UNDER HIGH ACCELERATION"

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DESCRIPTION

Technical field

The present invention relates to a system for performing shock tests, in particular under high acceleration.

Technical background

Systems are known in the art which are used for performing shock tests, in order to measure the effects of an impact on an assembly, such as a structure or an apparatus, wherein such effects are due to high acceleration caused by, for example, an explosion, a fall or a collision.

One example of such systems utilizes low-speed impacts with high acceleration, e.g. approx. lOkG, for a very short time, e.g. a time ranging from 30ps to lOOps. Typically, these system operate by dropping the assembly to be shock- tested, possibly with the aid of elastic means.

Another example of such systems utilizes a gun barrel, e.g. a cannon, for launching the assembly to be shock-tested against a surface, as if it were a bullet. In this example, such systems impart a faster speed to the assembly, and the extent of the impact can be significantly affected by the surface against which the assembly is launched; in order to mitigate the impact, soft zones are used, providing a so- called "soft recovery".

However, such systems suffer from a few drawbacks which should be remedied.

For example, in such systems the time during which the tested apparatus is subjected to acceleration is limited, and should preferably be increased.

Summary of the invention It is one obj ect of the present invention to provide an improved system which can overcome the drawbacks of the prior art .

According to the present invention, this and other obj ects are achieved through a system having the technical features set out in the appended independent claim .

Moreover, according to some advantageous embodiments of the present invention, it is possible to increase the time during which the system is subj ected to the desired acceleration, e . g . up to 10ms .

It is understood that the appended claims are an integral part of the technical teachings provided in the following detailed description of the present invention . In particular, the appended dependent claims define some preferred embodiments of the present invention that include some optional technical features .

Further features and advantages of the present invention will become apparent in light of the following detailed description, provided herein merely as a nonlimiting example and referring, in particular, to the annexed drawings as summari zed below .

Brief description of the drawings

Figure 1 is a schematic view representing a block diagram of a system made in accordance with an illustrative embodiment of the present invention . A person skilled in the art will understand that the drawings referred to herein are not drawn in scale , since the aim is merely to illustrate the principles of the present invention .

For completeness ' sake , the following is a li st o f alphanumerical references used herein to identi fy parts , elements and components illustrated in the above-summari zed drawings . 10 . System

12 . Carrier

14 . Assembly

16. Tubular guide

18 . End

20 . Other end

22 . Inner cavity

24 . Thrust tank

26. First chamber

28 . Second chamber

30 . Release device

32 . Return tank

34 . Stop device

36. Retaining element

38 . Pawl element

Detailed description of the invention

With reference to Figure 1 , 10 designates as a whole a system for performing shock tests , in particular under high acceleration . Such system is made in accordance with an illustrative embodiment of the present invention .

System 10 comprises a carrier 12 intended to house an assembly 14 to be subj ected to a shock test .

In addition, system 10 comprises a tubular guide 16 having a pair of ends 18 and 20 . Tubular guide 16 defines an inner cavity 22 through which carrier 12 is movable , in a guided manner, between ends 18 and 20 .

Furthermore , system 10 comprises a thrust tank 24 containing a pressuri zed thrust f luid and connected to inner cavity 22 in proximity to one end 18 of tubular guide 16 and in a position upstream of carrier 12 . The thrust fluid can thrust carrier 12 through tubular guide 16 towards the other end 20 . In this way, carrier 12 is subj ected to a thrust acceleration suitable for simulating the ef fects of a shock undergone by assembly 14 .

In the exemplary embodiment illustrated herein, inner cavity 22 of tubular guide 16 is divided by carrier 12 into two chambers , in particular a first chamber 26 located upstream of carrier 12 and a second chamber 28 located downstream of carrier 12 . In operation, such chambers 26 and 28 are set to di f ferent pressures , so as to generate the force necessary to accelerate carrier 12 . In particular, thrust tank 24 is connected to the first chamber 26, in which the thrust fluid flows and operates . Therefore , the first chamber 26 will tend to expand through the ef fect of the pressure of the thrust fluid exerting said thrust acceleration on carrier 12 , particularly thrusting it through tubular guide 16 away from thrust tank 24 .

