US3656592A

US3656592A - Adjustable dash pot and actuating means therefor

Info

Publication number: US3656592A
Application number: US80114A
Authority: US
Inventors: William Fredrick Keller; Frank Francis Domyan
Original assignee: Deutsche ITT Industries GmbH
Current assignee: TDK Micronas GmbH; ITT Inc
Priority date: 1969-09-08
Filing date: 1970-10-12
Publication date: 1972-04-18
Anticipated expiration: 1989-04-18

Abstract

An hydraulic system having calibration, bandwidth, and dash pot controls with indicators for each, and a dash pot adjustment. The dash pot includes a corrugated bellows closed at one end and open at the other end to receive a conduit means. The conduit means connects the bellows to a fluid tight chamber and has an adjustable valve means therein to regulate fluid flow therethrough. Arm means is provided to compress the bellows.

Description

nited States Patent lfieller et al.

[54] ADJUSTABLE DASH POT AND ACTUATING MEANS THEREFOR [72] Inventors: William Fredrick Keller, Covina; Frank Francis Domyan, North Hollywood, both of Calif.

[73] Assignee: International Telephone and Telegraph Corporation, New York, NY.

[22] Filed: Oct. 12, 1970 [21] Appl. No.: 80,114

Related US. Application Data [62] Division of Ser. No. 855,937, Sept. 8, 1969, Pat. No.

[52] US. Cl ..188/270, 188/298 [51] Int. Cl ..F16f 9/04 [5 8] Field of Search ..188/270, 298

[56] References Cited UNITED STATES PATENTS 3,171,330 3/1965 McCombs, Jr ..91/388 X 3,393,607 7/1968 Peczowski et al ..91/388 X 2,029,136 1/1936 Stevens ..188/298 2,629,793 2/1953 Ponstingl ....l88/298 X 3,425,679 2/1969 Risso ..188/298 X FOREIGN PATENTS OR APPLICATIONS 513,332 8/1952 Belgium ..188/298 1,075,522 4/1954 France ..188/98 Primary Examiner-George E. A. Halvosa Att0rneyC. Cornell Remsen, Jr., Walter J. Baum, Paul W. Hemminger, Thomas E. Kristofferson and Charles L. Johnson, Jr.

[57] ABSTRACT An hydraulic system having calibration, bandwidth, and dash pot controls with indicators for each, and a dash pot adjustment. The dash pot includes a corrugated bellows closed at one end and open at the other end to receive a conduit means. The conduit means connects the bellows to a fluid tight chamber and has an adjustable valve means therein to regulate fluid flow therethrough. Arm means is provided to compress the bellows.

1 Claims, 2 Drawing Figures PATENTEnAP-R 18 I972 I 3,655,592

Inventor M F'- KELLER F- F- DOM YA N y 7 9" A ltorney ADJUSTABLE DASH POT AND ACTUATING MEANS THEREFOR This application is a division of co-pending application Ser. No. 855,937 filed Sept. 8, 1969, now U.S. Pat. No. 3,620,185, and having the same title. The benefit of the filing date of said co-pending application is hereby claimed for this application.

BACKGROUND OF THE INVENTION no bandwidth indicators have been provided with a correction which is a function of stroke length.

It is also old in the art to provide negative feedback to a valve positioner and to adjust the feedback rate. However, such devices are complicated and have no visual indication of feedback rate.

SUMMARY or THE INVENTION In accordance with the devices of the present invention, the above-described and other disadvantages of the prior art are overcome by providing a movable suspension system for the feedback spring. The set point may, thus, be adjusted accurately.

In accordance with a feature of the invention, a visual indication of the set point adjustment is provided.

According to another feature of the invention, a bandwidth adjustment is provided including a lead screw and a nut therefor to operate a feedback lever.

Still another feature of the invention includes a bandwidth indicator scale having a lined connecting plate extending from the nut to the scale. The plate may, thus, be adjusted to make the scale read accurately for a particular length of stroke.

