GB2157831A - Magnetically monitoring the movement of a rod - Google Patents
Magnetically monitoring the movement of a rod Download PDFInfo
- Publication number
- GB2157831A GB2157831A GB08408999A GB8408999A GB2157831A GB 2157831 A GB2157831 A GB 2157831A GB 08408999 A GB08408999 A GB 08408999A GB 8408999 A GB8408999 A GB 8408999A GB 2157831 A GB2157831 A GB 2157831A
- Authority
- GB
- United Kingdom
- Prior art keywords
- rod
- sensor
- sensors
- pulses
- magnetic
- 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.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
- G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
- G01D5/142—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage using Hall-effect devices
- G01D5/145—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage using Hall-effect devices influenced by the relative movement between the Hall device and magnetic fields
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
- G01P3/42—Devices characterised by the use of electric or magnetic means
- G01P3/50—Devices characterised by the use of electric or magnetic means for measuring linear speed
- G01P3/54—Devices characterised by the use of electric or magnetic means for measuring linear speed by measuring frequency of generated current or voltage
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
Abstract
The movement of a rod 24 which passes through a cylindrical seal or bearing 26 is monitored by a magnetic discontinuity sensor 60, the rod being formed by taking a generally cylindrical bar of ferromagnetic material, cutting one or more grooves 50 therein to provide magnetic discontinuities and providing the bar with a cylindrical surface by applying non- ferromagnetic material thereto to cover and/or fill said groove or grooves. One or more magnetic sensors such as Hall effect devices are mounted adjacent the path of the rod to sense the magnetic discontinuities and the output signals of the sensor 60 are used to determine the position and/or velocity of the rod. If two sensors are spaced apart so as to give outputs 90 DEG out of phase, the position and velocity of the rod can be determined. <IMAGE>
Description
SPECIFICATION
Method of monitoring the movement of a rod
This invention is concerned with a method of monitoring the movement of a rod which passes through a cylindrical seal or bearing.
An example of such a rod is a piston rod which is movable in a cylinder upon the introduction of fluid under pressure into the cylinder, the piston rod passing through a cylindrical seal in an end cap of the cylinder.
A further example of such a rod is a rod which is mounted on a cylindrical bearing for linear movement along the longitudinal axis of the rod or for turning movement about the longitudinal axis.
In many different types of machine, there are rods which pass through cylindrical seals or bearings. For example, glassware forming machines of the individual section type have fluid pressure operated piston and cylinder assemblies for moving mould parts, pressing plungers into molten glass, and for moving baffles, blow heads, funnels and neck rings thereof. These piston and cylinder assemblies have piston rods which project from the pistons through seals in end caps of the cylinders and are connected to the parts to be moved.The baffles, blow heads, and funnels of such machines are supported on rods which pass through cylindrical bearings to allow these parts to be moved between operative and out-of-the-way positions thereof along paths which have linear and arcuate components, the linear component being achieved by moving the rod linearly along its longitudinal axis and the arcuate component by turning the rod about its longitudinal axis. In some machines, it is desirable to be able to detect the position or the velocity of parts so that the information can be used to determine whether the parts are moving as desired.For example, with the above-mentioned glassware forming machines of the individual section type, it has been recognised that the machine can operate more efficiently if electronic control means therefor, which controls the timing of the various events in the machine, receives feedback concerned with part movements.
The control means can, for example, optimise the movements of the various parts to obtain maximum machine speed without risking collisions between the parts. Thus, it is desirable to provide sensors which can sense the movements of the parts. However, the part may be of an unsuitable shape for detection other than by the arrival of a portion of the part at a given position so that its movement towards the position cannot be effectively monitored or the part may be moving in an environment which is hostile to electronic sensors. In some cases, an additional member has been attached to the part which is then sensed by a sensor so that the additional part can be made in a suitable shape for sensing the entire movement thereof.However, in many cases, space considerations preclude the mounting of additional parts on the moving part and this does not overcome the problems of hostile environments.
