GB2614961A - Blast pressure impulse gauge - Google Patents

Abstract

A gauge 10 for determining the impulse of an explosion or blast. The gauge 10 consists of a piston 15,16 inside a cylinder 13. The piston 15,16 provides a fluid-tight seal with the cylinder 13 to form an internal compression chamber 14 filled with a compression fluid 20, e.g., oil. The fluid may be a gas. The cylinder may have any cross-sectional shape, as long as the piston matches it. The compression fluid 20 acts as a pressure transfer medium and a pressure sensor 19 is in contact therewith. A pressure plate 18 can be attached (e.g., threaded) onto the closed end of the piston 16. A bleed valve 21 may allow degassing the fluid 20. An additional pressure sensor (42, Fig. 2) may be provided, embedded in the pressure plate 18. This may help identify how pressure and fragments or debris are contributing to the blast pressure impulse.

Description

BLAST PRESSURE IMPULSE GAUGE

Technical Field of the Invention

This invention relates to the field of blast pressure measurements and in particular to an improved blast pressure impulse gauge.

Background to the Invention

The requirement to accurately measure impulse pressure from both blast and debris with high repeatability exists in numerous and varied applications. Within the field of engineering there is a requirement to ensure that structures are able to withstand the forces associated with the effects of explosive blast. These buildings, building structures and materials must be rigorously tested to ensure that they meet the associated standards and requirements. This in turn requires that trials and tests are undertaken to produce a consistent blast, blast shockwave or over pressure which can be accurately measured. Typically this requires the use of specialist instruments in the vicinity of the blast such that the resultant impulse pressures can be measured. The accurate measurement of these impulse pressures is a challenge due to the forces and speeds associated with the blast waves or pressures. Furthermore blast debris or particles may also cause damage to the sensitive measurement equipment.

Therefore it is the aim of the present invention to provide a pressure impulse gauge that is able to deliver repeatable and accurate impulse pressure measurements, whilst remaining robust to blast and blast debris.

Summary of the Invention

According to a first aspect of the invention there is provided a blast pressure impulse gauge comprising an assembly of a piston and a cylinder wherein: the piston comprises a piston external end for receiving a blast pressure impulse; the cylinder comprises an open-end, a closed-end, and a peripheral wall between the ends; the piston is received into the cylinder through the open-end such that the piston external end is exposed to the exterior of the gauge, the piston being further arranged to slide within the cylinder and to provide a fluid tight seal with the peripheral wall, such that an internal compression chamber is formed between the piston, and the closed-end and peripheral wall of the cylinder; and the internal compression chamber is substantially filled with a pressure transfer medium comprising a fluid, wherein the impulse gauge further comprises: a first pressure measurement means arranged to measure a change in pressure in the pressure transfer medium; such that a blast pressure impulse applied to the piston external end can be transferred through the pressure transfer medium to the first pressure measurement means, such that the blast pressure impulse can be measured.

The requirement to measure blast impulse pressure exists in many fields where it is important to understand the forces associated with pressure exerted over time, often requiring measurements of very short duration events. These measurements may be undertaken using a variety of methods and devices however they typically rely on the use of very sensitive sensor equipment. As such these sensitive and often costly sensors may be exposed to conditions under which the sensor may be damaged, such as high pressures but also those containing fragments or dust, often traveling at high speeds or velocities. Furthermore the sensors have a predefined performance range which may not prove sufficient for the broad range of applications in which it may be used.

Blast impulse pressure is the pressure resulting from the detonation of an explosive material. The measurement of blast impulse pressures requires that the sensor systems are robust to potentially extreme environments including forces, pressures, heat and fragmentation associated with blast testing. Additionally there is a requirement to provide robust but sensitive systems.

In this context 'pressure impulse' is derived from the accepted definition for impulse (1) in that it describes how a force (F) is applied over time (t) and is defined as; J = F at Where pressure (P) is related to force (F) by; Where A is the area to which the force is being applied.

The inventor has shown that the invention advantageously allows for a configurable blast pressure impulse gauge which is robust to blast.

