US2834361A

US2834361A - Electro-pneumatic system with rateresponsive action

Info

Publication number: US2834361A
Application number: US493523A
Authority: US
Inventors: Paul F K Erbguth
Original assignee: Daystrom Inc
Current assignee: Daystrom Inc
Priority date: 1955-03-10
Filing date: 1955-03-10
Publication date: 1958-05-13
Anticipated expiration: 1975-05-13

Description

y 1958 P. F. K. ERBGUTH 2,834,361

ELECTRO-PNEUMATIC SYSTEM WITH RATE-RESPONSIVE ACTION Filed March 10, 1955 2 Sheets-Sheet 1 PAUL E K. ERBGUT/l INVENTOR.

A T NE) May 13, 1958' P. F. K. ERBGUTH 2,834,361

ELECTRO-PNEUMATIC SYSTEM WITH RATE-RESPONSIVE ACTION Filed March 10, 1955 2 Sheets-Sheet 2 h'./? SUPPLY J PAUL E K. ERBGUTH INVENTOR.

United States Patent Cfifice 2,834,361 Patented May 13, 1958 ELECTRO-PNEUMATIC SYSTEM WITH RATE- RESPONSIVE ACTION Paul F. K. Erbguth, Great Neck, N. Y., assignor, by mesne assignments, to Daystrom, Incorporated, Murray Hill, N. J., a corporation of New Jersey Application March 10, 1955, Serial No. 493,523

13 Claims. (Cl. 137-84) This invention relates to pneumatic systems responsive to changes in a variable condition to effect a corresponding indication, recording or control function and more particularly to a novel system of this class provided Wth rate-responsive means to decrease the time required to rebalance the system and at the same time increase system stability.

Apparatus of the class contemplated by this invention comprises means for sensing changes in a variable condition, such as, for example, an electrical indicating instrument having a pointer and responsive to electrical current, balance lever systems deflectable in response to changes in weight, humidity, etc., telemetering arrangements for selectively positioning and/or controlling a remotely-positioned member, etc. Such condition-sensing means are arranged to move a vane, or baffie, into and out of an air stream flowing between a pair of axiallyaligned, spaced nozzles. Movement of the vane in the air stream inhibits, more or less, the quantity of air passing to the receiving nozzle thereby resulting in a corresponding variation in the air pressure of a closed system that is connected to the receiving nozzle. Included in such system is an air relay responsive to the air pressure changes in the receiving nozzle and correspondingly varying the air pressure of a relatively higher pressure system to thereby effect a desired action such as, for example, a return of the vane to substantially its initial or throttling position in the air stream. Such action is accompanied, if desired, by a simultaneous indicating, recording or control function.

Systems of this type are described and claimed in my co-pending application, Serial No. 490,907, filed February 28, 1955, which application is primarily directed to a pneumatic system adapted for use with condition-sensing devices having low torque.

The present application is directed to a pneumatic system having derivative action or rate response, in order to increase the stability of the air follow-up system and to prevent cycling, which may otherwise be present.

An object of this invention is the provision of a pneumatic system responsive to the movement of a vane actuated by an element that is sensitive to changes in a variable condition and including rate responsive means for increasing the stability of the system.

An object of this invention is the provision of a pneumatic system comprising a pair of axially-aligned nozzles, means normally maintaining an air stream between the nozzles, a vane movable in the air stream by an element responsive to changes in the air pressure in one of the nozzles to effectuate a movement of the vane in a direction opposite to that brought about by the said element, said means including a pair of bellows pivotally carrying a beam, each of said bellows being connected to a common source of air pressure but having different rates of movement whereby a change in the air pressure source effects an initial tilting of the beam.

An object of this invention is the provision of a pneurnatic system comprising axially-aligned discharge and receiving nozzles, means connecting one of the nozzles to a source of constant, low pressure air whereby an air stream normally is maintained between the nozzles, an element movable in response to changes in a variable condition, a vane actuated by said element and movable in the air stream to inhibit more or less the flow of air to the other nozzle, an air relay responsive to air pressure changes in the said other nozzle, and correspondingly varying the air pressure of a higher pressure source, a pair of bellows connected for operation by the pressure variations of said higher pressure source, the connection to one of the bellows including an air restricter, a beam pivotally supported by both said bellows, and means coupling the said beam to the said vane.

