Snowmobile safety switch system

A safety switch system for use on snowmobiles that eliminates the hazards of previous systems by providing series connected normally closed switches, one connected directly into the throttle control lever which the operator must press for increasing engine speed from idle, and the other mounted directly on the carburetor and controlled by the throttle control arm which is directly connected to the butterfly valve of the carburetor. The two switches are connected to an engine kill system, such as a ground circuit for the ignition. One of the switches must be open for the engine to be running. This means that when the throttle is open (the carburetor control arm is away from idle position) and the operator's hand is off the throttle control lever the engine is dead. However, with the throttle arm in idle position the engine will run whether the operator has his hand on the manual throttle control lever or not. If the operator has his hand pressing with force on the manual throttle control lever the engine will run whether the carburetor throttle arm is open or closed. The positioning of the control switches eliminates the hazards that can result from mechanical failure of components because of the direct placement of the switches at the critical control locations.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to run-away preventive arrangements for 
vehicles, such as snowmobiles or other motorized devices. 
2. Prior Art 
In the prior art, so called "dead man" controls or run away preventing 
systems have been advanced for many different types of devices. In the 
U.S. Pat. No. 3,849,620 to Melisz a control which uses two series 
connected switches, one operated by a separate "dead man" lever on the 
handle of a power trowel and the other near the throttle control lever on 
the handle does have two normally closed switches in series that will 
ground the ignition if both are closed. The unit requires two separate 
hand actuated levers, one a dead man control, and the other the manual 
operated throttle control, and does not have a separately controlled 
switch on the carburetor itself. Also, it must be pointed out that in the 
device shown in the Melisz patent freezing or binding of the pivot pin for 
the dead man control can cause malfunction of the safety system, because 
of the placement of the switches. 
U.S. Pat. No. 3,789,938, issued to Hetteen shows a switch arrangement for 
providing a safety shut off for a snowmobile, but the switches are in 
parallel. In this particular device, one of the switches is positioned at 
the throttle arm and it appears that the throttle arm forms one of the 
contacts of the switch of the carburetor. 
The Filip U.S. Pat. No. 3,881,461 shows an automatic cut-off device for 
vehicles, where two switches have to be operated in sequential operation, 
and the switches are located in only one location, so that the necessary 
safety under potential adverse conditions such as the seizing of a 
throttle control rod, or of the throttle arm would not provide for the 
desired safety features. 
Another type of control, different than the present invention, is 
illustrated in the Veilleux U.S. Pat. No. 3,695,379. This device, which 
relates to ignition systems of automobiles is not concerned directly with 
hand throttle controls, and includes a panic button for stopping the 
engine. 
Other devices uncovered in the preliminary search in this case which 
generally show the state of the art, include the following U.S. Pat. Nos. 
2,550,999 -- Hoffman, 3,791,366 -- MacMillan, 3,789,402 -- Raab, 3,734,230 
-- Tanaka, 3,672,344 -- Albertson, 3,758,736 -- Tanaka, 3,845,847 -- Camp, 
3,303,836 -- Burleigh, 2,296,003 -- Van Loo, 3,742,928 -- Albertson. 
SUMMARY OF THE INVENTION 
The present invention relates to a safety system for preventing the 
run-away of vehicles such as snowmobiles. The system comprises an engine 
kill arrangement which can, for example, ground the ignition system and 
which uses two series connected, normally closed switches. The switches 
are located so that mechanical failure such as binding or seizing of lever 
pivot pins or control cables, or other similar operating problems that 
occur, will not cause the safety system to malfunction. 
A first normally closed switch is placed directly in the operator's 
throttle control handle or lever and is placed so that whenever the 
operator's hand is depressing the throttle control for increasing the 
engine speed the switch will be open. No separate dead man lever is 
utilized, nor is the switch positioned so that the movement of the lever 
itself is necessary for operation. The only thing that is necessary for 
operation of the switch is that there is a pressure on the throttle 
control lever, which will open the switch. 
The switch actuating surface on the throttle control lever encompasses 
substantially the entire actuating surface of the lever for greater safety 
and reliability. 
A second series connected switch, also normally closed, is mounted in a 
housing on the carburetor, and the housing is connected to move with the 
idle adjusting screw. The throttle butterfly valve actuator arm, which 
normally stops against the idle adjusting screw in idle position has a 
flange of sufficient width to provide an actuating surface engaging the 
second switch control button when the throttle arm goes to idle position. 