The blast pressure impulse gauge has a piston and cylinder assembly, these take the commonly understood meaning, wherein the piston fits inside or is conformal to and moveable within the cylinder chamber which is the internal volume defined by the cylinder casing. The term 'cylinder' in this context is not limiting to a device which is substantially cylindrical in shape, but also refers more generically to the commonly understood term associated with pressure or compression systems, which may equally be designed to be any three dimensional shape such that the shape or geometry of internal cylinder chamber or volume is matched or complimentary to the piston outer shape or geometry. Equally the 'cylinder' external shape may be entirely different to the internal chamber shape or volume. For example the cylinder body may have a square cross-sectional area with a circular internal cross sectional area, which would require a piston with a matched circular cross-sectional area. This advantageously provides significant configurability of the system to ensure it can fit or be compatible with various intended uses.

In the present invention the piston has an external end for receiving the force or pressure from for example a blast event, again this configuration is well understood within the art where the cylinder commonly has an end upon which a force acts or is applied directly or indirectly, or equally may impart a force to an external system.

The cylinder has an open-end, a closed-end, and a peripheral wall between the ends. This is typical of a cylinder, where the open-end is an aperture or opening suitable for receiving the piston of complimentary shape and size. The closed end in combination with the peripheral walls create the cylinder chamber or volume. The piston is received in the cylinder chamber or volume through the open-end of the cylinder such that the piston external end is exposed to the exterior of the gauge. In this context 'exposed' means that the end of the piston is arranged such as to receive the force or pressure from a blast or associated debris. This includes configurations where the piston external end may extend beyond or be proud of the cylinder peripheral wall or similarly may be recessed or inset compared to the cylinder open end or may equally be flush with the peripheral wall of the open end. The piston is arranged to slide or move within the cylinder, and to provide a fluid tight seal with the peripheral wall, such that an internal compression chamber is formed between the piston, and the closed-end and peripheral wall of the cylinder. The internal compression chamber is also substantially filled with a pressure transfer medium, namely a fluid, where fluid takes its normal meaning of a liquid or gas. The medium may be selected from any suitable fluid known to the art or commonly used in industrial applications, including natural or synthetic fluids suitable for the use in pneumatic or hydraulic applications. The medium is advantageously selected such that in use the transfer of pressure from the piston to the pressure transfer medium is predictable and repeatable.

Fluid tight' takes its normal meaning in that it is arranged to ensure there are no leaks or escape of fluid from the compression chamber. 'Compression chamber' is generally a well understood term, it is the volume within the chamber which when an external force is applied, or removed the pressure and or temperature of the fluid within the compression chamber will change.

The invention further comprises a first pressure measurement means arranged to measure a change in pressure in the pressure transfer medium such that a blast pressure or force applied to the piston external end can be transferred through the pressure transfer medium to the first pressure measurement means, such that the blast pressure impulse can be measured. The pressure measurement means is arranged to be in fluid connection with the pressure transfer medium, such that the pressure measurement means is in intermit contact with the pressure transfer means. In this context this means the pressure measurement means is substantially surrounded or in direct contact with the pressure transfer means.

The pressure measurement means is housed in a suitable aperture or holder. This aperture provides a channel in fluid connection between the outside of the cylinder through to compression chamber and pressure transfer medium. The aperture is typically positioned at the closed end of the cylinder facing or directed towards the cylinder open end. This channel can be varied in size or shape or both, for example for a channel with a circular cross-sectional area when viewing the invention in plan view, the diameter could be varied to accommodate pressure measurement means of differing diameters. Alternatively for a channel with a square cross-sectional area, this area could as equally be varied. Furthermore the aperture can be manufactured to receive a pressure measurement means with a plurality of fixing methods. The pressure measurement means may be held in said aperture using any known fixing method such as adhesives, fasteners, clamps or brackets, or other means such as friction fit, more preferably it may provide a complementary thread to that of the pressure measurement means such that a fluid tight seal is formed between the cylinder wall and the pressure measurement means so as to preserve the integrity of the compression chamber. In this context a fluid takes the common definition and includes liquids and gases.

