U.S. patent number 3,916,657 [Application Number 05/548,921] was granted by the patent office on 1975-11-04 for double key axial split-pin tumbler-type lock.
This patent grant is currently assigned to Chicago Lock Co.. Invention is credited to Robert L. Steinbach.
United States Patent |
3,916,657 |
Steinbach |
November 4, 1975 |
Double key axial split-pin tumbler-type lock
Abstract
An axial split-pin tumbler-type lock having a lock cylinder, a
three-part plug assembly inserted in the cylinder, and a plurality
of spring-pressed pin tumbler assemblies carried by the plug
assembly is supplied with two keys, the first key serving to rotate
two parts of the plug assembly conjointly to operate the lock, and
the second key serving to rotate but one of the two parts, the one
part being rotated to an inoperative position in which the lock
cannot be picked directly and requiring for operation of the lock
from that position the use of the second and first keys
successively in that order.
Inventors: |
Steinbach; Robert L. (Chicago,
IL) |
Assignee: |
Chicago Lock Co. (Chicago,
IL)
|
Family
ID: |
24190935 |
Appl.
No.: |
05/548,921 |
Filed: |
February 11, 1975 |
Current U.S.
Class: |
70/338; 70/339;
70/491 |
Current CPC
Class: |
E05B
27/083 (20130101); Y10T 70/7458 (20150401); Y10T
70/7593 (20150401); Y10T 70/7452 (20150401) |
Current International
Class: |
E05B
27/00 (20060101); E05B 27/08 (20060101); E05B
027/08 (); E05B 035/08 () |
Field of
Search: |
;70/337,338,339,340,341,342,343,362,363,382-385 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wolfe; Robert L.
Attorney, Agent or Firm: Gerlach; Norman H.
Claims
Having thus described the invention, what I claim as new and desire
to secure by Letters Patent is:
1. In combination with an axial split-pin tumbler-type lock having
a lock cylinder, a three-part plug assembly inserted in the
cylinder, and a plurality of tumbler assemblies carried by the plug
assembly, said plug assembly including a rear sleeve part fixed to
the cylinder, a rotatable intermediate spindle part including a
lock shaft extending through the sleeve part, a rotatable front
drive part, and a post fixed to the drive part and having means
drivingly engaging a key for rotation of the drive part by turning
the key, said plug assembly parts each having a plurality of
longitudinal bores arranged for alignment with the bores in the
remaining parts in an initial disposition of said parts, said
aligned bores being asymmetrically disposed about the longitudinal
axis of the plug assembly, whereby the drive part may be rotated
relative to the other parts and provide an inoperative second
disposition of the parts wherein a blank area of the drive part is
disposed over aligned bores in the spindle and sleeve parts and
prevents access thereto, while at least one bore of the drive part
is disposed in alignment with aligned bores in the spindle and
sleeve parts, one of said tumbler assemblies being disposed in each
series of aligned bores in said initial disposition of the parts
and each tumbler assembly including spring means, a rear tumbler
pin, an intermediate tumbler pin, and a front tumbler pin, said
spring means yieldingly urging the several pins forwardly in the
bores in said initial disposition of the parts, whereby a first
interfacial plane between the sleeve and spindle parts, and a
second interfacial plane between the spindle and drive parts are
bridged by tumbler pins to secure the parts against relative
rotation, and the tumbler pins in each series of aligned bores may
be shifted longitudinally to cause the interface between the rear
pin and the intermediate pin to coincide with said first plane
while said second plane is bridged by at least one pin to thereby
free the drive and spindle parts for conjoint rotation relative to
the sleeve part, or alternatively to cause the interface between
the intermediate pin and the front pin to coincide with said second
plane while at least the interface between said aligned bores
having said blank area thereover in said second disposition of the
parts is bridged by one of said pins to thereby free the drive part
for rotation relative to the spindle part and the sleeve part:
first and second keys each adapted for drivingly engaging said post
and having different bittings engaging said front tumbler pins, the
bittings of the first key being adapted for shifting the tumbler
pins longitudinally in each series of aligned bores so as to free
the drive and spindle parts for cojoint rotation by the key from
said initial disposition of the parts to operate the lock, the
bittings of the second key being adapted for shifting the tumbler
pins longitudinally in each series of aligned bores so as to free
only the drive part for rotation by the key from said initial
disposition of the parts to said inoperative second disposition of
the parts, and said second key being removable from the lock in
said second disposition of the parts to leave the parts secured
against relative rotation, whereby the lock is rendered
inaccessible for direct picking and the second and first keys must
be employed successively in that order to operate the lock.