An object of this invention is to provide a bellows arrangement for use in a pneumatic system and comprising a pair of bellows, each acting on different portions of a controlling lever and, while connected to the same air supply, one of the bellows has a line thereto restricted so that upon a slow change in air pressure, the control lever remains substantially parallel to its initial position during movement, but when a sudden change in air pressure takes place, the lever initially is tilted by reason of the faster movement of unrestricted bellows.

An object of this invention is the provision of a rateresponsive bellows arrangement for use in a balancing type of pneumatic system said arrangement comprising a pair of similar bellows connected to the same source of air pressure, a restriction in the air line leading to one of the bellows, a pair of supporting brackets individually secured to the movable ends of the bellows, knife-edge fulcrum elements carried by the brackets, a lever supported by the fulcrum elements and spring means biasing the lever toward the fulcrum elements.

These and other objects and advantages of the invention will become apparent from the following specification when taken with the accompanying drawings. It will be understood the drawings are for purposes of illustration and are not to be construed as defining the scope or limits of the invention, reference being had for the latter purpose to the claims appended hereto.

In the drawings, wherein like reference characters denote like parts in the several views:

Figure 1 is a diagrammatic view of a pneumatic system embodying my invention;

Figure 2 is a view corresponding to Figure 1, but showing a practical form of the invention;

Figure 3 is a perspective view of a portion of the mechanism shown in Figure 2; and

Figure 4 is a fragmentary, transverse sectional view on the line IViV of Figure 2, in the direction of the arrows.

In the instrument illustrated in Figure 1, which includes a force balance system involving mechanism for sensing changes in a variable condition, there is shown a vane 21 carried by a lever 22 which, in this instance, is the pointerof a sensitive electrical instrument, such as a millivoltmeter. The sensitive eiectrical instrument is designated generally by the numeral 23 but only the wire wound coil 24, rotatably mounted on pivots 25 and 2-6, is illustrated. The coil is provided with a pair of

spiral hair spring

27 and 28, for conducting current to the coil and resiliently causing the coil 24- to stay in a given position with respect to the poles of an associated permanent magnet (not shown), until electric current is passed therethrough, as is well known in this art. The coil position is also controlled by a third spiral hair spring 29 for purposes which will be explained hereinbelow. The current to the coil may, for example, be generated by a thermocouple 31 serving as a temperature-measuring de vice in a furnace (not shown).

There is employed a pair of axially-aligned

nozzles

32 and 33 positioned so that the vane 21 is initially or normally disposed therebetween, The discharge nozzle 32 is connected to a source of fluid under pressure, such as a compressed air supply, through the tube 34. The tube 34 has a flow restrictor 35 therein to cause'the air to flow from the nozzle 32 at a low pressure, say at a pressure of aboutl of water and no more than 3" of water. The aligned receiving nozzle 33 is connected to an air relay 36 by tube 37.

When the vane 21 is displaced, say, to move further into the air stream, a decreased amount of air flows across the gap to the nozzle 33, and through the tube 37 to the chamber of an air relay 36. The resulting decrease in air pressure causes the air relay diaphragm 38 to move downwardly, thereby moving a connected member, such as a lever 39, pivoted to the relay 36 as indicated at 41, and carrying at its other end a flapper 42 normally disposed adjacent a nozzle 43 from which air normally flows. The nozzle 43 is connected to a source of air under pressure by the tube 44 containing a flow restrictor 45 therein. It is here pointed out, however, that the air pressure in the tube 44 may be considerably higher than that in the tube 34 connected to the discharge nozzle 32. A beam 51 is coupled to the bellows 46, 47 such that expansion or contraction of the bellows results in a corresponding lateral displacement of the beam. When the air pressure in the tube 37 decreases, due to the vane 21 cutting further into the air stream between the

nozzles

32, 33, the relay diaphragm 38 moves downwardly thereby moving the flapper 42 closer to the associated nozzle 43. There results a corresponding increase in the pressure of the air within the tubes 44 and 48 causing the bellows 46, 47 to expand and displace the beam 51 upwardly.

