GB2534132A

GB2534132A - Pressure sensing switch

Info

Publication number: GB2534132A
Application number: GB1500240.5A
Authority: GB
Inventors: Altaf Husain Karampurwala Mustafa
Original assignee: Intelligent Energy Ltd
Current assignee: Intelligent Energy Ltd
Priority date: 2015-01-08
Filing date: 2015-01-08
Publication date: 2016-07-20
Also published as: GB201500240D0

Abstract

A pressure-sensing switch comprises a first part for inclusion in a controller 20 and a second part for inclusion in a pressure vessel 2 that may contain pressurised fluid 4 such as hydrogen for powering an electrochemical fuel cell. When vessel 2 is connected to controller 20 conductive ring contact 12 electrically connects with contact 24,25 on a plunger 22 but when its internal pressure exceeds a level diaphragm 5 extends from a retracted position displacing the plunger 22 and opening the contacts 12,24,25. Plunger contacts 24, 25 can connect with a printed circuit board 125 via conductive paths 26, 27 and spring-loaded pick-up contacts 30,31; and be bridged by contact 12 that disconnects from both contacts when plunger 22 is displaced. Alternatively there may be a single contact on the plunger and an additional contact connecting housings of the controller and diaphragm parts. The pressure sensing switch can be used to disable a pump (fig 5, 64) that is in a used to pressurise vessel 2, being a component of a disposable part (fig 5, 41) such as a reaction chamber module or refill cartridge.

Description

PRESSURE SENSING SWITCH

The present invention relates to pressure switches and in particular, though not exclusively to pressure switches suitable for sensing an over-pressure condition in, for example, a gas generator cartridge or a reactor module.

Electrochemical fuel cells require a source of fuel and oxidant to generate electrical energy. A common type of fuel cell uses hydrogen as a fuel source. In some applications, it is convenient to use a fuel supply cartridge which incorporates a reactor module to generate hydrogen as it is required. Such reactor modules may comprise a reaction chamber pre-charged with a first reactant, for example, a metal hydride (such as sodium borohydride) to which can be added a second reactant (e.g. water) to generate hydrogen as and when required. Where the second reactant is a fluid, control of the flow of hydrogen can be conveniently controlled by monitoring hydrogen pressure in the reaction chamber and controlling a pump delivering the fluid reactant to the reaction chamber.

It is desirable to provide a safety mechanism capable of shutting off such a pump in the event of an overpressure condition.

According to one aspect, the present invention provides a pressure-sensing switch comprising: a first part comprising a first electrical contact biased towards an extended position relative to a housing of the first part; a second part comprising: a diaphragm extendable between a retracted position and an extended position as a function of internal pressure within a chamber within a housing of the second part, a second electrical contact on the second part housing configured to make electrical connection with the first electrical contact when the first part is connected to the second part and when the internal pressure is at a first level, and a plunger, displaceable by the diaphragm, configured to displace the first contact from the second contact when the first part is connected to the second part and the internal pressure is at a second level.

The first electrical contact may comprise a pair of electrical contacts and the second electrical contact may be configured to connect the pair of electrical contacts to one another when the first part is connected to the second part and the internal pressure is at the first level. The second electrical contact may be configured to disconnect from both contacts of the pair of electrical contacts when the first part is connected to the second part and the internal pressure is at the second level. The first part may comprise a plunger displaceable between the extended position and a retracted position, the plunger having a first surface comprising said first electrical contact and a second surface comprising a pick-up electrical contact, the first part further comprising at least one spring loaded electrical contact bearing against, and in electrical connection with, the pick-up electrical contact. The first part may comprise a plunger displaceable between the extended position and a retracted position, the plunger having a first surface comprising said pair of electrical contacts and a second surface comprising a corresponding pair of pick-up electrical contacts, the first part further comprising a pair of spring loaded electrical contacts respectively bearing against, and in electrical connection with, the pair of pick-up electrical contacts. The second electrical contact may comprise a conductive ring extending around the plunger axis. The first part housing and the second part housing may each further comprise an additional contact, the additional contacts being configured to make electrical contact with one another when the first part housing and the second part housing are coupled together. The first part may be mounted in a fuel cartridge controller. The second part may be mounted in a fuel cartridge. The first part may be mounted in a fluid fuel supply module and the second part may be mounted in a fuel cartridge.

