Three position electrically operated actuator

A three position electrically operated actuator has a self centering system so that if power is off for the actuator, it returns to a central position. The actuator comprises a center cavity with a first solenoid on one side and a second solenoid on the other side, a shaft extends through the center cavity and is joined to a first magnetic core of the first solenoid and a second magnetic core for the second solenoid. The shaft has a connection at least at one end for connection to a gearbox or the like. When the first solenoid is energized the shaft moves axially in one position so the connection is at a first position, when the second solenoid is energized, the shaft moves axially in the opposite direction so the connection is at a second position. A coil spring is provided in the cavity, and when neither solenoid is energized the spring moves the shaft so the connection is in a third position midway between the first position and the second position.

TECHNICAL FIELD 
The present invention relates to an actuator which is electrically 
operated, preferably by a solenoid, and has a neutral position which is 
engaged when the power is off. The actuator is suitable for marine gearbox 
applications. 
BACKGROUND ART 
In marine applications wherein a gearbox is used to change the direction of 
rotation for propeller shafts, actuators are generally used to change the 
gear drive arrangement. In most cases gearboxes have three positions, 
forward propulsion, reverse propulsion and neutral. 
Actuators presently used for changing gear drives in marine applications 
may be hydraulic or pneumatic operated. Provisions are made in certain 
instances for returning the gear change lever to the neutral position if 
there is a sudden loss of hydraulic or pneumatic pressure. This avoids 
situations where a power breakdown leaves the propulsion engaged. 
Up until the present time there has been no electrically operated actuator 
which has a self centering arrangement so that if there is a power failure 
the actuator returns a gear change lever to the neutral position. There is 
definitely a requirement for such an actuator control for safety reasons 
and to permit the use of electrical power for controlling a ship thus 
avoiding the necessity of having to have either pneumatic or hydraulic 
controls. 
DISCLOSURE OF INVENTION 
It is an aim of the present invention to provide an electrically operated 
self centering three position actuator with an end connection suitable for 
use in connecting to a gear change lever for a marine gearbox. The 
actuator has two electrical solenoids, one solenoid to move the end 
connection to a first position, the second solenoid to move the end 
connection to a second position. A self centering spring is provided to 
move the end connection to a neutral or third position being a third 
position when both the solenoids are de-energized. Thus, should a power 
failure occur when the end connection is in either the first or the second 
position, the spring automatically returns the end connection to the 
neutral or third position which is arranged to be the neutral position for 
the gear change lever. 
The present invention provides a three position electrically operated 
actuator comprising a center cavity with a first solenoid on one side and 
a second solenoid on the other side, a shaft extending through the center 
cavity and joined to a first magnetic core of the first solenoid and a 
second magnetic core of the second solenoid, the shaft having connection 
means at least at one end, the first solenoid when energized adapted to 
move the shaft axially in one direction to position the connection means 
at the end of the shaft in a first position, the second solenoid when 
energized adapted to move the shaft axially in the opposite direction to 
position the connection means at the end of the shaft in a second 
position, spring means within the center cavity, flange means located 
about the shaft on both sides of the spring means, the flange means 
compressing the spring means when the shaft is moved axially to locate the 
connection means in the first position or the second position, and upon 
deactivation of the solenoids, the spring means moving the shaft so the 
connection means at the end of the shaft is moved to a third position 
midway between the first position and the second position.

