Accoustically soft ink jet nozzle assembly

Abstract

An acoustically soft ink jet nozzle assembly is produced from materials, such as for continuous jets. The nozzle is a tubular member formed from polyphenylene sulfide. The resulting assembly is acoustically soft so that undesirable fluid and mechanical resonances are (RYTON) which has a substantially attenuated constant response over a transducer range of 10-100 KHz.

Description

not nonconductive electrically, that characteristic is not a requirement for many applications fo the present invention.

Referring to FIG. 2, there is shown a preferred embodiment of the nozzle assembly employing the preferred materials of the present invention. A nozzle 50 formed of Ryton, Celcon or Delrin is coupled to a tail piece 52 preferably formed of the same materials. In turn, the tail piece is coupled to a fitting 54 for connection to an ink supply conduit. A jewel 56 is provided in the forward portion of the nozzle and captured therein by virtue of the dimensions of the nozzle recess as previously described. Concentrically mounted over the nozzle 50 is a piezoelectric transducer 58 adhesively bonded in place. The devices are electrically driven by means of a cable 61, the conductors contained therein being soldered to the outside of the transducers as indicated. The nozzle assembly is preferably potted and disposed within a nozzle head assembly or block 60. The completed assembly is small enough to permit spacing on the order of six separate print heads per inch. The nozzles made according to the teachings of the present invention have good, long term resistance to ink solvents, are relatively temperature insensitive, and can be driven an substantially uniform drive voltages over a wide range of operating frequencies. At the same time, because they are acoustically soft, the fluid does not "experience" a rigid confining wall and does not form standing waves which generate fluid resonance within the nozzle body. By eliminating fluid resonance, the antiresonances representing sharp increases in the acoustic impedance of the ink are also eliminated. Thus, droplet formation is accomplished across a broad frequency range by a substantially uniform driving voltage.

If desired, because of the electrical isolation of the ink within the nozzle body, an independently controlled potential may be applied to the ink permitting, for example, increased deflection by the techniques taught in U.S. Pat. No. 4,319,251. In addition, phasing of drop formation and drop charging is facilitated by permitting charging currents in the ink to be reliably detected.

While the invention has been described with reference to a preferred embodiment of a nozzle assembly having a single orifice through which ink is ejected, it is within the teachings of the present invention to provide a plurally of orifices in the nozzle assembly configured in an array. Either a separate chamber for each orifice or a common chamber for a plurality of orifices may be used dependent upon which droplet formation, technique is desirable in the particular ink jet device in which the nozzle is employed. There is ink confined to the chamber in either instance, and forming the wall or walls of the nozzle ink chamber of acoustically soft material in accordance with the teachings of the present invention assures that the disturbing energy coupled to the chamber is transmitted to the ink within the chamber without substantial amplification, attenuation or the creation of harmonic resonance of any frequency characterizing the disturbing energy.

The present invention is useful also in ink jet printers that employ a pulsed nozzle to form droplets. Zolton U.S. Pat. No. 3,683,212 discloses one example of that type of nozzle. The impulses of electrical energy used to drive such a nozzle commonly have a duration of 10 microseconds to 100 microseconds. A Fourier analysis of those energy pulses manifests that reliable droplet formation necessitates that the nozzle respond consistently to frequencies in the range of 10 KHz to 100 KHz. It is desirable that the nozzle chamber not support fluid resonances in that frequency range. A nozzle which has a fluid chamber with walls made of acoustically soft material as taught by the present invention will not support resonances in that region, and thus will have a substantially flat response to energy impulses characterized by frequencies that are within the operating frequency range. As a result, droplet formation is more nearly proportional to the characteristics of the energy pulse applied to the fluid to improve control and enhance the marking results. In addition, spurious oscillations in the impulse nozzle ink chamber that occur after a pulse has directed formation of a droplet are absorbed if the walls are made of acoustically soft material. Those spurious oscillations can distort the energy applied to the fluid when a succeeding command pulse is transmitted to the fluid. Clearly, an impulse or pulse driven nozzle can be operated more advantageously by following the teachings of the present invention.

While we have shown and described embodiments of the invention, it will be understood that this description and illustrations are offered merely by way of example, and that the invention is to be limited in scope only as to the appended claims.

Claims

1. A In a continuous jet printer of the type which produces a continuous stream of ink droplets which are projected toward a substrate and are selectively electrically charged and deflected to mark the substrate, the improvement comprising:

a. a transducer producing a disturbing energy at a frequency within the range of approximately 10 KHz to 100 KHz;

b. a nozzle suitable for use with a said transducer to form said continuous stream of ink droplets comprising: a tubular member for coupling the disturbing energy to the ink said member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents, said tubular member being formed from Ryton a material which is substantially impervious to said ink and which ink, is acoustically soft, whereby when a transducer is coupled to said tubular member the disturbing energy thereof is transmitted to the ink within the tubular member without substantial and has a substantially constant response to the disturbing energy over said frequency range to minimize amplification, attentuation or the creation of harmonic resonances of a frequency characterizing the disturbing energy.

