Pull-ahead winch control system

• US 3,893,404 A
• Filed: 03/25/1974
• Issued: 07/08/1975
• Est. Priority Date: 03/25/1974
• Status: Expired due to Term

• Current Assignee: Continental Emsco Co. (LTV Corp.)
• Original Assignee: Donald R. Cooper, Edward J. Mangold, William R. Chandler
• Inventors: Cooper, Donald R., Mangold, Edward J., Chandler, William R.
• Primary Examiner(s): Spar, Robert J.
• Assistant Examiner(s): Noland, Kenneth
• Application Number:
  US05/454,506
• Time in Patent Office: 470 Days
• Field of Search: 254/172,150 114/144R,144B 318/6R 61/72R,72.1,72.3,72.4,72.5,72.6 37/62,63 115/7
• US Class Current: 440/34
• CPC Class Codes: B63B 35/03 Pipe-laying vessels laying pipes under water F16L1/12
• CPC Class Codes: B63H 15/00 Marine propulsion by use of vessel-mounted driving mechanisms co-operating with anchored chains or the like
• CPC Class Codes: E02F 5/104 for burying conduits or cables in trenches under water floating substructures per se E02F9/06
• CPC Class Codes: E02F 5/107 using blowing-effect devices, e.g. jets digging devices using a blowing effect per se E02F3/9206
• CPC Class Codes: F16L 1/16 on the bottom

Abstract

A control system is provided for a pull-ahead winch used on a barge which digs a trench on the floor of a body of water and lays pipe in the trench. The trenching device or jet sled is suspended from the barge and is supplied with air and water at considerable force which are used to displace the bottom soil to dig the trench. The jet sled is pulled along a desired path by means of a cable, usually of fixed length, extending from a winch on the barge, and forward movement is supplied by one or more pull-ahead winches which reel in on a forwardly extending cable at a desired rate to permit the trench to be of the desired depth. Sled cable tension is controlled to a desired value by sensing this tension and producing an electrical signal proportional thereto, modifying this signal in a signal-shaping circuit comprising a second order lead-lag filter and comparing the modified signal with a tension reference signal to produce an error signal. The error signal is further modified by a signal representative of velocity and direction of movement of the pullahead cable. This modified error signal is then amplified and supplied to an electrically controlled clutch which controls the drive to the pull-ahead winch.

Claims

1. For use on a vessel used to pull a device for underwater trenching wherein a cable is attached to said device and a winch is carried on said vessel and drivably attached to said cable:

a pull-ahead control for said vessel including a second cable and an anchor attached thereto, a second winch drivably attached to said second cable, a prime mover and drive means connected to said second winch, said drive means including an electrically actuated clutch;

means producing an electrical signal substantially responsive to the tension in said first named cable, signal shaping means modifying said teNsion signal in response to changes in tension rate and rate of change of tension rate, means producing a tension reference signal, means comparing said modified electrical tension signal with said tension reference signal to produce an error signal, means producing a cable velocity signal whose magnitude is proportional to velocity of said second cable and whose polarity indicates direction of movement of said cable with respect to said vessel, means summing said error signal with said cable velocity signal to produce a control signal and power amplifier means connecting said control signal to said electrically actuated clutch.

2. producing a second electrical signal representative of a desired tension,

3. A pull-ahead control for a vessel as set forth in claim 2 wherein the transfer function of said lead-lag filter is defined by

4. A pull-ahead control for a vessel as set forth in claim 2 wherein the transfer function of said lead-lag filter is defined by

5. For use with a barge in which a trenching jet sled is suspended from the barge and is pulled by means of a sled cable, and the barge is moved by means of an anchored forwardly directed cable and a pull-ahead winch which winds in on said forwardly directed cable to impart forward movement to said barge, said pull-ahead winch being driven by means of a suitable prime mover and an electrically controlled clutch connected between said prime mover and said pull-ahead winch, a method of controlling tension in said sled cable comprising the steps of 1. sensing the tension in said cable sled and producing a first electrical signal responsive to said tension, 2. producing a second electrical signal representative of a desired tension, 3. modifying said first electrical signal by means of a second order lead-lag filter, 4. comparing said modified first electrical signal with said second electrical signal to produce an error signal, 5. producing a third electrical signal representative of velocity and direction of movement of said forwardly directed cable, 6. further modifying said error signal by comparing said error signal with said third electrical signal, and 7. amplifying said modified error signal and connecting said amplified, modified error signal to said electrically controlled clutch.

6. further modifying said error signal by comparing said error signal with said third electrical signal, and

7. In a control system for a barge pulling a trenching device wherein a first cable is attached to said trenching device and to a winch on said barge, a pull-ahead winch on said barge, and a second forwardly-directed cable attached to an anchor and to said pull-ahead winch, said pull-ahead winch being driven by means of a prime mover and electrically controlled clutch means connected between said prime mover and said pull-ahead winch, a third cable on said barge attached to an anchor and extending astern of said barge:

means producing a first electrical signal proportional to the tension in said first cable, means producing a second electrical signal proportional to a desired value of said tension, means including a second order lead-lag filter for modifying said first electrical signal, summing means comparing said first and second signals and producing a tension error signal, means producing a third electrical signal reprEsentative of velocity and direction of movement of said second forwardly-directed cable, second summing means summing said third electrical signal with said tension error signal to provide a modified error signal, an amplifier for amplifying said modified error signal, and means connecting said amplified and modified error signal to said electrically controlled clutch means.

8. A control system for a barge as set forth in claim 7 wherein said first named winch is pivotally mounted on said barge such that tension in said first cable tends to produce a moment around said mounting pivot, a hydraulic load cell is located at the base of said winch such that it produces a hydraulic pressure varying with the magnitude of said moment, and means are provided for converting said hydraulic pressure to an electrical signal to produce said first electrical signal.

9. A control system for a barge as set forth in claim 7 wherein the transfer function of said lead-lag filter is defined by