Security lock box with removable key plug

A security lock box includes a receptacle having an access opening and a hinged door. A vertical door edge adjacent th hinge is provided with an edge return which engages an inwardly curved lip along the receptacle opening for preventing entry through removal of a hinge pin. The door additionally has flanges extending transversely along top and bottom edges. The flanges are adapted for cooperative interfitting within confronting guard recesses along the margin of the receptacle opening. A locking mechanism having a pair of selectively slidably locking bars is positioned within the access opening. The locking bars are extendable through slots within the door flanges for securing the door in a locked mode. The locking mechanism is activated by a cylinder lock mounted in the door. The cylinder lock includes a cylindrical housing for accommodating a removable key plug and operating key adapted for interchangeable applications within a plurality of similar lock cylinders. The key plug includes a tail member for engaging the locking mechanism and is further provided with a keeper element for retaining the key plug within the cylinder housing when the door is in a locked mode.

TECHNICAL FIELD 
This invention relates generally to theft prevention devices and especially 
to a repository for the safekeeping of valuables and other personal 
property. 
In particular, the device of this invention concerns a protective enclosure 
of tamper proof construction which is accessible through the application 
of a removable lock component. 
BACKGROUND ART 
The increasing awareness of the necessity for safeguarding unattended 
personal property and valuables prompted the development of various 
security systems. This became a matter of particular concern with regard 
to innkeepers and the management of other establishments which sought to 
protect their guests' property. An approach that gained noteworthy 
acceptance involved the utilization of personal key operated in-room 
strong boxes. The integrity of those protective measures in maintaining 
effective access control was substantially impaired. A serious deficiency 
was that previous guests or hotel employees could duplicate keys for later 
unauthorized re-entry into the depositories. 
In an attempt to overcome these shortcomings, wall safes were developed 
which contained a standardized removable door incorporating a lock 
cylinder such as those marketed under the trademark Telsafe and described 
in the pioneer U.S. Pat. Nos. 3,481,288 and 3,715,998. Other wall safe 
constructions with removable doors were disclosed in U.S. Pat. Nos. 
4,145,978, 4,148,265, 4,158,377, 4,258,632 and 4,278,033. 
In accordance with the Telsafe limited access security system, a newly 
registered guest received a randomly selected sealed packet containing a 
door having a lock cylinder and a key. The door could then be used for 
sealing a selected safe mounted within the guest's hotel room. Each door 
was compatible for use with any of the strong boxes provided in each of 
the guest rooms. This concept provided a theft deterrent, however there 
were still certain inherent disadvantages. It should be apparent, for 
example, that the removable door which was made of heavy gauge steel was 
thus subject to certain weight and size limitations. As a consequence, the 
dimensions of the strong box were correspondingly restricted. This had an 
adverse effect on the storage capacity and was a limiting factor as to 
what items of personal property could be stored therein. A distinct 
shortcoming therefore of those strong boxes was that larger size or bulky 
objects such as cameras, cassette players and C.B. radios could not be 
stored therein. 
The earlier filed related application provided a solution to this 
problem--the strong box was provided with a hinged door and thus 
eliminated the size restraints. The several embodiments disclosed 
arrangements for securing a removable lock cylinder to the swingable door. 
The lock cylinders were interchangeable and could be randomly distributed 
to each new guest and adapted for the in-room wall safe. 
The present invention introduces a still further improvement wherein a lock 
cylinder permanently affixed to a hinged door is provided with an 
interchangeable lock component. This is in full consonance with the 
security system concept heretofore described yet provides a more 
convenient and reliable agency for limited access control. 
DISCLOSURE OF THE INVENTION 
Briefly, the nature of this invention involves an individualized room 
depository for the accommodation of hotel guests or other lessees. A 
purpose of this device is to provide protection against unauthorized entry 
into a strongbox either by lock picking, key duplication or direct attack 
upon the receptacle. 
In summary, the device of this invention concerns a receptacle forming a 
lock box which is adapted for bolted connection onto a fixed wall surface 
or other convenient location. The receptacle includes an access opening 
and hinged door having inturned flanges along a top and bottom margin. The 
hinged side of the door is provided with an edge return which is designed 
to interlock with a curved lip along the opening when the door is in a 
closed position. The flanges are received within confronting guard 
recesses. The remaining vertical side opposite the edge return has a 
transverse face and is accommodated within the receptacle opening for 
providing a relatively jimmy-resistant door. 
A locking mechanism is incorporated within a housing mounted to a side wall 
of the receptacle opening. The locking mechanism includes a locking cam 
for operating a twin locking bar arrangement. The bars are extendable 
through aligned openings within the respective door flanges along the 
upper and lower edge of the door. 
The gist of this improvement is directed to the utilization of a lock 
cylinder assembly mounted within the door which has a detachable key plug. 
The key plug and an operating key are adapted for interchangeable 
applications within a plurality of similar lock cylinder assemblies 
although companion keys can be required for each of the respective key 
plugs. The key plug further includes a tail for activating the locking 
cam. 
