Transmission safety locking lever apparatus

A transmission safety locking lever apparatus prevents a transmission from being shifted from park or neutral into either drive or reverse unless the vehicle brakes are applied. The apparatus includes first and second spaced apertures formed in a gear shift lever connected to the gear shift shaft coupled to and extending from the transmission. A lock pin movable between extended and retracted positions is biased to the extended position to engage one of the first and second apertures in the gear shift lever when the transmission is in either park or neutral. An actuator retracts the lock pin to enable the transmission to be shifted to any gear position from park or neutral only when the vehicle brakes are applied. A sensor is provided for detecting the application of the vehicle brakes via a predetermined pressure in the vehicle brake system. Electric current is applied to the actuator to activate the actuator when the pressure sensor detects a predetermined pressure in the vehicle brake system indicating application of the vehicle brakes to retract the lock pin from the gear shift lever.

BACKGROUND OF THE INVENTION 
1. Field of the Invention: 
The present invention relates, in general, to vehicle transmission gear 
shifting mechanisms and, specifically, to transmission safety lock devices 
which prevent shifting of a transmission until certain predetermined 
safety-related conditions are met. 
In vehicles provided with an automatic transmission, movement of a gear 
selector in the vehicle into any position of park, reverse, neutral or 
drive causes the transmission to be shifted through a linkage coupling the 
gear selector with the transmission into a gear ratio corresponding to 
park, reverse, neutral or drive. The vehicle engine operates independently 
of the transmission and can be operated when the transmission is in any of 
the park, reverse, neutral or drive modes. The operator controls movement 
of the vehicle in reverse or drive modes through the use of the vehicle 
accelerator and brake pedals. 
However, some vehicle operators occasionally leave the vehicle for a short 
time with the engine operating and the transmission in park or neutral. 
When the engine is operating and the vehicle is unattended by an operator, 
a child can easily move the gear selector into reverse or drive thereby 
causing movement of the vehicle and creating the potential of property 
damage and bodily injury to the occupants of the vehicle and pedestrians 
or bystanders. Furthermore, design deficiencies, misalignment or wear in 
the transmission or the transmission shifting linkage occasionally causes 
transmissions to shift into reverse or drive without direct operator 
intervention. Again, this results in unattended and uncontrolled vehicle 
movement. 
In order to prevent such unattended movement of a vehicle caused by the 
unintended shifting of the transmission into reverse or drive modes when 
the engine is running, several safety lock devices have been developed 
which prevent shifting of the transmission into drive or reverse modes 
until one or more safety-related conditions are met. Typically, such 
safety conditions require an intentional action by the operator of the 
vehicle which is difficult or impossible for a child. Generally, the known 
transmission safety lock devices employ stops or plungers which 
mechanically interlock with the vehicle gear selector and prevent movement 
of the gear selector from park or neutral into drive or reverse modes 
unless the vehicle brakes are applied. This ensures that the vehicle is 
attended by an operator and is in a safe operating mode when drive or 
reverse movement of the vehicle occurs. 
However, the known transmission safety lock devices utilize a large number 
of separate parts which increases the cost of the safety lock device and 
makes installation more difficult. Furthermore, the number and complexity 
of the parts employed in such safety lock devices prevents their use on a 
large number of different transmissions without extensive and expensive 
modification of the vehicle transmission. 
Thus, it would be desirable to provide a transmission safety lock device 
which prevent the shifting of a vehicle transmission from park or neutral 
into either drive or reverse unless the vehicle brakes are applied. It 
would also be desirable to provide a transmission safety lock device which 
is simple in construction and contains a small number of individual 
components. It would also be desirable to provide a transmission safety 
lock device which can easily be used with a large number of different 
transmissions and vehicles without excessive modification. 
SUMMARY OF THE INVENTION 
The present invention is a transmission safety locking lever apparatus 
which prevents a transmission in a vehicle from being shifted from park or 
neutral into either drive or reverse unless the vehicle brakes are 
applied. 
The apparatus comprises first and second spaced apertures formed in the 
gear shift lever which is connected to a gear shift shaft coupled to the 
transmission and rotatable for selecting transmission operating modes and 
gear ratios upon movement of a gear selector means in the vehicle. A lock 
pin is movable between extended and retracted positions. Means for 
mounting the lock pin are provided such that the lock pin engages one of 
the first and second apertures in the gear shift lever when in the 
extended position and the gear shift lever and the gear shift shaft are in 
a position selecting either park or neutral transmission operating 
conditions. Actuator means are provided for retracting the lock pin out of 
engagement with the gear shift lever when activated. Means, responsive to 
a predetermined pressure at which the vehicle brakes are applied, connects 
the actuator means to an electric power source to activate the actuator 
means to retract the lock pin from engagement with the gear shift lever. 
