GB2177209A - Barographs - Google Patents

Abstract

The recording means of a barograph comprises heat sensitive paper 13 and a stylus 11 carrying a heating coil 26. Heat is produced by periodic discharge via capacitor 16. The barograph is intended to operate over periods up to 1 year. Time and a portion of the paper are displayed. <IMAGE>

Description

SPECIFICATION This invention relates to an improved barograph The traditional Barograph, consisting of a 7 day clock driven chart drum, with associated aneroid movement and pen arm, traces a 7 day graphical record of barometric pressure.

Such instruments have inherent disadvantages, which include the necessity to change the chart weekly, involving particularly dismantling the instrument, inking the pen and winding the clock. A particular disadvantage for Marine use is the inherent sensitivity to vibration. Also, chart papers are difficult to obtain, except from the manufacturer of the instrument, since there is no standardisation in the size of chart drums.

According to the present invention there is provided a Barograph, using thermal paper rolls of standard type internationally available, so as to provide a barometric record for over one year unattended.

Further advantages of the invention include a high immunity to shock, vibration and lateral acceleration, higher accuracy as a result of complete detachment of the Aneroid sensor during the process of measurement, and the employment of thermal paper precludes the necessity for ink. A clock display of navigational accuracy is also provided.

A specific embodiment of the invention will now be described by way of example, with reference to the accompanying drawings in which: Figure 1 Shows, in perspective, the complete Barograph.

Figure 2 Illustrates the parts comprising the system, together with associated electrical system.

Figure 3 Shows the stylus assembly 11, together with stylus contact arm 19 for clarity.

Figure 4 Shows a timing diagram of the system operation.

Referring to the drawing shown in Fig. 2, the hour, minute and second hands 3.2.1, are affixed to the clock movement 5 in a conventional manner. Also affixed to the clock hour shaft is a pulley 23, which is coupled by belt to a further pulley 10, which is secured to the paper drive roller shaft 21, with idler pulley 9 assisting the right angle configuration of the belt drive. The paper chart 13 is held to the paper drive roller 21 by the spring loaded rubber covered pinch roller 22, the diameter of paper drive roller 21 is chosen so as to feed the paper chart 13 downwards at a rate of 1;5 inches per 24 hours. Pulleys 9, 10 and 23 may be replaced by gearing if so desired.

Affixed to the minute hand shaft of clock movement 5, is a transparent plastic cam 4, which allows the clock to be viewed, whilst pulley 23 is hidden behind the clock dial, which for clarity in Fig. 2 has been omitted.

This cam 4 is so profiled as to provide four quarter-hour sections, each containing a linear fall of approximately three minutes, followed by a rise during the next twelve minutes. Cam follower shaft 6, supported by insulated plastic bearings 20-29 carries, at the front end, the cam follower arm 7, and in line with the pivot axis of the Aneroid Barometer movement 12, the stylus contact arm 19, with its associated leaf spring 24.

Hence the clock, apart from advancing the paper downwards in a linear manner, also causes cam 4 to rotate once per hour, causing a relatively fast fall of contact arm 19, over about three minutes, followed by a rise for the remaining twelve minutes, repeated four times per hour.

As contact arm 19 falls, under pressure from leaf spring 8, leaf spring 24 depresses the stylus arm assembly 11, until the associated heat coil 26 is firmly in contact with the paper over platen 23, this operation taking about one and a half minutes. A further one and a half minutes of fall continues, resulting in contact arm 19 carrying contact 28 being brought firmly onto contact 27 on stylus arm assembly 11, which in turn, is connected by a fine wire to the heat coil 26. Closure of these contacts results in the discharge of Electrolytic Capacitor 16 across the heat coil, over a duration of several milliseconds, hence marking the paper.

Thus a graph is produced, formed by a chain of heat marks giving the appearance of an unbroken line, and representing barometric pressure measured by Aneroid unit 12.

Capacitor 16 is charged by resistor 17 connected to battery 18, and since contacts 27-28 previously described are normally open for a large part of each quarter hour cycle of cam rotation, resistor 17 is chosen as the highest resistive value that permits capacitor 16 to be recharged in sufficient time for the next quarter hour of operation, thus minimising battery consumption.

Aneroid unit 12 and stylus arm 11 remain free of contact arm 19 for a considerable part of each quarter hour cycle, hence the accuracy of aneroid unit 12 is not adversely affected.

A transparent plastic graticule 25 is fitted in front of the paper chart so that the preceding forty-eight hours of barometric pressure may be examined in detail.

Stylus assembly 11 is designed so as to be of very light weight, and is statically balanced in order to reduce the effects of shock, vibration and lateral acceleration.

