have beenshown comprising theonly combination of tumblers which, when shifted rearwardly, will unlock the mechanismflthe combination may consist of any desired number of such tumblers, and it may be easily changed at any time merely by an end-to-end reversal of tumblers.

Such rearward unlocking actuation of the tumblers 30 may be effectuated by means of the movable operator or dial 34, which is a shallow, cup-shaped member hav ing a cylindrical side wall and a bore 59 in its bottom wall 61 by which it ismounted on the actuatorv shaft 22 for rotation and for axial sliding movement between the front knob 19 and the lock body. The axially short cylindrical wall 60 of the dial projects rearwardly to closely but slidably embrace the front end portion of the barrel, and the bottom wall 61 of the dial overlies the front wall of the barrel so that the dial thus serves as a closure by which moisture andother foreign matter is prevented from entering the lock body from the front thereof and by which the mouths of the small bores :42 in the barrel are closed and the tumblers concealed. The cylindrical wall -60 of the dial is preferably pro vided .on its exterior with: suitable indicia' (such as the numbers shown in Figures 1 and -7), cooperable with reference mark 62 on the stationary cylindrical wall of the barrel, to define severalpredetermined positions of rotation of the dial at each of which a rearwardly projecting pin 63 fixed to'the inside of the dial wall 61 aligns with one of the bores 42, and consequently with one of the tumblers 30. For a purpose to be presently described, the diameter of the bores 42 is such as to snugly though slidably receive the pin 63.

Rearward movement of the tumblers is effected one at a time by means of the pin 63, as a consequence of rearward motion of the dial to project its pin 63 throughthe small bores 42 and into engagement with the forward ends of the tumblers. This, of course, first involves rotation of the dial to bring each of its indicia into alignment with the mark 62. The length and diameter of the pin 63 are such that as the dial is moved axially rearwardly a distance to bring its front wall 61 into fiatwise engagement with the front wall 40 of the barrel the pin may enter the bores 50 in the front tumbler carrier and engage the tumblers, pushing the tumblers from their forward to their rearward predetermined positions.

It will-now be seen that if the dial is rotated tobring it to each of the positions, in turn, at which itspin 63 is engageable with such of the tumblers as have their longer end portions 55 rearmost (which tumblers are designated 30), and the dial is moved rearwardly as far as it will go at each such position, all of the tum-- blers 30 will, in turn, be moved from their forward positions, in which their locking portions 54 are lockingly engaged in arcuate notches 53 in the rear disc 32, to their rearward positions, in which their circumferential grooves 57 align with the disc, permitting it to rotate. Ths latter unlocked condition of the mechanism is illustrated in Figures 4 and 4a. As stated previously, the unlocking combination may be readily changed merely by reversing the orientation of selected tumblers, turning them end for end.

A coiled compression spring 65' surrounding the actua'tor shaft 22 reacts between the wall 61 of the dial and the front sprocket-like disc 31 to yieldingly urge the dial forwardly and normally hold the pin 63 thereon out of the small bores 42 in the front wall of the barrel. The front knob 19, of course, prevents forward displacement of the dial off of the shaft 22, and the spring 65 normally holds the dial against the rear of said knob.

The front toothed disc 31 is generally similar to the rear disc 32 with respect to its diameter and arcuately notched periphery, and it, too, is constrained to rotate with the actuator shaft 22. Its notches 66, however, are of a size to substantially closely fit the pin 63 on the dial. Therefore, if torque is applied to the shaft 22, while inward pressure is exerted upon the dial to cause the pin 63 to pass through one of the bores 42 in the front wall of the barrel, the entry of the pin into the adjacent close fitting notch 66 of the front disc 31 will effectively preclude any possibility of picking the lock by feel. This follows from the fact that since both the rotational and the axial force being applied will be resisted by the friction resulting from the wedging of the pin 63 between the stationary front wall of the barrel (through which the bores 42 pass) and the disc 31, and this would make it impossible to feel any force applied to the tumbler being moved by the pin 63.

