CA1048296A - Measurement of the change in longitudinal force in a rail - Google Patents
Measurement of the change in longitudinal force in a railInfo
- Publication number
- CA1048296A CA1048296A CA76251412A CA251412A CA1048296A CA 1048296 A CA1048296 A CA 1048296A CA 76251412 A CA76251412 A CA 76251412A CA 251412 A CA251412 A CA 251412A CA 1048296 A CA1048296 A CA 1048296A
- Authority
- CA
- Canada
- Prior art keywords
- ring
- wire
- strain gauge
- pole piece
- rail
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/10—Measuring force or stress, in general by measuring variations of frequency of stressed vibrating elements, e.g. of stressed strings
- G01L1/106—Constructional details
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Force Measurement Appropriate To Specific Purposes (AREA)
- Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
Abstract
ABSTRACT
A vibrating wire strain gauge for enabling the in-situ measurement of the change in longitudinal force in rails is set in a hole in the rail. The strain gauge comprises a ring to which the ends of the vibrating wire are secured and an electromagnetic coil arrangement for setting the wire in vibration and then detecting the vibration frequency of the wire. The electromagnetic coil arrangement comprises an annular coil surrounding a single pole piece and extending axially of the ring towards the wire. The pole piece is connected to the ring so that the magnetic circuit is completed through the body of the ring and the wire.
A vibrating wire strain gauge for enabling the in-situ measurement of the change in longitudinal force in rails is set in a hole in the rail. The strain gauge comprises a ring to which the ends of the vibrating wire are secured and an electromagnetic coil arrangement for setting the wire in vibration and then detecting the vibration frequency of the wire. The electromagnetic coil arrangement comprises an annular coil surrounding a single pole piece and extending axially of the ring towards the wire. The pole piece is connected to the ring so that the magnetic circuit is completed through the body of the ring and the wire.
Description
~L~4~9~ .
This invcntion rela~es -to strain gauges Eor enabling the in-situ measurement of the change in lonyitudinal force in rails of railway track and in other elon~ated structural members which are subjected to longitudinal loading ~all herein referred to as "rails").
In the specification of Canadian Patent No. 975,576, issued July 10, 1975 (John Charles Luchs and George William Moreland, inventors) there is described and claimed a system for measuring the longitudinal orce in a rail comprising a strain gauge set in a hole in the rail, which hole extends depthwise transversely of the rail, the output o~ the strain gauge varying upon changes in cross-sectional shape of the hole caused by changes in longitudinal force in the rail.
The strain gauge described in ~he aforesaid specifica-tion is a vibrating wire strain gauge comprising at least one wire which extand diametrically across and is secured at its ends to a ring which conforms to the periphery of the hole in the rail and is secured around its periphery to the rail and an electro-magnetic coil arrangement supported by the ring for sPtting the wire in vibration and then detecting the vibration frequency of the wire.
The object of the present invention is to provide an advantageous electromagnetic coil arrangement for a vibrating wire strain gauge of the form described in the aforesaid speci-fication.
According to the invention the electromagnetic coil arrangement comprises an annular coil surrounding a single pole piece which extends axially of the ring towards the wire and which is connected to the ring so that magnetic circuit is com-pleted through the body of the ring and the wire.
In use of the system described in the aforesaid speci-fication the electromagnetic coil arrangement comprised a coil mounted on a pair of pole pieces which thus effectively formed 2S~
a 'U' shaped electromagnet. Hence the wire was set in-to vibra-tion by plucking it at two spaced points at for example 1/4 and 3/4 the way along the length of the wire from one end. In con-trast, with the single pole piece in accordance with the present invention, the wire is plucked at one point substantially at the mid-length of the wire. This feature together with the feature of using the ring as part of the magnetic circuit leads to the following advantages: !
i. A more efficient pluck leading to an improved characteristic for the strain gauge.
ii. The possibility of reducing the size of the electromagnetic coil arrangement so that the strain gauge can be contained whol-ly within the width of the web of a rail of railway track in order to reduce the risk of damage to it by for example track maintenance machines.
iii. Simplicity of construction and hence reduction in cost. ;
iv. Maximum use of space within the strain gauge leading to increased output and thereby reducing requirements on read-out equipment, i.e. equipment to which the electromagnetic coil arrangement is electrically connected for determining the vibration frequéncy of the wire.
