Releasable locking mechanism

A plurality of arms extend outwardly from an accessory structure and are adapted to engage slots in a base structure to which the accessory structure is to be mounted. The arms are normally biased to a position at which they are freely insertable an removable from the slots in the base structure, and movable to a position at which the arms are locked in the slots in response to forcedly maintaining the arms at a spaced apart distance greater than the distance of which the arms are disposed in the normally biased position. The arms are returned to their normally biased position in response to depressing an actuator mounted in the accessory structure, and moved to the spaced apart locking position in response to releasing the actuator. The problems of fatigue failure, wear, breakage and decrease of positive retention between accessory and base structures using current releasable locking mechanisms is overcome.

BACKGROUND OF THE INVENTION 
1. Technical Field 
This invention relates generally to a locking mechanism for mechanically 
securing two components together, and more specifically to such a locking 
mechanism that is particularly suitable for locking an accessory device 
onto a portable telecommunication instrument. 
2. History of Related Art 
Several arrangements are used for locking accessory devices, such as 
battery chargers, power supply adapters, hands-free operation adapters, 
and the like to a base structure, such as a radiotelephone. The locking 
mechanisms are generally provided on the accessory structure, and 
typically include one or more molded plastic arms that engage a mating 
feature on the base structure. The plastic arms are deflected by a user to 
remove or insert the arms into a mating feature on the base structure, and 
thereby disconnect or attach the accessory device to the base structure. 
When the deflecting force applied by the user to the arms is released, the 
arms spring outwardly thereby secure the accessory device to the base 
member. 
Such molded plastic arm configurations do not hold up well when subjected 
to repeated deflection, eventually resulting in a loose fit and even 
breakage of the plastic arm. This problem results in a limited life cycle 
for the accessory device. Repair of the plastic arms generally requires 
disassembly of the accessory adapter at a service center. Often repair 
costs exceed the cost of purchasing a new accessory. Also, such 
deflectable arm locking mechanisms have heretofore been cumbersome to 
operate because deflection of the arms is generally accomplished by 
squeezing two arms toward each other to remove or attach the accessory 
device. This operation may be difficult for a person having limited manual 
dexterity. 
Other methods currently used to attach an accessory device to a base 
structure include press-fit designs which typically require significant 
insertion force. Such press-fit designs are subject to high early wear 
rates, and are often difficult to secure for proper electrical connection 
and remove for subsequent disconnection from the mating structure. 
The present invention is directed to overcoming the problems set forth 
above. It is desirable to have a simple, easy-to-use, locking mechanism 
for attaching an accessory structure to a base structure. It is also 
desirable to have such a locking mechanism that is releasable in response 
to depressing a single button which provides positive, tactile feedback to 
the user. It is also desirable to have such a releasable locking mechanism 
in which the locking arms are minimally stressed and will withstand 
repeated deflection over the life of the accessory device. 
SUMMARY OF THE INVENTION 
In accordance with one aspect of the present invention, a releasable 
locking mechanism for attaching an accessory structure to a base structure 
having at least two spaced apart slots extending through a wall of the 
base structure housing, comprises at least two arms extending outwardly 
from a surface of the accessory structure. The arms are normally biased to 
a position at which the arms are readily insertable and removable from the 
slots in the base structure, and are moveable to a position at which the 
arms are locked in the slots in response to forcedly maintaining the arms 
at a spaced apart distance greater than the distance at which the arms are 
disposed when at their normally biased position. 
Other features of the releasable locking mechanism embodying the present 
invention include the arms being leaf springs, preferably formed of spring 
steel. Each of the leaf springs has a distal end that extends outwardly 
from a first wall of the accessory structure housing and is adapted to 
engage a respective one of the slots extending through the base structure 
housing wall. Additional features include the releasable locking mechanism 
having at least two elongated pins disposed in the accessory structure 
housing that are moveable along a longitudinal axis of the pins. Each of 
the pins have a first end disposed adjacent a respective one of the arms 
and a second end that is biased toward a predefined position within the 
accessory housing by a respective one of the arms. 