Because the housing carrying the second switch moves with the idle 
adjusting screw, whenever the adjusting screw is changed, the switch 
control button position is changed as well. Therefore, regardless of idle 
adjustment, whenever the throttle control arm moves to its idle position, 
that is, the butterfly valve in the carburetor moves to its idle position, 
the normally closed switch will be opened. Any position other than the 
idle position will cause the normally closed switch to close. Thus, if the 
butterfly shaft should bind open the second switch would be closed. 
Suitable microswitches are used for the control switches so the switches 
are reliable and are responsive to only a small amount of movement. 
It can thus be seen that the positioning of the control switches is of 
great importance, and that freezing of a throttle control linkage, such as 
a cable, will not affect operation, nor will binding of the pivot pin on 
the throttle hand control lever cause malfunction of the safety system. 
If either or both of the switches are open, the engine will be permitted to 
run. This means that when the operator grasps the throttle control handle, 
opening the switch there, movement of the throttle control arm away from 
its idle position to increase engine speed will not activate the kill 
system. However, if an operator should drop the throttle, for example when 
falling off the machine, the switch of the throttle hand control lever 
will close immediately grounding the ignition and stopping the engine 
unless the throttle arm returns to its idle position. The situation where 
this would be important is when the butterfly valve might freeze open, and 
the operator dropped the throttle control. The engine would then be 
grounded, stopping the sled and avoiding a run-away. 
The series connected, normally closed switches for the engine kill system, 
one of which is positioned to be acted upon directly by the butterfly 
control arm at the carburetor and the other of which is positioned to be 
actuated whenever a hand is pressing on the manual throttle control lever 
directly enhances the safety and reliability of the engine kill system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Reference is made to known, general snowmobile speed control for 
understanding of the invention as outlined in certain prior art patents 
listed above. The fragmentary showing of an operator's manual control 
handle indicated generally at 10 is therefore believed to be sufficient. 
The control handle 10 is the operator control used for steering the 
snowmobile, and includes an operator's grip 11 at the outer end of the 
control handle. As is conventional in many hand controlled vehicles, the 
operator's handle includes a throttle control indicated generally at 12. 
A housing 13 is mounted onto the operator's control handle 10, and a 
throttle lever 14 is pivotally mounted to the housing 13 on a pivot pin 
15, as shown. An operator holding the grip 11 would grasp the throttle 
control lever 14 adjacent its outer portion indicated generally at 16, 
normally by placing a thumb on the control surface 17, the covering of 
which has been broken away and is shown only in dotted lines. The covering 
would be flexible material or a foam layer, for example. Substantially the 
entire surface of the outer end portion is part of a receptacle or slot 
indicated at 20 and as also seen in FIG. 3. The opening is a full width 
transverse slot, with small overhanging shoulders 20A and 20B. A switch 
assembly 21 in the throttle control lever includes a plate 21 which is 
spring mounted with a leaf spring 22. The leaf spring 22 moves in a pair 
of slots 23 at opposite ends of the slot 20, as can be seen in FIG. 3, so 
that the plate and spring are held in place when the device is assembled. 
The plate 21A also carries an electrical contact strip 24 of a suitable 
material, that is made to engage contacts 24A and 24B, respectively, 
attached to the respective shoulders 20A and 20B. The spring 22 thus will 
urge the plate 21A to a position where the strip 24 is in engagement with 
both of the contacts 24A and 24B, to complete an electrical circuit path 
between the two contacts. As will be shown schematically, each of the 
contacts is connected to a separate electrical wire 25A and 25B, 
respectivly, as can be seen in FIG. 3. 
The mounting housing 13 includes a support portion or ear 26, that retains 
an outer cable housing 27 of the throttle control cable that mounts a 
slidable throttle control wire 28. The throttle control wire 28 is 
connected to lever 14 through a control end 29 fitting into a receptacle 
in the conventional manner, so that when the manual throttle control lever 
is pivoted, the throttle control wire 28 will be moved in and out with 
respect to the housing 27. The throttle is spring loaded to idle position 
in a normal manner. A torsion spring is shown in FIG. 2. 