2. A combination as defined in claim 1 and including means on said
cylinder for indicating when said second key is oriented in said
second disposition of the parts.
3. A combination as defined in claim 1 and wherein said cylinder
includes a retaining flange surrounding said post and having
angularly spaced apart first and second notches, and each of said
keys includes an outwardly projecting lug received in said first
notch when its key is employed in said initial disposition of the
parts and turning behind said flange to retain the key in the lock
when the key is turned, the lug on said second key being movable
through said second notch for removing and reinserting the second
key in said second disposition of the parts.
4. A combination as defined in claim 3 and including stop means
interengaging said cylinder and said lock shaft for limiting said
conjoint rotation of the drive and spindle parts in operation of
the lock so that said second notch is outside of the travel arc of
the lug on said first key, thereby preventing removal of the first
key in said second disposition of the parts.
5. A combination as defined in claim 3 wherein said bores in each
part are seven in number arranged at intervals of 45 degrees about
the longitudinal axis of the plug assembly and at an interval of
90.degree. between two of them, the area of said drive part between
said latter bores comprising said blank area thereof.
Description
BACKGROUND OF THE INVENTION
This invention relates to an axial split-pin tumbler-type lock and
key combination employing two keys for operation of the lock.
Heretofore, various locks of the axial split-pin tumbler-type have
been devised, having means designed to limit unauthorized operation
of the locks. The prior locks have achieved varying degrees of
success. Generally speaking, it is possible ultimately to pick any
key-operated lock, and efforts to prevent unauthorized picking are
based upon rendering the operation difficult and
time-consuming.
An example of a tamper-proof axial split-pin tumbler-type lock is
disclosed in U.S. Pat. No. 3,541,819 to Kerr. This patent discloses
a lock constructed to induce a "false picking", which does not
operate the lock. A lock employing a plurality of keys for
controlling operation of the lock is disclosed in U.S. Pat. No.
3,729,964 to Hsu.
It would be desirable to provide an axial split-pin tumbler-type
lock and key combination having even lower vulnerability to picking
than the combination of the aforesaid Kerr patent, and also having
a relatively simple and economical comgination of members as
compared, for example, to the lock of the aforesaid Hsu patent.
SUMMARY OF THE INVENTION
In the invention, an axial split-pin tumbler-type lock having a
lock cylinder, a three-part plug assembly inserted in the cylinder,
and a plurality of spring-pressed pin tumbler assemblies carried by
the plug assembly is supplied with two keys, the first key serving
to rotate two parts of the plug assembly conjointly to operate the
lock, and the second key serving to rotate but one of the two
parts, the one part being rotated to an inoperative position in
which the lock cannot be picked directly combination requiring for
operation of the lock from that position the use of the second and
first keys successively in that order. Two-key operation renders
picking of the lock at least extremely difficult and time-consuming
and also serves to restrict access by key. Alternatively, if
desired, the lock can be used with but the first key.
