GB2195399A - Lifting equipment - Google Patents

Abstract

A pneumatic hoist, particularly for aircraft, comprises a set of inflatable airtight chambers (12) arranged one on top of the other to form a lifting bolster. A control console 20 is used to control separately the air supply to at least some of the individual chambers. Maximum pressure and relief valves are provided to maintain the desired pressure in the chambers and in particular in the uppermost, aircraft contacting chamber (14). The relief valves are adjustable. <IMAGE>

Description

SPECIFICATION Lifting equipment Field of the Invention: This invention relstes to hoisting/lifting equipment particularly, but not exclusively for aircraft.

Known pneumatic lifting equipment includes a lifting bolster comprising several airtight chambers or bags constructed from flexible airtight material and arranged one or top of the other, as a stack. Each chamber is fitted with an air supply connection such as a nipple. The apparatus further includes a control console having an air input connection and a set of controls for each of the chambers, the number of sets of controls corresponding to the number of chambers. Each chamber has its own individual supply hose and valve.

An aircraft hoist of the aforesaid type is disclosed in Applicant's German Utility Model No. 85 06736. Each individual chamber achieves optimal stability when filled to a pressure of between 0.4 and 0.5 bar. The pressure of 0.5 bar is also the upper pressure limit because at this level a valve at the control console operates to prevent any further increase in pressure. Although during use the lower chambers of a stack of chambers may be pressurised to any suitable pressure level commensurate with achieving optimal stability in the stack, it is normal to remain within the above-mentioned range, because those chambers which come into contact with an aircraft should be pressurised only within the limits prescribed by the aircraft manufacturer.For some aircraft the maximum permitted pressure permitted in the upper, aircraft-contacting chambers is 0.5 bar, but for other aircraft (especially those of more recent construction) a much lower pressure is permitted. For example, the maximum permitted pressure to be applied to the underside of a 757 fuselage is 0.16 bar and for the underside of the wings of a 747 the pressure must not exceed 0.39 bar.

Using prior art methods and apparatus it is not always simple to achieve the pressure prescribed by the manufacturer for a given aircraft, especially in that chamber which comes into contact with the surface of the aircraft. It is also especially difficult to maintain the correct pressure throughout a period of use. During inflation of the chamber the pertinent manometer must be closely monitored so that too much pressure is not introduced. Operator errors cannot always be ruled out. Even if the upper chambers have been correctly inflated there is no guarantee whatsoever that the pressure in these chambers will be maintained at the correct level during the whole of the period in which the aircraft is supported by the pneumatic hoist.

The sun or other source of heat may warm the air in the chambers, thereby leading to an increase in the pressure, because the inflated capacity of the chambers is essentially constant. Such variations in pressure can result in pressure levels which may lead to damage to the aircraft and even to claims for compensation. This is particularly true for aircraft for which only a very low maximum load pressure is permitted. On the other hand, the pressure in the aircraft-contacting chambers may fall to such an extent that the chambers below those chambers also come into contact with the shell of the aircraft, because the upper chambers have collapsed so much. In such a case there is a very real danger that the maximum permitted pressure will be grossly exceeded, especially if the second chamber from the top of the stack is' filled to a pressure of 0.5 bar, which is normal.

Objects of the Invention: It is an object of the invention to avoid or at least mitigate the disadvantages which have just been described in relation to known pneumatic lifting equipment. In particular it is an object of the invention to ensure that as far as practicable a desired pressure in that chamber (normally the upper chamber) which is in use in contact with an aircraft can be achieved with precision, checked and maintained as long as necessary.

Brief Description of the Invention According to the present invention a control console for a pneumatic hoist comprises an overflow valve fitted with a pressure regulating device. The valve is preferably provided with a clear indication of operating pressure.

More preferably it is adapted to be controlled by a set of interchangeable fittings, especially in the form of plug-in cards. By using a valve of the kind just recited it is no longer necessary to monitor manometer readings visually, with the result that operator maladjustments are almost totally precluded.

The overflow valve ensures that any increase in pressure (caused by temperature change and/or by the operator) will not result in a pressure exceeding the permitted level for a particular aircraft. Instead, the overflow valve ensures that any excess pressure above the target pressure is immediately vented.

Thus if the sun warms a stack of lifting bolsters which are inflated and in use to support an aircraft, the pressure in the uppermost, aircraft contacting chamber will slowly increase.

With the overflow valve of this invention there will be a periodic, compensating discharge of air from the chamber so that the correct pressure is maintained.

Furthermore the same valve can also compensate for pressure loss, because it is possible to introduce air to make up for such losses, without risk of exceeding the maximum pressure. Thus if there is no loss to be made up the excess air volume will simply be vented via the valve. If there is a pressure loss to be compensated for, the valve will permit air flow into the chamber until the desired pressure level is restored.