Still other features include an actuator having a first end portion that is 
extendable through an aperture in a second wall of the accessory structure 
housing, a second end portion biasedly maintained at a position in 
abutment with each of the second ends of the elongated pins, and an 
intermediate portion between the first and second portions. The second and 
intermediate portions of the actuator have separately defined thicknesses, 
wherein the thickness of the second end portion is greater than the 
thickness of the intermediate portion. The actuator is movable from the 
biased position to a depressed position at which the intermediate portion 
of the actuator is aligned with the second ends of the elongated pins, and 
at which the second ends of the pins are urged into biased abutment with 
the intermediate portion of the actuator when the arms are at their 
normally biased release position. 
Other features of the releasable locking mechanism include the base 
structure being the transceiver unit of a portable telecommunication 
instrument, and the accessory structure being a battery pack or auxiliary 
power supply adaptor arranged for interconnection with the transceiver 
unit. 
The releasable locking mechanism further includes a means for maintaining 
the actuator at the biased position. 
Other features of the releasable locking mechanism embodying the present 
invention include the distal ends of the leaf springs having an L-shaped 
flange extending in a transverse direction to the spring whereby the 
L-shaped flange is moved laterally into engagement with an interior 
surface of the wall of the base structure housing in response to the 
actuator button being at the biased position. Other feature of the leaf 
springs include the leaf springs being the legs of a U-shaped clip in 
which a base portion of the clip extends between respectively spaced apart 
second ends of the leaf springs. 
Still other features of the releasable locking mechanism include the 
actuator having a tapered transition region disposed between the second 
and intermediate portions of the actuator, and the means for maintaining 
the actuator at the biased position being a coil spring disposed in biased 
abutment against the second end portion of the actuator.

DETAILED DESCRIPTION OF PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS 
The releasable locking mechanism embodying the present invention is 
particularly suitable for attaching an accessory device, such as a battery 
pack, battery recharging adaptor, auxiliary power supply, hands-free 
operation adaptors and the like, to portable telecommunication instruments 
such as cellular telephones and similar portable radiotelephones. 
In a preferred exemplary embodiment of the present invention, a releasable 
locking mechanism 10 is disposed within an accessory structure 12, adapted 
for attachment to a base structure 14. As shown in FIG. 2, the accessory 
structure 12 has surface-mounted contact features 17 represented by a 
rectangular area, and disposed on a face arranged to abut the base 
structure 14 and establish electrical contact with mating features 16 
provided on the abutting face of the base structure 14, as also 
represented by a rectangular area as shown in FIG. 1. The mating features 
16,17 typically are electrically conductive contact pads or, 
alternatively, sockets or pins arranged in a pattern to mate with 
cooperating sockets or pins mounted on the adjoining structure. In the 
exemplary embodiment, the accessory structure 12 has a coiled cable 
assembly 18 that extends between the mating features 17 on the face of the 
accessory structure 12 and an adaptor 20 that is arranged for plugging 
into an auxiliary power source, such as the cigarette lighter socket on a 
vehicle. 
The accessory structure 12 has a housing 22 which has a front portion 24 
and a rear portion 26. As best shown in FIG. 2, the electrical 
interconnection features 17 of the accessory structure 12 are mounted on a 
first surface of the housing 22 which is provided by a face panel of the 
rear portion 26 of the accessory structure housing 22. As shown in FIG. 1, 
the electrically mating features 16 on the base structure 14 are 
positioned on a wall 28 of the base structure 14 which abuts the accessory 
structure 12 when the accessory structure 12 is connected to the base 
structure 14. As shown in FIG. 1, the wall 28 of the base structure 14 
also has a pair of spaced apart slots 30 formed therein that, is described 
below in greater detail are positioned to receive respective outwardly 
extending arms of the accessory structure 12. 
