Title of Invention

PEAK AIRFLOW INDICATOR

Abstract

Disclosed herein is a peak airflow indicator comprising a blow tube having a diameter of 10 to 40 mm and length of 10 to 40 mm, one end of the blow tube being fitted with a nozzle having an orifice whose open area diameter is in the range of 0.5 mm to 39 mm, the said nozzle having rounded entry and sharp exit edges, the blow tube being connected to a set of indicating tubes through a manifold, the indicating tubes being of various shapes but sealed from outside atmosphere, one end of the manifold being connected to the blow tube, without obstructing flow in the blow tube, the other end of manifold being connected to indicating tubes which are vertical in normal operation, the indicating tubes being made of transparent material with a diameter of 1 to 10 mm and a length of 5 to 50 mm with smooth and uniform bore, said indicating tubes being provided with pistons of different weights, the lower ends of the indicating tubes being vertically fixed to the manifold having stops to keep the pistons in position without significantly obstructing the flow in the tubes, the upper end of the indicating tubes being designed to keep the pistons from leaving the open ends of the tubes without obstructing the flow and maintaining the communication of pressure, the indicating tubes being provided with pistons having two discs, which are connected with a rod carrying weights.

Full Text

FIELD OF INVENTION The invention pertains to instrumentation technology. The present invention pertains to an instrument for indicating peak airflow with specific application for planning medical treatment of respiratory obstruction due to Asthma and other causes. More particularly this invention relates to a novel peak airflow indicator. The present invention pertains to an instrument for the indication of peak expiratory airflow of lungs for monitoring the status of obstruction and to plan their medication. The instrument consists of a blow tube one end of which fits the tube. To the other end of the blow tube is fitted a nozzle of suitable size which raises the pressure inside the blow tube to an extent depending on the flow in the blow tube. The increase in pressure in the blow tube is communicated to one or more vertical indicating tubes through a connecting manifold. The indicating tubes carry pistons of carefully chosen weights such that each piston lifts off at specific pressure corresponding to a specific flow in the blow tube. By carefully choosing the nozzle, the number and weight (4) of pistons as well as other geometrical parameters of the instrument, it can be so arranged that a specific flow in the blow tube can be bracketed by the lifting of a piston in one indicating tube and by non-lifting of the piston in the next tube. The principle of operation and construction of a practical instrument based on the principle are described. BACKGROUND A fairly large fraction of the general population all over the world experience breathing difficulty occasionally/regularly associated with allergic reaction to inhalants like pollen, fungal spores, mites, insects, dust and/or other environmental pollutants. In these cases there is constriction of bronchial passages and treatment of the condition is by the use of bronchodilators and other anti-inflammatory drugs. But a measure of the obstruction is required for planning the medication. Instruments by the name of peak flow meters are currently in use for these purposes. (Example, see British Patent Specification 1463814). These employ a mouthpiece of some kind in conjunction with a spring-loaded piston in which one blows. The instrument provides a quantitative measure of the peak airflow. These instruments are expensive and are not satisfactory for the use by patients like children or illiterate adults who do not have adequate skill to read such instruments. Consequently, these instruments are not suitable for planning self-medication by a large class of users. The current invention overcomes these deficiencies by providing go-no-go type indication and is also cheaper to produce. DESCRIPTION OF PRIOR ART Previous designs of peak air flow meters, which the current invention improves upon, generally employ a mouthpiece mto which the patient empties his lungs rapidly so as to provide the highest peak airflow rate. The au" blown Into the mouthpiece esc^es through a slit of constant or variable width, which is progressively uncovered by a spring, loaded piston. The piston moves due to the increase in pressure in the cylinder in which the piston moves. The movement of the piston is recorded by an index whose position on a scale is an indication of peak akflow. For accurate indication of auflow, the spring controlling the movement of the piston must have a precise spring rate. This problem is overcome in the present invention which employs precisely calibrated dead weights which also act as pistons in the indicating tubes. The present invention also makes other improvements, which make it suitable for children and illiterate users. In the accompanying drawings: Fig -1 illustrates the peak air flow indicator of the present invention; and Fig -2 is an enlarged view of the piston. SUMMARY OF INVENTION The main features of the invention are indicated in Fig. 1. The instrument consists of a blow tube (1) with a nozzle (5) at the free end. The blow tube (1) is cormected by a manifold (2A-2B) to a set of indicating tubes (7) of the same or different diameters m which move pistons (3) of different weights (4). These being provided with appropriate steps, when there is a flow in the blow tube (1), there is a corresponding increase in pressure in the blow tube (1) over ambient. This increased pressure is indicated by the lifting up of pistons (3) of below a certain weight (4) in one or more of indicating tubes (7). By carefully choosing the dimensions of the instrument including diameters of the blow tube (1), indicating tubes (7), piston weights (4) and nozzle area, it is possible to closely bracket any given peak flow by the lifting one or more pistons (3) and not lifting of one or more pistons in the indicating tubes. DEATILED DESCRIPTION OF THE INVENTION Now the invention will be described in detail with reference to drawings, as those left with the provisional specification wherein the Fig-1 is a