Stated in another way, the projection of the pin 63 through one of the bores 42 and into an adjacent notch 66 in the front disc 31 makes it impossible to press the side of the adjacent notch 53 in the rear disc 32 against the side of the actuated tumbler, as would be necessary to pick the lock by feel.

The front disc is constrained to rotate with the actu ator shaft 22, and for this purpose the disc has a hub portion 67 with rearwardly opening diametrical slots therein which receive a pair of tangs' 68 each secured in and projecting outwardly from the wall of the shaft. The tangs 68 may be provided by short pins, the inner ends of which terminate short of the rod 76 within the shaft 22, and assembly of the front disc to the shaft may be accomplished by axially sliding -the'disconto the shaft from its front before the tumbler carriers, with the shaft in place, are installed in the barrel. The front tumbler carrier 28 has a forwardly opening coaxial counterbore 70 therein which accommodates the hub portion of the front disc, and the front wall of the barrel has a shallow rearwardly opening counterbore 71 which accommodates the body of said disc, so that the front disc is confined against axial movement relative to the shaft 22 by the opposing faces on the barrel and the front tum-' bler carrier. The hub portion of the front disc also has a forwardly opening counterbore 72 in which the rear end portion of the compression spring 65 is guidingly confined, and the central bore 41 in the front wall of the barrel is large enough to clear this spring, Y

The tumbler resetting device 35 comprises a pusher by which all rearwardly actuated tumblers may be simultaneously shifted back to their forward positions. It

comprises a hub portion 75 having a coaxial bore therethrough whereby the pusher is axially slidably mounted on the front actuator shaft 22, and a flange 74 having a flat front face opposing and normally spaced from the rear of the tumbler carrier 29. The actuator shaft is tubular, and through its bore extends an axially slidable rod 76 by which the pusher may be actuated. The front end portion of the rod 76 projects forwardly through the knob 19 and terminates in a small knob 77, accessible in front of the knob 19 and by which the rod may be readily drawn forwardly. A cross-pin 78, extending through the hub portion of the pusher, through an axially:

elongated slot 79 in the actuator shaft, and through a small transverse bore in the rod 76, anchors the pusher to the rod to constrain the pusher to axial motion with the rod. p

Thus, when the small knob 77 is drawn forwardly the pusher is moved forwardly with it to carry its flange 74 flatwise against the rear face of the rear tumbler carrier 29, and any tumblers which had been actuated to their rear positions are returned to their forward positions wholly within the lock body, and in which positions the three tumblers 30' lock the actuating shaft against rotation out of its latching position. In other words, forward actuation of the small knob 77 to move the pusher forwardly, serves to' effect normal locking of the mechanism, moving the tumblers 30 from their positions shown in Figures 4 and 4a to their positions shown in Figures 5 and 5a.

The pusher is yieldingly held in a rearward inoperative position by means of a coiled compression spring surrounding the actuator shaft 22 and reacting between the rear tumbler carrier and the pusher. The end portions of said spring are received in counterbores 8t and 81 in the rear tumbler carrier and the hub portion of the pusher, respectively.

When the dial is actuated to an incorrect position, as might be the case when a person unfamiliar with the correct combination tampers with the mechanism, the engagement of the pin 63 thereon with one of the normally non-locking tumblers 30 will move such tumbler to its rearward position, interposing its locking portion 54 in one of the notches in the rear toothed disc 32, and such tumbler then cooperates with the tumblers 36' in more securely locking said disc and the actuating shaft against rotation. The condition which then obtains is illustrated in Figures 6 and 6a. Thus, even if the dial is subsequently manipulated through the correct combination, the lock will nevertheless remain in a securely locked condition. However, a person having knowledge of the combination who thereafter desires to unlock the mechanism need only draw the pusher 35 forwardly, by

pulling on the small knob 77, to return to their forward non-locking positions all of the tumblers 30" which have been thus displaced and to reset the mechanism in its normally locked condition, as seen in Figures 5 and 5a, before working the correct combination.