Advantageously the pole piece can project from and be supported by, an end cap for the ring; for example the pole piece may be formed integral with the end cap. Thus where the strain gauge has two vibrating wires each associated with a respective magnetic coil arrangement, each pole piece can be supported by a respective end cap for the ring. The two wires may extend at .
~4~
right angles -to each o~her as described in the aforesaid speci-fication or pa.rallel to each other, in which case the ring would be set in the hole in the rail so that the wires exte.nd longitu-dinally of the rail.
In further development of the invention, the gauge can be formed in two axially separable parts, a first part carrying the wire and a second part carrying the annular coil. Thus only , said first part need by permanently installed in a rail, the second part bein~ transportable with the associated measuring instrument. This development of the invention leads to simplifi- -cation of the part of the gauge installed in the rail and there-fore reduction in its cost. In addition a much greater freedom in coil design and size is possible.
Two constructions of strain gauge in accordance with the invention will now be described by way of example with refer-ence to the accompanying drawing, in which:
Figure 1 shows a cross-section through one construction - of strain gauge, Figure 2 is a diagram of the maynetic circuit set up ~0 in the device of Figure 1, and Figure 3 is a cross-section of the second construction :`
of strain gauge.
. Referring to Figures 1 and 2, the strain gauge has a pair of parallel wires 1 and 2 extending diametrically across a ring 3 and locked to the ring at their ends by locking pins 4.
The wires 1 and 2 are associated with electromagnetic coil arran-gements 5 and 6 respectively for setting the wires 1 and 2 in vibration and for detecting the vibration frequency in the manner described in our aforesaid specification. Each electromagnetic coil arrangement comprises an annular coil 7 surrounding a pole piece 8 which extends axially of the ring 3 to a position closely adjacent its associated wire 1 and 20 The pole piece 8 projects .~ from a respective end wall of the ring 3 in the form o~ an end .. . . ~
cap 9 for the ring ', ~he end cap being secured in position by locking screws 10 which ~lso serve to hold the wire locking pins 4 in position.
In use the strain gauge can be mounted in a hole in ihe vertical web of a rail of railway track shown at 12 in Figure 1. With this parallel wire strain gauge the ring is set in the hole so that the two wires extend longitudinally of the rail.
Conveniently the outside diameter of the ring 3 corresponds to the standard fish bolt hole diameter to facilitate fitting of the strain gauge in the rail. The ring 3 is fixed around its peri-phery to the hole in the rail web so that any changes in shape of the hole will cause corresponding changes in shape of the ring and hence variation in the vibration frequency of the wires 1 and
This invcntion rela~es -to strain gauges Eor enabling the in-situ measurement of the change in lonyitudinal force in rails of railway track and in other elon~ated structural members which are subjected to longitudinal loading ~all herein referred to as "rails").
In the specification of Canadian Patent No. 975,576, issued July 10, 1975 (John Charles Luchs and George William Moreland, inventors) there is described and claimed a system for measuring the longitudinal orce in a rail comprising a strain gauge set in a hole in the rail, which hole extends depthwise transversely of the rail, the output o~ the strain gauge varying upon changes in cross-sectional shape of the hole caused by changes in longitudinal force in the rail.
The strain gauge described in ~he aforesaid specifica-tion is a vibrating wire strain gauge comprising at least one wire which extand diametrically across and is secured at its ends to a ring which conforms to the periphery of the hole in the rail and is secured around its periphery to the rail and an electro-magnetic coil arrangement supported by the ring for sPtting the wire in vibration and then detecting the vibration frequency of the wire.
