Pressure gage

A pressure gage for indicating pressure and variations thereof of a physical variable being monitored. The gage is provided with a circular dial having on the face thereof a pheripheral marginal portion or border green in color and graduations disposed internally of the green peripheral border. A pair of movable arcuate opaque cover plates, each made as an arc of an annulus, are disposed coaxial with the dial and graduations on the face of the dial. The plates are movably mounted for positioning thereof selectively in a circumferential direction of the dial for partially covering the marginal peripheral portion or border of the face of the dial. The plates are positionable selectively so that two opposed ends thereof define a space therebetween so that a green area of the border, which defines a range of selected pressure graduations on the dial, corresponds therewith. These two ends are colored red so that different ranges of pressure graduations may be selected to establish a range of normal values of pressures at which pressures the physical variable are in correspondence with a green normal zone or area of the dial. The graduations outside of the selected range remain visible and the pointer, also continuously visible, points to the instantaneous pressure value which may be in correspondence with the green area or the red areas designated by the plates.

BACKGROUND OF THE INVENTION 
(a) Field of the Invention: 
The present invention relates to a pressure gage permitting it to read a 
value on a disc-like dial as indicated by a pointer adapted to a be 
rotated around a center of the dial and thereby to determine a fluid 
pressure and, more particularly, to such a pressure gage being capable of 
accurately displaying a predetermined pressure range assuring a normal 
function of an apparatus which is subjected to a pressure of fluid such as 
air, water or oil. 
(b) Description of the Prior Art: 
To display a predetermined pressure range assuring a normal function of an 
apparatus which is subjected to a fluid pressure, the conventional 
pressure gage has usually been provided on the periphery of the dial with 
a single or two arrow-marking(s) adapted to indicate upper and lower 
critical values or any one of these critical values of the predetermined 
pressure range. With such a way of displaying, the marking has been so 
unnoticeable that it has often been difficult to determine whether the 
pressure value indicated by the pointer falls within the preset pressure 
range or not. 
SUMMARY OF INVENTION 
As a measure to solve the above-mentioned problem, the present invention 
provides a construction such that the dial is formed on its front surface 
with an indication hem extending along the outer periphery thereof and 
cover plates each in the form of circular arc are mounted on the dial in a 
circumferentialy position-adjustable manner for partially covering said 
indication hem, wherein the cover plates may be circumferentially 
displaced over the indication hem so as to cover the latter leaving a 
predetermined area exposed and thereby to display the predetermined 
pressure range by the exposed area of the indication hem extending along a 
portion of the periphery in the form of a circular arc. Thus, the preset 
range is displayed as a continuous circular arc which is easily visible 
and effectively facilitates it to determine whether the pressure value 
indicated by the pointer falls within the preset range or not.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present invention will be more apparent from reading the following 
description of an embodiment, as applied to the Bourdon-tube pressure 
gage, given in reference with the accompanying drawing. 
A pressure gage according to this embodiment essentially comprises a body 1 
provided on its rear end with a male screw 2 projecting therefrom by which 
the pressure gage is mounted on an apparatus (not shown) being subjected 
to a pressure of fluid and actuator a carried by said body 1 to rotate an 
output shaft 6. This actuator a is so constructed that a pressure of the 
fluid introduced through a guide bore 9 formed in the body 1 into a 
Bourdon-tube 3 causes a deformation of the latter, said deformation 
causes, in turn, rotation of a sector gear 5 connected through a link 4 to 
a free end of said Bourdon-tube 3 and a pinion 7 adapted to be engaged 
with said sector gear 5, and thereby causes rotation of said output shaft 
6 fixed to said pinion 7. The body 1 is provided on its front side with a 
circular dial 8 secured thereon by pins 11, 11 and said circular dial 8 
carries on its front surface suitably calibrated graduations 10 
circumferentially arranged slightly inside the outer periphery of the dial 
8 itself. The output shaft 6 extending through a central hole 12 of the 
dial 8 carries on its front end a pointer 13 adapted to be rotated over 
the front surface of the dial 8 as the pressure of fluid varies and to 
indicate a particular graduation 10 corresponding to a current value of 
said pressure. A green-colored annular indication hem 14 surrounds the 
graduations 10 carried on the front surface of the dial 8 and a pair of 
cover plates 15, 16 in the form of semi-circular arcs are provided for 
partially covering the indication hem 14, respectively. 
The cover plate 15 closely bears against the indication hem 14 and has a 
portion at its end as seen in a counterclockwise direction red-colored on 
the front surface thereof so as to define a limit indicating area 24. At 
this area 24 of the indication hem 14, an arm 18 integrally extending from 
the hem 14, striding over the periphery and along the rear surface of the 
dial 8, towards the center of the dial 8. A circular front end of the arm 
18 is centrally formed with a mounting through-hole 19. The other cover 
plate 16 has a portion at its end as seen in a clockwise direction 
red-colored on the front surface thereof also to define a limit indicating 
area 25. The cover plate 16 further includes a support plate 21 in the 
form of semi-circular arc integral with or continuous from said cover 
plate 16 but spaced from the latter so that the dial 8 and said one cover 
plate 15 may be somewhat tightly received therebetween. Said support plate 
21 strides over the periphery of the dial 8 and extends along the rear 
surface thereof. The support plate 21 is formed at its end as seen in 
clockwise direction with an arm 22 extending integrally therefrom towards 
the center of the dial 8. A circular front of this arm 22 is centrally 
formed with a mounting through-hole 23 in alignment with the mounting 
through-hole 19 formed through the arm 18 of said one cover plate 15 and 
these mounting through-holes 19, 23 are rotatably received around a 
bushing 26 tightly extending through the central hole 12 of the dial 8. 
The indication hem 14 of the dial 8 is partially covered by the cover 
plates 15, 16 with the end of the one cover plate 15 as seen in the 
clockwise direction being received between the other cover plate 16 and 
the dial 8 and, in this area, the cover plates 16, 15, the dial 8 and the 
support plate 21 closely bearing against one another in this order so that 
a frictional force developed among these components prevents the cover 
plates 15, 16 from being rotationally displaced relative to the dial 8 and 
a portion of the indication hem 14 defined between the limit indicating 
areas 24, 25 of the cover plates 15, 16, respectively, is exposed to be 
seen from the front. 
The above-mentioned mechanism is enclosed by a cylindrical casing 28 
secured to the body 1 and a transparent disc 29 is mounted in a front 
opening of said casing 28 covers the front surface of the dial 8. 
In operation of the pressure gage according to the embodiment considered 
herein, when the cover plates 15, 16 are individually displaced in the 
circumferential direction with their corresponding ends being adjusted to 
the upper and lower limit values, respectively, of a predetermined 
pressure range previously set as the safety range, the safety range is 
indicated by a green-colored circular arc extending along a portion of the 
outer periphery of the graduations 10 while, at the opposite ends of said 
arc, the opposite borders of said safety range are indicated by the 
red-colored limit indicating areas 24, 25. 
It should be understood that, if it is desired to avoid any circumferential 
displacement of the cover plates 15, 16 possibly occurring due to factors 
such as vibration, the dial 8 may be formed along its outer periphery with 
fine indentation while the cover plates 15, 16 also may be formed with 
correspondingly fine indentation adapted to be engaged with the 
indentation of the dial 8 and thereby to avoid said accidental 
displacement. 
Furthermore, it should be understood that the present invention can find 
its application not only to the Bourdon-tube pressure gage but also to the 
pressure gage of any other type in which the graduations carried on the 
circular dial are pointed by the rotatable pointer.