Physical quantity measuring device

A physical-quantity-measuring device includes: an outer-case including a bottom and a cylindrical body; a synthetic-resin-made inner-case provided inside the outer-case; a detector that detects a physical quantity; a terminal base including a terminal for transmitting a signal from the detector outward; a cover covering an opening of the outer-case and being different in hardness from the inner-case; a cable whose first end is connected to the terminal; and a cylindrical-cable-drawing portion drawing a second end of the cable and projecting from a circumferential surface of the outer-case. The inner case includes: a case threaded-portion; and a terminal-base-setting portion on which the terminal base is set. The detector includes: a bottom connector connected to the bottom; and a joint attachable to a target. The cover includes: a cover body covering the terminal-base-setting portion; and a cover threaded-portion provided to the cover body and screwable with the case threaded-portion.

The entire disclosure of Japanese Patent Application No. 2018-122294 filed Jun. 27, 2018 is expressly incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a physical quantity measuring device configured to measure a pressure and other physical quantities.

BACKGROUND ART

A pressure gauge and other physical quantity measuring devices are used for measuring physical quantities such as pressure.

A physical quantity measuring device including a hermetically sealed housing has been known in order to detect, measure, manage and control processes in industrial process equipment.

A typical device in this type is exemplified by an industrial process transmitter including: a cylindrical housing body; first and second stainless-steel-made covers respectively engageable with both ends of the housing body; and a conduit and a neck provided on a circumferential surface of the housing body (Patent Literature 1: Japanese Patent No. 5716028).

In the typical device of Patent Literature 1, the housing body has a double-layered structure including: an inner cylindrical chassis made of aluminum; and a cylindrical outer plate made of stainless steel. The neck partially contains a sensor and is fixed to an attachment target of a pipe or the like through which a measurement target fluid flows, thereby supporting the rest of the industrial process transmitter except the neck. The conduit partially houses field wiring that can electrically connect a field terminal circuitry within the housing body to an external device. A cover screwed with an end of the chassis is removed. An end of the field wiring introduced from the conduit is connected to the field terminal circuitry. Subsequently, the cover is screwed with the end of the chassis.

In the typical device of Patent Literature 1, since the neck is provided on the circumferential surface of the housing body, the cover is to be removed from or attached to the housing body in a direction orthogonal to an axial direction of the neck.

In the connecting operation of the field wiring to the field terminal circuitry, when the neck is short, a pipe and the like present at a base of the neck disturb the operation.

When the neck is elongated in order to avoid the pipe and the like from disturbing the operation, the device is not stably supported.

Moreover, in the typical device of Patent Literature 1, the chassis is made of aluminum in order to provide a complicated structure, and the outer plate and the cover are made of stainless steel in order to obtain corrosion resistance. However, since all of the chassis, the outer plate and the cover are metallic, scoring may occur when the cover is screwed with the chassis, which also complicates the wiring operation.

SUMMARY OF THE INVENTION

An object of the invention is to provide a physical quantity measuring device capable of easily connecting a cable with a terminal of a terminal base.

According to an aspect of the invention, a physical quantity measuring device includes: an outer case comprising a bottom and a cylindrical body provided to a peripheral portion of the bottom; an inner case that is made of a synthetic resin and is provided inside the outer case; a detector that is provided to the bottom and configured to detect a physical quantity; a terminal base comprising a terminal configured to transmit a signal from the detector to an outside; a cover configured to cover an opening of the outer case and having a different hardness from that of the inner case; a cable having a first end connected to the terminal and a second end; and a cylindrical cable drawing portion drawing out the second end of the cable and projecting from a circumferential surface of the outer case, the inner case including: a case threaded portion; and a terminal base setting portion on which the terminal base is set, the detector including: a bottom connector connected to the bottom; and a joint attachable to an attachment target, and the cover including: a cover body configured to cover the terminal base setting portion; and a cover threaded portion provided to the cover body and configured to be screwed with the case threaded portion.

