Door handle modular return spring cage assembly

A modular return spring cage assembly for door lock handles, consists of a door lock mounting chassis member having two opposed faces, at least one face having two opposed arcuate channels forming a circular groove in the face. The groove has two split diametrically opposed spring bases each formed by two substantially equal spring stops projecting from radially outer and radially inner walls of the groove. Two compression springs are slidably disposed within the channels and have length such that a slight compression is required to fit the springs between the split spring bases. An arrangement for transmitting torsional motion between a door handle and the springs, and for limiting rotary motion of the handle is included. A provision for positively retaining the springs and the torsional motion transmission arrangement on the mounting chassis member completes the modular assembly. When so assembled, the spring cage module can be easily installed in or removed from a door preparation; and, because of its modularity, it may be designed to be reversible to provide enhanced tamper resistance.

BACKGROUND OF THE INVENTION 
This invention relates generally to door hardware and more particularly to 
an apparatus for supporting, guiding, and protecting door handle return 
springs and to simplify their installation on the door hardware. 
In response to the needs of the handicapped population and to the Americans 
with Disabilities Act (ADA) legislation, commercial building owners are 
required to provide locksets which can be operated by disabled persons. 
Most commonly, this is done by installing lever operated locksets in place 
of those with knob style handles. Levers can be easily pressed without 
grasping; they provide increased mechanical advantage; they generally 
require no power assist or power connections; and, in many cases, they can 
be substituted for knobs without changing the whole lockset. 
Most door locksets have decorative (or cosmetic) trim roses, surrounding 
the spindle of the handle, which conceal the inner mounting hardware and 
give the mounted lock a finished appearance. These are commonly fastened, 
by screws, spring clips and slots, or some combination thereof, to plates 
which form the external portions of the lockset mounting chassis. Within 
the chassis, in addition to the latch operating components, there is some 
arrangement of springs and levers for extending the latch and for 
returning the knob or handle to a resting (or parked) position. 
In knob operated cylindrical locksets, the latch return springs will 
usually suffice for also returning the knob. This is because the 
symmetrical shapes of knobs and their resulting balanced mass distribution 
only require the return springs to overcome friction within the lock 
mechanism. However, for the same lock equipped with lever handles, the 
springs also must overcome the lever overhang and the weight imbalance and 
may not be strong enough to prevent sagging and droop of the levers. This 
gives an unattractive appearance and indicates an inadequacy of design 
which must result in premature failure of the return springs. 
Part of the cause of this inadequacy is the space constraints within the 
door preparation and the mounting chassis which limit the radial extent of 
return levers and arms upon which the return springs must act. This 
results in low mechanical advantage for the return springs and, for any 
given spring size, limits the return force capacity. Thus, a heavy lever 
will begin to sag after a relatively short service life, due to weakening 
of the springs. Although very stiff springs could prevent lever sag, they 
cannot be applied to door levers because of the necessity for operability 
of the levers by children and handicapped persons. 
Finally, whatever lever return scheme is used, it must be reasonably simple 
to install so that labor costs for new installations and retrofits will 
not be unduly high. Many return spring systems are relatively complicated 
in that they include many parts, have limited space and access to the 
parts, and require a high degree of skill to install. Any new return 
spring system should, as a minimum, address the limitations enumerated 
above. This is important in order to enable building owners to upgrade 
existing buildings and to design new buildings for easy access in accord 
with the requirements of the ADA. Lever handles meet the requirements for 
accessibility, but they do not always provide the simplicity of structure 
and installation described as desirable above. 
The foregoing illustrates limitations known to exist in present door handle 
return spring systems for door locksets. It would clearly be advantageous 
to provide an alternative directed to overcoming one or more of the 
limitations set forth above. Accordingly, a suitable alternative is 
provided including features more fully disclosed hereinafter. 
SUMMARY OF THE INVENTION 
In one aspect of the present invention, this is accomplished by a modular 
return spring cage assembly for door lock handles, comprising a door lock 
mounting chassis member having two opposed faces, at least one face having 
two opposed arcuate channels forming a circular groove in the face, the 
groove having two split diametrically opposed spring bases each formed by 
two substantially equal spring stops projecting from radially outer and 
radially inner walls of the groove; two compression springs slidably 
disposed within the channels and having length such that a slight 
compression is required to fit the springs between the split spring bases; 
an arrangement for transmitting torsional motion between a door handle and 
the springs, and for limiting rotary motion of the handle; and means for 
retaining the springs and the means for transmitting torsional motion on 
the mounting chassis member. 
The foregoing and other aspects will become apparent from the following 
detailed description of the invention when considered in conjunction with 
the accompanying drawings.

