Pressure sensing apparatus having pressure pulse dampener

#The present invention relates to the field of pressure sensing and, more particularly, to a pressure gauge for high pressure water systems such as in fire fighting equipment.

#Mechanical pressure measuring instruments such as pressure gauges have employed a sensing element a curved or twisted metallic tube which is flattened in cross section. The tube is closed at one end, and has a second end open to the fluid pressure to be sensed. As fluid pressure increases, the tube tends to become more circular in cross section and tends to straighten. The nineteenth-century French inventor, Eugene Bourdon, recognized that the motion of the closed end of such a tube in response to an applied pressure is proportional to the applied pressure and, thus, provides a measure of the pressure. The Bourdon tube still bears the inventor's name in recognition of his inventive contribution.

#In many prior art pressure gauges, the fluid whose pressure is to be sensed is allowed to enter the Bourdon tube to thereby apply pressure and cause movement of the tip of the tube. With gauges of this type, water often remains trapped in the closed end of the Bourdon tube when the high pressure water system is shut down and drained. Gauges with water trapped in this manner have a tendency to freeze and be damaged by low ambient temperatures, a common problem when fighting fires in cold winter climates.

#Some of the features, advantages, and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings in which:

#FIG. 1 is a perspective external view of a pressure gauge according to an embodiment of the present invention;

#FIG. 2 is a cross sectional view of the pressure gauge of FIG. 1 cut along line 2—2 so as to show internal detail;

#The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein. Rather, these illustrated embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

#FIGS. 1-3 illustrate the pressure sensing apparatus 10 of the present invention. The apparatus 10 comprises a Bourdon tube 14, a socket 18, a diaphragm 22 also known in the art as a bladder, and a dampener 26. The Bourdon tube 14 is connected to a source of fluid pressure (not shown) for sensing pressure changes therein, The Bourdon tube 14 preferably contains a pressure sensitive medium 16 therein, and most preferably is filled with instrument oil resistant to low temperatures. A socket 18 having a bore 30 therethrough is positioned to fluidly connect the Bourdon tube 14 with the source of pressure. The skilled will recognize that the socket 18 preferably includes a threaded connector 34 for fluidly connecting the pressure sensing apparatus 10 into the fluid system requiring pressure monitoring. Additionally, the socket 18 is connected to a housing 38 within which the Bourdon tube 14 mechanism, indicator needle 42, and pressure scale 46 are positioned, as best shown in FIG. 1. The diaphragm 22 is positioned in the bore 30 of the socket 18, as shown in FIGS. 2 and 3. The diaphragm 22 being positioned between the Bourdon tube 14 and the source of pressure so as to isolate the pressure sensitive medium from the fluid whose pressure is being sensed. A dampener 26 is positioned between the diaphragm 22 and the Bourdon tube 14, the dampener having a porous body 28 effective for substantially dampening transmission of a pressure pulse from the source of pressure to the pressure sensitive medium. The dampener 26 is best shown positioned in the pressure sensing apparatus 10 in FIGS. 2 and 3.

#The dampener 26 is adapted for positioning between the Bourdon tube 14 and the source of pressure being sensed so as to protect the pressure sensing apparatus from a pressure pulse. The invention is preferably for use in a high-pressure fluid system such as in a fire engine pumper truck, which must provide high pressure water for fire fighting. The term “pressure fluctuation” is, thus, intended to include pressure changes within the system which can cause undesirable indicator needle oscillations in the pressure sensing apparatus, or even damage the apparatus. Such pressure fluctuations may be relatively minor pulsations, or may be sudden and large pressure spikes such as the above described water hammer effect. The dampener 26 comprises a preferably metallic body 28 having a plurality of pores 30 extending through the body along random paths, the plurality of pores allowing passage of fluid pressure therethrough while substantially dampening a fluid pressure pulse from the source of fluid pressure. The metallic body of the dampener 26 preferably comprises sintered metallic powder, and may comprise a plurality of metals. Further, the dampener 26 metallic body most preferably comprises a disc having a thickness 32 predetermined for a desired dampening, as shown in FIG. 3. It should be understood that dampener 26 is fabricated so as to be substantially pressure resistant.