CA1050097A - Marking method and apparatus - Google Patents
Marking method and apparatusInfo
- Publication number
- CA1050097A CA1050097A CA237,306A CA237306A CA1050097A CA 1050097 A CA1050097 A CA 1050097A CA 237306 A CA237306 A CA 237306A CA 1050097 A CA1050097 A CA 1050097A
- Authority
- CA
- Canada
- Prior art keywords
- electrode
- marking liquid
- droplets
- shaft
- marking
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/015—Ink jet characterised by the jet generation process
- B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
- B41J2/06—Ink jet characterised by the jet generation process generating single droplets or particles on demand by electric or magnetic field
- B41J2/065—Ink jet characterised by the jet generation process generating single droplets or particles on demand by electric or magnetic field involving the preliminary making of ink protuberances
Landscapes
- Particle Formation And Scattering Control In Inkjet Printers (AREA)
- Printers Or Recording Devices Using Electromagnetic And Radiation Means (AREA)
Abstract
MARKING METHOD AND APPARATUS
Abstract of the Disclosure A method and apparatus are provided for providing droplets that are suitable to mark a recording surface with a high degree of resolution and which are quickly responsive to electrical input. A shaft electrode is positioned with respect to a supply of marking liquid such that its propellant end is just above the surface of the marking liquid. A field is established between the shaft electrode and one external electrode causing droplets to be propelled from the marking liquid supply covering the shaft electrode onto record receiv-ing means.
Abstract of the Disclosure A method and apparatus are provided for providing droplets that are suitable to mark a recording surface with a high degree of resolution and which are quickly responsive to electrical input. A shaft electrode is positioned with respect to a supply of marking liquid such that its propellant end is just above the surface of the marking liquid. A field is established between the shaft electrode and one external electrode causing droplets to be propelled from the marking liquid supply covering the shaft electrode onto record receiv-ing means.
Description
105009~
The invention relates to marking of recording surfaces.
The prior art, typified by UK patent nos 1,148,771 and 1,064,344 discloses the marking of recording surfaces responsive to electrical signals by means of ink jets and styli.
One method of marking so disclosed operates with physical contact between a liquid fed stylus and the recording surface, said physical contact being interrupted in accordance with a signal. Interruption of physical contact is hard to control with high speeds and with a fast flow of intelligence requires a highly damped non-elastic mechanical system. The large amount of distortion free power required to operate such a system at higher speeds, such as lO kcs or higher, results in high initial cost and a very low level of operating efficiency.
Another marking device so disclosed is commonly referred to as an 'ink spitter' or 'ink jet' and includes devices in which liquid is transferred across a gap from a point or orifice on to the recording surface responsive directly to an electrical force or to controlled pressure in the feed system. Such devices are limited by the energy required to move a particle across a gap.
Factors such as inertia and surface tension must be over-come, both being extremely difficult at high frequency
The invention relates to marking of recording surfaces.
The prior art, typified by UK patent nos 1,148,771 and 1,064,344 discloses the marking of recording surfaces responsive to electrical signals by means of ink jets and styli.
One method of marking so disclosed operates with physical contact between a liquid fed stylus and the recording surface, said physical contact being interrupted in accordance with a signal. Interruption of physical contact is hard to control with high speeds and with a fast flow of intelligence requires a highly damped non-elastic mechanical system. The large amount of distortion free power required to operate such a system at higher speeds, such as lO kcs or higher, results in high initial cost and a very low level of operating efficiency.
Another marking device so disclosed is commonly referred to as an 'ink spitter' or 'ink jet' and includes devices in which liquid is transferred across a gap from a point or orifice on to the recording surface responsive directly to an electrical force or to controlled pressure in the feed system. Such devices are limited by the energy required to move a particle across a gap.
Factors such as inertia and surface tension must be over-come, both being extremely difficult at high frequency
- 2 -rates. For example, in drops of sizes suitable for recording purposes, it is estimated that the potential required to move the drops across a one mil gap at 10 kcs is in the range of 30,000 volts/cm, which is also about the potential required to produce undesirable air break-down. If it is also necessary to completely overcome surface tenstion by electrical potential, the useable frequency is greatly reduced.
Another category of such marking devices so disclosed is one in which a liquid fed stylus is maintained in constant contact with the recording surface and is moved relative to the recording sheet in order to record information. Such a device provides a continuous mark on the recording surface at all times when the stylus and the recording surface are in contact. Such a device is fairly limited in practical application to oscillogra-phic use, and it becomes quite complex to control a continuously mar~ing stylus through the tortuous configu-rations necessary for most sophisticated writing.
Disclosed in UK patent no 1,064,344 is a stylus marking device capable of fast turn on and inter-ruption of liquid flow from a stylus which is in continuous contact with the recording surface. Such a device contemplates the liquid being held in the stylus while 1~50097 a high voltage signal across the stylus and recording sheet is applied in order to effect rapid flow of the liquid. Removal of the high voltage signal results in interruption of the liquid flow, although the stylus remains in contact with the recording surface. Although capable of solving many of the prior art problems, such a device in general application requires a high voltage supply and embodies a single stylus in contact with a recording surface which is rotated many times as the stylus moves across the surface so that eventually the point of the stylus covers most of the surfaces area.
Such methods are generally so slow as to be undesirable and require undesirably high voltages.
