Foot pedal switch

Single pedal vehicle speed and direction controls are advantageously applied in industrial vehicles. Available pedals are prone to damage in an industrial environment and require multiple discrete pedal portions for various pedal functions. The instant apparatus provides a simple and durable foot pedal having a unitary pad including first and second integral moveable members and respective sealed switchable members. The pad is advantageously of one piece molded rubber construction and includes first and second resilient portions, each having a curvilinear connecting portion and an intermittent substantially solid connecting portion. The switchable members include respective sealed membrane switches, each having first and second spaced apart electrically conductive contact surfaces. At least one of the first and second conductive contact surfaces is attached to a flexible polymer film and is maintained separated from the other first and second conductive contact surfaces by a pressure medium contained within an enclosed pressurable chamber. The respective pressurable chambers are connected to one another and to a common pressure medium reservoir by respective interconnecting passageways. The instant apparatus is both durable and reliable when used in an industrial environment, and is of relatively simple and inexpensive construction.

DESCRIPTION 
1. Technical Field 
This invention relates generally to an apparatus for controlling the 
movement of a vehicle and, more particularly, to a foot pedal assembly for 
controlling a plurality of vehicle movement functions. 
2. Background Art 
In the past, vehicles, such as lift trucks, have advantageously been 
provided with combined vehicle speed and direction controls. Such combined 
controls typically include a foot pedal moveable for speed control, and 
one or more independent foot pedal switches attached to the foot pedal and 
moveable for direction control. Such arrangement facilitates control of 
both vehicle speed and forward and reverse vehicle direction with a 
single, foot operated, control. 
Conventional foot operated direction controls typically include forward and 
reverse pedal portions connected to the main foot pedal. Movement of the 
pedal portions operates respective mechanical switches mounted on the main 
pedal. Such switches, typically of the push-button micro-switch variety, 
are prone to mechanical failure and to atmospheric contamination. 
Additionally, the discrete pedal portions must be assembled to the main 
pedal, for example with hinges or other flexible mounting devices. 
A further advance in the art replaces the failure prone mechanical switches 
with Hall effect switches and magnetic actuators. Such assemblies avoid 
the problem of atmospheric contamination but add complexity to the pedal 
and continue to require mechanical assembly of the pedal portions to the 
main pedal. 
In view of the above problems, it is advantageous to provide a pedal 
assembly that is substantially free from failure prone devices, easy to 
assemble without need for independent discrete pedal portions, and 
incorporates durable, rugged and inexpensive construction. 
The present invention is directed to overcoming one or more of the problems 
as set forth above. 
DISCLOSURE OF THE INVENTION 
In one aspect of the present invention an apparatus is provided with a base 
having a substantially planar surface. First and second switchable members 
are connected to the base, each having an axis extending substantially 
perpendicular to the planar surface. Also connected to the base is a pad 
having first and second moveable members. The pad and moveable members are 
of unitary construction. Each of the moveable members has a contact 
surface lying in a plane substantially parallel to the base planar surface 
and axially aligned with respective ones of the first and second 
switchable members. 
The present invention provides a pedal assembly that is substantially free 
from failure prone devices, easy to assemble, and of durable, rugged and 
inexpensive construction. The foregoing and other advantages are apparent 
in view of the following detailed description of the invention when 
considered in conjunction with the accompanying drawings. The drawings are 
not intended as a definition of the invention but are for the purpose of 
illustration only.

BEST MODE FOR CARRYING OUT THE INVENTION 
Referring first to FIG. 1, an apparatus embodying certain of the principles 
of the present invention is generally indicated by the reference numeral 
10. It should be understood that the following detailed description 
relates to the best presently known embodiment of the apparatus 10. 
However, the apparatus 10 can assume numerous other embodiments, as will 
become apparent to those skilled in the art, without departing from the 
appended claims. 
