SK279595B6 - Pressure transmitter for measuring liquid pressure - Google Patents

Abstract

A pressure transmitter, for measuring liquid pressure coming from a pressure supply, has a housing (14, 104) with an outer rim (24, 78, 142) enclosing an inner ring (36, 38, 117) of the housing (14, 104) which has an aperture (34) formed therein. The pressure transmitter further comprises a pressure transducer, positioned in the housing (14, 104) and providing pressure output, a pressure transducer whereof is connected to the aperture (34) of the housing (14, 104), and, a flange (16, 28, 122) connected to the pressure supply and pressure transducer. Said flange (16, 28, 122) is provided with an outer ring (90, 92, 140) abutting on the corresponding outer rim (24, 78, 142) of the housing (14, 104), and with an inner ring (70, 72, 149) whose position correspondents with the position of the inner ring (36, 38, 117) of the housing (14, 104). There is a recess (44, 46, 154) formed between the inner ring (70, 72, 149) of the flange (16, 28, 122) and the corresponding inner ring (36, 38, 117) of the housing (14, 104), said flange (16, 28, 122) being provided with a passage that is connected with the pressure supply at an inlet hole (62, 64) formed in the flange (16, 28, 122), and with a hole (66, 68) defined by the inner ring (70, 72, 149) of the flange (16, 28, 122). The pressure transmitter also comprises fastening means, which are connected with the flange (16, 28, 122) and flexural means represented by at least one groove (20, 94) in the housing (14, 104) between the inner ring (36, 38, 117) of the housing (14, 104) and outer rim (24, 78, 142) of the housing (14, 104), and is functionally connected between one another.

Description

The pressure transducer for measuring the pressure of the fluid coming from the pressure source comprises a body (14, 104) with an outer rim (24, 78, 142) surrounding the inner rim (36, 38, 117) of the body (14,104) formed therein. an aperture (34) further comprising a pressure transducer disposed within the body (14, 104) and providing a pressure output having a pressure transducer connected to the aperture (34) of the body (14, 104); 28, 122) connected to a pressure source and a pressure sensor, the flange (16, 28, 122) being provided with an outer rim (90, 92, 140) adjacent the corresponding outer rim (24, 78, 142) of the body (14), 104), and an inner rim (70, 72, 149) corresponding to the position of the inner rim (36, 38, 117) of the body (14, 104). A shoulder (44, 46, 154) is formed between the inner rim (70, 72, 149) of the flange (16, 28, 122) and the corresponding inner rim (36, 38, 117) of the body (14, 104) and further there is this flange (16, 28, 122) provided with a passageway connected to a pressure source at the inlet (62, 64) formed in the flange (16, 28,122), and an opening (66, 68) provided by the inner rim (70, 72,149) of the flange (16, 28). 28,122). The pressure transmitter also includes fastening means associated with the flange (16, 28, 122) and further comprises bending means formed by at least one recess (20, 94) in the body (14, 104) between the inner rim (36, 38, 117) of the body (16). 14, 104) and an outer rim (24, 78, 142) of the body (14,104) and functionally connected thereto.

Technical field

The invention relates to a pressure transmitter for measuring the pressure of a fluid coming from a pressure source.

BACKGROUND OF THE INVENTION

The need to reduce the clamping forces of the pressure transducer located within the transducer body has resulted in improvements in the transducer and their bodies and methods of applying fluid pressure to the pressure transducer. The sealed flanges supplying fluid pressure to the pressure sensor exert large clamping forces on the operator body, known as bias. These clamping forces can significantly distort the pressure sensor and cause measurement errors.

Large clamping forces are generally created by screws pressing the flanges against the body. These bolts are usually tightened to such a torque that they create a clamping force in excess of 13,040 N. This preload presses the flange to the body and ensures that the flange remains tightly connected to the separating diaphragm when connected to a high pressure source.

The pressure transducer body, flanges and screws also typically consist of a different material having a different thermal coefficient of expansion. This causes varying unequally distributed axial and radial constituents of the clamping force due to different extensibility and contraction of flanges, body and bolts over the entire temperature range.

