Steering wheel pad keyboard switch assembly

A steering wheel pad keyboard switch assembly is mounted on a steering wheel. The preassembled switch assembly comprises a base, a printed circuit board which has an array of open contact grids, an elastomeric switch member which has an array of movable contacts, a guide plate and a push button sub-assembly. The guide plate has a plurality of guide bosses and guide holes disposed in the same predetermined array for guiding the stem pieces of the push buttons into operative contact with the movable contacts of the switch member and a pad portion for supporting a horn switch. The push button sub-assembly comprises a frame member which is attached to the base to provide the unit handle switch assembly, a plurality of push buttons which are slideably retained in respective slide chambers of the frame and a soft decorative cover which includes a depressible horn switch pad to operate the horn switch and cut-outs to provide access to the push buttons. The guide plate and the stem pieces of the push buttons are made of a translucent material and form part of the back lighting system for the push button legends.

BACKGROUND OF THE INVENTION 
This invention relates generally to keyboard switch assemblies and more 
particularly, to steering wheel pad keyboard switch assemblies which are 
mounted on a vehicle steering wheel. 
Such keyboard switch assemblies are already known, for instance, from U.S. 
Pat. No. 2,863,015 (Ahrens) which shows switch controls mounted on the 
spoke of a steering wheel and U.S. Pat. No. 3,544,743 (Takei) which shows 
a printed circuit board in a steering wheel which is operated by push 
button switches. Further, U.S. Pat. No. 4,374,310 (Kato) shows a steering 
wheel switch arrangement comprising a depressible horn pad and switches 
which are mounted on fixed pedestals while U.S. Pat. No. 4,383,148 
(Arima); U.S. Pat. No. 4,409,584 (Arima) and U.S. Pat. No. 4,421,960 
(Arima) show other electric switch assemblies which are operated by push 
buttons. 
SUMMARY OF THE INVENTION 
The object of this invention is to provide an improved steering wheel pad 
keyboard switch assembly. 
A feature of the invention is that the steering wheel pad keyboard switch 
assembly is a preassembled unit which facilitates assembly into the 
steering wheel under factory conditions. 
Another feature of the invention is that the steering wheel pad keyboard 
switch assembly includes a keyboard sub-assembly in which the push buttons 
are slideably retained in a frame member thereby facilitating assembly of 
the steering wheel pad keyboard switch assembly. 
Still yet another feature of the invention is that the steering wheel pad 
keyboard switch assembly includes a horn switch which is operated in a 
conventional manner. 
Still yet another feature of the invention is that the steering wheel pad 
keyboard switch assembly includes a back lighting system for the push 
buttons.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawing, FIG. 1 illustrates a vehicle instrument panel 
10 and steering wheel 12 in which the steering wheel pad 14 comprises a 
keyboard assembly 16 in accordance with this invention. 
Referring now to FIGS. 5, the keyboard assembly 16 comprises a base 17 
which is adapted to be attached to the hub of the steering wheel 12 so as 
to provide the steering wheel pad 14. The base 17 includes a U-shaped 
support plate 18 at the periphery of an open box-like guard 22 which has 
latch arms 19 for securing the keyboard assembly to the hub of the 
steering wheel 12. 
The keyboard assembly 16 further comprises a printed circuit board 20 which 
is mounted on the support plate 18. The printed circuit board 20 has a 
number of electronic components (not shown) mounted on its underside where 
these components are protected by the open box-like guard 22 of the base 
17. These electronic components are connected into a predetermined control 
circuit by a circuit pattern on surfaces of the printed circuit board 20 
which includes a plurality of open contact grids 24 on the upper surface. 
The contact grids 24 are disposed in a predetermined array within a 
U-shaped area which borders three sides of the printed circuit board 20 
and which is preferably adhesively secured to the support plate 18 
beneath. 
The keyboard assembly 16 also includes a U-shaped switch member 26 which is 
disposed on the upper surface of the U-shaped area of the printed circuit 
board 20. The switch member 26 comprises a sheet or membrane of 
elastomeric material which has a plurality of integrally molded hollow 
buttons 28 which correspond in number to the open contact grids 24 and 
which are disposed in the same predetermined array as the contact grids 
24. Each hollow button 28 carries a conductive disc 30 inside, as shown in 
FIGS. 2, 3 and 4 so that the hollow buttons 28 form movable contacts 32 
which selectively close the open contact grids 24 when the hollow buttons 
28 are depressed. 
The keyboard assemby 16 further includes an acrylic guide plate 34 which 
also serves as a light bar as explained more fully below. The guide plate 
34 is disposed over the the printed circuit board 20 with the U-shaped 
switch member 26 sandwiched therebetween. The guide plate 34 comprises a 
U-shaped peripheral portion 36 along three sides thereof and a thinner pad 
portion 38 which is defined by a recess in the surface which faces the 
printed circuit board 20. This recess provides room for the soldered 
projecting wire ends of the electronic components which are mounted 
beneath the printed circuit board 20. 
The U-shaped peripheral portion 36 of the guide plate 34 includes a 
plurality of guide bosses 40 having guide holes 42. The plurality of guide 
bosses 40 and guide holes 42 correspond in number to the movable contacts 
32 of the switch member 26 and the open contact grids 24 of the printed 
circuit board 20 and they are disposed in the same predetermined array as 
the movable contacts 32 and the open contact grids 24. 
