Pumps – Motor driven – Fluid motor
Reexamination Certificate
1999-06-16
2001-07-31
Thorpe, Timothy S. (Department: 3746)
Pumps
Motor driven
Fluid motor
Reexamination Certificate
active
06267568
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a diaphragm pump.
PRIOR ART
A prior art document, U.S. Pat. No. 4,862,192, describes an ink jet point printer, with an ink circuit comprising a transfer device for transferring thick ink from a first supply tank and, independently thereof, the additive from a second supply tank, into an ink chamber. Ink from said ink chamber is supplied under pressure to a writing head. Ink is returned to the ink chamber through a recovery channel, traversing the writing head and recovering the ink droplets which have not been deflected for writing requirements. The transfer device uses pressurized air for transporting the ink between an ink tank, connected to the writing head, a mixing tank, connected to the supply tanks, and a recovery tank, connected to the recovery channel. The mixing tank can be alternatively connected to a suction line or to a delivery line.
In this prior art printer, the ink transfer is consequently ensured by an intermediate tank which is either under vacuum for recovering the ink in the recovery tank, or under pressure during the supply phase of the tank (accumulator) connected to the print head.
FIG. 1
shows the diagram of such a printer. The presence of an intermediate volume therein is a source of problems. Thus, the dimensions of said volume are by no means negligible. The volume and air/ink exchange surface lead to:
a high air consumption due to successive inflations and deflations of said intermediate volume,
a dissolving of the air in the ink, because the mixing volume is not equipped with an air/ink separator,
an overdimensioning and an increase in the number of pneumatic components (three pressure regulators, two and three-way valves, etc.).
These different problems lead to the use on said machines of a system differing from that described hereinbefore. Thus, on the marketed machines, it can be seen that the:
the ink transfer takes place with a diaphragm pump located between the mixing tank and the accumulator,
the mixing tank is permanently under vacuum and in fact becomes the recovery tank, which disappears from the primary circuit.
FIG. 2
shows a diagram of the system equipping the machines. This system, which is simpler and better adapted to an ink jet printer, uses a diaphragm pump. For this novel circuit, liquid admission is ensured by a spring integrated into a pump, which is directly immersed in the ink. The spring requires guiding and centring operations, which significantly increase its size. The displacement of such a pump is significant and requires the presence of a precise, mechanical air pressure regulator on the accumulator or storage tank. As the internal volume of the pump is significant, such a system suffers from numerous disadvantages during a rapid ink colour change (there is a large surface to be cleaned). This prior art printer does not bidirectionally use the pump, although there are suction valves and sometimes outlet valves with the pumps. The principle of this prior art printer is simple, but limited with respect to future applications (control of transferred volumes, ease of machine rinsing, colour change, ink addition and additive addition by the pump). It should be noted that on said machine, the pump only has a very limited number of functionalities.
The invention relates to a diaphragm pump making it possible to obviate these disadvantages.
DESCRIPTION OF THE INVENTION
The present invention describes a diaphragm pump incorporating an entirely pneumatic control mechanism, which has a double acting jack, to which is connected a diaphragm, delivery being obtained by the pressurizing of several chambers and admission being obtained by the pressurizing of a first chamber, the other chambers being under atmospheric pressure.
Advantageously, the control of said diaphragm pump is brought about by means of a single two-way/two-position solenoid valve completed by the presence of a gauged orifice permitting the depressurization of the chambers. Advantageously, said diaphragm pump comprises a body from which are hollowed out two cavities and communication channels, a two-part control piston, the diaphragm being integral with the first of the two parts of the piston. It also comprises two joints or seals located between the body and the piston, one being integral with the body (rod seal) and the other integral with the second part of the piston (piston seal). The positioning of the piston equipped with the diaphragm within these two cavities makes it possible to obtain a large chamber in two isobaric parts, a small chamber, as well as an access chamber to which access is respectively given by different orifices and in particular two suction/delivery orifices.
The pump according to the invention no longer requires the use of a spring for pump return purposes, as was the case in the prior art document. The spring is in fact a mechanical component to be calibrated, which is subject to variations in its characteristics. The spring must not be too strong to in all cases permit the delivery control and sufficiently strong to permit in all cases the suction control. This difficulty of adapting said component to the operating conditions does not exist with the pump according to the invention. Thus, the pump according to the invention adapts to all operating pressure evolutions. Thus, such a pump has a high vacuum capacity independent of its pressure characteristics. Thus, the stress or load used for creating the vacuum is directly associated with the product of the pressure prevailing in the small chamber of the jack multiplied by the surface of said small chamber. The maximum vacuum possible is obtained by dividing the load by the surface of the diaphragm. The pressure in the small chamber is permanently the source pressure, so that we obtain:
maximum vacuum=source pressure*(small chamber section/diaphragm section).
The load used for creating the pressure is directly associated with the product of the pressure prevailing in the large chamber of the jack multiplied by the surface of the diaphragm. The maximum possible delivery pressure with such a pump is consequently the source pressure.
If S is the surface of the large chamber, s the surface of the small chamber and S diaphragm the surface of the diaphragm. The arrangement is diagrammatically shown in FIG.
3
. During delivery, the driving pressure is applied to (S diaphragm−s rod+S) and substantially the same pressure is applied to s. It is pointed out that: S rod=S−s and consequently:
delivery load=pressure*((S diaphragm−(S−s)+S)−s), i.e.:
delivery load=pressure*S diaphragm.
The delivery driving load is independent of the section of the small chamber of the jack.
Advantageously, the diaphragm pump according to the invention is equipped with a pressure and temperature sensor, which is in direct contact with the fluid inside the pump.
The invention also relates to a hydraulic circuit equipped with said pump.
Advantageously, the latter comprises:
means for monitoring the source pressure located at the regulator outlet,
means for determining the clogging of a filter located in its delivery,
means for checking the sealing of the ink circuit components,
means for implementing the flowmeter functionality of the different fluid quantities consumed.
The invention also relates to an ink jet printer equipped with said ink circuit.
The pump according to the invention has numerous advantages:
simplicity,
small number of parts,
very small dead spaces,
operating reliability.
REFERENCES:
patent: 3387566 (1968-06-01), Temple
patent: 3781141 (1973-12-01), Schall
patent: 4003679 (1977-01-01), McManigill
patent: 4068983 (1978-01-01), Balme et al.
patent: 4372208 (1983-02-01), Legardinier
patent: 4648810 (1987-03-01), Schippers et al.
patent: 5782617 (1998-07-01), Habla
patent: 758 053 A1 (1997-02-01), None
patent: 2 466 640 (1981-04-01), None
Granger Catalog Jan. 1991.
Garcin Jean Denis
Pagnon Alain
Imaje S.A.
Pearne & Gordon LLP
Rodriguez W.
Thorpe Timothy S.
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