In a preferred embodiment, the gear shift lever is formed with an arcuate 
portion containing the first and second spaced apertures. Solid portions 
are formed in the arcuate portion of the gear shift lever between the 
first and second apertures. Such solid portions are engaged by the lock 
pin when the lock pin is in the extended position so as to enable the gear 
shift lever to be moved simultaneously with movement of the gear shift 
selector of the vehicle to park or neutral positions. 
The actuator means preferably comprises an electromechanical solenoid 
having a core and coil. The lock pin is movably disposed within the core 
and coil and is magnetically attracted into the core and coil by the 
magnetic field induced in the core when an electric current is applied to 
the coil. 
The sensor means preferably comprises a pressure switch mounted in the 
hydraulic fluid brake system of the vehicle and is configured for 
activation at a predetermined pressure signifying a high degree of brake 
application sufficient to bring the vehicle to a stopped position. 
A vehicle start interrupt is also provided by means of a contact plate 
mounted on the lock pin and movable therewith. The contact plate spans two 
contacts and closes an electric circuit between an electric power source, 
such as the vehicle's battery, and the vehicle starter so as to enable the 
starter to be energized through the vehicle ignition switch only when the 
lock pin is fully engaged in one of the first and second apertures in the 
gear shift lever. This ensures that the vehicle is in a safe operating 
condition when started. 
The transmission safety locking lever apparatus of the present invention 
provides safe operation of a vehicle by preventing the vehicle's 
transmission from being shifted into drive or reverse modes from either 
park or neutral unless the vehicle brakes are applied. The apparatus is 
simple in construction and contains a minimal number of separate 
components. This leads to a low manufacturing cost and, more importantly, 
enables the apparatus to be used with a large number of different 
transmission configurations. Further, the apparatus can be easily 
installed on most vehicles without significant modification.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Throughout the following description and drawing, an identical reference 
number is used to refer to the same component shown in multiple figures of 
the drawing. 
The present invention is a transmission safety locking lever device which 
locks a vehicle's transmission in either park or neutral positions and 
prevents shifting of the transmission to either drive or reverse positions 
unless the vehicle brakes are applied. 
FIG. 1 depicts a conventional prior art vehicle transmission showing a 
transmission housing 1 which houses the vehicle transmission containing a 
plurality of gear sets selectable in various ratios to provide various 
operating modes, including park, reverse, neutral and drive (P, R, N and 
D). Such a transmission is preferably an automatic transmission and has a 
gear shift shaft 4 coupled to the transmission gears and extending outward 
from one side of the housing 1. A planar link or gear shift lever A2 is 
fixedly connected at one end to the gear shift shaft 4. The opposite end 
of the gear shift lever A2 is connected to a shift control rod 3 which is 
attached to the gear shift selector, not shown, mounted interiorly within 
the vehicle. As is conventional, movement of the gear shift selector to 
either park, reverse, or drive positions causes a corresponding movement 
of the control rod 3 which results in a rotation of the gear shift lever 
A2 and the gear shift shaft 4 to the various positions labeled D, N, R and 
P, as shown in FIG. 1. Rotation of the gear shift shaft 4 results in a 
selection of the appropriate gear ratio or gear set in the transmission to 
implement the drive, neutral, reverse or park modes of vehicle operation. 
It will be understood that the present invention may be applied to any 
conventional vehicle transmission having any number of gears including 
transmissions having more than one forward drive mode, such as those 
conventionally referred to as D.sub.1 and D.sub.2 or D and LOW. 
Furthermore, the control rod 3 is illustrated by way of example only as 
forming one means for coupling the gear shift lever A2 to the gear shift 
selector mounted within the vehicle. Any linkage, cable or coupling 
mechanism may be employed to transmit movement of the gear shift selector 
to rotational movement of the gear shift lever A2. 
Referring now to FIGS. 2-5, the transmission safety locking lever device of 
the present invention includes the gear shift lever 2. The gear shift 
lever 2 is connected at one end to the gear shift shaft 4 extending 
outward from the transmission housing 1 and is rotatable therewith to 
enable the gear shift shaft 4 to select one of the transmission operating 
modes labeled D, N, R and P. The gear shift lever 2 is formed with a 
planar portion extending from the connection end to the gear shift shaft 4 
and an arcuate section integrally connected to the planar portion. 
An aperture 3A is formed at one end of the arcuate section of the gear 
shift lever 2, as shown in FIG. 3, and receives one end of the gear 
selector control rod 3. This causes rotation of the gear shift lever 2 
upon movement of the gear selector control rod 3 as described above. 
