Patent EP0215525A2 successfully refreshed from Google Patents.
EP0215525A2
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EP
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Liquid chromatograph
Assignee: Koninklijke Philips NV
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Filing: 1986-09-10
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Granted: —
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Expires: 2006-09-10
Abstract
Abstract The liquid chromatograph comprises a multiple piston pump (1) which is arranged so that the delivery strokes of two pistons overlap to such an extent that for all designed liquid delivery pressures and compressibilities no period exists when no piston is delivering liquid. Thus for all other than worst case conditions there are periods in each pump cycle when two pistons are delivering liquid. The start of these periods is detected by the pressure increase produced at the outlet of the pump and measured by a pressure transducer (5). The output of the pressure transducer is fed via path (14) to a motor drive circuit (10) which controls a motor (4) which drives the pump (1) via a shaft (3) so that the speed of advance of the pistons is halved until one of the pistons ceases delivery. Consequently a relatively pulse free liquid flow is produced by the pump with a relatively simple motor speed control sustem.
Inventors
- 👤 James Brian Wilson
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 01:30
CPC Classifications
G; G01; G01N; G01N30/00; G01N30/02; G01N30/26; G01N30/28; G01N30/32; G01N2030/326
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
173 words
A liquid chromatograph comprising a multiple piston reciprocating pump for delivering a liquid at a desired flow rate to a separating column, each piston being arranged, during its delivery stroke, to deliver liquid at the same rate as the others, wherein the pistons are arranged to have overlapping delivery strokes and are driven by a motor whose speed is controlled by a control arrangement characterised in that the control arrangement is arranged to produce a control signal a characteristic of which has a first constant value during a first period when m of the pistons is/are delivering liquid to the column so that the piston(s) advance at a first constant velocity and a second constant value during a second period when (m+1) pistons are delivering liquid to the column to cause the pistons to advance at a second constant velocity, the second constant velocity being m/(m+1) times the first constant velocity, where m is an integer and (m+1) is less than or equal to the total number of pistons provided in the pump.
Claim 2
Dependent Claim
173 words
A liquid chromatograph comprising a multiple piston reciprocating pump for delivering a liquid at a desired flow rate to a separating column, each piston being arranged, during its delivery stroke, to deliver liquid at the same rate as the others, wherein the pistons are arranged to have overlapping delivery strokes and are driven by a motor whose speed is controlled by a control arrangement characterised in that the control arrangement is arranged to produce a control signal a characteristic of which has a first constant value during a first period when m of the pistons is/are delivering liquid to the column so that the piston(s) advance at a first constant velocity and a second constant value during a second period when (m+1) pistons are delivering liquid to the column to cause the pistons to advance at a second constant velocity, the second constant velocity being m/(m+1) times the first constant velocity, where m is an integer and (m+1) is less than or equal to the total number of pistons provided in the pump.
Claim 3
Dependent Claim
18 words
A liquid chromatograph as claimed in Claim 1, characterised in that the pump is a dual piston pump.
Claim 4
Dependent Claim
45 words
A liquid chromatograph as claimed in Claim 1 or Claim 2, characterised in that the start of the second period is detected by monitoring the pressure of the liquid delivered by said pump, an increase in the pressure denoting the start of the second period.
Claim 5
Dependent Claim
24 words
A liquid chromatograph as claimed in any of Claims 1 to 3, characterised in that the motor drives the pistons through a cam arrangement.
Claim 6
Dependent Claim
32 words
A liquid chromatograph as claimed in Claim 4, in which the cam arrangement comprises a separate cam for each piston, the cams being mounted on or formed integrally with a common shaft.
Claim 7
Dependent Claim
35 words
A liquid chromatograph as claimed in Claim 4 or Claim 5, in which the cam(s) are profiled such that a constant angular velocity of the cam(s) produces a constant linear velocity of the delivering piston(s).
Claim 8
Dependent Claim
30 words
A liquid chromatograph as claimed in any of Claims 1 to 6, characterised in that the end of the second period is detected by monitoring the positions of said pistons.
Claim 9
Dependent Claim
32 words
A liquid chromatograph as claimed in Claim 7 when dependent on Claim 6, characterised in that the position of the pistons is monitored by means of an encoder mounted on the shaft.
Claim 10
Dependent Claim
60 words
A liquid chromatograph as claimed in any of Claims 1 to 8, characterised in that the pump is driven by an electrical stepping motor, that the characteristic of the control signal is its frequency, and that during the second period in which (m+1) pistons are delivering liquid the frequency of the pulses applied to the motor is divided by (m+1)/m.
References Cited (Backward Citations)
No citation records indexed.
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