Keypad assembly using a lead screw assembly for moving a curved member

An apparatus for moving a member between a retracted position and an extended position includes a housing, a movement mechanism, a linear lead screw, a first carriage, and a second carriage. The housing has a curved path between the retracted position and the extended position. The lead screw has a longitudinal axis and threads. The movement mechanism is coupled to the lead screw to rotate the lead screw about the longitudinal axis. The first carriage has a connecting structure and a bore with threads that mate with the threads of the lead screw to move the carriage linearly along the longitudinal axis of the lead screw when the lead screw rotates. The second carriage is coupled to the member and has a connecting structure. The connecting structure of the second carriage operatively couples with the connecting structure of the first carriage to permit lateral and rotational displacement such that the member is moved through the curved path between the retracted position and the extended position as the first carriage moves linearly along the longitudinal axis of the lead screw.

FIELD OF THE INVENTION 
This invention relates to keypad assemblies and lead screws, and, in 
particular embodiments, to a keypad assembly using a lead screw assembly 
to extend and retract a curved TDD keypad for an emergency call box. 
BACKGROUND OF THE INVENTION 
Traditionally, a user can utilize an emergency call box to communicate with 
an emergency dispatch operator using voice communication. Generally, 
emergency call boxes have not been provided with Telecommunications 
Devices for the Deaf (TDD) or Text Telephony (TTY) capability. Thus, a 
user who is deaf, hearing-impaired, or speech-impaired may not be able to 
communicate with an emergency dispatch operator. The difficulties 
experienced by a hearing-impaired user are also aggravated by the fact 
that many emergency call boxes are located in extremely noisy roadside 
environments. 
To overcome these drawbacks, emergency call boxes with TDD or TTY 
capability have been developed. Call boxes have been equipped with a TDD 
keypad that is permanently attached on the outside of the call box to 
enable a user to bidirectionally communicate with an emergency dispatch 
operator without the need for voice communication. However, these keypads 
are vulnerable to damage due to harsh environments. In addition, vandalism 
of these keypads poses a major problem. 
To overcome these drawbacks, emergency call boxes with a keypad contained 
within the call box or with a retractable keypad assembly attached outside 
of the call box have been developed. However, these keypads are flat and 
located in a non-ergonomic position, thus hindering use by persons of 
various heights and in wheelchairs. 
Traditionally, lead screws have been used to extend and retract flat trays 
or other members in a linear direction parallel to the axis of the lead 
screw. However, flat trays, even if not deployed horizontal to the ground, 
are not ergonomically adapted for a person's use. Therefore, traditional 
lead screws are unable to deploy an ergonomic tray to an ergonomic 
position in order to accommodate use by persons of various heights and in 
wheelchairs. 
SUMMARY OF THE DISCLOSURE 
It is an object of an embodiment of the present invention to provide an 
improved keypad assembly and an improved lead screw assembly, which 
obviate for practical purposes, the above mentioned limitations. 
According to an embodiment of the present invention, an apparatus for 
moving a member between a retracted position and an extended position 
includes a housing, a movement mechanism, a linear lead screw, a first 
carriage, and a second carriage. The housing has a curved path between the 
retracted position and the extended position. The lead screw has a 
longitudinal axis and threads. The movement mechanism is coupled to the 
lead screw to rotate the lead screw about the longitudinal axis. The first 
carriage has a connecting structure and a bore with threads that mate with 
the threads of the lead screw to move the carriage linearly along the 
longitudinal axis of the lead screw when the lead screw rotates. The 
second carriage is coupled to the member and has a connecting structure. 
The connecting structure of the second carriage operatively couples with 
the connecting structure of the first carriage to permit lateral and 
rotational displacement such that the member is moved through the curved 
path between the retracted position and the extended position as the first 
carriage moves linearly along the longitudinal axis of the lead screw. 
In particular embodiments of the present invention, the apparatus for 
moving the member between the retracted position and the extended position 
further includes a set of tracks engaging the member. The member glides 
along the set of tracks as the member is moved between the retracted 
position and the extended position. Other embodiments of the present 
invention include a plurality of position sensors coupled to the housing 
for determining when the member is in the retracted position and when the 
member is in the extended position. 
