Title:
HIGH LEVEL WASHING AND DUSTING APPARATUS FOR AIRCRAFT AND THE LIKE
United States Patent 3775798


Abstract:
A washing and dusting unit particularly for cleaning the upper surfaces of larger aircraft. A powered brush is connected to the distal end of a powered boom structure which has three elements connected pivotally in seriatim. The first element is adjustably coupled to a support and the elements can be adjusted into a generally inverted-U configuration to bring the brush onto the upper surfaces of the aircraft. The brush is connected to a telescopic member which is in turn connected to an adjustable arm coupled to the boom structure. A seat is provided adjacent the adjustable arm and the orientation of both arm and seat is maintained by a levelling mechanism coupled to the boom structure. The adjustable arm has shoulder, upper arm, elbow and wrist adjustments to position the brush as desired.



Inventors:
THORNTON TRUMP W
Application Number:
05/133534
Publication Date:
12/04/1973
Filing Date:
04/13/1971
Assignee:
THORNTON TRUMP W,US
Primary Class:
Other Classes:
212/238, 212/299
International Classes:
B64F5/00; (IPC1-7): B64F5/00
Field of Search:
15/21R,21E,5R,5C,49R,49C,97R,98 239
View Patent Images:
US Patent References:
3557967ARTICULATED CRANE1971-01-26Madole
3551934AIRCRAFT SKIN CLEANING MAINTENANCE1971-01-05Franzreb
3460177AIRCRAFT WASHING SYSTEM1969-08-12Rhinehart et al.
3439372AIRPLANE WASHING DEVICE1969-04-22Collier
3196472Mobile washing apparatus for automobiles and the like1965-07-27Ventrella
3099852Power operated brush attachment for earth moving machine1963-08-06Grant



Primary Examiner:
Roberts, Edward L.
Claims:
I claim

1. Washing and dusting apparatus comprising:

2. Apparatus according to claim 1 wherein levelling means extend from said coupling means to said support means for maintaining the orientation of said coupling means constant with respect to the vertical during movement of said first, second, and third elements.

3. Apparatus according to claim 2 wherein a seat for an operator is connected to said levelling means adjacent said coupling means whereby the orientation of said seat is maintained constant during movement of said boom structure.

4. Apparatus according to claim 1 wherein said coupling means includes a telescopic member for permitting reciprocal movement of said brush means with respect to said third beam; a telescopic actuator being connected to said telescopic member and being operable to cause reciprocal movement of said brush means.

5. Apparatus according to claim 2 wherein said coupling means has a longitudinal axis, said coupling means being pivotally mounted with respect to said levelling means for swinging movement about a shoulder axis; shoulder actuator means interconnecting said coupling means and said levelling means for causing swinging movement therebetween.

6. Apparatus according to claim 5 wherein said coupling means includes an elbow joint intermediate its opposite ends; said elbow joint permitting articulated folding movement of said coupling means about an elbow axis which is transverse to said shoulder axis; an elbow actuator being connected to said elbow joint for causing articulated folding about said elbow axis.

7. Apparatus according to claim 6 wherein said coupling means includes a wrist joint intermediate its opposite ends, said wrist joint permitting two portions of said coupling means to rotate with respect to one another about a wrist axis which is parallel to said longitudinal axis of said coupling means; a wrist actuator being connected to said wrist joint for causing rotational movement of said two portions about said wrist axis.

8. Apparatus according to claim 7 wherein said wrist joint is on one side of said elbow joint and an upper arm joint is on the other side of said elbow joint; said upper arm joint permitting the portions of said coupling means on opposite sides of said upper arm joint to rotate about an upper arm axis parallel to the longitudinal axis of said coupling means; an upper arm actuator being connected to said upper arm joint for controlling rotation about said upper arm axis.

9. Apparatus according to claim 8 wherein said coupling means has first and second ends, said shoulder joint being adjacent said first end and said elbow joint being spaced from said shoulder joint; said upper arm joint being between said shoulder and elbow joints.