Preferably, the apparatus additionally includes a conventional maximum pressure set- ting valve to ensure that in no case can a preset absolute maximum of, say, 0.5 bar be exceeded. This valve acts as a safety device in the event of any malfunction of the overflow valve. However it is particularly preferred that both valves have the same maximum settling, so that regardless of which valve malfunctions the other will hold the chamber pressure within safe limits.

In principle it is possible to provide similar overflow valves for each chamber in a set or stack, but in practice it is preferable to provide one such valve for at least the uppermost (aircraft-contacting) chamber, whilst inflating the chambers below to the optimum pressure for stability and then maintaining that pressure by means of an overflow valve.

According to a further aspect of the invention, the overflow valve may be constituted by an adjustable pressure-reducing valve, the high pressure side of which is attached to the air supply and the low pressure side of which is attached to the hose to the chamber. At each side of this valve a non-return valve is inserted in the line, with the inlet side of the non-return valve directed towards the pressure reducing valve. In this way, a known pressure reducing valve can be used as the overflow valve. The non-return valve ensures that the chamber which is in contact with the aircraft cannot be filled with air via the pressure reducing valve, but instead that the latter can be used to reduce the pressure. This has the advantage that existing, known pressure-reducing valves have a regulatory device which can be set to a desired level of pressure reduction.

In a modified version of the arrangement just described the overflow valve may be spring-loaded, a setting device being provided to modify the behaviour of the spring whereby the response of the valve can be modified.

Overflow valves constructed in this way can be used for very precise functions. Additionally, because the setting is mechanically determined, the adjusting mechanism can be set to give a precise pressure level at which the valve is to operate to decrease pressure.

In a further modification the adjusting device may be fitted with either a control screw or with a two wheel mechanism adapted to regulate the strength of the spring. One wheel may set the pressure in tenths of a bar, the other in hundredths of a bar. In both cases highly accurate, readily monitorable settings can be achieved.

Brief Description of the Drawings: In order that the invention be better understood preferred embodiments of it will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is general perspective view of a pneumatic hoist for an aircraft, fitted with a control panel Figure 2 is a schematic circuit diagram illustrating the air supply for several chambers of the hoist of Fig. 1, including those which in use come into contact with an aircraft.

Figure 3 is a schematic diagram corresponding to Fig. 2, but including a spring-loaded overflow valve, the spring of which is responsive to a control screw.

Figure 4 is another schematic diagram, similar to Fig. 2, but in this case with the addition of a plug-in card for control purposes.

Figure 5 is a cross-sectional view of part of Fig. 4 taken along line V-V of the latter Figure, and Figure 6 is a cross-sectional view of an adjusting device similar to that shown in Fig. 3, but with the addition of two numerical counters.

Description of the Embodiments: Fig. 1 illustrates the construction of a pneumatic aircraft hoist. It comprises a hoist 10 having eight individual airtight chambers 12,14 arranged one over the other to form a stack.

The chambers are constructed from an airtight fabric. The uppermost chamber 14 is the chamber which in use comes into contact with the aircraft (not shown.) It may be divided into a number of individual chambers by vertical dividing panels, but as shown it appears as a single chamber 14. Each chamber 12 has a nipple 16 for an air input connection. The nipple itself does not function as a valve. Attached to the nipple are hoses 18,20 which are connected to a control panel 22. This is referred to as the control console. In this case each chamber 12,14 is fitted with its own control unit 24 which (as is particularly shown in Fig. 2) contains a control valve 26, a manometer 28 and a safety valve 30.

In addition the control unit, or units, for the aircraft-contacting chambers 14 include an overflow valve 34 which is incorporated into the control section 22 and which is fitted with a pressure control device 32. This will be discussed in further detail below. The control valves 26 are preferably of the "dead man" kind, remaining closed unless positively actuated. From this closed or rest position they can be operated in one direction to fill the chambers 12,14 and in the opposite direction to release air from the latter. They are conected to a common air supply 36, whose pressure exceeds 0.5 bar. A manometer 28 is connected to each control valve and enables the pressure in each chamber 12,14 to be measured.Additionally, the safety valves 30 are set to open automatically when chamber pressure exceeds 0.5 bar. - It will be appreciated that the side of the control valve 26 which is nearest to the chamber is connected both to the manometer 28 and to the safety valve 30, as well as to the hose 18,20.

It is preferred that a special hose be provided for the aircraft-contacting chamber(s) 14, this hose having couplings which can be attached only to the relevant control unit 24 and to the nipple 16. Then this particular hose connot be confused with other hoses and it will not be possible to wrongly connect other hoses to nipple 16. The special hose may be colour-coded so that when the hoist is being assembled prior to inflation the hose can be speedily and correctly connected.