The pressure measurement means may be any suitable device known to the art, for example those which convert pressure to an electrical signal, often referred to as transducers, such as the Kistler 701a piezo electric gauge which the inventor has shown to work well. The pressure measurement means may be connected to a signal recording means, comprising a system capable of receiving and recording the electrical signals from the pressure measurement means with time, such that impulse pressure can be derived. It may be any suitable system known to the art which may include a personal computer or bespoke recording hardware adapted for the purpose, such as to be able to record the signals with time at a suitable recording rate. The signals may be directly transferred to the recording means via electrical connections, alternatively the signals may be received and transmitted to the recording means via a wireless connection. The recording means may provide multiple connections, often referred to in the art as 'channels', to allow for multiple impulse pressure gauges to be connected to a single recording means. The recording means may also contain signal processing tools, such as to filter, or modify the gain of the recorded signal, which may act independently on each 'channel', further improving the versatility of the system.

The cylinder and piston should be of suitable thickness to ensure that the transfer of pressure is predictable and such that they do not deform when in use. The cylinder may be made of any suitable material which provides sufficient strength suitable for the confinement of the pressures and temperatures within the compression chamber and or the pressure transfer medium. The material selected must also be able to be manufactured to have the desired internal shape such as to form the compression chamber and aperture for holding the pressure measurement means. A typical material may be a metal or alloy for example steel, but other materials such as plastics or composites may also prove suitable. The cylinder may be formed using any known manufacturing or machining technique such as forming, milling or turning, additionally it may be formed by additive or advanced manufacturing processes. Similarly the material for the piston may be selected from any known material including a metal or alloy for example steel, but other materials such as plastics or composites may also prove suitable. The material may be selected to be the same as that of the cylinder, this advantageously provides common material properties and hence performance when in use, which further adds to the reliability of the invention.

In further embodiments of the invention the piston comprises a tube closed at the piston external end. The tube or hollow rod is manufactured or selected such that the outer surface is conformal to the internal shape of the cylinder. The external end of the tube, that which is the piston external end is closed, such as to create a hollow piston, with the open end adjacent the closed end of the cylinder. The closing may be a separate cap or closure plate, which may be fixedly attached to the rod or tube using any known fixing method suitable to the materials used, including adhesives, clasps, fasteners, friction fit or threaded means. Preferably the fixing method creates a fluid tight seal such as to prevent the leak or loss of pressure within the compression chamber. Alternatively the hollow piston may be manufactured as a single piece such that the closed end and peripheral walls create the hollow piston. Advantageously the hollow piston provides protection to the often costly pressure measurement means as there is no direct contact from the piston on to the sensor, and even if the piston should be compressed beyond its normal operating range, it would only impact the cylinder internal casing not the pressure measurement means.

The hollow piston may be manufactured using the minimal feasible amount of material such as to provide sufficient strength to withstand the expected pressures and forces when in use, but also to where used, to allow for the reliable connection of the end cap or pressure plate. Minimising the material helps to reduce cost but also advantageously allows for improved sensitivity due to the reduction in mass of the piston, which, in use, reduces the inertia of the system, thus improving the time responsiveness of the system allowing for more accurate pressure impulse measurements.

In further embodiments of the invention the pressure transfer medium is oil. Oil includes many different fluids and may be selected from any known material commonly used in the art, for example those used in hydraulic systems. This may include natural, synthetic or semisynthetic oils, which can be selected to provide a predicable performance when under pressure. Advantageously oil has been shown to provide improved performance when used with a pressure measurement means over other mediums such as air.

In further embodiments of the invention there is a bleed valve in fluid connection with the internal compression chamber. The bleed valve provides a channel from the external face of the cylinder body through to the internal volume or compression chamber. Within the channel is a sealing means configured to operate in an open position and a closed position. The sealing means may be a simple plug or threaded 'grub screw', with complementary thread within the channel, such that when removed, allows for fluid to flow between the internal volume or compression chamber and the external face. The bleed valve advantageously allows for the pressure within the compression chamber and pressure transfer medium to be controlled. For example where the medium is an oil, the cylinder, with piston in place, may have a vacuum applied to remove gas trapped in both the cylinder and oil, this advantageously improves the performance of the system.