In the above aspect, while the cover is detached from the inner case, the first end of the cable is inserted into the cable drawing portion and is connected to the terminal of the terminal base. Subsequently, the cover threaded portion is screwed with the case threaded portion of the inner case. The connecting operation of the cable to the terminal thus ends.

Accordingly, since the cover is disposed opposite from the detector across the outer case and the inner case, the outer case is open to a side opposite from the attachment target when the cover is detached. Accordingly, in the connecting operation of the cable to the terminal, no obstacle (e.g., the attachment target) to the connecting operation is present around the opening of the outer case. Further, since the inner case is made of synthetic resin, the inner case can be easily formed by injection molding or the like such that the terminal base is located close to the opening of the outer case, thus allowing easy connection of the cable. Further, since the inner case having the case threaded portion is made of synthetic resin and the cover having the cover threaded portion is different in hardness from the inner case, scoring is less likely to occur when the cover is screwed with the inner case. Accordingly, since disadvantages concurring with the scoring when the cover is fastened are avoidable, the cable can be easily connected to the terminal.

In the above arrangement of the invention, the detector may be attached to the attachment target while the joint is located at a lower position and the bottom connector is located at a higher position, and the cable drawing portion may be attached to the outer case in a manner to be inclined downward from a base end to a distal end thereof.

In this arrangement, since the cable drawing portion is inclined downward toward the distal end, water is unlikely to enter the inside of the outer case from an opening at the distal end of the cable drawing portion, so that water can be prevented from entering the outer case.

In the above arrangement of the invention, the inner case and the outer case may define a space therebetween, and a seal member may be located surrounding a communication hole that communicates with the bottom connector formed on the bottom.

In this arrangement, even if water is generated due to dew condensation in the space, or even if unexpectedly entering water passes through the space to accumulate on the bottom of the outer case, since the seal member is disposed on the bottom in a manner to surround the communication hole, water can be prevented from entering the bottom connector through the communication hole.

In the above arrangement of the invention, the seal member may have an annular gasket located adjacent to the communication hole.

In this arrangement, prevention of water from entering the bottom connector can be reliably achieved with such a simple structure as the gasket.

In the above arrangement of the invention, the inner case may have a guide configured to guide a first end of the cable from an inside of the cable drawing portion to the terminal.

In this arrangement, when the cable is pushed into the inside of the inner case from the cable drawing portion, the first end of the cable is guided by the guide to be transferred to the terminal, so that the cable can be easily connected to the terminal.

In the above arrangement of the invention, the detector may include: a cylindrical case having a first end provided to the bottom connector and a second end provided to the joint; a sensor that is provided to the joint and is configured to detect a physical quantity of a measurement target fluid to be introduced from an introduction port formed on the joint; and a circuit board that is provided inside the cylindrical case and is configured to receive a detection signal from the sensor and transmit the detection signal to the terminal.

In this arrangement, the physical quantity measuring device is attached to the attachment target via the joint. In this arrangement, when the measurement target fluid is introduced to the sensor through the introduction port of the joint, the sensor detects the physical quantity of the measurement target fluid. The detection signal of the physical quantity outputted by the sensor is transmitted to the terminal through the circuit board, and then transmitted from the terminal through the cable to the outside.

Since the joint, the sensor and the circuit board are provided in the cylindrical case, the detector can be compact in size.

In the above arrangement of the invention, the outer case, the cable drawing portion and the cylindrical case may be metallic, an O-ring may be provided between the cover and the inner case, and the outer case may be welded to the cylindrical case and the outer case may be welded to the cable drawing portion.

In this arrangement, since the inside of the device is covered with the metallic components, the device has a rigid structure. Since the O-ring is provided between the cover and the inner case, the device has a water-proof structure.

Herein, the welding is exemplified by laser welding, electron beam welding, TIG (tungsten inert gas) welding, brazing and soldering.

In the above arrangement of the invention, the cover body may be connected to the cable drawing portion with a chain.

In the arrangement, since the cover body is connected to the cable drawing portion with the chain, the cover can be prevented from dropping off.

