Patent Application
20130340844
1. Field of the Invention
This invention relates, generally, to pilot valves. More particularly, it relates to a novel heat sink for an electropneumatic pilot valve.
2. Description of the Prior Art
The power of compressed air used in actuating cylinders and motors needs to be controlled. A directional-control valve positioned between the source of pneumatic energy and the actuator performs this function.
Pneumatic directional-control valves generally require the use of electropneumatic pilot valves to allow them to switch states. These electropneumatic pilot valves are generally of the electromagnetic type and therefore generate heat associated with the Joule effect due to electric current passing through an inductor coil.
The heating effect can be reduced by limiting the power of the coil, but such power limitation impairs pneumatic performance. The electropneumatic pilot valves may also be positioned in such a way that their heat is transferred directly to the outside. This solution places severe restrictions on the pneumatic and electrical connections and therefore impacts the dimensioning of the pneumatic directional-control valve.
This disadvantage increases where pneumatic distribution blocks which are made up of several pneumatic directional-control valves are juxtaposed with one another. This juxtaposition, by confining the heat sources, further reduces the capacity for heat transfer to the outside, i.e., away from heat-sensitive devices.
The issue of heat transfer rates and improvement of same is a concern of electrical component manufacturers.
In the field of electric transformers, the solution put forward in patent JP2010027733 proposes accelerating the dissipation of heat using a simple metal plate and a thermal contact.
Unfortunately, such solutions provide an insufficient heat removal rate and therefore cannot guarantee optimum operation of the devices.
It is therefore an important object of the invention to optimize heat transfer from a pilot valve to an external medium.
However, in view of the prior art considered as a whole at the time of the invention, it was not obvious to those of ordinary skill how the heat transfer rate could be improved.
SUMMARY OF THE INVENTION
The novel pneumatic distribution device having at least one electromagnetic pilot valve and a distribution body includes at least one heat sink having a thermal conductivity of at least 0.9 W/m K, tested in accordance with the ASTM D5470 standard, positioned between said at least one electromagnetic pilot valve and said distribution body.
The novel pneumatic distribution device also includes a pneumatic distribution line associated with a sleeve and with a mobile spool with elastomeric sealing or so-called “metal-to-metal” sliding contact. A manual control device is optional as is a printed circuit connecting the pilots to the electric control circuits. Where a printed circuit is used, the heat sink allows greater proximity between the pilot and the electronic components of the circuit without the risk of the components of the circuit becoming damaged, due to the enhanced rate of heat transfer made possible by the novel heat sink.
A simple pneumatic base is also disclosed, in the case of a directional-control valve in isolation, or a juxtaposable pneumatic base in order to create a distribution block.
The use of one or more heat sinks able to collect and direct the thermal flux emitted thereby makes it possible to limit the extent to which the electromagnetic pilots heat up. It is also conceivable to combine these heat sinks in the assembly of the distribution body and of the pneumatic base, to further increase the capacity for heat transfer between these two parts.
Advantageously, the heat sink has a thermal conductivity of at least 0.9 W/m K, tested in accordance with the ASTM D5470 standard.
More advantageously, the heat sink has a thermal conductivity of at least 1.2 W/m K, tested in accordance with the ASTM D5470 standard.
The device may be assembled onto a metallic pneumatic base, at least one heat sink being interposed between the distribution body and the pneumatic base.
The heat sink may have a Shore 00 hardness between 30 and 80, tested in accordance with the ASTM D 2240 standard.
Advantageously, the heat sink has a Shore 00 hardness between 40 and 70, tested in accordance with the ASTM D 2240 standard.
More advantageously, the heat sink has a Shore 00 hardness between 40 and 50, tested in accordance with the ASTM D 2240 standard.
The heat sink may be obtained by polymerizing or solidifying a liquid or pasty material.
Other features and advantages of the invention will become apparent from the following description of a preferred embodiment (bistable directional-control valve with two electromagnetic pilots and juxtaposable pneumatic base) with reference to the attached drawings, but which does not imply any limitations.
Heat sink 2, depicted in
Heat sink 2 may be placed under stress to ensure permanent contact between the facing surfaces. Heat sink 2 may be made of an elastic or rigid material or may be made by polymerizing or solidifying a liquid or a pasty material.
Examples of heat sinks 2 include the 1000SF pads by Bergquist which have a thermal conductivity of 0.9 W/m K for a thickness of 0.254 to 3.175 mm, tested in accordance with the ASTM D5470 standard and a Shore 00 hardness of 40, tested in accordance with ASTM D 2240 standard, or the 575 NS pads by Parker which have a thermal conductivity of 1.2 W/m K for a thickness of 0.5 to 2.5 mm, tested in accordance with the ASTM D5470 standard and a Shore 00 hardness of 70, tested in accordance with the ASTM D 2240 standard.
There are numerous possible alternative ways of embodying the preferred embodiment disclosed hereinabove.
In an alternative embodiment, electropneumatic pilot 1 may be completely incorporated into the pneumatic directional-control valve 4 in housing 8 as depicted in
As depicted in
Pneumatic directional-control valve 4 may also be assembled onto a metal base 6 as depicted in
Several heat sinks may also advantageously be added to pneumatic directional-control valve 4 or to metal base 6, or both, or in between these two elements, to increase the conduction of the thermal flux and the dissipation of heat of the assembly of the pneumatic directional-control valve or valves 4 mounted on metallic base 6.
As indicated by
The device according to the invention makes it possible to increase the area for heat exchange with the external medium, but also the use of the pneumatic base and its circulation of compressed air flow such as, in particular, the supply and return common lines in the distribution blocks.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1256001 | Jun 2012 | FR | national |
