Secret latch

Abstract

A second latch for use on a door has the customary bolt retractable by turning an inner knob which is always free to rotate, and also by turning an outer knob when such outer knob is freed for rotation by the momentary axial depression by thumb pressure of a pin tumbler lock cyclinder located in the outer knob. When greater security is desired a push button in the inner knob can be moved to a hold position to prevent axial depression of the lock cylinder thereby preventing the release of the outer knob for rotation. The lock cylinder may be rotated at all times by a proper key in the customary manner for retracting the bolt.

Description

In buildings and the like there are various instances in which security requirements vary from time to time. Sometimes an ordinary amount of security is required but at other times less security and easier access is helpful. Also, there are instances in which ordinary security should be maintained with respect to one type of user, whereas lesser security is more convenient and satisfactory for other types of users. For example, a large, private workroom having a door onto a public hall is provided with the normal amount of security in off business hours in that an access door between the room and the hall is secured with the customary, key operated knob lock. During business hours, for example, the same degree of security must be maintained as to members of the general public utilizing the hall. But clerks or others having normal access to the room can be afforded easier access going into the room from the hall, so that their work is not impeded. While each clerk can be given his own key, this is cumbersome and bothersome. There is a requirement for easier access from the hall into the room by privileged users, such as clerks and the like, but not for the general public.

It is therefore an object of the invention to provide a secret latch which can be utilized to afford normal keyed security to the door on which it is installed, but which can be more readily operated without a key by those having appropriate information.

Another object of the invention is to provide a secret latch that can readily be incorporated, with very few structural changes, in a lock set of customary construction.

Another object of the invention is to provide a secret latch that can be easily shifted from its maximum security condition to an intermediate security condition.

Another object of the invention is to provide a lock mechanism that has special characteristics but does not differ in appearance, when installed, from a standard lock mechanism.

A further object of the invention is to provide a secret latch of generally improved construction and having attributes not normally available in customary latch sets.

A further object of the invention is in general to provide an improved latch or lock mechanism.

Other objects, together with the foregoing, are attained in the embodiments of the invention described in the accompanying description and illustrated in the accompanying drawings, in which:

FIG. 1 is a cross-section on a generally horizontal plane through the axis of one form of secret latch constructed pursuant to the invention and shown mounted on a door panel cooperating with a door frame, some parts being omitted for clarity;

FIG. 2 is a cross-section, the plane of which is indicated by the line 2--2 of FIG. 1;

FIG. 3 is a cross-section, the plane of which is indicated by the line 3--3 of FIG. 2;

FIG. 4 is a side elevation of a fragment of the secret latch mechanism of FIG. 1;

FIG. 5 is an isometric perspective of a generalized form of secret latch, most of the parts being disclosed in diagrammatic form;

FIG. 6 is a view comparable to FIG. 1, with a portion broken away, showing a modified form of interior construction;

FIG. 7 is a detail in elevation, the plane of view being indicated by the line 7--7 of FIG. 6;

FIG. 8 is a view comparable to FIG. 1, but showing a further modified form of device, portions being broken away to disclose a modified interior construction;

FIG. 9 is a cross-section, the plane of which is indicated by the line 9--9 of FIG. 8;

FIG. 10 is a cross-section, the plane of which is indicated by the line 10--10 of FIG. 8;

FIG. 11 is a view comparable to FIG. 1 but showing a still further modified form of the invention, portions being broken away to disclose a modified interior arrangement;

FIG. 12 is a cross-section, the plane of which is indicated by the line 12--12 of FIG. 11;

FIG. 13 is a cross-section, the plane of which is indicated by the line 13--13 of FIG. 11;

FIG. 14 is an interior elevation, the plane of which is indicated by the line 14--14 of FIG. 11;

FIG. 15 is a cross-section, the plane of which is indicated by the line 15--15 of FIG. 11;

FIG. 16 is a view comparable to FIG. 1 but showing an even further modified form of the device, portions being broken away to disclose the particular interior construction;

FIG. 17 is a detail in plan and cross-section, the general plane of the figure being indicated by the line 17--17 of FIG. 16;

FIG. 18 is a cross-section, the plane of which is indicated by the line 18--18 of FIG. 17.

