Solenoid energization indicator

An energization indicator for a solenoid includes an electrically operable signaler (70) having a coil (72) for energizing the signaler (70) when a magnetic flux field sweeps such coil, with the coil (72) being mounted in the magnetic flux path of the solenoid coil (53).

FIELD OF INVENTION 
This invention relates to an energization indicator, such as a pilot light, 
for solenoids and in particular to such an indicator which operates on the 
voltage induced from the solenoid coil. 
BACKGROUND OF THE INVENTION 
During inspection or servicing of pneumatic or hydraulic systems employing 
solenoid-operated pilot valves, it is often desirable to be able to 
determine if a particular pilot valve solenoid is actually electrically 
energized as and when it is supposed to be. Sensing the electrical 
condition of such solenoids has heretofore been accomplished by either 
inserting a suitable detector in the solenoid circuit at the time of the 
inspection, such as by disconnecting a wire at the solenoid and 
temporarily connecting in a meter, or by having a light permanently wired 
in the solenoid circuit. The first approach was time consuming and the 
second substantially raised the initial cost of the solenoid. 
The following prior art U.S. patents show sensing devices either hard wired 
into a switch or solenoid circuit or inductively coupled with a carrying 
wire: 
U.S. Pat. No. 2,591,336 
U.S. Pat. No. 2,611,843 
U.S. Pat. No. 3,316,447 
U.S. Pat. No. 3,488,611 
U.S. Pat. No. 3,909,670 
U.S. Pat. No. 5,015,944 
SUMMARY OF THE INVENTION 
A solenoid pilot light comprising a lamp connected to an inductance coil is 
mounted on a solenoid so that the inductance coil is inductively coupled 
with the solenoid coil whereby upon energizing the solenoid the lamp is 
inductively illuminated. In a preferred embodiment, the lamp and 
inductance coil are compactly arranged and housed as a unit which may be 
used on the pilot valve solenoid in place of the solenoid retaining nut. 
In such embodiment the pilot light may be offered as an aftermarket item 
to replace retaining nuts on pilot valves in the field.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT 
As shown in FIG. 4, a typical pilot valve solenoid comprises a cylindrical 
plunger post 8 having a brass tube portion 10, the proximal end of which 
is enlarged with a boss-like flange 12 encircled by a groove 14 within 
which is disposed an O-ring 16 for sealing the boss and in turn the 
plunger post within the pilot valve, not shown. The solenoid plunger 18 is 
disposed within the bore 20 of the tube portion 10 for limited 
reciprocation and may be biased outwardly by a spring 22. The plunger is 
provided with elastomeric valve faces 24 and 26 at opposite ends, the 
former for sealing against an orifice (not shown) in the pilot valve, and 
the latter for sealing the orifice at 28 within the post. These valve 
faces may be provided by opposite ends of an elastomeric insert 30 
disposed within a hollow bore 32 in the plunger 18. 
The plunger post 8 is provided with a stop portion 34 received within the 
tubular portion 10 and secured by an indentation as at 36, which 
cooperates with a groove 38 in the stop. A fluid passageway 40 in the stop 
opens at its lower end through the orifice 28 and at its upper end through 
the distal end 42 of the post. The bore 40 may be enlarged as at 44 and 
threaded to receive a screw 46 which is axially bored as at 48 to allow 
the passage of fluid axially through the screw whereby fluid within the 
bore 40 may escape outwardly of the post. It will be noted the plunger 18 
has a clearance between its external cylindrical surface and the bore 20 
of the post so that fluid from the pilot valve may escape around the 
plunger and through the orifice 28 when the plunger is spaced downwardly 
from the orifice 28. 
The plunger stop may include a shading coil 50 disposed circumaxially 
around the orifice 28 to provide for a quiet holding of the plunger 
against the orifice when the solenoid is energized. 
Removably telescoped over the plunger post 18 and its plunger stop 34 is 
the solenoid coil assembly 52. The assembly comprises a solenoid coil 53 
and bobbin generally indicated by the reference numeral 54, a steel 
solenoid frame 56 of generally C-shaped configuration which embraces the 
coil and bobbin and overlies opposite ends thereof. The coil and bobbin 54 
and frame 56 are encapsulated within a plastic encapsulating medium 58 
which integrates these parts as a unitary assembly. A pair of electric 
contact blades 60 (only one of which is shown) are connected to opposite 
ends of the solenoid coil to be connected in an alternating current 
circuit for energizing the coil. A third contact blade 62 is connected to 
the solenoid frame as a ground. These blades are suitably encapsulated by 
the encapsulating medium 58. 