A further feature of the invention resides in the use of, for example, a pneumatic bellows or feedback. The output of the bellows operates a diaphragm. The diaphragm chamber is vented through a needle valve which carries a scale to indicate the reset adjustments.

The above-described and other advantages of the invention will be better understood from the following description when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, which are to be regarded as merely illustratrve:

FIG. I is a vertical sectional view of a hydraulic control hydraulic constructed in accordance with the present invention; and

FIG. 2 is a top plan view of a needle valve assembly shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, a valve positioner is indicated at 10. The valve to be positioned is indicated at 11 in a housing 12. Housing 12includes a valve seat 13. Valve 11 is fixed to a piston rod 14. A piston 15 is fixed to rod 14. Cylinder l6 surrounds piston 15. Piston 15 has a groove 17 in which an O-ring 18 is positioned. O-ring 18 seals the space between piston 15 and cylinder 16. Piston 15 is moved upwardly by fluid pressure supplied by a pump 19 which is operated by an electric motor 20. The pressure below piston 15 is determined by a hydraulic amplifier 21 which receives an input from pump 19 through a conduit 22. The lower end of cylinder 16 is supplied with fluid under pressure by pump 19 through a conduit 23. Amplifier 21 has outlet conduit 24 with an orifice 25. Hydraulic fluid is bled from ori- 26 is fixed to a beam 27. When amplifier 21 causes the pressure in conduit 23 to drop by bleeding sufficient hydraulic fluid through orifice 25, a spring 28 closes valve 11.

A body 29 encloses rod 14 and a follower 30 for spring 28, follower 30 being fixed to rod 14. Housing 29 is joined to an intermediate body portion 31 of positioner 10 at 32 and 33.

Positioner 10 has a body portion or end cover 34 and a body portion of side cover 35.

A divider and beam support 36 extends across body 31 near the upper end thereof. All of the structures shown in FIG. 1 below divider 36 may be entirely conventional. These devices may also operate in a conventional way, for example, as shown and described in U.S. Pat. No. 3,087,471. Thus valve 11 in this application corresponds to valve 10 in FIG. 5 in the patent. Conduit 23 in this application corresponds to conduit 17 in the patent. Piston 15 is the same in both. In the patent, a pump is indicated at 25, and an hydraulic amplifier is indicated between

conduits

20 and 63.

In this application, in end cap 34, a control mechanism 37 is shown including an arm 38 pivoted on a shaft 39 by a ball bearing 40 carried thereby to rest on the upper end of piston rod 14. Arm 38 has a lead screw 41 threaded therethrough. Lead screw 41 may be turned to move a nut 42. Nut 42 has a projection 43 on which another arm 44 rests. Arm 44 is rotatable about a fixed shaft 45. An index marker 46 is also fixed to nut 42. A spring 47 is fixed to the left end of beam 27. The upper end of spring 47 is supported by a flexible strand 48. Strand 48 is movable over a pulley 49 with a nut 50. Nut 50 is moved by turning a lead screw 51 carried by arm 44. Lead screw 51 is threaded through an index marker 52.

Beam 27 is supported by flexure strips 53 and 54. A coil 55 is fixed to the right end of beam 27. The entire construction of the positioner 10 is made of non-magnetic materials with the exception of a body 56. Body 56 is made of a magnetic material A bellows 57 is located between arm 44 and movable relative thereto and a fixed projection 58. Bellows 57 has an output conduit 59 which extends into a chamber 60. Chamber 60 is enclosed with a diaphragm 61. Diaphragm 61 is connected to beam 27 by a fixed member 62. Chamber 60 has an outlet conduit 63 in which a needle valve 64 is disposed.

