US3285575A

US3285575A - Aerial target towing installations

Info

Publication number: US3285575A
Application number: US370805A
Authority: US
Inventors: Frank K Griffiths
Original assignee: Flight Refuelling Ltd
Current assignee: Cobham Mission Systems Wimborne Ltd
Priority date: 1964-05-28
Filing date: 1964-05-28
Publication date: 1966-11-15
Anticipated expiration: 1983-11-15

Description

NOV '15, 1965 F. K. GRIFFITHs 3,285,575

AERIAL TARGET TOWING INSTALLATIONS Filed May 28, 1964 'sneets-sheet 1 Ill ` FRANK KEN New! @hmm-rw s INVENTOR )EAM FAIR TBAINK #msc H ATTORNEY:

NOV 15, 1965 F. K. GRlFFlTl-ls 3,285,575

AERIAL TARGET TO'NING INSTALLATIONS Filed May 28, 1964 3 Sheets-Sheet 2 N f1-H CmPmTH-S FRAN l M WEA/TOR BY 95M.; F'Alrznum v #mscH A TTORNEYS Nov. 15, 1966 F, K, GRIFFITH?, 3,285,575

AERIAL TARGET TOWING INSTALLATIONS Filed May 28, 1964 5 Sheets-snee?l 3 ,Ww/M

L FW- Ls; -WL/ g g Y n 55 W oooo a% 5I] oooc A FRAN r Kuuur 'CRHFH H s /NVENTOR BY .Diani FMRGANK v #unc-rf TTORNEYS United States Patent O 3,285,575 AERIAL TARGET TOWING INSTALLATIONS Frank K. Griffiths, Ferndown, Dorset, England, assigner to Flight Refuelling Limited, London, England, a British company Filed May 2S, 1964, Ser. No. 370,805 Claims. (Cl. 254-172) This invention relates to aerial target towing installations for paying out and reeling in cables by means of which targets are connected to aircraft so that the said targets can be towed for use in connection with the pracice tiring of missiles from other aircraft or from the ground.

It is the object of the invention to provide an improved target towing installation which enables the cable attached to the target to be payed out and reeled in without difficulty and avoids rapid wear of or damage to the cable, thereby substantially reducing the danger of losing the target.

According to the present invention an aerial target towing installation comprises a reel drivable in opposite directions for paying out and winding in a towing cable attached to a target, the towing cable being led over one or more capstans coupled to an air screw or air turbine and to the said reel, the capstan or capstans supporting the tension load applied to the cable -by the drag of the target and the reel being connected to the air screw or air turbine and to the capstan or capstans through a variable speed drive mechanism.

The variable speed drive mechanism may com-prise a V-belt arranged between a pair of pulleys bot-h of which are capable of expansion and contraction to enable the drive ra-tio from one to the other to be varied.

The invention is hereafter described with reference to the accompanying drawings, in which:

FIGURE l is a diagramm-atic sectional side elevation of one form of target towing installation according to the invention, the installation being in the form of a pod for mounting on an aircraft either below the wing or in some other convenient position;

FIGURE 2 is a diagram showing the main elements of the mechanism of the towing installation;

FIGURE 3 is a diagram showing the speed control system for the cable reel; and

FIGURE 4 is a diagram showing the liquid pressure circuit of the speed control system.

Referring to the drawings, -a pod-like housing contains a 4cable reel 11 mounted substantially longitudinally in the housing 10, a serving carriage 12 (FIGURE 2) mounted on an Archimedean yscrew 13 so as to travel toand-fro along the reel and lay the cable evenly thereon, a pair of capstans 14 and 15 (FIGURE 2) over which a towing cable 16 is led to the serving carriage 12 and so to the reel 11, and an airscrew or air turbine 17 for driving both the reel 11 and the capstans 14 and 15.

The airscrew or air turbine 17 includes blades 18 mounted on a shaft 19 driving through bevel gears 21, 22 a transverse shaft 23 on which the capstan 14 is mounted, the other capstan 'being driven at the same speed as the capstan 14 by a chain drive 24 connecting them one to the other. Also mounted on the shaft 23 is an expanding pulley 25 forming the driving member of a V-belt drive, the two sides of the pulley being urged towards each other by springs indicated at 26. Another expanding pulley 27 constituting the driven member of the Vabelt drive, and driven from the pulley 25 through the belt 28 has one side urged towards the other by liquid under pressure acting in a motor cylinder 29. The pulley 27 drives the cable reel 11 through Ibevel gearing 31, and the Archimedean lscrew 13 is driven through spur reduction gea-ring 32 from the reel 11 so as to give a suitable 3,285,575 Patented Nov. 15, 1966 lCC rate of travel of the serving carriage 12 along the screw.

