Rotary needle and expanding bellows pressure indicator

Abstract

A fluid pressure indicating device is disclosed. The fluid pressure indicating device includes a base defining an aperture therethrough, a plate separated from the base by a variable distance, the plate defining a hole therethrough, a shaft including a helical surface disposed within the hole of the plate, a first bellows extending between the base and the plate, and a second bellows extending between the base and the plate, the second bellows disposed around the first bellows, the first bellows and the second bellows defining a first chamber therebetween. The first bellows and the second bellows expand or contract in response to a difference between a pressure inside the first chamber and a pressure outside the first chamber. The variable distance between the base and the plate varies upon expansion or contraction of the first bellows and the second bellows, such that the shaft rotates relative to the plate.

1 . A fluid pressure indicating device, comprising:
 a base defining a base aperture therethrough;   a plate separated from the base by a variable distance, the plate defining a hole therethrough;   a shaft rotatable about a first axis, the shaft including a helical surface disposed within the hole of the plate;   a first bellows extending between the base and the plate; and   a second bellows extending between the base and the plate, the second bellows disposed around the first bellows, the first bellows and the second bellows defining a first chamber therebetween,   wherein the first bellows and the second bellows expand or contract in response to a difference between a pressure inside the first chamber and a pressure outside the first chamber, and   wherein the variable distance between the base and the plate varies upon expansion or contraction of the first bellows and the second bellows, such that the shaft rotates relative to the plate.   
     
     
         2 . The fluid pressure indicating device of  claim 1 , further comprising a flow channel in fluid communication with the first chamber through the base aperture. 
     
     
         3 . The fluid pressure indicating device of  claim 1 , further comprising a pointer disposed on the shaft. 
     
     
         4 . The fluid pressure indicating device of  claim 3 , further comprising pressure indicia disposed on a surface of the plate facing the pointer. 
     
     
         5 . The fluid pressure indicating device of  claim 3 , further comprising:
 a housing surrounding the second bellows; and   pressure indicia disposed on a surface of the housing.   
     
     
         6 . The fluid pressure indicating device of  claim 5 , wherein a portion of the housing adjacent the pressure indicia is permeable to visible light. 
     
     
         7 . The fluid pressure indicating device of  claim 5 , wherein the pointer is disposed between the plate and the housing, and the pointer is visible through the housing and the pressure indicia. 
     
     
         8 . The fluid pressure indicating device of  claim 1 , further comprising a housing surrounding the second bellows. 
     
     
         9 . The fluid pressure indicating device of  claim 8 , wherein the housing and the second bellows define a second chamber therebetween, and
 wherein the housing defines a housing aperture therethrough, such that the second chamber is in fluid communication with an ambient environment around the fluid pressure indicating device through the housing aperture.   
     
     
         10 . The fluid pressure indicating device of  claim 9 , wherein the first bellows and the second bellows expand or contract in response to a difference between the pressure inside the first chamber and a pressure inside the second chamber. 
     
     
         11 . The fluid pressure indicating device of  claim 1 , wherein the first bellows and the second bellows each includes a plurality of corrugations. 
     
     
         12 . The fluid pressure indicating device of  claim 1 , wherein the first bellows and the second bellows each has a substantially cylindrical shape. 
     
     
         13 . The fluid pressure indicating device of  claim 1 , further comprising a bearing fixed to the base and rotatably coupled to the shaft. 
     
     
         14 . The fluid pressure indicating device of  claim 8 , further comprising a bearing fixed to the housing and rotatably coupled to the shaft. 
     
     
         15 . An expandable cuff system, comprising:
 a tube defining a lumen therein;   an expandable bladder in fluid communication with the lumen; and   a fluid pressure indicator including
 a plate defining a hole therethrough, and 
 a shaft rotatable about a first axis, the shaft including a helical surface disposed within the hole, wherein a portion of the plate is in fluid communication with the expandable bladder through the lumen. 
   
     
     
         16 . The expandable cuff system of  claim 15 , wherein the fluid pressure indicator further includes
 a base defining a base aperture therethrough, the base separated from the plate by a variable distance;   a first bellows extending between the base and the plate; and   a second bellows extending between the base and the plate, the second bellows disposed around the first bellows, the first bellows and the second bellows defining a first chamber therebetween.   
     
     
         17 . The expandable cuff system of  claim 16 , wherein the first bellows and the second bellows expand or contract in response to a difference between a pressure inside the first chamber and a pressure outside the first chamber, and
 wherein the variable distance between the base and the plate varies upon expansion or contraction of the first bellows and the second bellows, such that the shaft rotates relative to the plate.   
     
     
         18 . A fluid pressure indicating device, comprising:
 a base defining a base aperture therethrough;   a plate separated from the base by a variable distance, the plate defining a hole therethrough;   a shaft rotatable about a first axis, the shaft including a helical surface disposed within the hole of the plate;   first means for defining a variable volume extending between the base and the plate; and   second means for defining the variable volume extending between the base and the plate, the second means for defining the variable volume disposed around the first means for defining the variable volume, the first means for defining the variable volume and the second means for defining the variable volume defining a first chamber therebetween,   wherein a volume of the first chamber expands or contracts in response to a difference between a pressure inside the first chamber and a pressure outside the first chamber, and   wherein the variable distance between the base and the plate varies upon expansion or contraction of the volume of the first chamber, such that the shaft rotates relative to the plate.   
     
     
         19 . The fluid pressure indicating device of  claim 18 , further comprising a resilient member that biases the plate toward a position that minimizes a volume of the first chamber. 
     
     
         20 . The fluid pressure indicating device of  claim 18 , further comprising a resilient member that biases the plate toward a position that maximizes a volume of the second chamber.