A drum 52 is mounted on a second shaft 54 axially aligned with the movable coil shaft 30 and rotatable within suitable bearings (not shown) that support the

shaft ends

55, 56. One end of a wire 53 is secured to the drum and wound therearound while the other end is secured to an end of the beam 51. A spiral spring 57 has one end secured to the shaft 54 and the other end to a fixed abutment 58, such spring providing a biasing force to maintain the wire 53 taut. The shaft 54has a rigid L-shaped connecting link 59 secured thereto, said link extending toward the movable coil and having secured thereto the outer end of the spiral spring 29 as at 61. The other end of the spring 29 is secured to the shaft 30. Movement of the beam 51 results in a corresponding rotation of the shaft 54 which acts upon the hair spring 29 to retain the vane 21 in a throttling position in the air stream and thereby maintain system balance. It will be apparent that the variation of the air pressure in the bellows 46, 47 is a measure of the force applied to the lever, or pointer, 22.

However, in the present instance, it will be seen that the restoration of system balance is accelerated by virtue of the differential action of the bellows 46, 47. Upon a change in air pressure in the tubes 44 and 48, the unrestricted bellows 46 will expand or contract at a faster rate than the bellows 47 having a restriction 49 in the supply line thereto. Thus, the initial displacement of the beam 51 is not parallel to its original at-rest position. More specifically, if the air pressure in the tube 48 increases the beam 51 will be tilted in a clockwise direction thereby resulting in an initial over-correction action. So too, if there is a decrease in the air pressure in the tube 48 in which case the beam initially will be tilted in a counter-clockwise direction. The beam, therefore, tilts one way or the other upon a change in the position of the vane between the

nozzles

32, 33 and the extent of such tilt depends upon the extent of the vane movement. Eventually, the restricted bellows 47 will expand or contract to an extent equal to that of the unrestricted bellows and the new position of the beam will be parallel to its original position. The response of the'system, therefore, is proportional to the rate of change of the air pressure in the receiving nozzle 33. The net result is an accelerated rebalancing action and improved system stability.

In order to prevent passage of the vane 21 completely through the air stream resulting in an improper operation of the system, a suitable stop S is provided.

Referring now to the embodiment of the invention illustrated in Figures 2, 3 and 4, there is shown an instrument employing preferred features shown only diagrammatically in the preceding embodiment. The mechanism for sensing changes in a variable condition is here an electrical measuring instrument, such as a millivoltmeter or a milliarnmeter, generally designated 23a. This instrument is more or less conventional, so the parts are not described fully. The part 62 is a soft-iron yoke within which rotates a pivoted coil 24a carrying a pointer 22a which moves over a scale 63 between suitable limiting stops 64 and 65.

The pointer 22a has a tail 66, extending away from the scale 63, and which engages a lever 67 movably mounted on a shaft 68 (see Figure 3) joumalled in

bearings

69 and 71, forming part of a supporting frame 72. As shown in Figure 3, the outer end of this shaft 68 has a knurled setting wheel 73, secured thereto by means of a screw 74. The setting wheel 73 carries a stop rod 76 for limiting turning of itself, as by engaging the frame 72. The shaft 68 corresponds with the shaft 30 of Figure 1, in that it is operated by an aligned shaft 77, corresponding with shaft 54 in Figure I. Said shaft 77 effects turning of the shaft 68 by means of a rigid shaft extension 78, the free end of which is connected tothe outer end of a spiral hair spring 79 carried by the shaft 77. In the present instance also, the lever 67 carries a vane 21a disposed between aligned nozzles 32a and 33a, rather than having the vane carried directly by the pointer 22a of the instrument.

The shaft 77 carries an arm 81 having an adjustable disc 82 movable by an end of the beam and corresponding with the wire 53 of the preceding embodiment, in that it effects turning of the shaft 77, which corresponds with the shaft 54. This beam 51a is carried by the bellows 46a and 47a, as by being pressed against the bottoms of

U-shaped arms

84 and 85 respectively pivoted to said bellows as indicated at 86 and 87, by individual springs 88. The beam maintains its position by having notches 89 in its lower side receiving corresponding projections, o'r knife edges, 91 on the

U-shaped members

84 and 85. The bellows are fixedly supported on the frame member 96 by the

bolts

92, 93 and the nuts 94, 95.