In a typical environment; for example, between a public hallway or passageway and an interior workroom, such as a file room or clerk room, there is provided a door frame 6 of the customary kind, including a strike box 7 and a strike plate 8. Cooperating with the door frame is a door panel 9 adapted to swing about a hinge axis spaced from the plate 8. The panel 9 includes an edge bore 11 in which the customary or any standard, cylindrical bolt or latch mechanism 12 is disposed for reciprocation. Intersecting the bore 11 and extending through the door panel between the exterior and the interior is a cross bore 13. The panel arbitrarily divides the space so that the side 14 is referred to as the inside or interior, whereas the side 16 is referred to as the exterior or outside.

Mounted in the bore 13 and interconnected in the customary way with the latch mechanism 11 is the housing 17 of a lock or latch unit. A representative device of this general sort is shown in Pat. No. 2,834,194, issued May 13, 1958, to E. L. Schlage et al. and assigned to the assignee of this application, and is also found in numerous residential and commercial installations throughout this country. The housing 17 has an appropriate hub 18 on the interior side surrounded by a decorative escutcheon 19 and serving as a bearing mount for rotation of an inner spindle 21 about a through axis 22. The spindle 21 carries an inner knob 23 rotatable therewith about the axis. Operation of the knob 23 is effective through the spindle 21 to actuate a rollback mechanism 24 to withdraw the latch bolt 12 to an inactive position releasing the otherwise retained door panel from the door frame in the customary fashion.

In a similar fashion, the housing 17 includes a frame plate 26 having a hub 27 within which an outer spindle 28, unless restrained, is rotatable about the axis 22. A knob 29 on the outer spindle is disposed next to an escutcheon 30 and, if free to rotate, is effective through the spindle upon the roll-back mechanism 24, so that the latch member 12 can be retracted from the exterior side as well as from the interior side, both knobs working independently but being effective for the same purpose.

There is a control governed from the interior for normally holding the exterior knob 29 immovable with respect to the frame or housing 17, so that, in effect, the door is exteriorly locked. Conveniently nested within the knob 23 is an interior button 31 that is in general movable along the axis 22 and is normally spring urged into an outermost or right-hand position, as seen in FIG. 1. The arrangement for this includes a shell 32 disposed within the spindle 21 and containing a spring 33 pressing against the outermost part of the button 31. Carried by the button (FIGS. 3 and 4) is an extending lug 34 movable within a cut-out 36 in the wall of the spindle 21. The cut-out preferably has an inclined face 37 (FIG. 4) and a re-entrant notch 38. A user can depress the button 31 toward the left in FIG. 1, compressing the spring 33 and moving the lug 34 along the cut-out to an extreme left-hand position, whereupon the user can turn the button 31 about the axis 22 and let go the button so that the spring urges the lug 34 into the recess 38 to hold the button in its inner location axially abutting the shell 32. The button can be released by a slight inward pressure to remove the lug 34 from the notch 38 and then can be rotated counterclockwise so that the spring restores the button and the lug to its initial position.

The position of the button is effective to permit or to prevent axial translation of a locking bar 41 partly housed within the knob 23 and partly housed within the housing 17 and extending along the axis 22. The locking bar 41 interengages with the end of the shell 32 against relative axial motion and for relative rotation therebetween. The locking bar has an offset 42 terminating in a pair of lugs 43 and 44. One of the lugs 43 is axially translatable in a slot 46 formed in one end of the hub 27 included in the housing 17, so that the locking bar 41 is non-rotatable with respect to the stationary hub. The other lug 44 is movable between a lock position (as shown in FIG. 1) in which the lug 44 enters into and engages the sides of a slot 47 formed in the otherwise rotatable outer spindle 28. In this position of the parts, as continually urged by the wire spring 33, the locking bar interengages with the stationary housing and the otherwise rotatable spindle to preclude rotation of the spindle. The exterior knob 29 is thus normally held against rotation, so that the outer knob is ineffective to withdraw the latch bolt 12. If the locking bar 41 is in some fashion translated toward the right in FIG. 1 so that the lug 44 is removed from the spindle slot 47, the spindle is freely rotatable and the lock bolt or latch can be withdrawn by the outer knob. Thus, whether the outer knob is locked or is free depends upon the axial position of the locking bar.