1. A Barograph comprising visual clock display with associated continuous running chart display, using a capacitor discharge and heat coil with the mechanical arrangements previously described, using Thermal Paper, and capable of greater than one year of unat

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION This invention relates to an improved barograph The traditional Barograph, consisting of a 7 day clock driven chart drum, with associated aneroid movement and pen arm, traces a 7 day graphical record of barometric pressure. Such instruments have inherent disadvantages, which include the necessity to change the chart weekly, involving particularly dismantling the instrument, inking the pen and winding the clock. A particular disadvantage for Marine use is the inherent sensitivity to vibration. Also, chart papers are difficult to obtain, except from the manufacturer of the instrument, since there is no standardisation in the size of chart drums. According to the present invention there is provided a Barograph, using thermal paper rolls of standard type internationally available, so as to provide a barometric record for over one year unattended. Further advantages of the invention include a high immunity to shock, vibration and lateral acceleration, higher accuracy as a result of complete detachment of the Aneroid sensor during the process of measurement, and the employment of thermal paper precludes the necessity for ink. A clock display of navigational accuracy is also provided. A specific embodiment of the invention will now be described by way of example, with reference to the accompanying drawings in which: Figure 1 Shows, in perspective, the complete Barograph. Figure 2 Illustrates the parts comprising the system, together with associated electrical system. Figure 3 Shows the stylus assembly 11, together with stylus contact arm 19 for clarity. Figure 4 Shows a timing diagram of the system operation. Referring to the drawing shown in Fig. 2, the hour, minute and second hands 3.2.1, are affixed to the clock movement 5 in a conventional manner. Also affixed to the clock hour shaft is a pulley 23, which is coupled by belt to a further pulley 10, which is secured to the paper drive roller shaft 21, with idler pulley 9 assisting the right angle configuration of the belt drive. The paper chart 13 is held to the paper drive roller 21 by the spring loaded rubber covered pinch roller 22, the diameter of paper drive roller 21 is chosen so as to feed the paper chart 13 downwards at a rate of 1;5 inches per 24 hours. Pulleys 9, 10 and 23 may be replaced by gearing if so desired. Affixed to the minute hand shaft of clock movement 5, is a transparent plastic cam 4, which allows the clock to be viewed, whilst pulley 23 is hidden behind the clock dial, which for clarity in Fig. 2 has been omitted. This cam 4 is so profiled as to provide four quarter-hour sections, each containing a linear fall of approximately three minutes, followed by a rise during the next twelve minutes. Cam follower shaft 6, supported by insulated plastic bearings 20-29 carries, at the front end, the cam follower arm 7, and in line with the pivot axis of the Aneroid Barometer movement 12, the stylus contact arm 19, with its associated leaf spring 24. Hence the clock, apart from advancing the paper downwards in a linear manner, also causes cam 4 to rotate once per hour, causing a relatively fast fall of contact arm 19, over about three minutes, followed by a rise for the remaining twelve minutes, repeated four times per hour. As contact arm 19 falls, under pressure from leaf spring 8, leaf spring 24 depresses the stylus arm assembly 11, until the associated heat coil 26 is firmly in contact with the paper over platen 23, this operation taking about one and a half minutes. A further one and a half minutes of fall continues, resulting in contact arm 19 carrying contact 28 being brought firmly onto contact 27 on stylus arm assembly 11, which in turn, is connected by a fine wire to the heat coil 26. Closure of these contacts results in the discharge of Electrolytic Capacitor 16 across the heat coil, over a duration of several milliseconds, hence marking the paper. Thus a graph is produced, formed by a chain of heat marks giving the appearance of an unbroken line, and representing barometric pressure measured by Aneroid unit 12. Capacitor 16 is charged by resistor 17 connected to battery 18, and since contacts 27-28 previously described are normally open for a large part of each quarter hour cycle of cam rotation, resistor 17 is chosen as the highest resistive value that permits capacitor 16 to be recharged in sufficient time for the next quarter hour of operation, thus minimising battery consumption. Aneroid unit 12 and stylus arm 11 remain free of contact arm 19 for a considerable part of each quarter hour cycle, hence the accuracy of aneroid unit 12 is not adversely affected. A transparent plastic graticule 25 is fitted in front of the paper chart so that the preceding forty-eight hours of barometric pressure may be examined in detail. Stylus assembly 11 is designed so as to be of very light weight, and is statically balanced in order to reduce the effects of shock, vibration and lateral acceleration. CLAIMS

1. A Barograph comprising visual clock display with associated continuous running chart display, using a capacitor discharge and heat coil with the mechanical arrangements previously described, using Thermal Paper, and capable of greater than one year of unat tended operation.

2. A Barograph as claimed in Claim 1, but employing gearing instead of a belt drive, coupling the clock to paper drive roller.

3. A Barograph, as claimed in Claim 1 or 2, but without the visual clock display.

4. A Barograph as claimed in any preceding claim, but employing any type of electric, electronic or mechanical clock movement.

5. A Barograph, as claimed in any preceding claim, but employing any form of aneroid movement.

6. A Barograph substantially as described herein, with reference to Figs. 1-4 of the accompanying drawings.