Also known in the prior art is the device and method disclosed in US patent no 2,143,376 wherein recording fluid is held in an open ended container and drawn therefrom on to a recording surface interposed between the open ended fluid container and a conductive element when electrical energy is applied to the conductive element. A series of such fluid containing containers and matching conductive elements may be arranged across the path of a recording surface so as to simultaneously mark at least portions of a line on a recording surface as the surface moves between the fluid containers and the 1~50097 conductive elements. Such a device is subject to limitations of speed and definition~ The clarity and resolution of the images produced by such a marking device are physically limited by the number of sets of open ended fluid containers and conductive elements which may be placed side by side in line across the paper path.
The voltage requirements of such a device are found to be undesirably high for many applications.
There is also known in the prior art, the apparatus for marking a recording surface described in US patent 2,600,129 wherein a fine stream of charged liquid particles are produced by creating a DC field between a nozzle or a point protruding from a liquid supply and an external annular electrode through which the stream passes. The external annular electrode has a focusing effect which allows the use of a comparatively small potential to move a stream of liquid particles over comparatively great distances; however, in many embodi-ments it is inconvenient to place an anular electrode between the source of the stream of particles and the recording surface. If, for example, the droplets are sought to emanate from a row of adjacent sources to selectively mark portions of a moving recording surface, the definition of the image thus created may be limited by the spacing between the sources required by the matching series of annular electrodes. It may also be inconvenient at times to be limited to the use of a direct current in order to establish a field.
In the marking of recording surfaces, especially in response to electrical impulses such as those provided by computers or facsimile devices it is often desirable to mark the recording surface as it moves past a row of closely spaced sources of liquid droplets which may be activated and inactivated rapidly so as to produce a high resolution image at high speed.
According to one aspect of the invention there is provided a method of propelling droplets of marking liquid which comprises:
(a) providing supply of marking liquid;
(b) positioning a shaft electrode so that a propellent end thereof extends to a position just above the operative surface level of the marking liquid supply; and ~c) establishing a field between the shaft electrode and at least one external electrode sufficient to cause droplets to be propelled from the marking liquid source covering the shaft electrode onto a record receiving means.
Such a method provides droplets which are quickly 10~V097 responsive to electrical input and which are suitable to mark a recording surface with a high degree of resolution.
The marking droplets may be, for example, propelled to the recording surface directly from a row of closely spaced independently driven shaft electrodes; or, if desired, the droplets may be deflected by an electric field prior to striking the recording surface.
According to another aspect of the invention there is provided an apparatus for marking a recording surface responsive to electrical input which comprises:
(a) a container for holding a supply of marking liquid;
(b) a shaft electrode positioned in the supply of marking liquid so that a propellent end thereof protrudes to a position just above the operative surface level of the marking liquid;
(c) a second electrode positioned so that a field may be created between it and said shaft electrode sufficient to cause a stream of drop-lets to emanate therefrom whenever a sufficient field is established between the electrodes; and (d~ a means for creating such a field between said electrodes.
lOS0097 A marking method and apparatus according to the present invention will now be described by way of example and with reference to the accompanying drawings wherein:
Fig 1 shows in cross-section one embodiment of an apparatus for performing the present invention.
Fig 2 shows in cross section the embodiment of Fig 1 wherein the marking liquid covers the tip of the shaft electrode.
Fig 3 shows in cross section the embodiment of Figs 1 and 2 wherein a stream of droplets of marking liquid are propelled from the shaft electrode to a recording surface.
Fig 4 shows in cross section an apparatus for performing the method of the present invention wherein a preferred shaft electrode is used.
Fig 5 shows in cross section an apparatus for performing the method of the present invention wherein the field is established between the shaft electrode and the marking liquid container.
Fig 6 shows schematically a means for marking a recording surface in imagewise fashion using the method of the present invention.
10S(3097 Fig 7 shows schematically an alternative means for making a recording surface by the method of the present invention wherein deflecting electrodes are employed to change the path of the marking liquid droplets.
Referring more specifically to Fig 1 there is shown in cross section an open ended container 1 which holds a supply of marking liquid 2. A shaft electrode 3 is positioned in the supply of marking liquid 2 in such a way that one end referred to as a propellent end, 3a protrudes to a position just above the operative surface level thereof. Positioned above the protruding end 3a of the shaft electrode 3 is a second electrode 4.
The shaft electrode 3 and the second electrode 4 may be made from any suitable conductive material.
Typically the electrodes are formed from conductive materials such as aluminium, copper and steel.
The protruding end 3a of the shaft electrode 3 may be positioned so that it protrudes any suitable distance from the operative surface level of the supply of marking liquid 2.
Typically the protruding end 3a extends at least about 0.020 inch above the surface of the supply of marking liquid 2.
Surprisingly it is observed that the movement of the droplets is unstable when the protruding end 3a extends less than about 0.020 inch above the surIace of the marking liquid 2.
That is the droplets are either not formed or are formed at irregular intervals and have irregular sizes~
However, distances of at least about 0.020 inch are observed to produce droplets of substantially regular size and spacing. It will be apparent to those skilled in the art that the maximum distance which the protruding end 3a may extend above the surface of the supply of marking liquid 2 is largely dependant upon such factors as the shape of the protruding end and the viscosity of the marking liquid 2. Such maximum distance will vary from case to case and may be optimized by experi-mentation in each case.