The U-shaped peripheral portion 36 of the guide plate 34 also includes four 
domes 44 which have cavities which open onto the surface of the guide plate 
which is adjacent the printed circuit board 20 as shown in FIG. 3. These 
cavities receive the light bulbs 46 which are plugged into sockets which 
are mechanically and electrically connected to the printed circuit board 
20. First selected surfaces of the acrylic guide plate 34 are painted 
white for light reflection. Then substantially, the entire surface of the 
acrylic guide plate 34 is painted opaque, preferably a matte black, so 
that the acrylic guide plate 34 acts as a light guide or pipe which 
transmits the light from the light bulbs 46 to selected unpainted 
translucent surfaces of the guide plate 34 as explained more fully below. 
A horn contact plate 48 is secured on the surface of the pad portion 38 of 
the guide plate 34 which is remote from the printed circuit board 20. A 
flexible printed circuit contact 50 lies atop the horn contact plate 48. 
The flexible printed circuit contact 50 comprises a thin copper sheet 51 
which is secured on a Mylar support sheet 52 and which has a foamed spacer 
grid 53 on its exposed surface. This foamed spacer grid 53 engages the 
contact plate 48 and normally spaces the thin copper sheet 51 from the 
horn contact plate 48 as shown in FIGS. 3 and 4. However, when the 
flexible printed circuit contact 50 is depressed, the copper sheet 51 
contacts one or more dimples 49 of the horn contact plate 48 which closes 
the circuit between the leads 54a and 54b to operate the vehicle horn (not 
shown). 
The keyboard assembly 16 also includes a push button sub-assembly 56 which 
comprises a hardshell frame 58 and a plurality of push buttons 60. The 
hardshell frame 58 has a face plate 62 and four sidewalls 64 which form a 
housing when the hardshell frame 58 is attached to the support plate 18 of 
the base 17 as shown in FIG. 3 to provide a unit handled keyboard assembly 
16. The frame plate 62 of the frame 58 has three raised bezels 66 which 
cooperatively define a plurality of slide chambers 68 which extend through 
the frame 58. The plurality of slide chambers 68 correspond in number to 
and are disposed in the same predetermined array as the guide bosses 40 
and guide holes 42 of the guide plate 34. 
The plurality of push buttons 60 are shaped to match respective slide 
chambers 68 and slideably retained in the plurality of slide chambers 68 
respectively. Each push button 60 comprises an opaque hollow cap 70 which 
has a flanged skirt 72 which slides freely in the associated slide chamber 
68. Each push button is retained in the downward or depressed direction by 
its side slots 74 which receive nibs 76 of the frame 58 and in the upward 
or raised direction by the skirt flange 78, as shown in FIG. 4, so that 
the frame 58 and buttons 60 are a unit-handled sub-assembly as indicated 
above. Each button 60 also includes a translucent stem piece 80 which is 
integrally attached inside the hollow cap 70 and which extends below the 
skirt flange 78 by a substantial amount. 
When the hardshell frame 58 is attached to the support plate 18 of the base 
17, the hollow caps 70 of the push buttons 60 fit over the guide bosses 40 
of the guide plate 34 and the stems 80 extend through the guide holes 42 
with a sliding fit to engage the hollow buttons 28 of the elastomeric 
switch member 26 as shown in FIGS. 2, 3 and 4. The natural resilience of 
the hollow elastomeric buttons 28 biases the push buttons 60 to the raised 
position as well as spaces the contact disks 30 from the contact grids 24. 
The face plate 62 of the hardshell frame 58 also has a large rectangular 
hole 82 which surrounds the flexible printed circuit switch 50 which is on 
top of the horn contact plate 48 which is attached to the pad portion 38 of 
the guide plate 34. 
The push button sub-assembly 56 further comprises a decorative cover 84 of 
soft pliable plastic material which is fitted on the frame member 58 and a 
thick rubber-like pad 86. The pad 86 is friction fitted into a rectangular 
cavity 88 of a depressible pad portion 89 of the cover 84 and the pad 86 
engages the flexible printed circuit contact 50 when the decorative cover 
84 is fitted on the frame member 58 so that horn switch is operated when 
the pad portion 89 of the cover 84 is depressed. The decorative cover 84 
has three cut-outs 90 which fits around the three raised bezels 66 so that 
the push buttons 60 are accessible for operation. The decorative cover pad 
84 also has flange pieces 92 and button hooks 94 which cooperate with side 
rails 96 and notches 98 of the frame member 56 to retain the cover pad 84 
on the frame member 56 as shown in FIGS. 2 and 3. 
The push buttons 60 are lit by a back lighting system which includes the 
acrylic guide plate 34 and the translucent stem pieces 80. As indicated 
above, selected surfaces of the guide plate 34 are painted white, and then 
substantially the entire surface of the acrylic guide plate 34 is painted 
opaque, preferably a matte black, so that the acrylic guide plate 34 acts 
as a light guide or pipe which transmits the light from the light bulbs 46 
to selected unpainted translucent surfaces of the guide plate 34. These 
areas are the faces of the guide blocks 40 and the cylindrical surfaces of 
the guide holes 42. The light which is transmitted to these surfaces is in 
turn transmitted into the translucent stem pieces 80 and to the faces 100 
of the stem pieces 80. These faces 100 are disposed in the windows 102 of 
the opaque hollow caps 70 and the translucent faces 100 are covered with 
indicia tabs having a translucent legend on an opaque background which 
preferably matches the color of the opaque hollow caps 70. The light at 
the faces 100 of the stem pieces 80 is then transmitted through the 
translucent legends to light up the messages of the legends. 
We wish it to be understood that we do not desire to be limited to the 
exact details of construction shown and described, for obvious 
modifications will occur to a person skilled in the art.