In the above arrangement of the invention, the chain includes: a chain body including a first end connected to the cable drawing portion and a second end; a first engaging portion connected to the second end of the chain body; and a ring connected to the first engaging portion, and the ring includes: an elastic arc portion that is engageable with a groove formed along a circumferential direction of the cover body; and second engaging portions that are respectively provided to open ends of the arc portion and are engageable with the first engaging portion.

In this arrangement, in order to connect the cable to the terminal, the cover is rotated in one direction to be attached to the inner case or in the reverse direction to be removed from the inner case. At this time, since the ring engaged with the first engaging portion at the second end of the chain is provided, not at the top of the cover body, but along the circumferential direction of the cover body, the cover can be held with the entire flat of a hand. Moreover, since the arc portion forming the ring remains engaged with the groove formed along the circumferential direction of the cover body, when the cover is rotated, the arc portion spins free in the groove against an elastic force, thereby reducing tangling of the chain. Accordingly, the cover can be easily attached to and removed from the inner case.

DESCRIPTION OF EMBODIMENT(S)

An exemplary embodiment of the invention will be described with reference to the attached drawings.

Structure of Physical Quantity Measuring DeviceFIGS. 1 to 3illustrate an overall structure of a physical quantity measuring device according to the exemplary embodiment.

As shown inFIGS. 1 to 3, the physical quantity measuring device includes: an outer case1; an inner case2made of a synthetic resin and provided inside the outer case1; a detector3provided to the outer case1; a terminal base4provided inside the inner case2; a cover5that covers an opening of the outer case1; a terminal6provided to the terminal base4; a cable C having a first end connected to the terminal6and a second end; and a cable drawing portion7through which the second end of the cable C is drawn out.

The physical quantity measuring device is attached to an attachment target (e.g., a pipe (not shown)) with the detector3being located lower than the cover5.

The outer case1, which is made of metal such as stainless steel, includes a bottom11and a cylindrical body12provided to an outer peripheral portion of the bottom11.

A communication hole11A is formed at the center of the bottom11. The communication hole11A communicates an inside of the inner case2with an inside of the detector3. A cord L is placed in the communication hole11A.

The cord L, which electrically connects the detector3to the terminal6, includes a connector L1at a first end thereof and electrically connected to the detector3, and a connector L2at a second end thereof and electrically connected to the terminal6.

The cylindrical body12, which is located so as to be substantially coaxial with upper and lower components, includes a cylindrical base end portion121integrally formed with the bottom11, and a distal end portion122integrally formed with an open end of the base end portion121.

The base end portion121has at least one inclined portion121B that is inclined such that the base end portion121has a larger bore at a remoter position from the bottom11.

Two inclined portions121B are respectively provided at both sides of the axis of the outer case1. The first one of the inclined portions121B has an attachment hole121A (seeFIG. 4) in which a base end of the cable drawing portion7is fitted. The cable drawing portion7, which is made of metal such as stainless steel, is bonded to the base end portion121by welding such as laser welding, electron beam welding, TIG (tungsten inert gas) welding, brazing and soldering.

The cable drawing portion7has a base71dented toward a base end thereof, and a distal end portion72integrally formed with the base71and having an axially constant profile.

A grounding joint123is provided to the second one of the inclined portions121B. The grounding joint123is used for grounding the detector3.

FIG. 4is a cross-sectional view of the physical quantity measuring device. As shown inFIGS. 1, 3 and 4, the inner case2includes a case body21, a case threaded portion22that is formed on an upper end of the case body21, and a terminal base setting portion23integrally formed with an inner circumferential surface of the case body21.

The case body21has a step21A formed close to the case threaded portion22along an outer circumference of the case body21. An O-ring01is interposed between a lower side of the step21A of the case body21and an inner circumferential portion of the cylindrical body12. The O-ring01blocks water from entering the bottom of the outer case1through between the open ends of the outer case1and the inner case2.

An opening21B is formed on a circumferential surface of the case body21at a position corresponding to the base end of the cable drawing portion7.

A space S is defined between the case body21and the cylindrical body12.

The case threaded portion22is in a form of an external thread.

