# US 11,110,702 B2 · Controlling recirculating of nozzles > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,110,702 B2 - Document ID: US11110702B2 - Status: Granted - Kind: B2 - Application number: 16/857,403 - Filed: 2020-04-24 - Published: 2020-08-06 - Granted: 2021-09-07 - Earliest claimed: 2020-04-24 - Assignees: Hewlett-Packard Development Company, L.P. - Applicants: Hewlett-Packard Development Company, L.P. - Inventors: Eric Martin; Vincent C Korthuis - Web page: https://patentgrep.com/patent/US11110702B2 ## CPC - B41J 2/04541: {Specific driving circuit} - B41J 2/0458: {controlling heads based on heating elements forming bubbles} - B41J 2/04586: {controlling heads of a type not covered by groups B41J2/04575 - B41J2/04585, or of an undefined type} - B41J 2/18: Ink recirculation systems - B41J 2202/12: with ink circulating through the whole print head - B41J: TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS ## Abstract In some examples, a fluid ejection device includes a nozzle to dispense fluid, and a recirculation controller to control recirculating of the nozzle. The recirculation controller is to receive, from a fluid ejection controller, an indication corresponding to a start of a sampling time interval, determine, during the sampling time interval, whether a firing event corresponding to firing of the nozzle has occurred, and in response to determining that the firing event has not occurred, cause activation of a recirculation pump to recirculate fluid through a chamber of the nozzle. ## Claims ### Claim 1 A fluid ejection device die assembly comprising: a plurality of nozzles and corresponding firing chambers; a plurality of memory elements to enable tracking of nozzle firing events; and a recirculation controller to initiate performance of recirculation of the plurality of nozzles in response to local determinations of firing events of the plurality of nozzles based on values of the plurality of memory elements. ### Claim 2 (depends on 1) The die assembly of claim 1, wherein the local determinations are to be based on indications of sampling time and the tracking of nozzle firing events. ### Claim 3 (depends on 1) The die assembly of claim 1, wherein the local determinations are to be based on a determination of whether nozzle firing events occur during sampling time intervals. ### Claim 4 (depends on 3) The die assembly of claim 3, wherein the performance of recirculation of the plurality of nozzles is to be based on activation of recirculation pumps associated with the plurality of nozzles. ### Claim 5 (depends on 1) The die assembly of claim 1, wherein the local determinations of firing events are to be based on a counter comprising the plurality of memory elements loaded with signals indicative of the firing events. ### Claim 6 (depends on 5) The die assembly of claim 5, wherein the performance of recirculation is to be based on an elapsed time since firing of a nozzle of the plurality of nozzles based on the firing events as tracked using the counter and the plurality of memory elements. ### Claim 7 (depends on 1) The die assembly of claim 1, wherein the performance of recirculation is to be based on a recirculation enable indication that indicates a recirculation enable time interval and a determination that a nozzle firing event has not occurred. ### Claim 8 (depends on 7) The die assembly of claim 7, wherein the performance of recirculation to be performed during the recirculation enable time interval to correspond a portion of a sampling time interval. ### Claim 9 (depends on 1) The die assembly of claim 1, wherein the recirculation controller is to cause the performance of recirculation without reception of recirculation commands from a fluid ejection controller. ### Claim 10 A fluid ejection device comprising: nozzles and corresponding firing chambers; an electrical interface to enable communication of messages, via a communications link, with a fluid ejection controller; and a recirculation controller to: start a sampling time interval based on a first indication in a message received from the fluid ejection controller; determine whether a firing event corresponding to the nozzles has occurred; and perform recirculation of the nozzles in response to reception of a second indication from the fluid ejection controller and a determination that a firing event has not occurred. ### Claim 11 (depends on 10) The ejection device of claim 10, comprising a die having the nozzles and the corresponding firing chambers and further wherein the recirculation controller is on the die. ### Claim 12 (depends on 10) The ejection device of claim 10, wherein the first indication is an information element in a header of a first print packet that contains print data controlling firing of the nozzles, and the second indication is an information element in a header of a second print packet that contains print data controlling firing of the nozzles. ### Claim 13 A method of recirculating nozzle of a fluid ejection device die, the method comprising: determining locally, by a controller of the fluid ejection device die, that a nozzle of a plurality of nozzles has not fired within a sample period; and triggering, by the controller, recirculation of the nozzle in response to the determining. ### Claim 14 (depends on 13) The method of claim 13, wherein the determining is based on a value of a firing event tracking counter, the counter associated with the nozzle of the plurality of nozzles. ### Claim 15 (depends on 14) The method of claim 14, further comprising responsive to a firing event occurring for the nozzle, resetting the counter associated with the nozzle. ### Claim 16 (depends on 14) The method of claim 14, further comprising updating the value in the counter associated with the nozzle for a new sampling period in response to detecting that nozzle has not fired during the sample period. ### Claim 17 (depends on 16) The method of claim 16, further comprising receiving, by the controller, a first indication that starts the new sampling period. ### Claim 18 (depends on 17) The method of claim 17, further comprising receiving, by the controller, a second indication that a recirculation enable time period during which recirculation of the nozzles is allowed, wherein the recirculation of the nozzle is responsive to the recirculation enable indication and the value of the counter.