The object of the present invention is to provide an advantageous electromagnetic coil arrangement for a vibrating wire strain gauge of the form described in the aforesaid speci-fication.
According to the invention the electromagnetic coil arrangement comprises an annular coil surrounding a single pole piece which extends axially of the ring towards the wire and which is connected to the ring so that magnetic circuit is com-pleted through the body of the ring and the wire.
In use of the system described in the aforesaid speci-fication the electromagnetic coil arrangement comprised a coil mounted on a pair of pole pieces which thus effectively formed 2S~
a 'U' shaped electromagnet. Hence the wire was set in-to vibra-tion by plucking it at two spaced points at for example 1/4 and 3/4 the way along the length of the wire from one end. In con-trast, with the single pole piece in accordance with the present invention, the wire is plucked at one point substantially at the mid-length of the wire. This feature together with the feature of using the ring as part of the magnetic circuit leads to the following advantages: !
i. A more efficient pluck leading to an improved characteristic for the strain gauge.
ii. The possibility of reducing the size of the electromagnetic coil arrangement so that the strain gauge can be contained whol-ly within the width of the web of a rail of railway track in order to reduce the risk of damage to it by for example track maintenance machines.
iii. Simplicity of construction and hence reduction in cost. ;
iv. Maximum use of space within the strain gauge leading to increased output and thereby reducing requirements on read-out equipment, i.e. equipment to which the electromagnetic coil arrangement is electrically connected for determining the vibration frequéncy of the wire.
Advantageously the pole piece can project from and be supported by, an end cap for the ring; for example the pole piece may be formed integral with the end cap. Thus where the strain gauge has two vibrating wires each associated with a respective magnetic coil arrangement, each pole piece can be supported by a respective end cap for the ring. The two wires may extend at .
~4~
right angles -to each o~her as described in the aforesaid speci-fication or pa.rallel to each other, in which case the ring would be set in the hole in the rail so that the wires exte.nd longitu-dinally of the rail.
In further development of the invention, the gauge can be formed in two axially separable parts, a first part carrying the wire and a second part carrying the annular coil. Thus only , said first part need by permanently installed in a rail, the second part bein~ transportable with the associated measuring instrument. This development of the invention leads to simplifi- -cation of the part of the gauge installed in the rail and there-fore reduction in its cost. In addition a much greater freedom in coil design and size is possible.
Two constructions of strain gauge in accordance with the invention will now be described by way of example with refer-ence to the accompanying drawing, in which:
Figure 1 shows a cross-section through one construction - of strain gauge, Figure 2 is a diagram of the maynetic circuit set up ~0 in the device of Figure 1, and Figure 3 is a cross-section of the second construction :`
of strain gauge.
. Referring to Figures 1 and 2, the strain gauge has a pair of parallel wires 1 and 2 extending diametrically across a ring 3 and locked to the ring at their ends by locking pins 4.
The wires 1 and 2 are associated with electromagnetic coil arran-gements 5 and 6 respectively for setting the wires 1 and 2 in vibration and for detecting the vibration frequency in the manner described in our aforesaid specification. Each electromagnetic coil arrangement comprises an annular coil 7 surrounding a pole piece 8 which extends axially of the ring 3 to a position closely adjacent its associated wire 1 and 20 The pole piece 8 projects .~ from a respective end wall of the ring 3 in the form o~ an end .. . . ~
cap 9 for the ring ', ~he end cap being secured in position by locking screws 10 which ~lso serve to hold the wire locking pins 4 in position.
In use the strain gauge can be mounted in a hole in ihe vertical web of a rail of railway track shown at 12 in Figure 1. With this parallel wire strain gauge the ring is set in the hole so that the two wires extend longitudinally of the rail.
