PNEUMATIC SENSOR

The invention belongs to physics, more precisely to measuring and in particular to measuring length by means of arrangements characterized by the use of fluids.

The purpose of the invention is to create such pneumatic sensor, which should enable measuring of each distance between the probe and a reference plane even in heavy conditions, namely even when used in such environment, where measuring by means of known devices seems to be absolutely impossible, i.e. on tool machines in the presence of impurities like fats, chips and dust, or even by increased temperature.

Various sensors are known from the prior art, which are intended for measuring i.e. detecting each distance between a probe and a reference plane. A sensor is disclosed in GB 2 149 513, which is merely intended for detecting of an object in the adjacency thereof. Such sensor generally includes a casing with an external thread, while on the end portion of said casing there is a tangential cutoff with a plane longitudinally extending surface. A reference member is mounted on said

surface, which is adapted to determine a distance up to the probe, which may be placed in adjacency thereof. Such sensor may then be mounted into appropriate device like working tool or tool machine, upon which the sensor is signaling the presence or absence of the probe, e.g. a machined semi-product or a machine part or the like. Such device may generally operate without any problem, unless the gap between said cutoff and the probe remains clean, namely without any dust, moisture or any other impurities. As soon as impurities are present in the area between the probe and the reference member, then either obtained measuring results may be irregular or also measuring as such becomes quite impossible. On such a basis such sensor is useless in heavy conditions, namely by performing of working operations on tool machines, by machining of forged parts or also in any other similar conditions.

Still further, US 4,325,249 discloses an automatic pneumatic sensor for measuring distances, which consists of e.g. cylindrical casing, in which a closed central chamber is available together with further two side chambers on the front sides, as well as of a reference member, which is inserted in said casing and displaceable in its longitudinal direction. Said reference member consists of a tube, which is embedded within the casing in both walls between the central chamber and each belonging side chamber. There is a passage within the casing intended for conducting of air from a charging connection towards corresponding passages between said chambers. Said sensor is equipped on its measuring side with a tapered conical reference member, which is disposed within a corresponding chamber on the front side of said casing and may generally be displaced along said chamber. In the opposite chamber there is a piston, which is mounted on the tubular rod and displaceable along the lastly mentioned chamber. A tapered conical reference member comprises a nozzle, which is arranged on its plane central

surface on the front side, so that the air, which is fed into the casing through the aforementioned connection, is then discharged through this nozzle. The reference member is pressed towards the probe either by means of pressure, which results from the air, which is flowing through said connection and the casing, or also by means of a spring in one of the embodiments. The pressure difference is then measured, which results from the air flow through the nozzle o the front side of the reference member and is each time depending on distance between the probe and the reference plane, which normally corresponds to the plane on the front side of the reference member. It is therefore obvious, that also in this case each presence of impurities like moisture, fats or dust in the area between the probe and the front side of the reference member may lead to irregular results, whenever such measuring is possible at all.

The present invention refers to a pneumatic sensor, which is adapted for being mounted into appropriate pneumatic circuit equipped with at least one pressure measuring device, wherein such sensor consists of a casing as well of a compressed-air charging member with at least one closing member with corresponding sealing seat, which is adapted for closing or opening of passage for conducting of compressed air.

According to the invention, said closing element with corresponding sealing seat is arranged within said passage in the interior of the closed casing, wherein said closing member is supported by a spring and is at the same time pressed against reference member, which extends coaxially with respect to said spring and partially protrudes outwards from said casing and is moreover displaceable at a pre-determined distance in its longitudinal direction. In this, said compressed-air passage is preferably formed by appropriate bore within said casing together with a

charging member inserted therein, and a blind bore, which is adapted for receipt of said spring and equipped with a conically tapered seat adapted for receiving a spherical closing member, and also by a discharging passage, by means of which the interior of the casing is connected with the exterior thereof.

A front surface, which is adapted to be pressed towards each probe, is arranged on the end portion of the reference member, which is inserted into said casing and protrudes outwards from the casing, but is at the same time sealed by means of a seal. Said passage for discharging of compressed air from the casing is preferably directed at least approximately rectangular with respect to the front surface of the reference member.

In a preferred embodiment of the invention said spring is a compression helical spring, while the closing member is an axially symmetric, preferably spherical geometric formation, which is rest against the sealing seat along its complete i.e. continuous and non-interrupted circumferential area. Said reference member consists of a guiding portion, which is tightly and longitudinally movable inserted within the guiding passage of the casing and sealed therein by means of a seal, as well as of a thickened resting portion, which is rest on the peripheral area of the operating chamber within the casing and is herewith adapted for limitation of the longitudinal movements of the reference member and at the same time also for cooperation with the closing member. In this, said casing preferably consists of two parts, which are interconnected by means of screws.