Optionally the piston and cylinder assembly further comprises a sealing means arranged between the piston and the peripheral wall of the cylinder, thereby providing the fluid tight seal. The use of the sealing means provisions for the typical tolerances expected in the manufacture of these types of systems.

In some embodiments of the invention the sealing means comprises an 0-ring. In this context an 0-ring is a general term for a sealing ring or band to provide an improved seal and further enhance the performance of the compression chamber and may comprise one or more such 0-rings. The term 0-ring is not limited to a sealing means which is circular, and is used generically to describe a sealing ring or band which conforms to the shape of the piston outer surface and cylinder internal chamber. 0ring(s) or sealing ring(s) may be located in suitable receiving groove cut or formed on the piston surface such as to provide a tighter fitting piston which advantageously provides improved performance. Alternatively the 0-ring(s) may be located in suitable receiving groves in the internal face or bore of the cylinder. Additionally the use of the sealing ring provisions for the typical tolerances expected in the manufacture of these types of systems. The 0-ring may be of any suitable material known to the art including plastics or natural or synthetic rubbers. The material for the sealing rings is selected such as to be compatible with the pressure transfer medium, so as to not degrade, corrode or fail.

In certain embodiments, the piston external end has an attachment means for attaching a detachable pressure plate. The attachment means may be any known method or fastener including friction fit, threaded means or clasps. The detachable pressure plate provides a surface to which the blast effects may be applied when in use and advantageously allows for efficient transfer of the energy to the pressure measurement means whilst also advantageously protecting the sensitive pressure measurement means. The pressure plate may be of any suitable material able to withstand the blast pressures and associated debris which may come from a blast event, and also chosen so as to ensure reliable and consistent transfer of energy into the piston and transfer medium. The material may be selected from any known material including a metal or alloy for example steel, but other materials such as plastics or composites may also prove suitable. The material may be selected to be the same as that of the cylinder and or piston, this advantageously provides common material properties and hence performance when in use, which further adds to the reliability of the invention.

In further embodiments, the blast pressure impulse gauge comprises at least one detachable pressure plate for attaching to the piston external end using the attachment means. The pressure plate provides a blast facing surface which is robust to all aspects of the blast effects including the pressure waves but also debris or particles which may be generated. This advantageously means that the contributions of all aspects of the blast event can be measured using a single system, whilst also providing an element of the system which can easily be replaced should it become damaged or worn. The pressure plate may be of any suitable material able to withstand the blast pressures and associated debris which may come from a blast event, and also chosen so as to ensure reliable and consistent transfer of energy into the piston and transfer medium. The material may be selected from any known suitable material including a metal or alloy for example steel, but other materials such as plastics or composites may also prove suitable. The material may be selected to be the same as that of the cylinder and or piston, this advantageously provides common material properties and hence performance when in use, which further adds to the reliability of the invention.

In further embodiments the sensitivity of the system may be further adjusted by use of a plurality of detachable pressure plates each having a different blast facing cross-sectional area. This further increases the configurability of the system to be tuned or selected for the specific application due to the well understood relationship between pressure exerted, force and area. For example should an increase in sensitivity be required for a certain application the pressure plate may be selected such as to have a larger area then the external piston surface, as such for a given pressure the force through the piston is increased. Therefore it can be seen that by selecting pressure plates from a range of preselected areas the invention provides significant configurability without having to modify the pressure measurement means. This advantageously reduces the complexity and cost as the pressure measurements means is typically an expensive component.