In the preferred embodiment of the releasable locking mechanism 10, the 
arms that extend outwardly from the accessory structure 12 and engage the 
slots 30 in the base structure 14, are leaf springs 32 that are mounted 
substantially within the accessory structure 12. Desirably, the leaf 
springs 32 are, as shown in FIG. 2, the legs of a generally U-shaped clip 
that has a base portion 34 extending between the lower ends of the 
upwardly extending legs 32. The metal clip, including the leg portions 
that form the leaf springs 32, is preferably formed of a flexible metallic 
material, such as spring steel. The metal clip is substantially enclosed 
within the accessory structure housing 22 with the exception of a distal 
end portion 36 formed at each outer end of the leaf springs 32. Each of 
the distal end portions 36 extend outwardly from the mating face wall of 
the housing 22 of the accessory structure 12 and are adapted to engage a 
respective one of the slots 30 formed in the base structure housing wall 
28. More specifically, as shown in FIGS. 2-4, the distal end portions 36 
of the leaf springs 32 have an L-shaped flange 38, or alternatively a 
curved hook, extending in a direction transverse to the respective leaf 
spring 32. As will be described below in greater detail, when the L-shaped 
flanges 38 are moved laterally in a direction away from each other, each 
of the flanges 38 engage an interior surface of the base structure wall 28 
adjacent a respective slot 30. The distal end portions 36 of the leaf 
springs 32 are normally biased i.e., in the free state without any applied 
external force, toward a release position at which of the flanges 38 are 
not engaged with the internal surface of the base structure wall 28, and 
the distal end portions 36 can be withdrawn from the respective slots 30. 
The leaf springs 32 are also movable, as described below in greater 
detail, toward a locking position at which of the distal ends 36 are 
forcedly retained within a respective one of the slots 30 formed in the 
base structure wall 28. 
The releasable locking mechanism 10 further includes a pair of elongated 
pins 40 that are slidably disposed within the accessory structure housing 
22 and movable along a longitudinal axis 42 of the pins 40. As best shown 
in FIGS. 3 and 4, each of the pins 40 has a first end 44 that abuts a 
respective one of the leaf springs 32 and a second end 46 that is spaced 
from the first end 44. The pins 40 are biased inwardly toward the center 
of the accessory structure 12 so that the second end 46 of each of the 
pins 40 is biased toward a predefined position, as described below, within 
the accessory structure housing 22. 
The releasable locking mechanism 10 embodying the present invention further 
includes an actuator 48 having a first end portion 50 that extends through 
a second wall of the housing, formed in the front portion 24 of the 
housing 22 as shown in FIG. 2, a second end portion 52, and an 
intermediate portion 54 disposed between the first and second end portions 
50,52. A coil spring 56, positioned between the second end portion 52 of 
the actuator 48 and an internal wall surface of the rear portion 26 of the 
housing 22, provides a means for maintaining the actuator 48 at a biased 
position at which the first portion 50 of the actuator 48 extends through 
the front portion 24 of the housing 22. Moreover, when in the biased 
position, the second ends 46 of the pins 40 are biasedly maintained, by 
the leaf springs 32 which are deflected outwardly from their normal biased 
position, in abutment with the second end portion 52 of the actuator 48. 
When the actuator 48 is depressed, as a result of applying finger pressure 
against the first end portion 50 of the actuator 48, the actuator 48 moves 
against the bias force of the coil spring 56 to a depressed position at 
which the intermediate portion 54 of the actuator 48 is aligned with the 
longitudinal axes 42 of the elongated pins 40 and the second ends 46 of 
the pins 40 are urged into biased abutment, by the leaf springs 32 to the 
above-discussed predefined position against the intermediate portion 54 of 
the actuator 48. 
As illustrated in the drawings, the intermediate portion 54 may comprise a 
tapered section that angles inwardly from the thicker second end portion 
52, toward the first end portion 50 of the actuator 48. Importantly, when 
the actuator 48 is moved to the depressed position as shown in FIG. 4, the 
pins 40 move inwardly, under the influence of the leaf springs 32, so that 
the leaf springs 32 are at their normal biased position whereat the distal 
end portions 36 are spaced closer to each other. When at their normal 
biased position, the distal end portions 36 of the leaf springs and may be 
withdrawn from locking engagement with the base structure 14 by simply 
withdrawing the end portions 36 from the slots 30 formed in the wall 28 of 
the base structure 14. 