10. Apparatus according to claim 9 wherein said coupling means includes a telescopic member for permitting reciprocal movement of said brush means along an axis parallel to said longitudinal axis of said coupling means; a telescopic actuator connected to said telescopic member and being operable to cause reciprocal movement of said brush means.

11. Apparatus according to claim 10 wherein said telescopic member is positioned adjacent said second end of said coupling means and said upper arm joint, said elbow joint and said wrist joint are between said telescopic member and said shoulder joint.

12. Apparatus according to claim 1 wherein said second actuator means includes a mechanism pivotally interconnecting said first and second elements, a power means interconnecting said second element and said mechanism and being operable to cause said second element to swing with respect to said first element.

13. Apparatus according to claim 12 wherein said first element includes a cranked portion adjacent the pivotal connection between said first and second elements so that with said first element in a horizontal position said second element is free to fold to a position resting horizontally above said first element.

14. Apparatus of the type described comprising:

15. Apparatus according to claim 14 wherein said arm includes a wrist joint intermediate its opposite ends, said wrist joint permitting the portions of said arm on opposite sides of said wrist joint to rotate about a wrist axis parallel to said longitudinal axis of said arm; a wrist actuator being connected to said wrist joint for controlling rotation about said wrist axis.

16. Apparatus according to claim 15 wherein said wrist joint is on one side of said elbow joint and an upper arm joint is on the other side of said elbow joint; said upper arm joint permitting the portions of said arm on opposite sides of said upper arm joint to rotate about an upper arm axis parallel to said longitudinal axis of said arm; an upper arm actuator being connected to said upper arm joint for controlling rotation about said upper arm axis.

17. Apparatus according to claim 16 wherein said coupling means includes a telescopic member interconnecting said arm and said work tool for permitting reciprocating movement of said work tool with respect to said arm, a telescopic actuator being connected to said telescopic member for causing reciprocating movement of said work tool.

18. Apparatus of the type described comprising:

Description:
This invention relates to washing and dusting apparatus, and more particularly, it relates to washing and dusting apparatus suitable for use on the upper surfaces of aircraft.

Washing aircraft has presented serious problems which have been overcome in part by the use of aerial brush devices. These devices however have been found unsatisfactory in many instances because they are complicated and relatively expensive. As aircraft are made larger the problems are increased, particularly the problem of washing the upper surfaces of the wings and the tail section.

Accordingly, the present invention in one of its aspects provides a powered brush attached to the distal end of a boom structure which is pivotally mounted on a support. The boom structure comprises first, second and third elements pivotally connected in seriatim, so that the elements can be adjusted into a generally inverted -U configuration to bring the brush onto the upper surfaces of an aircraft. The brush can then be moved across the surface by manipulating the elements.

In another of its aspects the invention provides coupling means for attaching the brush to the distal end of the boom structure. The coupling means includes shoulder, upper arm, elbow and wrist adjustments as well as a telescopic adjustment for moving the brush through a large variety of angular positions relative to the boom structure. In a preferred form, an operator's seat is also coupled to the distal end of the boom structure and held in a predetermined orientation by a levelling mechanism which is coupled to the boom support.

In yet another of its aspects, the first element has a cranked portion where it is pivotally connected to the second element and an actuator is coupled to the second element. The actuator operates through links to adjust the angle between the first and second elements. This arrangement of the actuator allows a lighter second element to be used and also results in reduced actuator forces as compared with the forces required in an actuator coupled directly to the first element.

Further objects and advantages of the invention will appear from the following description taken together with the accompanying drawings, in which:

FIG. 1 is a side view of a preferred embodiment of the invention mounted on a conventional truck chassis;

FIG. 2 is a view looking down on the invention;

FIG. 3 is a sectional view on line 3--3 of FIG. 2;

FIG. 4 is a top view of the device shown in FIG. 3;

FIG. 5 is a diagrammatic view of the invention shown in a number of different positions; and

FIG. 6 is a diagrammatic view of another embodiment of the invention.