In addition, slipping between the mating surfaces of the flange and the body can cause radial constituents of the clamping forces due to friction. These radial components have a temperature-dependent hysteresis due to slipping across the body.

Thus, it is desirable to provide a pressure transducer body that substantially reduces the transmission of large and unevenly distributed axial and radial clamping forces from the body to the pressure sensor located within the body. It is also necessary to provide a pressure transducer body that reduces the transmission of hysteresis radial clamping forces due to friction between the mating surfaces of the body and the flange due to temperature changes of the flange, the body and the screws.

SUMMARY OF THE INVENTION

The disadvantages of the prior art are largely eliminated by the solution according to the invention, which consists in that it comprises a body with an outer rim surrounding the inner rim of the body, in which an opening in the body is formed; further comprising a pressure transducer disposed within the body and providing a pressure output, wherein the pressure transducer is connected to the opening of the body; moreover, it comprises a flange connected to a pressure source and a pressure sensor, the flange being provided with a rim adjacent to the corresponding outer rim of the body and an inner rim having a position corresponding to the position of the inner rim of the body and between the inner rim of the flange and the corresponding inner rim of the body the flange is provided with a passageway connected to a pressure source at the inlet opening formed in the flange, and an opening provided by the inner rim of the flange, the opening of which is connected to a pressure source to the pressure sensor. It further comprises a seal housed in the shoulder sealing the inner rim of the body relative to the inner rim of the flange, further comprising fastening means connected to the flange to which the outer rim flanges are attached and the outer rim of the body, and further comprises bending means formed by at least one recess in the body between the inner rim of the body and the outer rim of the body and operatively connected thereto.

Furthermore, it is essential that the recess is formed because of the flexibility of the outer rim of the body around the bending regions, the recess being formed close to the outer rim of the body.

From a constructional point of view, it is advantageous that the recess is formed by at least one groove surrounding the inner rim of the body or the recess is formed by at least one notch surrounding the inner rim of the body and the seal is compliant.

It is significant from the point of view of the efficiency of the transmitter according to the invention that the outer flange of the flange surrounds the cutout in the flange.

It is essential for the broad application of the invention that it further comprises a second inner rim of the body and a second opening of the body and further comprises a first separating membrane and a second separating membrane sealed through the first opening and the second opening of the body and connected to the pressure sensor and the flange. including a second inner rim provided with a second shoulder between the second inner rim of the body and the second inner rim of the flange, the flange having a second passage connected to the first opening and the second flange bore, which are defined by the second inner rim of the flange.

It is also preferred that the bending means is further formed by at least one recess in the body surrounding both the first separating membrane and the second separating membrane, and when the surface of the outer rim of the body is larger than the surface of the first inner rim of the body.

The advantage of the invention lies mainly in the possibility of its application to reduce deformation of the pressure sensor located inside the pressure transmitter, for example differential, absolute and calibrated. Several types of pressure transducers can be used, including a strain gauge, an optical transducer, and capacitive cells with conductive plates.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of embodiments of the invention are shown in the drawings, wherein FIG. FIGS. 1A, 1B, 1C show a cross-section of a portion of a pressure transmitter according to the invention, FIG. 2 shows an exploded section of a part of the pressure transmitter, FIG. 3 is a cross-sectional view of part of the transmitter of FIG. 2 in a collapsed state, FIG. 4 is a perspective view of a portion of the transmitter of FIG. 2, FIG. 5 is an exploded view of a second embodiment of the pressure transmitter according to the invention, FIG. 6 shows a cross-section through part of the transmitter of FIG. 5 on an enlarged scale, FIG. 7 is a perspective view of part of the second embodiment.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1Λ, 1B, 1C illustrate several embodiments of a pressure transducer part, each comprising a pressure transducer 12 disposed within the transducer body 14. As described in detail below, the pressure transducer 12 converts the pressure of the fluid discharged from the flange 16 into an electrical quantity, representing pressure. An annular recess is formed in the body 14

