DE2164406A1 - Device for supplying writing fluid to the tip of the ejection tube of liquid jet pens - Google Patents

Description

© IPL.-ING. DIETER 3ANDf * 218 / 13.742 DE

DR.- ING ·. M ΑΓ! 7REp BONING

i '"December ^{21, 1971}

TELEPHONE 832 40 66

Pat. Entanglement

of the company

PAILLARD S.A.

Sainte-Croix (Vaud, Switzerland)

Device for supplying writing fluid to the tip of the ejection tube of liquid jet pens

The invention relates to a device for feeding of writing fluid to the tip of the ejection tube of liquid jet pens, where the pressure is the Ink in the ejector tube is stabilized approximately to the value that the formation of a convex meniscus at the ejector tube tip guaranteed, with an outflow in

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Form of an ink jet with a very small cross-section only occurs when this meniscus is under the action a certain value of an electric field.

Such a device has already been used, e.g. in the patent application No. P 16 73 979.0 of 19 January 1968 and in the, under No. 1 673 980 published and deposited on 19 January 1968 Patent application described. A means for supplying ink to the tip of the ejector tube was also provided in patent specification No. 1,252,424 dated October 20, 1964 described. With this writing method, the best results are achieved when the ink pressure in the ejector tube is only slightly lower than the pressure that would cause the ink to run out in the absence of the electric field. Under these conditions, however, the device is very sensitive and it can happen that

electrical
Even when the field is switched off, ink flows out under the influence of external influences. It is obvious that such an outflow of ink, as it can be triggered, for example, by untimely changes in pressure, vibrations or shocks of the machine containing the writing device, is undesirable. Any unintentional leakage from the ejection tube can contaminate the outer surfaces of the same and the electrodes and the perfect centering of the ink jet, as well

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jeopardize the accuracy of its deflection by the electrodes.

In the German patent specification No. 1 252 424 a solution has been proposed for this problem, in which between Ink tank and ejector tip an electrically controllable pump is provided, which is of a significant starting from a lower pressure, under the action of a, with the activation of the electric field to expel the Inkjet synchronized electrical control that quickly creates operating pressure.

However, the described in the aforementioned patent, electromagnetic pumps have a discontinuous working cycle. After a certain number of characters a rest time is required to allow the piston to return to the starting position. In applications where a large number of lines have to be written without interruption, accordingly, a continuous pace pump is desirable. This type of pump generally has the Disadvantage of a relatively slow production of the operating pressure during the start-up process. This relative Slowness requires a corresponding time difference between the point in time at which the pump is switched on

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is and at which the key that triggers the writing process is actuated in turn and the time at that the writing process can effectively begin, with the operating pressure being reached.

The present invention relates to a device for Feeding of writing fluid from a storage container to the tip of the ejection tube of liquid jet pens, in which a convex meniscus is formed at the exit of the discharge tube by hydrostatic pressure which is generated by means of a pump located between the storage container and the discharge tube tip, the Ink jet generated by an electric field, characterized in that the pump for a continuous Gait is formed, wherein means are provided to the operating pressure in the area of the discharge tube from the value required to form a convex meniscus to a value at which the ink remains as possible in the interior of the discharge tube and wherein a control device acts on these means to them putting each out of service and restoring pressure to form the meniscus at the beginning of each Ensure writing period.

The accompanying drawing shows a schematic and example

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one embodiment and a variant of the device according to the invention.

Show in it:

Fig. 1 is a vertical section of this embodiment,

Fig. 2 shows a longitudinal section through a writing head in which the ejection tube is installed, with a schematic representation of the electrical circuit for controlling the device,

Fig. 3> ^a , y & ^{un (} ä 3c on an enlarged scale the end of an exhaust pipe in different operating states,

Fig. 4 shows a vertical section through a pump according to the execution variant,

Fig. 5 is a plan view of the effective side of the rotor of this pump,

6 is a view of the other side of the rotor. With reference to Fig. 1, the illustrated pump JL is a scroll pump. It includes two flanges 12 and ^ x. ^{the A}

4th
rohrVfesthalten in which a rotor £ ^m it Archimedean spiral 6 rotating. The tightness between the pipe 4_ and the flanges 2_ and J £ is ensured by rubber rings 2. ^and ü S ^e

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ensures. The rotor ^ is extended to the right by an axis 2, which penetrates the surface 2j_ with the interposition of a seal 10, which is held in a recess 11 of the flange by a stop disk 12_. The rotor 5_ is driven by a pinion 1 ~ 5, which is attached to the axis £ by a screw 14_.