In accordance with the invention, unlocking movement of the locking bar can be accomplished from the exterior by appropriately operating a pin tumbler lock mechanism 51 housed within the outer knob and spindle. The spindle 28 has a slot 52 receiving the tongue or flag 53 of a pin tumbler lock body 54 of the customary sort. Within the body 54 and rotatable about the axis 22 is the customary lock plug 56 designed to receive a proper key 57. Upon insertion of the key various tumbler pins 58 are arranged within the lock mechanism, so that the plug 56 can be rotated. Plug rotation is accompanied by rotation of a relatively flat driver bar 59. The driver bar engages an actuating mechanism 61 also engaging a tube 62 effective upon rotation to withdraw the latch bolt 12 in the customary way. Thus, when a proper key 57 is rotated, although the outer knob 29 is held stationary, the latch bolt 12 is withdrawn by key and entry can be had through the doorway, as is customary. As so far described, the general operation of this lock or latch set is substantially standard.

Pursuant to the present invention, however, an additional function is afforded. The notch 52 is the outer spindle 28 is made axially somewhat deeper than usual, so that although the pin tumbler lock body 54 is well confined in the rotary sense, it is not confined in the axial sense. Inward pressure upon the outer end of the rotary plug 56 or upon the housing 54, or both, is effective to translate the combined plug and housing toward the right in FIG. 1. Although the driver bar 59 is axially slidable within the fitting 61 and can impart rotation thereto in any axial position, the driver bar 59 is made somewhat longer than usual in order to press upon a cup 63 concentric with the axis and itself bearing upon a spacer 64 engaged with a third lug 66 on the locking bar 41. Thus, when pressure (with or without a key 57) is exerted toward the right on the body 54 and the plug 56, the driver bar 59 is similarly translated and comparably translates the cup 63, the spacer 64 and the locking bar 41 to the right against the force of the spring 33. The amount of translation is sufficient to withdraw the lug 44 from the slot in the outer spindle 28, thus releasing the knob 29 for rotation. Thereupon the user can rotate the knob and can withdraw the latch bolt 12 from its locked position to its unlocked position without rotation of any key 57. When the knob is released, all parts are spring returned to the original locked position.

With this mechanism a user on the interior side 14 can depress the button 31 and can turn the button to hold it in location so that the locking bar 41 is axially completely non-movable, the knob 29 is held and the latch 12 cannot be withdrawn by the exterior knob. Furthermore, under these conditions the insertion of a proper key 57, although effective to rotate the locking mechanism 51 and in that fashion to withdraw the latch bolt 12, cannot translate the driver bar 59 nor the locking bar 41 since the depressed and held button 31 acts as an axial stop and the outer knob 29 remains immobile. On the other hand, when the button 31 is released from the interior allowing lost motion between the shell 32 and the button itself, then anyone knowing of the extra capability of the lock body and plug, even without a key, can depress the plug 56 and the locking mechanism thus releasing the outer knob 29 for rotation, and by that means can withdraw the latch bolt 12 to gain access through the door to the interior. In this way there is provided an arrangement which, when the interior button 31 is depressed, affords normal security to the lock set; that is, the outer knob 29 is immobile but use of a proper key 57 will afford access to the interior. On the other hand, when the interior button 31 is released into its position as shown in FIG. 1, then a lesser degree of security is afforded in that anyone, having knowledge, can depress the plug 56 by thumb pressure, can rotate the knob 29 to withdraw the latch bolt 12 and so can gain access to the interior. The external appearance is standard and unchanged, so inspection of the lock set does not indicate its extra or "secret" capability.

In a representative instance, the button 31 can be left in its innermost "hold" or locked position for the night, for example. The only access from the exterior to the interior is then by means of a proper key 57. During working hours, however, if the button 31 is released, as shown, then anyone having appropriate knowledge of the lock can by depressing the plug 56 gain access without the usual key. Those with keys can always gain access, and those without keys can gain access provided the interior button 31 is released and they have the information that, unlike usual practice, the lock body and plug are not only rotatable, but are depressible or axially translatable. The casual public does not have this information and since the lock set looks exactly the same from the exterior as other sets always requiring the use of a key for access, there is an opportunity to exclude the unknowing general public from the area, but to make easy ingress for those having adequate information to depress the key actuated mechanism.