SK 279595 Β6

20, for example a groove or notch defining the bending region 22 and the outer rim 24. By the screw 26, the flange 16 is pressed against the outer rim 24 to create a pre-load on the flange 16, generating a large axial force Fj on the outer rim 24. The body 14 comprises materials with different thermal expansion coefficients and therefore expand and contract differently depending on the temperature. This different expansion and contraction causes the axial and radial constituents of the clamping force Fj to vary and to be unequal across the body 14 over the entire temperature range. The different expansion and contraction also induces a sterile, radial component of the clamping force Fj under the effect of friction between the surface of the flange 16 sliding over the body 14, as will be described in more detail below. The outer rim 24 bends outwardly around the bending region 22, thereby reducing transmission of both axial and radial clamping force components Fj from the outer rim 24 to the pressure sensor 12 so that the electrical quantity of the pressure sensor 12 better corresponds to the actual differential pressure.

In FIG. 2, there is shown a portion of a differential pressure transmitter 10 that includes a pressure sensor 12 generally known from U.S. Patent 3,618,390. The sensor 12 is disposed within the transmitter body 14. The transducer 12 converts the differential pressure of the fluid discharged from the flanges 16 and 28 through the flexible separation membranes, the first membrane 18 and the second membrane 30, to an electrical quantity representing the differential pressure. The circuit board wiring 32 housed in the body 14 connects the electrical output to the transducer 12 with the transmitter inner circuit 10, not shown, relative to a potentially explosive atmosphere and providing a magnitude corresponding to the sensed differential pressure Pi-P2 such as DC 4 to DC. 20 mA, digital signal or 1 to 5 VDC

A pressure sensor 12 is disposed in an aperture 34 formed in the body 14. The inner rims, namely the first inner rim 36 and the second inner rim 38, surround the ring 40 and 42 of the body 14. A first shoulder 44 is formed in the ring 40 and the shoulder 40 of the body 14 is welded to the body 14 in the region 48 defined by the opening 34. The ring 42 is welded to the lid 50 in the region 52. The lid 50 is also welded to the inner rim 54 in the region 56.

The flanges 16 and 28 connect the pressure P1 and P2 by means of not shown passages from the inlet port 62 and 64 to the respective ports, to the first port 66 of the flange 16 and to the second port 68 of the flange 28. The inner rim is the first inner rim 70 and the second inner rim 72, defining the first orifice 66 and the second orifice 68, are facing the corresponding shoulders 44 and 46 to create corresponding gaps therebetween. Sealing rings 74 and 76 are disposed in the gaps to seal the fluid pressure and allow pressure Pi and P2 to be transferred from the first orifice 66 and the second orifice68 to the corresponding membranes 18 and 30. The sealing rings 74 and 76, for example O-rings, are generally flexible. a material having a substantially lower modulus of elasticity than the outer skirt 78, as discussed below.

The four fastening screws and four nuts, including the illustrated screws 26 and 80, spaced along the circumference of the flanges 16 and 28, together with the nuts 82 and 84, press the recesses 86 and 88 formed in the outer rims 90 and 92 of the flanges 16 and 28. 78, exerting a large clamping force Fj acting on the outer rims 24 and 78. The fastening screws 26 and 80 together with the nuts 82 and 84 are generally tightened to such a torque that they create a clamping force F1 of about 13 340 N, known as bias, which ensures that the flanges 16 and 28 remain connected to the body 14 even at the highest differential pressure values developed in the inlets 62 and 64. The sealing rings 74 and 76 are clamped by the inner rims 70 and 72 of the flanges 16 and 28 with a sealing force F ₂ . Because the sealing rings 74 and 76 are resilient, the sealing force F2 is substantially lower and is easier to determine in advance than the clamping force Fj and its effect on the pressure measurement can be removed by calibration.

