GB1592071A

GB1592071A - Aircraft arrester apparatus

Info

Publication number: GB1592071A
Application number: GB1073/77A
Authority: GB
Original assignee: TI ANDERSTON CLYDE Ltd
Current assignee: TI ANDERSTON CLYDE Ltd
Priority date: 1977-12-22
Filing date: 1977-12-22
Publication date: 1981-07-01

Description

(54) AIRCRAFT ARRESTER APPARATUS (71) We: TI ANDERSTON CLYDE LIM ITED (formerly Anderston Clyde Engineers Limited), a British Company of P.O. Box No.

11, Ince, Nr. Wigan, Lancashire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to aircraft arrester apparatus of the type comprising an arrester net supported between two booms which can be moved rapidly from lowered to raised positions to suspend the net across a runway.

In known aircraft arrester apparatus of this type, each of the booms is pivotally connected to the ground and is rotated between the lowered and raised positions by an electric motor which has its drive shaft connected directly through reduction gearing to the boom. The motor is a high speed motor with a high starting torque in order to swing the loaded boom rapidly up and down, and because of this, relatively large shock forces are produced when accelerating from a stationary lowered or raised position and when decelerating and braking when the boom reaches its raised and lowered positions. An object of the present invention is to provide improved aircraft arrester apparatus in which these shock forces are reduced or eliminated.

This object is achieved according to the present invention by providing aircraft arrester apparatus of the aforesaid type in which each boom is raised and lowered by drive means comprising an actuator which is connected to the boom via a linkage mechanism having a velocity ratio which varies so as to pass through a maximum between the raised and lowered positions of the boom, whereby the angular speed of the boom increases away from and decreases towards these extreme positions and a minimal acceleration reaction and minimal stopping reaction is produced at each.

The invention therefore allows the use of a constant speed electric motor as the actuator, but varies the velocity characteristic of the motor through the linkage mechanism so as to move the boom slowly but with increasing velocity to the approximate mid point of travel and then rapidly but with decreasing speed towards the stop positions. The motor therefore need not have a high starting torque like that of the known apparatus, such low starting torque motors being less expensive.

Preferably, the linkage mechanism comprises a toggle linkage and makes use of the inherent variable velocity ratio characteristic of this linkage.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic front view of aircraft arrester apparatus according to the invention showing the arrester net raised, Figure 2 is an elnarged more detailed view of one of the booms of the apparatus of Figure 1, showing the boom in the lowered position, and Figure 3 is a plan view of the boom of Figure 2.

The illustrated aircraft arrester apparatus comprises a flexible net 1 that extends across a runway 2 and which is raised and lowered by a pair of booms 3 positioned one on each side of the runway. The booms are pivotally mounted about horizontal axes 4 at ground level and are actuated by drive means 5 so that they move in a common vertical plane between lowered positions, in which they point towards one another, and raised positions. Each boom carries a pulley 6 at its upper end that co-operates with a cable 7 fastened to the adjacent upper corner of the net and a fixed point 8 on the ground beyond the boom so that raising both booms simultaneously lifts the net off the ground to the raised position shown in Figure 1. The net 1 is also connected via cables 9 to energy absorbing units 10 on each side of the runway that retard movement of the net should an aircraft hit it.

In operation, the net 1 has to be raised and lowered rapidly in order not to delay normal aircraft operations. The drive means 5 for moving each boom comprises a constant speed electric motor 11 with an output shaft connected via a flexible coupling 12 and gearbox 13 to a horizontal drive spindle 14 that extends parallel to the boom axis 4 and carries a crank arm 15 at each end. The end of each crank arm 15 is pivotally connected via a connecting rod 16 to the boom at a point spaced from the boom axis 4 so that the two crank arms and connecting rods form two parallel toggle linkages that move from a substantially straightened state with the boom lowered (see Figure 2) to an extreme folded state with the boom raised (see Figure 1).The velocity ratio provided by these toggle linkages is such that the constant velocity characteristic of the motor 11 is changed to a peaked velocity characteristic in the boom, whereby the boom accelerates away from and decelerates towards both extreme raised and lowered positions. The starting and stopping reactions produced by movement of the boom are therefore reduced.

As indicated in Figure 2, the toggle linkages 15, 16 are arranged so that they operate to move the boom through 85 , the crank arms 15 being rotated through 170 in moving the boom between its extreme- posi- tions. A pair of rubber stops 17 stop the boom in its extreme raised position by cooperation with lugs 18 on the boom adjacent the connections to the connecting rods 16.

The pulley 6 is mounted on an elongate member 19 (Figure 3) which is telescopically received in the upper end of the boom so as to allow longitudinal adjustment of the pulley relative to the boom. The elongate member is a square section tube which is received in a matching square section sleeve 20 in the boom, the two being keyed together by a pin or bolt 21.