Reference is first made to FIGS. 1 and 2 with particular reference to FIG. 1. A truck 10 is equipped with a turntable 12 which pivotally supports an elongated boom structure 13 having a first element 14, a second element 16, and a third element 18. The elements 14, 16 and 18 are of fabricated construction and are pivotally connected in seriatim. Pairs of first, second, and third actuators, 20, 22 and 24 which are coupled to the elements for changing the relative positions of the elements are controlled from either a first set of controls 25 in an operator's chair 26 or from a second set of controls 27 on the turntable 12. The chair 26 is pivotally attached to the distal end of the third element 18 and is maintained in a horizontal position by a pair of levelling mechanisms 19 positioned one on each side of the boom structure 13. A pair of generally cylindrical washing and dusting brushes 28 are rotatably coupled one to each side of a coupling 30 which includes a telescopic member 32 and an adjustable arm 34. The arm 34 has shoulder, upper arm, elbow and wrist adjustments as will be described and combines with the telescopic member 32 for changing the orientation of the brushes 28 relative to the chair 26.

In the folded position shown in FIG. 1, the first element 14 of the boom structure 13 rests horizontally on a front support 36 which is rigidly attached to the truck, and the third element 18 rests on a similar rear support 38. The truck is stabilized during use of the boom structure by conventional outriggers 40, 42, which are duplicated on the hidden side of the truck. The outriggers and actuators 20, 22, 24 are preferably operated hydraulically.

The turntable 12 is of conventional design and includes a lower fixed portion 44 and an upper portion 46 which can be rotated relative to the lower portion 44 and locked in any desired position. A pivot 48 which lies transversely of the boom structure 13 couples the upper portion 46 of the turntable 12 to one end of the first element 14. The element 14 is of fabricated construction and terminates at its opposite end in a cranked or dog-leg portion 50. A second transverse pivot 52 which is generally parallel to the pivot 48 couples the portion 50 to the second element such that the pivot 52 lies substantially above the longitudinal axis of the first element 14 to allow the second element 16 to come to rest in the position shown in FIG. 1. The element 14 can be moved up and down by energizing actuators 20, each of which is pivotally connected at 54 to a bracket 56 on the upper portion 46 of the turntable 12 and at 58 to a bracket 60 on the lower side of the element 14 respectively.

The position of the second element 16 relative to the first element 14 can be adjusted by the actuators 22, each of which is coupled between a point intermediate the ends of a moment arm or link 62 and a bracket 64 on the element 16. A first end of the moment arm 62 is coupled to a bracket 65 on the second element 16 at a pivot 66 and an opposite end is coupled to an end of a link 67 at a pivot 68. The opposite end of the link 67 is pivotally connected at 69 to a bracket 70 on the first element 14. When the actuators 22 are activated they force the moment arms 62 to rotate about the pivots 66 and the links 67 to rotate about the pivots 68, 69 resulting in the element 16 rotating about the pivot 52. The moment arms 62, links 67 and actuators 22 are chosen so that the element 16 can rotate through approximately 160 degrees about the pivot 52 as will be described.

The distal end of the second element 16 is coupled by a pivot 71 to an end of the third element 18. The actuators 24, each of which is rotatably attached to a bracket 72 on the third element 18, are pivotally coupled at their opposite ends to links 73, 74 at common pivot points 75. Each link 73 is also coupled at an opposite end to a bracket 76 on the third element 18, and the opposite end of link 74 is coupled to a bracket 77 on the second element 16. The operation of the actuators 24 is similar to that of actuators 22. However, the actuators 24, links 73 and 74 are chosen so that the third element 18 can pivot about the pivot 71 to either side of the axis of the second element 16 within a range limited by the movement of the actuators 24. This movement is possible because levelling mechanism 19 includes a chain and sprocket levelling mechanisms 78 on the third element 18.