The towing cable 16 is secured at its free end t=o a target 33 (FIGURE l) which, when not being trailed, is supported on a retractable launching support 34, the cable 16 being led over a pulley 35 to its attachment on theA target. The target and its launching support form no part of the present invention and will not be described in detail herein.

The towing cable 16, Ibetween the capstans 14, 15 and the pulley 35, passes over a group of three

pulleys

36, 37, 38 to form a bight 39 in the said cable around the pulley 37. As shown in FIGURE 3, this pulley 37 is mounted on a pivoted arm 41, spring-loaded at 42 so as to apply a light load acting to extend the bight 39, so that increase in tension in the cable will tend to move the arm 41 against the spring 42.

The liquid pressure cylinder 29 is, as shown in FIG- URE 4, connected through a control valve 43 to a liquid pressure accumulator 44 so that, by suitable operation of the Isaid control valve 43, liquid under pressure can be admitted to or allowed to escape from the cylinder 29.

The control valve 43 is of the electrically controlled type, known per se, in which the position of the valve is determined by the relation between two magnetic fields, the valve being closed when the two elds are balanced, opened to admit liquid under pressure to the motor cylinder 29 when there is a difference between the eld strengths in one sense, and opened to allow liquid to escape from the motor cylinder when there is a difference between the field strengths in the opposite sense.

The magnetic lields are generated by coils 45, 46 which are shown diagrammatically in FIGURE 3 as providing ields )acting on a valve-operating member 47. The coil 45 is connected to a reference source of electric current, and the coil 46 is connected through a potentiometer 48 coupled to the arm 41 to the same or another source of current, the arrangement being such that, at a predetermined -setting of the potentiometer the two currents provide balanced magnetic fields.

The pulley 27 and the motor cylinder 29 are so arranged that pressure acting in the cylinder urges the sides of the pulley towards each other which, since it is the `driven pulley, reduces the speed of the reel 11 and screw 13 relative to the capstans 14 and 15, thus tending to reduce tension in the cable 16 between the capstans and the reel. The connection of the arm 41 to the potentiometer 4S is such that the current to the coil 46 is increased when the arm is moved by tension in the cable to shorten the bight 39, and that a greater field due to this coil actuates the valve 43 to admit liquid under pressure to the motor cylinder 29. Thus any increase in cable tension from a predetermined value reduces the speed of the reel to reduce such tension until it returns to the predetermined value, and, correspondingly, a reduction in the tension below the predetermined value increases the speed of the reel to increase the tension and restore it to the predetermined value.

The liquid pressure system, shown in FIGURE 4 includes a pump 49 which draws liquid from a reservoir 51 and delivers it to an olf-loading valve 52 which causes such liquid to pass to the accumulator 44 so long as the pressure in the latter is below a predetermined value, but allows the liquid to return idly to the reservoir 51 when the accumulator 44 is fully loaded. A non-return valve 53 is arranged between the olf-loading valve 52 `and the accumulator, and the latter is connected to the control valve 43 through a reducing valve 54. A filter 55 is arranged between the pump 49 and the off-loading valve 52.

The towing cable 16 is wrapped several times round each of the capstans 14 and 15, and it will be understood that, so long as some tension is applied lto the said cable between the said capstans and the reel 11, the capstans themselves will support the tension in the part of the cable between the said capstans and the target when the latter is being towed. The actual tension between the capstans and the reel will, therefore, have a value which is not affected by variations in the towing load. The tension between the capstans and the reel can therefore be chosen so as to provide smooth winding of the cable on the reel without one layer biting into the next.

If the reel 11 were driven at a constant speed relative to the capstans 14, 15 it is evident that the tension would vary from layer to layer on the reel in view 0f the fact that the layers increase in size as the cable is wound on. 'The

variable speed drive

25, 27, 28 enables the tension to be maintained constant by varying the speed of the reel relative to the speed of the capstans, and the variable speed gear is controlled to provide this relative speed variati-on by the liquid pressure mot-or 29 in response to tension changes sensed by the arm 41 and causing adjustment of the potentiometer 48.