According to another aspect, the present invention provides a pressure vessel with a pressure switch comprising: a diaphragm extendable between a retracted position and an extended position as a function of internal pressure within a chamber within the pressure vessel, an electrical contact configured to make electrical connection with an external electrical contact of an external device when the pressure vessel is connected to the external device and the internal pressure is at a first level, and a plunger, displaceable by the diaphragm, configured to displace the external contact of the external device from the electrical contact when the pressure vessel is connected to the external device and the internal pressure is at a second level.

The electrical contact may be configured to make electrical connection to a pair of external electrical contacts of the external device when the pressure vessel is connected to the external device and the internal pressure is at the first level. The electrical contact may be configured to disconnect from both contacts of the pair of external contacts when the pressure vessel is connected to the external device and the internal pressure is at the second level. The electrical contact may comprise a conductive ring extending around the plunger axis. The pressure vessel housing may comprise an additional contact, the additional contact being configured to make electrical contact with a corresponding additional contact on the external device when the pressure vessel and the external device are coupled together. The pressure vessel may comprise a fuel cartridge.

According to another aspect, the present invention provides a method of controlling activation of a fuel cartridge by a controller comprising: connecting the fuel cartridge to a controller; biasing a first electrical contact on the controller towards an extended position to be in electrical contact with a second electrical contact on the fuel cartridge; providing a diaphragm on the fuel cartridge extendable between a retracted position and an extended position as a function of internal pressure within a chamber within the fuel cartridge, using a plunger, displaceable by the diaphragm, to (i) displace the first contact from the second contact when the diaphragm is in the extended position and (ii) allow the first contact to touch the second contact when the diaphragm is in the retracted position.

The method may include using displacement (i) to indicate an overpressure condition and thereby deactivate the fuel cartridge, and using displacement (ii) to indicate a normal pressure condition and thereby activate the fuel cartridge.

According to another aspect, the present invention provides a fuel supply cartridge comprising a control module and a detachable reaction chamber module configured to engage with the control module, the control module comprising the first part of the pressure-sensing switch described above and the reaction chamber module comprising the second part of the pressure-sensing switch described above.

The fuel supply cartridge may include a pump configured to pump reactant fluid to the reaction chamber, the pump being disabled by the pressure-sensing switch when the reaction chamber module is disconnected from the control module and when the reaction chamber is in an overpressure condition.

Embodiments of the present invention will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 shows a cross-sectional side view of a pressure-sensing switch installed within a pressure vessel and a controller module; Figures 2 to 4 show cross-sectional side views of the pressure sensing switch of figure 1 in three different configurations during operation; Figure 5 shows a schematic view of a fuel supply cartridge and a controller incorporating the pressure-sensing switch of figure 1.

Throughout the present specification, any descriptors relating to relative orientation and position, such as "top", "bottom", "horizontal", "vertical", "left", "right", "up", "down", "front", "back", as well as any adjective and adverb derivatives thereof, are used in the sense of the orientation of component parts as presented in the drawings. However, such descriptors are not intended to be in any way limiting to an intended use of the described or claimed invention.

