LIFTING SYSTEM COMPRISING A LIFTING APPLIANCE AND A WORK
PLATFORM HAVING A VARIABLE OPENING
The invention refers to a lifting system to be used for work on elongated work pieces, especially to be used at the inspection, the maintenance and the repair of aircraft engines. In accordance with the preamble of claim 1, the system comprises a work platform having a central opening, and on which the mechanics are situated, when working on the elongated work piece. The work piece is placed on a lifting appliance comprised in the system and having a support surface, which is movable in relation to the platform, and by means of which the work piece may be displaced through the central opening of the platform and be lifted up to a suitable level in relation to the platform.
STATE OF THE ART
At the repair or the maintenance of big aircraft engines, having a weight up to some tons, and a length of up to several meters, the engine is removed from the fuselage and transported to a service plant. In many nowadays existing plants the engines then are blocked up on big carriages with their longitudinal axis positioned in a substantially horizontal plane some meters above the ground, so that the engines can be reached from all directions.
The available working space will then be very limited in certain areas, which amongst other things results in ergonomically defective working positions for the mechanics. The restricted space also results in the need of using specially designed chairs in order to make the work reasonably tolerable, so that it can be carried out with a sufficient degree of precision. When performing work on the top parts of the engine, some types of stands are required, so that also the top parts can be reached. Also in this case the ergonomics will be impaired. A further serious drawback of this technique is that the inspection of the most inaccessible areas of the engine is obstructed.
The FR-A-1 2 523 547 discloses another kind of service plant which operates according to a quite different principle than the above solution. For in this case the elongated work piece is placed in an upright position on a pontoon floating in a shaft filled with water. The water level may be controlled by supplying or discharging water to or from the shaft by means of a pumping system, the pontoon then being displaced in correspondence to the change of the water level. This known plant further includes a work platform, having a central opening aligned with the shaft. The distance between the shaft and the work platform and the depth of the shaft are conformed to each other, so that the work piece, which may be an aircraft engine or a rocket engine, may be disposed in suitable, continuously adjustable working positions in relation to the work platform.
From the stationary work platform the mechanics may inspect and work on the work piece from all directions, which always may be brought to a correct working level. Thus, the risk of certain areas being neglected during the inspection is reduced in comparison with the method described in the foregoing pargraph in combination with an simultaneous improvement of the ergonomic conditions.
Notwithstanding these significant improvements the above system still suffers from same serious drawbacks. In the first place this prior system is relatively slow as regards the vertical displacement of the pontoon, since relatively large amounts of water has to be supplied to or discharged from the shaft by means of the pumping system. Furthermore, the floating pontoon has to be secured against tilting movements on every adjustment level in order to assure that the object remains immovable (the pontoon must of course have a certain range of radial movement during the vertical displacement). These measures are rather complicated and thus a shift of the level of the work piece can not be carried out in a simple and easy way.
A further important drawback of this prior device, especially when dealing with elongated pieces having many various diameters, as for example is the case for jet engines, is related to the fact, that the opening of the stationary platform must be seized to the largest diameter of the piece.
This fact implies two essential inconveniences. In the first hand the mechanic will have his feet positioned on the platform at a too far distance from the object, when working on small diameters of the object. Thus, the mechanic will have an erroneous, straining and leaning working position in relation to the object, and the components in the area in question will be difficult to reach. In the second hand, the prior art construction results in there always being a gap between the work piece and the work platform, except when the portion having the largest diameter of the work piece is located in the opening of the platform. Then, it easily might occur that the mechanic by accident lands one of his feet in the gap, since all his attention is directed onto the working area. Furthermore, tools might easily fall down through the gap resulting in possible complications as a consequence.
THE OBJECT OF THE INVENTION
The object of the invention is to provide a device of the kind defined in the preamble of claim 1, having a vertically displaceable lifting surface in relation to a work platform, by means of which the drawbacks of prior art for the inspection and the maintenance of elongated objects, such as jet engines for aircrafts are eliminated, and which provides for a faster, safer and more ergonomic operation than have been possible up to now.
This object is attained at, in that the device as defined in the preamble of claim 1 includes the features of the characterizing part of claim 1.
DESCRIPTION OF A PREFERRED EMBODIMENT
A preferred embodiment of the invention will now be explained more in detail, with reference to the annexed drawings, wherein:
Fig. 1 is a side elevational view of a lifting system in accordance with the invention,
Fig. 2 is a partial top view of a work platform, included in the system of Fig. 1, some parts being removed for the sake of clarity, and
Fig. 3 is a cross-sectional view of one half of the platform shown in Fig. 2.
The system in accordance with the invention comprises two main elements, a lifting appliance and a work platform 50, respectively. The lifting appliance 10 is located in a shaft 1, which extends up to the work platform 50 and has a sufficient depth for allowing the vertical movements of the lifting appliance 11. The top part of the lifting appliance 10 is a lifting platform 11, on which an upright elongated work piece 2, in this case a jet engine, is placed. The radial extension of the lifting platform 11 is slightly smaller than the upper opening of the shaft, so that said lifting platform 11 can move therethrough. A lifting mast 12 is at its upper portion supportingly connected to the lower portion of the lifting platform 11 and guided in a frame 13 by means of guide rollers (not shown) in the shaft 1.
On the frame 13 drive means 14 in the form of one or more motor(s) is provided, which through a toothed transmission gear drives a gear wheel drivingly engaged with a rack 15, which is fixedly secured to the mast 12, so that the mast 12, in the form of a frame work, will move upwardly or downwardly upon energizing of the motor(s). The shaft 1 comprises a portion 16 below the frame 13 permitting the mast 12 to reach its lowermost position, the lifting platform 11 then being positioned just above the uppermost portion of the frame 13. The frame 13 and the mast 12 are of course provided with necessary guides, so that the mast 12 will be able to move as intended. Furthermore, limit switches are provided, to stop the power supply to the motor(s) 14, when the mast 12 reaches its limit positions.