More particularly, the invention in its preferred embodiments
includes in combination with an axial split-pin tumbler-type lock
having a lock cylinder, a three-part plug assembly inserted in the
cylinder, and a plurality of tumbler assemblies carried by the plug
assembly, said plug assembly including a rear sleeve part fixed to
the cylinder, a rotatable intermediate spindle part including a
lock shaft extending through the sleeve part, a rotatable front
drive part, and a post fixed to the drive part and having means
drivingly engaging a key for rotation of the drive part by turning
the key, said plug assembly parts each having a plurality of
longitudinal bores arranged for alignment with the bores in the
remaining parts in an initial disposition of the parts, said bores
being asymmetrically disposed about the longitudinal axis of the
plug assembly, whereby the dirve part may be rotated relative to
the other parts and provide an inoperative or ineffectual second
disposition of the parts wherein a blank area of the drive part is
disposed over aligned bores in the spindle and sleeve parts and
prevents access thereto, while at least one bore of the drive part
is disposed in alignment with aligned bores in the spindle and
sleeve parts, one of the tumbler assemblies being disposed in each
series of aligned bores in said initial disposition of the parts
and each tumbler assembly including spring means, a rear tumbler
pin, an intermediate tumbler pin, and a front tumbler pin, said
spring means yieldingly urging the several pins forwardly in the
bores in said initial disposition of the parts, whereby a first
interfacial plane between the sleeve and spindle parts, and a
second interfacial plane between the spindle and drive parts are
bridged by tumbler pins to secure the parts against relative
rotation, and the tumbler pins in each series of aligned bores may
be shifted longitudinally to cause the interface between the rear
pin and the intermediate pin to coincide with the first plane while
the second plane is bridged by at least one pin to thereby free the
drive and spindle parts for cojoint rotation relative to the sleeve
part, or alternatively to cause the interface between the
intermediate pin and the front pin to coincide with the second
plane while at least the interface between the aligned bores having
the blank area thereover in said second disposition of the parts is
bridged by one of said pins to thereby free the drive part for
rotation relative to the spindle part and the sleeve part: first
and second keys each adapted for drivingly engaging the post and
having different bittings engaging the front tumbler pins, the
bittings of the first key being adapted for shifting the tumbler
pins longitudinally in each series of aligned bores so as to free
the drive and spindle parts for cojoint rotation by the key from
said initial disposition of the parts to operate the lock, the
bittings of the second key being adapted for shifting the tumbler
pins longitudinally in each series fo aligned bores so as to free
only the drive part for rotation by the key from said initial
disposition of the parts to said inoperative second disposition of
the parts, and said second key being removable from the lock in
said second disposition of the parts to leave the parts secured
against relative rotation, whereby the lock is rendered
inaccessible for direct picking and the second and first keys must
be employed successively in that order to operate the lock.
In further preferred embodiments of the invention, means are
provided on the lock cylinder for indicating when the second key is
oriented in said second disposition of the parts. More preferably,
the cylinder includes a retaining flange surrounding the post and
having angularly spaced apart first and second notches, and each of
the keys includes an outwardly projecting lug received in the first
notch when its key is employed in the initial disposition of the
parts and turning behind the flange to retain the key in the lock
when turned, the lug of the second key being movable through the
second notch for removing and reinserting the second key in the
second disposition of the parts. Additional preferred structure is
described hereinafter.
The lock and key combination of the invention provides a valuable
increase in lock security while at the same time increasing the
versatility of the lock. The lock itself is relatively simple and
economical in its construction and operation, its preferred
embodiment actually being simpler and less expensive than the
preferred embodiment of the above-described Kerr patent lock, on
which the present lock is based. The only additional part required
is a second key, while parts of the preferred embodiment of the
Kerr lock are obviated.
BRIEF DESCRIPTION OF THE DRAWINGS
The attached drawings illustrate a preferred embodiment of the
invention, without limitation thereto. In the drawings, like
elements are identified by like reference symbols in each of the
views, and:
FIGS. 1 and 2 are perspective views of first and second keys,
respectively, which serve to operate the lock illustrated in FIG.