The shaft electrode 3 may be of any suitable shape and diameter. Typically the shaft electrode 3 has a diameter of from about 0.001 to about 0.010 inch, although a preferred shaft electrode 3 diameter is about 0.005 inch at its protruding end 3a because of the size of the droplet thus produced. The shaft electrode typically has a non-pointed protruding end 3a. It may be flat as shown in Fig 1 or rounded, although a rounded protruding end 3a is preferred because the droplets formed by such a shaft electrode 3 are found to be more accurately directed. It is observed that the droplets produced by a flat electrode eminate from various points lOS0097 on the flat surface and thus are not as well directed as the droplets produced by a rounded electrode end. An optimum configuration for the protruding end 3a of the shaft electrode 3 is a rounded surface which is covered with insulating material over its protruding portion.
It is believed the insulating tip of the protruding end has a beneficial effect on the direction and concentration of the lines of force between the shaft electrode 3 and the second electrode 4. Such an embodiment is described in greater detail in connection with Fig 4.
Although it is not essential, open ended con-tainer 1 may function as an external electrode as explained in greater detail in connection with the following illustrations.
The marking liquid 2 may be any suitable liquid.
Typically, it is a relatively insulating liquid having a viscosity of less than about 50 cps and a dielectric constant of from about 2 to about 3. The desirable resistivity of the marking liquid varies with the diameter of the shaft electrode. Generally, as the diameter of the shaft electrode becomes smaller the desired resistivity of the marking liquid is reduced. For example, satisfactory results have been obtained using a shaft electrode with a diameter of about 0.005 inch with a marking liquid having a resistivity of about 10 ohm cm, said marking liquid comprising light mineral oil having a viscosity of about 30 cps with 5 wt percent Antoron, a dispersant which is commercially available from General Analine Film Limited which is added to increase the conductivity. Th~ marking liquid may be colored with, for example, a suitable amount of carbon black or some other suitable dye or pigment to enhance its marking ability.
Referring more specifically to Fig 2 there is shown the embodiment of Fig l wherein an electrical poten-tial is established between the shaft electrode 3 and the second electrode 4. The marking liquid 2 has been drawn by the field to cover the protruding propellent end 3a of the shaft electrode 3. Although in this illustration the marking liquid 2 is drawn to cover the protruding end 3a of the shaft electrode 3 by the field, it is to be understood that the marking liquid could be so drawn by surface tension.
Although the function of the liquid covering the protruding end 3a of the shaft electrode 3 is not completely understood it is known to be important to the proper functioning of the method of the present invention that an amount of the marking liquid cover the protruding propellent end 3a. It is believed that the liquid so drawn may have a beneficial effect on the concentration and direction of the lines of force between the shaft electrode 3 and the external electrode 4 in addition to serving as a ~050097 supply for the droplets to be formed.
Re~erring more specifically now to Fig 3 there is shown in cross section an apparatus for performing the method the present invention wherein a stream of droplets 5 are moving from the protruding end 3a of the shaft electrode 3 toward the external electrode 4.
The stream of droplets 5 strikes and adheres to a recording surface 6. Although the recording surface 6 of Fig 3 is shown to be moving in a path defined by rollers 7 and 7a, it is to be understood that the recording surface may be stationery. Any suitable material may be used for the recording surface. Typically, plain paper is used.
Any suitable potential of either alternating or direct current may be established between the shaft electrode 3 and the external electrode 4 depending primarily upon the distance through which the droplets are sought to be propelled and the diameter of the protruding end 3a of the shaft electrode 3. It is observed that the potential necessary to produce a satisfactory stream of droplets is somewhat dependant upon the geometry of the protruding end 3a.
Typically a potential of from about 14,000 v/cm to about 30,000 v/cm may be used to propell the droplets when, for example, a rounded shaft electrode 3 having a protruding propellent end 3a diameter of about 0.005 inch is used.
It is understood that as the diameter of the protruding end 3a decreases a smaller potential will be sufficient to propell the 1a~50097 stream of droplets 5 toward the recording surface 6.
Additionally, a smaller potential may be used if the protruding end 3a is rounded than if it is flat; however, it is observed that a pointed protruding end is not useful.
A pointed protruding end tends to so concentrate the potential charge that it effects air breakdown before the droplets are created. This is thought to be caused by the undesirably high concentration of charge at the point and by the absence of sufficient marking liquid to cover the site of concentrated charge on the pointed protruding end of a shaft electrode.
It is also observed that potentials of greater than about 30,000 v/cm undesirably tend to result in air breakdown between the electrodes even when a shaft electrode with a flat protruding end is used.
It is observed that when a suitable potential is applied to an apparatus such as that described in connection with Figs 1, 2 and 3 there results immediate propulsion of a stream of regularly sized and spaced droplets away from the shaft electrode. The steam of droplets is also observed to cease immediately upon the removal of sufficient potential. The droplets have a size related somewhat to the diameter of the protruding end 3a of the shaft electrode 3.
lOSOQ97 Smaller electrode ends are observed to produce generally smaller droplets than those produced by larger electrodes. For example, it is observed that a shaft electrode having a protruding end with a diameter of about 0.005 inch and having a potential of about 20,000 v/cm applied will produce droplets of a suitable marking liquid having a diameter of about 0.005 inch and a spacing between droplets of about 0.005 inch.
It is to be understood that the rising of the marking liquid 2 to cover the protruding end 3a of the shaft electrode 3 as shown in Fig 2 may occur almost simultane-ously with the start of the flow of droplets therefrom.
Alternatively, however, especially in embodiments wherein it is desireable to produce intermittant bursts of droplets from the shaft electrode, as exemplified by the embodiment of Fig 6, a potential may be maintained on the shaft electrode sufficient to maintain a covering of marking liquid over the protruding end at all times.