The terminal base setting portion23, on which the terminal base4is set, includes: a supporting portion231whose lower end is supported by the bottom11; and a guide232integrally formed with the supporting portion231.

The supporting portion231includes: a plate231A; and a plurality of cylindrical ribs231B provided to a lower side of the plate231A.

The plate231A is attached to an attachment portion110formed on the bottom11using at least one bolt B.

A vent seal26that allows a flow of air and blocks a flow of water between spaces above and below the plate231A is provided at an end of at least one of the plurality of ribs231B. A stud (not shown) is provided to each of the rest of the ribs231B (seeFIG. 5).

A seal member25is disposed between the plate231A and the bottom11in a manner to surround an open communication hole11A.

The seal member25is provided with an annular gasket251as shown inFIG. 5.

The gasket251blocks water from entering a bottom connector32(described later) even if water is generated due to dew condensation in the space S between an outer circumferential surface of the case body21and an inner circumferential surface of the cylindrical body12.

The gasket251includes: rings252respectively surrounding the circumference of the plurality of ribs231B; and a connecting portion253connecting the rings252to each other.

As shown inFIGS. 1, 3 and 4, the terminal base4includes: a plate41supported by the supporting portion231; and a terminal base body42provided on the plate41.

The plate41is attached to the attachment portion110formed on the bottom11using the bolt B through the supporting portion231. The connector L2is provided to the plate41.

The terminal base body42is shaped in a step formed of a synthetic resin. The terminal6is attached to the step.

The terminal6is provided with a connector tube61, through which the terminal6and the cable C are connected to each other.

The guide232is in a form of an inclined plate for guiding the first end of the cable C to the terminal6from an inside of the cable drawing portion7. The guide232is integrally formed with an end of the plate231A. A lower end of the guide232is adjacent to a lower open edge of the cable drawing portion7.

The detector3includes: a cylindrical case31; the annular bottom connector32provided to an upper end of the cylindrical case3; a joint33provided to a lower end of the cylindrical case31; a sensor34configured to detect a physical quantity of a measurement target fluid to be introduced from an introduction port33A formed in the joint33; a circuit board35installed inside the cylindrical case31; and a holder36holding the circuit board35.

The cylindrical case31includes: a case body311; and an annular portion312provided to a lower end of the case body311.

The cylindrical case31, the bottom connector32and the joint33are made of metal such as stainless steel. Welding such as laser welding, electron beam welding, TIG (tungsten inert gas) welding, brazing and soldering is applied for bonding between the bottom11and the bottom connector32, between the bottom connector32and the cylindrical case31, and between the cylindrical case31and the joint33.

The joint33includes: a shaft331having an introduction port33A at the axial center thereof, through which the measurement target fluid is introduced; and a flange332formed to a periphery of the shaft331.

The sensor34includes: a diaphragm341displaceable depending on a pressure of the measurement target fluid; and a cylindrical portion342bonded to a peripheral portion of the diaphragm341. A strain gauge (not shown) is provided on a surface of the diaphragm341. A detection signal detected by the strain gauge is transmitted to the circuit board35.

The circuit board35includes one or two substrate body (bodies)351and an electronic component (not shown) provided to the substrate body351. The connector L1is provided to the substrate body351. With this arrangement, the detection signal of the pressure detected by the sensor34is transmitted to the terminal6through the circuit board35, the connector L1, the cord L and the connector L2.

The holder36is in a form of a synthetic-resin-made member holding both sides of the circuit board35with a predetermined elastic force, and is housed inside the case body311.

The holder36has a locking member (not shown) for locking the circuit board35therein.

A lower end portion of the holder36is supported by the annular portion312.

The cover5includes: a cover body51that is circular in a plan view and covers the terminal base4; a cover threaded portion52provided to a peripheral edge of the cover body51; and a cover end53provided to the cover5to be located closer to an open end of the cover5than the threaded portion52is located. The cover5is formed of a material such as metal, synthetic resin and ceramics. A hardness of the cover5is higher than that of the inner case2.

The cover threaded portion52is in a form of an internal thread screwable with the case threaded portion22.

