WO2003034017A1

WO2003034017A1 - Pressure sensor for measuring hydraulic pressure

Info

Publication number: WO2003034017A1
Application number: PCT/EP2002/007867
Authority: WO
Inventors: Sebastian M. Mundry; Jürgen Tschöpe; Reiner Frank
Original assignee: Dbt Automation Gmbh
Priority date: 2001-10-10
Filing date: 2002-07-16
Publication date: 2003-04-24
Also published as: DE20116651U1; DE10294641D2

Abstract

The invention relates to a pressure sensor (10) which is used to measure hydraulic pressure, especially in mining hydraulics. The inventive sensor comprises a connection element (12) which can be connected to a pressure sensor connection (14) of a hydraulic device (15), and a hydroelectric pressure transducer (19) which is actuated by the hydraulic pressure on the pressure sensor connection. The aim of the invention is to prevent sudden pressure changes in the hydraulic system, in the form of pressure peaks, from having an effect on the pressure transducer and impairing the same. To this end, a pressure peak attenuating element (25) is arranged between the pressure sensor connection and the pressure transducer, said attenuating element comprising at least one throttle bore and a compensation chamber for hydraulic fluid in a preferred embodiment of the invention.

Description

Applicant: DBT Automation GmbH, Industriestrasse 1,

D-44534 Lünen Title: Pressure sensor for the measurement of hydraulic pressures

The invention relates to a pressure transducer for measuring hydraulic pressures, in particular for use in mining hydraulics, with a connecting element that can be connected to a pressure-receiving connection of a hydraulic device and a hydro-electric pressure converter that is acted upon by the hydraulic pressure present at the pressure-receiving connection.

Such pressure transducers are used to enable remote display of the pressures prevailing in hydraulic devices such as, for example, hydraulic cylinders of step extension frames in underground mining. The hydraulic fluid acts on the hydro-electric pressure transducer, which can be a metal membrane with a strain gauge arrangement. The pressure is converted into electrical measurement signals, which are then output after suitable processing and possibly forwarding to a remote display device.

Hydraulic equipment in mining in particular works at very high pressures, which can be up to 400 bar and more. In such hydraulic devices, pressure changes in the hydraulic system often occur very quickly, for example when the stamps are retracted when a removal frame is stolen and the switching valves are actuated and the check valves are unlocked for this purpose. The pressure peaks that occur in the past in the known pressure transducers have often led to damage to the pressure transducers, because these become immediate on their membrane surface acted upon directly and punctually by the high-energy hydraulic fluid.

The object of the invention is to remedy the deficiency described above and to create a pressure sensor with a longer service life and greater measuring accuracy.

This object is achieved with the invention in that a pressure peak damping element is arranged between the pressure receiving connection and the pressure transducer. The pressure peak damping element can preferably have a compensating chamber arranged between the pressure transducer and the pressure receiving connection and at least one throttle bore which connects the compensating chamber to the pressure receiving connection.

The configuration according to the invention has the advantage that the pressure peak damping element avoids a sudden increase or decrease in pressure on the hydro-electric pressure transducer, as a result of which the punctiform loads resulting from this in the past and the frequent failures in the pressure transducers attributable to this are reliably avoided.

The throttle bore can run at an angle to the longitudinal axis of the pressure transducer, for example be arranged radially, tangentially or obliquely on the connection element of the pressure transducer. A particularly advantageous embodiment of the invention, which also enables retrofitting existing pressure transducers, consists in an intermediate piece which can be mounted between the pressure receiving port and the pressure transducer and which has the connecting element which can be connected to the pressure receiving port, the throttle bore being located in the intermediate piece. Here, the compensation chamber can also be located in the intermediate piece between the throttle bore and a connection for a pressure transducer having the pressure transducer and provided with a connection element. sensor. Such a pressure sensor can be, for example, a pressure transducer used in the past without a pressure peak damping element, which was previously connected directly to the pressure receiving connection of the hydraulic device and in which the hydraulic fluid was present, ie without the interposition of a damping element on the pressure transducer. In this embodiment, the intermediate piece forms the pressure peak damping element and can be installed on the hydraulic device between the latter and the pressure receiving connection for retrofitting existing pressure sensors.

