Diesel engine shutoff actuator

An actuator is provided to selectively turn a diesel engine governor shutoff shaft to fuel "off" or fuel "on" position in response to keyswitch operation. An electric motor coupled through a gear train to a shutoff lever turns the lever to "on" or "off" position. A relay circuit controls the motor operation in response to keyswitch position and shutoff lever position. A feedback element moving with the shutoff lever mechanically interrupts the relay circuit by overriding the relay contact state to turn off the motor whenever the shutoff lever reaches an "on" or "off" position.

This invention relates to a diesel engine shutoff actuator and in 
particular to such an actuator which turns fuel on or off in response to 
keyswitch operation. 
In order to turn off the diesel engines in trucks it has been the 
conventional practice to provide a manually operated cable which is 
effective to turn off the engine fuel when operated. Thus, the operation 
of a truck differs from that of an automobile where merely operation of a 
keyswitch is required to start or stop the engine. It has been proposed to 
operate a diesel fuel shutoff mechanism by an electric motor responsive to 
a keyswitch, however, that proposal required a complicated electrical 
circuit for controlling the motor. 
It is, therefore, an object of this invention to provide a diesel fuel 
shutoff actuator with a simple circuit responsive to a keyswitch for 
operating the actuator motor. 
The invention is carried out by providing an electric motor coupled with a 
fuel shutoff control member, a relay circuit responsive to a keyswitch 
position for driving the motor in a direction to move the shutoff member 
to "on" or "off" position and a mechanical feedback element to interrupt 
the motor circuit by operation of the relay switches when the shutoff 
control member reaches "on" or "off" position.