In further embodiments, the member includes a curved keypad that is a 
membrane-type and a curved keypad plate that is coupled to the curved 
keypad. The curved keypad plate and the curved keypad curve downward to an 
ergonomic position when the curved keypad plate and the curved keypad are 
in the extended position. In additional embodiments, the movement 
mechanism includes a motor and a pulley coupled to the motor to provide 
rotary motion. 
Other features and advantages of the invention will become apparent from 
the following detailed description, taken in conjunction with the 
accompanying drawings which illustrate, by way of example, various 
features of embodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As shown in the drawings for purposes of illustration, the invention is 
embodied in a keypad assembly and a lead screw assembly. In preferred 
embodiments of the present invention, the keypad assembly is attached to 
an emergency call box, and the keypad assembly utilizes the lead screw 
assembly to move a curved keypad plate and a curved TDD keypad from a 
retracted position, through a curved path, to an extended position. This 
allows users of various heights and in wheelchairs to utilize the TDD 
keypad to bidirectionally communicate with an emergency dispatch operator 
without the need for voice communication. However, it will be recognized 
that further embodiments of the invention may be included in other devices 
that have TDD or TTY capability or may be used in other devices that 
extend and retract a curved member. In alternative embodiments, the keypad 
assembly may be deployed from other devices, such as telephones, 
computers, kiosks, karaoke machines, or the like. In further alternative 
embodiments, the lead screw assembly may be used in other devices, such as 
a display case, to extend and retract other curved members, such as a 
frame of the display case. In additional embodiments, the keypad assembly 
may include other input devices that are curved, such as a standard 
keyboard, an I/O keypad, a track ball, a touch screen, or the like. 
FIGS. 1 and 2a illustrate a top plan and partial cut-away view of a keypad 
assembly 12, with a keypad plate 14 and a keypad 16 in a retracted 
position, in accordance with an embodiment of the present invention. In 
the illustrated embodiment, a keypad assembly 12 is formed from a housing 
48 containing a curved keypad plate 14, a curved keypad 16, a movement 
mechanism 10, a lead screw assembly 22, and two position sensors 24 and 
26. In one embodiment, the movement mechanism 10 includes an electric 
motor 18 and a pulley 20. However, in alternative embodiments, the 
movement mechanism may include other parts, such as a gear, a spring, or 
the like. In one embodiment, the motor 18 is a rotating DC motor. However, 
in alternative embodiments, the motor 18 may be a stepping motor or the 
like. 
The lead screw assembly 22 includes a linear lead screw 28, an articulating 
drive nut 30, and a slider 32. The lead screw 28 has a longitudinal axis 
and threads. In one embodiment, the lead screw 28 is made of stainless 
steel that is passivated and then finished with teflon coating. However, 
in alternative embodiments, the lead screw 28 may be made of other 
suitable materials, such as plastic, ceramic, metal, composites, or the 
like. In further alternative embodiments, the lead screw 28 may be formed 
out of other configurations, using a belt, a chain, a spring, or the like, 
to move the drive nut 30. However, the lead screw 28 is preferred because 
the lead screw 28 more effectively resists the keypad plate 14 and the 
keypad 16 being pulled out to an extended position when not being driven, 
and thus tends to protect the keypad plate 14 and the keypad 16 from 
vandalism. 
In the embodiment illustrated in FIG. 1, the pulley 20 is coupled to the 
motor 18 to provide rotary motion. Referring to FIGS. 8a and 8b, the motor 
18 has a bore spacer 110 that is inserted into the pulley 20 to secure the 
motor 18 to the pulley 20. In the embodiment illustrated in FIG. 1, the 
pulley 20 is also coupled to the lead screw 28 to rotate the lead screw 28 
about the longitudinal axis of the lead screw 28. In alternative 
embodiments, the pulley 20 may be a gear, or the like, that is coupled to 
corresponding gears, or the like, on the motor 18 and the lead screw 28. 
Referring to FIGS. 2a-2c, 6a, and 6b, the drive nut 30 contains a magnet 44 
that is pressed flush into a slot in the drive nut 30. Referring to FIG. 