An expedient embodiment results if the intermediate piece has at least two interconnected connections and if the pressure transducer is arranged in a pressure sensor provided with a connection element and the compensation chamber is arranged in a buffer cartridge provided with a further connection element, the pressure sensor and the buffer cartridge with their Connection elements are connected to the connections of the intermediate piece. This three-part construction of the pressure sensor, consisting of a pressure sensor, buffer cartridge and intermediate piece, not only allows the pressure sensor and buffer cartridge to be replaced separately and independently of one another, for example if it is desired to provide the pressure sensor with a compensation chamber of larger or smaller volume, but also offers advantages cramped space. It can be particularly advantageous if the intermediate piece is designed as a T-piece, the buffer cartridge and the pressure sensor being arranged in alignment with one another.

As already indicated, the volume of the compensation chamber can be variable, with a volume change, for example, simply by exchanging the one having the compensation chamber Component is accessible. A particularly advantageous embodiment results when the compensation chamber is limited by a pressure compensation piston which can be spring-loaded and is expediently guided in the compensation chamber with a seal. The pressure compensation piston moves in the pressure compensation chamber in the event of a sudden pressure increase in the hydraulic system of the monitored hydraulic device and thus causes a change in volume of the compensation chamber and thus a reduction in the rate of pressure change at the pressure transducer. The pressure output piston can be loaded by a preloaded spiral spring or at least one plate spring element.

In an advantageous further development of the invention, the compensation chamber can have a conically widening chamber part which is arranged between the throttle bore and the pressure compensation piston. The pressure compensation piston is preferably designed as an annular piston and runs along a guide pin extending inside the pressure sensor. In a further embodiment of the invention, the pressure damping element can essentially be formed by an insert piece which is detachably arranged with a seal on the connection element of the pressure sensor or the intermediate piece and which is preferably screwed into the pressure sensor or the intermediate piece. With such an insert, it is possible, for example, to vary the length or the diameter of the throttle bore without having to replace other individual parts of the pressure transducer at the same time.

In particular at very high pressures or pressure fluctuations to be expected, it can be advantageous if the pressure damping element has a plurality of compensation chambers arranged one after the other, which are connected to one another or to the pressure receiving connection via throttle bores. The peak pressure Damping element is in this case designed in several stages and allows the pressure changes which occur very suddenly to act only very slowly, almost statically, on the pressure transducer. It is also possible to arrange at the inlet and / or the outlet of a throttle bore a deformation element which can move under pressure, which can consist of a circumferential, preferably elastic ring and which at least largely covers the inlet or outlet of the throttle bore in the stationary state and when suddenly occurring pressure changes slowly shifted in relation to the inlet and outlet and the throttle bore is released with a delay, so that the pressure change is noticeably slowed down until the pressure transducer becomes noticeable. The deformation element can preferably be displaceable thereon in the axial direction of the pressure transducer and, in a particularly advantageous embodiment, is arranged in a circumferential groove arranged in the region of the throttle bore, the width of which in the axial direction of the pressure transducer is greater than that of the deformation element and which expediently has a beveled groove base, which ensures that the deformation element automatically returns to its starting position, in which it covers the throttle bore, when the pressure equalization between the hydraulic system of the hydraulic device and the pressure transducer is completed.

The compensation chamber can have a constant or stepped longitudinal section and is preferably delimited on one side by a stopper having an opening, in particular a screw stopper, which makes it possible to optimally design the compensation chamber with regard to its volume and dimensions, without encountering any difficulties during manufacture bump. Further features and advantages of the invention will become apparent from the following description and the drawing, in which preferred embodiments of the invention are explained in more detail using examples. It shows:

1 shows a first embodiment of a pressure transducer according to the invention in its installed state at the pressure transducer connection of a hydraulic device in longitudinal section.

Fig. 2 shows a detail II of the pressure transducer

Figure 1 in an enlarged view in section.

3 shows a second embodiment of a pressure sensor according to the invention in a representation corresponding to FIG. 1;

Figure 4 shows a third embodiment of a pressure transducer according to the invention in section.

Fig. 5 u.

6 fourth and fifth embodiments of the pressure transducer according to the invention in the state connected to the pressure transducer connection of a hydraulic device, likewise in longitudinal section;

7 shows a sixth embodiment of the invention, partly in section; and

8 shows a seventh embodiment of the invention in a representation corresponding to FIG. 7.

The pressure transducer, designated 10 in its entirety in FIG. 1, is used in particular for measuring hydraulic pressures in mining hydraulics, for example in the system of robbery and setting punches of cramping racks or the like. The pressure transducer 10 has the shape of a slim, cylindrical cartridge and is provided on its hydraulic side 11 with a plug-in part 13, with which it engages a pressure receiving connection 14 of the hydraulic device 15 is connected and secured in a manner known per se with a fork 16. On the rear side 17 opposite the hydraulic side 11, the pressure sensor has a plug-in coupling 18 for an electrical cable (not shown).

