Abstract:
An electrical lock for a moving part prevents the part from moving unless a device controlled by the part is in a safe mode. The invention may find a use in many different environments. The specific example here described is a set of reverse thruster doors on a jet engine. The lock prevents a throttle from applying or removing power unless the reverse thruster doors are properly set for such application or removal of power. The lock is removed when the doors reach full deployment or retraction, respectively, which is appropriate for the direction in which said throttle is moved. These functions are provided under the control of a single solenoid.

Description:
FIELD 
     This invention relates to locks for automatically controlling the movement of a bi-directional mechanical part, and more particularly--but not exclusively--to bi-directional, electric safety lock devices for fail-safe operation in potentially dangerous conditions, such as on the throttle of a jet aircraft, for example. 
     BACKGROUND 
     The invention may find use in almost any place where it is necessary to lock a mechanical part in an immobile position until it is safe for that part to move. In particular, the invention is especially useful when size and weight are serious constraints. For example, every ounce that is added to an airplane demands seven or more additional ounces for support, fuel, engine power, etc. Therefore, the inventive safety lock should be as light and as small as it reasonably can be considering the task which it is designed to perform. 
     However, to give a concrete example of one place where the invention may find special utility, reference may be made to operation of the reverse thrusters on a jet aircraft and to the deployment and retraction of doors behind the jet engine for reverse thrust. For example, when the jet plane is coming in for a landing, many sensors detect things such as weight on the wheels on touch down, the rotational speed of the wheels, and the like. After touchdown, the pilot wants to initiate deployment of thrust reversing doors behind the engine and increase thrust in order to slow the airplane to assist braking on the runway. Also, in the event of a &#34;touch and go&#34; type go around (taking off again after touching down), he wants to be certain that the doors are fully retracted, before he goes to full throttle (forward thrust). 
     When the pilot moves the levers backward for power with reverse thrust, it is necessary to block movement of the levers until the reverse thrust doors are fully deployed. Otherwise, he might cause power to be applied at a point where the applied force could override the thrust reverse doors and inadvertently apply forward thrust at a critical stage when available runway is running out. Likewise, after the touch down and full deployment of the thrust reverse doors, the pilot might see something on the runway and move to full throttle in order to abort the landing and take off. The full throttle power cannot be allowed to take effect until the thrust reverse doors are stowed. Otherwise, instead of taking off inadvertent reverse thrust would be applied. 
     Of course, the invention is equally applicable to almost any similar situation where a mechanical part must be restrained from immediate operation, and yet be enabled for an immediate response as soon as it is safe or desirable to do so. One can easily imagine many other examples of situations where a part is locked until sensors of various sorts signal the ability of a mechanical part to move. 
     In each of these and similar situations, it is necessary to lock the moving part against motions in either of opposite directions of its possible excursion until such motion is safe or desirable. There are many sensors, that respond to such things as the deployment or retraction of the thrust reverse doors, which may be connected to remove the lock upon the movable part as soon as it is safe to do so. The invention should be able to work with most of these sensors. 
     SUMMARY 
     Accordingly, an objective of the invention is to provide a unique combination of fail safe mechanisms designed to fulfill a function within restricted design restraints, especially safety restraints. Here, a requirement is to provide a mechanism having an electromechanical latch which can be configured to operate in two independently triggered positions and to be sensitive to safety lock outs. It is desirable to accomplish these objectives with few moving parts. In this connection, it is prerequisite to accomplish this in conjunction with minimized size and weight. 
     In keeping with the aim of the invention, these and other objectives are provided by a mechanism comprising a solenoid actuated pivoting arm which locks a rotating cam in either of two positions. When the cam is rotated in one direction, a lock out is encountered when the solenoid is energized. Similarly, when the cam is rotated in a counter direction, it causes a lock out when the solenoid is de-energized. The release from either lock out condition is achieved by reversing the energized or de-energized state of the solenoid, as appropriate. Isolation between the two lock out conditions is achieved responsive to a position sensitive cam operated switch which changes over the energizing/de-energizing circuit depending upon the angular position of the cam. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A preferred embodiment of the invention is shown in the attached drawing, in which: 
     FIG. 1 is an elevation showing the inventive mechanism in a switching neutral position, and is provided primarily for a description of the various parts; 
     FIG. 2 is yet another showing of the invention in a forward lock out position; 
     FIG. 3 is a similar elevation showing the invention in a reverse lock out position; 
     FIG. 4 schematically shows a jet engine with its reverse thruster doors fully retracted; and 
     FIG. 5 shows the jet engine with its reverse thruster doors fully deployed. 
    
    
     DESCRIPTION 
     Purely by way of example, the invention is here described in connection with the throttle 20 of a jet aircraft having reverse thruster doors which are deployed to slow the aircraft. More particularly, the throttle has a lever arm 22 which may rotate forward or reverse about a pivot point 24 in order to apply or remove jet engine power. In normal flight, the engines are controlled by an auto throttle, which includes the control of a motor 26 that automatically drives the throttle lever arm 22 in a forward thrust regime dependent upon a sensed need for power. If the pilot wishes to temporarily override the automatic throttle feature, he presses a push button 28 while gripping knob 30 in order to move the throttle lever 22. If he wishes to permanently enable or inhibit the automatic throttle operation by motor 26, he operates a manual switch 32. A separate trigger lever releases the throttle lever into the reverse thrust range and thus initiating subsequent deployment or retraction of the reverse thruster doors, shown in FIGS. 4, 5. The parts (of FIG. 1) described thus far are conventionally found on a jet aircraft throttle assembly. 
