GB2385666A

GB2385666A - Pressure sensor device suitable for use with parachutes

Info

Publication number: GB2385666A
Application number: GB0204339A
Authority: GB
Inventors: David Richard Jordan Hirst
Original assignee: Airborne Systems Ltd
Current assignee: Airborne Systems Ltd
Priority date: 2002-02-25
Filing date: 2002-02-25
Publication date: 2003-08-27
Anticipated expiration: 2022-02-25
Also published as: GB2385666B; GB0204339D0

Abstract

A mechanism includes an inlet port 12 for receiving air for supply to a sensor producing a signal which is a function of the pressure of said air. The inlet port 12 is connected to an inlet device 28 for providing air to the inlet port from a location remote from the sensor. This allows the sensed pressure to be characteristic of the ambient pressure, and so provides an accurate signal. The mechanism may incorporated into both an automatic parachute opening device and an altimeter. The embodiment shows a parachute opening device 10 having an T-shape tube configuration 29, 30, 31 inlet device. Any number of tubes in any type of configuration may be used, and the tubes may be perforated to provide averaged air pressure to the sensor. The device may include a reservoir (38, figure 2) to damp pressure fluctuations.

Description

MECHANISM FOR USE WITH PARACHUTES The invention relates to mechanisms for use with parachutes and includes also automatic parachute opening devices incorporating such mechanisms and load/parachute combinations incorporating such mechanisms.

There are mechanisms for use with a parachute that include an inlet port receiving air for supply to a sensor producing a signal which is a function of the pressure of said air. Examples of these are automatic parachute opening devices which open a parachute automatically at a predetermined height above ground, if the parachute has not already been deployed and altimeters. It is a problem with such mechanisms that the air pressure detected by the sensor can depend on the location of the mechanism relative to a load associated with the parachute. The term"load"is used to include both inanimate loads and persons.

The mechanism will be located at a fixed point on the load, for example, within a parachute pack, and this position may not be one in which the inlet port receives air at a pressure which is the ambient pressure around the load at a particular time, even if the load maintains a fixed orientation during descent. For example, in the case of a back-mounted parachute, the inlet may be in a load pressure zone in the wake of a person descending face first. This may lead to the sensor providing a signal which is incorrect for the pressure of the ambient air. This is plainly undesirable.

According to a first aspect of the invention, there is provided a mechanism for use with a parachute including an input port receiving air for supply to a sensor producing a signal which is a function of the pressure of said air, the inlet port being connected to an inlet device for providing air to said input port from a location remote from said input port.

The use of the inlet device allows the air to be taken from a selected point or points on the load remote from the input port at which it is known that the air pressure is characteristic of the ambient air pressure. In this way, the sensor can produce a more accurate signal.

It is also a problem with mechanisms of this kind that the load may not maintain the same orientation during descent. This is particularly true where the load is inanimate and may tumble prior to deployment of the parachute. In this case, the inlet may supply air to the sensor whose pressure fluctuates rapidly.

In a preferred embodiment of the invention, the inlet device includes means for averaging the pressure of the air provided to the inlet port.

In this way, fluctuations in air pressures, such as those occurring through tumbling of the load, are mitigated or avoided.

According to a second aspect of the invention, there is provided an automatic parachute opening device for opening a parachute associated with a load when the device detects that predetermined criteria have been met, said criteria including at least a predetermined height of the load above a datum, the device including a sensor for converting sensed air pressure into a signal representing a height indicated by said air pressure, said device including a mechanism according to the first aspect of the invention.

According to a third aspect of the invention, there is provided a load/parachute combination including an automatic parachute opening device having a mechanism according to a first aspect of the invention, in which the device comprises an elongate flexible member having a passage extending therethrough to connect at least one air inlet to said inlet port, the elongate flexible member extending around said load to locate said at least one inlet at a predetermined position relative to the load.

The following is a more detailed description of some embodiments of the invention, by way of example, reference being made to the accompanying drawings in which :- Figure 1 is a view, partially broken away, of an automatic parachute opening device for opening a parachute associated with a load, an inlet port of the device being connected to a first form of inlet device for extending around the load, and

Figure 2 is a view of the same automatic parachute opening device as shown in Figure 1 but having the inlet port of the device connected to a second form of inlet device.

Referring first to Figure 1, the automatic parachute opening device 10 comprises a casing 11 having an inlet port 12 connected by a flow path to a sensor (not shown).

The flow path contains a filter 13, such as a sintered filter, for removing dust and dirt.

In addition, the flow path contains one or more beads of a liquid, such as silicone oil, which prevents principally the passage of moisture to the sensor but also performs some damping on the air in the flow path so evening out the excessive fluctuations in air pressure.