1, the position sensors 24 and 26 are reed switches that are activated by 
the magnet 44 in the drive nut 30. The position sensors 24 and 26 are 
coupled to the housing 48 for determining when the keypad plate 14 and the 
keypad 16 are in a retracted position and an extended position. 
FIGS. 2a-2c show partial cross-sectional views of the keypad assembly 12 
along the line 2--2 as shown in FIG. 1. In preferred embodiments, the 
housing 48 has a curved path between the retracted position and the 
extended position. The keypad plate 14 is engaged in a set of tracks 40 
and glides along the set of tracks 40 as it moves between the retracted 
position and the extended position. The drive nut 30 has a connecting 
structure and a bore with threads that mate with the corresponding threads 
of the lead screw 28 to move the drive nut 30 linearly along the 
longitudinal axis of the lead screw 28 when the lead screw 28 rotates. The 
slider 32 is attached underneath the keypad plate 14 using fasteners, such 
as screws, bolts, nails, rivets, or the like. The slider 32 also has a 
connecting structure that operatively couples with the connecting 
structure of the drive nut 30 to permit lateral and rotational movement of 
the slider 32 perpendicular to the longitudinal axis of the lead screw 28 
such that the keypad plate 14 and the keypad 16 are moved through the 
curved path between the retracted position and the extended position as 
the drive nut 30 moves linearly along the longitudinal axis of the lead 
screw 28 and the keypad plate 14 glides along the set of tracks 40. 
Referring to FIGS. 2a-2c and 5-6b, the connecting structure of the drive 
nut 30 is a protruding knob 42. Referring to FIGS. 2a-2c, 7a, and 7b, the 
connecting structure of the slider 32 is a receiving recess 46. Referring 
to FIGS. 2a-2c, the receiving recess 46 of the slider 32 loosely couples 
with the protruding knob 42 of the drive nut 30 to permit lateral and 
rotational movement of the slider 32 perpendicular to the longitudinal 
axis of the lead screw 28 such that the keypad plate 14 and the keypad 16 
are moved through the curved path between the retracted position and the 
extended position as the drive nut 30 moves linearly along the 
longitudinal axis of the lead screw 28 and the keypad plate 14 glides 
along the set of tracks 40. 
The protruding knob 42 of the drive nut 30 and the receiving recess 46 of 
the slider 32 shown in FIGS. 2a-2c are preferred because the knob 42 and 
the recess 46 have smooth, rounded surfaces that are unlikely to "catch" 
and hinder movement of the keypad plate 14 and the keypad 16 between the 
retracted position and the extended position. However, in alternative 
embodiments, the drive nut 30 may have other protruding structures, such 
as a triangular pivot, a rectangular post, or the like, and the slider 32 
may have other receiving structures that correspond with the protruding 
structure of the drive nut 30, such as a triangular trough, a rectangular 
slot, or the like. In further alternative embodiments, the connecting 
structures of the drive nut 30 and the slider 32 may be switched, so that 
the drive nut 30 has the receiving recess or other receiving structure, 
and the slider 32 has the protruding knob or other protruding structure. 
In the illustrated embodiment, when the keypad plate 14 and the keypad 16 
are in the retracted position, the distance between the top of the 
protruding knob 42 of the drive nut 30 and the bottom of the receiving 
recess 46 of the slider 32 is at a minimum value, as illustrated in FIG. 
2a. As the drive nut 30 moves linearly along the longitudinal axis of the 
lead screw 28 and the keypad plate 14 glides along the set of tracks 40, 
the receiving recess 46 of the slider 32 rotates about the protruding knob 
42 of the drive nut 30. In addition, the distance between the top of the 
protruding knob 42 of the drive nut 30 and the bottom of the receiving 
recess 46 of the slider 32 increases, reaching a maximum value when the 
keypad plate 14 and the keypad 16 are at the apex of their curved path of 
movement, as illustrated in FIG. 2b. The distance between the top of the 
protruding knob 42 of the drive nut 30 and the bottom of the receiving 
recess 46 of the slider 32 then decreases again as the drive nut 30 
continues to move linearly along the longitudinal axis of the lead screw 
28, reaching another minimum value when the keypad plate 14 and the keypad 
16 are in the extended position, as illustrated in FIG. 2c. Also, the 
keypad plate 14 continues to glide along the set of tracks 40 and the 
receiving recess 46 of the slider 32 continues to rotate about the 
protruding knob 42 of the drive nut 30. 