This general type of operation is shown for explanatory purposes in diagrammatic form in FIG. 5. The latch bolt 72 is connected to a slide 73 movable with respect to the main frame 74. An interior knob 76 carries a lug 77 forming part of the knob spindle 78 so that upon rotation of the knob 76, in at least one direction, the slide 73 is moved toward the right in FIG. 5 and the latch bolt 72 is withdrawn. In a similar fashion, there is provided an exterior knob 81 having a spindle 82 provided with a lug 83 bearing against the rear wall 84 of the slide 73, and effective when rotated, at least in one direction, also to withdraw the latch bolt 72. The latch bolt is restored by a spring 85 interposed between the wall 84 and the main frame 74. There is a key mechanism 87 of the pin tumbler type having a lock body 88 disposed in the spindle 82 with the body flag 89 movable axially in a longitudinal slot 91 in the spindle. Within the body 89 is a relatively rotatable lock plug 92 operable by a proper key 93. Rotation of the plug within the body is effective to rotate a locking bar 94 to rotate a lug 96 bearing against the wall 84 and so withdraw the latch bolt.

Projecting from the inner knob 76 is a manually operable button 97 pressed outwardly by a spring 98 and having a lug 99 movable into a notch 101, so that the button 97 can be retained in its hold or depressed position. The spring 98 is effective normally to move a shell 102 and a locking bar 103 to the left in FIG. 5. A lug 104 on the locking bar is slidable in engagement with a notch 106 in the frame 74, while a lug 107 on the locking bar engages a notch 108 in the spindle 82. The outer knob 81 is thus kept from rotating under all normal circumstances. Even without the use of the key 93, pressure from the exterior toward the right along the axis of the mechanism is effective to translate the lock body 88, as well as the plug 92, within the remaining length of the slot 91, so that the driver bar 94 moves the locking bar 103 to the right. This withdraws at least one of the lugs, such as 107, from the notch 108 and translates the shell 102 and compresses the spring 98. The knob 81 is so released for exterior rotation and the latch bolt 72 can be withdrawn thereby. However, when the button 97 is moved to its hold position and the lug 99 is moved into the notch 101, axial pressure by the driver bar 94 is ineffective to translate the locking bar 103 so that the outer knob remains fixed and held against rotation and withdrawal of the latch 72.

The arrangement of FIG. 6 is substantially the same in general as previously described, but some of the details are different. In this instance the flat locking bar 111 has a shoulder 112 against which a spring 113 abuts through the intermediary of a washer 114. The spring at the other end abuts a lug plate 116 mounted on a plug 118 against which abuts a driver bar 119 controlled by a locking mechanism 121 disposed in the outer knob 122 and of the same type as previously described. In the normal location of the parts as shown in FIG. 6, for example, the lug plate 116 and the plug 118 are positioned by the spring 113 so that a radially extending lug 123 on the lug plate resides in both a slot 124 in the main housing 126 and also in a notch 127 in the end of the spindle 128 of the outer knob. This locks the outer knob 122 against rotation. If, however, the locking mechanism 121 is translated toward the right in the figure, the driver bar 119 moves the plug 118 and the lug plate 116 to the right so that the lug 123 disengages from the notch 127 and compresses the spring 113. This movement takes up most of the space available so the plug 118 resides eventually against a shoulder 129 near the end of the locking bar 111. In this position of the parts the knob 122 is released for customary rotation and withdrawal of the latch bolt. A key 131 for the locking mechanism 121 is effective as usual to operate the latch bolt under any circumstances.