An advantage of this invention is that the key plug can be readily inserted 
and removed from the cylinder housing for insuring smooth, efficient and 
reliable operation. 
Another feature of this invention concerns the interrelationship between 
the removable key plug and cylinder housing whereby only the key and not 
the plug is removable when the door is in the locked mode. 
Having thus summarized the invention, it will be seen that it is an object 
thereof to provide a security lock box of the general character described 
herein which is not subject to the aforementioned disadvantages. 
Specifically, it is an object of this invention to provide a security lock 
box having a lock cylinder housing adapted for receiving an 
interchangeable key plug. 
Still another object of this invention is to provide a security lock box 
having a removable key plug adapted for interconnection with a locking cam 
for operating an integral locking mechanism. 
A still further object of this invention is to provide a security lock box 
having a key plug which can be withdrawn from the lock cylinder housing 
yet is permanently retained within the cylinder housing when the door is 
in a locked mode. 
Still another object of this invention is to provide a security lock box of 
the general character described which is simple in construction, low in 
cost, reliable in use, and well adapted for mass production fabrication 
techniques. 
Other objects, features and advantages of the invention in part will be 
obvious and in part will be pointed out hereinafter. 
With these ends in view, the invention finds embodiment in certain 
combinations of elements and arrangements of parts by which the objects 
aforementioned and certain other objects are hereinafter attained, all as 
more fully described with reference to the accompanying drawings and the 
scope of which is more particularly pointed out and indicated in the 
appended claims.

BEST MODE FOR CARRYING OUT THE INVENTION 
Referring now in detail to the drawings, the reference numeral 20 denotes 
generally a security lock box of this invention. The lock box 20 is 
comprised of a container or receptacle 22 having a hingedly mounted door 
24. It should be noted that the term lock box as used herein is also 
considered to generically encompass a strongbox, safe, personal vault or 
similar protective enclosure. 
As particularly noted in FIGS. 1 and 5, the door 24 includes a cylinder 
lock 26 and handle 28. In order to facilitate installation by bolting box 
20 to a wall or other surface, interior bolt holes (not shown) can be 
provided. In this exemplary embodiment the receptacle 22 and door 24 are 
fabricated of heavy gauge steel. By way of example, the lock box 20 
typically has the following dimensions: height 33 cm. (13 inches), width 
36 cm. (14 inches), depth 31 cm. (12 inches) with a door size of 
approximately 29 cm..times.29 cm. (111/2 inches.times.111/2 inches). The 
approximate weight of this lock box is 20 kilograms (44 pounds). The 
preferred cylinder lock 26 is a modification of a commercially available 
lock sold under the trademark Medeco (catalog number 64-550). In addition, 
the receptacle 22 has been provided with wood grain laminated finish for 
compatibility with hotel room decor. 
The door 24 is preferably fabricated of a single panel having a flange 30, 
32 along respective upper and lower panel edges. The flange 30, 32 lies 
substantially normal to the plane of the door 24 and is further provided 
with a respective locking slot 34, 36 and a respective hinge pin aperture 
38, 40. The vertical edge of the door 24 adjacent to the hinge pin 
aperture 38, 40 includes a curved extension or edge return 42 coextensive 
with the edge of the door 24. The distal vertical door edge is defined by 
a transverse face 44. The door 24 is further provided with aperture 46 for 
receiving the cylinder lock 26. A hinge pin 39 is used for pivotally 
mounting the door 24 to the receptacle 22. In the embodiment illustrated 
the hinge pin 39 extends through each of the respective hinge pin 
apertures 38, 40 and terminates within the respective upper and lower 
walls of receptacle 22. As previously noted, the edge return 42 engages an 
inwardly curved lip 43 when in a closed position as shown in FIG. 6. In 
this connection it should be observed that, even if the hinge pin 39 
should be removed, the door 24 will still be secure against forceable 
entry. When the door 24 is opened (as shown in FIG. 2), the edge return 42 
clears the inturned lip 43 which does not present an obstacle to the 
swingable movement of the door 24. 
In regard to the securement of the top and bottom edges of door 24, 
reference is made to FIGS. 2 and 6 wherein it will be seen that the upper 
flange 30 and the lower flange 32 are received within respective guard 
recesses 31, 33. The transverse face 44 is also received interiorly of the 
receptacle 22. It should thus be apparent that the four peripheral edges 
of the door 24 are not readily accessible to a prying tool for opening the 
lock box 20. 
Referring once again to the cylinder lock 26, it should be observed with 
particular reference to FIGS. 5 and 9 that the assembly includes an outer 
shell or cylinder housing 48 having an integral bezel 49 and a threaded 
portion for receiving a hexagonal mounting nut 50. The cylindrical housing 
48 includes a rotatable core or key plug 52. The key plug 52 contains a 
key receiving aperture 54 for accepting an operating key 56. In addition, 
the plug 52 is formed with a substantially cylindrical surface 57 which 
terminates in a rectangular lug or tail member 58. The tail member 58 has 
a set of fins 60 adapted for accommodation within a complementary series 
of grooves 62 positioned interiorly within the cylinder housing 48. When 
the fins 60 are engaged within the grooves 62, the key plug 52 cannot be 
removed. Additionally, the tail member 58 will be displaceable behind a 
pair of shoulder segments 66 at the distal end of the housing 48 to 
further prevent withdrawal of the key plug 52 when the door 24 is in a 
locked mode as shown in FIGS. 1, 9 and 10. 
