A FLOW INDICATOR FOR OXYGEN ADDITION TO REBREATHING SYSTEMS

Abstract

The invention relates to a flow indicator preferably to be used in oxygen therapy treatment of patients where a clear flow or no flow state must be signaled for the supply of oxygen.

According to the inventive flow indicator are two cylindrical bodies used, one (30) movable and one (10) stationary, and with one extended flow restriction passage (80) that forces the movable cylindrical body away from a sight glass (40), instead exposing the stationary cylindrical body. The viewable cylindrical part of the movable part may be colored red (R), and the viewable cylindrical part of the stationary body may be colored green (G).

A flow indicator with quick and stable indication of developed flow is obtained.

Claims

1. A flow indicator for indicating developed flow of oxygen into rebreathing systems comprising an elongated flow indicator housing with an oxygen inlet in one end and an oxygen outlet in the other end of the elongated flow indicator housing and with at least a part of the elongated flow indicator housing made in a transparent material enabling visualization of at least a part of the flow channel through said elongated flow indicator housing, and a movable indicator body located inside of said elongated flow indicator housing; a bias member with one end fastened to a stationary anchor of the elongated flow indicator housing and the other end fastened to an anchor of the movable indicator body, which bias member apply a force to the movable indicator body towards a closing seat preventing flow through the flow indicator housing, and when oxygen pressure is applied to the oxygen inlet in said flow indicator housing is the movable indicator body pushed away from the closing seat allowing passage of oxygen flow, wherein an axially directed flow restriction passage is arranged in a coaxial fashion between a stationary cylindrical part of the elongated flow indicator housing and a complementary cylindrical part of the movable indicator body, said flow restriction passage in one end connected to an inlet chamber in turn connected to the oxygen inlet and in the other end connected to an outlet chamber in turn connected to the oxygen outlet, and with the closing seat arranged between an axially facing surface of the stationary part of the elongated flow indicator housing and an axially facing surface of the movable indicator body.

2. A flow indicator according to claim 1, wherein the part of the elongated flow indicator housing made in a transparent material has an axial extension over the flow indicator housing from the first axial position of the closing seat, close to one of the inlet or outlet ends, to an axially distant second position closer to the other inlet or outlet end, with a distance between said first and second positions exceeding at least 50% of the axially length of the flow restriction passage.

3. A flow indicator according to claim 2, wherein the distance between said first and second positions exceeds at least 75% of the axially length of the flow restriction passage.

4. A flow indicator according to claim 1, wherein the movable indicator body is displaceable by the developed flow of oxygen to an axial position away from the part of the elongated flow indicator housing made in a transparent material, and with the outer part of the movable indicator body preferably being colored in a first signal color, signaling said first signal color through the transparent part of the housing when no flow of oxygen is developed, and when displaced from the part of the elongated flow indicator housing made in a transparent material when oxygen flow is developed instead expose a second signal color through the transparent part of the housing.

5. A flow indicator according to claim 4, wherein the movable indicator body is shaped as a cylinder closed in one end and in the other open end of the cylinder comprise the axially facing surface that forms the closing seat, and with an axial length of the cylinder exceeding that of the axial length of the part of the elongated flow indicator housing made in a transparent material, and with the outer cylindric surface of the movable indicator body preferably colored in red.

6. A flow indicator according to claim 5, wherein a stationary inner cylinder is located coaxially of the movable indicator body, which inner cylinder also has an axial length of the cylinder exceeding that of the axial length of the part of the elongated flow indicator housing made in a transparent material, and with the outer cylindric surface of the stationary inner cylinder preferably colored in green.

7. A flow indicator according to claim 1, wherein the axially directed flow restriction passage has a progressively increasing flow area as the movable indicator body lifts from the closing seat.

8. A flow indicator according to claim 7, wherein the axially directed flow restriction passage is arranged in a coaxial fashion between a stationary cylindrical part of the elongated flow indicator housing and a complementary cylindrical part of the movable indicator body, and said flow passage shows a step wise increase of flow area as the movable indicator body lifts from the closing seat, and wherein each step of flow increase is developed over an axial length of the axial flow restriction passage exceeding 10%, preferably 20%, of the total length of the axial flow restriction passage.