The annular recesses 20 and 94 define the bending regions 22 and 96 in the body 14, wherein the annular recesses 20 and 94 surround the inner rims 36 and 38 just adjacent the radial edges and form narrow and ribbed outer rims 24 and 78. External rims 24 and 78 preferably, they extend beyond the planes defined by the inner ring body 36 and 38. The cross-sectional areas have been reduced by the defect areas 22 and 96 with respect to the outer flanges 24 and 78. The annular recesses 20 and 94 are sufficiently deep so that the outer flanges 24 and 78 can deflect around the bending areas 22 and 96 to substantially mechanically separate the tensities in the outer rims 24 and 78 from the inner rims 36 and 38 as well as from the sensing portions of the pressure sensor 12 including the separating membranes 18 and 30. A greater number of recesses can be provided to increase the separating effect. concentric grooves or series of grooves from one end to the other, surrounding from separating membranes 18 and 30.

There are substantially no deformations of the sensor 12 or the inner ring body 36 and 38 at the rings 40 and 42 of the body 14 connected to the separating membranes 18 and 30 as a result of the clamping force F 1. The errors caused by the clamping force Fj proportional to the pressure of the sensor 12 are substantially reduced, so that the output value of the sensor 12 better corresponds to the actual differential pressure P1-P2. Thus, the narrow bending regions 22 and 96 and the outer flanges 24 and 78 are a pressure sensor 12 substantially isolated from the clamping force F1

The carrier body 14, the flanges 16 and 28 and the screws 26 and 80 usually consist of different materials having different thermal expansion coefficients. Differences in the coefficient of thermal expansion cause the clamping forces of the four screws to change due to temperature changes of the flanges 16 and 28, the body 14 and the screws 26 and 80. Changes in the clamping force of the screws cause the clamping force Fj to change. Since the flanges 16 and 28 and the body 14 have different coefficients of thermal expansion, they also change their dimensions as a function of temperature, producing radial force components Fj in the outer flanges 24 and 78. This radial force is usually hysteresis due to friction during sliding of the abutting surfaces of the flanges 16 and 28 and the body 14.

The deformations of the pressure sensor 12 caused by the large unequal and hysteretic axial and radial clamping forces F 1 are substantially reduced by the arrangement of the outer flanges 24 and 78 that deflect around the bending regions 22 and 96 as described. Although the sealing force F2 may vary slightly with temperature, this sealing force F2 is small and has substantially no effect on the measurement of sensor 12. Pressure measurement errors by sensor 12 due to different thermal expansion of flanges 16 and 28 of body 14 and screws 26 and 80 are substantially reduced.

In FIG. 3 is a cross-sectional view of a first pressure transducer assembly in an assembled state. As already described, the flanges 16 and 28 act against the outer flanges 24 and 78 and deflect outwardly from the sensor 12. For better clarity, the deflections of the outer flanges 24 and 78 are shown in FIG. 3. As shown, the large axial as well as hysteretic radial components of the clamping force F1, varying with temperature, are substantially separated from the pressure sensor 12, thereby allowing a much more accurate pressure measurement.

In FIG. 4 is a view of a portion of the differential pressure transmitter 10. The carrier body 14 is generally cylindrical in shape with an outer rim 24, an annular recess, a bending region 22, an inner rim 36, a shoulder 44, and a separating membrane 18, and these parts are generally concentric with the body 14.

In FIG. 5, a second preferred embodiment of the differential pressure transmitter 100 is shown. A pressure sensor 102, similar to the sensor 12 described in the first preferred embodiment, is disposed within the body 104 of the transmitter 100 and senses the differential pressure P1-P2 on the transversely displaceable separating membranes, the first membrane 106 and the second membrane 108.

The electrical wiring 110 of the transmitter 100, which is sealed apart from the potentially explosive atmosphere, is coupled to the sensor 102 and provides an output representing a differential pressure Ρχ - P2 sensed by the sensor 102. Separating membranes 106 and 108 forming part of the sensor 102 seal the openings 112 and 114 the first orifice 112 and the second orifice 114 defined by the first inner rim 116 and the second inner rim 117 and lie substantially in the same plane. Channels 118 and 120 apply pressures Ρχ, P2 to sensor 102.