In Fig. 2, the control units 24 for the chamber(s) which in use come into contact with an aircraft are also each connected via a supply line 38 to an overflow valve 34 constituted by a pressure-reducing valve. Connection is made to the low pressure side of the valve and a manometer 40 is also connected to this side of the valve 34. The high pressure side of the valve 34 is connected to the common air supply 36 by a supply line 42. In each of the supply lines 38,42 there is a non-return valve, 44 and 46 respectively. Their purpose is to ensure that valve 34 functions essentially statically and is not used during inflation of the associated chamber 14. The non-return valves 44 in the supply lines 38 also serve to isolate the feeds to each individual chamber, so that it is possible to use one single pressure-reducing valve for several chambers.Fig. 2 shows this in respect of three chambers.

If, in use, a pressure appears at the low pressure side of the valve 34 and is greater than the set pressure for the valve 34, then air will be released from the chamber in question until the correct (set) pressure is restored.

Referring to Fig. 3, a different version of the overflow valve 34 is shown. This version comprises a housing fitted with a valve opening 48 connected by a supply line 38 to the control valve 26. Opposite the valve opening 48 there is a valve element 50 which is connected to an operating rod 52 and retained in the housing by a crimped supporting/locating member 54. However the latter is also movable axially with respect to the axis of the control rod 52. Preferably the member 54 is constituted by a sealing membrane through which the rod 52 extends, with the valve element 50 on one side and the rest of the rod 52 on the other side. Preferably the operating rod is supported so that it is constrained to move only in an axial direction. Control of this movement is then achieved by means of an adjusting nut 56 which will now be described in greater detail.

The nut 56 surrounds the housing, which is cylindrical at that point. It has an internal thread which is engaged with an external thread 58 on the housing. The adjusting nut 56 is essentially cup-shaped although an axial guide bearing 60 protrudes centrally, parallel to the sides of the cup. The guide bearing slides over and along the activating rod rod 52, but without exerting any direct control on the axial position of the rod. Instead a helical spring 62 is located on the rod between the member 54 and the base of the cup-shaped adjusting nut 56. The spring is a compression spring which urges apart, in an axial direction, the two components just mentioned. The adjusting nut 56 enables the pressure applied to the valve part 50 to be varied.Attached to the outside wall of the housing is a numbered scale 63, part of which is masked by the nut 56 so that the opening pressure setting of valve 34 is clearly visible.

The end section of the housing of the valve 34 to which the nut 56 belongs juts prominently out of the control console 22 while the other part, to which the supply 38 is connected, remains concealed inside the console.

Turning the nut 56 sets the pressure at which the overflow valve operates.

Use of a sealing membrane for the member 54 has the advantage that the area to the left (in Fig. 3) of the membrane and which includes the valve opening 48 as well as the valve part 50, is separated from the other mechanical parts of the valve. Thus no dirt can enter the valve area. Expelled air can escape through an opening 64, but no air is drawn in. Accordingly there is no fear of contamination of the valve area. Also, because the mechanical valve area which contains the helical spring 62 can be made so that it is virtually sealed off, there is no danger that dirt and the like can penetrate and interfere with the mechanical adjustment. The adjusting nut 56 can be screwed into the housing only so far as to exert on the spring a pressure corresponding to an operating pressure of 0.5 bar.

It is impossible to set the nut beyond this level. If turned in the opposite direction a lock on the nut 56 ensures that it cannot be unscrewed involuntarily. Parts 56, 58 and 63 constitute the adjusting device generally indicated as 66.

Referring now to Fig. 4, a similar valve is shown but with a different adjusting device.

Inside the housing, which is again cylindrical, there is a sliding cup 68 joined to a guide bearing 60 which surrounds, but slides over the operating rod 52. This cup has in addition an adjustable pin 70 which passes through a retaining ring 72 and protrudes into a slot cavity 74, (Fig. 5.) The cavity 74 is the receptacle for a flat but rigid card insert 76, the purpose of which is to press the adjustable pin in as far as it necessary to set the opening pressure of the valve at a particular level.

Each type of aircraft will be provided with several such card inserts 76, at least one of which would be for the underside of the wings and one for the underside of the fuse lage. The inserts will be clearly marked so that the operator can quickly recognise the function of each insert. For example, one may bear the legend: "747 WING 0. 39 BAR." The card inserts may be made of, say, 1 mm thick plastic or metal and are constructed so that it is immaterial which way they are introduced into the slot cavity 74.