Where the part whose movement it is desired to monitor is mounted on the piston rod of the piston and cylinder assembly or on a rod which passes through a cylindrical bearing, the movement can be monitored by monitoring the movement of the rod itself which is of a suitable shape and generally outside any hostile environment. However, the use of sensors which sense magnetic discontinuities in monitoring the movement of a rod has the difficulty that the rod must have a smooth cylindrical surface to enable it to pass through the seal at the end cap of the cylinder or the cylindrical bearing. Thus, conventional rods which consist of ferromagnetic material and are cylindrical cannot generally be monitored during their movement by magnetic discontinuity detectors.
It is an object of the present invention to provide a method of monitoring the movement of a rod in which a magnetic sensor is used which detects magnetic discontinuities.
The invention provides a method of monitoring the movement of a rod which passes through a cylindrical seal or bearing, the method comprising forming the rod by taking a generally cylindrical bar of ferromagnetic material, cutting one or more grooves in the cylindrical surface of the bar so that it has magnetic discontinuities along its length, and providing the bar with a cylindrical surface by applying non-ferromagnetic material thereto to cover and/or fill said groove or grooves, mounting a magnetic sensor adjacent to the path of the rod so that the sensor senses the magnetic discontinuities as they pass the sensor, and using output signals of the sensor to determine the position and/or velocity of the piston rod.
In a method in accordance with the last preceding paragraph, the rod presents a cylindrical surface to the seal or bearing but the magnetic sensor "looks through" the nonferromagnetic material to sense the magnetic discontinuities.
In order that the sensor can produce a series of pulses indicating the amount of movement of the rod, the magnetic discontinuities may be uniformly spaced along the portion of the surface of the which passes the sensor. To achieve this, conveniently, in forming the rod a screw thread is applied to the bar.
In one method of forming the rod, the groove or grooves may be covered by a cylindrical sleeve of non-ferromagnetic material, e.g. stainless steel.
In another method of forming the rod, the groove or grooves may be filled and covered by plating the bar with non-ferromagnetic material, e.g. hard chrome.
In order to further increase the accuracy of the monitoring, one or more further sensors may be mounted adjacent to the path of the rod so that it or they also each sense the magnetic discontinuities and each produces a further chain of pulses, the further sensor or sensors being so positioned that its or their chain or chains of pulses is or are out of phase with the chain of pulses produced by the first-mentioned sensor, and the chains of pulses from the sensors are combined to form a combined output signal from which the position and/or velocity of the rod is determined.
Conveniently, the sensor or sensors are Hall sensors which detect changes in the magnetic field in their environment by utilising the Hall effect. A suitable sensor can be obtained from the West German firm Siemens A.G. under designation FP210 L100.
Where it is likely that the rod will need to be exchanged for a replacement rod, the sensor or sensors may be connected to control means via a contactless connector, the receiver of which is mounted for removal with the rod, and the transmitter of which is mounted on a frame of a machine in which the rod is mounted. Thus, when the rod is exchanged, it can be removed without disconnecting any wires and a replacement rod can be mounted so that a receiver mounted thereon co-operates with the transmitter on the frame. A suitable contactless connector can be obtained from the Swiss firm Wepatron AG under designation 20/15.
Where the rod forms part of a glassware forming machine of the individual section type, the output signals may be fed to an electronic control system of the machine. In this case, the control system can calculate whether the timing of impulses it produces to cause movement of the rod should be altered.
There now follows a detailed description, to be read with reference to the accompanying drawings, of two methods of monitoring the movement of a rod which are illustrative of the invention. In the first illustrative method, the rod is a piston rod of a piston and cylinder assembly and, in the second illustrative
method, the rod passes through a bearing. It is to be understood that the illustrative
methods have been selected for description by way of example and not of limitation of the invention.
In the drawings:
Figure 1 is a longitudinal cross-sectional view taken through the piston and cylinder assembly to the piston rod of which the illustrative method is applied;
Figure 1 a is a detailed view of a portion of a piston rod of the piston and cylinder assembly shown in Figure 1;
Figure 2 is a side elevational view, with parts broken away to show the construction, of a rod passing through a cylindrical bearing to which the second illustrative method is applied; and
Figure 3 is a diagrammatic view of output signals obtained in the second illustrative method.