The sensor produces a signal representative of the sensed air pressure which is fed to a control circuit 14. The control circuit 14 compares this signal with a stored signal representing a height at which an associated parachute is to be opened, if opening has not already taken place. When the signal from the sensor indicates that the predetermined height has been reached, the control circuit 14 sends a signal to a stepper motor 15 having an output shaft 16 that rotates to move a block 17 on a worm gear at the end of the output shaft 16 in a direction axially along the shaft 16. This movement is translated by a lever arm 18 into a rotational movement of a secondary lever 19 in a clockwise direction as viewed in Figure 1. This moves an end of the secondary lever 19 out of engagement with a first end of a primary lever 20 which then rotates clockwise as shown in Figure 1 under the action of a lever spring 22.

This movement moves a notch 22 at a second end of the primary lever 20 out of engagement with a pin 23 on a piston 24. In the position shown in Figure 1, the piston is in a cocked position where the piston 24 holds a spring 25 compressed against the casing 11 and where a piston rod 26 projects from an extension tube 27 carried by the casing 11.

The release of the pin 23 results in the piston 24 being retracted by the spring 25 to draw the piston rod 26 through the extension tube 27 and into the casing 11. The piston 24 can be manually re-cocked.

As seen in Figure 1, the inlet port 12 is connected to an inlet device indicated generally at 28. The inlet device 28 comprises first, second and third lengths of flexible tubing 29,30, 31 connected in a T-configuration. The first tube 29 has one end connected to the inlet port 12 and the other end connected to a limb of a Tconnector 32. The second and third tubes 30,31 have respective first ends connected to respective limbs of the T-connector 32 and have respective free second ends 35.

As will be seen in Figure 1, the second and third tubes 30,31 are significantly longer than the first tube 29. The second ends 35 of the second and third tubes 30,31 are open.

In use, the opening device 10 is associated with a parachute in a parachute container attached to a load which may be either an inanimate object or a person. The container

is held closed by locking pins (not shown) which are connected to the piston rod 26.

The piston rod 26 is held cocked as described above.

The second and third tubes 30,31 are located on the load such that the second ends 35 of the second and third tubes 30,31 are located at a point or points on the load which are likely to be in areas where the air pressure at the second ends 35 is the same as the ambient air pressure. Where the parachute is a back-mounted parachute on the person, this may be out of the wake behind the person.

When the load is dropped, air enters the second ends 35 of the second and third tubes 30,31 and passes through the first tube 29 to the inlet port 12. There, it passes through the filter 13 to remove dust and dirt and causes the bead or beads of liquid in the flow path to move along the flow path in accordance with the pressure in the tubes 29,30, 31. The movements of the liquid are translated into corresponding pressure variations at the sensor which outputs an electrical signal which is a function of the sensed pressure. This in turn is fed to the control circuit 14 where, when the sensed pressure signal from the sensor is the same as the stored pressure signal, the stepper motor 15 is actuated to cause the primary lever 20 to rotate clockwise as described above and release the pin 23 to retract the piston rod 26. This acts to withdraw the pins from the container and release the parachute.

It is a particular problem with inanimate loads that, before deployment of the parachute, they can tend to tumble. If this occurs, the pressure at the inlet port 12 can fluctuate significantly over very short periods of time, even with the second and third tubes 30,31 as described above. In order to overcome this, the second and third tubes 30,31 may be provided with a plurality of holes spaced apart along the length of the second and third tubes 30,31 respectively. For example, where the second and third tubes 30,31 are 3mm outside diameter tubes, the pitch of the holes along the length may be 25mm.

The holes may be preformed in the second and third tubes 30,31 before they are assembled into the device. In an alternative proposal, the second and third tubes 30,31 may be sewn to fabric associated with the parachute or the load. In this case, the stitch holes are arranged to pass through the second and third tubes 30,31 at a pitch of 25 mm and provide the necessary holes.

The use of a plurality of air inlets allows the second and third tubes 30,31 to provide an averaged air pressure to the sensor. This mitigates or removes fluctuations in air pressure at the sensor caused by tumbling loads.

It will be appreciated that the arrangement of Figure 1 need not have first, second and third tubes 29, 30, 31 arranged in a T-configuration. There may be simply a single tube or 2 tubes, or four or more tubes arranged in any required configuration. The holes,

whether pre-formed or produced by stitching, need not be regularly spaced, they could be at any desired spacing. The pre-forming may be by the punching of holes in the tubes 30,31. Alternatively, the tubes 30,31 may be made from an air permeable material.

An alternative arrangement for the inlet device is shown in Figure 2. In this Figure, the opening device 10 is as described above with reference to Figure 1 and so will not be described in any further detail. In this arrangement, the inlet device is formed by a single tube 36 having a first end connected to the inlet port 12 and having an open second end 37. Adjacent the open end, the tube 36 is formed with a reservoir 38 whose volume is large compared with the volume of the tube 36. The tube 36 is uninterrupted between its ends; i. e. there are no holes in the tube 36. The tube 30 may, as seen inset in Figure 2, contain a monofilament thread 50 which forms a support member to prevent the tube 30 kinking or collapsing.