An embodiment of the invention is shown in Fig. 1 in its longitudinal cross- section.

A sensor according to Fig. 1 consists of a casing 1, within which there is a passage 2, which is intended for compressed air and is ended by a sealing seat 21. In the area of said seat 21 an elastically supported closing member 3 is foreseen, on which a reference member 4 is rest, which is movable in its longitudinal direction and tightly and sealed inserted into said casing 1.

In this particular embodiment said casing 1 consists of two parts 11, 12, which are interconnected by means of screws 13

The first part 11 of said casing 1 includes said compressed-air passage 2 and is moreover equipped with a threaded bore 20, which extends in a transversal direction with respect to said casing 1 and to which a charging member 22 for feeding the compressed air is then connected, which is sealed against the casing 1 by means of a seal 23.

Still further, said first part 11 of the casing 1 comprises a threaded anchoring bore 110, which opens outwardly and is adapted for receiving of corresponding anchoring means, e.g. bolts or the like, which then serve for the purposes anchoring of the casing 1 and herewith also the sensor in each desired place. A longitudinally extending tapered and blind bore 111 is available within said first part 11 of the casing 1, which in this particular embodiment extends coaxially with the aforementioned anchoring bore 110 and into which said compressed-air passage 2 coincides. Consequently, a compression helical spring 5 is then inserted into said blind bore 111 at the one hand, while on the another hand said conically tapered area of said blind bore 111 then also forms a sealing seat 21, on which a preferably spherical closing member 3 is rest.

The second part 12 of said casing 1 includes a longitudinal guiding passage 121, which is expanded within said casing 1 into an operating chamber 123 and which is adapted for receipt of a longitudinally movable reference member 4, which is sealed by means of a seal 122 placed in the area of said passage 121. In this particular embodiment said second part 12 of the casing 1 comprises a discharging passage 124, by means of which said chamber 123 is connected with the exterior of the casing 1 and which then in the sense of functionality forms a part of said passage 2 for conduction of the compressed air.

Said reference member 4 consists of a guiding portion 41, which is merely inserted within said guiding passage 121 while its end portion 410 together with corresponding front surface 411 protrudes outwardly from the casing 1, as well as of a thickened resting portion 42, which is adapted to be rest on the belonging wall of said chamber 123 in the peripheral area of the passage 121 and at the same time also towards said spherical closing member 3. Consequently, said reference member 4 is displaceable in its longitudinal direction and coaxially with respect to said spring 5, however just in a pre-determined and limited extent L, while on the other hand any displacement thereof also depends on loadings, namely the compression force resulting from the spring 5 and each available reference force, which is pressed towards the front surface 411 of the reference member 4.

As soon as the sensor according to the invention is anchored in a desired measuring position and appropriate compressed-air charging member 22 is attached thereto, the closing member 3 is pushed away from the seat 21 by means of the spring 5 and also the reference member 4 is pushed by means the closing member 3 into a position of maximized distance between the front surface 41 and the casing 1 (L = 0). The compressed air is charged from the charging member 22

into said passage 2, namely throughout the bore 20 and the seat 21, and is then freely flowing through the discharging passage 124 out from the casing 1.

As soon as a probe is placed adjacent to the reference member 4, the front surface 41 is rest towards the probe, by which the reference member 4 has to be moved in its longitudinal direction, so that the closing member 3 is then pushed towards the spring 5 and the seat 21. Consequently, the cross-section of passage 2 is then reduced and pressure conditions become correspondingly changed. When the presence of the probe results in the maximum movement (L) of the reference member 4, then the compressed-air passage 2 is completely closed.

Those skilled in the art should understand, that the pressure difference of the compressed air in dependence of each position of the reference member 4 i.e. of each distance (L) may also be monitored by means of including the sensor into appropriate pneumatic circuit, which also includes at least one pressure measuring means, which is not shown in the drawing. It is also obvious, that such sensor enables precisely measuring of each distance between the probe and the reference plane even in heavy conditions, e.g. on the tool machines, where impurities are present like fats, machining chips, dust, and even by increased temperature. The reason for that is the fact, that only the portion 410 of the reference member 4 together with the front surface 41 is exposed to such conditions, which protrudes outwards from the casing 1, while at the same time said compressed-air passage 2 is protected from any influences, which might result from said conditions.