Lock assembly with over-torque defense system

A lockset mechanism (20, 120) is provided with a spindle subassembly (24, 124) having a spindle component (44, 128) particularly configured to fracture when an over-torque is applied thereto for uncoupling the handle subassembly (22, 122) from the latch bolt subassembly (26). A spring mechanism (64, 130) is operably disposed between the lockset housing (32, 164) and the spindle subassembly (24, 124) for urging the spindle subassembly (24, 124) including the fractured spindle component (44, 128) away from the handle subassembly (22, 122) to render the lockset mechanism (20, 120) inoperable thereby.

TECHNICAL FIELD 
The present invention relates generally to a lockset mechanism adapted to 
provide a torque-releasable knob for defeating a forced entry attack, and 
more particularly to a lockset mechanism having a spindle subassembly 
operable in an enabled mode wherein a handle subassembly is operably 
coupled to a latch bolt subassembly through the spindle subassembly for 
normal actuation of the lockset mechanism and a disabled mode wherein the 
handle subassembly is uncoupled from the latch subassembly as a result of 
an over-torque force having been applied to the spindle subassembly 
causing it to fracture. 
BACKGROUND ART 
A variety of door lockset mechanisms operable for selectively closing and 
locking a door are generally known in the art. In principle, the door knob 
is mounted on a knob sleeve or spindle which is adapted to be blocked from 
rotation by manipulation of a turn mechanism or the like operably mounted 
on the knob, thus preventing operation of the latch bolt subassembly. The 
outside door knob may incorporate a key-actuated lock mechanism for 
actuating the locking mechanism. One method of forced entry attack on such 
lockset mechanism is to apply a high turning force or over-torque on the 
outside knob, as with a pipe wrench or other tool, sufficient to break or 
overpower the mechanism which blocks the knob spindle from rotation, 
thereby actuating the knob sleeve to retract the latch bolt. 
DISCLOSURE OF THE INVENTION 
In accordance with the principles of the present invention, a preferred 
embodiment of the lockset mechanism includes a spindle subassembly having 
a full-round spindle mounted within a half-round spindle. The half-round 
spindle is drivingly connected to a sleeve, which in turn is drivingly 
connected to a handle subassembly. When the lockset mechanism is in the 
unlocked condition, the sleeve, half-round spindle and full-round spindle 
are free to rotate within the lockset housing such that the half-round 
spindle actuates a latch bolt. When the lockset mechanism is in the locked 
condition, the spindle subassembly is constrained from rotation by means 
of a locking slide which connects the spindle subassembly to the lockset 
housing. Upon application of an over-torque to the handle subassembly, the 
half-round spindle will fracture, and a spring operably coupled between 
the lockset housing and the spindle subassembly urges the full-round 
spindle out of driving engagement with the handle subassembly. Thus, the 
spindle subassembly is disabled and the handle subassembly is uncoupled 
from the latch bolt subassembly. As a result, when the over-torque 
condition is reached, the defense system of the present invention will not 
operate the latch and the handle subassembly will otherwise spin freely. 
Accordingly, it is an object of the present invention to provide a lockset 
mechanism having a spindle subassembly operable in an enabled mode whereby 
the handle subassembly is operably coupled to the latch bolt subassembly, 
and further operable in a disengaged mode when an over-torque has been 
applied to the handle subassembly for uncoupling the connection with the 
latch bolt subassembly. 
It is another object of the present invention to provide a spindle 
subassembly having a full-round spindle mounted within a half-round 
spindle which is operably coupled to a driving sleeve of the handle 
subassembly, in which the half-round spindle is particularly configured to 
fracture upon application of an over-torque force. 
It is a further object of the present invention to provide a spindle 
subassembly having a spring operably associated therewith for urging a 
portion of the spindle subassembly out of engagement with the handle 
subassembly upon application of an over-torque force. 
It is yet another object of the present invention to provide a spindle 
subassembly having an over-torque defense system which is readily 
adaptable into existing lockset mechanism designs. 
These and other objects, features and advantages of the present invention 
will become apparent from the following description when viewed in 
accordance with the accompanying drawings and appended claims.

MODES OF CARRYING OUT THE INVENTION 
With reference to FIGS. 1-9, a first preferred embodiment of the present 
invention is illustrated including lockset mechanism 20 having handle 
subassembly 22, spindle subassembly 24 and latch bolt subassembly 26. 
Handle subassembly 22 includes knob 28 secured to exterior sleeve 30 for 
rotation therewith. Exterior sleeve 30 is received within a central 
aperture formed in exterior rose 32 and releasably secured therein by 
support washer 34 such that knob 28 and exterior sleeve 30 are rotatably 
supported within exterior rose 32. Exterior rose 32 includes rose liner 36 
and rose cover 38 releasably secured over rose liner 36 for providing a 
finished cosmetic appearance. The particular design of knob 28 may be of 
any conventional design including a generally spherical knob as 
illustrated in FIG. 1, a lever-type knob as illustrated in FIGS. 2 and 3 
or alternately any other suitable shape. Typically, knob 28 is adapted to 
receive a keyed lock cylinder 40 operably coupled to spindle subassembly 
24 for selectively locking and unlocking lockset mechanism 20. 