     The invention adds a solenoid 36 which controls the enablement of the throttle. An example of a suitable solenoid is found in U.S. Pat. No. 5,836,001, filed Sep. 8, 1997, and granted Nov. 10, 1998, by Jerry D. Hielkema, Gary A. Sparks and David J. Treadwell and entitled &#34;Solenoid Having Multistage Plunger&#34;. 
     Means are provided for inhibiting or enabling a movement of the throttle depending upon whether or not an unsafe condition exists at the time when an attempt is made to move the throttle. In greater detail, the solenoid controls a three prong lock out latch arm 38 which pivots about point 39 to engage a lock out cam 40. A control cam 42 and a micro switch 44 detects and discriminates between forward and reverse throttle movement. A pair of inhibiting means in the form of rollers 45 and 46, are mounted on the ends of two of the three prongs of lock out latch 38 to selectively engage a lock out face on lock out cam 40. 
     A single tooth drive gear 47 is mounted to rotate about point 24 in unison with the throttle lever arm 22. As gear 47 turns, pinion 48 rotates to turn a control cam 42 having a profile which indicates whether the throttle is moved in a forward direction (FIG. 2) or a reverse direction (FIG. 3). A micro switch activator 52 has a cam follower activator 54 which responds to the profile of the cam 42 in order to operate or release micro switch 44 which, in turn, is connected to energize or de-energize solenoid 36. 
     It should be noted that in the neutral position of FIG. 1, the plunger 60 of solenoid 36 is in the center of slot 62 on one prong of the three prong lock out latch arm 38. If the throttle 20 is pulled forward (Direction A--FIG. 2), pinion 48 (FIG. 1) turns cam 42 so that its profile 50 pushes cam follower activator 54 down (as viewed in FIG. 1). Micro switch 44 operates and closes its contacts which passes a 28v energizing signal to solenoid 36 if the aircraft thrust reversers are not fully stowed. As the solenoid 36 is operated (FIG. 2), plunger 60 is pulled into the solenoid coil which moves its connection towards the right hand end of slot 62 as it pulls the three prong lock out latch arm 38 in Direction C. The end of the prong which has a roller 46 is moved in direction D. As the throttle is rotated in direction A, the roller 46 is pressed against a stop or lock out face 64 on the lock out cam 40 in order to inhibit a movement of the throttle in Direction A. 
     If the throttle 20 is pushed back (FIG. 3), in Direction B, pinion 48 (FIG. 1) is rotated in an opposite direction to turn cam 42. The cam follower activator 54 moves up (as viewed in FIG. 1) to release the micro switch 44 which opens its contacts and, if thrust reversers are not fully deployed, then, in turn, de-energizes solenoid 36. When solenoid 36 releases (FIG. 3), spring 70 pushes the plunger 60 to an extended position. In this position, the throttle cannot be applied because the solenoid plunger 60 raises the three prong latch arm 38 which presses down roller 45 to capture the reverse lock out face 68 and inhibit the movement of the throttle in Direction B. 
     Hence, it is seen that, when the solenoid 36 is energized (FIG. 2), plunger 60 is retracted, three prong lock out latch arm 38 is pulled down, and roller 46 is lodged against the forward stop or lock out face 64 to prevent the throttle from being pulled forward (Direction A). When the solenoid 36 is de-energized (FIG. 3), the plunger 60 extends, the three prong latch arm 38 is pushed up by spring 70, and roller 45 is lodged against reverse lock out face 68 to prevent the throttle from being pushed back (Direction B). 
     As pointed out above, the inventive mechanism may be used in any of many installations where this type of action is required. However, the specific example of reverse thruster doors on a jet engine has been cited to show one use. In greater detail, FIG. 4 schematically shows a jet engine 82 with the reverse thruster doors 84, 86 retracted, to close sensor contacts symbolically shown at 88, 90. Before these sensor contacts close, micro switch 44 (FIG. 1) contacts 92 are open and the solenoid 36 is de-energized to inhibit the jet engine from responding to the reverse thrust throttle command. After both reverse thruster doors are fully deployed, the two sensor contacts 88, 90 complete an AND circuit 93 to energize the solenoid, which releases the lock out of FIG. 3 to enable the jet engine to respond to the reverse thrust command. Likewise, FIG. 5 schematically shows jet engine 82 with its reverse thruster doors 84, 86 fully deployed to close sensor contacts symbolically shown at 90, 94. Before these sensor contacts are closed, the micro switch contacts 92 are closed to energize the solenoid 36 and inhibit a full throttle response. These sensors indicate whether the reverse thruster doors are retracted or extended, but they could be other sensors on any other parts which require the kind of lock out that has been described. 
     In operation, on landing (FIG. 2), lever 34 is manually extended to permit throttle movement into reverse thrust range. Reverse thrust power is applied against the reverse thruster doors to slow the forward roll of the airplane. 
     On take off (FIG. 3), there would be a problem since, if the reverse thruster doors are deployed, a forward operation of the throttle would produce catastrophic results. Hence, the solenoid 36 is de-energized and roller 45 blocks the reverse lock out face 68. When the reverse thruster doors are fully retracted, a sensor energizes the solenoid 36 to lift roller 45 away from the reverse lock out face 68. Then, the throttle lever arm 22 can be moved in Direction B. 
     Those who are skilled in the art will readily perceive how to modify the invention. Therefore, the appended claims are to be construed to cover all equivalent structures which fall within the true scope and spirit of the invention.