The apparatus 10 includes a pedal 12, for example, an accelerator pedal of 
a vehicle such as an electric lift truck. The pedal 12 is connected 
through linkage 14 to a vehicle control mechanism 16. The control 
mechanism 16 exercises, for example, control over vehicle speed and 
direction in response to speed and direction command signals, as is 
well-known in the art. 
The pedal 12 is shown to have a swing motion about an axis 18. Pressure on 
the pedal 12 sufficient to overcome the bias of a spring 20 moves the 
pedal 12 about the axis 18. The degree of motion of the pedal 12 about the 
axis 18 is translated into a speed command signal, for example by an 
encoder 22, and the command signal is delivered to the control mechanism 
16. 
Pressure on preselected portions of the pedal 12 is translated into 
direction command signals as is hereinafter described. These direction 
command signals are likewise delivered to the control mechanism 16. 
Referring now to FIG. 2, the pedal 12 includes a base 24 having a 
substantially planar surface 26. In the preferred embodiment, the base 24 
is an aluminum plate. Connected to the base planar surface 26 are first 
and second switchable members 28,30, each having a respective axis 32,34 
extending substantially perpendicular to the base planar surface 26. 
The switchable members 28,30 are, for example, membrane switches, each 
having first and second spaced apart conductive contacts 28a,28b,30a,30b 
separated by an enclosed pressurable chamber 28c,30c. Each of the 
pressurable chambers 28c,30c is connected for pressure communication with 
the other of the pressurable chambers 28c,30c and with an associated 
pressure reservoir 36. In the preferred embodiment, the pressure medium is 
a substantially non-conductive gas, for example, air, contained at one 
atmosphere. The contacts 28a,30a,28b,30b are connected by respective 
conductive lines to a terminal block 38. In the preferred embodiment, the 
contacts 28a,30a,28b,30b and the connecting lines are flexible conductors 
deposited or positioned on layers of polymer film. 
The switchable members 28,30 are provided by assembly of layers of polymer 
film on the base 24, in the relationship shown in FIG. 3. A first layer of 
film 31a is applied directly to the base planar surface 26. The first 
conductive contact 28a is positioned on the first layer of film 31a. A 
second layer of film 31b is applied over the first layer 31a and functions 
as a spacer. The second layer of film 31b includes a cut out portion 
surrounding the contact 28a. A third layer of film 31c is applied over the 
second layer 31b with the second conductive contact 28b positioned on the 
third layer 31c. The second conductive contact 28b is maintained adjacent 
and substantially parallel to but separated from the first conductive 
contact 28a. The cut out portion of the second layer of film 31b is thus 
enclosed by the first and third layers of film 31a,c and is the 
pressurable chamber 28c. Finally, a fourth protective layer of film 31d is 
applied over the third layer 31c. Such an assembly is commonly known as a 
membrane switch and is relatively impervious to atmospheric contamination 
owing to the completely sealed construction. Although FIG. 3 depicts only 
one of the switchable members 28,30 in cross section, the other of the 
switchable members 28,30 is similarly constructed and includes elements 
corresponding to those discussed above. 
The switchable members 28,30 and the electrical relationship of one to the 
other is depicted in the schematic representation at FIG. 4. Each 
switchable member 28,30 is seen to include a first contact 28a,30a 
connected in common to a single conductor, and a second contact 28b,30b 
connected to respective individual conductors. 
Referring now to FIG. 5, the pedal 12 also includes a pad 40 having first 
and second integral moveable members 42,44. The pad is constructed of 
flexible, molded material, for example, rubber, and is of one piece or 
unitary construction. The moveable members 42,44 are attached to the pad 
40 by respective molded resilient portions 46,48, best seen in the 
partially sectioned view of the pad 40 at FIG. 6. Adverting to FIG. 5, the 
resilient portions 46,48 each include a curvalinear connecting portion 
46a,48a and one or more intermittent substantially solid connecting 
portions 46b,48b. The resilient portions 46,48 connect the respective 
moveable members 42,44 to the remainder of the pad 40 while maintaining 
the moveable members 42,44 controllably free to move independently of the 
pad 40 in response to a force applied to the respective moveable member 
42,44. 