9. A flow indicator according to claim 1, wherein the part of the elongated flow indicator housing made in a transparent material runs over the entire circumference of the elongated flow indicator housing, exposing the outer surface of the movable indicator body or alternatively the outer surface of the stationary inner cylinder, depending on developed flow of oxygen and hence the axial position of the movable indicator body.

10. A flow indicator according to claim 1, wherein the axial length of the part of the elongated flow indicator housing made in a transparent material is at least 10 mm long, with the axial length of the outer surface of the movable indicator body and the outer surface of the stationary inner cylinder as well as the flow restriction passage, all exceeding the axial length of the part of the elongated flow indicator housing made in a transparent material.

Description

LIST OF DRAWINGS

[0032] In the following schematic drawings may same details not be numbered in additional figures.

[0033] FIG. 1; Show an assembled flow meter according to the invention in a cross section view;

[0034] FIG. 2; Show the stationary cylindrical insert as such;

[0035] FIG. 3; Show the movable cylindrical insert as such;

[0036] FIG. 4a; Show the stationary and movable cylindrical inserts in a no flow state;

[0037] FIG. 4b; Show the stationary and movable cylindrical inserts in a fully developed flow state;

[0038] FIG. 5a; Show a side view of the flow indicator in a no flow state;

[0039] FIG. 5b; Show a side view of the flow indicator in a fully developed flow state;

[0040] FIG. 6; Show an alternative embodiment of the flow restriction passage between the two cylindrical inserts.

DETAILED DESCRIPTION OF THE INVENTION

[0041] In FIG. 1 is shown the inventive flow indicator in a cross section view when installed in an oxygen supply hose 21.

[0042] The flow indicator housing 1 is in this embodiment manufactured and mounted in an oxygen supply hose 21 by assembly of only 10 different parts; i.e. [0043] A single flow channel housing 4, preferably made in one piece of transparent material such as carbonate plastic; [0044] Two end pieces, an upper and lower end piece, 2.sub.U and 2.sub.L respectively; Said end pieces attached to the flow channel housing by threads 42.sub.U, 42.sub.L engaging threads 41.sub.U, 41.sub.L on the flow channel housing. The end pieces integrated with an upper and lower hose nipple 20.sub.U and 20.sub.L. [0045] Two standard O-ring seals 5.sub.U and 5.sub.L providing a pressure seal between the flow channel; [0046] a stationary cylindrical part 10 of the elongated flow indicator housing, in this embodiment made as a separate part. [0047] a movable indicator body 30; and [0048] a bias member 60, and [0049] finally, 2 hose clamps 22.sub.U and 22.sub.L providing a closing force on the hose towards the hose nipples.

[0050] The flow indicator hosing 1 has an oxygen inlet 70 through the hose nipple 20.sub.U in the upper end, in turn connected to an inlet chamber 50, and an oxygen outlet 71 through the hose nipple 20.sub.L in the lower end, in turn connected to an outlet chamber 51. The bias member 60, here a coil spring, is connected In one end to a stationary anchor 11 and in the other end to a movable anchor integrated with the movable indicator body. As long as the inlet chamber is not pressurized with oxygen is a sealing seat S developed between the stationary cylindric insert 10 and the movable indicator body 30, preventing flow through the flow indicator.

[0051] The stationary cylindrical part 10 of the elongated flow indicator housing, in this embodiment made as a separate part, is shown separately in FIG. 2. The essential cylindrical part that aligns with the transparent 40 part of the housing is the lower part 92. The outer surface 92 is preferably given a distinctive signal color, preferably green, as this entire surface is intended to be seen when flow of oxygen is developed. The part of the stationary cylindrical part 10 that form the sealing S is the axially facing shoulder S.sub.S. An anchor 11 for the bias member, i.e. a coil spring end, is provided in form of a pin 11 running across the inlet chamber 50.

[0052] The movable indicator body 30 is shown separately in FIG. 3. The essential cylindrical part that aligns with the transparent part 40 of the housing is the outwardly facing surface 91. The outer surface 91 is preferably given a distinctive signal color, preferably red, as this surface is intended to be seen when no flow of oxygen is developed, and the movable indicator body settles with the circular end face S.sub.M on the axially facing shoulder S.sub.S of the stationary part. An anchor for the bias member, i.e. a coil spring end, is provided in form of a pin or a hook 31 mounted close to the closed gable end 33. The movable indicator body may also be provided with at least one smaller end projection 34 that prevents the closed gable end 33 to cover and close the oxygen outlet 71 from the outlet chamber 51.