3, in accordance with the invention;
FIG. 3 is a front perspective view of a preferred embodiment of an
axial split-pin tumbler-type lock employed in the invention
illustrating the lock in its initial or starting attitude;
FIG. 4 is a front elevational view of the lock on a reduced
scale;
FIG. 5 is a transverse sectional view of the lock on a reduced
scale, taken on line 5--5 of FIG. 3, also showing an alternate
position of the locking bolt in phantom lines;
FIG. 6 is an enlarged partly side elevational and partly
longitudinal sectional view of the lock, with certain parts broken
away and in section, the sections being taken aubstantially on
lines 6--6 of FIG. 4, illustrating the lock with its plug assembly
parts in an initial disposition thereof;
FIG. 7 is a fragmentary view of the lock similar to FIG. 6 but
having the first key inserted therein, the key being shown
fragmentarily and with parts broken away and in section,
illustrating how the lock may be operated by turning the key;
FIG. 8 is a view similar to FIG. 7 but showing the second key
inserted in place of the first key, with the key being shown
fragmentarily and with parts broken away and in section,
illustrating how one plug assembly part may be rotated by turning
the key;
FIG. 9 is a view similar to FIG. 8 but with the key turned to place
the lock in an inoperative second disposition of its plug assembly
parts; and
FIG. 10 is a view similar to FIG. 9 but with the key removed to
leave the plug assembly parts secured against relative rotation in
their second disposition.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIGS. 1-3 of the drawings, the lock and key
combination of the invention includes a first key 1, which may be
termed a true operating key, a second key 2, which may be termed a
lockout or prevent key, and an axial split-pin tumbler-type lock 3.
The keys are of generally conventional construction. Thus, the key
1 includes a wing-type handle 11 secured to a cylindrical tubular
shank or bit 12. A series of partly cylindrical bittings 13 is
provided on the outer periphery of the shank 12 at its circular
free end 14. The bittings 13 in the illustrative preferred
embodiment number seven, and they are angularly spaced around the
end 14 on 45.degree. centers, except for two bittings, which are
spaced apart on 90.degree. centers.
A rectangular retaining lug 15 is fixed on the outer surface of the
key shank 12 closely adjacent to and spaced from the end 14,
equidistantly between those bittings 13 which are spaced apart
90.degree.. On the inner surface of the shank 12, behind the lug
15, and likewise adjacent to and spaced from the free end 14, is a
rectangular locating and plug-engaging lug 16. Similarly, the
second key 2 includes a handle 21, a tubular shank 22, partly
cylindrical bittings 23, a shank free end 24, a retaining lug 25,
and a locating and plug-engaging lug 26. At least some of the
bittings 13 and 23 on the respective keys 1 and 2 have different
depths, for arranging the lock tumbler assemblies in different
dispositions, as described hereinafter.
Referring to FIGS. 3-6, the lock 3 is based upon the lock disclosed
in the above-identified Kerr U.S. Pat. No. 3,541,819. The lock 3
includes a lock cylinder 30, a three-part plug assembly 32 inserted
in the cylinder, and a plurality of tumbler assemblies 34 carried
by the plug assembly. A radial locking bolt 36 is carried by the
plug assembly, and it is rotatable through an angle of 90.degree.,
between the positions illustrated in full and phantom lines in FIG.
5, although any suitable degree of rotation may be selected.
The lock cylinder 30 includes a circular tubular threaded body 38
having flats 39 on opposite sides thereof, an enlarged ring-like
and tapered head 40 integral with one end of the body 38, and an
annular retaining flange 41 integral with the head 40 around the
inner periphery thereof. The head 40 and the flange 41 form part of
the face or front end of the lock 3. The flange 41 is provided with
first and second rectangular, radial notches 42 and 43,
respectively, and it defines the outer wall of a circular keyway 44
in the face of the lock 3. The notches 42 and 43 are disposed at
angular distances between centers of 45.degree.. The cylinder body
38 has a bore 45 of slightly greater diameter than the internal
diameter of the head 40, providing an annular shoulder 46 (FIG. 6)
at the junction of the body and head within the cylinder 30.
A mounting nut 48, illustrated in FIG. 6, is in threaded engagement
with the cylinder body 38, and serves for mounting the lock 3 upon
a door or other suitable structure (not illustrated). Thus, the
cylinder body 38 may be inserted through a suitable hole or opening
in such a door, and a door panel may be clamped between the nut 48
and the cylinder head 40.
