DE2135519A1 - DIAPHRAGM PUMP FOR TRANSFERRING LIQUIDS - Google Patents

Description

Diaphragm pump for pumping liquids

The invention relates to a diaphragm pump for pumping small amounts of liquid, in particular for Ink jet pen for conveying the writing ink by influencing the membrane element in opposite directions in interaction by an electromagnet and a spring element from a storage container to the writing head, from its small-caliber outlet opening the writing ink is only released by the influence of an electrical one Field is promoted and distracted in the direction of the writing point.

The basic structure of a piston pump for pumping liquids as well as gases is sufficient known. The principle of such pumps is that the contents of a feed channel except for one and a drainage channel of closed space by a vibrating member, e.g. by a piston or a Diaphragm is enlarged or reduced in size, wherein, during the expansion of the pump chamber, a valve arranged in the supply channel and a valve arranged in the discharge channel Valve are closed and when the pump contents are compressed, the valve arranged in the feed channel closed and v / earth the valve in the drainage channel opened.

In contrast to pump systems, which use the liquid or the organ conveying gases is continuously driven in a circular motion, so that an approximately constant delivery pressure

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is given, the delivery pressure in this system changes with each stroke in piston pump systems. With compression The pressure of the pump chamber rises, while it falls when the pump chamber expands. For a variety of These pressure fluctuations are insignificant in areas of application, while such pressure fluctuations are for other areas of application can be disadvantageous. On the other hand, alternating the pump pressure may even be desirable for certain tasks be.

This is the case, for example, with inkjet pens for conveying the writing ink from a reservoir to a writing head. During the writing operation, the Writing ink can be continuously fed to the writing head, while the pump pressure is as high as possible after the end of a writing phase should drop steeply. For this purpose, pump systems are to be used, the displacement of which is so large that there is sufficient ink liquid can be promoted for a write cycle during a single piston stroke. On the other hand will the requirement is that the pump pressure remains constant during the compression phase, i.e. the delivery phase, so that there is no impairment of the writing operation. The liquid pressure should namely be constant in such a way that it protrudes convexly at the writing nozzle, which has a capillary effect on the ink liquid, but is neither squeezed out of this nozzle nor dripping out. The ink liquid that has emerged convexly becomes Accelerated by an electric field drop by drop in the direction of the writing point and corresponding to the one to be written Distracted character contour. On the other hand, this working pressure should drop steeply at the end of the writing phase.

It is the object of the invention to provide a pump system that the conditions after a constant working

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pressure and guaranteed after a steep build-up of the working pressure or reduction of this working pressure.

A pump system that, using a pump diaphragm, fully meets the requirements fulfilled, is characterized according to the invention in that the acting on the pump membrane element against each other Actuators of an electromagnet and a spring element each have a large area and plan Have membrane plane parallel actuating surface and a cone-like actuating surface aligned away from the membrane plane, so that after reaching the working pressure the changes in the magnetic or spring forces caused by the changes in path due to the change in the the membrane element acting Flächai of the actuating elements are compensated

These measures according to the invention lead to the fact that when the large-area, planar and membrane becomes effective parallel actuation surface of the actuating member influenced by the electromagnet immediately steeply the working pressure is built up in the ink liquid and when the actuator is further immersed in addition to the large-area, planar and parallel to the membrane, the cone-like surface that fls away from the membrane to the side Actuating surface acts successively on the membrane, whereby the active surface of the actuating member is enlarged. By appropriate design of this cone-like actuating surface aligned away from the membrane, the active surface increases proportionally to the during of the immersion process increasing force of the electromagnet on its armature, so that the pressure within the ink liquid remains constant. A uniform conveyance "of the ink liquid necessary for the writing operation

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to the nozzle of the writing head Mn is guaranteed.

A "preferred embodiment of the invention Pump ensyst one is characterized by its use a largely reaction-free membrane element with great expansion and low adjustment height. This ensures that changes are made to the conditions can be largely prevented during the delivery process for the ink liquid and that the pressure within the ink liquid to be conveyed is approximately proportional to the excitation current of the electromagnet.

Is preferable to use, as plunger magnets \ opposite hinged armature magnets have a better for these purposes tightening torque for operating the membrane element a solenoid plunger magnet.

To the changes in the adjustment by the electromagnet and to keep the forces acting on their actuators within a narrow range are advantageous on the one hand, the use of an upper, the location of membrane and magnet armature at the beginning of the stroke defining stop and, on the other hand, the use of a lower one Stop that: Limits the stroke before the magnetic force of the armature causes the ink pressure to be too high.

An embodiment of a piston pump device according to the invention for conveying ink liquid in ink jet pens is shown in detail with reference to the drawing described below. It shows:

1 shows a simplified representation of the pump arrangement

in cut and
2 shows the pressure curve of the pump system reproducing

Diagram.

