Patent Application
20140209438
Exemplary embodiments of this invention generally relate to electrical actuation systems and, more particularly, to a lock-out solution for an electrical actuation system of an aircraft.
During installation, service and maintenance of powered equipment, service personnel, such as electricians for example, must assure that the equipment being worked on is isolated from its power source. Although the power source is usually electrical, other power sources such as mechanical, hydraulic, pneumatic, chemical, and thermal may be involved.
When the power source and the equipment are arranged generally at the same location, isolation is not difficult. However, it is common that the power source, e.g. a breaker box, is located relatively far away from the equipment in need of service. Thus, it is possible that after the equipment is isolated at the power source it may be inadvertently powered on by other personnel who do not know that the equipment was intentionally powered off.
“Lock-out” and “Tag-out” refer to safe methods for the complete power isolation of equipment during maintenance or service work. OSHA regulations require the use of locks or tags at control points, such as breaker boxes for example, as warning devices to ensure that personnel are not injured from accidental machine start-ups. While many lock-out and tag-out solutions perform well, none are fool proof. For example, tag-out solutions assume that all personnel can read the same language. Lock-out solutions are often difficult to install and require that the device being locked is pre-equipped with a lock receiving apparatus. In addition, lock-out solutions may be bypassed intentionally or accidentally without the knowledge of the affected personnel.
As aircrafts convert systems previously using hydraulic controls to new electrical solutions, issues arise in preventing unintended start-up of equipment. Many of these systems on an aircraft have large moving surfaces that can create a safety hazard if they were to accidentally move while maintenance personnel are working on them or a neighboring engine. Hydraulic lockout valves were previously used in the hydraulic lines to prevent fluid flow, and therefore movement of these large surfaces. Because these systems are now electrically actuated, an electrical lock out mechanism configured to safely lock out the system by removing power is desired.
According to one embodiment of the invention, an electrical switch for use in an electrical actuation system is provided including a switch box having an upper surface with an opening. A stem guide is coupled to the switch box adjacent the opening. A lock out mechanism is received within a central bore of the stem guide and the opening. The lock out mechanism is configured to move between a first position and a second position to selectively break a flow of power through the electrical switch. A pin is configured to couple the lock out mechanism to the stem guide in one of the first position or the second position.
According to another embodiment of the invention, an electrical actuation system of an aircraft is provided including a power feed line configured to supply power to at least one downstream component. An electrical switch is arranged along a portion of the power feed line. The electrical switch includes a switch box having an upper surface with an opening. A stem guide is coupled to the switch box adjacent the opening. A lock out mechanism is received within a central bore of the stem guide and the opening. The lock out mechanism is configured to move between a first position and a second position to selectively break a flow of power in the power feed line. A pin is configured to couple the lock out mechanism to the stem guide in one of the first position or the second position.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
Referring now to the FIGS., an electrical switch 20, such as from an electrically actuated thrust reverser system or an electrically actuated variable area nozzle system of an aircraft is illustrated. In the illustrated embodiment, the electrical switch 20 is a three pole single throw switch (3PST) having an auxiliary switch for position status. Alternative electrical switches, such as a four pole single throw switch (4PST) that uses the fourth pole for position status for example, are within the scope of the invention. Configured to be mounted to a panel (not shown) in a conventional manner, the electrical switch 20 is arranged within a power feed line of the electrical actuation system and supplies power to a downstream component of the actuation system, such as a motor for example.
A stem guide 30 having a central bore 32 is aligned with and positioned next to an opening (not shown) in the upper surface 24 of the switch box 22. In one embodiment, the stem guide 30 is threadably coupled, such as with a mounting nut 31 for example, to a portion of the switch box 22 extending perpendicularly from the upper surface 24 adjacent the opening. In addition, the stem guide 30 includes a through hole 34 configured to receive a pin 36.
The electrical switch 20 additionally includes a lock out mechanism 40 configured to selectively create a break in the power feed line. In the illustrated, non-limiting embodiment, the lock out mechanism 40 is a generally cylindrical stem having a button feature 42 and a shaft 44; however, alternative configuration, such as including a lock out mechanism that pivots for example, are within the scope of the invention. A first portion 46 of the shaft 44, positioned next to the base 42, includes a first color, such as green for example, and an adjacent second portion 48 of the shaft 44 includes a second color, distinct from the first color, for example red. The shaft 44 additionally includes a first through hole 50 and a second through hole 52 (
The shaft 44 of the lock out mechanism 40 is slidably positioned within the bore 32 of the stem guide 30, as well as the opening in the upper surface 24 of the switch box 22. In the illustrated embodiment, the lock out mechanism 40 is configured to translate about an axis X between a first position (
Similar to the through hole 34 of the stem guide 30, the first and second through holes 50 of the lock out mechanism 40 are also configured to receive the pin 36. Therefore, the diameter of the pin 36 is generally smaller than the diameter of each of the through holes 34, 50, 52. The pin 36 is configured to couple the shaft 44 of the lock out mechanism 40 to the stem guide 30 to retain the lock out mechanism 40 in a desired position relative to the switch box 22. In one embodiment, a snap ball 58 is located adjacent a first end 54 of the pin 36 to prevent unintended movement of the pin 36 once inserted through the stem guide 30 and lock out mechanism 40 (
When the lock out mechanism 40 is in the first position, as illustrated in
In the second position, as illustrated in
To move the lock out mechanism 40 between the first position and the second position, a mechanic removes the pin 36 from the stem guide 30 and shaft 44 of the lock out mechanism 40 and then applies a force to the lock out mechanism 40. Once reaching the new position, the pin 36 is positively reinserted through the stem guide 30 and the lock out mechanism 40. In one embodiment, a mechanic pulls the lock out mechanism 40 to move the lock out mechanism 40 from the first position to the second position, and pushes the lock out mechanism 40 to move the lock out mechanism 40 from the second position to the first position.
The electrical switch 20 includes an electrical lock out mechanism 40 for use in an electrically actuated system of an aircraft. The color coding of the lock out mechanism 40 will easily indicate to a mechanic if the switch 20 is either in normal mode operation or safety mode operation. By including a snap ball at an end 54 of the pin 36, the pin 36 positively retains the lock out mechanism 40 in a position. The positive locking pin provides a visible locking feature
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