Inside, the pressure transducer 10 is provided with a hydroelectric pressure transducer 19, on which the hydraulic fluid of the hydraulic device is present with pressure on the hydraulic side, the pressure transducer converting the hydraulic pressure into electrical measurement signals and transmitting these to the plug coupling 18 via lines 20.

As is apparent from FIG. 2, the plug part 13 forming the pressure receiving connection is provided with an axial blind hole which forms a compensation chamber 21 and which is connected to the pressure receiving connection 14 via one or more radial throttle bores 22, so that hydraulic fluid flows out of the hydraulic device can flow from the pressure receiving connection through the narrow radial bore (s) 22 into the compensation chamber 21, at the rear end of which the pressure transducer provided with a metal membrane 23 and a strain gauge arrangement 24 is located. In the event of a sudden pressure increase or pressure drop in the hydraulic system of the hydraulic device 15, this does not have an immediate or sudden effect on the pressure transducer, but rather the pressure increases (or decreases) in the compensation chamber and thus on the metal diaphragm 23 of the pressure transducer slower or gentler on (down) than in the hydraulic device itself, since the pressure change due to the narrow radial bore can only spread more slowly into the compensation chamber. Pressure peaks in the hydraulic system therefore do not affect the pressure transducer, which is therefore not damaged by sudden pressure changes in the system. The radial throttle bore 22 thus forms, together with the compensation chamber 21, a pressure peak damping element 25, which considerably extends the service life of the pressure transducer or of the pressure transducer used therein compared to the pressure transducer previously used.

In the second embodiment of the invention shown in FIG. 3, the pressure peak damping element 25 essentially consists of an intermediate piece 26 which is mounted between the pressure receiving connection 14 and the pressure transducer 19 provided on a conventional pressure sensor and which has on its front side the connection which can be connected to the pressure receiving connection 14. Element 12 has, in which the throttle bore 22, in this embodiment as an axial bore. The comparatively short throttle bore opens into an axial bore 27 which extends approximately over the length of the connecting element 12 and which in turn merges into the comparatively large-volume compensation chamber 21 with a large diameter, which is also arranged in the intermediate piece 26. At the rear end 28 of the intermediate piece 26, this is provided with a screw plug 29, which delimits the compensation chamber 21 and in which a connection 30 is provided, to which a conventional pressure sensor or sensor 10 'is secured in the usual manner with a plug-in fork and with sealing , The intermediate piece used in this embodiment therefore enables conventional pressure transducers to be retrofitted with the invention with no pressure peak damping element in order to also extend their service life. Just like the 1 and 2, the narrow throttle bore in combination with the compensation chamber prevents pressure peaks in the hydraulic system of the hydraulic device 15 from striking the pressure transducer of the pressure sensor and being able to destroy it prematurely.

The third embodiment of the invention shown in FIG. 4 shows a T-shaped intermediate piece 26 with a connecting element 12 with which it is arranged on the pressure receiving connection 14 of a hydraulic ram 15. The T-shaped intermediate piece 26 has two mutually opposite connections 30a, 30b, which are connected to one another by a longitudinal bore 31, into which a transverse bore 32 provided with a throttle bore 22 opens into the connection element. At one of the two connections 30a, a conventional pressure sensor or pressure sensor 10 'is connected under sealing, while at the other connection 30b a buffer cartridge 33 is arranged, in which the compensation chamber 21 is located, which together with the narrow throttle point 22 in the transverse bore 32 for the avoidance of pressure peaks in the pressure sensor 10 ensures. The T-shaped design of the pressure transducer ensures a construction which is only slightly protruding from the hydraulic device 15 and is therefore protected against damage. The buffer cartridge 33 can easily be exchanged for one with a larger or smaller compensation chamber in order to optimize the damping behavior of the pressure peak damping element.

