|Title of Invention||
|Abstract||The present invention relates to a rail thermometer comprising a thermometer casing with a thermometer provided therein, said casing being provided at one end with an adhesive member to secure the said casing to the rail track, and a heat conducting means to transfer the heat from the rail to the thermometer bulb, said heat conducting means being connected to said thermometer inside said casing through a fastening means.|
|Full Text||RAIL THERMOMETER
Field of the invention
The present invention relates to a rail thermometer. More particularly, the present invention relates to a rail thermometer for taking the temperature of a railway track or any ferromagnetic 'flat surface. Background of the invention
Railway lines generally use long welded railway tracks which comprise a 3 to 4 kilometer long railway track _piece without any gap therebetween. With diurnal changes in the temperature, the track piece expands and contracts linearly. The linear expansion of railway track pieces results in the formation of several stresses therein. However, since the contraction of the track is not directly opposite of expansion, residual stresses remain in the railway track piece. All railway systems carry out regular destressing to remove residual stresses in order to prevent flaws developing in the railway track. Destressing is normally done by unlocking the rail length from the track and then locking it back again to the sleepers (or ties) which allows the rail time to take its natural shape and remove residual stresses. Ideally destressing needs to be done when the track temperature is closest to the neutral temperature or distressing temperature in a particular area. Destressing temperature is determined according to the local geographical conditions and vary from region to region depending on the local climatic conditions.
Failure to destress the rail lengths or destressing at the wrong
temperature results in retention of the residual stresses in the rail track and
to latent deformities therein. Over a period of time, such latent deformities result in cracking or buckling of the track and impact on the safety levels of the railway system. This also results in losses of expensive material and also costs towards hold up of train schedules while rectification of the residual stresses if carried out afresh. It is therefore essential that destressing is carried out at the appropriate temperature to ensure that there are no residual stresses in the track length and to ensure that there is no loss of material. In view of the above, it is imperative that the temperature of a track be measured accurately and speedily to ensure that destressing can be carried out appropriately.
JP 01015624 A discloses a method for the measurement of temperature of road surfaces in order to prevent the effects of wear, vibration and the like caused by the
running of vehicles, by providing measuring means for measuring temperatures at places, where the running of the vehicles is not interrupted. The device comprises a thermometer which includes a resistor, whose electric resistance value is changed. The thermometer is connected to a temperature transducer through a piece of cable. The temperature transducer outputs a signal representing the temperature into a correcting circuit based on the measured resistance value. The correcting circuit corrects the output signal from the temperature transducer. Thus the signal, which represents the temperature of a road surface, is obtained and sent to an observing station and a display device. In working, the thermometer is fixed with a piece of angle sfeel, which is attached to a post of a guard rail. Since the thermometer is provided in the vicinity of a region,
vehicles run, the working is simplified, and the thermometer is not affected by vibration and wear caused by the running of the vehicles.
JP 58216924 A discloses a rail stress detection system which is used to measure the axial tension of a rail by a magnetic anisotrqpic detection sensor, by averaging four peak output values accompanied by magnetic anisotropy yielded by stress, based on the output of the magnetic anisotropic sensor, and performing correction based on the temperature. A rail axial tension detecting sensor is attached to a rail. When an anisotropic sensor is rotated, signals are obtained for 0°W360°. Four peak values are detected by a peak value detecting circuit. Said peak value data are sequentially added, and an average value is computed by an average value circuit. The corresponding rail axial tension is read from said average value by a converter and displayed on a display device. The value of the rail axial tension is corrected by the temperature data from a thermometer in a temperature correcting circuit so as to obtain the value of the standard temperature. The value is compared with upper and lower limit values in a comparator. When the value exceeds the limit value, a signal is outputted and displayed on the display circuit.