With reference to figure 1 there is shown a pressure-sensing switch 1 suitable for electrically connecting and disconnecting a circuit dependent on the pressure sensed in a pressure vessel 2. The pressure vessel 2 includes a housing 13 within which is a pressure chamber 3. The pressure chamber 3 may contain any suitable pressurised fluid 4 such as hydrogen gas suitable for powering electrochemical fuel cells. The pressure vessel may be a refill cartridge. The pressure vessel 2 includes a diaphragm 5 mounted within a supporting structure 6. The supporting structure 6 includes fluid communication channels or ports 8 which communicate pressure in the pressure chamber 3 to an internal surface 9 of the diaphragm 5. The diaphragm 5 is flexible and responds to increasing and decreasing pressure within the chamber 3 by, respectively, upward and downward motion as viewed in figure 1. The diaphragm 5 includes a plunger 7 mounted on the diaphragm which extends from an external surface 10 of the diaphragm 5. The supporting structure 6 further includes an aperture 11 surrounded by an electrically conductive ring 12.

The pressure vessel 2 is connectable to a controller 20 having a housing 21 and a plunger 22 axially displaceable within the housing 21 between an extended position and a retracted position as indicated by the arrow 23. The plunger 22 comprises a pair of electrical contacts 24, 25 each of which is coupled to control circuitry on a printed circuit board 125 by way of electrical paths 26, 27 through the plunger 22 to a pair of pick-up electrical contacts 28, 29 which are in electrical communication with a corresponding pair of spring loaded electrical contacts 30, 31 on the printed circuit board 125. The spring loaded contacts 30, 31 are arranged to bias the plunger 22 to its extended (downward) position in which a plunger shoulder stop 32 bears against housing 21. The spring loaded contacts 30, 31 maintain electrical contact with the plunger 22 in both extended (downward) and retracted (upward) positions.

Operation of the pressure-sensing switch 1 is now described with reference to figures 2 to 10 4.

Figure 2 shows the pressure vessel housing 13 and the controller housing 21 disconnected from one another. In this disconnected configuration, the plunger 22 is in its extended position, and the diaphragm 5 and diaphragm plunger 7 are in an axial position determined by the pressure of fluid 4 within the chamber 3. This configuration corresponds to a switched-off configuration as indicated, with no electrical continuity between the contacts 30, 31.

Figure 3 shows a first (normal) connected configuration in which the pressure vessel housing 13 and the controller housing 21 have been connected together using an appropriate engagement mechanism, not shown. The engagement mechanism could be any suitable mechanical or magnetic latching mechanism. In this connected configuration, the plunger 22 is generally in an extended (downward) position and the diaphragm 5 and diaphragm plunger 7 are in a generally retracted (downward) position corresponding to a low or normal pressure condition of the fluid 4 within the chamber 3. In this configuration, the electrical contacts 24, 25 bear against the electrically conductive ring 12 which completes an electrical circuit between spring loaded contacts 30 and 31 via the electrical paths 26, 27 and the pick-up electrical contacts 28, 29. Although the plunger 22 is in an extended position, preferably the shoulder stop 32 may be slightly lifted from the housing 21 using a small amount of travel against the bias of the spring loaded contacts 30, 31 to ensure good electrical contact is maintained and to accommodate minor tolerances in the engagement mechanism coupling the vessel housing 13 and the controller housing 21. Completion of the electrical circuit as described may signal to the controller 20 that the pressure vessel is connected and at normal pressure levels. This configuration corresponds to a 'switched-on' configuration as indicated, with electrical continuity between the contacts 30, 31.

Figure 4 shows a second (overpressure) connected configuration in which the pressure vessel housing 13 and the controller housing 21 are connected together using the engagement mechanism, but in this configuration, the pressure vessel pressure chamber 3 has an overpressure condition of fluid 4 causing the diaphragm 5 to be in an extended position (e.g. upwards as shown in figure 4) such that the diaphragm plunger 7 bears against the plunger 22 thereby forcing the plunger 22 to a retracted (upward) position and lifting the electrical contacts 24, 25 from the conductive ring 12. This action breaks electrical continuity between the first and second spring loaded contacts 30, 31. Breaking this electrical continuity (indicated as 'switched-off condition) may signal to the controller that the pressure vessel is overpressure, or may signal to the controller that the pressure vessel is disconnected or overpressure. In either case, this may be sufficient to indicate that the pressure vessel may be deactivated.