The embodiments of the pressure transducer 10 according to the invention shown in FIGS. 5 and 6 are particularly compact and can therefore also be installed in confined spaces. Similar to the embodiments according to FIGS. 3 and 4, the fourth and fifth embodiment have an intermediate piece 26, which is connected at its front end with an attachment End element 12 for connection to a hydraulic device 15 and at its rear end 28 is provided with a connection 30 for a conventional pressure sensor 10 '. The compensation chamber 21 arranged in the interior of the intermediate piece 26 has a conically widening chamber part 34 and is delimited on one side by a pressure compensation piston 35 which is arranged displaceably in a cylinder bore 36 formed by the intermediate piece 26. The pressure compensation piston, which is designed as an annular piston 37, runs along a guide pin 38 which extends in the interior of the intermediate piece of the pressure sensor 10 and is sealed off from this and the cylinder bore 36 by means of sealing rings 39, 40. The piston is spring-loaded in both cases, specifically in the embodiment according to FIG. 5 by a helical compression spring 41 and in the embodiment according to FIG. 6 by a plurality of plate spring elements 42. A ventilation hole 43 on the side opposite the pressure side of the piston ensures that the force acting on the piston when the pressure conditions in the system change is completely absorbed by the spring elements 40 or 42 and not by compressed gas in the annular space receiving the spring elements. With the spring-loaded pressure compensation piston 35, the volume of the compensation chamber 21 can automatically increase or decrease in the event of pressure changes in the system and thereby compensate pressure peaks particularly well, which then have no effect on the pressure transducer and can damage it. In particular, the embodiment of the pressure transducer shown in FIG. 6 is particularly compact and is only insignificantly longer than a conventional pressure sensor that has been used to date.

A particularly simple, also very compact embodiment of a pressure sensor is shown in FIG. 7. In this case, the pressure sensor 10 is also on its front connection element 12 a screwed-in insert 44, which is sealed with an O-ring 45 with respect to the connection element and in which the throttle bore 22 is arranged coaxially to the longitudinal axis of the pressure transducer and then the graduated compensation chamber 21 is arranged. The size of the embodiment according to FIG. 7 does not differ from conventional pressure transducers and can only be distinguished from these by the additional screw part 44 and the throttle bore 22 which is narrow towards the hydraulic device. It is therefore suitable to be used as an alternative to conventional pressure transducers if the requirements are met.

A particularly sophisticated, also very compact embodiment of the pressure transducer according to the invention is shown in FIG. 8. Also in this embodiment, the pressure transducer 10 is provided on its connecting element 12 with an insert 44 ′ screwed into it, which, however, has several, when installed on the pressure receiving connection 14, successive compensation chambers 21a, b, c forms, which are connected to one another or to the pressure receiving connection 14 via a plurality of throttle bores 22a, b, c. The arrangement is such that the first throttle bore 22a opening into the pressure-receiving connection 14 runs obliquely backwards from it and opens into a circumferential groove 46 arranged on the insert 44 on the circumference, which with the cylinder wall 14 'of the pressure-receiving connection forms the first compensation chamber 21a forms. In this area, two O-rings 47, 48, of which the rear O-ring 47 lies in the groove 46 and is supported on the rear end wall 49 thereof, serve to seal the insert 44 'with respect to the pressure receiving connection 14, while the front O-ring 48 lies in a separate receiving groove 50, which is still in front of the groove 46. It can be seen that the groove 46 is of stepped design and has a front, recessed groove section 51 with a smaller diameter, in which a deformation element 52, likewise made of an elastic O-ring, is received. The width of the groove section 51 in the axial direction of the pressure sensor 10 is greater than the cross section of the deformation element 52, which can thus move back and forth in the groove section in the axial direction of the pressure sensor when it is acted upon by hydraulic fluid. The arrangement is such that the deformation element in the stationary state of the pressure transducer, in which the pressure conditions do not change or do not change appreciably, is in a lower position in which it rests on the lower end wall 53 of the groove 46 and not only that covers first, oblique throttle bore 22a, but also the second throttle bore 22b, which extends radially opposite the mouth of the first throttle bore and which connects the first compensation chamber 21a to the second compensation chamber 21b arranged concentrically inside the insert 44 '.

In the event of sudden changes in pressure in the system, these cannot have an immediate effect on the pressure transducer, since the deformation element 52 must first be moved into its upper position shown in the figure in order to release the two throttle bores 22a, b. Since the rubber-elastic deformation element 52 reacts only comparatively slowly to changes in pressure and moves relatively slowly along the groove section 51, pressure peaks in the hydraulic system cannot penetrate the pressure transducer.

A third throttle bore 22c, which connects the second compensation chamber 21b to the third compensation chamber 21c, on whose rear end face the pressure transducer is located, provides an even further improved damping. additional, Compressible rings 54 arranged in the second compensation chamber 21b serve to make the volume of the second compensation chamber 21b slightly variable and thus to further improve the damping behavior.

Claims

Expectations :

1. Pressure transducer for the measurement of hydraulic pressures, in particular for use in mining hydraulics, with a connecting element which can be connected to a pressure-receiving connection of a hydraulic device and a hydraulic-electric pressure transducer which is acted upon by the hydraulic pressure present at the pressure-receiving connection, characterized in that between the pressure receiving connection (14) and the pressure transducer (19), a pressure peak damping element (25) is arranged.