Upon occasion, it is desired to prevent the translation of the lock mechanism 121 to prevent freeing the outer knob 122 for rotation. When that is the case, a button 132 within an inner knob 133 is depressed to its hold position. This is accomplished by a rotary connection 134 between the button 132 and the locking bar 111 and by a lug 136 on the button operating in a cam notch 137 in a fixed sleeve 138. A flat 139 at the end of the notch 137 holds the button 132 when it is pressed in and turned. Depression of the button translates the locking bar 111 to the left so that the shoulder 129 thereon abuts against the end of the plug 118 compressing the spring 113 and precluding translation of the lug 123 out of the slot 124. By the turning and locking mechanism, the interior button 132 can be kept in a hold position thus securing the outer knob 122 against rotation and preventing depression of the locking mechanism 121.

As a further variation, there is shown a mechanism in FIGS. 8, 9 and 10 comparable to the mechanism shown in FIG. 1, but with a different lost motion and spring arrangement. In this instance the parts not described in detail are substantially the same as in connection with FIG. 1. In this instance the locking bar is made in two portions. There is an interior locking bar 151 having lugs 43 and 44 exactly as in FIG. 1 and terminating in a portion 152 overlapping the forward portion 153 of an exterior locking bar 154 extending into the interior knob 156. The overlapping portions of the locking bars are aligned by through pins 157 and 158 disposed in appropriate slots 159 and 161. There are washers 162 and 163 that abut the pins 157 and 158 and also abut the ends of an interposed spring 164 so that a resilient lost motion is afforded. The exterior locking bar 154 carries a head 166 rotatably connected to a button 167 axially translatable and rotatable with respect to the adjacent interior spindle 168 to which the knob 156 is attached. A lug 169 on the button 167 operates within an irregular notch 171 formed in the spindle 168.

Normally with the button 167 projected against the knob as a stop, as shown in FIG. 8, the spring 164 urges the interior locking bar 151 into its exterior knob blocking position. The spring also forces the exterior locking bar 154 to the right, thus moving the button 167 to the right. A rim 172 on the button lodges against an inturned portion 173 of the knob 156. When a locking mechanism 174 in the outer knob 176 is translated to the right in FIG. 8, it also moves a driver bar 177 to the right, thus displacing the interior locking bar 151 into knob release position. When pressure on the locking mechanism 174 is released, the spring 164 expands and forces the interior locking bar 151 to the left and back into its notch position holding the exterior knob 176 against rotation. When this position is to be maintained, the interior button 167 is translated to the left, in FIG. 8, and is rotated so that the lug 169 moves into an axially confining, offset, flat portion of the notch 171 and translates the exterior locking bar 154 to the left. This brings the pin 158 to the left end of its notch 161 and brings the right end of the notch 159 against the pin 157. This, then, holds the interlocking bar 151 against translation to the right, so that the knob 176 cannot be released.

In the modified form of device shown in FIGS. 11 to 15, inclusive, an arrangement generally similar to those preceding is furnished, but there is a difference in the operation of the interior push button. The push button, instead of being depressed in order to maintain the outer knob in its nonrotatable position, is, in effect, moved from a normal rotated position to a special hold rotated position.

In this arrangement a locking bar 181 is provided with a securing washer 182 positioning an abutting washer 183 having a radial split therein and serving as a stop for one end of a suitable spring 184. The other end of the spring 184 bears against a slotted backing washer 186, in turn resting against the customarily provided, transverse slide 187. A spring 188 in the interior spindle 189 projects the slide 187 to engage the inner knob 191 with the spindle. When the slide 187 is moved inwardly by an appropriate tool the knob 191 is released from the spindle, but in the position shown the knob is held axially in position and for rotation with the spindle.

The innermost end of the locking bar 181 is pivotally connected to a button housing 192 having a lug 193 (FIGS. 14 and 15) operating in a spindle slot having a circumferential portion 194 and having an axial merging portion 196 open to the end rim 197 of the interior spindle.

For normal locking, the button 192 is disposed with the lug 193 at the top (FIG. 14) end of the slot 194. Under these conditions translation of the locking bar 181 is prevented by interengagement of the lug 193 with the inner wall of the circumferential slot 194. The button 192 has a diametral extension 201, so the button can be turned to position the lug 193 at either end of the slot 194. In both instances the lug 193 serves as a stop against further translation of the locking bar 181 to the left.