Owing to the fact that the motor(s) is fixedly positioned on the frame, a complicated wiring to the motor(s) advantageously may be eliminated, in contrast to conventional lifting appliances, wherein the motor(s) normally is disposed on the movable part.
With reference to Fig. 2, the work platform 50 consists of two main parts, a fixed, outer, upper and annular work platform part 51, of which only a small portion is shown, but the work platform part 51 continues all around the periphery.
This outer platform part 51 is positioned above a movable platform part 52, which it partly covers, see Fig. 3, and rests at its outer peripheri on an edge in the floor and is supported by the movable platform part 52 by sliding elements 71 provided at the under side thereof.
The movable platform part 52 is comprised by a number, eight in this case, of rotatable, essentially triangular segments 54. Each segment 54 rests on a support structure, which is secured around the shaft and consists of a number of joined ring segments 55 to form an annular base plate. The base plate slidably supports the triangular segments 54 through support elements 56 and 57, e.g. in the form of profile parts 56, and friction reducing slide elements 58, 59. Each triangular segment 54 is rotatable about a fixed pivot 60 at the "corner of the triangle" closest to the outer circumference. The edge area 61 of the longest side of the triangular segment 54 has a small step, and a second edge area 62 of a second side has a thickness, which corresponds to the height of the step.
The top surface of the second edge area 62 forms a continuous prolongation of the rest of the work surface of the segment 54 and forms a part thereof. The lower surface of the second edge area 62 may rest and slide upon the upper surface of the first edge area 61 of an adjacent triangular segment 54, so that a continuous, substantially uninterruped work surface is formed by the assembled triangular segments. Each segment 54 is rotatable about its pivot axis 60 between an inner position, shown with full lines, in Fig. 2, and an outer position, shown with broken lines. The triangular segments 54 are each driven by means of a pinion 63 in engagement with an arcuate gear segment 64 provided on each triangular segment 54, the centre axis of which coincides with the pivot axis 60.
Thus, when the pinion 63 is rotated, it will rotate the corresponding triangular segment 54 through its engagement with the arcuate gear segment 64, so that the inner point 64 of the triangular segment 54 will approach or depart from the centre axis of the platform in dependence of the rotary direction of the pinion 63. Limit switches 66, sensing the extreme positions of the gear segments 64, are provided to interrupt the driving of the arcuate gear segments 64. Of course it need not be the positions of the gear segments 64 that are sensed, but any other element on the triangular segment 54 may operate suitably disposed sensors, as well.
Referring to Fig. 3, the pinions 63 are driven by means of one or more electric motor(s) 67, which directly or through a gear drives/drive the pinions 63. For synchroniza tion of the movement and of the driving of all the triangular segments 54 of the movable platform part 52, a plurality of interconnected synchronization gear wheels 68, 69 are provided, more exactly there are twice as many such gear wheels as there are triangular segments 54. The rotary axes of the synchronization gear wheels 68, 69 are spaced around the work platform at the same distance from the sensor axis of the platform. Furthermore, these drive and synchronization gear wheels 68, 69 are rotatably supported on the bottom plate 55.
A pinion 63 is non-rotatably secured to the rotary shaft of each second synchronization gear wheel 68. Thus, when a pinion 63 rotates in engagement with the corresponding gear segment 64, the synchronization wheel 68 on the same rotary shaft also will rotate. The gear wheel 68 then will rotate the adjacent synchronization gear wheel 69 through its toothed engagement with the same, which in turn rotates the next synchronization gear wheel 68 of the following triangular segment 54. On the rotary shaft of said next synchronization gear wheel 69, the pinion 63 for said following triangular segment 54 is secured, which through its engagement with corresponding arcuate gear segment 64 will rotate said triangular segment 54. Thus, by means of the synchronization gear wheels 68, 69 all triangular segments 54 comprised in the inner platform part will have the same angular displacement.
Those sides of the triangular segments 54, which may come into contact with the work piece are each provided with a squeeze protection strip 70, made of a protecting and cushioning material, such as rubber, to prevent damage of the work piece, if the triangular segments 54 would come into contact with the workpiece during an adjustment movement of the work platform. Each squeeze protection strip 70 further comprises sensor means, which at contact with the work piece stops the power supply to the drive motors.
In the described structure the radially interior portions of the segments 54 define a centre opening. Upon energizing of the diametrically disposed motors, in this case two, all platform segments 54 will move in synchronism, so that in dependence of the drive direction of the driving means, the centre axis of the platform. The width of the centre opening will then continuously decrease and increase, respectively, similar to an iris diaphragm in a camera. As an example should be mentioned, that in a practical embodiment of the invention the "diameter" of the opening is variable from about 0,8 meters to about 3,2 meters. The shift of the opening is very rapid and an adjustment to the various diameters of the work piece could easily be accomplished.
Without risking any short-term or long-term industrial injuries, the mechanics may come close to the work piece, resulting in a high degree of precision during the repair and/or the maintenance thereof. At the same time a continuous, substantially even work surface between the outer, annular platform part 51 and the centre opening is provided.
This is an advantage in comparison with prior art, wherein the platform area corresponds to the outer, annular platform part according to the invention.
Of course, the movable segments may geometrically have a different shape from that shown in the drawing. It should be obvious that the number of segments in the inner platform part 52 is arbitrary.
A greater number of segments provides for a more continuous centre opening, which however results in a higher manufacturing cost.