Each edge of the card begins with a leading portion 80 which slides into a corresponding slot 82, but which does not on entry contact the adjusting pin 70. Contact is effected only by an adjacent diagonal control edge 84. As the card insert 76 is introduced into the slot cavity 74 the pin 70 rides along the control edge 84 and is pushed upwards, according to the special features of the card. A retaining edge 86 which extends normal to the pin is located next to the control edge. The pin 70 engages this retaining edge as the card is fully inserted into the slot until the edge of the latter seats against a seat on the card, as indicated at 88. This is the operating position and the pressure at which the valve 34 opens is determined by the geometry of the card insert 76. A blocking ring located above the retaining ring 72 determines the furthest point to which the pin can be displaced.The retaining ring 72 prevents dirt from entering the area which houses the spring. Parts 70 and 74 to 86 constitute the adjusting device.

Fig. 6 illustrates a different adjusting device which may replace the one just described, the rest of the valve construction 34 remaining unchanged. The purpose of this adjusting device is to render it both simple to read and to regulate the deflation pressure. Next to the adjusting pin 70 there is a captive nut 94 which is preferably non-circular and fitted into a correspondingly shaped fixed guide 94 which allows it to move axially, but not to rotate. The captive nut has an inner thread of relatively steep pitch which is engaged with a correspondingly threaded portion 96 of a rod 98. Below the threaded portion the rod is non-circular, preferably hexagonal. This region of the rod 98 passes through a first numbered wheel 100 which is rotatable, but not mov able axially of the rod. The circumference of the wheel is marked 0 to 9.The wheel 100 is kept in place by a locking device, (not shown.) If the wheel is turned the the position of the captive nut 92 is varied by relative movement of the threaded region 96, thereby moving the adjusting rod 70 up or down. The gradations (in tenths of a bar) on the wheel 100 are thus implemented.

Below the wheel 100 there is a second, identically numbered wheel 102 which is simi larly mounted and adjustable. It includes a cantilevered axial extension which is internally screw-threaded with a very fine pitch thread.

This section is engaged on a threaded section 104 of a second rod 106. This latter rod is also non-circular at its lower extremity; it is preferably hexagonal. The rod 106 is mounted in a rigid guide 114 so that it can move axially, but not rotate. It is spring-loaded by a leaf spring 112. When the second wheel 102 is turned, the second rod 106 is moved up or down. The second rod is coaxial with the first rod 98 and end to end with respect to part of it. The abutting end parts of the rod 98 and 106 are shaped to receive and retain a ball 110. Other constructions are possible for this area where the rods meet.

Claims (12)

1. A pneumatic hoist, particularly for aircraft, comprising a lifting bolster consisting of a plurality of chambers arranged one on top of the other, said chambers being made from a flexible airtight material and each having a nipple for an air supply connection, a control console fitted with a connection for an air supply and having a plurality of control units, each control unit being fitted with a control valve and a connection whereby it may be connected to an individual chamber by hose means, together with an overflow valve incorporated into one of said control units, said valve including a pressure regulator.

2. A hoist according to claim 1 wherein said overflow valve is incorporated into the control unit for the air supply to that chamber of the bolster which in use will contact an aircraft to be lifted.

3. A hoist according to claim 1 wherein part of an adjusting device for the pressure regulator is so disposed as to be visible, the remaining portion being within the control unit.

4. A hoist according to claim 1 wherein the overflow valve comprises an adjustable pressure reducing valve, the high pressure side of which is connected to an air supply, the low pressure side being connected to a hose connection, a non-return valve being inserted in each of the low and high pressure connections to the valve, the flow direction of said non-return valve being in each case towards the pressure reducing valve.

5. A hoist according to claim 1 wherein the overflow valve includes a spring acting on a part of the valve, and a adjusting device for adjusting the force applied by said spring.

6. A hoist according to claim 5 wherein the adjusting device is fitted with a cupshaped adjusting nut screw-threaded to a housing and acting on a helical spring.

7. A hoist according to claim 5 wherein the adjusting device includes an adjusting rod, one end of which is linked to the valve component and the other end of which supports the spring.

8. A hoist according to claim 7 wherein the adjusting device includes a receptacle for a card insert and a slot cavity accessible through an entry slot in a front cover plate for the control unit.

9. A hoist according to claim 8 wherein said card insert is symmetrically shaped and has an insert edge, a diagonal control edge and a retaining edge parallel to the insert edge.

10. A hoist according to claim 7 wherein the adjusting device has two circular, numbered wheels carried by respective coaxially mounted rods, one of which acts directly on the adjusting rod and the other of which acts against the first rod.

11. A hoist according to any of claims 5-10 wherein the control unit includes a stop effective to limit the force exerted against the valve component by the spring to a given maximum.

12. A pneumatic hoist substantially as hereinbefore described in relation to and as illustrated by the accompanying drawings.