It is also known in the art to use mercury in glass thermometer encased in an aluminum protective jacket. In the lower cavity of the cover a cylindrical permanent magnet is screwed in. On the upper side of the diaphragm where the magnet is screwed a copper clip is screwed. The thermometer bulb is held in the said clip. The device is placed vertically on the track, and adheres to the track rail with the help of the magnet. The magnetic base conducts the heat of the rail to the diaphragm, which
•^onducts the heat to the copper clip that in turn conducts the heat to the thermometer. However, this device suffers from many disadvantages. As is evident there are four interfaces between the rail and the thermometer: rail to magnet, magnet to diaphragm, diaphragm to clip, and clip to bulb. The existence of these four interfaces results in:
i) Significant slowing down of the response of the thermometer, ii) Heat loss to the casing of the thermometer since the magnet (which is also the conducting component) is in direct contact with the case. The case loses heat to the air at a rate faster than it gains from the rail (through the magnet). Thus the equilibrium temperature of the device, which is recorded by the thermometer is significantly lower than that of the rail, iii) Long time (about 30 minutes) taken to show the final temperature (equilibrium temperature) because the thermal conductivity of the magnet is low. This period of time is unacceptable as it leads to a lot of idle time for the destressing crew.
Another disadvantage of this device is that the device is a straight piece, which causes the person inspecting the rail temperature to either bend at a very odd angel or lift the device off the rail repeatedly. Both are undesirable methods of temperature recording. The magnet is a strontium magnet and hence requires a pole keeper to avoid its demagnetization. The pole keeper being a small piece leads to misplacement by human error. This behavioral problem of users leads to a reduced life cycle of the instrument or a drop in magnetic adhesion.
The root cause of the problem is that the instrument uses the magnet as a means of securing the device to the rail and also as a conductive medium and (2) the conductive medium (the magnet in this case) has not been insulated form the rest of the case.
Another prior art thermometer used is a black bulb thermometer wherein a thermometer with a blackened bulb is mounted on a metal plate such that the edges of the plate lock over the rail sides while the bulb comes in direct contact with the rail. This device gives a good response but faces major problems of breakage while in use and direct insolation (sunlight) interfering with the reading.
It is therefore important and necessary to develop a temperature measurement device for rail tracks which has a low response time and minimal margin for error in reading. Objects of the invention
It is an object of the invention to develop a rail thermometer which has a low response time.
It is another object of the invention to develop a rail thermometer which shows minimal margin for error in temperature readings and is therefore possessed of greater accuracy.
It is a further object of the invention to develop a rail thermometer which enables easy readings of temperature without detaching from the rail track or requiring unnatural postures.
It is yet another object of the invention to develop a rail thermometer which is rugged and substantially breakage .free.
^Summary of the invention
These and other objects of the invention are achieved by the rail thermometer of the invention wherein the novel construction employed reduces the number of conductive interfaces between the rail and the thermometer while strengthening the device itself to ensure that the chances of breakage are minimised. Additionally, the reduced number of interfaces ensures a greater degree of accuracy and reduced response time in temperature readings from the rail.
Accordingly, the present invention provides a rail thermometer comprising a thermometer casing with a thermometer provided therein, said casing being provided at one end with an adhesive member to secure the said casing to the rail track, and a heat conducting means to transfer the
heat from the rail to the thermometer bulb, said heat conducting means being connected to said thermometer inside said casing through a fastening means.
In one embodiment of the invention, the fastening means comprises a clip adaptable to secure the bulb end of the said thermometer.
In another embodiment of the invention, the heat conducting means comprises a sheet metal plate provided in a bell type structure.
In a further embodiment of the invention, the heat conducting means is insert molded into the bell.type structure.
In a further embodiment of the invention, the adhesive member is integral with said bell shaped structure while heat insulated therefrom by insulating means.
In a further embodiment of the invention, the adhesive member is integral with said bell type sensor while insulated therefrom by an insulating means.
In another embodiment of the invention, the thermometer casing is provided with a viewing means to view the temperature readings on the said thermometer.
In yet another embodiment of the invention, the said viewing means is provided with a moving means to move it from a first viewing position to a second closed position. Brief description of the accompanying drawings
Figure 1 is a representation of the rail thermometer according to the invention.
Figure 2 is a representation of the casing for the rail thermometer according to the invention.
Figure 3 (a) is a representation of the spring locking ball used to secure the thermometer bulb according to the invention.
Figure 3(b) is a representation of the spring gripping device which renders the thermometer immobile inside the base unit (5).