Referring to FIG. 1 a molded polymer housing 10 is configured to hold a 
number of operating elements to be described below and to support each 
elemnt in its operating position. The housing includes a cover, not shown, 
which complements the support function of the housing. Apertures 12 are 
provided for securing the cover to the housing 10. A printed circuit board 
14 nested in the housing supports a reversible DC permanent magnet motor 
16 which is connected to the circuit board 14 by conductors 18 and 20. The 
output shaft of the motor 16 is coupled by a gear train 22 to a screw 
shaft 24 which extends longitudinally of the housing. The screw shaft is 
rotatably carried by a pair of brass journals 26 which are nested in the 
molded housing 10. One end of the screw shaft 24 extends outside the 
housing and is secured to a knob 28 which turns with the shaft. The other 
end of the shaft 24 has a worm gear thread 30 formed thereon. A shutoff 
lever or control element 32 carries a gear segment 34 which meshes with 
the thread 30 for operation thereby. The lever 32 has hub portions 36 
extending from either side which are journalled in apertures, not shown, 
in the housing 10 and its cover to thereby permit rotation of the lever 32 
upon operation of the screw shaft 24. A bore 38 in the shutoff lever 
concentric with the hub 36 contains the diesel engine governor shutoff 
shaft 40. A clamp 42 integral with the shutoff lever 32 securely fastens 
the shutoff shaft 40 to the shutoff lever 32 to rotate therewith. Thus, 
rotation of the motor 16 results in rotation of the shutoff lever 32 and 
the shaft 40. 
The printed circuit board 14 has three electrical conductors 44 connected 
thereto which extend through the housing. The printed circuit board also 
carries two relays 46 and 48. As shown in FIGS. 1 and 2, those relays 
include spring biased armatures 50 and 52 respectively which carry 
corresponding movable contacts 54 and 56. Relay 46 has two stationary 
contacts 58 and 60. The movable contact 54 is spring biased against the 
contact 58 but when the coil of the relay is energized, the movable 
contact is pulled by the magnetic field of the coil against the contact 60 
and away from the contact 58. In the same way the relay 48 has a fixed 
contact 62 which is normally closed with respect to the movable contact 56 
and in stationary contact 64 which is normally open with respect to the 
movable contact. 
As shown in FIG. 2, the gear segment 34 carries on its under surface a pair 
of control pins 66 and 68. A feedback element or member 70 formed of 
insulating material selectively engages the armatures 50 and 52 of the 
relays and also engages the control pin 66 and 68 so that the movement of 
the shutoff lever 32 can cause longitudinal sliding of the control element 
70 to effect selective mechanical operation of the relay armatures 50 and 
52. The element 70 is Z-shaped and has an upper bar 72 extending above the 
relays and a lower bar 74 extending beneath the gear segment 34 to engage 
the pins 66 and 68. A cavity 76 in the bar 74 defines walls 78 and 80 
which are each engaged by a control pin to effect movement of the control 
element 70. The cavity 78 is considerably larger than the control pins so 
that a lost motion connection is provided. Thus, the principle portion of 
the travel of the gear segment 34 does not cause movement of the feedback 
element 70 and only at the extremes of gear segment travel do the control 
pins engage the wall 78 or 80 to cause control element shifting. A finger 
82 depending from the top bar 72 and integral therewith extends alongside 
the armature 56 of relay 48 to force it toward the relay coil and engage 
the contact 56 with the contact 64 when the shutoff lever reaches its 
"off" position as shown in FIG. 2. A recess 84 in the upper surface of the 
top bar 72 contains a slot 86 which slidably retains a pin 88. The pin is 
held in the slot by a large head 90 which overlaps the sides of the slot 
86. The pin has a bifurcated end 92 straddling the relay armature 50 and 
is so arranged that when the shutoff lever is moved to the fuel "on" 
position the feedback element 70 and the pin 88 moves to the right and 
pulls the armature 50 away from the relay coil to close the contacts 54 
and 58. The pin and slot arrangement 86-88 allows a lost motion connection 
so that the pin 88 freely rides in the slot until the extreme fuel "on" 
position is reached whereupon the end of the slot 86 acts against the pin 
88 to affect relay switching. 
As shown in FIG. 3, the cavity 76 in the lower bar 74 is shaped so that the 
wall 78 engages only pin 66 when the gear sector 34 rotates to the extreme 
clockwise position whereas the pin 68 contacts the wall 80 when the gear 
sector 34 rotates to the extreme counterclockwise position. The fuel 
shutoff shaft 40 in the engine governor is spring loaded in such a way 
that when it is turning counterclockwise it is pushing against the spring 
force and thus tends to move more slowly and to stop movement more quickly 
during motor coastdown after motor de-energization than occurs in the 
clockwise direction where the spring loading actually assists the shaft 
rotation. Thus, there is a tendency to move the feedback element 70 
further during the coastdown period in the clockwise direction than in the 
counterclockwise direction. The use of the two pins 66 and 68 at different 
distances from the center of rotation of the lever compensates for the 
difference in motor coastdown since the pin 68 moves the feedback element 
70 further than does the pin 66 for a given increment of shutoff lever 
rotation. This features assures that when the circuit to the motor is 
interrupted by the movement of the control element 70 the continued 
movement of the element during the coastdown period will be the same 
regardless of the direction of rotation. Then the movement of the movable 
contact from its initial position to its final position will be the same 
in either case. The coastdown distance is just sufficient to cause the 
movable relay contact to break with one stationary contact and close with 
the other. 
Referring to FIG. 4 the circuit which actually resides on the printed 
circuit board 14 is shown in schematic form. The three conductors 44 (FIG. 
1) leading to the printed circuit board comprise a conductor 100 connected 
to a voltage source V+ and which is connected to the stationary contacts 
58 and 64 of the relays, a ground wire 102 which is connected to the 
stationary contacts 60 and 62 of the relays as well as to one side of the 
relay coils 46' and 48' and a third conductor 104 which is connected 
between the other side of the relay coils 46' and 48' and a keyswitch 106 
which, in turn, is supplied by V+ voltage. The conductors 18 and 20 
leading to the terminals of the motor 16 are connected to the movable 
relay contacts 54 and 56 respectively. 
When the keyswitch 106 is open, the relay coils are both de-energized and 
the movable contacts 54 and 56 are spring biased toward the contacts 58 
and 62 respectively. However, when the actuator is in the fuel "off" 
position, as shown in FIG. 4, the control element 70 is moved toward the 
left so that its finger 82 holds the contact 56 against the contact 64 
counter to the spring bias of the armature 52. An inspection of the 
circuit will reveal that in the fuel "off" condition the motor leads 18 
and 20 are both connected through the relays to the conductor 100 so that 
there is no current flow to the motor and it will be stationary. Circuit 
inspection will also reveal that when both movable contacts are in the 
relay energized position or state, i.e. engaging contacts 60 and 64, 
current will be supplied in one direction through the motor and when they 
are in the relay de-energized position current will flow in the opposite 
direction. Thus, the relay coils which are in parallel are concurrently 
energized or de-energized by keyswitch operation to establish motor 
rotation in a given direction. When the movable contacts are in opposite 
positions or states, there is no current flow to the motor. Thus, motor 
operation is halted by moving one movable contact to a position contrary 
to the state established by its coil. The relay switch is then functioning 
as a limit switch responsive to the feedback member 70. 
To move the actuator to the run or fuel "on" condition, the keyswitch 106 
is closed by the operator thereby energizing both relay coils 46' and 48'. 
Then the contact 54 is pulled against the stationary contact 60 and the 
movable contact 56 will be maintained in contact with the contact 64 even 
after movement of the control element 70. This state of the circuit allows 
current flow from the conductor 100 through the contacts of relay 48, the 
motor, and the relay 46 to ground thus causing the motor to rotate in a 
direction to move the fuel shutoff lever 32 clockwise. When that lever 
approaches its extreme fuel "on" position, the pin 66 engages the wall 78 
on the feedback element 70 to move the pin 88 against the armature 50 
thereby moving the contact 54 from the contact 60 to the contact 58 to 
stop the rotation of the motor 16. The terminal leads 18 and 20 of the 
motor are then in effect interconnected so that dynamic braking occurs to 
terminate the motor coastdown period. 
To move the actuator to fuel "off" condition, the keyswitch is opened by 
the operator to de-energize both relays. Then the contact 56 will engage 
contact 62 to supply current to the motor. When the control lever 32 
reaches the "off" position, the finger 82 will move contact 56 into 
engagement with contact 64 as shown in FIG. 4 to stop the motor. 
During engine operation an electrical failure will not interfere with the 
fuel flow since the motor 16 will not move if there is no voltage. 
However, the fuel can be shut off manually, if desired, by turning the 
knob 28 on the screw shaft 24.