In further embodiments of the invention the detachable pressure plate further comprises a mounting means for mounting a second pressure measurement means. This mounting means or position is an aperture into which the pressure measurement means can be inserted such that the pressure measurement means is facing the direction of the incoming blast pressure wave and is at the surface of the pressure plate. This advantageously allows for the direct and indirect blast pressure impulse to be measured. In circumstances where the blast creates both pressure and fragments or debris, it is desirable to identify how both components are contributing to the blast pressure impulse. As such the inventor has identified that the addition of a pressure measurement means in the face of the pressure plate advantageously allows for this separation to occur. This is achieved by measuring the impulse pressure at the pressure measurement means on the face of the pressure plate and that of the fragmentation and blast pressure impacting the pressure plate. These can then be compared to establish the contributions from each element. The mounting means or aperture provides a channel from the one face of the pressure plate, that furthest from the source of pressure impulse, through to the adjacent face that closest to the source of pressure impulse, and is suitable for holding a pressure measurement means. The aperture is positioned in the pressure plate such that the pressure measurement means is external of the cylinder, for example for a pressure plate with a circular cross-sectional area, when viewing the invention in a plan view, the aperture would be positioned at a radius such as to beyond the area of the piston and cylinder, so as to not interfere with normal functioning of the cylinder and piston. This channel can be varied in size or shape or both, for example for a channel with a circular cross-sectional area when viewing the invention in plan view, the diameter could be varied to accommodate pressure measurement means of differing diameters. Alternatively for a channel with a square cross-sectional area, this area could as equally be varied. Furthermore the aperture can be manufactured to receive a pressure measurement means with a plurality of fixing methods. The pressure measurement means may be held in the said aperture using any know fixing method such as adhesives, fasteners, clamps or brackets, or other means such as friction fit, more preferably it may provide a complementary thread to that of the pressure measurement means.

In a further embodiment of the invention the mounting means or positon for the second pressure measurement means is configured such as to shield the pressure measurement means from direct impact. Where pressure measurements are required close to the source of an explosion the pressure measurement means may be damaged by the associated fragmentation or debris of the blast. As such the inventor has identified that the protecting the sensor from direct impact by a shielding means allows for the continued accurate measurement but improved robustness. The 'shield' for the pressure measurement means is positioned such that the pressure waves are able to still interface with the sensor, however there is no direct route for a fragment or debris through to the pressure measurement means. The shield may be any shape, but preferably the extent of the shielding is sufficient to completely cover the cross sectional area of the pressure measurement means, or preferably provide some a wider area of cover to improve redundancy. Furthermore the shield is provided with sufficient standoff to allow for the pressure waves to interact with the pressure measurement means. This standoff may be varied depending on the application to optimise the performance. The standoff may be provided by upstands or 'legs' which fixedly attach the shield to the pressure plate. The upstands may be fixed using any known attachment method such as adhesives or threaded means, alternatively the upstands may be formed from the fixing method itself, such as a threaded bar. The 'shield' may be made of any suitable material such as metal, alloy or plastic and may be selected so as to be robust to the expected forces of the blast.

In certain embodiments of the blast pressure impulse gauge a second pressure measurement means is provided for measuring a blast overpressure. The second pressure measurement means may be located in the mounting means of the detachable faceplate, where present, or alternatively may be located separate to or outside of the impulse pressure gauge but still within the expected blast area, and directed such that the effects of the explosion or blast can be detected. For example it may be positioned in a building structure or fabric adjacent the pressure impulse gauge facing the incoming blast. This pressure measurement means may be selected to be the same or different to the first pressure measurement means, for example to provide the same or different level of sensitivity to the system. The addition of a second measurement means has advantageously been shown to provide better characterisation of the blast pressure impulse then for example a single pressure measurement means alone.

In certain embodiments of the blast pressure impulse gauge further comprises a data processing means connected to a first and second pressure measurement means, the data processing means being configured to: receive pressure measurements or signals from the first and second pressure measurement means; and then calculate from the pressure measurements, a blast pressure impulse. The data processing means is connected by any known means including wired or wireless systems such that the signal from the measurement means can be recorded locally or alternatively streamed or sent such that it can be recorded or processed in real-time, or recorded and processed at some point after the event. The processing means may be selected to have sufficient data recording and processing rate such as to measure the impulse pressure, of the blast event and may include hardware such as a personal computer, Field Programmable Gate Array (FPGA) or other bespoke hardware. The processing means may be able to have multiple inputs or channels such as to record the output from multiple blast pressure impulse gauges. The processing means may be able to perform various calculation operations on the received signals such as subtraction, addition or multiplication or equally may perform filtering or transformation operations. For example where used within the pressure impulse gauge with a first and second pressure measurement means, the signals can be filtered such that time constant or responsiveness of the first pressure measurement means can be matched to the second measurement means. Additionally the signals from the first and second measurement means can be subtracted so as to give the contribution to the impulse pressure from both components, namely the debris hitting the detachable face plate and that of the blast pressure. The addition of the processing means advantageously provides the user with a complete system configured to operate with the pressure impulse gauge providing an efficient and simple to use system.