The rear actuator shaft 23, to which the rear knob 20 is anchored, is also tubular and is rotatably mounted in a rear flanged bearing .member 82, the flange of which closes the mouth of the bore 6 at the rear or inner side of the door. Axial displacement of the shaft 23 is prevented by engagement of the forward or hub end of the rear knob with the hub 83 of the bearing member 82, and by a collar 84 secured on the inner end portion of the shaft 23, which collar carries the rear bolt retracting lever 13. This collar is axially confined between the flange of the bearing member 82 and another collar 85 fixed on the adjacent rear end of the front shaft 22 and which other collar carries the frontcbolt retracting lever 1'7.

A rod 86 is axially slidably mountedin the bore in the rear actuator shaft 23 for actuation, of the pusher 35 and locking of the mechanism from the inside of the door. The rod 86 projects outwardly beyond the inner knob 2%, to be accessible for actuation, and terminates in at small knob 87 whichcfacilitates manipulation of the rod; and at its forward end the rod 86 abuts the rear end of the front rod 76, as at 88. A transverse pin 89 through the rear rod 86 prevents axial displacement thereof out of the rear actuator shaft.

From the foregoing description taken together with the accompanying drawings it will be readily apparent that this invention provides a combination lock in which unlocking of the lock mechanism can be accomplished only by a predetermined sequence of movements which includes both rotation of an indicia carrying dial and axial movement thereof, so that the complexity of operation of the lock will be increased to a person unfamiliar with its operation without unduly complicating it for persons familiar with it. It will also be seen that the lock of this invention is inherently simple and rugged in construction; that it is well adapted for installation on exterior doors and in other exposed locations because the movable parts of the lock mechanism are well protected against the entry of dirt and moisture; that the lock of this invention tends to provide increased locking security when tampered with by persons unfamiliar with the correct unlocking combination; that the unlocking combination or sequence may be readily changed when desired merely by reversal of one or more of the tumblers in their bores; and that the mechanism is relatively inexpensive, particularly because all of the tumblers may be made identical with one another.

What is claimed as my invention is:

1. In a lock mechanism of the type having an actuator shaft which is rotatable between latching and unlatching positions: a fixed front wall in which the actuator shaft is journalled with a forward end portion thereof accessibly projecting therefrom, said fixed front wall having a number of parallel bores therethrough tangent to and equispaced around a circle which is concentric to the actuator shaft axis; tumbler carrying means behind and fixed with respect to said front wall, said tumbler carrying means having an opening through which the actuator shaft passes and having a number of parallel bores therein equal to the number of bores in the fixed front wall and axially aligned therewith; an elongated tumbler endwise slidably mounted in each of said bores in the tumbler carrying means for motion between forward and rearward positions, each of said tumblers having axially adjacent locking and non-locking positions; a disc coaxially anchored to the actuator shaft for rotation therewith, said disc having notches in its periphery aligned with the bores in the tumbler carrying means when the actuator shaft is in its latching position; the locking portions of certain tumblers which occupy their forward positions being received in adjacent ones of said notches in the disc to prevent rotation of the actuator shaft to its unlatching position, and the locking portions of other tumblers which occupy their forward positions being disposed forwardly of said disc; all of the notchesin said disc being large enough to loosely receive the locking portions of their adjacent tumblers; an indicia carrying element mounted in front of said front wall for rotation about the shaft axis and for axial movement toward and from said front wall, said indicia carrying element having a rearwardly extending pin thereon adapted to be snugly. projected through any selected one of said bores in the front wall and to thereby depress the tumbler aligned with such selected bore to push the same from its forward to its rearward position so that upon proper selection of the tumblers so actuated the actuating shaft is freed for rotation to its unlatching position; and a second disc interposed between said front wall and the tumbler carrying means and fixed with respect to the shaft so as to turn therewith, said second .disc, having a circular row of openings to axially align with the bores in the front wall when the actuatorshaft is in its latching position of rotation, said openings in said second disc being of a size to snugly receive the rearwardly extending pin so that upon simultaneous application of torque on the actuator shaft and rearward axial pressure upon the indicia carrying element with the pin engaged in one of said openings, the friction caused by the resulting wedging of said pin between the front wall and said second disc constitutes the major resistance to such force and thus precludes picking the lock by feel.