First and second apertures 20 and 27 are formed in the arcuate portion of 
the lever 2. The apertures 20 and 27 are spaced apart in the arcuate 
section of the lever 2 and bounded by solid portions. The first aperture 
20 corresponds to the park position labeled P; while the second aperture 
27 corresponds to the neutral position labeled N of the transmission, as 
shown in FIG. 3. Additional positions corresponding to the reverse and 
drive modes of the transmission, labeled R and D, respectively, are 
provided adjacent the apertures 20 and 27 for reasons which will be 
discussed in greater detail below. 
The transmission safety locking apparatus of the present invention further 
includes a slidable lock pin 6 which is retractable and extendable with 
respect to the gear shift lever 2. An actuator means is provided for 
retracting the lock pin 6 to the retracted position when activated. In the 
retracted position shown by reference number 6A in FIG. 5, the lock pin 6 
is disengaged from the arcuate section of the lever 2 thereby enabling the 
gear shift lever 2 to be rotated so as to change the selection of the 
transmission gears upon movement of the gear shift selector. 
Preferably, the actuator means comprises an electromechanical solenoid, one 
example of which is shown in FIG. 5. The electromechanical solenoid is 
formed of a magnetic core 24 surrounding an electric coil 5 wound in a 
plurality of turns. The coil 5 is wound within a bobbin 26 mounted 
interiorly within the core 24. A bore 28 is formed interiorly within the 
coil 5. Leads 12 and 13 connected to the end of the coil 5 extend outward 
from the coil 5 for connection to an electric circuit, described 
hereafter, for activating the actuator means. 
The lock pin 6, which is formed of a magnetic material, is slidably 
disposed through the core 24 interiorly within the coil 5, as shown in 
FIG. 5. The application of an electric current to the coil 5 induces a 
magnetic field in the core 24 which magnetically attracts the lock pin 6 
interiorly into the core 24 causing a retraction and disengagement of the 
lock pin 6 from the gear shift lever 2 and movement of the lock pin 6 to 
the retracted position shown by reference number 6A in FIG. 5. 
A biasing means 15, preferably a coil spring, is mounted exteriorly about 
the bobbin 26 and engages a metallic plate 9 mounted on one end of the 
lock pin 6 to normally bias the plate 9 and the lock pin 6 to the extended 
position. The magnetic field induced in the core 24 when an electric 
current is applied to the coil 5 overcomes the bias of the spring 15 to 
enable the lock pin 6 to be retracted to the position 6A shown in FIG. 5. 
In this position, the metallic plate 9 assumes the retracted position 
shown by reference number 9A in FIG. 5. 
It should be noted that the core 24 and coils may be mounted on the 
transmission housing 1 in any suitable position such that the lock pin 6 
is positioned to engage one of the apertures 20 or 27 in the gear shift 
lever 2 when the transmission is in the corresponding park or neutral 
modes of operation. In such modes of operation, the gear shift lever 2 
will be rotated to one of the positions shown in FIG. 2 such that the lock 
pin 6, normally biased to the extended position by the spring 15, will 
engage one of the apertures 20 or 27 locking the gear shift lever 2 from 
rotational movement. 
FIG. 4 depicts one mounting position of the core 24 and coil 5 on the 
transmission housing 1 in which the lock pin 6 extends outward from the 
housing 1 to engage the lever 2. An alternate mounting position is shown 
in FIG. 5 in which the core 25 and coil 5 are mounted exteriorly of the 
lever 2 such that the lock pin 6 moves toward the housing 1 to engage the 
lever 2. 
For added support, a guide plate 14 is connected to and extends outward 
from one end of the core 24. The guide plate 14 is spaced from the one end 
of the core 24 to form a channel 30 with the opposed end of the core 24. 
The gear shift lever 2 is pivotally movable within the channel 30. The 
guide plate 14 is engageable by the outer end of the lock pin 6 when the 
lock pin 6 is in the extended position to support the lock pin 6 and 
provide stability to lock the gear shift lever 2 in a fixed position. 
The transmission safety locking lever apparatus of the present invention 
further includes means, responsive to a predetermined pressure at which 
the vehicle brakes are applied, for connecting the actuator means to an 
electric power source to activate the actuator means to retract the lock 
pin 6 from engagement with the gear shift lever 2. In a preferred 
embodiment, a brake pressure sensor means 32, as shown in FIG. 6, is 
mounted in the vehicle brake hydraulic system. The brake pressure sensor 
means 32 is in the form of a pressure switch which closes when a 
predetermined pressure is reached in the vehicle brake system evidencing a 
predetermined degree of activation of the vehicle brakes. Preferably, such 
a predetermined pressure and degree of activation of the vehicle brakes 
are such that the vehicle is stopped or nearly stopped to ensure safe 
operation of the vehicle. The brake pressure sensor means 32, as shown in 
FIG. 6, is connected in series with an ignition key switch 34 and an 
electric power source 36, such as the vehicle's battery. The pressure 
switch 32, the ignition switch 34 and the battery 36 are serially 
connected between ground and the coil 5 of the actuator means. 