2. Pressure sensor according to claim 1, characterized in that the pressure peak damping element (25) between the pressure transducer (19) and the pressure receiving connection (14) arranged compensation chamber (21) and at least one throttle bore (22) which the compensation chamber (21) with connects the pressure receiving connection (14).

3. Druckauf ehmer according to claim 1 or 2, characterized in that the throttle bore (22) extends at an angle to the longitudinal axis of the pressure sensor (10).

4. Pressure sensor according to claim 3, characterized in that the throttle bore (22) extends radially, tangentially or obliquely to the longitudinal axis of the pressure sensor (10).

5. Pressure sensor according to one of claims 1 to 4, characterized by an intermediate piece (26) which can be mounted between the pressure receiving connection (14) and the pressure transducer (19) and which has the connecting element (12) which can be connected to the pressure receiving connection (14), the throttle bore (22) in the intermediate piece (26).

6. Pressure sensor according to claim 5, characterized in that the compensation chamber (21) in the intermediate piece (26) between the throttle bore (22) and a connection (30) for a pressure transducer (19) having a connection element (12 ') provided pressure sensor (10 ').

7. Pressure sensor according to claim 5, characterized in that the intermediate piece (26) has at least two interconnected connections (30a, b) and that the pressure transducer (19) in a pressure sensor (10 ') provided with a connection element (12') ) and the compensation chamber (21) is arranged in a buffer cartridge (33) provided with a further connection element (12 ''), the pressure sensor (10 ') and the buffer cartridge (33) with their connection elements (12', 12 '') are connected to the connections (30a, b) of the intermediate piece (26).

8. Pressure sensor according to claim 7, characterized in that the intermediate piece (26) is designed as a T-piece, the buffer cartridge (33) and the pressure sensor (10 ') being arranged in alignment with one another.

9. Pressure sensor according to one of claims 1 to 8, characterized in that the volume of the compensation chamber (21) is variable.

10. Pressure sensor according to one of claims 1 to 9, characterized in that the compensation chamber (21) is delimited by a pressure compensation piston (35).

11. Pressure sensor according to claim 10, characterized in that the pressure compensation piston (35) is spring-loaded.

12. Pressure sensor according to claim 10 or 11, characterized in that the pressure compensating piston (35) is guided displaceably under seal in the compensating chamber (21).

13. Pressure sensor according to one of claims 10 to 12, characterized in that the pressure compensation piston (35) is loaded by a prestressed coil spring (41) or at least one plate spring element (42).

14. Pressure sensor according to one of claims 1 to 13, characterized in that the compensation chamber (21) has a conically widening chamber part (34) arranged between the throttle bore (22) and the pressure compensation piston (35).

15. Pressure sensor according to one of claims 1 to 14, characterized in that the pressure compensation piston (35) is designed as an annular piston (37) and extends along an inside of the pressure sensor (10) extending guide pin (38).

16. Pressure sensor according to one of claims 1 to 15, characterized in that the pressure peak damping element (25) essentially from a sealed on the connecting element (12) of the pressure sensor (10) or the intermediate piece

(26) detachably arranged insert (44, 44 ') is formed.

17. Pressure sensor according to claim 16, characterized in that the insert (44, 44 ') in the pressure sensor (10) or the intermediate piece (26) is screwed.

18. Pressure sensor according to one of claims 1 to 17, characterized in that the pressure peak damping element (25) has a plurality of compensation chambers (21a, b, c) arranged one after the other, which with one another or with the pressure receiving connection (14) via throttle bores (22a , b, c) are connected.

19. Pressure sensor according to one of claims 1 to 18, characterized in that a throttle bore (22a, b) is arranged at the inlet and / or the outlet a pressurized deformation element (52).

20. Pressure sensor according to claim 19, characterized in that the deformation element (52) consists of a circumferential, preferably elastic ring.

21. Pressure sensor according to claim 19 or 20, characterized in that the deformation element (52) in the axial direction of the pressure sensor (10) is displaceable thereon.

22. Pressure sensor according to one of claims 19 to 21, characterized in that the deformation element (52) is arranged in a circumferential groove (51) arranged in the region of the throttle bore (22a, b), the width of which in the axial direction of the pressure sensor ( 10) is larger than that of the deformation element (52).

23. Pressure sensor according to one of claims 1 to 22, characterized in that the compensation chamber (21) has a constant or stepped longitudinal section and one-sided on a stopper (29) having an opening, in particular screw stopper, is limited.