Modiiications may be made in the installation according to the invention. For example, only one capstan may be used instead of two, though a single capstan has the disadvantage that the cable must slide laterally across `the capstan as it is wound `on and 01T. Forms of variable speed gear other than the V-belt described may be used to vary the speed of the reel relative to the speed of the capstans, a suitable alternative arrangement being a hydraulic pump and motor with means for varying their relative' speeds.

The paying out or lreeling in of the cable may be controlled by varying the pitch of the blades of the airscrew or 4air turbine, the latter providing power to draw the cable in and serving as a brake to retard lthe movement of the cable as it is payed out. The pitch-varying mechanism may be controlled automatically by means sensitive to the direction of movement of the cable to set the said blades to a driving position for reeling the cable in and to a braking position for paying the cable out, the motive power during paying out being derived from the drag of the target itself.

I claim:

1. An aerial target towing installation comprising a reel drivable in opposite directions for paying out and winding in a towing cable attached to a target, at least one capstan around which said towing cable is wound, an air driven member operatively connected to said capstan and said reel to drive the latter, said capstan supporting the tension load applied to the lcable by the drag of the target, a variable speed drive mechanism connected between said reel and said air driven member and said capstan, said variable speed drive mechanism comprising a V-belt arranged between a pair of expandable and contractable pulleys to enable the drive ratio from one to the other to be varied and means responsive to changes in the tension of the towing cable at a point between the capstan and the reel to vary the drive ratio of said variable speed mechanism.

2. An aerial target towing installation according to claim 1 in which a liquid pressure motor is provided operatively connected to one lof the pulleys of said variable speed drive mechanism to vary the spacing between the sides of said pulley to change the drive ratio thereof, and a valve responsive to changes in the tension of the towing cable at a point between the capstan and the reel to control the flow of fluid under pressure to said pressure motor.

3. An aerial target towing installation according to claim 2, wherein the valve includes a control member acted upon by two opposed magnetic fields one of which is a reference eld and the other of which is varied by changes in an electric current inducing it, and a potentiometer responsive to the changes of cable tension to vary the current through the other magnetic field.

4. An aerial target towing installation according to claim 3 wherein two spaced pulleys are provided at a point between the capstan and the reel, la third pulley is provided between said `two pulleys and spaced therefrom, said towing cable being led over said two pulleys to form between them a bight around said third pulley, the third pulley being mounted on a pivoted arm which is spring loaded in a direction to apply tension to the cable.

5. An aerial target towing installation according to claim 4, wherein the potentiometer is operated by movement of the arm carrying the third pulley.

References Cited by the Examiner UNITED STATES PATENTS 2,892,599 6/1959 Baldwin 244-3 2,916,927 12/1959 Opper 72-230.l7 3,016,754 1/1962 Corey 74-230.17

FOREIGN PATENTS 274,515 9/1927 Great Britain.

EVON C.`BLUNK, Primary Examiner. H. C. HORNSBY, Assistant Examiner.

Claims

1. AN AERIAL TARGET TOWING INSTALLATION COMPRISING A REEL DRIVABLE IN OPPOSITE DIRECTIONS FOR PAYING OUT AND WINDING IN A TOWING CABLE ATTACHED TO A TARGET, AT LEAST ONE CAPSTAN AROUND WHICH SAID TOWING CABLE IS WOUND, AN AIR DRIVEN MEMBER OPERATIVELY CONNECTED TO SAID CAPSTAN AND SAID REEL TO DRIVE THE LATTER, SAID CAPSTAN SUPPORTING THE TENSION LOAD APPLIED TO THE ABLE BY THE DRAG OF THE TARGET, A VARIABLE SPEED DRIVE MECHANISM CONNECTED BETWEEN SAID REEL AND SAID AIR DRIVEN MEMBER AND SAID CAPSTAN, SAID VARIABLE SPEED DRIVE MECHAMISM COMPRISING A V-BELT ARRANGED BETWEEN A PAIR OF EXPANDABLE AND CONTRACTABLE PULLEYS TO ENABLE THE DRIVE RATIO FROM ONE TO THE OTHER TO BE VARIED AND MEANS RESPONSIVE TO CHANGES IN THE TENSION OF THE TOWING CABLE AT A POINT BETWEEN THE CAPSTAN AND THE REEL TO VARY THE DRIVE RATIO OF SAID VARIABLE SPEED MECHANISM.