Thus, electric current is applied to the coil 5 to retract the lock pin 6 
from engagement with the gear shift lever 2 only when a predetermined 
pressure indicating a certain degree of actuation of the vehicle brakes 
has been sensed by the pressure sensor 32 and the vehicle ignition switch 
34 is on. Without the brakes being applied, the pressure sensor switch 32 
will be open thereby preventing current from being applied to the coil 5. 
This causes the lock pin 6 to remain in its extended position under the 
bias of the spring 15. 
In operation, it will be assumed that the vehicle brakes are not initially 
applied. The vehicle ignition is first activated as evidenced by a closure 
of the ignition switch 34 with the transmission is in a park position. At 
this time, no current is flowing through the coil 5 such that the actuator 
means is deactivated. The biasing spring 15 urges the lock pin 6 to its 
extended position, shown in FIG. 5, in which the lock pin 6 engages and 
passes through the aperture 20 in the gear shift lever 2 into the guide 
plate 14. This locks the gear shift lever 2 in a fixed position in the 
park mode of the transmission regardless of any force exerted on the gear 
shift selector to move the transmission to other positions. 
When the vehicle brakes are applied with a sufficient amount of pressure, 
as evidenced by a closure of the pressure switch 32, current will be 
applied to the coil 5 inducing a magnetic field in the core 24 and 
magnetically attracting and retracting the lock pin 6 to position 6A into 
the core 24. This disengages the lock pin 6 from the aperture 20 in the 
gear shift lever 2 and enables the gear shift lever 2 and the transmission 
to be moved to any operating position including reverse, neutral or drive 
as desired by the operator of the vehicle through movement of the gear 
shift selector. This selection of a particular transmission operating mode 
is possible only as long as the vehicle brakes are applied with a 
predetermined amount of pressure which causes the pressure switch 32 to 
remain closed and electric current applied to the coil 5. 
Whenever the vehicle brakes are released, the pressure switch 32 will open 
disrupting current flow to the coil 5 and deactivating the actuator means. 
This causes the lock pin 6 to move to its extended position under the 
influence of the biasing spring 15. 
If a neutral position has been or is selected by the operator of the 
vehicle, the aperture 27 in the gear shift lever 2 will be aligned with 
the lock pin 6 such that the extension of the lock pin 6 by the biasing 
spring 15 will cause the lock pin 6 to engage the aperture 27 in the gear 
shift lever 2. Alternately, if the operator has selected either reverse or 
drive modes of operation, the extension of the lock pin 6 under the 
biasing spring 15 will cause the lock pin 6 to strike a solid portion, 
labeled R or D in FIG. 3, located adjacent to the apertures 20 and 27 in 
the gear shift lever 2. The gear shift lever 2, thus, is free to be moved 
to any other position since the lock pin 6 is not in a fixed engagement 
with one of the apertures 20 and 27. Thus, at any time, the operator of 
the vehicle can move the gear shift selector to select park or neutral 
positions causing rotation of the gear shift lever 2 and an engagement of 
the lock pin 6 with one of the apertures 20 and 27 in the gear shift 
lever. 
The transmission safety locking lever apparatus of the present invention 
also includes a start interlock which prevents the vehicle's engine from 
being started until the transmission is in either a park or neutral 
position and the lock pin 6 is engaged with one of the apertures 20 and 27 
in the gear shift lever 2 locking the gear shift lever 2 and the 
transmission in the park or neutral position. 
The start interlock comprises a pair of contacts 10 and 11 which are 
mounted so as to be spanned and engaged with the contact plate 9 connected 
to the lock pin 6 when the lock pin 6 is in the extended position shown in 
FIG. 5. As shown in FIG. 6, the leads from the contacts 10 and 11 are 
serially connected with the ignition switch 34, the vehicle battery 36 and 
the vehicle engine starter 38. In this circuit, the engine starter 38 may 
be activated only when the lock pin 6 is engaged with one of the apertures 
20 and 27 in the gear shift lever 2 which locks the transmission in a 
fixed position and prevents it from being shifted to another gear. This 
provides safe operation of the vehicle during starting which would prevent 
inadvertent movement of the vehicle if the vehicle was started and the 
transmission was not in either park or neutral position. 
In summary, there has been disclosed a unique transmission safety locking 
lever device which prevents the transmission from being shifted from park 
or neutral into either drive or reverse unless the vehicle brakes are 
applied. This provides safe operation for the vehicle since operator 
action is required to positively move the transmission to forward or 
reverse modes of operation. 
The transmission safety locking lever apparatus of the present invention is 
simple in construction and contains a minimal number of components for a 
low manufacturing cost. Further, the minimal number of components 
contribute to ease of installation and enable the transmission safety 
locking lever apparatus of the present invention to be used with many 
different transmission configurations without undue modification.