Referring more specifically to Fig 4, there is shown a preferred embodiment of an apparatus for performing the method of the present invention. In Fig 4 the shaft electrode 3 is formed from a conductive metal and has a rounded protruding end 3a which is covered with an insulating material 8. Any suitable insulating material may be used. Typically insulating paints and varnishes are used as insulators.
The marking material container 1 of Fig 4 has a generally circular cross section along line 4-4 and is electrically connected with the second electrode 4 so that the container 1 and the second electrode 4 act together to establish a field with the shaft electrode.
Although not completely understood it is believed that the insulated, shaped protruding end 3a of the shaft electrode 3 and the establishing of a potential between the shaft electrode 3, the container 1 and the second electrode 4 cause a field having lines of force which aid in directing the stream of droplets 5 toward a very localiæed area on the recording surface 6.
Referring now to Fig 5 there is shown an alternative apparatus for performing the method of the present invention.
In this embodiment the potential is applied between a shaft electrode 3 and the conductive container 1 which becomes in effect the second electrode. It is observed that the application of a sufficient potential established between the shaft electrode and the container 1 will cause a stream of droplets 5 of substantially regular size and spacing to move away from the protruding propellent end 3a 10~S0097 of the shaft electrode 3 with sufficient velocity and volume to mark the recording material 6. Although satisfactory in its operation, it is observed that the path of the droplet stream 5 i5 slightly less regular when compared with the paths of the droplet streams of Fig
Another category of such marking devices so disclosed is one in which a liquid fed stylus is maintained in constant contact with the recording surface and is moved relative to the recording sheet in order to record information. Such a device provides a continuous mark on the recording surface at all times when the stylus and the recording surface are in contact. Such a device is fairly limited in practical application to oscillogra-phic use, and it becomes quite complex to control a continuously mar~ing stylus through the tortuous configu-rations necessary for most sophisticated writing.
Disclosed in UK patent no 1,064,344 is a stylus marking device capable of fast turn on and inter-ruption of liquid flow from a stylus which is in continuous contact with the recording surface. Such a device contemplates the liquid being held in the stylus while 1~50097 a high voltage signal across the stylus and recording sheet is applied in order to effect rapid flow of the liquid. Removal of the high voltage signal results in interruption of the liquid flow, although the stylus remains in contact with the recording surface. Although capable of solving many of the prior art problems, such a device in general application requires a high voltage supply and embodies a single stylus in contact with a recording surface which is rotated many times as the stylus moves across the surface so that eventually the point of the stylus covers most of the surfaces area.
Such methods are generally so slow as to be undesirable and require undesirably high voltages.
Also known in the prior art is the device and method disclosed in US patent no 2,143,376 wherein recording fluid is held in an open ended container and drawn therefrom on to a recording surface interposed between the open ended fluid container and a conductive element when electrical energy is applied to the conductive element. A series of such fluid containing containers and matching conductive elements may be arranged across the path of a recording surface so as to simultaneously mark at least portions of a line on a recording surface as the surface moves between the fluid containers and the 1~50097 conductive elements. Such a device is subject to limitations of speed and definition~ The clarity and resolution of the images produced by such a marking device are physically limited by the number of sets of open ended fluid containers and conductive elements which may be placed side by side in line across the paper path.
The voltage requirements of such a device are found to be undesirably high for many applications.
There is also known in the prior art, the apparatus for marking a recording surface described in US patent 2,600,129 wherein a fine stream of charged liquid particles are produced by creating a DC field between a nozzle or a point protruding from a liquid supply and an external annular electrode through which the stream passes. The external annular electrode has a focusing effect which allows the use of a comparatively small potential to move a stream of liquid particles over comparatively great distances; however, in many embodi-ments it is inconvenient to place an anular electrode between the source of the stream of particles and the recording surface. If, for example, the droplets are sought to emanate from a row of adjacent sources to selectively mark portions of a moving recording surface, the definition of the image thus created may be limited by the spacing between the sources required by the matching series of annular electrodes. It may also be inconvenient at times to be limited to the use of a direct current in order to establish a field.
In the marking of recording surfaces, especially in response to electrical impulses such as those provided by computers or facsimile devices it is often desirable to mark the recording surface as it moves past a row of closely spaced sources of liquid droplets which may be activated and inactivated rapidly so as to produce a high resolution image at high speed.
According to one aspect of the invention there is provided a method of propelling droplets of marking liquid which comprises:
(a) providing supply of marking liquid;
(b) positioning a shaft electrode so that a propellent end thereof extends to a position just above the operative surface level of the marking liquid supply; and ~c) establishing a field between the shaft electrode and at least one external electrode sufficient to cause droplets to be propelled from the marking liquid source covering the shaft electrode onto a record receiving means.
Such a method provides droplets which are quickly 10~V097 responsive to electrical input and which are suitable to mark a recording surface with a high degree of resolution.
The marking droplets may be, for example, propelled to the recording surface directly from a row of closely spaced independently driven shaft electrodes; or, if desired, the droplets may be deflected by an electric field prior to striking the recording surface.