2. The nozzle according to claim 1 wherein said tubular member is molded as a single piece from a material selected from the group comprising: Celcon, Delrin, Ryton. 3. The nozzle according to claim 1 wherein the nozzle has a substantially flat response to the driving voltage frequency generating the disturbing energy over the range of approximately

10 KHz to 100 KHz.4. A In a continuous jet printer of the type which produces a continuous stream of ink droplets which are projected toward a substrate and are selectively electrically charged and deflected to mark the substrate, the improvement comprising:

a nozzle assembly to form a continuous stream of ink droplets for an ink jet printer comprising:

a. transducer producing a disturbing energy at a frequency within the range of approximately 10 KHz to 100 KHz;

(a) b. a tubular member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents; for coupling said (b) a transducer coupled to said nozzle for transmission of a disturbing energy through said tubular member to cause the ink to the ink to form droplets, as it leaves the orifice;

(c) c. said tubular member being formed from Ryton a material which is substantially impervious to said ink and which ink, is acoustically soft,

whereby the disturbing energy is transmitted to the ink within the tubular member without substantial and has a substantially constant response to the disturbing energy over said frequency range to minimize amplification, attentuation or creation of harmonic

resonances of a frequency characterizing the disturbing energy. 5. The nozzle according to claim 4 wherein said transducer is mounted on said tubular member and coupled thereto by adhesive bonding with a bonding agent which is relatively stiff to insure efficient coupling of the

disturbing energy to the tubular member. 6. The nozzle according to claim

5 wherein said bonding agent is an anaerobic adhesive. 7. A nozzle suitable for use with a transducer to form ink droplets comprising:

a tubular member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents, said tubular member being formed from a material which is substantially impervious to said ink and which has a substantially flat response to a driving voltage frequency characterizing the disturbing energy at least over the frequency range of 20 KHz to 70 KHz,

whereby when the transducer is coupled to said tubular member the disturbing energy thereof is transmitted to the ink within the nozzle without substantially amplification, attentuation or creation of harmonic resonances of a frequency characterizing the disturbing energy.8. The nozzle according to claim 7 wherein said tubular member is molded as a single piece from a material selected from the group comprising: Celcon, Delrin, Ryton polymers9. The nozzle according to claim 7 wherein said tubular member is molded as a single piece from Ryton and the response to the transducer disturbing frequency is substantially flat over the frequency range of 10 KHz to 100 KHz.10. A nozzle assembly to form ink droplet for an ink jet comprising:

(a) a tubular member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents;

(b) a transducer responsive to a driving signal for generating disturbing energy coupled to said tubular member to cause the ink to form droplets as it leaves the orifice;

(c) said tubular member being formed from a material which is substantially impervious to said ink and which has a substantially flat response to the driving signal frequency at least over the frequency range of 20 KHz to 70 KHz,

whereby the distributing energy is transmitted to the ink within the tubular member without substantial amplification, attentuation or creation of harmonic resonances of one or more frequencies characterizing the disturbing energy.11. The nozzle according to claim 10 wherein said transducer is coupled to said tubular member by adhesive bonding with a bonding agent which is relatively stiff to insure efficient coupling of the disturbing energy to the tabular member.12. The nozzle according

to claim 10 wherein said bonding agent is an anaerobic adhesive.13. A nozzle suitable for use with a transducer to form ink droplets comprising:

a tubular member having an orifice at one end, the other end adapted for connection to a supply of ink containing solvents, said nozzle being formed from a material which is:

(a) resistant to said ink,

(b) acoustically soft, and

(c) has a substantially flat response to the driving signal frequency generating the disturbing energy at least over the range of 20 KHz to 70 KHz,

whereby when a transducer is coupled to said tubular member the disturbing energy thereof is transmitted to the ink within the tubular member without substantial amplification, attentuation or creation of harmonic resonances of the driving signal frequency.14. The nozzle according to claim 13 wherein said tubular member is molded as a single piece from Ryton and the response to the transducer driving signal is substantially flat over the frequency range of 10 KHz to 100 KHz.15. A nozzle suitable for use with a transducer to form ink droplets comprising:

a hollow chamber connected to a supply of ink containing solvents, adapted to confine a volume of said ink to be ejected through an orifice in a wall thereof, said chamber being formed from an acoustically soft material which is substantially resistant to said ink,

whereby when a transducer is coupled to said chamber the disturbing energy thereof is transmitted to the ink within the chamber without substantial amplification, attenuation or the creation of harmonic resonances of one

or more frequencies characterizing the disturbing energy.16. A method of forming ink droplets from a supply of ink comprising the steps of:

supplying the ink to a chamber, the walls of which are formed of acoustically soft material and which have at least one outlet therefrom through which ink may pass;

creating a disturbing energy characterized by one or more predetermined frequencies;

transmitting said energy to said ink through said acoustically soft chamber walls to form droplets as the ink passes out of the chamber;

whereby the disturbing energy is transmitted to the ink without substantially amplification, attenuation or the creation of harmonic resonances of said one or more frequencies characterizing said disturbing energy.