The flange 122 connects the pressures Ρχ, β2 through channels 124 and 126 from the inlet holes 128 and 130 to the holes 132 and 134 to the first hole 132 and the second hole 134, respectively, corresponding to the separating membranes 106 and 108. fastening screws including screws 136 and 138 which press the outer rim 140 of the flange 122 to the corresponding outer rim 142 of the body 104 and exert a clamping force Fx on the outer rim 142. Elastic or plastic sealing rings 144 and 146, for example of polytetrafluoroethylene, internal wreaths, ie. first inner rim 148 and second inner rim 149 of flange 122, and welded rings 150 and 151 as described in U.S. Patent 4,792,089. Welded rings 150 and 151 are welded to corresponding shoulders, first shoulder 152 and second shoulder. 154, which surround the separating membranes 106 and 108. The inner rims 148 and 149 of the flange 122 also create a sealing force F2, compressing the sealing rings 144 and 146 to seal the flange holes 132 and 134 with the holes 112 and 114 of the body 104.

The separate grooves 156 and 158 in the body 104 form bending regions 160 and 162 between the outer rim 142 and the inner rims 116 and 117 associated with the separating membranes 106 and 108. The grooves 156 and 158 may also overlap to form one continuous groove surrounding the two inner rows 116 and 117 or include a plurality of parallel grooves to enhance the deflection effect. The grooves 156 and 158 are sufficiently deep that the clamping force Fx deflects the outer rim 142 around the bending regions

160 and 162. Similar to that described in FIG. 1, the transmission of the large unevenly distributed axial and radial constituents of the clamping force Fx from the outer rim 142 to the inner rims 116 and 117 at the separating membranes 106 and 108 is substantially reduced, so that the deformations of the separating membranes 106 and 108 are also substantially less.

In addition, the body 104 and the flange 122 may be of different materials having a different coefficient of thermal expansion. The flange 122 slides over the temperature-varying body 104 due to the differential expansion and contraction of the body 104 and the flange 122. This sliding movement is hysteretic due to the friction between the abutting surfaces of the flange 122 and the body 104 creating a hysteresis radial component of clamping force Fx. This hysteresis radial force is substantially reduced by providing an outer rim 142 that deflects around the bending regions 160 and 162 to substantially reduce deformations of the separating membranes 106 and 108, similar to the first embodiment of the invention.

The sealing forces F2 may be great in particular when using sealing rings 144 and 146 of polytetrafluoroethylene which slightly distort the separating membranes 106 and 108. However, errors in the pressure measurements due to this deformation can be eliminated by calibration, since the inner rims 116 and 117 and the sealing rings 144 and 146 they have a substantially smaller surface than the outer rim 142 as well as because the polytetrafluoroethylene has a lubricating effect such that the hysteresis radial components of the sealing force F2 due to sliding on the flange 122 over the sealing rings 144 and 146 and the inner rims 116 and 117 are small.

In FIG. 6 is an enlarged cross-sectional view of the region 164 of FIG. 5th

Fig. 7 is a perspective view of the pressure transmitter 100. The grooves 156 and 158 are formed between the outer rim 142 and the inner rims 116 and 117, the inner rims 116 and 117 surrounding the separating membranes 106 and 108. The grooves 156 and 158 are sufficiently deep so that the outer rim 142 can be deflected around the bending areas 160 and 162 (FIGS. 5, 6) to substantially reduce the deformation of the inner rims 116 and 117 and the separating membranes 106 and 108 due to the large and unequal axial and hysteresis radial components of the clamping force Fx exerted on the outer rim 142 of the flange 122. 158 is optimal in the range of one quarter to one half of the width A shown in FIG. 7, wherein the grooves 156 and 158 surround the separation membranes 106 and 108 as much as possible.

While preferred embodiments of the invention have been described, it will be apparent to those skilled in the art that some detailed changes and some changes to the arrangement may be made within the scope of the inventive idea.