The pulley itself is mounted on the elongate member 19 between flanges or cheeks 22 which are curved outwards away from the pulley at their upper edges so as to form a shaped channel to guide the cable 7 into the groove of the pulley. The flanges or cheeks 21 are designed so as to allow only vertical loading from the cable 7 to be transmitted to the pulley, any horizontal loading from the cable being transmitted to the flanges or cheeks and then to the boom.

WHAT WE CLAIM IS:- 1. Aircraft arrester apparatus of the aforesaid type in which each boom is raised and lowered by drive means comprising an actuator which is connected to the boom via a linkage mechanism having a velocity ratio which varies so as to pass through a maximum between the raised and lowered positions of the boom, whereby the angular speed of the boom increases away from and decreases towards these extreme positions and a minimal acceleration reaction and minimal stopping reaction is produced at each.

2. Apparatus as claimed in Claim 1 in which the linkage mechanism comprises a toggle linkage of two pivotally connected links, -one link being pivoted about a fixed axis and the other link being pivotally connected to the boom so that they assume a substantially straightened state relative to one another when the boom is in one extreme position, and assume an extreme folded position relative to one another when the boom is in the other extreme position.

3. Apparatus as claimed in Claim 2 in which the toggle links assume the substantially straightened state when the boom is in the lowered position and assume the extreme folded state when the boom is in the raised position.

4. Apparatus as claimed in Claims 2 or 3 in which said one link is connected to a drive shaft rotatable about said fixed axis.

5. Apparatus as claimed in Claim 4 in which the drive shaft is driven by a constant speed electric motor.

6. Apparatus as claimed in Claim 5 in which the motor is connected to the drive shaft via a gearbox.

7. Apparatus as claimed in any one of Claims 2 to 6 in which the linkage mechanism comprises two toggle linkages connected in parallel.

8. Apparatus as claimed in Claim 7 as dependent on Claim 4 in which the two toggle linkages are each connected to opposite ends of the drive shaft.

9. Apparatus as claimed in any one of the preceding claims in which each boom carries a pulley at its upper end that cooperates with a cable connected to an upper corner of the net, the pulley being mounted on an elongate member that is telescopically received in the end of the boom so as to be longitudinally adjustable relative to the boom.

10. Apparatus as claimed in any one of the preceding claims in which each boom carries a pulley at its upper end that cooperates with a cable connected to an upper corner of the net, the pulley being mounted between a pair of flanges that are curved outwards away from the pulley at their edges so as to form a shaped channel to guide the cable into the groove of the pulley.

II. Aircraft arrester apparatus substantially as herein described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. connected via a flexible coupling 12 and gearbox 13 to a horizontal drive spindle 14 that extends parallel to the boom axis 4 and carries a crank arm 15 at each end. The end of each crank arm 15 is pivotally connected via a connecting rod 16 to the boom at a point spaced from the boom axis 4 so that the two crank arms and connecting rods form two parallel toggle linkages that move from a substantially straightened state with the boom lowered (see Figure 2) to an extreme folded state with the boom raised (see Figure 1).The velocity ratio provided by these toggle linkages is such that the constant velocity characteristic of the motor 11 is changed to a peaked velocity characteristic in the boom, whereby the boom accelerates away from and decelerates towards both extreme raised and lowered positions. The starting and stopping reactions produced by movement of the boom are therefore reduced. As indicated in Figure 2, the toggle linkages 15, 16 are arranged so that they operate to move the boom through 85 , the crank arms 15 being rotated through 170 in moving the boom between its extreme- posi- tions. A pair of rubber stops 17 stop the boom in its extreme raised position by cooperation with lugs 18 on the boom adjacent the connections to the connecting rods 16. The pulley 6 is mounted on an elongate member 19 (Figure 3) which is telescopically received in the upper end of the boom so as to allow longitudinal adjustment of the pulley relative to the boom. The elongate member is a square section tube which is received in a matching square section sleeve 20 in the boom, the two being keyed together by a pin or bolt 21. The pulley itself is mounted on the elongate member 19 between flanges or cheeks 22 which are curved outwards away from the pulley at their upper edges so as to form a shaped channel to guide the cable 7 into the groove of the pulley. The flanges or cheeks 21 are designed so as to allow only vertical loading from the cable 7 to be transmitted to the pulley, any horizontal loading from the cable being transmitted to the flanges or cheeks and then to the boom. WHAT WE CLAIM IS:-

1. Aircraft arrester apparatus of the aforesaid type in which each boom is raised and lowered by drive means comprising an actuator which is connected to the boom via a linkage mechanism having a velocity ratio which varies so as to pass through a maximum between the raised and lowered positions of the boom, whereby the angular speed of the boom increases away from and decreases towards these extreme positions and a minimal acceleration reaction and minimal stopping reaction is produced at each.