[0053] The interplay between the stationary cylindrical part 10 of the elongated flow indicator housing and the movable indicator body 30 is shown in FIGS. 4a and 4b, where FIG. 4a show the relative positions between these parts 10/30 as well as the transparent part of the flow indicator housing 40 in a no flow state, and FIG. 4b show the relative positions between these parts 10/30/40 in a fully developed flow state.

[0054] When no flow is developed, which may occur if the inlet chamber is not connected to a pressurized oxygen source or if the outlet channel 71 is blocked, the movable indicator body 30 will settled down on the sealing seat S by the action of the bias member 60. The outer surface R of the movable indicator body 30 is then seen through the transparent part of the flow indicator housing 40. In this starting position is a flow restriction passage 80 formed between the outer surface of the stationary cylindrical part 10 and the inner cylindrical surface of the movable indicator body 30.

[0055] When the inlet chamber 50 is connected to a pressurized oxygen source is the oxygen pressure at the inlet pressure applied onto the gable end 33 of the movable indicator body 30, and thus push the body 30 downward opening the passage through the sealing seat S. The flow of oxygen must pass the flow restriction passage 80 before passing the sealing seat S and is therefore subjected to pressure drop. The pressure in the outlet chamber 51, i.e. working on the other side of the gable end 33, will be lower than the pressure in the inlet chamber 50. The order of pressure drop established in the flow restriction passage is directly related to the gap in the passage 80. In FIG. 4b is shown the end position of the movable indicator body 30 when oxygen flow is established. This position will be kept as long as flow is developed, but as soon as flow is interrupted will the pressure on both sides of the closed gable end 33 assume same pressure, and the bias member will return the movable indicator body towards the position shown in FIG. 4a.

[0056] In FIG. 5a is shown a side view of the flow indicator in a no flow state, where the outer surface of the movable indicator body 30 Is viewable through the transparent part 40 of the flow indicator housing 1. In FIG. 5b is shown a side view of the flow indicator in a developed flow state, where the outer surface of the stationary cylindrical part 10 is viewable through the transparent part 40 of the flow indicator housing 1. As seen from previous figures is the diameter D.sub.R (signaling “Red” in no flow state) slightly larger than the diameter D.sub.G (signaling “Green” in a developed flow state).

[0057] In FIG. 6 is an alternative configuration of the flow restriction passage 80 disclosed, which in contrast to previous embodiments do not have a constant gap in the flow restriction passage 80 over the entire stroke of the movable indicator body 30, but instead Is designed with a progressively increasing gap in the flow restriction passage 80. In this embodiment is the flow restriction passage designed with stepwise increase of gap in 4 stages and on both cylindrical surfaces of the movable indicator body 30 as well as the stationary cylindrical part 10. In this figure is the order of gap increase exaggerated and the step wise increase may be obtained from surface modification of only one surface and not both as shown here.

[0058] The cross section of the flow restriction passage 80 in the alternative with a constant gap size over the stroke length, is considerably smaller than the flow area through the hose 21 and the hose nipple and other flow sections in the flow indicator. Assuming that a hose 21 with a flow area of about 5 mm is used, then the flow restriction passage should have a total flow area of less than 50% of the hose, preferably less than 10-25% of the flow area of the hose. This narrow flow restriction passage may easily be machined to size in the two cylindrical parts, i.e. the movable indicator body 30 and the stationary cylindrical insert 10, or alternatively between the inside surface of the flow channel housing 4 and the outer surface of the movable indicator body 30.

[0059] Hence, in a total flow area in the flow restriction passage with a constant gap size may lie between 0.3-1.5 mm.sup.2. When using a hose with a flow area of 3 mm.sup.2. total flow area in the flow restriction passage with an increasing gap size, as shown in FIG. 6, may change gap size in steps between 0.3-1.5 mm.sup.2 when using a hose with a flow area of 3 mm.sup.2, wherein each step wise increase may lie in the order of 0.1-0.3 mm.sup.2.