DETAILED DESCRIPTION 
FIG. 1 shows a door handle 70 (in this case a lever) together with a driver 
60 for driving a spindle and a torque plate 40. The driver 60 is shown as 
a separate item from the handle 70, but it may be made as part of the 
handle 70 if desired. The handle/driver 70/60 operates together with the 
spring cage module 10 as described herein. The module 10 comprises a 
mounting chassis member 20 with two arcuate spring guide channels(25 in 
FIGS. 2 & 3), a pair of compression springs 30, a torque plate 40, and a 
fire plate 50. Driver 60 has slots 61 for engaging tabs 49 of torque plate 
40 for causing plate 40 to rotate with driver 60. 
Torque plate 40 has radially outwardly extending tabs 42 and axially 
extending tabs 41 for limiting rotary motion by striking the edges of 
limiter projections 22 of mounting chassis member 20, and for reaching 
into slots 21 of the circular groove to displace compression springs 30, 
respectively, whenever lever 70 and its driver 60 are turned. Slots 21 are 
formed by the spring stops ("a" & "b" in FIGS. 2 & 4) projecting radially 
outwardly and radially inwardly from the inner and outer walls of the 
channels (25 in FIGS. 2 & 3). A fire plate 50 is shown, also. This 
prevents flame travel through the lock from one side to the other, in the 
event of a fire; but it also may be used to retain the torque plate 40 and 
compression springs 30 in proper alignment against mounting chassis member 
20 without interfering with their motion during operation of the door 
lock. This is the preferred method for such retention, but it would also 
be feasible to provide the same function with any of a number of well 
known torque plate retention means (not illustrated) which would still 
permit unimpeded rotation of the torque plate. 
FIG. 2 shows a front view of the mounting chassis member 20. In this case, 
front refers to the side of member 20 which faces outwardly from the door. 
It should be noted that, because of its modular design, the present 
invention could as well be reversed so that the view of FIG. 2 would be a 
rear view instead. One advantage of the reversed embodiment is that the 
back side of the mounting chassis member 20 may be designed to present a 
flat and solid surface which has an enhanced resistance to tampering and 
damage when installed. The method of attachment of the mounting housing 
member 20 to the lockset and the door is not illustrated or discussed in 
detail; because such attachment schemes are well known in the art, and any 
of such schemes may be used. However, for the highest strength and 
security, the preferred attachment method uses through bolts between 
mounting chassis members on both sides of the door, the bolts passing 
through the door outside the door lock preparation cavity. In addition, 
castellated nuts are threaded onto both sides of the spindle housing which 
projects from the lock housing through the spindle ports 100 of chassis 
members 20 on both sides of the door. The result is a very strong lock 
assembly installation. 
The preferred embodiment of the module 10 can be best understood by 
reference to FIGS. 1-5, as different features are apparent in each Figure. 
Mounting chassis member 20 is a disc-like body with a circular groove on 
at least one side formed by two channels 25 connected by two slots 21 in 
two diametrically opposed spring bases defined by spring stops "a" and "b" 
projecting from the walls of channels 25. Member 20 has a first surface 27 
on one face and a second surface 29 on an opposite face. A third surface 
26 bounds channels 25 and is recessed below first surface 27. Two 
diametrically opposed limiter projections 22 are coplanar with first 
surface 27 and obstruct an outer portion of third surface 26 to provide 
bi-directional limits to rotary motion of torque plate 40 along third 
surface 26. Edges "c" of limiter projections 22 act as stops against which 
tabs 42 of torque plate 40 strike when the rotational limit is reached. 
The two diametrically opposed tabs 41 of torque plate 40 extend axially 
from the torque plate into slots 21 of chassis member 20. When the torque 
plate 40 is rotated in either direction, tabs 21 compress springs 30, and, 
when released, the springs 30 return the torque plate 40 to its resting 
position by pushing tabs 41 back into slots 21. Using two springs 30 
provides the advantage of doubling the return force available to prevent 
sagging of the handle 70, of halving the wear and tear on the return 
compression springs 30, of permitting use of stronger springs, and of 
providing redundancy to permit continued operation even if one of the 
springs 30 fails. This allows repairs to be made without waiting for 
complete failure of the return function. Torque plate 40 rotates in 
response to rotation of driver 60 by means of tabs 49 which engage with 
slots 61 of the driver member. Thus, when the handle 70 is turned, driver 
60 turns causing torque plate 40 to turn and springs 30 to be compressed. 
When the handle is released, the springs 30 expand, push against tabs 41 
to return the torque plate 40 to its resting position with tabs 41 in 
slots 21. This returns driver 60 and handle 70 to their resting position 
by means of the rotary interaction of tabs 49 with slots 61. 
Chassis member 20 also has a spindle port 100 at its center for accepting a 
spindle housing. A fourth surface 101 surrounds port 100 and is bounded by 
a cylindrical wall 23, which acts as a support and guide for rotary motion 
of driver 60 and handle 70. Outer surface 63 of driver 60 receives rotary 
bearing support from wall 23 surrounding surface 101 of chassis member 20. 
Fire plate 50 is the preferred means for retaining all components in their 
modular package; because it prevents flame travel through the door lock 
and door preparation cavity while providing a low friction retention 
surface against which torque plate 40 can rotate. The springs 30 are 
retained by torque plate 40. The fire plate 50 is secured to chassis 
member 20 against surface 27 by placing slots 58 over projections 80 of 
chassis member 20 and expanding or staking the projections to secure the 
plate to the member. This attachment could also be made by threaded 
fasteners, tongue and groove turnlocks, riveting, welding, or other known 
joining techniques; but, because of its simplicity, staking is preferred. 
Other retention devices could be used, such as a plurality of separate low 
friction torque plate hold down tabs, arrayed around the edge of chassis 
member 20, or an overhanging lip formed on the inner edge of surface 27 of 
chassis member 20. In such cases, the fire plate 50 is not needed as long 
as chassis member 20 is designed with no direct flame paths. 
Once assembled, the door handle modular return spring cage assembly is 
compact, durable, damage resistant, and, because of these properties, it 
is easy to handle and to install. The modular assembly may also include 
mounting provisions for trim roses or other ornamental devices.