Referring particularly to FIG. 6, the plug assembly 32 includes a
rear sleeve part 50 fixed to the cylinder body 38 by a set screw
52, a rotatable intermediate spindle part 54 and a rotatable front
drive part 56. The several plug assembly parts 50, 54 and 56 are
generally cylindrical and have external diameters approximating the
diameter of the bore 45 of the cylinder body 38. The spindle and
drive parts 54 and 56 are retained at the front end of the cylinder
body 38 by the shoulder 46, on which the drive part 56 abuts.
The spindle part 54 includes an axial cylindrical lock shaft 60
extending rearwardly through and journaled in the sleeve part 50.
The shaft terminates in a threaded end 62 having flats 64 on
opposite sides thereof and projecting rearwardly beyond the
cylinder body 38. The spindle part 54 is provided with an axial
cylindrical pilot bore 66 extending rearwardly from its front
face.
A cylindrical stub shaft 68 extends axially rearwardly from the
drive part 56, and a cylindrical center post 70 extends axially
forwardly therefrom. A rectangular longitudinal lug-receiving
groove 72 (FIGS. 3-5) is formed along the side of the post 70. The
shaft 68 is received in the pilot bore 66 in the spindle part 54.
The post 70 extends to the face of the lock, its outer end being
substantially in a plane with the front surfaces of the head 40 and
the retaining flange 41. The post 70 is spaced inwardly from the
retaining flange 41, to form the annular keyway 44 therewith. In
the illustrative embodiment, the stub shaft 68 and the post 70 are
formed integrally with the drive part 56, but it may be preferable
that the shaft and the post constitute a separate member or members
fixed to the drive part 56 and be constructed of different
material.
The sleeve part 50, the spindle part 54, and the drive part 56 of
the plug assembly 32 each have a plurality of longitudinal bores
74, 76, and 78, respectively, arranged for alignment or registry
with the bores in the remaining parts in an initial disposition of
the parts, such as illustrated in FIG. 6. The bores 74 in the
sleeve part 50 are blind bores, and the remaining bores 76 and 78
extend through their parts 54 and 56. The bores in each part are
asymmetrically disposed about the longitudinal axis of the plug
assembly 32. While another number of bores may be provided, the
preferred illustrative embodiment has seven bores in each part. As
illustrated in FIG. 5 for the bores 78 in the drive part 56, the
bores in each part are arranged at intervals of 45.degree.,
center-to-center, about the longitudinal axis of the plug assembly
32, and at an interval of 90.degree. between two of them. The area
80 of the drive part 56 between the latter bores constitutes a
blank area thereof, and a similar blank area exists in the sleeve
and spindle parts 50 and 54.
In the structure of the lock 3 so far described, the spindle part
54 is rotatable in the cylinder 30 for operation of the lock, in a
manner such as described hereinafter. The drive part 56 also is
rotatable in the cylinder 30. The spindle part 54 and the drive
part 56 are rotatable relative to each other or cojointly. The
freedom of the spindle and drive parts to rotate is controlled by
the tumbler assemblies 34.
As illustrated in FIG. 6, each tumbler assembly 34 includes a coil
compression spring 82, a rear tumbler pin 84, an intermediate
tumbler pin 86, and a front tumbler pin 88, each of the pins being
cylindrical. In each series of aligned bores 74, 76, and 78, a coil
compression spring 82 is seated in the blind bore 74, a rear
tumbler pin 84 is seated on the spring 82 in the blind bore 74, an
intermediate tumbler pin 86 is inserted in the spindle part bore 76
and abuts on the rear pin 84, and a front tumbler pin 88 is
inserted in the drive part bore 78 and abuts on the intermediate
pin 86. While the several pins are, in general, associated with
respective principal bores, as described, they are of varying
lengths, which may exceed the lengths of the bores. The several
pins in each tumbler assembly 34 are spring-pressed by their spring
82, to cause the front pins 88 to abut on the rear surface of the
retaining flange 41, as seen in FIG. 6. A portion only, less than
one-half, of each front pin 88 is exposed in the keyway 44 (see
FIG. 4), and thereby accessible for engagement with a key.