The operation of the apparatus illustrated in Figures 2, 3 and 4 is similar to that of the apparatus illustrated in Figure 1. Air is received from a main supply line 97 through a shut-off valve 98. Such air, normally at a conventional pressure of 20 pounds per square inch, passes to a manifold 99. Air from the manifold 99 is passed to another'manifold 103 through the

tubes

101 and 104 and its pressure is indicated by a gauge 102. The pressure of the air in the tube 44a, after passing through the flow restrictor 45a is indicated-by the low pressure air gauge 106. This air pressure normally is in the range of, say, 3-15 pounds per square inch and its actual magnitude depends upon the spacing between the flapper 42a and the nozzle 43a of the air relay 36a. It is this air pressure which controls the expansion and contraction of the parallel bellows 46a and 47a, it being noted that the bellows 46a is connected directly to the tube 48a whereas the bellows 47a is connected thereto through a flow restrictor 49a.

The discharge nozzle 32a is connected to the manifold 99 by the tube 34a containing a flow restrictor 3511 the arrangement being 'such that the pressure of the air within this tube is very low, in the range of not more than three inches of water. Under such conditions there is no appreciable reaction between the air stream flowing between the aligned nozzles 32a, 33a and'the thin vane 21a. This is an important factor when the system is designed for operation with condition-sensing means developing only a relatively low torque such as a sensitive electrical instrument.

The operation of the apparatus corresponds to that of Figure 1 in that the vane is movable in an air stream between axially aligned nozzles, although the vane is not directly attached to the pointer. Upon movement of the pointer clockwise over the scale 63, the pointer tail 66, which extends in a direction opposite to said scale, engages an angular extension 105 on the lever 67 and moves it correspondingly counter-clockwise, as viewed in Figures 2 and 3. This effects a corresponding movement of the vane 21a further out of the air stream between the aligned nozzles 32a and 33a, it being pointed out that the vane initially was partially in the air stream when the instrument pointer 22a was in its normal, mechanical zero position. When the vane is moved further out of the air stream, the air pressure in line 37a is increased, thereby causing an upward movement of the diaphragm 38a of relay 36a. The lever 39a, therefore, moves the flapper 42a further away from the nozzle 43a, thereby correspondingly decreasing the air pressure in the bellows 46a and 47a causing the beam 51a to effect a corresponding rotation of the lever 67 to move the pointer towards its initial position, wherein the forces of meter torque and the air system are in balance.

From the previous description it will also be seen that by virtue of the restrictor 49a, here shown as a coil in the line 48a to the bellows 47a, the beam 51a tilts under a change in pressure so as to effect an initial over-correction, follower by a restoration to the normal desired position as the pressures in the two bellows 46a and 47a equalize.

From the foregoing description, it will be seen that I have provided a pneumatic system responsive to changes in a variable condition at a rate depending upon the rate of change of the condition. Those skilled in this art will understand that the variation in the air pressure in the output line of the air relay corresponds to the extent of the change in the variable condition. Such air pressure variation maintains a balance with respect to the condition-sensing device and, therefore, can be utilized to return the condition to a preselected or normal value.

Having now described my invention in detail, in accordance with the requirements of the patent statutes, various changes and modifications will suggest themselves to those skilled in the art, and it is intended that such changes and modifications shall fall within the scope and spirit of the invention, as recited in the following claims.

I claim:

1. A pneumatic system comprising a discharge nozzle and an axially-aligned receiving nozzle, a vane movable between the nozzles, means maintaining a flow of air across the nozzles except as inhibited by the vane, rateresponsive air-operated means movable in response to variations in air pressure in the receiving nozzle, as the vane intercepts more or less of the air stream, and means coupling the air-operated means to the vane in a sense to restore the vane to a throttling position in the air stream.

2. The invention as recited in claim 1, wherein the said air-operated means comprises a pair of bellows, one of which includes a restriction in the air connection thereto, and the means coupling the bellows to the vane comprises a beam pivotally supported by the bellows.

3. The invention as recited in claim 2, wherein the bellows are disposed in vertical position with the upper surface of each secured in relatively fixed position, and the said beam is supported by the bellows by means of a pair of supports, each pivotally connected to the lower end of the bellows.