The piston and cylinder assembly shown in
Figure 1 is for use in a glassware forming machine of the individual section type and is specifically designed to move a glass-pressing plunger into a mould containing molten glass so that the glass is pressed to the shape of a cavity of the mould. The piston and cylinder assembly comprises a cylinder 10 which is formed in a block of metal 1 2 in which a further cylinder 14 of an adjacent piston and cylinder assembly is also formed.The assembly also comprises a piston 1 6 movable in the cylinder 10 when fluid under pressure is introduced into the cylinder 10 either below the piston 1 6 through a port 1 8 or above the piston 1 6 through a port (not shown) at an upper end portion of the cylinder 1 0. The cylinder 10 has an upper end cap 20 and a lower end cap 22, through which the port 18 passes.
A piston rod 24 of the assembly projects upwardly from the piston 1 6 and passes through a seal 26 supported by the upper end cap 20. Upon introduction of fluid under pressure into the cylinder 10, the piston 1 6 moves the piston rod 24 either upwardly through the seal 26 or downwardly back through the seal 26. An upper end portion 30 of the piston rod 24, outside the cylinder 10,
is externally screw threaded so that it can receive a plunger (not shown) of the glassware forming machine. A recess 27 is formed in the upper side of the piston 1 6 to co-operate with a spring-loaded plunger 28 supported by the end cap 20 in preventing the piston 1 6 and the piston rod 24 from turning while a
plunger is screwed on to the portion 30.A
generally cylindrical hollow passage 32 passes through the piston rod 24 and the piston 1 6 and receives a tube 34 which projects upwardly from the lower end cap 22 through a
seal 36 mounted in a recess in the piston 1 6.
The purpose of the tube 34 and the passage
32 is to connect an air passage 38 in a frame
40 on which the piston and cylinder assembly
is mounted to an air passage within the
plunger mounted on the portion 30 of the
piston rod 24. Air from the passage 38 may
be used to cool the plunger during its operation. Thus, the piston rod 24 is movable with the piston 1 6 which is movable in the cylinder
10 upon the introduction of fluid under pres
sure into the cylinder 1 0. The piston rod 24
passes through the seal 26 and the end cap
20 of the cylinder 10 so that the external
surface of the piston rod 24 must be cylindri
cal and smooth.
The construction of the piston rod 24 will now be described in detail. The piston rod 24 is formed by taking a generally cylindrical bar of ferromagnetic material, i.e. steel, which is integral with the piston 16, cutting a groove 50 in the cylindrical surface of the bar in the form of a screw thread. The bar then has magnetic discontinuities along its length since there is more steel in edge portions thereof where the groove has not been cut than there is where the groove has been cut. The piston rod 24 is then hard chrome plated to provide it with a cylindrical surface. Thus, non-ferromagnetic material is applied thereto to fill said groove and cover the steel of the piston rod 24. Thus, the piston rod 24 is provided with a smooth cylindrical surface which can make a successful seal with the seal 26.The hard chrome material 52 (see Figure la) fills the groove 50 and forms a thin cylindrical surface 54 on the piston rod 24. Other non-ferromagnetic materials may be used to plate the piston rod 24 and the magnetic discontinuities may be created by means of a series of annular grooves around the ferromagnetic bar rather than by a continuous spiral groove.
Furthermore, it is not necessary to fill the groove or grooves with non magnetic material but a sleeve of non-ferromagnetic material may be applied to the outside of the piston rod 24 to cover the groove or grooves and to provide a smooth cylindrical outer surface.
