FR2840241A1 - Vessel for ultrasonic cleaning, comprises tank with double floors forming additional compartment at base which houses the ultrasonic units and is continuously swept by a non- inflammable gas - Google Patents

Abstract

The cleaning tank (1) has side walls (3) and a double floor (2,5) which defines an additional watertight compartment (7). The additional compartment contains ultrasonic units (4) which are supplied from a high frequency generator (13) and is swept by a non-inflammable gas (P) using an entry (8) and exit (9). The generator is controlled by switches (15,16) which respond to exhaust gas flow (10) and compartment gas pressure (12).

Description

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  The present invention relates to a device for

  ultrasonic cleaning including a

  curite. For many years, ultrasonic techniques have been used to carry out cleaning treatments on the surfaces of divergent parts. The material used is mainly made up of a tank in which the parts to be cleaned are placed with a liquid bath, whether or not provided with a detergent and used to propa

  manage an ultrasonic ounce within it, this ultrasonic ounce

  our being generated by piezoelectric generators or transducers fixed to at least one of the walls of the tank and supplied by a high frequency current of

the order of 20 to 40 kHz.

  The transducers are generally located outside the wall, in the open air or hoods and, in

  in any event, in contact with the ambient atmosphere.

  We realized that the use of high frequency currents could at the level of the transducers cons

  have the risk of electric fire and deflagration

  if the device was used in an atmosphere

likely to explode.

  There is therefore a need for apparatuses which have solved the problem of explosive atmospheres. The invention constitutes one of these devices and thus relates to an ultrasonic cleaning device comprising a tank, at least one wall of which is externally equipped with an ultrasonic generator and a high frequency current source electrically connected to each ultrasonic generator in which the generators are housed in

a pressurized watertight enclosure.

  In reality, the device according to the invention pos-

  sede a double bottom tank and it is between the two bottoms that the dangerous transducers are disposed, these two bottoms being tightly connected to each other to form the enclosure into which a gaseous overpressure has been introduced. at the time of construction or, preferably, this is maintained continuously

gas overpressure.

  Thus, the enclosure is connected to a source of pressurized gas which communicates with the atmosphere by an exhaust pipe comprising a leak rate regulator. In addition to the pressurization of this enclosure, that is to say the organization of an internal pressure greater than atmospheric pressure am

  biante, the enclosure is swept by the gaseous atmosphere.

  This gaseous atmosphere will of course be explosion-proof and may be formed by air or, if circumstances require, nitrogen. The sweep offers in relation to a static pressurization the advantage of avoiding that over the long term the atmosphere inside the enclosure becomes polluted and could in one way or another harm the proper functioning of the transducers, or even become

itself explosion-proof.

  Another advantage of scanning resides in the fact that the enclosure communicates with the exterior and therefore provides information which can be used in particular for controlling the high frequency current source. Thus, the device advantageously comprises an adjustable threshold detector for pressure in the enclosure and an adjustable threshold detector for the flow rate in the exhaust duct, each constituting a member for controlling the opening / closing of the circuit. power supply of the high frequency current source. This ensures the certainty that the transducers do not supply power until the pressurization conditions and

  of the enclosure for satisfactory wind.

  In addition, the supply circuit of the high frequency current source includes a time delay so that the supply of high frequency current to the

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  transducers be safely ensured, the time delay constitute a filter to eliminate the phase tran

  site of the pressurization establishment of the enclosure.

  Finally, it should be noted that the presence of a pressurized enclosure immediately adjacent to one of the walls of the tank and preferably to all the walls of the tank, in a particular embodiment of the invention, constitutes a leak detector for the walls of the tank. Indeed, these walls can present defects of poro site or micro-cracks which, widening with

  use, can lead to micro-leaks.

  The pressurized atmosphere prevailing around the walls of the enclosure will generate a passage of the gas in the direction of the bath contained in the tank which will cause bubbles in this bath, thus forming a means of detecting the pre

micro-leakage.

  Other features and benefits of

  the invention will emerge from the description given below

  after one of its embodiments for information.

  Reference will be made to the accompanying drawing comprising a single figure representing schematically a

device according to the invention.