Above the pipe ^ between the puddles 2_ and 2, a cylindrical chamber I ^ is provided, the tightness of which is guaranteed by a pack 1 (5.

An opening 15 opens into the chamber 15 and supplies the ink coming from a container (not shown). A channel I ^ connects the chamber 15_ with the inlet chamber 20_ of the pump. At the other end of the rotor of the latter there is the outlet chamber 21, which is connected to the exhaust pipe ₂ by means of the pipe Y (Fig. 2) P via an outlet duct 2Ji 1.

A channel 25_ connects the outlet _{chamber 2J 1 of} the pump with the chamber 15. Via the chamber 15 "a direct connection between the inlet and outlet chambers 20_ and 21 of the pump is established through the channels 1 and 24 and consequently forms a two-way line (Bypass). This connection via the chamber 15_ can be achieved by means of a valve

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are interrupted, which has a valve disk 25_, the circumference of which is provided with a sealing ring 26 ^ made of rubber, which sits in an annular groove 2 £. The valve disk 2Ji is under the action of a spring 28 which tries to press it against the valve seat 2_2_.

The valve disk 25_ is guided by a spherical bearing _3JD, that belongs to the shaft ^ l, which is replaced by a nut ^ 2_ is attached to the paddock 2_. This spherical bearing penetrates into a hole j53_ in the valve disk.

With its end opposite the valve disk 25_, the spring 2j8 is supported on the collar j54 of a displaceable shaft 35 ' whose free end j56. with thread, cooperates with a knurled adjusting nut ^ L. This nut is in turn mounted in a hole '_3_8 of the flange ^. It is axially secured by means of a stop washer 12. and a spring washer j> 2. A rubber ring 40 ensures the tightness between the displaceable shaft ^ 5 and the flange ^ jl. On the other hand, the collar is secured against rotation by a pin _4l inserted into the slot 42_.

It can be seen that when the nut JJ is rotated, the shaft 35 slides in the flange ^ and that the spring 28

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force exerted on the valve disk 25_ on the desired Value can be set.

The guide shaft jjl of the valve disk is drilled through along its entire length. It is traversed by a coaxial control shaft 4j5, the end 44_ of which can be supported on the bottom 4_5_ of the bore 22 of ^the valve disk 25 under the action of a spring 46 ^ , which is on the one hand on the collar 4j_ of the shaft 4 ^ and on the other hand against the stop 48 , which is fastened to the flange 2_ by a screw 4 £. The force of the spring 4J5 is significantly larger than that of the spring 28 so that the control shaft 4J5 2J5, literally lifts the valve disk off its seat 2_2 and restores the free passage of the ink through the Doppelwegleitung 24, 1 £.

On the other hand, the tax authority penetrates an excitation coil

50 of an electromagnet, whose sleeve-shaped plunger core

51 made of soft iron sits on the shaft 4j5. When the electromagnet is not excited, the control shaft 4j5 is in the starting position and the core 5_1 is partially outside the winding. As soon as a current of sufficient intensity flows through the winding 5_0_, the core 5_1 dips into the interior of the winding 5_0 in the direction of the arrow F1 . The end 44 of the shaft ^ 1_ is moved away from the valve disk 25_.

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moves and this is pressed against its seat by the spring 2_8, whereby the closure of the two-way line 24 15 19, as shown in FIG. 1, is effected.

