Air pressure gauge with self contained adjustable alarms

A diver's air tank pressure gauge having audible and visual alarms, an alarm pointer for indicating the pressure at which the alarms will activate, and a crank assembly for changing the position of the alarm pointer. The pressure gauge dial has a cutout for limiting the travel of the alarm pointer between acceptable high and low pressure limits. When the air tank pressure equals a preset alarm pressure, an electrical circuit is completed which activates the alarms. The diver can then turn off the alarms by resetting the alarm indicator to a lower pressure setting and continue the dive at a shallower depth.

BACKGROUND 
1. Field Of The Invention 
This patent relates to pressure gauges, and, more particularly, to an air 
tank pressure gauge with audible and visual alarms for scuba divers. 
2. Description Of The Related Art 
Pressure gauges with alarms are known in the prior art (see, for example, 
U.S. Pat. No. 4,906,977). However, there remains a need for an air tank 
pressure gauge with audible and visual alarms for scuba divers. Such a 
pressure gauge should be capable of measuring pressures from at least 1000 
lbs. (P.S.I.G.) down to at least 250 lbs. The gauge should be provided 
with both audible and visual alarms which are activated when a diver's air 
tank pressure reaches a preset level. The gauge should also be provided 
with an adjustable alarm pressure indicator such that a diver can turn off 
the alarms by lowering the alarm pressure and continue the dive at a 
shallower depth, and repeat this process until the air tank pressure 
reaches a minimum acceptable level. 
SUMMARY OF THE INVENTION 
The present invention is an air tank pressure gauge for use by scuba divers 
comprising a dial, an indicator lever, electrically-conductive contacts 
mounted on the indicator lever, and a shorting lever. The dial has a 
cutout portion for limiting the travel of an alarm pointer between two 
predetermined limits and an air tank pressure indicator needle attached to 
a rotatable center hub. The indicator lever is pivotally attached at one 
end to a shoulder screw or pivot point and has at the other end an alarm 
pointer. The electrically-conductive contacts are connected in series to a 
battery and audible and visual alarms. The shorting lever is pivotally 
attached at one end to the center hub and has an electrically-conductive 
shorting bar mounted at the end opposite the center hub. When the air tank 
pressure reaches a predetermined alarm level, the shorting lever aligns 
with the indicator lever, causing the shorting bar to contact the 
electrically-conductive contacts, completing an electrical circuit and 
thereby activating the audible and visual alarms. 
It is an object of the present invention to provide an air tank pressure 
gauge with audible and visual alarms for use by scuba divers. 
A further object is to provide an air tank pressure gauge with audible and 
visual alarms which can be preset prior to a dive to accommodate 
anticipated dive conditions. 
A still further object of the present invention is to provide a pressure 
gauge with an adjustable alarm pressure indicator such that a diver can 
turn off the alarms by lowering the alarm pressure and continue the dive 
at a shallower depth, repeating this process until the air tank pressure 
reaches a minimum acceptable level.