Any feature in one aspect of the invention may be applied to any other aspects of the invention, in any appropriate combination. The invention extends to a device as herein described, with reference to the accompanying drawings.

In all aspects, the invention may comprise, consist essentially of, or consist of any feature or combination of features.

Brief Description of the Drawings

Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure la illustrates a cross-sectional view of an embodiment of the pressure impulse gauge; Figure lb illustrates an exploded view of the embodiment of Figure la.

Figure 2a illustrates a cross-sectional view of an embodiment of the blast pressure impulse gauge; Figure 2b illustrates an exploded view of the embodiment of Figure 2a.

The drawings are for illustrative purposes only and are not to scale.

Detailed Description

Figure la shows a cross-sectional view of one embodiment of the blast pressure impulse gauge 10, with a first end 11 and second end 12. The gauge comprising a rectangular cross-section cylinder 13 machined from mild steel, with an open first end 11 and a closed second end 12, and peripheral wall (22) there between, such as to form the compression chamber 14, filled with oil 20. Within the cylinder 13, there is a tube 15 with end cap 16 which together form the piston 17, which further provides confinement to the oil 20 within the compression chamber 14 when inserted in the first end 11. The tube 15 is similarly made of mild steel and has been selected such that the walls are of the minimum feasible thickness such that in use it will not deform when under pressure. The piston cap 16 has similarly been selected to minimise the weight. Attached to the piston cap 16 via threaded means (not shown) is the pressure plate 18. The pressure plate 18 is made of mild steel and the cross-sectional area has been preselected to optimise the sensitivity of the gauge. At the second end 12 the pressure measurement means 19 is shown and is fixedly attached by threaded means. Within the compression chamber 14, the oil 20 transfers the pressure from the pressure plate 18, via the piston 17 to the pressure measurement means 19. The bleed valve 21 allows for control of the internal pressure of the compression chamber. In use the gauge 10 can be subjected to a vacuum under heat to drive out gases, via the bleed valve 21, trapped within the oil 20. In use the gauge 10 can then be located adjacent the source of the pressure impulse with connections made between a signal recording apparatus and the pressure measurement means 19 such as to record pressure with time to provide impulse pressure.

Figure lb shows an exploded view of the same embodiment as Figure la of the gauge 10, showing the cylinder 13, the piston 17 and pressure plate 18 all similarly made of mild steel. At the second end 12, the pressure measurement means 19 can be seen and is fixedly attached to the cylinder 13 by threaded means (not shown). The bleed valve 21 allows for control of the internal pressure of the compression chamber.

Figure 2a shows a cross-sectional view of a second embodiment of the blast pressure impulse gauge 30, with a first end 31 and second end 32. The gauge having a cylindrical main cylinder 33 machined from mild steel such that three sides of an internal volume forming the compression chamber 34. Within the cylinder there is the hollow rod 34 with end cap 35 which together form the piston 37, which further provides confinement to the oil 40 within the compression chamber 34. The tube 35 is similarly made of mild steel and has been selected such that the walls are of the minimum feasible thickness such that in use it will not deform when under pressure. The piston cap 36 has similarly been selected to minimise the weight. Attached to the piston cap 36 via threaded means (not shown) is the pressure plate 38. The pressure plate 38 is made of mild steel and the cross-sectional area has been preselected to optimise the sensitivity of the gauge. Within the pressure plate 38 the pressure measurement means 42 is shown directed towards the source of the impulse pressure. The measurement means shield 43 is also shown and provides protection to the measurement means from the direct effects of the explosion. At the second end 32 the pressure measurement means 39 is shown and is fixedly attached by threaded means. Within the compression chamber 34, the oil 40 is shown which transfers the pressure from the pressure plate 38, via the piston 37 to the pressure measurement means 39. The bleed valve 41 allows for control of the internal pressure of the compression chamber. In use the gauge 40 can be subjected to a vacuum under heat to drive out gases via the bleed valve 41, trapped within the oil 40. The gauge 30 can then be located adjacent the source of the blast pressure impulse, within or adjacent to the material or structure to be tested, with connections made between a signal recording apparatus (not shown) and the pressure measurement means 39.