FIG. 3 shows a perspective view of the keypad assembly 12 attached to an 
emergency call box 50, with the keypad plate 14 and the keypad 16 in the 
extended position, in accordance with an embodiment of the present 
invention. An emergency call box 50 is formed from a housing 52 that is 
attached to a road standard 54 with fasteners, such as screws, bolts, 
nails, rivets, or the like. The housing 52 includes a door 56 that opens 
to expose a standard telephone handset 58 attached to an armored cable 60, 
a display 62, and push button selection switches 64, 66, and 68. The 
housing 52 also includes current sense circuitry (not shown) that controls 
the motor 18. The keypad assembly 12 is attached underneath the housing 52 
with fasteners, such as screws, bolts, nails, rivets, or the like. A 
detailed example of an emergency call box and a method of controlling the 
emergency call box in TDD mode are disclosed in pending U.S. patent 
application Ser. No. 08/743,952, filed Oct. 30, 1996, which is 
incorporated herein by reference. 
FIG. 4 illustrates a partial perspective view of the keypad assembly 12 
attached to the emergency call box 50, with the keypad plate 14 and the 
keypad 16 in the extended position, in accordance with an embodiment of 
the present invention. More specifically, FIG. 4 shows the curvature of 
the keypad plate 14 and the keypad 16. Referring to FIGS. 1-4, when a user 
opens the door 56 of the emergency call box 50 to place an emergency call 
to an emergency dispatch operator, the user is prompted for a Yes/No 
response to the choice of "TTY" or "Phone." If the user selects "TTY," the 
user is prompted with a series of questions. The motor 18 then 
automatically turns on, and the keypad plate 14 and the keypad 16 are 
moved from the retracted position to the extended position. In alternative 
embodiments, the motor 18 may be turned on by other actions, such as 
opening the door 56 of the emergency call box 50 or pushing an activation 
button on the emergency call box 50. 
When the magnet 44 in the drive nut 30 is in the proximity of the position 
sensor 26, the magnet 44 activates the position sensor 26, and the 
position sensor 26 signals the current sense circuitry in the emergency 
call box housing 52 to drop voltage to the motor 18. Dropping the voltage 
to the motor 18 slows down the rotation of the lead screw 28, thus 
preventing the lead screw 28 and the drive nut 30 from locking up and 
jamming. When the keypad plate 14 and the keypad 16 are in the extended 
position, the slider 32 stops against the housing 48 of the keypad 
assembly 12, as shown in FIG. 2c. This drives up current on the circuitry 
in the emergency call box housing 52, and the circuitry then shuts off a 
relay to the motor 18, thus shutting down the motor 18. If the keypad 
plate 14 and the keypad 16 are unable to move completely out to the 
extended position, the magnet 44 in the drive nut 30 does not activate the 
position sensor 26. This drives up current on the circuitry in the 
emergency call box housing 52, and the motor 18 then reverses, thus 
returning the keypad plate 14 and the keypad 16 to the retracted position. 
In preferred embodiments, when the keypad plate 14 and the keypad 16 are in 
the extended position, the keypad plate 14 and the keypad 16 are curved at 
a downward angle to an ergonomic height to accommodate use by persons of 
various heights and in wheelchairs, as illustrated in FIGS. 2c and 4. The 
ergonomics of the height and the angle of the keypad plate 14 and the 
keypad 16 comply with the guidelines defined in the book "Human Scale 
1/2/3." In preferred embodiments, the keypad plate 14 and the keypad 16 
are positioned at a height of about 36 inches (about 91 centimeters) from 
ground level and curve at a downward angle of about 20 degrees. However, 
in alternative embodiments, the keypad plate 14 and the keypad 16 may be 
positioned at other heights and angles that provide an ergonomic position. 
Referring to FIGS. 1-4, when the emergency dispatch operator or the user 
ends the emergency call, the motor 18 turns on, and the keypad plate 14 
and the keypad 16 are moved from the extended position back to the 
retracted position. In alternative embodiments, the motor 18 may be turned 
on by other actions, such as closing the door 56 of the emergency call box 
50 or pushing an activation button on the emergency call box 50. 