According to another aspect of the invention there is provided an apparatus for marking a recording surface responsive to electrical input which comprises:
(a) a container for holding a supply of marking liquid;
(b) a shaft electrode positioned in the supply of marking liquid so that a propellent end thereof protrudes to a position just above the operative surface level of the marking liquid;
(c) a second electrode positioned so that a field may be created between it and said shaft electrode sufficient to cause a stream of drop-lets to emanate therefrom whenever a sufficient field is established between the electrodes; and (d~ a means for creating such a field between said electrodes.
lOS0097 A marking method and apparatus according to the present invention will now be described by way of example and with reference to the accompanying drawings wherein:
Fig 1 shows in cross-section one embodiment of an apparatus for performing the present invention.
Fig 2 shows in cross section the embodiment of Fig 1 wherein the marking liquid covers the tip of the shaft electrode.
Fig 3 shows in cross section the embodiment of Figs 1 and 2 wherein a stream of droplets of marking liquid are propelled from the shaft electrode to a recording surface.
Fig 4 shows in cross section an apparatus for performing the method of the present invention wherein a preferred shaft electrode is used.
Fig 5 shows in cross section an apparatus for performing the method of the present invention wherein the field is established between the shaft electrode and the marking liquid container.
Fig 6 shows schematically a means for marking a recording surface in imagewise fashion using the method of the present invention.
10S(3097 Fig 7 shows schematically an alternative means for making a recording surface by the method of the present invention wherein deflecting electrodes are employed to change the path of the marking liquid droplets.
Referring more specifically to Fig 1 there is shown in cross section an open ended container 1 which holds a supply of marking liquid 2. A shaft electrode 3 is positioned in the supply of marking liquid 2 in such a way that one end referred to as a propellent end, 3a protrudes to a position just above the operative surface level thereof. Positioned above the protruding end 3a of the shaft electrode 3 is a second electrode 4.
The shaft electrode 3 and the second electrode 4 may be made from any suitable conductive material.
Typically the electrodes are formed from conductive materials such as aluminium, copper and steel.
The protruding end 3a of the shaft electrode 3 may be positioned so that it protrudes any suitable distance from the operative surface level of the supply of marking liquid 2.
Typically the protruding end 3a extends at least about 0.020 inch above the surface of the supply of marking liquid 2.
Surprisingly it is observed that the movement of the droplets is unstable when the protruding end 3a extends less than about 0.020 inch above the surIace of the marking liquid 2.
That is the droplets are either not formed or are formed at irregular intervals and have irregular sizes~
However, distances of at least about 0.020 inch are observed to produce droplets of substantially regular size and spacing. It will be apparent to those skilled in the art that the maximum distance which the protruding end 3a may extend above the surface of the supply of marking liquid 2 is largely dependant upon such factors as the shape of the protruding end and the viscosity of the marking liquid 2. Such maximum distance will vary from case to case and may be optimized by experi-mentation in each case.
The shaft electrode 3 may be of any suitable shape and diameter. Typically the shaft electrode 3 has a diameter of from about 0.001 to about 0.010 inch, although a preferred shaft electrode 3 diameter is about 0.005 inch at its protruding end 3a because of the size of the droplet thus produced. The shaft electrode typically has a non-pointed protruding end 3a. It may be flat as shown in Fig 1 or rounded, although a rounded protruding end 3a is preferred because the droplets formed by such a shaft electrode 3 are found to be more accurately directed. It is observed that the droplets produced by a flat electrode eminate from various points lOS0097 on the flat surface and thus are not as well directed as the droplets produced by a rounded electrode end. An optimum configuration for the protruding end 3a of the shaft electrode 3 is a rounded surface which is covered with insulating material over its protruding portion.
It is believed the insulating tip of the protruding end has a beneficial effect on the direction and concentration of the lines of force between the shaft electrode 3 and the second electrode 4. Such an embodiment is described in greater detail in connection with Fig 4.
Although it is not essential, open ended con-tainer 1 may function as an external electrode as explained in greater detail in connection with the following illustrations.
The marking liquid 2 may be any suitable liquid.
Typically, it is a relatively insulating liquid having a viscosity of less than about 50 cps and a dielectric constant of from about 2 to about 3. The desirable resistivity of the marking liquid varies with the diameter of the shaft electrode. Generally, as the diameter of the shaft electrode becomes smaller the desired resistivity of the marking liquid is reduced. For example, satisfactory results have been obtained using a shaft electrode with a diameter of about 0.005 inch with a marking liquid having a resistivity of about 10 ohm cm, said marking liquid comprising light mineral oil having a viscosity of about 30 cps with 5 wt percent Antoron, a dispersant which is commercially available from General Analine Film Limited which is added to increase the conductivity. Th~ marking liquid may be colored with, for example, a suitable amount of carbon black or some other suitable dye or pigment to enhance its marking ability.
Referring more specifically to Fig 2 there is shown the embodiment of Fig l wherein an electrical poten-tial is established between the shaft electrode 3 and the second electrode 4. The marking liquid 2 has been drawn by the field to cover the protruding propellent end 3a of the shaft electrode 3. Although in this illustration the marking liquid 2 is drawn to cover the protruding end 3a of the shaft electrode 3 by the field, it is to be understood that the marking liquid could be so drawn by surface tension.
Although the function of the liquid covering the protruding end 3a of the shaft electrode 3 is not completely understood it is known to be important to the proper functioning of the method of the present invention that an amount of the marking liquid cover the protruding propellent end 3a. It is believed that the liquid so drawn may have a beneficial effect on the concentration and direction of the lines of force between the shaft electrode 3 and the external electrode 4 in addition to serving as a ~050097 supply for the droplets to be formed.
