Pneumotach

• US 5,060,655 A
• Filed: 11/15/1988
• Issued: 10/29/1991
• Est. Priority Date: 11/15/1988
• Status: Expired due to Fees

• Current Assignee: Hans Rudolph, Inc.
• Original Assignee: Hans Rudolph, Inc.
• Inventors: Rudolph, Kevin A.
• Primary Examiner(s): Burr, Edgar S.
• Assistant Examiner(s): Lewis, Aaron J.
• Application Number:
  US07/271,607
• Time in Patent Office: 1,078 Days
• Field of Search: 128/716, 128/725, 73/861.52, 73/3
• US Class Current: 600/529
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: G01F 1/40 Details of construction of the flow constriction devices

Abstract

A pneumotach apparatus for measuring gas flows comprises a flow head with a passageway and having a plurality of screens positioned in the pasageway to provide a variance in pressure on different sides of one of the screens, a pressure transducer to convert the pressures into a flow value and a display or recorder for conveying the pressure readings to an operator. The apparatus includes improved seals between the screens, improved seals between pressure taps and the screens, improved sealing between a mounting plate for the taps and a housing for the screens, and knife edges on tube adaptors for the housing that are positioned in close proximity to the screens to improve the accuracy of flow measurements taken by the apparatus.

Claims

1. In a pneumotach apparatus for measuring flows of gases and including a head having a flow passageway therethrough with a pair of hose receiving tube adaptors extending outwardly from opposite ends thereof and a plurality of flow measuring foraminous members positioned so as to extend across the passageway, the improving comprising wherein:

(a) each of said tube adaptors has a passageway passing therethrough;

each of said passageways having an inner end and an outer end;

(b) both of said tube adaptor passageway inner ends terminating in a circular knife edge surrounding both of said passageway and the gas when passing through said passageway;

(c) each of said passageway inner ends being in a plane positioned so as to be parallel to and less than 30 thousands of an inch from a respective one of said foraminous members, so as to reduce gaseous turbulence at said foraminous members.

2. The apparatus according to claim 1 wherein:

(a) each of said tube adaptors respective inner ends is positioned within 0 to 2 thousands of an inch from a respective foraminous member on opposite sides of said head.

3. In a pneumotach apparatus having a flow head with at least one foraminous member extending across a passageway through said head wherein said foraminous member has an outer annular ring with a bore passing radially therethrough and said head having an aperture receiving a tap and extending from outside said head to said bore, the improvement comprising:

(a) sealing means between a lower planar surface of said tap and an outer curved surface of said bore;

said bore curved surface having a radius of curvature aligned perpendicular to said lower planar surface;

said sealing means comprising an elongate sealing sleeve slidably mounted on said tap at a first end of said sleeve such that said sleeve snugly seals about said tap;

said sleeve being constructed of a flexible and rubbery material;

said sleeve having a second end flexibly engaging said outer curved surface of said annular ring so as to be aligned generally axially with respect to a radius of said curved surface and to seal about said bore whereby said sleeve snugly seals about both said curved outer surface and said planar surface.

4. The apparatus according to claim 3 wherein:

(a) said sleeve having a elongate annular shape and being constructed of a relatively low durometer silicone rubber such that, when said head is assembled, said sleeve compresses and forms a sealed channel between said tap and said bore to substantially prevent leakage therefrom.

5. In a pneumotach apparatus comprising a flow head having a housing with a passageway passing through said housing and a plurality of foraminous members mounted in said passageway and including at least a pair of outer annular rings;

the improvement comprising;

(a) sealing means extending between said pair of said rings and directly engaging both of said pair of rings entirely around facing surfaces associated with each of said rings to prevent leakage of gases therebetween.

6. The apparatus according to claim 5 wherein:

(a) said sealing means comprises a slot in a face of at least one of said annular rings;

said slot receiving therein an O-ring sized to be compressed when said head is assembled.

7. A pneumotach apparatus comprising:

(a) a generally annular housing having a first passageway therethrough;

(b) at least two screen members mounted within said first passageway such that gaseous flow through said first passageway passes through said screen members;

each of said screen members including a screen attached to an outer annular ring and forming at least one chamber therebetween;

a first of said annular rings including a radially extending bore therethrough communicating directly with said chamber;

(c) said hosing including a tap mounting plate integrally mounted on said housing so as to prevent leakage therebetween;

said tap mounting plate including a tap mounted in an aperture passing through said housing;

said tap being aligned to be generally coaxial with said bore;

said tap having a generally planar first end in close proximity to said bore;

a sealing sleeve sleeved on said tap end;

said sealing sleeve being axially elongate and generally annular in shape and being constructed of a relatively low durometer material;

said sleeve having a first end sealably engaging said tap planar first end;

said first annular ring having an exterior curved surface with a radius of curvature perpendicular to said planar surface;

said sleeve being rubbery and flexible such that upon placement of said tap into said housing said sealing sleeve is depressed and seals between both said tap and said curved surface of said annular ring having said bore therein and so as to form a sealed flow channel therebetween and to allow flow of gases between said bore and said channel without leakage therefrom;

(d) at least one of said screen member rings having a face facing at least one of the housing or a second of said screen member rings;

said face having a circular slot therein;

an O-ring positioned in said slot and being sized such that when said apparatus is assembled, said O-ring extends between and engages both said first ring and either said second annular ring or said housing; and

(e) first and second tube adaptors;

said first and second tube adaptors being sealably secured to said housing on opposite sides of said housing;

said first and second tube adaptors having second and third passageways therethrough respectively that are aligned with said first passageway each having an inner end terminating with 30 thousands of an inch of respective opposed screen members;

each of said first and second passageways inner ends terminating in a respective knife edge spaced in close proximity to a respective one of said screen members and being generally coaxial and mirror images of each other.