2. In a combination lock of the type having an actuating shaft which is rotatable between latching and unlatching positions about a fixed axis, an indicia carrying element which is mounted for rotation about a'fixed axis and for back and forth axial motion toward andfrom a fixed member behind said element, and wherein axialdepression of said element in each of a plurality of predetermined angular positions thereof releases the shaft. for rotation to unlatching position, by effecting shifting of tumblers from operative positions at which they are engageable by parts fixed to the actuating shaft upon a slight degree of rotation of the shaft out of its latching position to block rotation of the shaft to its unlatching position: characterized by the provision of means for preventing such engagement between the tumblers and said shaft parts during manipulation of the lock, comprising cooperating means on the indicia carrying element and the fixed member behind it, adapted to be .brought into closely interfitting engagement as a consequence of initial depression of said element in :any angular tumbler shifting position thereof to establish an interlock between the element and said fixed member by which rotation of the indicia carrying element is precludedlas long as it is either partially or fully depressed, and cooperating means on the shaft and said indicia carrying element likewise adapted to be brought into closely interfitting.:engagement as a consequence of such axial depression of the indicia carrying element to interlock the shaft: to the element and hence to the fixed member so as to preclude such rotation of the shaft as would tend to effect engagement between the tumblers and said parts fixed to the shaft.

3. In a combination lock of the type having an actuating shaft which is rotatable between latching and unlatching positions about a fixed axis, an indicia carrying element which is mounted for. rotation about a fixed axis and for back and forth axial motion toward and from a fixed member behind said element, and wherein axial ;depression of said element in each of a plurality of. predetermined angular positions thereof releasesthe shaft for rotation to unlatching position, by effectingshifting of tumblers from operative positions at which they-are engageable by parts fixed to the actuating snaftwupon. a slight degree of rotation of the shaft out of its latching position to block rotation of the shaft to itsunlatch'ing position: characterized by the provision of means'for preventing such engagement between the. tumblers: and said shaft parts during manipulation of. the lock, comprising means operable upon axial depression of the indicia carrying element in any tumbler shifting position thereof, to establish an interlock between the shaft and said fixed member by which rotation of the shaft out of its latching position is limited to an amount less than said slight degree of rotation at which engagement between the tumblers and said shaft parts takes place.

4. In a combination lock of the type having an actuating shaft which is rotatable between latching and unlatching positions about a fixed axis, an indicia carrying element which is mounted for rotation about a fixed axis and for back and forth axial motion toward and from a fixed member behind said element, and wherein axial depression of said element in each of a plurality of predetermined angular positions thereof releases the shaft for rotation to unlatching position, by effecting shifting of tumblers from operative positions at which they are engageably by parts fixed to the actuating shaft upon a slight degree of rotation of the shaft out of its latching position to block rotation of the shaft to its unlatching position: characterized by the provision of means for 10 preventing such engagement between the tumblers and said shaft parts during manipulation of the lock, comprising abutment means on the shaft and on said fixed member, and abutment means on said indicia carrying element interposable between abutment means on the shaft and the fixed member upon axial depression of the indicia carrying element in any tumbler shifting position thereof to limit rotation of the shaft in the unlatching direction to an amount less than said slight degree of rotation at which engagement between the tumblers and said shaft parts takes place.

References Cited in the file of this patent UNITED STATES PATENTS 1,530,861 Standen Mar. 24, 1925 1,705,340 Robert Mar. 12, 1929 2,083,782 Grubb June 15, 1937 FOREIGN PATENTS 156,646 Australia May 21, 1954

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