Figure 4 is a representation of the base portion of the rail thermometer casing according to the invention accommodating the angled end of the rail thermometer within, the case at one end and the bell shaped structure at the other end.
Figure 5 is the bottom representation of the bell type sensing structure which comes in contact with the rail surface while recording temperature.
Figure 6 is a representation of the magnet used in the invention.
Figure 7 is a representation of the fastening means used to secure the bulb of the thermometer to the end acting as the sole interface between the thermometer bulb and the bell type sensing device. Detailed description of the invention
Ideally, for taking temperature readings of rail surfaces, it is imperative that the response time be (time taken for the thermometer to take on the final equilibrium temperature) be less than five minutes and the temperature shown within 2% of the actual temperature. At the same time any such temperature measuring device should also be easy of use, portable and lightweight.
In the device of the invention, the device is secured to the rail through a magnet. However, since the root cause of problems of low response time and easy breakability in the art is using the magnet as the conductive medium as well as the securing component, in the present device the magnet is not used as the conductive means and only as a securing (adhesive] component. The magnet is provided in a cavity in the bell shaped structure designed to accommodate the magnet. The said bell shaped structure has on its lower surface a sheet metal component secured such that the said component provides contact surface with the rail on one side and has a copper clip braced on the other side for gripping the bulb of the thermometer. By virtue of the bell shaped structure being composed of an insulating material (preferably plastic) it does not play any role in the rate of conduction of heat to the thermometer bulb. Thus, in a preferred
Embodiment while the magnet provides the required adhesion, the sheet metal part of the bell shaped structure provides heat conduction.
The bell shaped structure allows quick conduction of heat to the thermometer via the clip braced on it. The magnet is held in a separate cavity within the bell type sensor. While the magnet provides the required adhesion, the sensor provides the conductive interface. In a preferred embodiment, the housing of the bell type sensor itself acts as the conductive interface between the rail and the clip.
The conductive surface is insulated from the aluminum protective case in the aluminium version of the case by a plastic base which acts as a thermal insulator for the conductive surface. Thus the problem of heat loss due to heat transfer to the aluminium casing is avoided. Only two interfaces for conducting the heat are used, i) Rail to conductive surface.
ii) Clip (which is braced/soldered onto the heat conductive surface (sheet metal component) of the bell shaped structure) and the thermometer bulb. The presence of the gripping spring over the clip ensures that the thermometer bulb is firmly gripped in the clip and the contact surface area between the bulb and the clip is maximized to ensure..effective transfer of heat.
Both the clip and the bell shaped structure are made of sheet metal and designed to keep its mass and thickness to the barest minimum. This ensures that the heat up time of the conductive part is barest minimum. Hence the heat gradient is very small at all times leading to a quick
equilibrium temperature. This ensures a very quick response to temperature changes at the surface.
The thermometer and the device can be angled to ease taking readings from the thermometer while the device is still placed on the rail. This avoids heat loss/gain to atmospheric that occurs in prior art thermometers wherein removing the thermometer from the rail results in dissipation of heat into the atmosphere.
The magnet used can be any rare earth magnet instead of a strontium magnet as in the prior art. Rare earth magnets are advantageous over strontium magnets since they require no pole keepers, have a higher tolerance to heat before they j;et demagnetized and are more compact than a strontium magnet of the same strength.
The device of the invention results in a final reading wherein the margin is less than 2 % of the actual temperature of the rail. Due to insulation of the conducting parts, the device induces minimal changes in the temperature of the test surface. (Relevant in measuring temperature of smaller iron surfaces). The light weight nature of the device and its portability ensures its ease of use.
When the device and the thermometer are angled according to a preferred feature of the invention, it is no longer necessary for the measurement of the temperature to be done by either removing the thermometer from the rail and thereby breaking contact or by bending. The use of rare earth magnets as explained above also ensures that there is no need of pole keepers.
The Protective Cover
The components used in the protective cover are given in the Table 1 below:
The protective cover's purpose is to provide protection against direct physical impact/ shock to the .glass thermometer stem. Both the inner sheath (also called the sheath) and the rotary cover (cover) have windows on their front side with dimensions as shown in Figure 1. The purpose of these windows is that the graduation scale of the thermometer they encase is clearly visible.