Claims (10)

A pressure transducer for measuring the pressure of a fluid coming from a pressure source, characterized in that it comprises a body (14, 104) with an outer rim (24, 78, 142) surrounding the inner rim (36, 38, 117) of the body. (14, 104), wherein an opening (34) is formed in the body (14, 104) that further comprises a pressure switch disposed in the body (14, 104) and providing a pressure output, the pressure switch being connected to the opening (34) a body (14, 104) that further comprises a flange (16, 28, 122) associated with a pressure source; and SK27959SB6 with a pressure sensor, the flange (16, 28, 122) being provided with an outer rim (90, 92, 140) adjacent to a corresponding outer rim (24, 78, 142) of the body (14, 104) and an inner rim (70, 72, 149), a position corresponding to the position of the inner rim (36, 38, 117) of the body (14, 104) and between the inner rim (70, 72, 149) of the flange (16, 28, 122) and the corresponding inner rim (36, 38) The body (14,104) is formed by a shoulder (44,46,154), and further, the flange (16, 28, 122) is provided with a passage connected to a pressure source at the inlet (62, 64) formed in the flange (16, 28,122) and with an opening (66,68) provided by the inner rim (70, 72, 149) of the flange (16, 28, 122), the opening (66, 68) communicating a pressure source to the pressure switch, further comprising a seal (74, 76) ), housed in a shoulder (44, 46, 154), sealing the inner rim (36, 38, 117) of the body (14,104) with respect to the inner rim (70, 72, 149) of the flange (16, 28, 122); The mold comprises fastening means coupled to a flange (16, 28, 122) by which the outer rims (90, 92) of the flange (16, 28, 122) and the outer rim (24, 78, 142) of the body (14) are attached. 104), and further comprising bending means formed by at least one recess (20, 94) in the body (14, 104) between the inner rim (36, 38, 117) of the body (14, 104) and the outer rim (24, 78,142) of the body (14,104) and functionally associated therewith. A pressure transmitter according to claim 1, characterized in that the recess (20, 94) is formed due to the flexibility of the outer rim (24, 78, 142) of the body (14, 104) around the bending regions (22, 96). A pressure transmitter according to claim 2, characterized in that the recess (20, 94) is formed close to the outer rim (24, 78,142) of the body (14,104). Pressure transmitter according to any one of the preceding claims, characterized in that the recess (20, 94) is formed by at least one groove surrounding the inner rim (36, 38, 117) of the body (14, 104). Pressure transmitter according to claim 3, characterized in that the recess (20, 94) is formed by at least one notch surrounding the inner rim (36, 38, 117) of the body (14, 104). A pressure transmitter according to claim 4, characterized in that the seal (74,76) is compliant. A pressure transmitter according to claim 6, characterized in that the outer rim (90, 92) of the flange (16, 28, 122) surrounds the cutout in the flange (16, 28, 122). The pressure transmitter of claim 1, wherein the body (14, 104) further comprises a second inner rim (38, 117) of the body (14, 104) and a second opening (114) of the body (14,104), and further comprising a first a separating diaphragm (18, 106) and a second separating diaphragm (30, 108) sealed through the first orifice (112) and the second orifice (114) of the body (14,104) and connected to the pressure sensor and the flange (16, 28, 122), wherein the flange (16, 28, 122) further comprises a second inner ring (72, 149) provided with a second shoulder (46, 154) between the second inner ring (38, 117) of the body (14, 104) and the second inner ring (72, 149) flanges (16, 28, 122), the flange (16, 28, 122) having a second passageway connected to the first bore (66, 132) and the second bore (68, 134) of the flange (16, 28, 122) to be provided a second inner rim (72, 149) of the flange (16, 28, 122). The pressure transmitter according to claim 8, characterized in that the bending means are further formed by at least one recess in the body (14,104) surrounding both the first separating membrane (18,106) and the second separating membrane (30, 108). The pressure transmitter of claim 9, wherein the surface of the outer rim (24, 78, 142) of the body (14,104) is larger than the surface of the first inner rim of the body (14, 104). 6 drawings SK 279595 Β6 Fig. 2 Fig. 3 SK 279595 Β6 100 i / 56 LLB-® Fig. 5 Fig. 6