In the operation of positioner 10 shown in FIG. 1, the input is supplied electrically on leads 65 and 66 connected to coil 55. Piston 15 will then assume a position in accordance with the signal applied to

leads

65 and 66. Should there be any variation in the system so that piston 15 assumes a position error, this will be reflected in a change in the position of beam 27. This is true because the position of piston 15 and, therefore, piston rod 14 will cause arm 38 to move up or down by engagement of ball 40 with the upper end of rod 14. This, in turn, will cause arm 44 to move because arm 44 rests on pro- 55 jection 43 of nut 42. Movement of arm 44 will then cause the fice 25 at a rate determined by the position of vane 26. Vane spring 47 to supply more or less force to the left end of beam 27. The force supplied by spring 57 is, thus, balanced against the force supplied by coil 55 in its attraction of body 56. Note will be taken that when beam 27 tilts in a counterclockwise direction, orifice 25 is closed by vane 26; and the pressure in conduit 23 is increased. Tilting of beam 27 in a clockwise direction produces the opposite effect.

In accordance with the present invention, downward movement of arm 44 from the position shown causes bellows 57 to collapse. Downward movement of arm 44 is, therefore, retarded because air is not allowed to escape from bellows 57 except at a lower rate controlled by needle valve 64. Still further, negative feedback is provided in that the increased pressure in chamber 60 causes a counterclockwise movement on beam 27 through member 62.

It is a feature of the invention that bellows 57 is provided with chamber 60 for the negative feedback to provide damping. It is also a feature of the invention that needle valve 64 is provided to provide for the damping, yet insures final accurate correction.

Another feature of the invention resides in the use of indicia 64' and an index marker 64 relative to needle valve 64 to indicate the reset action adjustment of needle valve 64.

An adjustment card 67 is fixed to arm 38 by a screw 68. Card 67 has a slot 69 therethrough. Screw 68 extends through slot 69. The position of card 67 may be adjusted along the length of arm 38 by loosening screw 68 and moving card 67 beneath screw 68. An index marker is provided on card 67 at 70. Arm 38 has an indicia 71 thereon positioned so that index marker 70 may be located relative thereto in a position cor responding to the stroke of valve 11 desired for a particular input signal on leads 65 and 66. In this position, by comparing marker 46 with indicia at 72 and 73, the percentage of proportional bandwidth may be read from indicia 73 on card 74 fixed to arm 38. The proportional bandwidth relates the range of input signal on leads 65 and 66 to the range thereon at a particular stroke setting.

Arm 44 has card 75 fixed thereto with indicia 76. Comparison of marker 52 with indicia 76 gives the set point of the positioner 10.

An airtight O-ring seal 34' keeps valve 64 and all the structures in end cap 34 dirt free.

From the foregoing, it will be appreciated that, by the use of lead screw 51, it is possible to adjust the set point accurately. Further, indicia 76 provide a visual indication of the set point adjustment. A bandwidth adjustment is also provided including lead screw 41. Percentage of bandwidth is indicated by indicia 73 for any given stroke setting of card 67. The arrangement of bellows 57 with diaphragm 61 provides for negative feedback. Damping is simultaneously provided by bleeding air from bellows 17 through needle valve 64. The reset action is visible through indicia 64'.

We claim:

1. A control system comprising: a fixed base; an arm; first means to pivot said arm on said base to move about a predetermined axis; a hollow, fluid tight, corrugated bellows having first and second ends, said first end being closed, said bellows second end being fixed relative to said base, said bellows second end having an opening therethrough; second means providing a fluid tight chamber having an inlet opening and an outlet opening, said second means being fixed relative to said base; a conduit providing a fluid tight connection between said bellows opening and said inlet opening; an adjustable needle type vent valve connected from said outlet opening; and a spring connected with said arm and with said base to bias said arm substantially directly against said bellows first end in a manner such that said arm and said bellows can move relative to each other, said bellows being generally cylindrical and having a length substantial in comparison to its diameter to allow for substantial fluid evacuation from inside thereof upon compression by said arm while permitting substantial uninhibited arm movement by contouring to the inclination of said arm.