A magnetic sensor 60 is mounted adjacent to the path of the piston rod 24 on the upper end cap 20 so that the sensor 60 senses the magnetic discontinuities caused by the groove 50 as they pass the sensor 60. The sensor 60 is a Hall sensor which depends on the Hall effect, i.e. that when a magnetic field is applied perpendicular to a conductor carrying current, a potential difference is observed between points on opposite sides of the conductor, points which, in the absence of the field would be at the same potential. The detector 60 detects the difference in magnetic field caused by the magnetic discontinuities along the length of the piston rod 24 and produces a chain of pulses as an output signal.This output signal can be used to determine the position of the piston rod since the number of pulses which have occurred indicate how far the piston rod has travelled and also to indicate the velocity of the piston rod since the frequency of pulses enables this to be calculated. Thus, the output signals of the sensor 60 can be used to determine the position and/or velocity of the piston rod 24. The sensor 60 is connected by wires (not shown) to a contactless connector 64 which comprises a receiver 66 mounted on the bottom end cap 22 and a transmitter 68 mounted on the frame 40 adjacent to the receiver 66. The contactless connector is able to pass electrical signals between the receiver 66 and the transmitter 68 thereof without there being any electrical wires extending between the two.
The transmitter 68 transmits the output signals received from the receiver 66 to a control system of the machine.
Thus, the illustrative method comprises forming the piston rod 24 with magnetic discontinuities as described above, mounting the magnetic sensor 60 adjacent to the path of the piston rod 24 to sense the magnetic discontinuities, and using the output signals of the sensor 60 to determine the position and/or velocity of the piston rod 24. Since the magnetic discontinuities are uniformly spaced along the portion of the surface of the piston rod 24 which passes the sensor 60, the sensor 60 produces a train of pulses of uniform spacing if the velocity of the piston rod 24 is uniform.
Figure 2 illustrates the second illustrative method in which two Hall sensors 80 and 82 are mounted on an end cap 84 of a cylindrical bearing 86 through which a rod 88 passes.
The rod 88 is formed with magnetic discontinuities in the same way as the piston rod 24.
The sensor 80 acts in the same way as the sensor 60 to sense the magnetic discontinuities as the rod 88 moves past the sensor 80.
The further sensor 82 is mounted also adjacent to the path of the rod 88 so that it senses the magnetic discontinuities and produces a further chain of pulses. The chain of pulses of the sensor 80 are indicated in
Figure 3 by the chain 90 and the pulses of the sensor 82 are indicated by the chain of pulses 92 in Figure 3. The further sensor 82 is so positioned that its chain of pulses is 90 out of phase with the chain of pulses 90 produced by the first-mentioned sensor 80.
This can be done by separating the sensors 80 and 82 by a suitable distance longitudinally of the piston rod 88 or by separating the sensors 80 and 82 by 90 about the longitudinal axis of the piston rod 88. The two chains of puises 90 and 92 from the two sensors are combined to form a combined output signal from which the position and/or velocity of the piston rod is calculated. The combined signal provides a more accurate position and/or velocity indication since it contains sharper pulses than those of either of the chains 90 or 92. If desired, one or more further sensors, in addition to the sensor 82 can be mounted on the end cap 84 to give further chains of pulses, out of phase with those of the sensors 80 and 82, all the chains being combined to give the combined output signal. Further sensors can also be used in this way in modifications of the first illustrative method.
Claims (10)
1. A method of monitoring the movement of a rod which passes through a cylindrical seal or bearing, the method comprising forming the rod by taking a generally, cylindrical bar of ferromagnetic material, cutting one or more grooves in the cylindrical surface of the bar so that it has magnetic discontinuities along its length, and providing the bar with a cylindrical surface by applying non-ferromagnetic material thereto to cover and/or fill said groove or grooves, mounting a magnetic sensor adjacent to the path of the rod so that the sensor senses the magnetic discontinuities as they pass the sensor, and using output signals of the sensor to determine the position and/or velocity of the piston rod.
2. A method according to claim 1, wherein the magnetic discontinuities are uniformly spaced along the portion of the surface of the rod which passes the sensor so that the sensor produces a chain of pulses.
3. A method according to claim 2, wherein in forming the rod a screw thread is applied to the bar.
4. A method according to either one of claims 2 and 3, wherein one or more further sensors is or are mounted adjacent to the path of the rod so that it or they also each sense the magnetic discontinuities and each produces a further chain of pulses, the further sensor or sensors being so positioned that its or their chain or chains of pulses is or are out of phase with the chain of pulses produced by the first-mentioned sensor, and the chains of pulses from the sensors are combined to form a combined output signal from which the position and/or velocity of the rod is determined.