The plunger post and plunger stop may be held to the pilot valve by a clamp 
plate 64 which is telescoped down over the post and bears against the boss 
or flange 12. Suitable fasteners, not shown, may be passed through the 
plate 64 and threaded into the pilot valve to secure the post thereto with 
the O-ring 16 effecting the seal between the post and valve. The coil 
assembly 52 is telescoped over the post 8 and rests upon the plate 64 as 
shown in FIG. 4. 
The coil assembly 52 is normally held on the plunger post 8 and its 
outwardly projecting plunger stop portion 34 by a hold-down nut (not 
shown) which is internally threaded and is threadedly engaged over 
external threads 66 on the distal end of the plunger post. By removing 
such nut, the coil assembly 52 may be simply withdrawn off the post. With 
the hold-down nut tightened down against the coil assembly 52, the 
assembly is held securely on the post. The invention disclosed herein is 
intended to replace such nut and permits the mechanic to readily determine 
whether the pilot valve has been energized. 
In general the invention comprises an electrically operable signaller 70, 
shown herein in the form of an electric lamp, such as an LED. A signaller 
coil 72 electrically connected to the signaller or lamp is operable to 
activate the signaller when the magnetic flux from coil assembly 54 sweeps 
the coil 72. Housing means 74 are provided which protectively enclose or 
encapsulate the signaller coil 72 and provide a mounting or support for 
the lamp 70, as best shown in FIG. 3. The housing means includes an 
axially extending aperture 76 (see FIG. 3) which opens through an end face 
78. The aperture or bore 76 is intended to be received over the distal end 
42 of the plunger post whereby the coil 72 surrounds the post and the end 
face 78 can bear against the upwardly disposed surface 80 of the solenoid 
coil assembly 52. The signaller assembly may be held on the plunger post 
either by having the bore or aperture 76 threaded as shown in FIG. 3, or 
the screw 46 shown in FIG. 4 may have an enlarged head portion 82 which 
will overlie the housing means 74 to hold the housing means downwardly 
against the surface 80 of the coil assembly 52. In the latter case, the 
threads in the bore or aperture 76 may be eliminated and similarly the 
threads 66 on the distal end of the plunger stop may be eliminated. Either 
approach to holding the signaller assembly on the distal end of the 
plunger stop may be utilized. It is generally intended, however, that the 
signaller assembly will simply replace the pre-existing nut normally used 
to retain the solenoid assembly 52 on the distal end of the post. 
More specifically, the signaller assembly includes a bobbin 100, as shown 
in FIG. 2, having a flange 102 and a central cylindrical body 104 integral 
with the flange and terminating in resilient teeth 106 arranged in a 
circular configuration as shown in FIG. 2 and over which may be snapped a 
circuit board 108 carrying the LED 70. In practice, the circuit board 108 
may be snapped on to the bobbin before the wire coil is wound thereon. The 
coil is shown schematically in FIG. 2 as a donut 72. Ends of the coil wire 
are secured to pigtails on the lamp 70 in a well-understood fashion. 
Circuit board 108 has a central aperture 110, and the body 104 of the 
bobbin has a bore 112 and downwardly through the aperture 110 and the bore 
112 is received the cylindrical nut 116 having a flange 118 which overlies 
and bears against the upper face of the circuit board 108. For this 
purpose the flange 118 of the nut is provided with a through aperture 120 
which is telescoped over the lamp 70. The lamp projects upwardly through 
the aperture 120 as best shown in FIG. 3. 
Diametrically opposite aperture 120 is an aperture 122 for receiving the 
downwardly projecting ear 124 of the plastic cap 126, to allow torque 
driving between the cap and the nut 116. The cap 126 is either transparent 
or at least has a transparent lens portion 128 allowing light from the 
lamp 70 to shine through the cap. The cap 126 may be snapped on to the 
flange 102 of the bobbin by providing the periphery of the flange 102 with 
a small peripheral rib 130 which engages within a corresponding internal 
peripheral groove 132 in the lower edge of the cap. 
The exterior 134 of the cylindrical surface of the cap may be knurled to 
facilitate finger tightening of the signaller assembly on the threaded 
distal end of the plunger stop. The cap 126 may be either molded in a 
two-shot molding technique where the body of the cap is opaque and the 
lens portion 128 is translucent or transparent, or the cap may be formed 
with the lens portion 128 secured to the body of the cap after both 
portions have been molded. 
The nut 116 may be steel for conducting magnetic flux F up through the 
center of the signaller coil 72 as best shown in FIG. 5. As these flux 
lines cut across the signaller coil 72, they induce a voltage in such coil 
causing illumination of the LED or lamp 70, which is then visible to the 
mechanic through the transparent or translucent lens portion 128 of the 
cap 126, and indicates that the solenoid coil 54 is energized. 
While a lamp 70 is shown as the energization indicator, it will be 
understood that any other suitable signaller may be utilized including a 
circuit connected to a control panel or a portion of a telemetry 
redundancy system.