When the outer knob 198 is to be freed for rotation, a locking mechanism 202, of the sort previously described, can be axially moved toward the right to displace the entire structure connected to the locking bar 181 to the right but only provided the button 192 is positioned so that the lug 193 can freely traverse the axial portion 196 of the slot. Unlocking depression of the mechanism 202 can be noted from the interior by watching axial movement of the button 192. There is a detent cam 203 utilizing force of the spring 184 to urge the button into either extreme rotated position. By proper rotation of the normally depressed button 192 the locking bar 181 can be held in its unlocked condition or can be held in its locked or hold condition.

In a still further modification of the fundamental arrangement, as shown in FIG. 16, the mechanism is somewhat like that shown in FIGS. 8 to 10, inclusive. In this version, there is disclosed an arrangement in which, although interrelated, the locking and unlocking of the exterior knob is independent of the inward movement of the cylinder lock mechanism.

In this arrangement, the exterior pin tumbler cylinder mechanism 206 can be rotated, as usual, to withdraw the latch bolt by means of a key, but also can be translated axially, as before, and when so translated causes the driver bar 207 to release one of a pair of locking bars 208 and 209 from their engagement with a relatively wide slot 211 (FIG. 17) in the exterior spindle 212. The two locking bars are similar in construction and are fastened together in a limited sense for some guidance, but in most other respects are independent. The locking bar 208, for example, carries a pin 213 extending into an elongated slot 214 in the other locking bar 209. Furthermore, the locking bar 208 has a C-shaped end portion 216 riding on the top and bottom of the locking bar 209. The C-shaped end portion 216 abuts a notched washer 217 riding upon the locking bar 209 and abutting one end of a coil spring 218. The other end of the spring 218 abuts a washer 219 resting against a turnable button 221 mounted within the central opening of the inner knob 222. The button 221 has the customary lug designed to operate in a slot 223 in the interior spindle 224, as previously described.

In the operation of this structure when the lock mechanism 206 is translated toward the right it engages and similarly translates the locking bar 208 toward the right. This is against the urgency of the spring 218 because the portion 216 displaces the washer 217. At the same time, because of the interconnection of the pin 213 and the slot 214, both of the locking bars 208 and 209 are translated far enough so that neither interengages between the lock frame and the outer spindle, thus releasing the exterior knob.

When it is desired to maintain the outer knob against rotation, then the button 221 is translated toward the left in FIG. 16 and is turned so as to be held in its left-most position. That compresses the spring 218 and simultaneously moves the locking bar 209 to the left enough to cause interengagement of the left-hand end thereof in the wide slot 211 in the exterior spindle 212. In this way the locking bar 209 is held in restraining position by the depressed button 221. Should one then attempt to translate the locking mechanism 206 to the right, the attempt must fail because the pin 213 is then in the right-hand end of the slot 214 and cannot move the locking bar 209 because of the secure position of the button 221. The only way then to withdraw the locking bar 209 from its interengagement with the slot 211 is by rotating the interior button 221 and permitting the spring 218 to move it into its FIG. 17, projected position.

Claims

What is claimed is:

1. A secret latch comprising a lock frame adapted to be mounted on a door, a bolt mounted on said frame for movement between a locking position and an unlocking position, a knob, means for mounting said knob for rotation on said lock frame, means for moving said bolt out of said locking position upon rotation of said knob, a key mechanism, means for mounting said key mechanism for rotation and for axial movement relative to said lock frame, means for moving said bolt out of said locking position upon rotation of said key mechanism, means for coupling said knob to said lock frame for precluding rotation of said knob relative to said lock frame, and means operable upon translation of said key mechanism for uncoupling said knob from said lock frame.

2. A device as in claim 1 in which said knob is an outer knob and said key mechanism is disposed within said outer knob.

3. A device as in claim 1 including an inner knob and in which said coupling means is a control disposed within said inner knob.

4. A device as in claim 1 including means for preventing axial movement of said key mechanism.

5. A device as in claim 4 including an inner knob and in which said preventing means is disposed within said inner knob.

6. A device as in claim 5 in which said preventing means includes an axially movable button movable between a preventing position and a releasing position, means for urging said button toward said releasing position, and means for holding said button in said preventing position.