Thus, in a general aspect, the pressure-sensing switch of figures 1 to 4 exemplifies an apparatus having a first electrical contact 24 on a first part such as housing 21 and a second electrical contact 12 on a second part such as housing 13 in which the first and second electrical contacts make an electrical connection when the first part is connected to the second part and when an internal pressure in the second part is at a first level. In a further general aspect exemplified by the pressure-sensing switch, a plunger 22 is displaceable by a diaphragm 5 so as to displace the first contact 24 from the second contact 12 when the first part is connected to the second part and the internal pressure within the second part, communicated to the diaphragm, is at a second level. The first level may be a normal pressure level and the second level may be an overpressure level.

Numerous modifications may be made to various aspects of the pressure-sensing switch described above.

In the preferred arrangement of figures 1 to 4, two electrical contacts 24, 25 with respective electrical paths 26, 27 and pick-up contacts 28, 29 are provided on the moveable plunger 22, so that an electrical continuity loop can be established using a single conductive ring 12. Alternatively, a single electrical contact (e.g. 24) and electrical path (e.g. 26) and pick-up contact (e.g. 28) could be provided on the plunger 22 and a second electrical path provided by a direct electrical connection provided between the two housings 13, 21 (i.e. not on the plunger 22). In this way, electrical continuity can still be used to signal the presence of a pressure vessel at normal pressure with the electrical continuity being broken when there is an overpressure condition. The direct electrical connection between the two housings 13, 21 could be by way of an additional contact on each of the housings.

The diaphragm 5 may comprise any member or device which communicates a change in pressure inside the pressure chamber 3 by way of a physical displacement of an outer surface 10 which can be used to displace a plunger 22 in the controller 20. The diaphragm plunger 7 may form an integral part of the diaphragm 5 or may be a separate element mounted to or coupled to the diaphragm 5.

Although the preferred embodiment described in connection with figures 1 to 4 deploys a conductive ring 12 to provide the electrical contacts on the pressure vessel, a different shape or even separate electrical contacts coupled to other electrical elements are possible. Use of a single conductive ring 12 around the aperture 11 through which the plungers 7 and 22 cooperate means that the pressure-sensing switch 1 can be made orientation-independent (around the axis of motion of the plungers) or at least have multiple discrete orientations of engagement around the axis of motion of the plungers.

The controller 20 generally exemplifies a device which can be coupled to a pressure vessel 2 to control that pressure vessel. The pressure-sensing switch generally comprises a first part which may reside in, or be incorporated with, a housing of the controller, for example, and a second part which may reside in, or be incorporated with, a housing of the pressure vessel, for example. The first part or the second part can be configured to be recessed within the respective housing, to protect the plunger mechanism and / or electrical contacts. It may be preferable however to recess the diaphragm part if this comprises more delicate components.

In at least one particular application, illustrated in more detail in relation to figure 5, the pressure-sensing switch 1 is incorporated into a durable part 40, for example a fluid fuel supply module, and a disposable part 41, for example a reaction chamber module.

With reference to figure 5, the pressure-sensing switch 1 may be deployed within a fluid fuel supply cartridge 60. In the particular arrangement of figure 5, the fuel supply cartridge is fabricated as a two part cartridge having a first, durable part 40, referred to as a fluid fuel supply module 61 or a control module and a second, disposable part 41, referred to as a reaction chamber module 62 or refill cartridge. The disposable part 41 is detachable from the durable part 40 and is configured to engage therewith at interface 70 when connected. The reaction chamber module 62 may include a reaction chamber 63 pre-charged with a first reactant, for example, a metal hydride (such as sodium borohydride). The reaction chamber may lie within a pressure vessel 2 as shown in figure 1. The reaction chamber module 62 may also include a reservoir 74 containing a second reactant, such as water. The fluid fuel supply module 61 may include a pump 64 and control circuitry 65 for actuating the pump. The fluid fuel supply module 61 may also include an interface 66 for coupling to a fuel cell assembly (not shown) and a fuel conduit 67 for passing fluid fuel (e.g. hydrogen) from the reaction chamber 63 to the interface 66. The control circuitry 65 may also control a valve 68 in the fuel conduit 67, and may have a control interface 69 for coupling to the fuel cell assembly.