In use, the opening device of Figure 2 is arranged as described above with reference to Figure 1. The tube 36 is located on the load such that the second end 37 is at a point where the pressure is likely to be close to the ambient pressure around the load. Air from the second end 37 passes to the sensor through the inlet port 12 and the device is operated as described above with reference to Figure 1. As seen inset in Figure 2, the second end 37 may be formed by a metal tube 51 containing a wire 52 which forms a throttle valve. The presence of the reservoir 38 and the opening at the

second end 37 act to damp out fluctuations in the pressure not caused by changes in altitude but caused, for example, by the load tumbling. Accordingly, the parachute is opened at an accurate height.

It will be appreciated that the reservoir 38 need not be formed as described above; it could be formed simply by a portion of the tube 36 of larger diameter. In addition, the reservoir 38 need not be formed integrally with the tube 36; it could be a part formed separately from the tube 36 and attached to the tube 36.

It will also be appreciated that the opening device 10 is only an example of a device with which the inlet devices of Figures 1 and 2, and their associated modifications described above can be used. For example, the opening device may be as described in our UK Patent Application No. 9817716.5. The inlet device may also be used with other mechanisms carried by a parachute or a parachutist such as an altimeter.

Claims

CLAIMS 1. A mechanism for use with a parachute including an inlet port receiving air for supply to a sensor producing a signal which is a function of the pressure of said air, the inlet port being connected to an inlet device for providing air to said input port from a location remote from said input port.
2. A mechanism according to claim 1 wherein the inlet device includes means for averaging the pressure of the air provided to the input port and for removing fluctuations in pressure not caused by changes of altitude.
3. A mechanism according to claim 1 or claim 2 wherein the device comprises an elongate flexible member having a passage extending therethrough to connect at least one air inlet to said inlet port, said member being capable of being wrapped around a load to be supported by a parachute associated with said sensor to locate the at least one inlet at a required position relative to the load.
4. A mechanism according to claim 3 wherein said elongate flexible member comprises a flexible tube connected at one end to said inlet port.
5. A mechanism according to claim 4 wherein an elongate flexible support extends through the flexible tube to prevent the flexible tube kinking or collapsing.

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6. A mechanism according to claim 5 wherein said support member comprises a monofilament thread.
7. A mechanism according to any one of claims 3 to 6 when dependent on claim 2 wherein the member includes a plurality of air inlets spaced along the length of the member, the plurality of inlets providing said means for averaging the pressure of air supplied to said inlet port.
8. A mechanism according to claim 7 wherein said plurality of air inlets are pre-formed in the member.
9. A mechanism according to claim 7 wherein, in use, the member is stitched to a fabric associated with the parachute and/or the load, the stitching passing through said passage to provide said plurality of air inlets.
10. A mechanism according to any one of claims 3 to 9 when dependent on claim 2 wherein the member incorporates a reservoir for receiving a volume of air from said at least one air inlet, the reservoir having an outlet leading via said passage to the inlet port, the reservoir and the outlet averaging the pressure of the air received from said at least one inlet.

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11. A mechanism according to claim 10 wherein the reservoir is located in a portion of said member remote from the inlet port.
12. A mechanism for a parachute substantially as hereinbefore described with reference to the accompanying drawings.
13. An automatic parachute opening device for opening a parachute associated with a load when the device detects that predetermined criteria have been met, said criteria including at least a predetermined height of the load above a datum, the device including a sensor for converting a sensed air pressure into a signal representing a hight indicated by said air pressure, said device including a mechanism according to any one of claims 1 to 10 and the sensor being in communication with said inlet port.
14. A device according to claim 13 wherein the sensor is connected to the inlet port by a flow path said path containing a filter.
15. A device according to claim 14 wherein the path. contains at least one bead of liquid, said liquid acting to damp changes in air pressure in said path and to prevent the passage of moisture to the sensor.
16. An automatic parachute opening device substantially as hereinbefore described with reference to the accompanying drawings.

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17. A load/parachute combination including an automatic parachute opening device having a mechanism according to claim 3 or any claim appendant thereto, the elongate flexible member extending around said load to locate said at least one inlet at a predetermined position relative to the load.
18. A load/parachute combination according to claim 17 in which the load is a person, and in which the mechanism is in accordance with claim 7 or any claim appendant thereto, the member being wrapped circumferentially around the person in a plane generally normal to the height of the person.
19. A load/parachute combination substantially as hereinbefore described with reference to the accompanying drawings.
20. An altimeter incorporating a mechanism as claimed in any one of claims 1 to 12.