Spindle subassembly 24 includes full-round spindle 42 and half-round 
spindle 44 operably coupling handle subassembly 22 with latch bolt 
subassembly 26. Torsion spring mechanism 46 includes torsion spring 48 
operably coupled between half-round spindle 44 and rose liner 36 for 
providing a biased return torque for maintaining latch bolt subassembly 26 
in an extended position. Torsion spring mechanism 46 further includes 
locking slide 50 operably coupled to full-round spindle 42 and slidably 
positionable upon rotation of full-round spindle 42 between a locked 
condition wherein slide 50 engages the housing for disabling rotation of 
spindle subassembly 24 and an unlocked condition for disengaging the 
housing to permit rotation of spindle subassembly 24. Full-round spindle 
42 and half-round spindle 44 are received in an aperture 52 formed in 
latch bolt subassembly 26. Half-round spindle 44 is operably coupled to 
latch bolt 54 such that rotation of handle subassembly 22 actuates latch 
bolt subassembly 26 for movement between an extended position and a 
retracted position. 
The exterior end 56 of full-round spindle 42 is operably coupled to lock 
cylinder 40 such that rotation of a keyed member in lock cylinder 40 
rotates full-round spindle 42 causing slide 50 to move between the locked 
and unlocked state. The end of fullround spindle 42 opposite exterior end 
56 may be adapted to receive a lock turn mechanism operably associated 
with an interior knob assembly (not shown) of lockset mechanism 20 for 
manipulating slide 50 between the locked and unlocked state. 
Half-round spindle 44 is operably coupled to exterior sleeve 30 for 
co-rotation therewith. As best seen in FIG. 7, exterior sleeve 30 has a 
tab 58 projecting inwardly therefrom which is received within a slot 60 
formed in half-round spindle 44. In this manner, tab 58 axially positions 
and rotatably couples half-round spindle 44 with exterior sleeve 30. 
As previously indicated, lockset mechanism 20 is provided with an 
over-torque defense system which disables the lockset mechanism when an 
over-torque force has been applied thereto. In this regard, half-round 
spindle 44 is designed to fracture when an actuation torque has been 
applied to handle subassembly 22 which exceeds a maximum torque. More 
specifically, half-round spindle 44 may be provided with certain design 
features which initiate a fracture thereof when the maximum torque has 
been exceeded. For example, as best seen in FIGS. 8 and 9, a pair of 
notches 62 are formed at an end of half-round spindle 44 adjacent slot 60. 
Notches 62 locally reduce the cross-sectional area of half-round spindle 
44, as well as function as a stress riser to locate and control the 
failure mode of half-round spindle 44. As presently preferred, notches 62 
are formed at the edges of half-round spindle 44 and have a generally 
circular configuration. However, one skilled in the art will readily 
recognize that other stress risers may be adapted to the present invention 
to provide a particular failure mode of half-round spindle 44. 
Half-round spindle 44 may also be heat treated in a manner such that the 
hardness of the material, typically soft cold-rolled steel, is increased. 
In this regard, half-round spindle 44 may be heat treated in the presence 
of ammonia such that it becomes case hardened (from a hardness of 
approximately 60 RB to approximately 30-40 RC) and brittle. With the use 
of stress risers and surface hardening, alone or in combination, the 
failure mode of half-round spindle 44 at the maximum torque force may be 
precisely controlled. Presently maximum torque in the range of 220-270 
inchpounds is preferred and a maximum torque in the range of 240-250 
inch-pounds is more preferred to provide an adequate over-torque defense 
system. However, one skilled in the art will readily recognize that the 
precise maximum torque range may be a function of the particular design 
and application of the lockset mechanism. 
With reference again to FIG. 1-9, spindle subassembly 24 includes spring 
mechanism 64 operably coupled between rose liner 36 and torque spring 
mechanism 46 for urging spindle subassembly 24 axially away from exterior 
rose 32. Spring mechanism 64 includes spring seat 66 positioned adjacent 
the interior end 68 of exterior sleeve 30. A series of prongs 70 extend 
axially from exterior sleeve 30 and engage recesses 72 formed in spring 
seat 66. Conical coil spring 74 is operably disposed between spring seat 
66 and torque spring mechanism 46 to generate an axial biasing force. More 
specifically, coil spring 74 normally biases spindle subassembly 24 away 
from handle subassembly 22 such that when half-round spindle 44 fractures 
due to the application of an over-torque to handle subassembly 22, coil 
spring 74 forces full-round spindle 42 away from handle subassembly 22 and 
out of driving engagement with lock cylinder 40. Thus, full-round spindle 
42 is no longer in driving engagement with lock cylinder 40 and a portion 
of half-round spindle 44 and torsion spring mechanism 46 move axially away 
from handle subassembly 22 in the direction of arrow A shown in FIGS. 3 
and 5. As a result, when the over-torque condition is reached, spindle 
subassembly 24 is fully disabled. In this disabled state, handle 
subassembly 22 freely spins and the locking mechanism of lockset 20 is 
protected. While a conical coil spring is presently preferred, one skilled 
in the art will readily recognize that other biasing means such as a 
helical coil spring, a wave washer, a spring washer or other equivalent 
mechanisms for generating an axial biasing force may be utilized for 
urging spindle subassembly 24 away from handle subassembly 22. 
