Electronic CAM compensation of pressure change of servo controlled pumps

• US 5,971,714 A
• Filed: 05/27/1997
• Issued: 10/26/1999
• Est. Priority Date: 05/29/1996
• Status: Expired due to Term

• Current Assignee: Graco Incorporated
• Original Assignee: Graco Incorporated
• Inventors: Handzel, James J., Schaffer, Eric J., Werner, Neal A.
• Primary Examiner(s): Freay, Charles G.
• Assistant Examiner(s): Evora, Robert Z.
• Application Number:
  US08/863,115
• Time in Patent Office: 882 Days
• Field of Search: 417/44.1, 417/44.2, 417/53, 417/45, 417/15, 417/28, 417/41, 604/65, 364/152
• US Class Current: 417/44.2
• CPC Class Codes: F04B 11/0041 by piston speed control F04B11/0058 takes precedence
• CPC Class Codes: F04B 11/0058 with piston speed control
• CPC Class Codes: F04B 2203/00 Motor parameters
• CPC Class Codes: F04B 2203/0213 Pulses per unit of time (pulse motor)
• CPC Class Codes: F04B 49/065 and making use of computers
• CPC Class Codes: F04C 15/0049 Equalization of pressure pulses silencing for compressors F04C29/06

Abstract

The construction and operation of the control of this invention is designed to minimize pressure changes at pump changeover by sampling pump pressure characteristics for each pump cycle, calculating a compensating motion profile and applying the profile to the motor which drives the pump. This control can be used with any pump which has the following characteristics: positive displacement, repeating cycle characteristics, rotary motor drive and an output pressure cycle curve which never falls to zero.

Claims

1. In a multi-cylinder reciprocating pump having a rotary motor drive, the improvement comprising:

means for sampling the pressure curve for each pump cycle;

means for calculating a compensating pressure curve over substantially all of said cycle from said sampling means; and

control means for said motor for applying said compensating pressure curve to remove pressure spikes which occur during changeover.

2. The multi-cylinder pump of claim 1 further comprising means for calculating the phase lag of a control input and compensating for said lag.

3. The multi-cylinder pump of claim 1 further comprising means for determining the rotary position of said motor.

4. A method for controlling a multi-cylinder reciprocating pump having a rotary motor drive, the improvement comprising the steps of:

sampling the pressure curve for each pump cycle during all of said cycle;

calculating a compensating pressure curve for all of said cycle from said sampling means; and

controlling said motor by applying said compensating pressure curve to remove pressure spikes which occur during changeover.