When the magnet 44 in the drive nut 30 is in the proximity of the position 
sensor 24, the magnet 44 activates the position sensor 24, and the 
position sensor 24 signals the current sense circuitry in the emergency 
call box housing 52 to drop voltage to the motor 18. Dropping the voltage 
to the motor 18 slows down the rotation of the lead screw 28, thus 
preventing the lead screw 28 and the drive nut 30 from locking up and 
jamming. Dropping the voltage to the motor 18 also reduces the force with 
which the keypad plate 14 and the keypad 16 return to the retracted 
position, thus protecting against pinching the user's fingers, other body 
parts, or clothing. When the keypad plate 14 and the keypad 16 are in the 
retracted position, the front of the keypad plate 14 stops against a 
gasket 49, as shown in FIG. 2a. This drives up current on the circuitry in 
the emergency call box housing 52, and the circuitry then shuts off the 
relay to the motor 18, thus shutting down the motor 18. If the keypad 
plate 14 and the keypad 16 are unable to move completely back to the 
retracted position, the magnet 44 in the drive nut 30 does not activate 
the position sensor 24. This drives up current on the circuitry in the 
emergency call box housing 52, and the motor 18 then reverses, thus 
returning the keypad plate 14 and the keypad 16 to the extended position. 
FIGS. 10a and 10b illustrate detailed views of the keypad 16 mounted on top 
of the keypad plate 14 in accordance with an embodiment of the present 
invention. In one embodiment, the keypad plate 14 is made of cold rolled 
steel that is zincchromate plated and then painted. However, in 
alternative embodiments, the keypad plate 14 may be made of other suitable 
materials, such as plastic, ceramic, metal, composites, or the like. The 
keypad 16 is a membrane with tactile feedback, which utilizes membrane 
switch technology that is overlaid with textured polyester and then hard 
coated to provide a hermetic seal that is substantially impervious to 
harsh environments. In one embodiment, the keypad 16 is mounted on top of 
the keypad plate 14 using adhesive. However, in alternative embodiments, 
the keypad 16 may be mounted on top of the keypad plate 14 using 
fasteners, such as screws, bolts, nails, rivets, or the like. 
Referring to FIG. 10b, the keypad plate 14 has two holes with threads 130 
and 132. As illustrated in FIGS. 7a and 7b, the slider 32 also has two 
corresponding holes with threads 100 and 102, one hole on each side of the 
receiving recess 46. Referring to FIGS. 2a-2c, the holes 100 and 102 in 
the slider 32 are aligned with the holes 130 and 132 in the keypad plate 
14. In one embodiment, screws are inserted through the holes 100 and 102 
in the slider 32 and the holes 130 and 132 in the keypad plate 14 to 
secure the slider 32 underneath the keypad plate 14. In alternative 
embodiments, the slider 32 may be secured underneath the keypad plate 14 
using other types of fasteners, such as bolts, nails, rivets, or the like. 
FIG. 11 shows a schematic diagram of a keypad circuit 150 in accordance 
with an embodiment of the present invention. Referring to FIGS. 10a-11, 
the keypad 16 includes keys labeled as "Yes" 140 and "No" 142 to allow the 
user to quickly respond to questions presented on the display 62 of the 
emergency call box 50 illustrated in FIG. 3. The keypad 16 also includes 
keys labeled as "SK" 144 and "GA" 146, which are standard TDD 
abbreviations for "stopped keying" and "go ahead" respectively, to 
facilitate use of the keypad 16 for bidirectional communication between a 
user and an emergency dispatch operator without the need for voice 
communication. 
While the description above refers to particular embodiments of the present 
invention, it will be understood that many modifications may be made 
without departing from the spirit thereof. The accompanying claims are 
intended to cover such modifications as would fall within the true scope 
and spirit of the present invention. 
The presently disclosed embodiments are therefore to be considered in all 
respects as illustrative and not restrictive, the scope of the invention 
being indicated by the appended claims, rather than the foregoing 
description, and all changes which come within the meaning and range of 
equivalency of the claims are therefore intended to be embraced therein.