The pump 64 may be configured to pump second reactant fluid from the reservoir 74 to the reaction chamber 63 where it reacts with the first reactant to generate hydrogen. As the hydrogen is generated, it can be delivered to a fuel cell assembly via the fuel conduit 67. The pump 64 may be used to control the fuel (e.g. hydrogen) supply rate. The pump may include a mechanical or pneumatic link 64a to the reaction chamber module 62 via interface 70 if it is desired to provide the pump 64 in the durable part 40 rather than the disposable part 41. In an alternative arrangement, the pump could be provided in the disposable part and suitable electrical connections made across the interface 70.

The flow of second reactant fluid from the reservoir 74 to the reaction chamber 63 may be controlled by monitoring the pressure in the reaction chamber 63, using a pressure transducer, not shown. However, a pressure transducer could fail in a way that might cause a system to under-read pressure, or software errors could occur. In either situation, a fuel supply cartridge could over-produce hydrogen. Overproduction may lead to a pressure relief valve (PRV) opening, so that hydrogen can be released to atmosphere.

However, it may not always be optimal to release hydrogen to atmosphere, particularly if the fuel supply cartridge is being used in a confined space or in the presence of ignition sources. Also, continuing release of hydrogen to atmosphere may consume all remaining reactants and is thus wasteful.

Thus, it may be desirable to provide a further mechanism for ensuring that, in the event of an overpressure condition, electrical power to the pump 64 is shut off, It is preferable that the pump 64 is shut off when pressure exceeds a normal working range, but before a PRV opens. This can be particularly challenging, as in some designs the PRV should open before 830 mbar gauge (mbarg), and has some tolerance associated with it. The normal operating range of the reaction chamber may be 300-500 mbarg. Therefore, both the pressure switch and the PRV would need to function within very tight tolerances. However, both space and cost are tightly constrained. The pressure-sensing switch 1 described in connection with figures 1 to 4 can be manufactured as a very compact assembly and the pressure control range can be very tightly controlled by suitable design.

In a general aspect, the pressure-sensing switches as described above provide a method for controlling a fuel cartridge 2, e.g. by activation and deactivation of the cartridge. Activation may encompass commencing pumping of a second reactant to a reaction chamber containing first reactant, thereby generating fluid fuel which increases the pressure of fluid fuel within the fuel cartridge. Deactivation may encompass ceasing pumping of the second reactant to the reaction chamber thereby preventing further reaction taking place to further build pressure of fluid fuel. The activation may commence when the controller 20 is coupled to the pressure vessel 13 by the electrical continuity established between the spring loaded electrical contacts 30, 31 via the conductive ring 12, and may be deactivated upon reaching a maximum pressure permitted by breaking the electrical continuity by way of the displacement of the diaphragm 5.

Other embodiments are intentionally within the scope of the accompanying claims.