4. A pneumatic system comprising a sensing element movable according to changes in a variable condition, a vane movable by the sensing element, a discharge nozzle and an axially-aligned receiving nozzle disposed on opposite sides of the vane, means maintaining an air stream across the nozzles except as inhibited by the vane, an air relay having an actuating chamber closed by a diaphragm and connected to the receiving nozzle, means actuated by the diaphragm and varying the pressure in an air line, rateresponsive air-operated means movable in accordance with the variation of pressure in the said air line, and coupling means coupling the air-operated means to the vane in a sense to move the vane ina direction opposite to that brought about by the sensing element.

5. The invention as recited in claim 4, wherein the said air-operated means comprises a pair of bellows connected to the said air line, said bellows having different rates of motional response to a given change in air pressure in the line, and wherein the said coupling means includes a beam pivotally carried by both bellows.

6. The invention as recited in claim 5, wherein the said bellows are disposed in vertical position with the upper end of each secured in fixed position, and the said beam is carried by supports individually pivoted to the lower end of the bellows.

7. An electro-pneumatic system comprising an electrical instrument having a rotatable pointer, a discharge nozzle and an axially-aligned receiving nozzle, means normally maintaining an air stream flowing across the nozzles, a vane movable by the pointer to intercept more or less of the air stream, an air relay having a chamber closed by a diaphragm, a tube connecting the said chamber to the receiving nozzle, means actuated upon movement of the diaphragm to correspondingly vary the pressure in an air line, a first bellows directly connected to the air line, a second bellows connected to the air line through a flow restrictor, a beam pivotally movable in accordance with the movement of both bellows, and means coupling the beam to the vane in a sense to maintain the vane in a throttling position in the air stream.

8. The invention as recited in claim 7, wherein the said bellows are disposed in vertical, parallel position each having its upper end secured in relatively fixed position, and wherein the said beam is carried by brackets depending downwardly from the lower ends of the bellows.

9. The invention as recited in claim 8, wherein the said brackets are pivotally secured to the bellows, and the base portions of the brackets carry bearings disposed in transverse notches formed in the lower surface of the beam.

10. A bellows system for producing a motional response varying with the rate of change of air pressure applied thereto and comprising only a pair of bellows, means mounting said bellows side by side so that the corresponding end of each is fixed, an air line connection between one of the bellows and a source of variable air pressure, a second air line including a flow restrictor connected between the other bellows and the source of variable air pressure, a beam and means pivotally securing the beam to the movable end of each bellows.

11. A bellows system for producing a motional response varying with the rate of change of air pressure applied thereto and comprising a pair of bellows disposed in vertical position with the upper end of each secured in relatively fixed position, an air line connecting one of the bellows to a source of variable air pressure, a second air line including a flow restrictor and connecting the other bellows to the source of variable air pressure, a pair of brackets pivotally secured to the lower ends of the bellows, a beam supported by the brackets, and spring means disposed between the lower ends of the bellows and the beam and urging the beam toward the base portions of the brackets.

12. The invention as recited in claim 11, wherein the base portions of the brackets carry knife edges disposed within transverse slots in the lower surface of the beam.

13. An electro-pneumatic system comprising an electrical instrument having a rotatable pointer, a discharge nozzle and an axially-aligned receiving nozzle, means normally maintaining an air stream flowing from the discharge nozzle to the receiving nozzle, a lever on a shaft and movable 7 by said pointer during operation, a vane movable by the lever to. intercept more or less of the air stream, an air relay having a chamber closed by a diaphragm, a tube connecting said chamber to the receiving nozzle, means actuated upon movement of said diaphragm to correspondingly vary the pressure in an air line, a first bellows directly connected to the air line, a second bellows connected to the air line through a flow restrictor, a beam pivotally movable in accordance with the movement of both bellows, a second shaft coaxial with said lever shaft, resilient means positioning saidiever and having one end connected to the lever shaft and the other end attached to said second shaft, an arm extending from said second shaft, an adjustable disc carried by said arm, and means carried by said beam for engaging said disc so as to move the vane C3 in a sense to maintain it in a throttling position in the air stream.

References Cited in the file of this patent UNITED STATES PATENTS 2,330,654 Ziebolz Sept. 28, 1943 2,397,448 Todd Mar. 26, 1946 2,409,871 Krogh Oct. 22, 1946 2,441,044 Tate May 4, 1948 2,658,392 Vannah Nov. 10, 1953 FOREIGN PATENTS 689,814 France June 2, 1930 458,823 Great Britain Dec. 28, 1936 831,161 Germany Feb. 11, 1952