With reference now to FIGS. 10-12, a second preferred embodiment of the 
present invention is illustrated. Lockset mechanism 120 includes handle 
subassembly 122 and spindle subassembly 124 which is operably coupled to a 
latch bolt subassembly (not shown). Lockset mechanism 120 is particularly 
adapted to include a low-cost over-torque defense system similar to that 
incorporated in lockset mechanism 20 previously described. More 
specifically, spindle subassembly 124 includes full-round spindle 126 and 
half-round spindle 128 operably disposed within torque spring mechanism 
130 which includes torsion spring 132, locking slide members 134, 136 and 
torsion spring housing 138. Full-round spindle 126 is operably coupled to 
locking slide 136 such that rotation of full-round spindle 126 moves 
locking slide 136 in the transverse direction from an unlocked condition 
to a locked condition for inhibiting rotation of spindle subassembly 124 
to disable the latch bolt subassembly. Full-round spindle 126 is operably 
coupled at the end adjacent handle subassembly 122 to lock cylinder 140. 
Similarly, the interior end of full-round spindle 126 is operably coupled 
to a turn mechanism operably associated with the interior handle 
subassembly (not shown). 
Half-round spindle 128 is operably coupled to exterior handle subassembly 
122 for rotation therewith. More specifically, the exterior end of 
half-round spindle 128 is received within exterior sleeve 142. Insert 144 
having a complementary surface 146 to half-round spindle 128 is also 
inserted within exterior sleeve 142. A pair of radially extending details 
148 are formed on insert 144 and adapted to engage the edges of half-round 
spindle 128. Details 148 are also received within slot 150 formed in the 
end of exterior sleeve 142. In this manner, half-round spindle 128, 
exterior sleeve 142 and insert 144 are coupled together for co-rotation. 
As best seen in FIG. 12, exterior sleeve 142 has an inwardly extending tab 
152 formed thereon which is adapted to be received within slot 154 of 
half-round spindle 128. Similarly, tab 156 formed on exterior sleeve 142 
extends into groove 158 formed in insert 144. In this manner, details 148 
operably couple half-round spindle 128, exterior sleeve 142 and insert 144 
for co-rotation while tabs 152, 156 fix these components axially. 
As with half-round spindle 44 (of the first preferred embodiment), 
half-round spindle 128 is provided with certain design features which 
cause half-round spindle 128 to fracture when an over-torque force has 
been applied to lockset mechanism 120. More specifically, notches 160 are 
formed in the peripheral edges of half-round spindle 128 adjacent slot 
154. In addition, half-round spindle 128 may be heat treated to provide a 
desired range of hardness, thereby increasing its brittleness. In this 
manner, half-round spindle 128 is particularly adapted to fracture at a 
location adjacent notches 160 when the over-torque force is applied. 
With reference again to FIGS. 10 and 11, spindle subassembly 124 further 
includes spring mechanism 162 operably disposed between rose liner 164 and 
torsion spring mechanism 130 for biasing spindle subassembly 124 away from 
exterior handle subassembly 122. Spring mechanism 162 includes spring seat 
166 engaging an inner surface of rose liner 164 and helical coil spring 
168 operably disposed between spring seat 166 and torsion spring housing 
138. Upon application of a turning force greater than the maximum 
allowable torque (i.e. an over-torque force), half-round spindle 128 
fractures adjacent notches 160. Spring mechanism 162 urges full-round 
spindle 126 away from exterior handle subassembly 122 such that the 
exterior end thereof disengages lock cylinder 140, thereby disabling 
spindle subassembly 124. 
To ensure the smooth operation of lockset mechanism 120, spindle 
subassembly 124 is rotatably supported by rose liner 164 at a side 
opposite exterior handle subassembly 122. More specifically, rose shield 
170 extends axially inwardly from rose liner 164 and has a central 
aperture 172 formed therein which is adapted to receive bearing member 
174. Full-round spindle 126 and half-round spindle 128 extend through a 
central portion of bearing member 174 and are rotatably supported by rose 
shield 170. Support collar 176 and washer 178 are operably disposed 
between the exterior knob (not shown) of handle subassembly 122 and rose 
liner 164 for enhancing the relative rotation therebetween. As best seen 
in FIG. 11, handle subassembly 122 further includes spring member 180 
secured within exterior sleeve 142 and operably coupled to catch member 
182 for retaining and rotatably coupling a knob with exterior sleeve 142. 
While the present invention has been described with particular reference to 
preferred embodiments, one skilled in the art will readily recognize from 
the foregoing discussion and accompanying drawings and claims that various 
changes, modifications and variations can be made in the present invention 
without departing from the spirit and scope thereof as defined in the 
following claims.