Directing attention now to the key plug 52, the cylindrical surface 57 
includes a longitudinal slot 68 through which a spring urged retainer or 
keeper bar 70 can project. The keeper bar 70 can be depressed to a 
position substantially flush with the cylindrical surface 57 only when the 
key 56 is inserted into the key aperture 54. Furthermore, the key 56 
cannot be withdrawn from the key plug 52 if the keeper bar 70 is 
depressed. 
The cylinder housing 48 includes a passageway 72 for slidingly 
accommodating the key plug 52 for longitudinal and rotational movement. In 
this connection it should be noted that the pair of shoulder segments 66 
provide a substantially rectangular egress opening 74 for the tail member 
58 which must be in alignment with the rectangular egress 74 for entry and 
withdrawal (see FIGS. 7 and 8). This alignment corresponds with a keyway 
76 in a latching mechanism 78 as will be further described hereinafter and 
thus insures registration of the tail 58 within the keyway 76. The 
passageway 72 also has two longitudinal channels 80 for accepting the 
keeper bar 70 as it projects through the slot 68. The channels 80 are 
provided on opposite sides of the passageway 72 and placed such that when 
the tail 58 is in a locked position (FIGS. 9 and 10), the keeper bar 70 
will be seated within the channel 80 and the key 56 can be withdrawn. 
In order to guide entry of the key plug 52 within the passageway 72 a 
portal notch 82 is provided for engaging and depressing the keeper bar 70. 
As the key plug 52 is rotated into the locked position, the keeper bar 70 
will be released and "snaps" into the channel 80 providing both an audible 
and mechanical indication that the tail member 58 has rotated into the 
locked mode. Since the tail member 58 will now engage the shoulder 
segments 66 as the fins 60 are simultaneously received within the grooves 
62, the key 56 can be withdrawn and the plug 52 will remain within the 
housing 48 as the key 56 is withdrawn. In order to remove the key plug 52, 
the key 56 must be reinserted and the plug 52 rotated 90 degrees such that 
the tail member 58 is in alignment with the rectangular egress opening 74 
of the cylinder housing 48 and the keeper bar 70 is depressed against the 
passageway 72. The key 56 cannot now be withdrawn from the key plug 52 and 
will thus permit removal with the key plug 52. 
The operation of the latching mechanism 78 will now be described with 
particular reference to FIGS. 3 and 4. As illustrated, the latching 
mechanism 78 is enclosed within a housing 84 which is recess mounted along 
one side of the receptacle 22 and is further spaced from the respective 
top and bottom walls of the receptacle 22 to accommodate the flanges 30, 
32. 
A circular locking cam 86 is pivotally mounted to the rear wall of the 
housing 84 by a pivot pin 88. The locking cam 86 further includes a 
circumferential lobe 90 as illustrated in FIG. 4 and a pair of locking 
bars 92, 94 each of which is pinned at one end to the cam 86. A distal end 
of each of the locking bars is extendable through a respective top 96 and 
bottom 98 wall opening of the housing. A spring 100 affixed to a side wall 
of the housing engages a lower locking bar for urging the locking cam 86 
in a clockwise direction wherein the locking bars are in an open or 
retracted position. The cam lobe 90 will be resiliently urged into contact 
with a limit stop 102. When the locking cam 86 is rotated in a 
counterclockwise direction as indicated by the arrows in FIG. 4 and broken 
line illustration, each of the locking bars 92, 94 will then be extendable 
through the respective apertures 96, 98 in the top and bottom walls of the 
housing and through the locking slots 34, 36 in the respective door flange 
30, 32. When the locking cam 86 is in this locked position, the cam lobe 
90 contacts limit stop 104. 
With regard to the activation of the locking cam 86, reference is made to 
the rectangular keyway 76. The keyway 76 is formed within a bracket 106 
affixed to the cam 86 and is adapted for receiving the tail member 58 of 
the key plug 52. It should be apparent that use of the operating key 56 
and rotation of the key plug 52 will be effective for rotating the locking 
cam 86 which will be selectively held in a locked position when the keeper 
bar 70 snaps into channel 80. The key 56 can then be removed. 
Thus, it will be seen that there is provided a security lock box with a 
removable key plug which achieves the various objects of the invention and 
which is well adapted to meet the conditions of practical use. 
Since other possible embodiments might be made of the present invention and 
various changes might be made in the exemplary embodiment set forth, it is 
to be understood that all material set forth or shown in the accompanying 
drawings is to be interpreted in an illustrative sense and not in a 
limiting sense.