In like manner, the accessory structure 12 can be attached to the base 
structure 14 by depressing the first end portion 50 of the actuator 40, 
thereby moving the actuator 48 to the depressed position, whereat the 
second ends 46 of the pins are at the predefined position in abutment with 
the intermediate portion 54 of the actuator 48. When pressure on the first 
end portion 50 of the actuator 48 is released, the coil spring 56 moves 
the actuator 48 to the biased position shown in FIG. 3, at which the 
second ends 46 of the elongated pins 40 are in biased abutment with the 
second end portion 52 of the actuator 48. 
In an alternative embodiment illustrated in FIGS. 5 and 6, the releasable 
locking mechanism 10 embodying the present invention is specifically 
adapted to provide retention of a battery pack 58 in the transceiver 
portion 60 of a cellular telephone. In this embodiment, the distal end 
portions 36 of the leaf springs 52 are urged outwardly, by the second end 
portion 52 of the actuator 48 and the intervening pins 40, into slots 62 
formed in an internal wall surface 64 of the transceiver 60. In this 
embodiment, the first end portion 50 of the actuator 48 is positioned on 
an end face of the battery pack 58. When the first end portion 50 is 
depressed, the actuator 48 is moved to the depressed position and the pins 
40 move inwardly, as described above, permitting the leaf springs 32 to 
return to their normal biased position at which the end portions 36 of the 
leaf springs 32 are disengaged from the slots 62 in the internal wall 
surface 64 of the transceiver 60. This permits the battery pack 58 to be 
separated from the transceiver portion 60, and recharged or replaced. 
Thus, it can be seen that the releasable mechanism embodying the present 
invention is in its "active", or locking, position in the absence of any 
external force upon the actuator 48. When at the active position, the 
elongated pins 40 are at their maximum spaced apart distance because of 
their respective interface with the thicker second end portion 52 of the 
actuator 48. The elongated pins 40 also interface with the leaf springs 32 
and force deflection of the leaf springs 32 in an outward direction away 
from each other. At this position, the leaf springs 32 are deflected from 
the normal position and the distal end portions 36 are correspondingly 
spaced at a maximum distance from one another. 
When external pressure is placed on the first end portion 50 of the 
actuator 48, as illustrated in FIG. 6, the actuator 48 is depressed 
inwardly and the second ends 46 of the elongated pins 40 engage the 
reduced thickness intermediate portion 54 of the actuator 48. This allows 
the elongated pins 40 to move inwardly toward each other and allows the 
leaf spring 32 to return to a normally biased position whereat the leaf 
springs 32 exert minimal force against the pins 40. To attach the 
accessory structure 12 to the base structure 14, the accessory structure 
12 is aligned with the base structure 14. With the mating features 16 and 
17 in their respective desired alignment, and the external force on a 
second end portion 50 of the actuator 48 removed. The actuator 48 is then 
moved to its normally biased position be the force imposed by the coil 
spring 56, and the leaf springs 32 are deflected outwardly by the pins 40 
so that the distal end portions 36 of the leaf springs 32 extend into the 
slots 30 and are captured within the base structure 14. The accessory 
structure 12 is thus securely attached to the base structure 14, and is 
maintained in secured attachment during use, but can be readily released 
when desired by simply depressing the first end portion of the actuator 
48. 
Although the present invention is described in terms of preferred exemplary 
embodiments, and specific examples given of base and accessory units that 
may be interconnected using the releasable locking mechanism described and 
claimed herein, those skilled in the art will recognize the changes in 
those components, and in the specific arrangement of the accessory and 
base components, may be made without departing from the spirit of the 
invention. Such changes are intended to fall within the scope of the 
following claims. Other aspects, features and advantages of the present 
invention may be obtained from the study of this disclosure and the 
drawings, along with the appended claims.