2 shows a write head already described in patent application No. P 16 73 979.0 of 19.I.68, of which only the elements required for a better understanding of the operation of the device are mentioned. A tube 5_2_ for ejecting the ink jet is held by an arbor-shaped insulating element 5J> which is attached to a central, basically cylindrical metal body ^ 4. A diaphragm 5_5_ with a circular bore 60, which is centered on the tube 52 , forms one of the electrodes for generating the electric field for ejecting the ink jet, the other consisting of the ejection tube 5j2 itself.

The diaphragm 5_5_ and the discharge tube 5J2 are on. applied to the two poles a_ and b_ of a power supply unit. A second power supply part 5J £ serves to feed the electromagnet 50, 51 * which is connected to the terminals c and d. The two power supply parts ^ 6, and 5X can, as already known, be switched on by a control pulse that is generated by logic circuits 5Q ₁ , which are combined with those that control the

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press the voltages on the deflection electrodes 22_ des Control the print head.

The operation of the device is as follows: When a printing unit, which works according to the writing method with ink jet, is energized, the motor for driving the pump is set in motion and the rotor is driven to rotate. Since initially the whole currents ψ mung circle was filled with ink, the spiral is achimedische this fluid due to its viscosity in the direction of arrow F2_ promote. However, as long as a control pulse has not been supplied by the logic circuit ^ 8 the power supply parts 56 and 5Z, the electromagnets ^ne ^ * is 50j 51 is not energized and the control shaft 4 ^> holds, under the action of its spring 46, the valve plate 2 ^ j _- open. Under this condition, the rotor ^. amount of ink conveyed in a closed circle via the two-way

™ line 24 _f 15, Ig _- circulate. Only the losses due to friction of the fluid in the flow circuit will generate a slight overpressure in the exhale tube ^ j2_ in relation to air pressure, so that the liquid in the ejection tube 52 yo changes from that shown in Fig jja 'position shown. In the of FIG..

As soon as the write command is given to the printing unit, the logic circuits generate a control pulse, the

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the two current supply members is transmitted 5jo 5_J_ and, either simultaneously or with a predetermined delay for the power supply part 57 "The electric field is produced on the one hand between the electrodes 5J2 and 55, and on the other hand the solenoid 50. 51 is energized. The control shaft 4 ^ 5 is shifted against the action of the spring 46_ in the direction of the arrow Fl ₁ to allow the valve disk 25_ to come to rest very quickly on its seat 29_ under the action of the spring 28 , and the double-way line 24, 15, 19 to close.

The full pressure of the pump is thus transferred to the ink that is located in the ejection tube 5_2 and is immediately thrown out by the electric field in the form of a jet with a very small cross section. It should be noted that the slight pressure surge, which causes the very rapid closure of the valve disk 25_, facilitates the start of the jet formation. By choosing the appropriate force of the spring 28, which acts on the valve disk, a very precise setting of the pressure in the discharge tube is achieved because, as soon as the liquid pressure exceeds a pressure corresponding to the force of the spring 28, the valve disk 25_ is again opens and allows the dual-way line to exert a regulating effect. An exact setting of this pressure according to regulations

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BATH ORIGINAL

is achieved by turning the knurled nut 37 " until the conditions shown in FIG. 3 ° are achieved in the absence of the electric field and which correspond to the optimal operating state of the write head. It can thus be seen that the double-way line 24, 15, 19 serves as a means to reduce the operating pressure in the discharge tube 5_2 from the value required to form the convex ink meniscus 5_9_ of FIG. 3c to a value at which the

fc ink, as shown in Fig. 3b, inside the ejection

pipe 5_2_ remains. These means are disabled by the control device, which consists of the logic circuits 58, the power supply part 5.X and the electromagnet 50, 51 , in order to restore the pressure required for the formation of the meniscus 5_ £ of FIG. 3c.

In certain applications of the device according to the invention, the electric field between ψ the ejector tube 5J2 and the diaphragm 55 » from the time the printing unit is switched on could preferably be maintained continuously. The power supply part 5j6 is not yet controlled by the logic circuits 5_8.