Re~erring more specifically now to Fig 3 there is shown in cross section an apparatus for performing the method the present invention wherein a stream of droplets 5 are moving from the protruding end 3a of the shaft electrode 3 toward the external electrode 4.
The stream of droplets 5 strikes and adheres to a recording surface 6. Although the recording surface 6 of Fig 3 is shown to be moving in a path defined by rollers 7 and 7a, it is to be understood that the recording surface may be stationery. Any suitable material may be used for the recording surface. Typically, plain paper is used.
Any suitable potential of either alternating or direct current may be established between the shaft electrode 3 and the external electrode 4 depending primarily upon the distance through which the droplets are sought to be propelled and the diameter of the protruding end 3a of the shaft electrode 3. It is observed that the potential necessary to produce a satisfactory stream of droplets is somewhat dependant upon the geometry of the protruding end 3a.
Typically a potential of from about 14,000 v/cm to about 30,000 v/cm may be used to propell the droplets when, for example, a rounded shaft electrode 3 having a protruding propellent end 3a diameter of about 0.005 inch is used.
It is understood that as the diameter of the protruding end 3a decreases a smaller potential will be sufficient to propell the 1a~50097 stream of droplets 5 toward the recording surface 6.
Additionally, a smaller potential may be used if the protruding end 3a is rounded than if it is flat; however, it is observed that a pointed protruding end is not useful.
A pointed protruding end tends to so concentrate the potential charge that it effects air breakdown before the droplets are created. This is thought to be caused by the undesirably high concentration of charge at the point and by the absence of sufficient marking liquid to cover the site of concentrated charge on the pointed protruding end of a shaft electrode.
It is also observed that potentials of greater than about 30,000 v/cm undesirably tend to result in air breakdown between the electrodes even when a shaft electrode with a flat protruding end is used.
It is observed that when a suitable potential is applied to an apparatus such as that described in connection with Figs 1, 2 and 3 there results immediate propulsion of a stream of regularly sized and spaced droplets away from the shaft electrode. The steam of droplets is also observed to cease immediately upon the removal of sufficient potential. The droplets have a size related somewhat to the diameter of the protruding end 3a of the shaft electrode 3.
lOSOQ97 Smaller electrode ends are observed to produce generally smaller droplets than those produced by larger electrodes. For example, it is observed that a shaft electrode having a protruding end with a diameter of about 0.005 inch and having a potential of about 20,000 v/cm applied will produce droplets of a suitable marking liquid having a diameter of about 0.005 inch and a spacing between droplets of about 0.005 inch.
It is to be understood that the rising of the marking liquid 2 to cover the protruding end 3a of the shaft electrode 3 as shown in Fig 2 may occur almost simultane-ously with the start of the flow of droplets therefrom.
Alternatively, however, especially in embodiments wherein it is desireable to produce intermittant bursts of droplets from the shaft electrode, as exemplified by the embodiment of Fig 6, a potential may be maintained on the shaft electrode sufficient to maintain a covering of marking liquid over the protruding end at all times.
Referring more specifically to Fig 4, there is shown a preferred embodiment of an apparatus for performing the method of the present invention. In Fig 4 the shaft electrode 3 is formed from a conductive metal and has a rounded protruding end 3a which is covered with an insulating material 8. Any suitable insulating material may be used. Typically insulating paints and varnishes are used as insulators.
The marking material container 1 of Fig 4 has a generally circular cross section along line 4-4 and is electrically connected with the second electrode 4 so that the container 1 and the second electrode 4 act together to establish a field with the shaft electrode.
Although not completely understood it is believed that the insulated, shaped protruding end 3a of the shaft electrode 3 and the establishing of a potential between the shaft electrode 3, the container 1 and the second electrode 4 cause a field having lines of force which aid in directing the stream of droplets 5 toward a very localiæed area on the recording surface 6.
Referring now to Fig 5 there is shown an alternative apparatus for performing the method of the present invention.
In this embodiment the potential is applied between a shaft electrode 3 and the conductive container 1 which becomes in effect the second electrode. It is observed that the application of a sufficient potential established between the shaft electrode and the container 1 will cause a stream of droplets 5 of substantially regular size and spacing to move away from the protruding propellent end 3a 10~S0097 of the shaft electrode 3 with sufficient velocity and volume to mark the recording material 6. Although satisfactory in its operation, it is observed that the path of the droplet stream 5 i5 slightly less regular when compared with the paths of the droplet streams of Fig
3 and 4, causing corresponding loss in resolution on the recording material.
Referring to Fig 6 there is shown schematically an apparatus for marking a recording surface 6, said apparatus making use of the present invention. Droplet supply 8 is a row of shaft electrodes positioned in marking material containers and electrically connected to external electrode 4 substantially in accordance, for example9 with the embodiments of Figs 3 or 4. Electrical potential sufficient to cause a stream of droplets to move in a desirably straight path from each of the shaft electrodes in the droplet source 8 toward the external electrode 4 is supplied by electrical input generator 9. Electrical input generators such as computers and facsimile apparatus are well known in the art, and any suitable such device may be used.
As the recording surface 6 moves past the drop-let source 8 the electrical input apparatus 9 syncrynously provides a potential between selected shaf~ electrodes and ~050097 the external electrode so that droplets are moved to mark the recording surface and meaningful information produced thereon.
Referring more specifically to Fig 7, there is shown schematically yet another method of marking a recording surface 6 using the method of the present invention. A
shaft electrode 3 is positioned in a supply of marking liquid 2 and a charge sufficient to cause a stream of droplets 5 to move from the shaft electrode 3 toward the recording surface 6 is established between the shaft electrode and an external electrode which, by way of example in this illustration is the marking liquid container 1.