A top of the cover body51projects upward. The top may be flat. The cover body51may be in any size. For instance, the cover body51may be in size enough for the top to be covered with the flat of a hand. An O-ring O2 is provided between an inner circumferential portion of the cover end53and the case body21of the inner case2.

The cover body51is connected to the cable drawing portion7with a chain8.

The chain8includes: an annular engagement portion81whose first end is engaged with a base end of the cable drawing portion7; a chain body82whose first end is connected to the annular engagement portion81; a first engaging portion83connected to a second end of the chain body82; and a ring84connected to the first engaging portion83.

The chain body82is formed by mutually connecting a plurality of spherical bodies in a line. The spherical body positioned at a first end of the chain body82is held by a holder82A and the spherical body positioned at a second end thereof is held by a holder82B. The holder82A is connected to the annular engagement portion81through an engaging ring82C.

The first engaging portion83is engaged with the holder82B. The first engaging portion83is in a form of a spiral roll of a single elastic wire, in which axially adjacent parts of the first engaging portion83are placed one upon another. The engaging ring82C may be formed in the same manner as the first engaging portion83.

The ring84includes: an elastic arc portion85that is engageable with a groove51A formed along a circumferential direction of the cover body51; and second engaging portions86that are respectively provided to open ends of the arc portion85and are engageable with the first engaging portion83. The ring84is formed by bending a single wire.

Each of the second engaging portions86includes: a linear portion861angularly formed to each of the open ends of the arc portion85; and an annular portion862integrally formed with an end of each of the linear portions861.

Two annular portions862can be placed one upon another against an elastic force of the arc portion85. The first engaging portion83is engaged with the annular portions862placed one upon another. In order to engage the first engaging portion83with the annular portions862, the annular portions862are pushed between layered parts at the end of the first engaging portion83.

Connection Method of Cable

Next, a method of connecting the cable C to the physical quantity measuring device will be described.

Firstly, the cover5is removed from the inner case2. Since the cover5removed from the inner case2has been connected to the cable drawing portion7with the chain8, the cover5will not be lost.

In this state, a first end of the cable C is pushed into the cable drawing portion7. The first end of the cable C pushed into the cable drawing portion7contacts with the guide232and is guided along an inclined surface of the guide232to a vicinity of the terminal6.

When the first end of the cableC comesto the vicinity of the terminal6, the first end of the cable C is connected to the terminal6provided to the terminal base4.

Subsequently, in order to attach the cover5to the inner case2holding the O-ring O2, the cover5is rotated clockwise while being held with the entire flat of a hand, so that the cover threaded portion52of the cover5is screwed with the case threaded portion22of the inner case2.

Although the rotation of the cover5may be restricted by the chain8whose first end is connected to the cable drawing portion7, the arc portion85of the chain8spins free in the groove51A, so that the cover5can be smoothly rotated.

For maintenance, the cover5may be rotated counterclockwise against the inner case2to be removed from the inner case2. Even when the cover5is rotated, the arc portion85of the chain8is slid in the groove51A of the cover body51, so that the chain8is less likely to be tangled with the outer case1.

The following advantages can be obtained in the exemplary embodiment.