Movement of the moveable members 42,44 with respect to the pad 40 occurs at 
a predetermined spring rate determined by the particular construction of 
the respective resilient portions 46,48. The spring rate is primarily 
determined by the properties of the molding material, the cross sectional 
area of the resilient members 46,48, and the ratio of the curvalinear 
connecting portion 46a,48a to the substantially solid connecting portions 
46b,48b. In the preferred embodiment, the predetermined spring rate is in 
a range of 1 to 15 pounds. A force applied to one of the moveable members 
42,44 in excess of the predetermined spring rate causes the respective 
moveable members 42,44 to move relative to the pad 40. 
Those skilled in the art will recognize that, although resilient portions 
46,48 having preselected geometric forms are used in the preferred 
embodiment, other arrangements and constructions of the resilient portions 
46,48 can be readily incorporated in the pedal 12. 
Referring now to FIG. 6, the sectioned portion shows that the second 
moveable member 44 includes a second contact portion 51 having a second 
contact surface 52. The pad 40 is connected to the base 24 with the second 
contact surface 52 lying in a plane substantially parallel to the base 
planar surface 26. The second contact surface 52 is aligned with the 
second switchable member 30 along the axis 34. A second stop portion 55, 
substantially cylindrical in shape, surrounds the second contact portion 
51, and includes a second stop surface 56 lying in a plane substantially 
parallel to the second contact surface 52 and displaced from it by a 
predetermined amount. 
Although FIG. 6 depicts only the second moveable member 44 in 
cross-section, the first moveable member 42 is similarly constructed, and 
includes elements corresponding to those discussed above, for example, 
first contact portion 49, first contact surface 50, first stop portion 53, 
and first stop surface 54. 
Industrial Applicability 
Operation of the apparatus 10 is best described in relation to its use on a 
vehicle, for example, an industrial vehicle such as an electric lift 
truck. 
The spring rate of the resilient portions 46,48 is selected to be less than 
the spring rate of the spring 20. Therefore, in response to a force 
greater than the spring rate of the resilient portion 46,48 being applied 
to the pad 40, one of the first and second contact surfaces 50,52 closes 
the respective switchable member 28,30 by displacing the pressure medium 
into the reservoir 36. The result is a direction command signal which is 
delivered by the flexible conductors to the control mechanism 16. 
Excessive displacement of the switchable members 28,30 is prevented by the 
stop portions 53,55. Owing to the large cross-sectioned area of the stop 
portions 53,55 relative to the contact portions 49,51, the stop portions 
53,55 effectively limit the travel of the contact portions 49,51 and 
prevent damage to the switchable members 28,30. 
Additional pressure on the pad 40 in excess of the spring rate of the 
spring 20 moves the pedal 12 about the axis 18. The pedal position is 
encoded by the encoder 22 and delivered as a speed command signal to the 
control mechanism 16. The control mechanism 16 responds, for example, by 
propelling the vehicle at the command speed in the command direction. The 
difference in spring rates between the resilient portion 46,48 and the 
spring 20 insures that a direction will normally be selected before a 
speed command is produced. 
The control mechanism 16 can be constructed to ignore any speed command 
signal not preceded by a direction command signal, for example, in the 
event the operator manages to avoid contact with the moveable members 
42,44 but moves the pedal 12. Also, the control mechanism 16 can ignore 
simultaneous selection of multiple directions, for example, in the event 
the operator simultaneously depresses both of the moveable members 42,44. 
Either of these situations can advantageously cause the vehicle to remain 
in a neutral mode of operation. The necessary circuitry, either hardware 
or software, to accomplish such error checking functions is readily 
incorporated in the control mechanism 16 by one skilled in the electronics 
art and is not an object of this invention. 
Other aspects, objects, advantages and uses of this invention can be 
obtained from a study of the drawings, the disclosure, and the appended 
claims.