In the exemplary embodiment illustrated herein, system 10 comprises a release device 30 configured for assuming a locking condition and an unlocking condition . In the locking condition, release device 30 locks carrier 12 in tubular guide 16 , in particular preventing it from moving towards the other end 20 (by countering the pressure exerted by the thrust fluid) . In the unlocking condition, release device 30 releases carrier 12 in tubular guide 16, in particular allowing it to move towards the other end 20 (without countering the pressure exerted by the thrust fluid) .

With system 10 in operation, when release device 30 i s switched from the locking condition to the unlocking condition, the pressure of the thrust fluid contained in the first chamber 24 will no longer be opposed by release device 22 . Therefore , carrier 12 can be accelerated towards the other end 20 through the e f fect of the pressure exerted thereon by the thrust fluid . In the illustrated embodiment , system 10 comprises al so a return tank 32 containing an additional pressuri zed return fluid . Return tank 32 is connected to inner cavity 22 in proximity to the other end 20 of tubular guide 16 and in a position downstream of carrier 12 . The return fluid contained in return tank 24 has a pressure which is lower than that of the thrust fluid contained in thrust tank 18 . In particular, return tank 32 is connected to the second chamber 28 , in which the return fluid flows and operates .

In operation, during an initial first phase carrier 12 , subj ected to the higher pressure of the thrust fluid contained in thrust tank 18 and acting in the first chamber 26 , is accelerated towards the other end 20 of tubular guide 16. During such initial phase , the pressure of the return fluid contained in return tank 24 and acting in the second chamber 28 will increase gradually, while the pressure of said thrust fluid will decrease accordingly . In fact , as carrier 12 moves through inner cavity 22 towards the other end 20 of tubular guide 16, the thrust fluid will expand and the pressure in the first chamber 26 will decrease , while the return fluid will be compressed and the pressure in the second chamber 28 will increase .

In a second phase , which follows the initial first phase , the pressure of the return fluid acting in the second chamber 28 exceeds the pressure o f the thrust fluid acting in the first chamber 26. Therefore, carrier 12 will be accelerated in a direction opposite to that o f the initial phase , moving towards end 18 of tubular guide 16. Carrier 12 will thus be brought again near its initial position, in proximity to end 18 .

In the illustrated embodiment , system 10 comprises al so a stop device 34 configured for stopping carrier 12 in proximity to end 18 of tubular guide 16 when it is thrust back towards end 18 . This condition occurs through the ef fect of the pressure of the return f luid downstream of carrier 12 ( in the second chamber 28 ) exceeding the pressure of the thrust fluid upstream of carrier 12 ( in the first chamber 26 ) .

Preferably, carrier 12 is a container or casing which is reclosable after having inserted assembly 14 therein .

Conveniently, the container formed by carrier 12 i s made up of a plurality of removably assemblable components . Such components can thus be reversibly disassembled .

In particular, carrier 12 is configured for sealingly enclosing assembly 14 which is intended to contain, e . g . by means of suitable sealing gaskets that are compressed between the components of carrier 12 when the latter is closed . The fluid tightness of carrier 12 i s , of course , suitable to prevent the thrust fluid and the return fluid from seeping into it .

Furthermore , carrier 12 is sealingly and slidably mounted in tubular guide 16, so as to ensure fluid separation between chambers 26 and 28 , both during a static initial phase , previous to the unlocking of device 30 , and during a dynamic phase , i . e . when sliding occurs within guide 16.

Particularly, the outer surface or geometry of carrier 12 is such that it can correctly interface with both release device 30 and stop device 34 . For example , a mechanical support or coupling is provided between mating portions of carrier 12 and of associated device ( s ) 30 and/or 34 .

Preferably, the inner surface or geometry of carrier 12 can firmly constrain assembly 14 placed therein . For example , any play or clearance between the inner surface o f carrier 12 and the outer surface of assembly 14 is avoided, whi le also dampening any vibration that may occur during use . In particular, carrier 12 may be suitably fitted with mechanical adapters to be interposed between the inner surface of carrier 12 and the outer surface of assembly 14 .