The other end of the cable housing 27 is attached as at 32 with a pair of 
lock nuts to a bracket 33 mounted onto a carburetor 34 of conventional 
design. The carburetor is mounted onto an engine 35 at the intake 
manifold, and includes an intake air tube indicated generally at 36. The 
carburetor is of normal design including a butterfly valve indicated in 
dotted line position that operates in an interior throat or venturi of the 
carburetor in a conventional manner. The butterfly valve is mounted onto a 
throttle shaft 37 that pivots to control the position of the butterfly to 
conrol engine speed. The shaft 37 has a throttle or butterfly valve 
control arm 38 drivably mounted thereon, and the opposite end of the 
sliding wire control 28 from connector 29 is connected with a clip 40 to 
one end of the throttle control arm as at 41. 
Referring now specifically to FIG. 2, the carburetor 34 includes an idle 
screw support ear 42, which has a threaded opening 43. The ordinary idle 
screw which threads through opening 43 is removed and a housing 44 is 
installed with a screw 45 threading in opening 43 and holding the housing 
in position. The housing, as can be seen, has a recess 46 into which the 
ear 42 slidably fits. The screw 45 is threaded through the opening 43, and 
through a provided clearance hole 47 in the housing so that the screw 
engages a tab 48 of the arm 38 in a normal manner to provide the normal 
idle position of the idle adjusting screw. A coil spring 50 is mounted on 
the screw, between the top of the ear 42 and the surface defining the top 
of recess 46, so that the spring 50 will urge the housing 44 upwardly, 
that is away from the tab 48 of the throttle control arm 38. The housing 
44 also includes an opening or receptacle 51 for receiving a normally 
closed micro-switch 52 which has an actuating plunger 53 protruding 
through a clearance opening 54 at the bottom of the housing 44. The 
actuating plunger, as can be seen is positioned at a slight angle with 
respect to the axis of the idle screw so that the plunger end easily 
engages the tab 48 on the arm 38. The plunger is positioned so that when 
the arm 38 is in idle position against the end of screw 45 the plunger 
will be moved. The switch 52 is epoxied into place in the opening 51, so 
that once the relative position of the plunger is correlated with the 
position of the idle screw, whenever the tab 48 backs against the idle 
screw the plunger 53 will be actuated to open the switch 52. 
As can be seen schematically, the wire 25B is connected to the switch, and 
the wire 25C leading from the switch 52 is connected to a ground. 
Referring specifically to FIG. 4, a schematic representation of the circuit 
is shown. As stated previously, the lead 25C is grounded, as can be seen, 
and leads to one side of the switch 52 also shown schematically in FIG. 4, 
is in its open position, that is with the butterfly valve and arm 38 at 
idle position. The lead 25B leads to one terminal 24B forming part of the 
switch 21 at the manual throttle lever. The spring loaded connector 21A is 
shown, connecting to the other contact 24A. Wire 25A which leads to the 
ignition system is connected to some portion of the ignition wiring which 
when grounded will disable the ignition. 
The following Table I shows the state of the engine in the various 
positions of the throttle, and the hand. The hand being "on" or "off" 
refers to the hand touching the throttle control lever and the switch 21. 
The throttle reference relates to the butterfly valve of the carburetor. 
"Closed" means it is at idle position and "open" means any position other 
than idle. 
TABLE I 
______________________________________ 
Throttle 
Hand Switch 52 Switch 21 
Engine Condition 
______________________________________ 
closed off open closed runs 
open off closed closed stop 
open on closed open runs 
closed on open open runs 
______________________________________ 
It can thus be seen that with the present arrangement the sensing is done 
directly at the involved components. Freezing of the control wire 28 in 
its housing, binding of pivot pins, bending of throttle levers, or similar 
malfunctions of a mechanical nature will not affect the safety of the 
present device. In this way, the unit is very reliable, easy to 
manufacture, and does not interfere with conventional operation of 
snowmobiles. It does not require additional levers, panic buttons, or dead 
man control levers at all. It is tied right into existing engine controls, 
and permits adjustment of engine idle speed in the normal manner but still 
uses direct sensing at the involved components for safety. 
The ground connection acts as an engine disabling connection or means, 
which is series connected through switch 51 and 21 to the engine control, 
in this case the ignition system. Other engine disabling controls also 
could be used, for example, an electric fuel cut-off valve could be 
energized by series connected switches located in the same positions as 
those shown. 
It should be noted that the last small bit of travel of the throttle arm 
opens switch 52. Thus if the throttle arm is away from its idle position 
to any significant degree (when the engine starts to pick up speed) the 
switch 52 will be closed. Also, if fuel control is achieved with other 
means than a carburetor one of the switches would be mounted at the final 
movable member for the fuel control and would be permitted to move to its 
normal position whenever the full control moved away from idle.