Figure 2b shows an exploded view of the same embodiment as Figure 2a of the gauge 30, showing the cylinder 33, the piston 37 and pressure plate 38 all similarly made of mild steel. Within the pressure plate 38 the pressure measurement means 42 is shown directed towards the source of the impulse pressure. The measurement means shield 43 is also shown and provides protection to the measurement means from the direct effects of the explosion. At the second end 32, the pressure measurement means 39 can be seen fixedly attached to the cylinder 33 by threaded means (not shown). The bleed valve 41 allows for control of the internal pressure of the compression chamber.

It will be understood that the present invention has been described above purely by way of example, and modification of detail can be made within the scope of the invention.

Moreover, the invention has been described with specific reference to blast pressure impulse measurements. It will be understood that this is not intended to be limiting and the invention may be used more generally. For example, the invention may be used in wider fields where there is a requirement for pressure impulse measurements, for example automotive or engineering industries more generally. Additional applications of the invention will occur to the skilled person.

Claims (13)

1. CLAIMS1. A blast pressure impulse gauge comprising an assembly of a piston and a cylinder wherein; a) the piston comprises a piston external end for receiving a blast pressure impulse; b) the cylinder comprises an open-end, a closed-end, and a peripheral wall between the ends; c) the piston is received into the cylinder through the open-end such that the piston external end is exposed to the exterior of the gauge, the piston being further arranged to slide within the cylinder and to provide a fluid tight seal with the peripheral wall, such that an internal compression chamber is formed between the piston, and the closed-end and peripheral wall of the cylinder; and d) the internal compression chamber is substantially filled with a pressure transfer medium comprising a fluid; wherein the impulse gauge further comprises: e) a first pressure measurement means arranged to measure a change in pressure in the pressure transfer medium; such that a blast pressure impulse applied to the piston external end can be transferred through the pressure transfer medium to the first pressure measurement means, such that the blast pressure impulse can be measured.
2. 2. The blast pressure impulse gauge of claim 1, wherein the piston comprises a tube closed at the piston external end.
3. 3. The blast pressure impulse gauge of any preceding claim wherein the fluid of the pressure transfer medium is an oil.
4. 4. The blast pressure impulse gauge of any preceding claim further comprising a bleed valve in fluid connection with the internal compression chamber such that the pressure of the pressure transfer medium can be controlled.
5. 5. The blast pressure impulse gauge of any preceding claim further comprising a sealing means arranged between the piston and the peripheral wall, thereby providing the fluid tight seal.
6. 6. The blast pressure impulse gauge of claim 5 wherein the sealing means comprises an 0-ring.
7. 7. The blast pressure impulse gauge of any preceding claim wherein the piston external end has an attachment means for attaching a detachable pressure plate.
8. 8. The blast pressure impulse gauge of claim 7, further comprising at least one detachable pressure plate for attaching to the piston external end using the attachment means.
9. 9. The blast pressure impulse gauge of claim 8, wherein the at least one detachable pressure plate comprises a plurality of detachable pressure plates each having a different blast facing cross-sectional area.
10. 10. The blast pressure impulse gauge of any one of claims 8-9, wherein each detachable pressure plate comprises a mounting means for mounting a second pressure measurement means.
11. 11. The blast pressure impulse gauge of claim 10 wherein the mounting means comprises a shielding means for shielding a second pressure measurement means from impact from debris.
12. 12. The blast pressure impulse gauge of any preceding claim, further comprising second pressure measurement means for measuring a blast overpressure.
13. 13. The blast pressure impulse gauge of claim 12, further comprising data processing means connected to the first and second pressure measurement means, the data processing means being configured to: a) Receive pressure measurements from the first and second pressure measurement means; and then b) Calculate from the pressure measurements, a blast pressure impulse.