Each levelling mechanism 19 consists of a levelling rod 79 pivotally coupled at one end to a pivot 80 on the turntable 12 and at its opposite end to a pivot 81 on a bell-crank lever 82 which is rotatably coupled to the pivot 52 between the elements 14 and 16. The opposite end of the bell-crank lever 82 is connected by a pivot 83 to an end of a levelling rod 84 which is coupled at its opposite end to a pivot 85 at the distal end of a crank 86. The crank 86 is fixed to the pivot 71 which is rotatably coupled to the elements 16, 18 and which is also fixed to a chainwheel 88 at one end of the pivot 71. The chainwheel 88 forms a part of one of the sprocket and chain assemblies 78 each of which also includes a chain 90 coupled at its ends to the ends of tie-rods 92, 94. A chain 96 is attached to the opposite ends of rods 92, 94 and passes around a sprocket 98 fixed to a layshaft 100 which is journalled in a bracket 101 on the element 18. A second sprocket (not shown) is attached to the layshaft 100 and is coupled by chains 102, 104 and tie-rods 106, 108 to a sprocket 110 on a shaft 112. The shaft 112 is rotatably journalled in the element 18 and is fixed by its end to the seat 26.

The pivots 48 and 80 on the turntable 12, and 52 and 81 at the distal end of the element 14 form a parallelogram so that as the first element 14 is elevated by the actuators 20, the bell-crank levers 82 remain in the same angular position relative to the horizontal. Also the pivots 52, 83 at the bell-cranks and 71, 85 at the distal end of the element 16 form a second parallelogram to maintain the position of the crank 86 and chainwheels 88 relative to the bell-cranks 82 and hence relative to the pivots 48, 80 on the turntable so that the cranks 86 remain in the same position relative to the horizontal no matter what the position of the elements 14 and 16. Also because each sprocket 88 is linked to the corresponding sprocket 110 at the distal end of the element 18, the parallelograms and chain and sprocket linkages maintain the chair 26 in a horizontal position.

Some two-element machines have used a second element controlled by an actuator such as 22, which was coupled directly to the first element 14. The second element 16 was straight, and the first element had a cranked end portion such as 50. It has been found that coupling the cylinder to the second or upper of the two elements and arranging the moment arm 62 and link 67 as shown in FIG. 1 results in an improved actuator efficiency as well as allowing a lighter second element to be used. The pivot 52 is offset from the longitudinal axis of the first element 14 to facilitate folding the elements to bring the second element 16 against the first element 14 in a horizontal position. The force applied by the actuator 22 is directed along a path which gives a larger turning moment about the pivot point 52 than is the case with the actuator attached to the first element 14. Also the actuator 22 is connected to substantially the mid-point of the elment 16 so that the force from the actuator 22 is applied to element 16 nearer to the load than is the case when the actuator is attached to the first element 14. Consequently the element 16 can be lighter and carry the same load with corresponding reduction in inertia forces when the element 16 is moved.

A further advantage resulting from placing the actuator on the element 16 as opposed to the element 14 is that the element 14 can be more readily insulated electrically. This is a desirable feature if the machine is to be used for purposes where one of the second and third elements is to be moved near to electrical conductors such as overhead hydro cables.

Reference is next made to FIG. 3 and 4 with particular reference to FIG. 3 to describe the coupling 30. The shaft 112 on which the seat 26 is mounted, acts as a pivot for the arm 34 which is positioned on shaft 112 by an actuator 114 which is preferably a hydraulic cylinder and piston arrangement. Movements of the arm 34 about its longitudinal axis are controlled by an upper arm motor 116, elbow motor 118, and wrist motor 120. The motors 116, 120 which are preferably hydraulically operated, control angular movement about the longitudinal axis of the arm 34 through worm and wheel gear boxes 122, 124, respectively, and the elbow motor 118 which is also preferably hydraulically operated controls movement about a transverse axis through an elbow worm and wheel gear box 126. The outer end of the arm 34 is coupled to the telescopic member 32 which includes an actuator 128 for adjusting the position of washing and dusting brushes 28. The actuator is preferably similar to the actuators 20, 22, 24 and 114. A fourth motor 132 (also preferably hydraulic) drives the brushes 28 through a right-angle bevel gear-box 134.