The variant shown in FIGS. 4 to 6 shows a solution in which the production and / or the suppression of the ink pressure without the help of one from the pump

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separate double-way line can be achieved. In this case, as shown in FIG. 4, the pump comprises a first flange 6l_ with a cylindrical recess 6j2 which is concentric ^{to the axis XX 1.} This cylindrical recess is defined by a second circular flange 63, which consists of non-magnetic material and the flange 6I in the thread 64 ^ _- is screwed. A packing 6> 5_ ensures the tightness between the two parts. A shaft 66 ^ passes through the lower part 6 £ of the flange 6_1_ in the axis X-X '. At its outer end it carries a pinion 68 which is fastened by the pin 6 and is driven in rotation by a motor (not shown). The other end of the shaft 66 penetrates into the recess 62 and ends with a triangular part 110 which is delimited by a collar 111. A disk 112 presses on a packing 113 * which ensures the tightness between the shaft 66 and the flange 6l_.

The eotor 114 of the pump is housed in the interior of the recess centered on the axis XX ', which is at least partly made of magnetic material.

The rotor is limited at the top by a circular, flat surface 115 in which a spiral channel 116 is incorporated. As can be seen from Fig. 5,

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the beginning of this channel starts from the central depression 117 and ends after several turns at the circumference of the circular surface 115,

The rotor 114 is driven in rotation by means of a device shown in FIG. 6, consisting of a three-armed spring Il8, which is loaded through a central, triangular bore 119 on the triangular part 110 of the shaft 66 . is consolidated. Each of the arms of this spring 118 has

Near its end a notch 120 in which three lugs 121 on the lower side of the rotor engage. The spring 118 is designed in such a way that it tends to press the rotor 114 against the collar 111 of the shaft. In this position, the circular, flat surface 115 of the rotor is at a small distance from a disk 122 which is attached to the lower side of the flange 6j5 and centered ^{on the axis XX 1.} This disk can preferably consist of glass and its side facing the surface 115 of the rotor is polished to a mirror finish.

The flange € r £ has an annular recess 123 in which a magnet core 124 with a U-shaped cross-section made of soft iron is housed and which contains an exciter winding 125 .

A channel 126 for supplying the pressurized

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Liquid connects the recess 6j2 of the pump with an outer container (not shown). On the other hand, an outlet channel 127 allows the pressure fluid to flow through the flange 6j5 in the direction of the ejection tube of a writing device direction, not shown.

The mode of operation of this pump is as follows: The pump is initially made ready for operation, the recess 62 and the inlet and outlet channels 126 and 127 being filled with writing fluid.

The rotor 114 is continuously driven in the direction of the arrow FlO . The excitation winding 125 is not under tension between the writing periods and the rotor is held in the position shown in FIG. 4, namely pressed against the collar 111 of the shaft 116 by the spring 118. The small distance between the surface 11 ^ S of the rotor 114 and the glass pane 122 forms a two-way line between the central depression 117 and the recess 62 through which the liquid, which could be conveyed by the spiral II6 towards the center, to the recess 62 again can be added. The same fluid pressure prevails on the outlet side as on the inlet side of the pump.

At the beginning of a writing period, the _: \ excitation development

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125 energized.

The magnetic field that is generated in the magnetic circuit 124 attracts the rotor 114 in such a way that its circular, flat surface 115 is pressed against the polished side of the glass plate 122. From this point on, the operating pressure is established at the outlet of the pump, the liquid being conveyed in the spiral-shaped channel by the effect of viscosity. The piston effect, which is caused by the rapid tightening of the rotor when the power is switched on, helps to establish the operating pressure quickly.

This operating pressure can be set very precisely by controlling the current intensity in the excitation winding 125. For this purpose, as soon as the liquid pressure balances the attraction force of the magnetic circuit (taking into account the restoring force of the spring 11 $), the rotor tries to move away from the surface of the disk 122 and the liquid can escape from the spiral-shaped channel II6. It can be seen that a simple voltage divider in the excitation circuit is sufficient to carry out this setting. A very adaptable program for regulating the pressure can also be created by controlling the excitation current by electronic means.

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The embodiment described is particularly suitable with regard to the production of the two flanges and even of the rotor made of injection-molded plastic. As for the latter, the attachment would be on its underside a disk made of magnetic material, which would serve as a movable magnetic core.