7. A secret latch including the subcombination of a retractable bolt, a lock cylinder body, means for supporting said lock cylinder body for translation along an axis out of an extreme position, a lock cylinder plug mounted for rotation about said axis in said lock cylinder body, a knob rotatable about said axis, means for connecting said lock cylinder body to enable said knob to retract said bolt upon translation of said lock cylinder body along said axis, and means for connecting said lock cylinder plug to retract said bolt upon rotation of said lock cylinder plug around said axis.

8. A device as in claim 7 including means for resiliently urging said lock cylinder body toward said extreme position.

9. A secret latch including the subcombination of a lock frame, a bolt retractable on said frame, a bolt operator, a lock cylinder body, means for mounting said lock cylinder body on said frame for reciprocation, a lock cylinder plug, means for mounting said lock cylinder plug in said lock cylinder body for rotation relative to said lock cylinder body, means for enabling said operator to retract said bolt by reciprocation of said lock cylinder body relative to said frame, and means for retracting said bolt by rotation of said lock cylinder plug relative to said frame.

10. A device as in claim 9 in which said means for retracting said bolt by rotation of said lock cylinder plug includes an axially movable slip joint.

11. A secret latch comprising a lock frame adapted to be mounted on a door, a bolt mounted on said lock frame for movement between a locking position and an unlocking position, an outer knob, means for mounting said outer knob for rotation relative to said lock frame, means for interconnecting said outer knob and said bolt for moving said bolt from said locking position to said unlocking position upon rotation of said outer knob, an inner knob, means for mounting said inner knob for rotation relative to said lock frame, means for interconnecting said inner knob and said bolt for moving said bolt from said locking position to said unlocking position upon rotation of said inner knob, a button, means for mounting said button for axial movement in said inner knob between an out position and an in position, means controlled by said button for holding said outer knob against rotation when said button is in said in position and for releasing said outer knob when said button is in said out position, a lock cylinder body, means for mounting said lock cylinder body for axial movement in said outer knob, means interconnecting said lock cylinder body and said means controlled by said button for moving said button into said out position, a lock cylinder plug, means for mounting said lock cylinder plug for rotation in said lock cylinder body, and means controlled by said rotation of said lock cylinder plug for moving said bolt from said locking position into said unlocking position.

12. A device as in claim 11 including a lost-motion connection between said lock cylinder body and said means controlled by said button.

13. A device as in claim 11 including means for holding said button in said in position.

14. A device as in claim 11 in which said means controlled by said rotation of said lock cylinder plug for moving said bolt is independent of said means for interconnecting said outer knob and said bolt.

15. A secret latch comprising a lock frame, a bolt movably mounted on said frame, a spindle movably mounted on said frame, means for connecting said spindle to move said bolt, a handle, means for connecting said handle to move said spindle, means for holding said spindle against movement on said frame, and means accessible to the thumb of a user grasping said handle for disabling said holding means, said accessible means including at least in part a rotatable key-actuated means for moving said bolt.

16. A secret latch comprising a lock frame, a bolt mounted on said frame for projection and retraction, a spindle rotatably mounted on said frame, means for connecting said spindle when rotated to retract said bolt, a handle having an opening, means for mounting said handle on said spindle for rotation therewith and with said opening in alignment with said spindle, means for holding said spindle against rotation on said frame, a plunger mounted on said spindle and accessible through said opening, means for connecting said plunger to disable said holding means, and means included at least in part in said plunger and operable by a key for moving said bolt.

17. A secret latch comprising a lock frame, a bolt mounted on said frame for projection and retraction, a spindle rotatably mounted on said frame and projecting therefrom along an axis, means for connecting said spindle when rotated about said axis to retract said bolt, means for holding said spindle against rotation on said frame, a pin tumbler mechanism including a body and a plug key-rotatable in said body, means for mounting said pin tumbler mechanism on said spindle for movement along said axis, means operated by axial movement of said pin tumbler mechanism for disabling said holding means, and means operated by rotation of said plug in said body for retracting said bolt.

18. A secret latch for a lock having a latch bolt retractable by rotation of a knob and retractable by key-rotation of a key plug in a body disposed within said knob and having means for holding said knob against rotation comprising means operated by depression of said key plug and said body relative to said knob for disabling said holding means.