DETAILED DESCRIPTION OF THE INVENTION 
Turning to the drawings, there is shown in FIG. 1 an air tank pressure 
gauge 10 according to the present invention. The pressure gauge 10 
comprises a dial 12 graduated from 0 to 4,000 lbs., a watertight case 14, 
a dial face cover 16, and a crank assembly 18. The dial 12 has a notch or 
cutout 20 cut along the edge of the dial 12 which limits the travel of an 
alarm pointer 22, preferably between a pressure of about 250 lbs. and 
about 1000 lbs. An air tank pressure indicator needle 24 is attached to a 
rotatable center hub 26 and indicates the air tank pressure. 
Preferably, the dial 12 is equipped with a light emitting diode (LED) 28 
which lights up when the pressure in the air tank reaches a predetermined 
level. The LED 28 is held in place by an LED holder 30 which is attached 
to the face of the dial 12 at about the 4,000 lb. position. 
As shown in FIG. 2, the center hub 26 is attached to a coiled Bourdon tube 
assembly 32. A shorting lever 34 is also attached to the center hub 26 
between the air tank pressure indicator needle 24 and the Bourdon tube 
assembly 32. An electrically-conductive shorting bar 36 is mounted on the 
underside of the shorting lever 34 at the end opposite the center hub 26. 
An insulator 38 is interposed between the shorting bar 36 and the shorting 
lever 34. 
An indicator lever 40 is pivotally attached at one end to a shoulder screw 
42. The shoulder screw 42 is screwed into the base 30 of the LED holder, 
providing a pivot point for the indicator lever 40. The indicator lever 40 
has a horizontal portion 44 which traverses the bottom of the dial 12 from 
the LED holder 30 to the opposite side of the dial 12, a first 
ninety-degree bend 46, a vertical portion 48 extending to just above the 
surface of the dial 12 where the indicator lever 40 terminates in a second 
ninety-degree bend 50 and the alarm pointer 22. The alarm pointer 22 is 
preferably red or another bright color, and indicates the preset air tank 
pressure at which the alarms will be activated. 
Electrically-conductive contacts 52, 52' are mounted on the horizontal 
portion 44 of the indicator lever 40 near the first ninety-degree bend 46. 
These contacts 52, 52' are connected in series to the LED 28, a battery 
54, and an audible alarm 56. One contact 52 is wired to the positive side 
of the LED 28. The second contact 52' is wired to the audible alarm 56. 
The other audible alarm wire 58 is attached to the positive end of the 
battery 54. The negative lead of the LED 28 is wired to the negative side 
of the battery 54. 
The alarms 28, 56 are activated in the following manner. When the air tank 
pressure reaches the level of the preset alarm indicator pressure, the 
indicator lever 40 and the shorting lever 34 align. The shorting bar 36 
completes the circuit across the electrically-conductive contacts 52, 52' 
(see FIG. 4), activating the alarms 28, 56. 
The dial face cover 16 and watertight case 14 encompass the dial 12, coiled 
Bourdon tube assembly 32, indicator lever 40, electrically-conductive 
contacts 52, 52', and shorting lever 34. A battery cover 60 with a 
watertight seal 62 covers the battery 54. Watertight seals 62 are also 
located between the dial face cover 16 and watertight case 14, and between 
the crank assembly 18 and the watertight case 14. 
The air tank pressure gauge 10 is used in the following manner. Prior to a 
dive, the scuba diver can set the alarm pointer 22 at a predetermined 
alarm setting of from about 1,000 lbs. down to about 250 lbs. As a dive 
progresses, the air tank pressure, indicated by the air tank pressure 
indicator needle 24, decreases. When the air tank pressure becomes equal 
to the preset indicator pressure, the audible alarm 56 will sound and the 
LED 28 will light, alerting the diver to the drop in air tank pressure. 
At that time, the diver can turn off the alarms 28, 56 by lowering the 
alarm pointer 22. The diver may also wish to begin his or her ascent at 
this time, depending upon how much air he or she has left in the air tank. 
The diver can repeat this procedure of turning off the alarms 28, 56 by 
lowering the alarm pointer 22 and ascending until the tank pressure 
reaches a minimal "safe" level of 250 lbs. Since the alarm pointer 22 
cannot be set any lower than 250 lbs., the diver can only turn off the 
alarms 28, 56 by raising the alarm pointer 22 to a point that is higher 
than the air tank pressure. At this time, the diver should return to the 
surface because the air tank pressure is at the minimum acceptable level 
of 250 lbs. 
The crank assembly 18 is used to change the position of the indicator lever 
40 and alarm pointer 22. As best shown in FIG. 3, the crank assembly 18 
comprises a knob 64, a mounting screw 66 perpendicularly mounted to the 
center of the knob 64, and a vertical lever 68 fixedly attached to the end 
of the mounting screw 66 opposite the knob 64. 
The indicator lever 40 further comprises a pin 70 perpendicularly mounted 
on the vertical portion 48 of the indicator lever 40 and facing away from 
the shoulder screw 42. The pin 70 is slidably connected to the vertical 
lever 68. In the preferred embodiment, the vertical lever 68 has a forked 
end 72 with two prongs 74 and the pin 70 extends between the two prongs 
74. 
The position of the indicator lever 40 and the alarm pointer 22 can be 
changed by rotating the knob 64, which rotates the mounting screw 66, 
causing the vertical lever 68 to pivot about its point of attachment to 
the mounting screw 66. As the vertical lever 68 pivots, the indicator 
lever 40 pivots about the shoulder screw 42 and the alarm pointer 22 moves 
across the face of the dial 12. This movement is limited by the length of 
the cutout 20, preferably to between 250 lbs. and 1,000 lbs. 
Other modifications and alternative embodiments of the invention are 
contemplated which do not depart from the spirit and scope of the 
invention as defined by the foregoing teachings and appended claims. For 
example, an air tank pressure gauge is contemplated having a visual alarm 
only, and no audible alarm.