The actuator 114 is coupled at its rear end to the rear of an elongated bracket 136 which is fixed by bolts 137 to the shaft 112 so that the bracket 136 is maintained substantially horizontal together with the seat 26. The forward end of the actuator 114 is coupled to a moment arm 138 fixed to a forked member 140. Each of the arms of the forked member 140 is pivotally mounted on the shaft 112 so that the arm 34 can rotate about the shaft 112 under influence of the actuator 114 on the moment arm 138. The shape and length of the moment arm 138 and the choice of actuator 114 dictate the limits of angular movement of the arm 34 about the shaft 112. Large angular movements are not normally necessary because the motors 116, 118 and 120 allow a great range of movement of the brushes 28 as will be described.

The forked member 140 has a radial flange 142 intermediate its ends for attaching the member 140 by bolts 144 to the gear box 122. A worm gear (not shown) is coupled to the motor 116 and engages a worm wheel 146 for rotating the part of the arm 34 outwardly of the motor 116 about its longitudinal axis. Forked member 140 also includes a series of stepped cylindrical portions towards its outer end for mounting conventionally an inner roller race 148 and an outer roller race 150. The outer race 150 is adjusted by tightening a plate 152 against the race 150 using bolts 154 and both races 148, 150 are seated in a housing 156 to which is attached at its inner end the worm wheel 146 by bolts 158. The worm wheel 146 also locates the inner race 148 in the housing 156. Oil is sealed in the gear box by a pair of conventional lip seals or the like 160, 162. The seal 160 is located in the casing of the gear box 122 and adapted to bear on the housing 156, and the seal 162 is located in the cover plate 152 such that the seal 162 rides on the inner surface of the housing 156. The outer end of the housing 156 is attached to first and second clevis plates 164, 166 which are welded to the housing 156 and strengthened by welded ribs 168. The motor 118 is attached to the clevis plates 164, 166 by bolts 170 and an axle 172 having a flange 174 is attached to the first clevis plate 164 by bolts 176. The axle 172 passes through second clevis plate 166 and is held in place by a retaining plate 178 which is attached to the axle 172 by bolts 180.

When the motor 118 is activated, a worm 181 which is coupled to the motor 118 causes a worm wheel 182 to rotate. The wheel 182 is similar to the wheel 116 and is located between third and fourth clevis plates 184, 186 by spacers 188, 190 held in place by bolts 192. A journal bearing 194 passes through the third and fourth clevis plates 184, 186 and through the spacer 188 so that when the motor 118 is activated the wheel 182 is rotated about the axle 172 carrying with it the third and fourth clevis plates 184, 186. This allows the portion of the arm 34 outward of the axle 172 to swing about the axle 172 which lies transversely of the arm 34.

Third and fourth clevis plates 184, 186 are attached to a flange 196 and a strengthening web 198. The flange 196 corresponds to the flange 142 associated with the gear box 122 and the parts forming the gear box 124 are similar to the parts of the gear box 122. A housing 200 corresponding in general shape to the housing 156 extends outwardly from the gear box 124 and is attached at its outer end to a support member 202 which is attached to the housing 200 by bolts 204. The support member 202 terminates at its outer end in a clevis through which a clevis pin 206 passes. The clevis pin 206 also passes through an extension 208 on the member 32, and a similar smaller extension 210 is connected by a clevis pin 212 to a clevis 214 attached to the housing 200. The arrangement of the clevis pins 206, and 212 allows easy removal of the telescopic member 32 and if desired, a platform or the like can be connected to the arm 34 in place of the telescopic member 32.

The arrangement of motors 116, 118, 120 and gear boxes 122, 124 and 126 and actuator 114 allows the arm 34 to reproduce some of the movements of a human arm. The actuator 114 elevates the arm 34 at the shoulder while the motors 116, 120 rotate the arm at the upper arm and wrist respectively. Elbow movement is achieved by the motor 118 and gear box 126. Consequently the arm 34 may be adjusted to take up a large number of positions by manipulating controls at either of the control panels 25 or 27 (FIG. 1).