The inner sheath has a hole in a section at its upper end where a spring can be placed and a steel ball as shown in figure 2 can be placed. The rotary cover has two holes in it at an angular distance. When the cover is pushed over the inner sheath, the locking ball locks into one of the two holes in the rotary cover. The rotary cover can be rotated freely over the inner sheath. However, the spring-loaded locking ball locks into one of the two holes when the rotary cover is rotated over the inner sheath forming two limiting positions. These two limiting positions correspond to an open
position (when the windows on the rotary cover and inner sheath overlap)
find a closed position (when the windows do not overlap and the rotary cover's window is aligned with the inner sheath's back).
The plastic base is molded from .glass filled Nylon and has dimension as shown in figure 4. Other hard and high impact plastics like HIPS, ABS etc. can also be used. It hast a neck that is at an angle of 30 degrees. The neck is angled to accommodate the angle in the thermometer as shown in figure 8. The neck has two steps on its outer side. The upper end has a tapping on it of size M10 such that the inner sheath can be screwed on to it. The rotary cover uses the lower neck for support during rotation.
The thermometer is first pushed into the plastic base and then the inner sheath is brought down to cover its stem. The base is then gently rotated such that the inner sheath gets screwed on to the base.
Together, when the five components are assembled, they form the protective cover for the thermometer. The sensor.
The bell shaped structure which also acts as the heat conducting component and hence acting as a sensor as shown in figure 4 is a brass/copper component designed to accommodate the plastic base (that is attached to it with the help of an adhesive) on one side and a housing for the permanent magnet on the other. A permanent magnet as shown in figure 5 is affixed with help of suitable adhesive in the said housing.
The bell shaped structure has been devised so that the contact surface and the magnet are all in the same linear plain. This ensures adequate contact surface area between the Tail and the sensor for effective heat transfer.
At the center of the sensor, a copper gripping clip as shown in figure 6 is braced on. The clip grips the thermometer bulb when the entire piece is assembled and thus provides adequate surface area for heat transfer to the bulb. The gripping spring as shown in figure 7 is pushed on to the clip to provide a tight fit of the clip over the thermometer bulb.
During assembly, The sensor is pushed on to the plastic base securing the thermometer bulb in the braced cojjper clip. A suitable adhesive is applied on the inner walls of the sensor prior to pushing it on to the plastic base.
The thermometer Usage:
The thermometer can be used to measure the temperature of any ferromagnetic flat surface quickly and accurately. It has been specifically designed keeping in mind the requirements of the railroads for track maintenance purposes. The thermometer is designed to give the track temperature with in five minutes of being brought into contact with the track.
The thermometer is paced on the track with its angle along the length of the track. If possible, ensure that the window of the thermometer does not face direct sunlight for better accuracy. The magnet will secure the thermometer to the track. Rotate the rotary cover, close the window of the cover. Leave the instrument for five minutes. After five minutes the rotary cover is opened and the temperature is taken. The thermometer should not be lifted off the track while taking the reading to ensure that the reading is not disturbed by air temperature.
The invention will now be explained with reference to the accompanying drawings, which are exemplary. It must be understood that different embodiments are possible within the scope and spirit of the invention and that the embodiments detailed herein are non-limiting.
As explained above, figure 1 is a representation of a rail thermometer according to the invention. As can be seen from the figure, the bell type sensing device (6) is in direct contact with the surface whose temperature is to be sensed through a contact surface (7). The bell type sensing means (6) is insulated from the casing of the rail thermometer by means of the base unit (5). The thermometer (11) is provided inside the base unit (5) and the rotating cover (2) thereby ensuring protection from damage. The rotating cover comprises of a fixed outer sheath and a moving inner sheath (1) which serves to act as a window to read the temperature measurement. The thermometer (11) has a bulb at one end and the other end thereof is fixed inside the cover by means of a locking ball (3). The bulb end of the thermometer (11) is fixed inside the base (5) by means of a adhesion means comprising a spring (10) and a gripping clip (9) which ensure that the bulb end of the thermometer is in direct contact with the temperature sensing means (7). When the rail thermometer is placed in contact with the surface whose temperature is to be read, the adhesive device comprising of a permanent magnet (8) firmly grips the contact surface. The temperature of the surface is transmitted by the surface (7) to the bulb without any dissemination to the atmosphere or to the cover thereby ensuring that the result obtained is substantially accurate without loss due to atmospheric dissipation of temperature.