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The piston pump system is designed as a diaphragm pump, which means that the expansion or compression of the pump chamber 2 takes place via a diaphragm 1. A plunger magnet 5 and a mechanical spring element 6 act on this membrane 1 against each other via a plunger plate 3 »4 in its upper position, so that the pump chamber 2 has its greatest extent. If the plunger magnet 5 is now excited, the plunger plate 3 arranged on the magnet armature builds up the working pressure for the ink liquid with its planar actuating surface 7 via the membrane 1. A plate 9 arranged in a chamber 8 closes the feed channel 10. As a result of the large expansion of the plunger plate, only a relatively low pressure is built up in the pump system, so that the pressure fluid is brought to the outlet nozzle 14 and emerges convexly at the outlet opening, but does not flow out or drip out further. (The ink that has emerged convexly is accelerated by an electric field drop by drop in the direction of the writing point and deflected according to the character contour to be written).

Due to the design of the plunger plate 3 with a large diameter, only very small anchor lifts required. But even with these short anchor strokes, one treads the path covered corresponding change to the. Magnetic armature acting on magnetic forces. Without appropriate action, this would with increasing immersion depth of the plunger plate in the pump chamber to an increase in the pressure forces in the ink

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lead liquid, so that undesirably this ink liquid flows out at the outlet opening of the writing nozzle. In order to achieve the desired uniform pressure regardless of the position of the magnet armature on the ink liquid, the edges of the plunger plate 3 are flattened in a cone-like manner. With this design of the plunger plate 3, when this plunger plate 3 is immersed in the membrane, the effective area increases corresponding to the increase in the forces acting on its armature by the magnet, so that the specific pressure in the ink liquid remains the same. For the same reasons, the edges of the tappet plate 4, on which the spring element 6 acts, are also flattened in a cone-like manner. TJm restrict the changes in the forces acting on their actuators 3, 4 during adjustment by the electromagnet 5 and the spring 6, the adjustment path of these actuators 3, 4 is limited by stationary stops on the pump housing.

If the plunger magnet 5 is de-energized, the pump space is due to that acting on the diaphragm 1 via the tappet plate 4 Force of the spring 6 tries to expand. This means that there is one in the entire pump system right through to the writing nozzle there was a steep drop in pressure. Since the nozzle 14 is capillary acts on the ink liquid and thus acts like a closed valve, is used to fill the. Expanding Pump chamber required ink liquid from a reservoir, not shown, via the inflow channel 10, of the valve plate due to only extremely small pressure differences lifted off and the chamber 8 sucked in. In this Chamber 8 channels 15 are provided so that through the plate 9 the channel leading into the pump room is not closed.

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This valve plate 9 is a glass plate approximately 0.15 mm thick. Such a plate is sufficient Low in mass and does not stick inadvertently to the support surface in the chamber 8. This check valve does not need to be absolutely tight. The leakage current should only be small compared to the current towards the nozzle be. It is even necessary that a slow pressure equalization, e.g. in the case of temperature-related volume changes can take place in the ink system. For this purpose, the contact surface for the valve plate is slightly roughened or provided with a notch.

The uniformity of the ink liquid pressure generated by the pump system can be seen from the diagram according to FIG. To the. At time t = 0, the pressure rises steeply and only swings by an extremely small amount above the working pressure in order to immediately assume this working pressure. This working pressure is maintained continuously until an equally steep drop in the ink liquid pressure is recorded when the magnet system is de-energized at time t = t _1. The elasticity of the flexible supply hose 12 prevents even steeper changes in the fluid pressure when the electromagnet is energized or de-energized, but it contributes to damping the pressure peaks that occur when the pressure changes.

5 claims
2 figures

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Claims (1)

Pat en tan claims 1J diaphragm pump for pumping small amounts of liquid, in particular for inkjet pens for conveying the writing ink by influencing one another in opposite directions of the membrane element in interaction by an electromagnet and a spring element of one Reservoir for the · write head, of its small-caliber Exit opening the writing ink only by the influence of an electromagnetic field in the direction is promoted and diverted to the writing point, characterized in that the on · The pump membrane element (1) counteracting actuating members (3, 4) of an electromagnet (5) and one Spring element (6) each a large area planar and parallel to the membrane actuating surface and at least one of them have a cone-like actuating surface aligned away from the membrane plane, so that after reaching of the working pressure, the changes in the magnetic or spring forces caused by the changes in travel Changes in the areas of the actuating elements (3, 4) acting on the membrane element (1) can be compensated for. 2. Diaphragm pump according to claim 1, characterized through the use of a largely non-reactive membrane element (1) with a large expansion and a small one Adjustment height. 3. Diaphragm pump according to claim 1 or 2, marked "Iin e t through the use of a plunger magnet system (5) for actuating the membrane element (1) via the actuating element (3). VPA 9/240 / 1058b -9- 209884/0668 4. Diaphragm pump according to one of claims 1 to 3, characterized by using an upper one, the position of the diaphragm and armature at the beginning of the stroke . defining stop. 5. Diaphragm pump according to one of claims 1 to 4 »characterized through the use of a lower . Impact that limits the stroke before the magnetic force of the anchor3 causes the ink pressure to be too high. VPA 9/240 / 1058b 20S88 4 / U668 40 . Blank page