In the embodiment of Fig 7 a pair of directional electrodes 11 are placed on either side of the path of the s~ream of droplets 5. The directional electrodes 11 are driven by an electrical input means 10, which may be, for example, a computer or a facsimile device. Such devices are well known in the art and any suitable such device may be used. The field applied by the directional electrodes 11 is such that it may change the direction of the stream of droplets 5 sufficient to effect writing on the recording surface 6.
The field established by the directional electrodes ~050097 11 is believed to be effective to change the direction of movement of the stream of droplets 5 because of the charge which is observed to be resident on each droplet as it moves away from the shaft electrode. It will be apparent to those skilled in the art that the amount of such charge is dependant upon factors such as the con-ductivity of the marking liquid, the amount of potential applied between the electrodes and the profile of the protruding end of the shaft electrode. In a typical example a marking liquid having a conductivity of about ohm cm which is propelled from a shaft electrode having a rounded protruding end with a diameter of about 0.003 inch by a potential of about 20,000 v/cm will have a charge of about 10 coulombs.
While particular embodiments of the invention have been described above, it will be appreciated that various modifications may be made by one skilled in the art without departing from the scope of the invention as defined in the appended claims.
Referring to Fig 6 there is shown schematically an apparatus for marking a recording surface 6, said apparatus making use of the present invention. Droplet supply 8 is a row of shaft electrodes positioned in marking material containers and electrically connected to external electrode 4 substantially in accordance, for example9 with the embodiments of Figs 3 or 4. Electrical potential sufficient to cause a stream of droplets to move in a desirably straight path from each of the shaft electrodes in the droplet source 8 toward the external electrode 4 is supplied by electrical input generator 9. Electrical input generators such as computers and facsimile apparatus are well known in the art, and any suitable such device may be used.
As the recording surface 6 moves past the drop-let source 8 the electrical input apparatus 9 syncrynously provides a potential between selected shaf~ electrodes and ~050097 the external electrode so that droplets are moved to mark the recording surface and meaningful information produced thereon.
Referring more specifically to Fig 7, there is shown schematically yet another method of marking a recording surface 6 using the method of the present invention. A
shaft electrode 3 is positioned in a supply of marking liquid 2 and a charge sufficient to cause a stream of droplets 5 to move from the shaft electrode 3 toward the recording surface 6 is established between the shaft electrode and an external electrode which, by way of example in this illustration is the marking liquid container 1.
In the embodiment of Fig 7 a pair of directional electrodes 11 are placed on either side of the path of the s~ream of droplets 5. The directional electrodes 11 are driven by an electrical input means 10, which may be, for example, a computer or a facsimile device. Such devices are well known in the art and any suitable such device may be used. The field applied by the directional electrodes 11 is such that it may change the direction of the stream of droplets 5 sufficient to effect writing on the recording surface 6.
The field established by the directional electrodes ~050097 11 is believed to be effective to change the direction of movement of the stream of droplets 5 because of the charge which is observed to be resident on each droplet as it moves away from the shaft electrode. It will be apparent to those skilled in the art that the amount of such charge is dependant upon factors such as the con-ductivity of the marking liquid, the amount of potential applied between the electrodes and the profile of the protruding end of the shaft electrode. In a typical example a marking liquid having a conductivity of about ohm cm which is propelled from a shaft electrode having a rounded protruding end with a diameter of about 0.003 inch by a potential of about 20,000 v/cm will have a charge of about 10 coulombs.
While particular embodiments of the invention have been described above, it will be appreciated that various modifications may be made by one skilled in the art without departing from the scope of the invention as defined in the appended claims.
Claims (33)
1. A method fox propelling droplets for marking liquid onto a recording surface which comprises:
(a) providing supply of marking liquid;
(b) positioning a shaft electrode so that a propellent end thereof extends to a position just above the operative surface level of the marking liquid supply; and (c) establishing a field between the shaft electrode and at least one external electrode sufficient to cause droplets to be propelled from the marking liquid source covering the shaft electrode onto a record receiving means.
(a) providing supply of marking liquid;
(b) positioning a shaft electrode so that a propellent end thereof extends to a position just above the operative surface level of the marking liquid supply; and (c) establishing a field between the shaft electrode and at least one external electrode sufficient to cause droplets to be propelled from the marking liquid source covering the shaft electrode onto a record receiving means.
2. The method of Claim 1, wherein the marking liquid has a viscosity of less than about 50 cps.
3. The method of Claim 2, wherein the marking liquid has a viscosity of less than about 30 cps.
4. The method of Claim 1, wherein the marking liquid has a resistivity of about 109 ohm cm.
5. The method of Claim 1, wherein the marking liquid has a dielectric constant of from about 2 to about 3.
6. The method of Claim 1, wherein the shaft electrode is positioned so that its propellent end extends at least about 0.020 inch above the surfaces of the marking liquid supply.
7. The method of Claim 1, wherein the shaft electrode has a flat propellent end.
8. The method of Claim 1, wherein the shaft elec-trode has a rounded propellent end.
9. The method of Claim 1, wherein the propellent end of the shaft electrode is coated with an insulating material.
10. The method of Claim 1, wherein the shaft elec-trode has diameter of at least about 0.005 inch.
11. The method of Claim 1, wherein the marking liquid rises to cover the propellent end of the shaft electrode by surface tension.