In the foregoing initial disposition of the parts, the several pins
bridge a first interfacial plane 90 between the sleeve part 50 and
the spindle part 54, and a second interfacial plane 92 between the
spindle part 54 and the drive part 56, to secure the parts against
relative rotation. The tumbler pins in each assembly 32 may be
shifted longitudinally against the pressure of the spring 82,
moving the pins rearwardly, to cause the interface between the rear
pin 84 and the intermediate pin 86 to coincide with the first plane
90, while the second plane 92 is bridged by at least one pin of the
several plug assemblies 32, to thereby free the drive part 56 and
the spindle part 54 for cojoint rotation relative to the sleeve
part 50. Alternatively, the tumbler pins may be shifted
longitudinally to cause the interface between the intermediate pin
86 and the front pin 88 to coincide with the second plane 92, while
the first plane 90 is bridged by at least one pin, as described
hereinafter, to thereby free the drive part 56 for rotation
relative to the spindle part 54 and the sleeve part 50.
The first key 1, illustrated in FIG. 1, is constructed for
operating the lock 3. The free end 14 of the key shank 12 is
inserted in the keyway 44, with the locating lug 16 entering the
groove 72 in the post 70, thereby providing a driving
interengagement of the key and the post 70, and also the drive part
56. The retaining lug 15 on the key enters the first notch 42 in
the retaining flange 41. As illustrated in FIG. 7, when the key 1
is inserted until its free end 14 bottoms on the drive part 56, the
key bittings 13 engage respective front tumbler pins 88 and shift
the tumbler pins in the several tumbler assemblies 34 to positions
such as illustrated. The retaining lug 15 on the key moves behind
the retaining flange 41.
At this time, the interface between the rear pin 84 and the
intermediate pin 86 in each of the tumbler assemblies 34 coincides
with the first interfacial plane 90, while the second interfacial
plane 92 is bridged by at least one tumbler pin. Any or all of the
bridging pins may be intermediate pins 86 or front pins 88, and in
FIG. 7, they are intermediate pins 86. The first key 1 may be
rotated and, owing to the interengagement of its locating lug 16
with the center post 70, the drive part 56 rotates therewith.
Further, owing to the bridging of the second interfacial plane 92
by pins such as the intermediate pins 86 seen in FIG. 7, the
spindle part 54 also rotates with the key. Accordingly, the lock
shaft 60 is rotated, to operate the lock.
One of various possible locking arrangements is illustrated in the
drawings. Referring to FIG. 6, the locking bolt 36 is secured on
the threaded end 62 of the lock shaft 60 by means of two nuts 94
and 96 on opposite sides of the bolt. The bolt then rotates with
the lock shaft 60, and may be rotated between locking and unlocking
positions, for example, as illustrated respectively by full and
phantom lines in FIG. 5.
In order to limit the movement of the locking bolt 36 to a
90.degree. throw, as in the illustrative embodiment, a stop flange
98 (FIG. 6) is formed on the lock cylinder body 38, integrally
therewith, and projects rearwardly therefrom. A stop washer 100 is
mounted on the lock shaft, adjacent to the cylinder body 38, and
the washer is rotatable with the shaft. The stop washer 100 is
contoured to abut on the stop flange 98 at the opposite ends of a
90.degree. path of travel, thereby limiting rotation of the lock
shaft 60 to a selected 90.degree. arc of the circle of
rotation.
The operation of the lock 3 as so far described, and the
corresponding structure, are essentially as described in the
above-identified Kerr U.S. Pat. No. 3,541,819. The patent further
describes the function of a front plug part numbered 18 like the
drive part 56 herein, which serves to induce a "false picking". The
false picking is facilitated by tumbler balls 42 in the patent. In
the present invention, inducement ot false picking is not relied
on, although it may play a part in preventing unauthorized access.
Therefore, the tumbler balls 42 of the preferred structure of the
patent are omitted from the preferred structure of the present
invention. Also omitted from the preferred structure of the patent
are a plunger or limit pin 82, its spring 86, and a clearance notch
80 in the front plug part, which would interfere with the operation
of the lock in the present invention.