A further measure of adjustment is provided by the telescopic member 32 which includes elongated tubular outer and inner members 216, 218 respectively. The inner member 218 is slidably engaged in the outer member 216 and a key 220 attached to the outer member 216 is slidably engaged in a key-way 221 in the inner member 218 to prevent rotation of the inner member relative to the outer member. Inner member 218 can be moved outwardly and returned by energizing actuator 128 which is coupled to support plates 222, 223 fixed to the outer end of the inner member 218 and the inner end of the outer member 216 respectively. The actuator 128 is free to move the inner member 218 outwardly between an extended position where the stop 224 engages the key 220 to prevent further outward movement, and a retracted position where the support plate 222 engages the outer end of the outer member 216.

The outer support plate 222 is rigidly coupled to the bevel gear-box 134 by a pair of parallel plates 226 such that the axis of an output shaft 228 is at right angles to the longitudinal axis of the telescopic member 32. The motor 132 drives a bevel pinion 230 which is in mesh with a bevelled wheel 231 on the output shaft 228. The shaft 228 is journalled conventionally in taper roller bearings 232, 233 and sealed with conventional oil seals 234, 236. When the motor 132 is activated the output shaft 228 is rotated carrying with it washing brushes 28 which are slidably engaged one on each spline 242, 244 of the shaft 228. The brushes 28 are secured on the shaft 228 by locking nuts 246, 248.

Reference is again made to FIG. 1 to further describe the levelling mechanisms 19, each of which includes the levelling rods 79, 84 which form parts of parallelograms as previously described. Because a parallelogram formed from four links is unstable when the links lie on a common line, it is essential to ensure that the first element 14 is not allowed to move into a position where the levelling rod 79 lies on a continuation of a line drawn between the pivots 48, 80. It is commonly accepted that a safe limit for the position of the rod 79 is 10° to the line between pivots. Consequently the range of element 14 is 160° relative to the pivot 48 and the minimum angle between the rod 79 and the line between pivots 48, 80 is 10°.

The second parallelogram containing the rod 84 will next be considered. A line drawn between pivots 52, 83 remains in the same position relative to the horizontal due to the levelling effect of the rod 79 on the bell-crank 82. As before, the range of movement of the element 16 is about 160° unless the element 16 engages the element 14 in which case the movement is reduced. For instance, in the position drawn the element 16 is free to rotate about the pivot 52 into an upper position where element 16 lies at 10 degrees to a line drawn through pivots 52 and 83. Thus with the element 14 horizontal, the range of element 16 is between this upper position and horizontal. As the element 14 is elevated it gradually moves out of the possible range of element 16 until, when the element 14 is almost vertical, the element 16 is free to move through a range of about 160° (if a safe limit of 10° is used).

The angular position of the pivot 83 about the pivot 52 locates the range of movement of the element 16. If the pivot 83 is moved clockwise, about pivot 52 then the 160 degree range is also moved clockwise, and similarly for anticlockwise movements. However anticlockwise movement is limited by possible interference of elements 14 and 16 within the range of element 16. Also clockwise movement is limited by the necessary 10° angle between the levelling rod 30 and the line through pivots 52, 83 with the elements 14, 16 in the FIG. 1 position. Once the range has been decided and the pivots located accordingly, the actuators 22, moment arms 62 and links 67 are chosen so that the actuators 22 can not move the element 16 outside this range.

In the present invention the element 16 will not normally be required to move into a vertical position so that the range of element 16 is located to give approximately 80° to either side of the horizontal.

The sprocket and chain assembly 78 has the advantage over the levelling rods that it allows the third element 18 to move through relatively large angles because there is no unstable position corresponding to that of the levelling rods. Consequently the range of element 18 is limited only by the movement of actuator 24, and of course by the maximum safe range of the brush about the truck. Typically the range is about 210°. One end of the range occurs with the second element vertical and the actuator fully retracted so that the second and third elements define an angle of about 20°.