(1) Since the cover5is disposed opposite from the detector3across the outer case1and the inner case2, the outer case1is open to a side opposite from the attachment target when the cover5is detached. Accordingly, in the connecting operation of the cable C to the terminal6, no obstacle (e.g., the attachment target) to the connecting operation is present around the opening of the outer case1, so that the cable C can be easily connected to the terminal6.
(2) Since the inner case2is made of a synthetic resin, the inner case2can be formed by injection molding or the like such that the terminal base4is located close to the opening of the outer case1, so that the terminal6is located close to the opening of the outer case1, thus also allowing easy connection of the cable C.
(3) Since the inner case2having the case threaded portion22is made of a synthetic resin and the cover5having the cover threaded portion52is made of the material harder than that of the inner case2, scoring is less likely to occur when the cover5is screwed with the inner case2. Accordingly, the cover5can be easily attached to the inner case2.
(4) Since the case threaded portion22is the external thread and the cover threaded portion52is the internal thread, the cover5covers the peripheral portion of the inner case2, so that water can be prevented from entering the inner case2through the cover5.
(5) Since the detector3is vertically located with the cover5at a higher position and the joint33at a lower position and the cable drawing portion7is attached to the outer case1in a manner to be inclined downward from the base end to a distal end of the cable drawing portion7, water is unlikely to enter the inside of the outer case1, so that water can be prevented from entering the outer case1.
(6) The space S is defined between the inner case2and the outer case1, and the seal member25is disposed between the inner case2and the bottom11in a manner to surround the communication hole11A. Accordingly, even if water is generated due to dew condensation in the space S or even if unexpectedly entering water passes through the space S to accumulate on the bottom11of the outer case1, the seal member25can prevent water from entering the bottom connector32through the communication hole11A.
(7) Since the seal member25has the annular gasket251provided adjacent to the communication hole11A, prevention of the entering of water can be reliably achieved with such a simple structure as the gasket.
(8) Since the inner case2has the guide232for guiding the first end of the cable C from the inside of the cable drawing portion7to the terminal6, when the cable C is pushed into the inside of the inner case from the cable drawing portion7, the first end of the cable C is guided by the guide232to be moved to the terminal6. Accordingly, since the first end of the cable C is located close to the terminal6, the cable C can be easily connected to the terminal6.
(9) Since the detector3includes the cylindrical case31, the sensor34provided to the joint33, and the circuit board35that is provided inside the cylindrical case31and receives the detection signal from the sensor34to transmit the detection signal to the terminal6, the detector3can be compact in size.
(10) The outer case1, the cable drawing portion7and the cylindrical case31are metallic. The outer case1is welded to cylindrical case31while the outer case1is welded to the cable drawing portion7. Accordingly, since the inside of the device is covered with the metallic components, a rigid exterior of the device is obtainble. Since the O-ring O2 is provided between the cover5and the inner case2, a water-proof structure is provided.
(11) Since the cover body51is connected to the cable drawing portion7with the chain8, the cover5can be prevented from dropping off.
(12) Since the ring84engaged with the first engaging portion83at the second end of the chain8is provided along the circumferential direction of the cover body51, the cover can be held with the entire flat of a hand. Moreover, since the arc portion85forming the ring84remains engaged with the groove51A formed along the circumferential direction of the cover body51, when the cover5is rotated, the arc portion85spins free in the groove against an elastic force, thereby reducing tangling of the chain8.
Modification(s)

It should be understood that the scope of the invention is not limited to the above-described exemplary embodiment(s) but includes modifications and improvements as long as the modifications and improvements are compatible with the invention.

Although the detector3detects a pressure in the above exemplary embodiment, for instance, the detector3according to the invention detects physical quantities (e.g., a differential pressure, a flow rate, and a temperature) other than the pressure in some embodiments.

For instance, in some embodiments, the physical quantity measuring device according to the invention is in a form of a differential-pressure measuring device in which the joint has two introduction ports individually receiving different measurement target fluids and the detector detects a pressure difference between the measurement target fluids introduced through the introduction ports and transmits the pressure difference as a detection signal to the circuit board. Alternatively, in some embodiments, the physical quantity measuring device according to the invention is in a form of a temperature measuring device in which the detector is a bimetal component that detects a temperature and transmits a temperature change as a detection signal to the circuit board.

In the above exemplary embodiment, the physical quantity measuring device is attached to the attachment target with the detector3being located lower than the cover5. However, in some embodiments, the cover5is located lower than the detector3, or the detector3and the cover5are located obliquely or horizontally.

Further, in some embodiments, the case threaded portion22is an internal thread and the cover threaded portion52is an external thread.

Moreover, it is only necessary that the cover5is different from the inner case2in hardness. In some embodiment, the hardness of the inner case2is higher than that of the cover5.

Further, the shape of the gasket251is not limited to the structure in the above exemplary embodiment. Any shape of the gasket covering the opening of the communication hole11A is applicable. For instance, in some embodiments, the gasket is a simply annular component.