The three position electrically operated actuator 10 shown in FIGS. 1 and 2 
has a center cavity 12 with side walls 14 on both sides to which are 
attached a first solenoid 16 and a second solenoid 18. The side walls 14 
both have bosses 20. A central shaft 22 extends through both solenoids 16 
and 18 and the center cavity 12. At one end the shaft 22 has a stud 
connection 24 to a connection link 26 which becomes the connection for the 
actuator 10. It is this connection link 26 which is connected to a gearbox 
(not shown). 
A further stud connection 28 is located at the other side of the shaft 22. 
The studs 24 and 28 and the shaft 22 are joined to cylindrical magnetic 
cores 30 by which represent the solenoid cores for the solenoids 16 and 
18. The shaft 22 passes through the cores and joined to the cores by screw 
threads. A compression coil spring 32 is positioned in the cavity 12 about 
the shaft 22 and has flange collars 34 having flange diameters about the 
same size as the coil spring 32 positioned on both sides of the coil 
spring 32. The flange collars 34 have cylindrical portions 36 integral 
therewith which slide in aperture in the walls 14 of the cavity 12 when 
either solenoid is energized. 
Expandable rubber protective covers 40 are provided on both sides of the 
solenoids 16 and 18 connected to the studs 24 and 28 exteriorly of the 
solenoid magnetic cores 30 to protect dirt from getting on the cores 30 
when the shaft 22 moves. 
Electrical terminals 42 are provided on the cylindrical exterior of the 
cavity 12 for electrical connections to the magnetic coil windings of the 
solenoids 16 and 18 through apertures 44 in their exterior shell. The 
center cavity 12 is preferably sealed to prevent dirt entering therein. 
In operation when neither solenoid is energized, the connection link 26 is 
in the neutral or third position as shown in FIG. 1, and the spring 32 
pushes against both flange collars 34 so the cylindrical portions 36 push 
against the two solenoid magnetic cores 30. The compression spring 32 is 
fully expanded and the actuator is stable in the neutral or third 
position. 
FIG. 2 shows first solenoid 16 energized, the solenoid magnetic core 30 
immediately moves to the right. The cylindrical portion 36 and flange 
collar 34 also move to the right compressing the spring 32. The shaft 22 
being connected to the magnetic core 30 also moves to the right, so the 
connection link 26 moves to a second position which when connected to a 
gearbox may represent either forward or reverse for a marine drive. The 
second solenoid 18 is not energized when the first solenoid 16 is 
energized so the solenoid core 30 for the second solenoid 18 simply moves 
because it is connected to shaft 22. The first solenoid 16 has sufficient 
power to compress the spring and provide sufficient force to move the 
connection link 26. 
When the solenoid 16 is de-energized the spring 32 immediately pushes the 
flange collar 34, cylindrical portion 36 and solenoid magnetic core 30 to 
return the shaft and the connection link 26 to the neutral or third 
position. When the second solenoid 18 is energized, the first solenoid 16 
is not energized and the shaft 22 moves in the other direction moving the 
connection link 26 to a first position. Thus, three positions are 
provided, the first and second positions when the two solenoids 16 and 18 
are energized, and the neutral or third position when both solenoids are 
not energized and the spring 32 returns the shaft 22 and the connection 
link 26 to the third or neutral position. 
Another embodiment is shown in FIGS. 3 and 4 wherein a manual override 
mechanism is provided to change positions of the actuator should there be 
a power failure and neither of the solenoids 16 or 18 can be energized. 
The connection link 26 is joined to connecting links 50 which rotates 
freely around output shaft 54. On top of the input lever 52 is a notch 56 
into which fits a latch plunger 58 as shown in FIG. 4. The latch plunger 
58 is connected to a manual handle 60 concentric about a manual lever 62, 
and spring loaded with a coil spring 64 which maintains the latch plunger 
58 in the notch 56 in the input lever 52. The manual lever 62 fits into 
the output shaft 54 at its base so that when the lever 62 is pivoted about 
the output shaft 54, the output shaft rotates and changes gears. 
A latch lever 66 acts as a guide and rotates about the shaft 54 with the 
manual lever 62 joined to it. Apertures 68,69 are provided on both sides 
of the manual lever 62 in the latch lever 66. One aperture 68 contains the 
latch plunger 58 which extends down to engage in notch 56 and a second 
short plunger extends down from the handle 60 passing only through the 
aperture 69 in the latch lever 66. 
Beneath the second aperture 69 is a sector latch plate 72 which is fixed 
and has notches 74 representing the three positions of the actuator. 
When the handle 60 is in the position shown in FIG. 4, the connecting links 
50 move the input lever 52 when the actuator moves between positions, and 
the input lever 52 through the latch plunger 58, handle 60 and manual 
lever 62 changes the gears by rotation of the output shaft 54. 
If there is a power failure, or if there is a need to operate the gear 
change manually, the handle 60 is raised, compressing spring 64 until the 
latch plunger 58 is free of the notch 56 and the aperture 68 in the latch 
lever 66. The handle 60 is then rotated about the manual lever 62 and then 
released so the latch plunger 58 passes through aperture 69 and engages in 
one of the notches 74. The actuator mechanism is then completely 
disconnected from the output shaft 54. The handle 60 can then be pivoted 
to any of the three positions, engaging in one of the three notches 74 in 
the latch plate 72 thus changing gears manually. 
In order to re-engage the actuator, the handle 60 is raised and rotated 
through 180.degree. so the latch plunger 58 again engages in the notch 56 
in the input lever 52. 
Various changes may be made to the embodiments shown herein without 
departing from the scope of the present invention which is limited only by 
the following claims.