  The device shown in the figure comprises a tank 1 shown in section with a bottom wall 2 and side walls 3 made for example of stainless steel sheet. The bottom wall 2 has ultrasonic transducers 4 fixed on its outer face. This bottom wall is doubled by a second bottom king pa 5 which delimits with the wall 2 and the complementary lateral walls 6 a sealed enclosure 7 in which the wind encloses the transducers 4. This in enclosure 7 is connected by a conduit 8 to a source of pressurized gas (air or nitrogen) and to the atmosphere, by an exhaust duct 9 which comprises an element 10 for adjusting a leak rate threshold

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  can change state when the effective flow reaches

  or crosses this threshold. Room 7 has a pi-

  cage 11 at the end of which is a pressure detector 12 produced in the form of a pressure switch makes it possible to establish an adjustable pressure threshold which

  changes state when this threshold is reached or crossed.

  The device includes a source or a genera-

  high frequency current tester 13 whose supply circuit 14 has two switches 15, 16 in eerie. The switch 15 is controlled by the element 10 and is closed when this element changes state when

  the flow in the exhaust duct 9 reached or fran-

  chit the threshold sets. Likewise the switch 16 is com-

  controlled by pressure switch 12 and is closed when this pressure switch changes state when the prevailing pressure

  in enclosure 7 reaches or crosses the set threshold.

  For completeness, it will be indicated that the source of gas under pressure P is also adjustable. By acting on the pressure source and on the members 10 and 12, it is therefore possible to establish a pressurization regime of the enclosure 7 with a scanning flow rate. When this speed is reached, the switches 15 and 16 are closed and the high frequency current generator is supplied, therefore can deliver energy to the transducers 4

  necessary for the production of ultrasonic waves. We notice-

  ra that the supply circuit 14 also includes a time delay 17 which will not trigger the operation of the generator 13 after having noted the presence of a voltage at the output of the switch 16 during the set time delay. This ensures filtering

  of the entire transitional period for establishing a

  permanent scan and pressure in the enclosure In a simpler variant, the switch 15 controlled by the detects can be omitted

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  flow threshold level 10, thus favoring the overpressure criterion over the scanning criterion. It is

  also possible in an embodiment not shown

  feels that only one switch is to be operated on the supply circuit 14 which would be controlled by the

  output of a logic cell <<ET>> whose inputs are

  for one, connected to the output of a comparator receiving at input the effective flow rate which is established in the exhaust duct 9 and a set value of this flow rate, and, for the other, at the output of a comparator receiving as input the pressure prevailing in

  chamber 7 and a setpoint for this pressure.

  Finally, it will be noted that the figure shows in dotted lines the side walls 18 coming to double the side pa rods 3 of the tank to connect to their top and, the complementary side walls 6 being

  deleted, extending enclosure 7 on the periphery to-

  size of the tank 1. The enclosure 7, then being completely adjacent to the walls 2 and 3 of the tank which blows in contact with the liquid, constitutes an easy means of detecting micro cracks or porosities of the walls 2 and 3 of the tank through which, if they exist, the pressurized gas from enclosure 7 would constitute

  micro bubbles in the bath contained in the tank 1.

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Claims (6)

  1. Compressed ultrasonic cleaning device   nant a tank (1) of which a wall (2) at least is internally equipped with generators (4) ultrasound and a   high frequency current source (13) connected electrically-   ment to each ultrasonic generator (4), characterized in that the ultrasonic generators (4) are housed in   a sealed and pressurized enclosure (7).   2. Device according to claim 1, character rise in that the enclosure (7) is connected to a source (P) of pressurized gas and communicates with the atmosphere by an exhaust duct (9) comprising a regulator (10) leakage rate.   3. Device according to claim 2, character rise in that it comprises a detector (12) of adjustable pressure threshold in the enclosure (7) constitute an organ for opening / closing the circuit (14) supplying the high frequency current source (13). 4. Device according to claim 3, character rise in that it comprises a detector (10) adjustable threshold leakage rate in the exhaust pipe (9). 5. Device according to claim 3 or re vendication 4, characterized in that the supply circuit (14) of the source (13) of high current   frequency includes a time delay (17).   6. Device according to any one of the preceding claims, characterized in that the tank (1) is entirely in double walls (2, 3, 5, 18) with a sealed intermediate volume which forms the enclosure (7) sus