By way of example , assembly 14 may be any structure or apparatus for which it is desirable to conduct a shock test . For example , assembly 14 may include an electromechanical apparatus or device to be subj ected to said shock test . As will be apparent to a person skilled in the art , the geometry of assembly 14 advantageously permits anchoring it inside carrier 12 , e . g . by means of one or more of the abovedescribed methods ( in particular, through the use of suitable mechanical adapters ) .

Tubular guide 16 is preferably made as one piece , in particular of metallic material .

For example , the internal cross-section of tubular guide 16 advantageously has a circular shape and a substantially constant diameter throughout its length .

Furthermore , the outer shape of tubular guide 16 can be determined according to requirements concerning its mechanical strength and the interface with fastening and supporting means (not shown) to be associated therewith .

Between carrier 12 and tubular guide 16 suitable sliding blocks may be advantageously provided, configured for creating an interface that - on the one hand - reduces the friction between said carrier 12 and said tubular guide 16 during the relative sliding thereof and - on the other hand - keeps chambers 26 and 28 sealingly separate when system 10 is in operation .

Preferably, thrust tank 24 contains compressed air or nitrogen . In particular, the initial pressure of the fluid contained in thrust tank 24 may reach 200bar . For example , the volume of thrust tank 24 may amount to some tens o f litres . Advantageously, tank 24 and the first chamber 26 can communicate through a passage having a flow section substantially matching the si ze of tubular guide 16.

Release device 30 preferably comprises a retaining element 36 interposed between carrier 12 and tubular guide 16. Retaining element 36 i s so shaped as to keep carrier 12 rigidly constrained to tubular guide 16, and is configured to be breakable in at least a portion thereof , in particular such portion being mechanically weakened, so that it can break . Advantageously, release device 30 reduces any transverse stress or sticking of carrier 12 in tubular guide 16, in addition to preventing damage to carrier 12 as it is unlocked by breaking retaining element 36. By way of nonlimiting example , release device 30 comprises an actuator device or striker (not numbered) which can be operated in order to break retaining element 36. The actuator device or striker may, for example , be pneumatically operated .

Preferably, i f return tank 32 is present , it has a reduced capacity in litres . In particular, return tank 32 may contain compressed air, or nitrogen, at an initial pressure of approximately l Obar . Advantageously, but not necessarily, the interface between return tank 32 and the second chamber 28 has a flow section substantially comparable with the cross-section of guide 16.

Conveniently, one or more gasket assemblies may be provided (not shown) , housed between carrier 12 and tubular guide 16 ( or belonging to at least one of carrier 12 and tubular guide 16 ) , which permit the first chamber 26 and the second chamber 28 to be kept separate , while at the same time allowing carrier 12 to slide in tubular guide 16.

Preferably, stop device 34 comprises a pawl element 38 that , together with carrier 12 ( e . g . with a suitably shaped outer profile of the latter ) , essentially creates a unidirectional ratchet device . Pawl element 38 is , for example , constrained to tubular guide 16. Moreover, pawl element 38 is configured to prevent carrier 12 from directly moving towards end 18 while allowing carrier 12 to move towards the other end 20 . Optionally, the unidirectional ratchet device formed between pawl element 38 and carrier 12 is normally deactivated, but can be selectively activated, e . g . by bringing pawl element 38 into an active position or condition capable of interfering with the movement of carrier 12 . In particular, the unidirectional ratchet device can be fluidically activated by the pressure di f ference developing between chambers 26 and 28 as carrier 12 moves through tubular guide 16 ( in particular, when carrier 12 is released by release device 30 ) . More particularly, the unidirectional ratchet device can be activated by means of an irreversible pneumatic system .

According to some illustrative embodiments of the present invention, at least one of tubular guide 16, thrust tank 24 and return tank 32 is configured for housing or including sensors and electromechanical transducers and for interfacing with commercial pneumatic components .

Of course , without prej udice to the principle of the invention, the forms of embodiment and the implementation details may be extensively varied from those described and illustrated herein by way of non- limiting example , without however departing from the scope o f the invention as set out in the appended claims .