sketch of the peak airflow indicator. The instrument typically consists of a blow tube (1) of about 10 to 40 mm in diameters and 10-40cms long. The subject using the instrument draws a deep breath and empties his lungs in one long puff of blowing through one end of the blow tube. To the other end of the blow tube is fixed a nozzle provided with orifice whose open area can be selected depending on the range of airflows to be indicated. Typically it is about 10mm in diameter. But replaceable nozzles with orifices of 0.5 to 30 mm can be provided. The nozzle creates an increased pressure in the blow tube the increase being approximately proportional to the square of the airflow rate. This increased pressure is communicated to a number (typically four) of indicating tubes (7) by a connecting manifold (2A-2B). The connectmg manifold (2A-2B) is connected to the blow mbe using a flush connection such that the flow in the blow tube is not disturbed by the manifold (2A-2B), but only the static pressure in the blow tube is communicated to the manifold (2A-2B). The vertical (or nearly vertical) indicating tubes (7) connected to the manifold (2A-2B) carry very nearly airtight pistons (3) of precisely adjusted weights (4) which can move without friction up and down along the indicating tubes (7). A typical design of the pistons (3) is shown in Fig-2. Each piston consists of two discs spaced apart fi-om a threaded rod, which carries weights (4) in the form of metal washers. As the top end of the indicating tubes (7) are communicating to atmosphere while the lower ends are connected to the manifold (2A-2B), the pistons (3) are subjected to an upward force proportional to the increase in the pressure in the blow tube (1). Normally, the pistons (3) rest at the bottom of the indicating tubes (7) and rest on stops provided. But when the pressure in the manifold (2A-2B) increases sufficiently, the weight (4) of a piston is overcome by the upward force due to pressure in the manifold (2A-2B) and that the piston lifts off and with further rise in manifold (2A-2B) pressure moves up and stops against a stop provided. Even a slight movement of the piston upwards indicates that a certain definite pressure has been exceeded in the manifold (2A-2B) and this corresponds to a definite flow bang exceeded in the blow tube (1). A similar piston movement takes place in each of the four indicating tubes (7). Bu the weights (4) of the pistons (3) are different in different tubes (typically arranged in a monotoracally increasing order corresponding to flow in the blow tube (1) being the ratio of 0.3:0.5:0.8:1 for a four tube instrument). Thus, as the flow in the blow tube (1) is progressively increased, the pistons (3) in the indicating tubes (7) lift off progressively starting from the lightest piston. Thus, any particular flow is bracketed by the lifting off the pistons (3) corresponding to that flow or lower and not lifting of other (heavier) pistons (3). The same behavior is maintained even when flow in the blow tube (1) is a puff of a certain peak value. However, in this case, the pistons that lift off during the puff, return after the puff is past. But an observo- can easily infer, by watching the movement of the pistons, whether a certain flow has been exceeded during the puff. It is to be noted that the object of the invention is to explain salient features of the invention. It is to be further noted that the description is m now way restrictmg the scope of die invention. It is to be understood that with in the scope of the invention, various amendments and modifications are permissible. The scope of the claims is described in the following description. I CLAIM: 1. Peak airflow indicator comprising a blow tube having a diameter of 10 to 40 mm and length of 10 to 40 mm, one end of the blow tube being fitted with a nozzle having an orifice whose open area diameter is in the range of 0.5 mm to 39 mm, the said nozzle having rounded entry and sharp exit edges, the blow tube being connected to a set of indicating tubes through a manifold, the indicating tubes being of various shapes but sealed firom outside atmosphere, one end of the manifold being connected to the blow tube, without obstructing flow in the blow tube, the other end of manifold being connected to indicating tubes which are vertical in nonnal operation, the indicating tubes being made of transpareat material with a diameter of 1 to 10 mm and a length of 5 to 50 mm with smooth and uniform bore, said indicating tubes being provided with pistons of different weights, the lower ends of the indicating tubes being vertically fixed to the manifold having stops to keep the pistons in position without significantly obstructing the flow in the tubes, the upper end of the indicating tubes being designed to keep the pistons from leaving the open ends of the tubes without obstructing the flow and maintaining the communication of pressure, the indicating tubes being provided with pistons having two discs, which are connected with a rod carrying weights. 2. Peak airflow indicator as claimed in claim 1, wherein the piston consists of two discs spaced apart by a threaded rod, said rod carrying the weights in the form of metal washers. 3. Peak airflow indicator as claimed in claim I, wherein the weights provided on the pistons are different in different tubes, which is progressively increased corresponding to the flow in the blow tube. 4. Peak air flow indicator as claimed in claim 1, wherein the weights are in the ratio of0.3:0.5:0.8:l for a four tube mstrument. 5. Peak airflow indicator as claimed in claim 1, wherein the pistons are of different colours for convenient interpretation of flow indication. 6. Peak airflow indicator as claimed in claim 1, wherein the said instrument is being made of transparent and/or opaque materials such as acrylic, poly vinyl chloride or other polymers.

Documents:

500-mas-99 abstract duplicate.pdf

500-mas-99 abstract.pdf

500-mas-99 claims duplicate.pdf

500-mas-99 claims.pdf

500-mas-99 correspondence others.pdf

500-mas-99 correspondence po.pdf

500-mas-99 description (complete) duplicate.pdf

500-mas-99 description (complete).pdf

500-mas-99 drawing duplicate.pdf

500-mas-99 drawing.pdf

500-mas-99 form-1.pdf

500-mas-99 form-13.pdf

500-mas-99 form-19.pdf

500-mas-99 form-26.pdf

500-mas-99 form-5.pdf