12. The method of Claim 1, wherein the marking liquid rises to cover the propellent end of the shaft electrode responsive to an electrical potential placed on the electrode.
13. The method of Claim 1, wherein the external electrode is a plate electrode positioned in the desired direction of travel of the droplets.
14. The method of Claim 1, wherein the external electrode is the liquid container.
15. The method of Claim 1, wherein the liquid container and a conductive means in the desired path of the droplets are both external electrodes.
16. The method of Claim 1, wherein the droplets are deflected by an electrical field.
17. The method of Claim 1, wherein the droplets mark a recording surface responsive to electrical input.
18. The method of Claim 1, wherein the field established between the shaft electrode and the second electrode is less than about 30,000 v/cm.
19. An apparatus for marking a recording surface responsive to electrical input which comprises:
(a) a container for holding a supply of marking liquid;
(b) a shaft electrode positioned in the supply of marking liquid so that a propellent end thereof protrudes to a position just above the operative surface level of the marking liquid;
(c) a second electrode positioned so that a field may be created between it and said shaft electrode sufficient to cause a stream of droplets to emanate therefrom whenever a sufficient field is established between the electrodes; and (d) a means for creating such a field between said electrodes.
(a) a container for holding a supply of marking liquid;
(b) a shaft electrode positioned in the supply of marking liquid so that a propellent end thereof protrudes to a position just above the operative surface level of the marking liquid;
(c) a second electrode positioned so that a field may be created between it and said shaft electrode sufficient to cause a stream of droplets to emanate therefrom whenever a sufficient field is established between the electrodes; and (d) a means for creating such a field between said electrodes.
20. The apparatus of Claim 19, wherein the marking liquid has a viscosity of less than about 50 cps.
21. The apparatus of Claim 20, wherein the marking liquid has a viscosity of less than about 30 cps.
22. The apparatus of Claim 19, wherein the marking liquid has a resistivity of about 109 ohm cm.
23. The apparatus of Claim 19, wherein the marking liquid has a dielectric constant of from about 2 to about 3.
24. The apparatus of Claim 19, wherein the propellent end of the shaft electrode is positioned to extend at least about 0.020 inch above the surface of the marking liquid supply.
25. The apparatus of Claim 19, wherein the shaft electrode has a flat propellent end.
26. The apparatus of Claim 19, wherein the shaft electrode has a rounded propellent end.
27. The apparatus of Claim 19, wherein the propellent end of the shaft electrode is covered with an insulating material.
28. The apparatus of Claim 19, wherein the shaft electrode has a diameter of at least about 0.005 inch.
29. The apparatus of Claim 19, wherein the second electrode is a plate electrode positioned in the desired direction of travel of the droplets.
30. The apparatus of Claim 19, wherein the external electrode is the marking liquid container.
31. The apparatus of Claim 19, wherein the liquid container and a conductive means in the desired path of the droplets are both external electrodes.
32. The apparatus of Claim 19, which includes a means for deflecting the droplets responsive to electrical input.
33. The apparatus of Claim 19, wherein the means for creating the field between the said electrodes is capable of providing a field having a strength of less than about 30,000 v/cm.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB4665274A GB1484368A (en) | 1974-10-29 | 1974-10-29 | Marking method and apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1050097A true CA1050097A (en) | 1979-03-06 |
Family
ID=10442077
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA237,306A Expired CA1050097A (en) | 1974-10-29 | 1975-10-07 | Marking method and apparatus |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1050097A (en) |
| GB (1) | GB1484368A (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4263601A (en) * | 1977-10-01 | 1981-04-21 | Canon Kabushiki Kaisha | Image forming process |
| IT1116334B (en) * | 1977-12-28 | 1986-02-10 | Olivetti & Co Spa | IMPACT-FREE WRITING DEVICE WITH SELECTIVE EMISSION OF SOLID INK PARTICLES |
| US4258371A (en) * | 1978-11-20 | 1981-03-24 | Matsushita Electric Industrial Co., Ltd. | Image recording apparatus |
| JPS55154169A (en) | 1979-05-18 | 1980-12-01 | Ricoh Co Ltd | Ink-jet printer |
| US4396925A (en) * | 1980-09-18 | 1983-08-02 | Matsushita Electric Industrial Co., Ltd. | Electroosmotic ink printer |
| CH649040A5 (en) * | 1982-10-08 | 1985-04-30 | Battelle Memorial Institute | DEVICE FOR PROJECTING DROPLETS OF AN ELECTRICALLY CONDUCTIVE LIQUID. |
| JPS59229345A (en) * | 1983-05-24 | 1984-12-22 | Fuji Xerox Co Ltd | Image recording apparatus |
| JPS61235157A (en) * | 1985-04-12 | 1986-10-20 | Tokyo Electric Co Ltd | Electrostatic printing |
| JPS6283151A (en) * | 1985-10-08 | 1987-04-16 | Tokyo Electric Co Ltd | Printer |
| JPS62225358A (en) * | 1986-03-27 | 1987-10-03 | Fuji Xerox Co Ltd | Image-recording head |
| JPS62225356A (en) * | 1986-03-27 | 1987-10-03 | Fuji Xerox Co Ltd | Image-recording head |
-
1974
- 1974-10-29 GB GB4665274A patent/GB1484368A/en not_active Expired
-
1975
- 1975-10-07 CA CA237,306A patent/CA1050097A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB1484368A (en) | 1977-09-01 |
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