Electromagnetic safety mechanism

The fail-safe gas valve solenoid construction disclosed herein employs a fixed electromagnet which, when energized, actuates an operating rod by means of an armature which is relatively loosely secured to the shaft to permit self-alignment between the magnet and the armature. Relative movement and wear between the armature and the shaft is inhibited by an elastomeric washer or O-ring which is interposed between the armature and a corresponding or facing surface associated with the shaft, the washer being under slight compression.

BACKGROUND OF THE INVENTION 
The present invention relates to a fail-safe fuel valve employed as a 
safety device for thermoelectric ignition and more particularly to the 
mounting of the armature in such a mechanism. 
The well known thermoelectric ignition safety devices that serve to shut 
off the flow of gas to burner equipment in case of extinction of a burner 
flame or of a pilot, require, as is known, an electromagnet or 2-pole 
magnetic core, as well as an armature plate mounted at one end of a shaft 
whose other end carries either a valve or a socket, depending on whether 
the mechanism is designed to block a flow of gas directly or by the 
intermediation of levers which may be engaged by the socket. To protect 
the magnetic core and the armature operating with it, they are surrounded 
by a non-magnetic metallic protective cover, e.g. of brass, or made of 
plastic. 
In these known devices, the magnetic core is fixed rigidly on a bed-plate. 
On the other hand, the armature is set on the shaft in such a way that 
there can exist a certain free motion permitting it to be hinged with 
respect to the two poles of the magnetic core at the time of the 
operational motions of the gas equipment in which the electromagnetic 
safety device is incorporated. Finally, there is used a metallic washer 
integral with the shaft, or resting against a shoulder of the shaft, whose 
function, in being applied against the rear face of the armature, is to 
maintain the armature in a plane generally perpendicular to the shaft, and 
to serve possibly as a stop against the top of the housing when the 
armature disengages from the magnetic core. 
One disadvantage of this method of mounting of the armature for 
self-alignment is that wear can occur between the armature and the 
corresponding part of the shaft to which it is attached. The shaft 
typically includes a portion of reduced diameter which passes through an 
aperture in the armature and is then typically riveted over to retain the 
armature. For example, energizing impulses applied to the electromagnet 
may cause the armature to rotate relative to the shaft and, as the result, 
small metallic particles may detach from the armature or from the shaft or 
from both parts, which particles can become attached to the magnetized 
surfaces of the electromagnet. These particles can bring about variation 
in the locking an unlocking characteristics of the valve and may even 
effect a total alteration of the functioning of the safety device. 
SUMMARY OF THE INVENTION 
The invention proposes a new attachment arrangement for the armature on the 
shaft which alleviates these disadvantages. In accordance with the 
invention, there is interposed, between the rear of the armature and the 
circular washer associated with the shaft, an elastic seal which is found 
pre-compressed at the moment of the operation of setting the extremity of 
the shaft, and whose role is to impede the rotation of the armature 
following the control impulses of the mechanism, while allowing a certain 
mobility to orient or to hinge itself with respect to the shaft in order 
to always be in perfect contact against the poles of the magnetic core. 
Other objects and features will be in part pointed out and in part 
understood from the following description.

Corresponding reference characters indicate corresponding parts throughout 
the several views of the drawings. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The safety mechanism such as is represented by FIG. 1 generally includes a 
magnetic core 5, an armature 4 mounted at one extremity of the shaft 1, 
and, at the outer extremity of this shaft, a valve 6 for obstructing 
directly a flow of gas, this valve being able to be replaced by a cup or 
socket if the mechanism must act on a valve unit through the intervention 
of levers. The core 5 is rigidly fixed by a rivet or by a contact rivet 7 
on the bed-plate 8. A protective case 9 covers the core 5 and its armature 
4. A return spring 10 supported on the base covers the shaft 1 and acts on 
the valve 6. 
The shaft 1 is journaled for axial movement in the case 9. The inner end of 
the shaft 1 includes a portion 21 which is of reduced diameter, the 
innermost end of which is riveted over, as indicated at 11, to retain the 
armature 4 in such a way that there exists a freedom of motion between the 
armature and the shaft permitting the armature to self-align with the 
magnetic core 5. The magnetic core 5 includes or is provided with a 
winding 23 which, when energized, acts on the armature 4 to draw the shaft 
1 inwardly and open the fuel valve. 
A circular metallic washer abuts the shoulder existing between the full and 
reduced diameter portions of the shaft 1. Interposed between the armature 
4 and the circular metallic washer 3 and coaxial with the shaft is an 
O-ring 2, i.e. an elastomeric toroidal seal. The various parts are 
dimensioned and the riveting over of the reduced diameter portion of the 
shaft is carried out so that this O-ring is normally under slight 
compression. Accordingly, the O-ring 2 prevents the rotation of the 
armature and relative wear and working between the armature and the shaft 
1 but, nevertheless, permits the armature to move sufficiently to 
self-align when it is attracted to the magnetic core 5. In that the 
armature does not rotate, it no longer produces either substantial wear or 
liberation of metallic particles caused by working between the central 
opening of the armature and the mating portion of the shaft. Accordingly, 
the operation of the solenoid valve system remains stable and predictable. 
FIG. 2 illustrates another variation of embodiment of the invention, in 
which the toroidal seal 2 is located in a circular groove 12 obtained by 
machining or stamping the armature. The seal being thus held, the metallic 
washer 3 is level. In FIG. 3, the elastic toroidal seal is replaced by a 
flat seal 2, and the hinging is assured by the intervention of a metallic 
ring 13 located in a chamber 14 machined or stamped into the rear face of 
the armature 4. 
FIG. 4 is a variation of the embodiments described previously, in which the 
toroidal seal 2 has a square cross-section; it is located within the 
chamber 14 also provided in the armature. 
Finally, FIG. 5 shows another variation of the embodiments, showing the 
same advantages. The toroidal seal or the seal of square cross-section is 
replaced by an elastic seal 2 with rectangular cross-section, and the 
washer 3 has a form 15 stamped in a V, or rounded, playing the role of a 
hinge. 
In view of the foregoing, it may be seen that several objects of the 
present invention are achieved and other advantageous results have been 
attained. 
As various changes could be made in the above constructions without 
departing from the scope of the invention, it should be understood that 
all matter contained in the above description or shown in the accompanying 
drawings shall be interpreted as illustrative and not in a limiting sense.