The present invention achieves an additional function employing the
structure including the drive part 56, and the second key 2, as
illustrated in FIGS. 8-10, to which reference now is made. As in
the case of the first key 1, the free end 24 of the shank 22 of the
second key 2 is inserted in the lock keyway 44. The locating and
plug-engaging lug 26 engages the center post 70 in its groove 72
(see FIG. 9), and the retaining lug 25 is received in the first
notch 42. When the second key 2 is fully inserted, as illustrated
in FIG. 8, its free end 24 bottoms on the drive part 56, and the
retaining lug 25 is behind or inwardly of the retaining flange 41.
The different bittings 23 of the second key 2 engage the front
tumbler pins 88 to shift the pins in each tumbler assembly 34
longitudinally, to cause the interface between each intermediate
pin 86 and adjacent front pin 88 to coincide with the second plane
92. At the same time, at least one of the tumbler pins of the
tumbler assemblies 34 bridges the first interfacial plane 90,
preventing the spindle part 54 from rotating. The drive part 56
thereby is freed for rotation relative to the spindle part 54 and
the sleeve part 50.
The second key 2 is rotated from the position illustrated in FIG. 8
to the position illustrated in FIG. 9, counterclockwise as viewed
at the face of the lock, and through an angle of 45 degrees. The
lock then is in a second disposition of the plug assembly parts, as
illustrated in FIG. 9. At this time, the blank area 80 (see also
FIG. 5) of the drive part 56 is disposed over or in alignment with
one pair of aligned bores 76 and 74 in the spindle part 54 and the
sleeve part 50, respectively, preventing access to such bores. Six
other pairs of aligned spindle and sleeve part bores 76 and 74 are
aligned with respective bores 78 in the drive part 56, as
illustrated by the lower series of aligned bores in FIG. 9. The
retaining lug 25 of the second key 2 then is in registry with the
second notch 43 in the retaining flange 41. The second disposition
of the plug assembly parts is an inoperative disposition, inasmuch
as the locking function has not been affected, i.e., the locking
bolt 36 is not moved from its original position, illustrated in
FIGS. 3-6.
The second key 2 may be removed from the lock 3, with the retaining
lug 25 on the key moving through the second notch 43 in the
retaining flange 41, and it may be reinserted in the reverse
manner. With the second key 2 removed, the tumbler assemblies 34
are disposed in the lock 3 as illustrated in FIG. 10: one rear pin
84 and an adjacent intermediate pin 86, shown in the upper portion
of the view, are urged by a spring 82 into abutting engagement of
the intermediate pin 86 with the drive part 56 as in FIG. 9, while
the intermediate pin 86 bridges the first plane 90 between the
sleeve part 50 and the spindle part 54. It is preferred in addition
that the first plane 90 be bridged by pins in some or all of the
remaining series of aligned bores, as illustrated by the rear pin
84 in the bottom portion of FIG. 10. In this manner, the spindle
part 54 is fixed or locked to the sleeve part 50, in turn fixed to
the lock cylinder 30, so that the lock cannot be operated. The
second interfacial plane 92 is bridged by one of the tumbler pins
in each series of aligned bores around the plug assembly 32,
although the second plane in other embodiments may be bridged by a
lesser number of pins, as little as one. The bridging pin is an
intermediate pin 86 as illustrated in the lower portion of FIG. 10,
but alternatively, may be a front pin 88. With both interfacial
planes 90 and 92 bridged by tumbler pins, the sleeve part 50, the
spindle part 54, and the drive part 56 are secured against relative
rotation.
The intermediate pin 86 and the adjacent rear pin 84 are rendered
inaccessible by the disposition of the blank area 80 of the drive
part 56 thereover, so that the lock cannot be picked directly. The
same result would be achieved if the first interfacial plane 90
were bridged by the rear pin 84 rather than the intermediate pin
86. It is necessary to prevent picking that the first plane 90 be
bridged by one or the other of the two pins 84 and 86 that are
covered by the blank area 80.