The magnetic circuit formed by the core 124 and the rotor 114 has an air gap that is large enough to prevent changes in the axial position of the rotor 114 in the operative position from significantly influencing the reluctance of the magnetic circuit «

Of course, other variants are conceivable, in particular, the axial displacement of the rotor may be controlled in IL4 direction of the disk 122 mechanically, eg _f by shifting the shaft 66 on which the rotor would be attached. The spiral-shaped channel could also be provided on a stationary part of the pump, with the rotor having a smooth surface or also a spiral-shaped channel.

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Claims (10)

"IPI.-ING. DIETER JANDIR Dft-ING MANFRED ΒΟΝίΝβ ^DR> PATEfiiANWÄLTl 218 / 13.742 DE BERlHM 33 (DAHlIM) X ^ V December 21, 1971 Patent registration of the company PAILIARD S.A. Sainte-Croix (Vaud, Switzerland) Θ Claims Device for supplying writing fluid from a storage container to the tip of the discharge tube (52) of liquid jet pens that have a convex meniscus of ink passing through the tip of the ejector tube a hydrostatic pressure is formed, which by means of a between the storage container and the discharge tube (52) lying pump is generated, whereby the ink jet is generated by an electric field, thereby ge - 2 209830/0626 indicates that the pump (l) is for continuous Gait is formed, with means (19, 24, 25, 43, 50) are provided in order to reduce the operating pressure of the required value in the area of the discharge tube (52) Reduce the formation of a convex meniscus to a value at which the ink is as inside as possible of the discharge tube remains, and wherein a control device acts on these means to each putting out of service and restoring pressure to form the meniscus at the beginning of each Ensure writing period. 2. Device according to claim 1, characterized in that the means for reducing the operating pressure consist of a double-way line (19 * 24, I5), which connect the output and the input of the pump, with a valve (25, 29) that closes or respectively to open this double-ended line through the circuit to control the writing process is controlled. 3. Device according to claims 1 and .2, characterized in that that the valve (25, 29) is in the closed position under the action of a spring that the Pressure at the outlet, which counteracts the pump to act as a valve - 3 209830 / Q626 til to regulate the said pressure. 4. Device according to claims 1 to ^, characterized in that that the valve head of said valve is actuated by one, under the action of a second spring standing shaft is lifted from its seat, this shaft under the action of an electromagnet stands, which acts against the spring force to allow the valve to close. 5. Device according to claim 1, characterized in that the pump consists of a first element (ll4) which on one side is limited by a surface of revolution in which a channel (116) is incorporated, the basically has the shape of a spiral which is approximately centered on the axis of this revolutionary surface and is open over at least part of its length, and consists of a second member (122) extending on one side is bounded by a second surface of revolution which is identical to the first surface and to this is concentric, these two surfaces lying inside a chamber (62) which is under pressure with the to be set liquid is filled, and one (114) of the two elements (114, 122) a rotational movement in relation to the second (122) to one to - 4 209830/0626 this axis of rotation executes common axis, and means are provided for axial displacement of the one element (114) in relation to the other (122) to both surfaces of revolution, opposite to the Effect of the positive pressure to press against each other, 6. Device according to claims 1 and 4, characterized in that that the pump has magnetic means (124, 125) for moving an element (ll4) against the other (122). 7 · Device according to claims 1, 5 and 6, thereby characterized in that the element (ll4) driven in rotation is axially displaceable and at least consists partly of magnetic material, its axial displacement being caused by a fixed, electromagnetic winding (125) is effected. 8. Device according to claims 1 and 5 to 7 , characterized in that the winding (125) is arranged outside the chamber (62) * 9. Device according to claims 1 and 5 to 8, characterized characterized in that the rotationally driven element (114) comprises said helical channel (116). - 5 209830/0626 216440B 10. Device according to claims 1 and 5 to 9 *, characterized in that the rotationally driven element (11 ^) is mounted on resilient arms positively connected to the shaft {66) , which strive to this element (ll4) from the other (122) to remove. 20 9830/0626