Figure 2 is a representation of the casing for the rail thermometer according to the invention. The casing comprises of a fixed outer sheath and a moving inner sheath (1) which serves to act as a window to read the temperature measurement. The inner sheath is movably secured to the outer sheath. When the device is not in use, the window portion of the inner sheath is covered by the outer sheath. When in use, the inner sheath is twisted sideways to enable easy reading of the temperature measurement.
Figure 3 (a) is a representation of the spring locking ball used to secure the thermometer bulb according to the invention. Figure 3(b) is a representation of the spring gripping device which renders the thermometer immobile inside the base unit (5). The spring gripping device also enables easy transmission of the temperature from the temperature sensing means provided on the contact surface to the thermometer bulb without significant dissipation into the atmosphere or to the inner or outer sheath of the cover.
Figure 4 is a representation of the base portion of the rail thermometer casing according to the invention accommodating the angled end of the rail thermometer within, the case at one end and the bell shaped structure at the other end. The base portion is provided with an angled neck to accommodate the angle in the thermometer as shown in figure 1. The neck has two steps on its outer side. The upper end of the base has a tapping on it such that the inner sheath can be screwed on to it. The rotary cover uses the lower neck for support during rotation.
Figure 5 is the bottom representation of the bell type sensing structure which comes in contact with the rail surface while recording
temperature. The magnet is provided discrete from the contact surface thereby ensuring that heat loss is minimised.
Figure 6 is a representation of the magnet used in the invention.
Figure 7 is a representation of the fastening means used to secure the bulb of the thermometer to the end acting as the sole interface between the thermometer bulb and the bell type sensing device. The fastening means depicted comprises a clip member which is provided inside a spring gripping device to ensure that the fastening of the thermometer bulb is secure without substantial chance of damage to the bulb due to vibration.
As explained above, the embodiments specifically described are exemplary and should not be read to constitute a limitation on the scope of the invention. Variations are possible within the scope of the invention without departing from the spirit thereof.
1. A rail thermometer comprising a thermometer casing with a thermometer provided therein, said casing being provided at one end with an adhesive member to secure the said casing to the rail track, and a heat conducting means to transfer the heat from the rail to the thermometer bulb, said heat conducting means being connected to said thermometer inside said casing through a fastening means.
2. A rail thermometer as claimed in claim 1 wherein the fastening means
comprises a clip adaptable to secure the bulb end of the said
3. A rail thermometer as claimed in claim 1 wherein the heat conducting
means comprises a sheet metal plate provided in a bell type structure.
4. A rail thermometer as claimed in claim 3 wherein the heat conducting
means is insert molded into the bell type structure.
5. A rail thermometer as claimed in claim 1 wherein the adhesive member is
integral with said bell shaped structure while heat insulated therefrom by
6. A rail thermometer as claimed in claim 1 wherein the thermometer casing
is provided with a viewing means to view the temperature readings on the
7. A rail thermometer as claimed in claim 6 wherein the said viewing means
is provided with a moving means to move it from a first viewing position
to a second closed position.
8. A rail thermometer substantially as described hereinbefore and with
reference to the accompanying drawings.
|Indian Patent Application Number||710/DEL/2001|
|PG Journal Number||36/2008|
|Date of Filing||26-Jun-2001|
|Name of Patentee||PAWANDEEP SINGH BAHL|
|Applicant Address||1 FIRST FLOOR, ARAVALLI SHOPPING COMPLEX, ALAKNANDA, NEW DELHI-110 019, INDIA.|
|PCT International Classification Number||G01K 15/00|
|PCT International Application Number||N/A|
|PCT International Filing date|