5. A method according to any one of claims 1 to 4, wherein the groove or grooves are covered by a cylindrical sleeve of non-ferromagnetic material.
6. A method according to any one of claims 1 to 4, wherein the groove or grooves are filled and covered by plating the bar with nonferromagnetic material.
7. A method according to any one of claims 1 to 6, wherein the sensor or sensors are of the Hall type.
8. A method according to any one of claims 1 to 7, wherein the sensor or sensors are connected to control means via a contactless connector, the receiver of which is mounted for removal with the rod, and the transmitter of which is mounted on a frame of a machine in which the rod is mounted.
9. A method according to any one of claims
1 to 8, wherein the rod forms part of a glassware forming machine of the individual section type and the output signals are fed to an electronic control system of the machine.
10. A method of monitoring the movement of a piston rod substantially as hereinbefore described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08408999A GB2157831A (en) | 1984-04-06 | 1984-04-06 | Magnetically monitoring the movement of a rod |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08408999A GB2157831A (en) | 1984-04-06 | 1984-04-06 | Magnetically monitoring the movement of a rod |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8408999D0 GB8408999D0 (en) | 1984-05-16 |
| GB2157831A true GB2157831A (en) | 1985-10-30 |
Family
ID=10559320
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08408999A Withdrawn GB2157831A (en) | 1984-04-06 | 1984-04-06 | Magnetically monitoring the movement of a rod |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2157831A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1988005151A1 (en) * | 1986-12-24 | 1988-07-14 | Pav Präzisions-Apparatebau Aktiengesellschaft | Calipers |
| WO1991019168A1 (en) * | 1990-05-25 | 1991-12-12 | Remote Marine Systems Limited | Magnetic sensing method and system |
| GB2259989A (en) * | 1990-05-25 | 1993-03-31 | Remote Marine Systems Ltd | Magnetic sensing method and system |
| EP0578999A1 (en) * | 1992-06-24 | 1994-01-19 | WARREN RUPP, Inc. | Electronic control interface for fluid powered diaphragm pump |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB967821A (en) * | 1960-02-19 | 1964-08-26 | Sperry Gyroscope Co Ltd | Improvements in electro-hydraulic actuators |
| GB1290093A (en) * | 1969-04-03 | 1972-09-20 | ||
| GB1393093A (en) * | 1971-07-26 | 1975-05-07 | British Non Ferrous Metals Res | Die casting or injection moulding machines |
| GB2056692A (en) * | 1979-08-18 | 1981-03-18 | Bosch Gmbh Robert | Magnetic measurement of position and/or speed of a piston |
-
1984
- 1984-04-06 GB GB08408999A patent/GB2157831A/en not_active Withdrawn
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB967821A (en) * | 1960-02-19 | 1964-08-26 | Sperry Gyroscope Co Ltd | Improvements in electro-hydraulic actuators |
| GB1290093A (en) * | 1969-04-03 | 1972-09-20 | ||
| GB1393093A (en) * | 1971-07-26 | 1975-05-07 | British Non Ferrous Metals Res | Die casting or injection moulding machines |
| GB2056692A (en) * | 1979-08-18 | 1981-03-18 | Bosch Gmbh Robert | Magnetic measurement of position and/or speed of a piston |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1988005151A1 (en) * | 1986-12-24 | 1988-07-14 | Pav Präzisions-Apparatebau Aktiengesellschaft | Calipers |
| US5029402A (en) * | 1986-12-24 | 1991-07-09 | Rene Lazecki | Sliding gauge |
| WO1991019168A1 (en) * | 1990-05-25 | 1991-12-12 | Remote Marine Systems Limited | Magnetic sensing method and system |
| GB2259989A (en) * | 1990-05-25 | 1993-03-31 | Remote Marine Systems Ltd | Magnetic sensing method and system |
| GB2259989B (en) * | 1990-05-25 | 1994-02-09 | Remote Marine Systems Ltd | Magnetic sensing method and system |
| EP0578999A1 (en) * | 1992-06-24 | 1994-01-19 | WARREN RUPP, Inc. | Electronic control interface for fluid powered diaphragm pump |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8408999D0 (en) | 1984-05-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |