Measuring and testing – Instrument proving or calibrating – Fluid pressure
Reexamination Certificate
2003-01-09
2004-12-07
Garber, Charles D. (Department: 2856)
Measuring and testing
Instrument proving or calibrating
Fluid pressure
C073S001360
Reexamination Certificate
active
06826947
ABSTRACT:
FIELD OF THE INVENTION
The present invention in general relates to improvements made to solenoid valves. It is more particularly applicable to solenoid valves comprising an electromagnet subassembly associated with a pneumatic switching subassembly with a valve plug, the pneumatic switching subassembly being composed of a body enclosing the valve plug trapped between two sealing seatings facing each other. The valve plug movement is provoked firstly by a spring located in the mobile core of the electromagnet subassembly by means of a pusher, and secondly by means of a spring located under the valve plug (usually called valve plug underspring) and bearing around the lower seating of the pneumatic switching subassembly, this valve plug underspring forcing the said valve plug into contact with the upper seating of the pneumatic switching subassembly when the solenoid valve is energized. In the rest position, in other words when the solenoid valve is not energised, the spring of the mobile core of the electromagnet subassembly pushes the core into contact on the pusher and forces the valve plug onto the seating of the lower channel of the solenoid valve.
BACKGROUND OF THE INVENTION
The improvements according to the invention will be better understood with reference to
FIGS. 1 and 2
, which show axial and vertical sections through an electromagnet according to prior art.
These
FIGS. 1 and 2
show that this invention relates to a solenoid valve comprising firstly an electromagnet subassembly denoted as a whole as reference
10
, and secondly a pneumatic switching subassembly denoted as a whole as reference
12
. Mechanical means are used to assemble these two subassemblies
10
and
12
.
The pneumatic switching subassembly
12
is composed of a body enclosing a valve plug
14
, preferably made from an elastomer, that is trapped between two sealing seatings
15
and
16
facing each other. The movement of the valve plug
14
in the body of the pneumatic switching subassembly
12
is caused firstly by a spring
17
positioned in the mobile core
18
of the electromagnet subassembly
10
by means of a pusher
19
, and secondly by a spring
20
(valve plug underspring) to return the valve plug.
In the rest position, in other words when the electromagnet is not energised, the spring
17
pushes the mobile core
18
such that it forces the valve plug
14
through its pusher
19
onto the seating
16
of the lower channel of the solenoid valve.
The force applied by the spring
17
of the mobile core
18
must be sufficient to guarantee leak tightness of the lower seating
16
, and to achieve this result, this force must be equal to the following sum:
(pressure×cross section of seating
16
)+force of spring
20
+additional sealing force.
In this respect, refer to
FIG. 3
which shows the force of the spring
17
as a function of the air gap of the lower seating
16
of the valve plug.
When the solenoid valve is ni the open position, in other words when the electromagnet is energised, the magnetic force that it generates in the mobile core
18
is greater than the force of the spring
17
under these conditions, the mobile core
18
forces it into contact with the fixed core
21
a
(or the yoke) of the electromagnet subassembly
10
and it no longer applies any force on the valve plug
34
through the pusher
19
. The return spring
20
of the valve plug
14
then forces the valve plug into contact with the upper seating
15
of the subassembly
12
.
Considering its manufacturing mode (particularly the steel quality, wire diameter, number and pitch of the turns, free length), the spring
17
of the mobile core can only be made with a certain tolerance on the free length, and therefore on the force at a certain predetermined height called the “placed height”. In solutions used at the moment, the force can vary from 20 to 40% for a load at a placed height, which is becoming less acceptable in the current attempt to improve the performances and miniaturization of this type of solenoid valve.
The most frequently used solution to solve this problem at the moment is to sort the springs in order to reduce the manufacturing tolerance. This technique is a simple means of reducing manufacturing dispersions, but it still leaves relatively large variations and it increases the cost of the spring production due to manufacturing scrap.
Another solution used at the moment is to adjust the mobile core spring after the solenoid valve has been assembled. Consequently, the yoke, in other words the fixed core of the electromagnet subassembly, is perforated and drilled in the axial direction so that a threaded pusher can be fitted into it on which an O-ring is fitted to make it leak tight. This threaded pusher is in contact at one of its ends with the spring of the mobile core of the electromagnet subassembly. In order to adjust the solenoid valve, in other words the spring force on the mobile core, all that is necessary is to apply the maximum usage pressure in the lower channel of the solenoid valve and then screw the pusher in until the spring of the mobile core seals the lower seating under the pressure. This known solution is precise because the mobile core spring only applies the force necessary to create a seal on the lower seating of the valve plug of the solenoid valve. The disadvantage of this solution is its manufacturing and installation costs: it requires tapping to be formed in the fixed yoke of the solenoid valve, machining of an additional part (threaded pusher) and the installation of an additional O-ring to seal the assembly.
BRIEF DESCRIPTION OF THE INVENTION
Starting from this state of the art, the present invention has the objective of solving the technical problem mentioned above, in other words:
to reduce dispersions in the force in the spring in the mobile core of the electromagnet assembly, and
also to compensate for dispersions in the valve plug return spring (valve plug underspring) of the pneumatic switching subassembly, in a simple manner without it being necessary to use additional sealing means.
Consequently, this invention relates to a process for calibration of the mobile core spring of a solenoid valve comprising an electromagnet subassembly associated with a pneumatic switching subassembly with a valve plug, the valve plug being moved in the body of the pneumatic switching subassembly firstly by a spring located in the mobile core of the electromagnet subassembly through a pusher, and secondly by a spring located under the valve plug and bearing on the lower seating of the pneumatic switching subassembly, this process being characterised in that:
a force sensor is put into position, either at a predetermined distance from the upper face of the core, this distance being equivalent to the actual travel distance of the mobile core, or directly in contact with the face of the core when it is required to adjust the spring based on its force after the travel distance (core in contact on the yoke);
the spring is installed in a reaming provided for this purpose in the axis of the mobile core, and then,
an elastic pin is put into position behind the said spring, that is forced more or less into the reaming of the core while measuring the force generated by the spring on the sensor, and
the pin is no longer forced into the core as soon as the required force is measured by the sensor.
According to one embodiment of the process according to the invention, the parameters used for adjustment of the spring are firstly:
the placed spring height, in other words the height at which the spring must supply the force necessary to seal the lower seating, and
secondly, the force necessary to seal the lower seating, these two parameters being either calculated or measured.
According to another embodiment of the invention, the said pin is perforated on each side. It may preferably be made by spiral winding of a metallic wire, or it may be in the form of a cylindrical part or a ball.
The process according to the invention may be applied to a normally open type solenoid valve. Accordi
Courpron Bernard
Solet Daniel
Vandamme Richard
ASCO Joucomatic
Connolly Bove & Lodge & Hutz LLP
Garber Charles D.
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