EP0157048A2
Expired / Lapsed
EP
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Position measuring apparatus
Assignee: HP Inc
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Filing: 1984-11-08
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Granted: —
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Expires: 2004-11-08
Abstract
Abstract A linear capacitive encoder is utilized for detecting and encoding the position of a movable member such as a print bar (5) in a dot matrix impact printer. An eight-phase signal is capacitively coupled to one plate of a linear capacitor (A5-A8) mounted on the movable print bar. When the print bar moves the phase of the coupled signal changes with respect to the phase of the signal on the other plate of the capacitor, producing an analog signal representing incremental movements of the print bar. The analog signal is amplified and filtered (41, 42) and then converted to a TTL signal representing the position of the print bar. Present position of the print bar is compared to previous positions of the print bar to derive signals representing the present direction of movement, direction change and incremental movements of .0254 mm. Built-in error or hysteresis is added to the direction and direction change signals to prevent false direction changes due to noise. The .0254 mm signal and the direction change signal input a microprocessor which generates print position command signals at a selected dot density based on data stored in an output table which takes into account print hammer flight time and compensates for the sinusoidal motion of the print bar. An absolute reference point is established by the processor at each direction change of the print bar motion.
Inventors
- 👤 Kenneth B. Wade
- 👤 Phillip R. Luque
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-26 11:15
CPC Classifications
B; B41; B41J; B41J19/00; B41J19/18; B41J19/20; B41J19/202; B41J19/205; B41J19/207
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
269 words
Apparatus for determining the position, with respect to a reference point, of a movable member characterized by: means (14,25,26) for producing a train of successive i polyphase pulses and a train of successive reference pulses; transmitter means (13) for transmitting said polyphase pulse train; receiver means (AI-A8) capacitively coupled to said transmitter means for producing a signal from a summation of successive coupled pulses of said polyphase pulse train, said signal embodying information indicative of the position of said movable member with respect to said reference point; detector means (42) coupled to said receiver means providing a TTL signal, derived from said signal, represent-5 ing the phase of said signal; first means (24) coupled to said detector means (42) for comparing said TTL signal with said reference pulse train to provide a first signal representing a first incremental position change of said movable member and a second signal representing a second incremental position change of said movable member; and second means (75) coupled to said first means for comparing said first incremental position with said second incremental position change and providing an output strobe ¡ representing an incremental position change of said movable member when said position changes are occurring in the direction of motion of said movable member and said first position change being one increment away from said second position change, and providing an output signal representing the direction of motion of said movable member, and providing a pulse representing a change of direction of the motion of said movable member whereby the position of said movable member with respect to said reference point may be determined.
Claim 2
Dependent Claim
269 words
Apparatus for determining the position, with respect to a reference point, of a movable member characterized by: means (14,25,26) for producing a train of successive i polyphase pulses and a train of successive reference pulses; transmitter means (13) for transmitting said polyphase pulse train; receiver means (AI-A8) capacitively coupled to said transmitter means for producing a signal from a summation of successive coupled pulses of said polyphase pulse train, said signal embodying information indicative of the position of said movable member with respect to said reference point; detector means (42) coupled to said receiver means providing a TTL signal, derived from said signal, represent-5 ing the phase of said signal; first means (24) coupled to said detector means (42) for comparing said TTL signal with said reference pulse train to provide a first signal representing a first incremental position change of said movable member and a second signal representing a second incremental position change of said movable member; and second means (75) coupled to said first means for comparing said first incremental position with said second incremental position change and providing an output strobe ¡ representing an incremental position change of said movable member when said position changes are occurring in the direction of motion of said movable member and said first position change being one increment away from said second position change, and providing an output signal representing the direction of motion of said movable member, and providing a pulse representing a change of direction of the motion of said movable member whereby the position of said movable member with respect to said reference point may be determined.
Claim 3
Dependent Claim
64 words
Apparatus according to Claim 1 characterized in that said transmitter means comprises a plurality (13) of electrically conducting transmitter plates, each of said transmitter plates comprising a plurality of conducting electrodes disposed in a plane; and said receiving means comprises a plurality of electrically conducting receiver plates (A5-A8) disposed in a plane, each receiver plate being capactively coupled to at least one transmitter plate.