The first key 1 is inoperative to function in any way when the
parts are in their second disposition, as in FIG. 10, and,
consequently, operation of the lock 3 by the first key 1 is "locked
out" or prevented by the use of the second key 2. In order to
operate the lock from the condition of FIG. 10, it is necessary
initially to employ the second key 2 in a reverse manner, to return
the plug assembly parts to their initial disposition, illustrated
in FIG. 8, followed by removal of the second key. Then, the first
key 1 must be inserted, as illustrated in FIG. 7, and rotated to
operate the lock, as described above.
In the illustrative preferred embodiment of the invention, the stop
flange 98 and the stop washer 100 (FIG. 6) are constructed so as to
limit the rotation of the spindle part 54 to clockwise rotation (as
viewed from the front) through an angle of 90.degree. from the
initial disposition of the parts. The first key 1 is inserted for
operation of the lock 3 with the parts disposed as illustrated in
FIGS. 3 and 4, in which disposition the retaining lug 15 is
inserted through the first notch 42. The first key 1 is rotated
90.degree. in the clockwise direction, as governed by the stop
flange 98 and stop washer 100, to rotate the locking bolt 36
through the same arc, is illustrated in FIG. 5, and thereby operate
the lock. The first key 1 cannot be removed in its rotated
position, inasmuch as its retaining lug 15 is held in place by the
retaining flange 41. The first key 1 can only be removed by
returning it to its initial position, in which the parts are in
their initial disposition, as in FIG. 3, when the retaining lug 15
can be withdrawn through the first notch 42. The lock and the first
key 1 thus provide a one-way key pull, which requires the operator
to return the key to its initial position in order to remove it
from the lock, and insures that the lock is restored to its initial
condition before the operator leaves. The second notch 43 is
outside of the travel arc of the retaining lug 15 of the first key
1. Consequently, the first key 1 cannot be removed by withdrawing
the lug 15 through the second notch 43 in the second disposition of
the parts, which would place the locking bolt 36 in an undesired
position.
The second key 2, like the first key 1, initially is inserted when
the parts are in their initial disposition illustrated in FIGS. 3
and 4. To perform its function, the second key 2 is turned in the
counterclockwise direction, until its retaining lug 25 registers
with the second notch 43. The second notch 43 functions to indicate
when the second key is oriented in the second disposition of the
parts, and the notch also permits removal of the key, allowing the
retaining lug 25 to pass therethrough. It will be apparent that the
retaining lug 25 may be dispensed with, and other indicating means
may be provided on the retaining flange 41 or the head 40, such as
a suitable marking which is related to the position of the second
key 2.
The lock 3 can be operated with the first key 1 alone, so long as
it is in the condition illustrated in FIGS. 3-6. In this condition,
however, it is subject to possible direct picking, rendered more
difficult by the use of a three-part plug assembly 32. In order to
prevent direct picking, the second key 2 is used, in the manner
illustrated in FIGS. 8-10. The lock in the position of FIG. 10 then
cannot be picked directly, because a picking tool cannot penetrate
the blank area 80 of the drive part 56, behind which a tumbler pin
86 (or 84) bridges the first interfacial plane 90 and prevents the
spindle part 54 from rotating. The only picking operation possible
in this condition of the lock is to first pick the lock by moving
the tumbler pins so as to free the drive part 56 for rotation back
to the initial disposition of the parts, illustrated in FIG. 6.
Then, it is necessary to pick the lock a second time and in such a
manner as to free the spindle part 54 for rotation with the drive
part 56, and not free only the drive part. The intricacy of the
picking operations and the time consumed are prohibitive if, in
fact, the picking can be accomplished by unauthorized persons. Once
the second key 2 is used, therefore, two keys are required to
operate the lock, and even the authorized possessor of a first key
1 is unable to open the lock without the second key 2. For
different locks, the keys 1 and 2 can be provided with various
arrangements of bittings 13 and 23, with correspondingly varying
tumbler pin sizes. The bittings on either key may remain the same
while the bittings on the other key and appropriate tumbler pin
sizes are varied for different locks.
While a preferred embodiment of the invention has been illustrated
and described, it will be apparent that various changes and
modifications may be made therein within the spirit and scope of
the invention. It is intended that such changes and modifications
be included within the scope of the appended claims.
* * * * *