Reference is next made to FIGS. 3 and 5 with particular reference to FIG. 5 which shows some of the many positions in which it is possible to place the brush when washing an aircraft. In the position A the wrist motor 120 has turned the brush through 90° relative to the FIG. 3 position for washing the upper portion of a plane's tail section Next in the position B the arm 34 is elevated from the A position by the piston 114. In the position C the arm 34 has been changed from the FIG. 3 position by activating the elbow motor 118 to rotate the outer part of the arm through 90° about the axle 172 and in the D position the arm is in the same position as shown in FIG. 3. Next the E position is achieved by activating the upper arm motor 116 to rotate the arm 34 through 90° to bring the axis of the axle 172 into a horizontal plane. The motor 118 is then activated to move the elbow joint through 90° to bring the outer part of the arm 34 into a vertical position. Finally the F position is similar to the D position but illustrates the arrangement of the elements for covering a large generally horizontal surface. The brushes can be moved forwardly from the F position by adjusting the elements 16 and 18 simultaneously in a modified pendulum action to produce a generally flat brush path for cleaning large areas. A more nearly flat path can be produced by adjusting either all three elements simultaneously or by adjusting the third and second elements together with the shoulder cylinder 114.

It will be seen from the positions of the brushes 28 that the boom structure 13 is capable of taking up a generally inverted-U shape to wash the upper surfaces of the wings and fuselage and can be further adjusted for washing the surfaces of the tail. Also although the apparatus is not primarily designed to wash the underside of the aircraft, portions of the underside may be washed by positioning the boom structure with its elements generally as shown in FIG. 1 and elevating the brush using the actuator 114 which brings the brush above the level of the seat 26 to avoid interference between the seat and the aircraft. However, the range of positions into which the boom structure can be adjusted will depend upon the relative positions of the pivots 48, 80 and 52, 83 as described, and also upon the relative lengths of the elements 14, 16 and 18. It has been found that for larger aircraft a suitable boom structure has a first element of about 22 feet, second element of about 18 feet and third element of about 20 feet.

The actuators 20, 22, 24, 114 and 128 are preferably double-acting hydraulic piston and cylinder arrangements which are controlled by adjustable valves. Oil is pumped to the valves which control the flow to a combination of actuators corresponding to a desired brush movement. The necessary oil pipes are not shown on the drawings for simplicity, but the pipes may be led inside the boom structure to protect them or along the outside of the boom structure as desired.

Reference is next made to FIG. 6 which illustrates a second embodiment of the invention, and in particular of the boom structure. The FIG. 1 arrangement of the second and third elements is essential to the satisfactory functioning of the apparatus over wings and other generally horizontal surfaces because this arrangement allows a pendulum action over the wings as previously described. The second embodiment has second and third elements which are substantially the same as elements 16, 18 (FIG. 1). However the FIG. 1 first element is replaced in the second embodiment by an elevator 249 having a platform 250 which is supported by two pairs of parallel legs 252, 254. The legs are pivotally attached to a turntable 256 on a truck 258.

The elevator 249 is raised and lowered by means of a pair of actuators 260 connected between the legs 252 and the platform 250. As the elevator is raised and lowered the platform 250 always remains in the same horizontal orientation. This allows the positions of the second and third elements relative to the horizontal to remain unchanged as the elevator is adjusted by activating an actuator 260 (preferably hydraulic). This is in contrast to the FIG. 1 arrangement of elements which moves as a unit about the pivot point 48 when the element 14 is adjusted. Thus for some applications it may be advantageous to chose one of the embodiments in preference to the other embodiment.

In both the FIG. 1 and FIG. 6 embodiments water is stored in a tank such as 262 (FIG. 1) where it is mixed with detergent for washing or with a de-icing compound if the apparatus is to be used for de-icing an aircraft. The tank 262 is connected to convention spray jets by hoses (not shown) for spraying the liquid on to the aircraft.