Claims

CLAIMS1. A pressure-sensing switch comprising: a first part comprising a first electrical contact biased towards an extended position relative to a housing of the first part; a second part comprising: a diaphragm extendable between a retracted position and an extended position as a function of internal pressure within a chamber within a housing of the second part, a second electrical contact on the second part housing configured to make electrical connection with the first electrical contact when the first part is connected to the second part and when the internal pressure is at a first level, and a plunger, displaceable by the diaphragm, configured to displace the first contact from the second contact when the first part is connected to the second part and the internal pressure is at a second level.
2. The pressure-sensing switch of claim 1 in which the first electrical contact comprises a pair of electrical contacts and the second electrical contact is configured to connect the pair of electrical contacts to one another when the first part is connected to the second part and the internal pressure is at the first level.
3. The pressure-sensing switch of claim 2 in which the second electrical contact is configured to disconnect from both contacts of the pair of electrical contacts when the first part is connected to the second part and the internal pressure is at the second level.
4. The pressure-sensing switch of claim 1 in which the first part comprises a plunger displaceable between the extended position and a retracted position, the plunger having a first surface comprising said first electrical contact and a second surface comprising a pick-up electrical contact, the first part further comprising at least one spring loaded electrical contact bearing against, and in electrical connection with, the pick-up electrical contact.
5. The pressure-sensing switch of claim 2 in which the first part comprises a plunger displaceable between the extended position and a retracted position, the plunger having a first surface comprising said pair of electrical contacts and a second surface comprising a corresponding pair of pick-up electrical contacts, the first part further comprising a pair of spring loaded electrical contacts respectively bearing against, and in electrical connection with, the pair of pick-up electrical contacts.
6. The pressure-sensing switch of claim 2 in which the second electrical contact comprises a conductive ring extending around the plunger axis.
7. The pressure-sensing switch of claim 1 in which the first part housing and the second part housing each further comprise an additional contact, the additional contacts being configured to make electrical contact with one another when the first part housing and the second part housing are coupled together.
8. The pressure sensing switch of claim 1 in which the first part is mounted in a fuel cartridge controller and in which the second part is mounted in a fuel cartridge.
9. The pressure sensing switch of claim 1 in which the first part is mounted in a fluid fuel supply module and in which the second part is mounted in a fuel cartridge.
10. A pressure vessel with a pressure switch comprising: a diaphragm extendable between a retracted position and an extended position as a function of internal pressure within a chamber within the pressure vessel, an electrical contact configured to make electrical connection with an external electrical contact of an external device when the pressure vessel is connected to the external device and the internal pressure is at a first level, and a plunger, displaceable by the diaphragm, configured to displace the external contact of the external device from the electrical contact when the pressure vessel is connected to the external device and the internal pressure is at a second level.
11. The pressure vessel of claim 10 in which the electrical contact is configured to make electrical connection to a pair of external electrical contacts of the external device when the pressure vessel is connected to the external device and the internal pressure is at the first level.
12. The pressure vessel of claim 11 in which the electrical contact is configured to disconnect from both contacts of the pair of external contacts when the pressure vessel is connected to the external device and the internal pressure is at the second level.
13. The pressure vessel of claim 11 in which the electrical contact comprises a conductive ring extending around the plunger axis.
14. The pressure vessel of claim 10 in which the pressure vessel housing comprises an additional contact, the additional contact being configured to make electrical contact with a corresponding additional contact on the external device when the pressure vessel and the external device are coupled together.
15. The pressure vessel of claim 9 comprising a fuel cartridge.
16. A method of controlling activation of a fuel cartridge by a controller comprising: connecting the fuel cartridge to a controller; biasing a first electrical contact on the controller towards an extended position to be in electrical contact with a second electrical contact on the fuel cartridge; providing a diaphragm on the fuel cartridge extendable between a retracted position and an extended position as a function of internal pressure within a chamber within the fuel cartridge, using a plunger, displaceable by the diaphragm, to (i) displace the first contact from the second contact when the diaphragm is in the extended position and (ii) allow the first contact to touch the second contact when the diaphragm is in the retracted position.
17. The method of claim 16 further including using displacement (i) to indicate an overpressure condition and thereby deactivate the fuel cartridge, and using displacement (ii) to indicate a normal pressure condition and thereby activate the fuel cartridge.
18. A fuel supply cartridge comprising a control module and a detachable reaction chamber module configured to engage with the control module, the control module comprising the first part of the pressure-sensing switch of claim 1 and the reaction chamber module comprising the second part of the pressure-sensing switch of claim 1.
19. The fuel supply cartridge of claim 18 further including a pump configured to pump reactant fluid to the reaction chamber, the pump being disabled by the pressure-sensing switch when the reaction chamber module is disconnected from the control module and when the reaction chamber is in an overpressure condition.