Claim 4
Dependent Claim
50 words
Apparatus according to either one of Claims 1 and 2 characterized in that said polyphase pulse train comprises a plurality of pulses electrically separated in phase; and each transmitting plate of said plurality (13) of transmitter plates transmitting one pulse of said plurality of pulses of said polyphase pulse train.
Claim 5
Dependent Claim
68 words
Apparatus according to any one of the preceding claims characterized in that said transmitter means (13) is fixedly attached to said reference point; and said receiver means (A5-A8) is disposed on said movable member orientated with respect to said transmitter means whereby the plane of said receiver means is parallel to both the plane of said transmitter means and the axis of motion of said movable member (5).
Claim 6
Dependent Claim
56 words
Apparatus according to any one of the preceding claims characterized in that the means for producing said train of successive polyphase pulses and said train of successive reference pulses comprises: a crystal controlled oscillator (22); and a plurality of binary counters (25,26), coupled to said crystal controlled oscillator, providing a train of successive polyphase square waves.
Claim 7
Dependent Claim
55 words
Apparatus according to any one of the preceding claims charaterized in that said receiver means provides a stepped triangle wave from a summation of successive coupled pulses of said train of successive polyphase square waves, said stepped triangle wave embodying information indicative of the position of said movable member with respect to said reference point.
Claim 8
Dependent Claim
40 words
Apparatus according to any one of the preceding claims characterized in that said detector means comprises a phase locked loop (42) for providing a TTL signal derived from said stepped triangle wave representing the phase of said stepped triangle wave.
Claim 9
Dependent Claim
45 words
Apparatus according to any one of the preceding claims characterized in that said first means coupled to said detector means comprises a plurality of D-type flip-flops (24) and latching means; and said second means coupled to said first means comprises electronic data processing means (55).
Claim 10
Dependent Claim
121 words
An impact printer comprising: a movable print bar (5) supporting a plurality of print hammers for printing marks; drive means for positioning said print bar; and characterized by means (70) to provide a first set of signals representing incremental movements of said print bar and a second set of signals representing changes in the direction of motion of said print bar, and a signal representing the direction of the motion of said print bar; and programmed data processing means (75) responsive to said first set of signals and said second set of signals and coupled to said print bar to provide print position signals to actuate appropriate ones of said plurality of print hammers for printing predetermined marks at predetermined positions.
Claim 11
Dependent Claim
121 words
An impact printer comprising: a movable print bar (5) supporting a plurality of print hammers for printing marks; drive means for positioning said print bar; and characterized by means (70) to provide a first set of signals representing incremental movements of said print bar and a second set of signals representing changes in the direction of motion of said print bar, and a signal representing the direction of the motion of said print bar; and programmed data processing means (75) responsive to said first set of signals and said second set of signals and coupled to said print bar to provide print position signals to actuate appropriate ones of said plurality of print hammers for printing predetermined marks at predetermined positions.
Claim 12
Dependent Claim
18 words
An impact printer according to Claim 9 and characterized in that it is a dot matrix impact printer.
Claim 13
Dependent Claim
154 words
An impact printer according to either one of Claims 9 and 10 characterized in that said programmed data processing means includes: a program memory for storing executable program code and a plurality of output tables corresponding to selected print dot densities; counter means responsive to said first set of signals for counting said incremental movements of said print bar to provide print position signals in accordance with data stored in a selected output table of said plurality of output tables; and means responsive to said second set of signals whereby said print position signals are provided in accordance with data stored in said selected output table commencing at the beginning of said output table in response to each signal of said second set of signals, and for computing an error signal to be utilized to establish an absolute reference point for said print bar position at each signal of said second set of siganls.
Claim 14
Dependent Claim
23 words
An impact printer according to any one of Claims 9 to 11 characterized in that said programmed data processing means comprises a microprocessor.
References Cited (Backward Citations)
No citation records indexed.
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