Conveniently the outside diameter of the ring 3 corresponds to the standard fish bolt hole diameter to facilitate fitting of the strain gauge in the rail. The ring 3 is fixed around its peri-phery to the hole in the rail web so that any changes in shape of the hole will cause corresponding changes in shape of the ring and hence variation in the vibration frequency of the wires 1 and
2. Advantageously the ring 3 and wires 1 and 2 have the same coefficient of thermal expansion as the rail. Thus the ring 3 ` may comprise a thin-walled hollow steel cylinder and the wires 1 and 2 high tensile steel wires.
When the coils 7 are energised a magnetic circuit is ?
set up as shown in Figure 2, the flux path being through the pole - 20 pieces 8 the wires 1 and 2, the ring 3 and the end caps 9. In Figure 1 the pole pieces 8 are shown as integrally formed with the end caps 9, but~they could be formed separately from the end caps .
, 9 and appropriately secured to them. In either case the end caps will be of ferromagnetic material, e.g. steel.
The construction of strain gauge shown in Figure 3 is basically the same as that shown in Figure 1. It comprises a wire 11 extending diametrically across a ring 13. The wire 11 is associated with an electromagnetic coil arrangement comprising an annular coil 15 surrounding a pole piece 18 which extends axially of the ring 13 to a position closely adjacent the wire 11.
Differently from the construction of Figure 1, the strain gauge of Figure 3 is in two axially separable parts achieved by forming the ring 13 in two axially separable parts -13a and 13b, the part 13_ carrying the wire 11 and being mounted in the rail web 22 and the part 13b being transportable and car-rying the coil 15. The pole piece 18 is in two parts 18 and 18b associated with the ring parts 13a and 13b re pectively.
The part 18a of the pole piece i~ mounted at the centre of a disc 20 of non-ferromagnetic material secured in the ring part 18a.
The part 18b of the pole piece extends from end wall 21 of the ring part 13b.
In use the ring part 13b of the strain gauge is brought 10 illtO abutment with the ring part 13a so that the two ring parts 13a and 13b parts are in axial alignment. The magnetic cixcuit is therefore effectively shown in Figure 2.
~ ., , , , . , ~ , .
When the coils 7 are energised a magnetic circuit is ?
set up as shown in Figure 2, the flux path being through the pole - 20 pieces 8 the wires 1 and 2, the ring 3 and the end caps 9. In Figure 1 the pole pieces 8 are shown as integrally formed with the end caps 9, but~they could be formed separately from the end caps .
, 9 and appropriately secured to them. In either case the end caps will be of ferromagnetic material, e.g. steel.
The construction of strain gauge shown in Figure 3 is basically the same as that shown in Figure 1. It comprises a wire 11 extending diametrically across a ring 13. The wire 11 is associated with an electromagnetic coil arrangement comprising an annular coil 15 surrounding a pole piece 18 which extends axially of the ring 13 to a position closely adjacent the wire 11.
Differently from the construction of Figure 1, the strain gauge of Figure 3 is in two axially separable parts achieved by forming the ring 13 in two axially separable parts -13a and 13b, the part 13_ carrying the wire 11 and being mounted in the rail web 22 and the part 13b being transportable and car-rying the coil 15. The pole piece 18 is in two parts 18 and 18b associated with the ring parts 13a and 13b re pectively.
The part 18a of the pole piece i~ mounted at the centre of a disc 20 of non-ferromagnetic material secured in the ring part 18a.
The part 18b of the pole piece extends from end wall 21 of the ring part 13b.
In use the ring part 13b of the strain gauge is brought 10 illtO abutment with the ring part 13a so that the two ring parts 13a and 13b parts are in axial alignment. The magnetic cixcuit is therefore effectively shown in Figure 2.
~ ., , , , . , ~ , .
Claims (7)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A vibrating wire strain gauge comprising at least one wire which extends diametrically and is secured at its ends to a ring and an electromagnetic coil arrangement for setting the wire in vibration and then detecting the vibration frequency of the wire, wherein the electromagnetic coil arrangement com-prises an annular coil surrounding a single pole piece which extends axially of the ring towards the wire and which is con-nected to the ring so that the magnetic circuit is completed through the body of the ring and the wire.
2. A vibrating wire strain gauge according to claim 1, wherein said pole piece is formed integrally with a ferromag-netic end wall of the ring and which constitutes a part of the magnetic circuit.
3. A vibrating wire strain gauge according to claim 2, wherein said end wall comprises a separately formed end cap.
4. A vibrating wire strain gauge according to claim 1, and formed of two axially separable parts, a first of said parts carrying said wire and the second of said parts carrying said annular coil.
5. A vibrating wire strain gauge according to claim 4, wherein said first and second parts are axially separable first and second ring parts.
6. A vibrating wire strain gauge according to claim 5, wherein said second ring part has an end wall from which at least part of the length of said pole piece extends axially.
7. A vibrating wire strain gauge according to claim 6, wherein a part of the length of said pole piece is carried by said first ring part.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB18559/75A GB1509044A (en) | 1975-05-02 | 1975-05-02 | System for measuring the longitudinal force in a rail |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1048296A true CA1048296A (en) | 1979-02-13 |
Family
ID=10114531
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA76251412A Expired CA1048296A (en) | 1975-05-02 | 1976-04-29 | Measurement of the change in longitudinal force in a rail |
Country Status (9)
| Country | Link |
|---|---|
| AU (1) | AU497246B2 (en) |
| CA (1) | CA1048296A (en) |
| DE (1) | DE2619150A1 (en) |
| ES (1) | ES447500A2 (en) |
| FR (1) | FR2309850A2 (en) |
| GB (1) | GB1509044A (en) |
| IT (1) | IT1063964B (en) |
| SE (1) | SE7604951L (en) |
| ZA (1) | ZA762508B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE69632325T2 (en) * | 1995-07-14 | 2005-06-02 | Brent Felix Jury | METHOD AND DEVICE FOR VOLTAGE TESTING |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE727455C (en) * | 1938-12-04 | 1942-11-04 | Walter Huendorf Dipl Ing | Method for determining the surface tension of stressed components that are particularly under static load |
| FR985978A (en) * | 1943-11-23 | 1951-07-25 | Acoustic manometric capsule | |
| FR1007568A (en) * | 1950-01-04 | 1952-05-07 | Manometric capsule | |
| GB1288378A (en) * | 1968-11-18 | 1972-09-06 | ||
| GB1336311A (en) * | 1970-06-15 | 1973-11-07 | British Railways Board | Measurement of the change in longitudinal force in a rail |
| FR2227520B1 (en) * | 1973-04-27 | 1975-08-22 | British Railways Board |
-
1975
- 1975-05-02 GB GB18559/75A patent/GB1509044A/en not_active Expired
-
1976
- 1976-04-27 ZA ZA762508A patent/ZA762508B/en unknown
- 1976-04-29 IT IT22826/76A patent/IT1063964B/en active
- 1976-04-29 SE SE7604951A patent/SE7604951L/en unknown
- 1976-04-29 CA CA76251412A patent/CA1048296A/en not_active Expired
- 1976-04-30 ES ES447500A patent/ES447500A2/en not_active Expired
- 1976-04-30 DE DE19762619150 patent/DE2619150A1/en not_active Ceased
- 1976-04-30 AU AU13547/76A patent/AU497246B2/en not_active Expired
- 1976-05-03 FR FR7613181A patent/FR2309850A2/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| IT1063964B (en) | 1985-02-18 |
| ZA762508B (en) | 1977-04-27 |
| AU1354776A (en) | 1976-07-29 |
| ES447500A2 (en) | 1977-08-01 |
| GB1509044A (en) | 1978-04-26 |
| SE7604951L (en) | 1976-11-03 |
| DE2619150A1 (en) | 1976-11-11 |
| FR2309850A2 (en) | 1976-11-26 |
| AU497246B2 (en) | 1978-12-07 |
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