US3090395A

US3090395A - Pneumatic governor with star-shaped arrangement of bellows

Info

Publication number: US3090395A
Application number: US89046A
Authority: US
Inventors: Weiss Walter; Kowalski Hans; Koebelc Alfred
Original assignee: JC Eckardt AG
Current assignee: JC Eckardt AG
Priority date: 1960-11-25
Filing date: 1961-02-13
Publication date: 1963-05-21
Anticipated expiration: 1980-05-21

Description

y 21, 1963 w. WEISS ETAL 3,090,395

PNEUMATIC GOVERNOR WITH STAR-SHAPED ARRANGEMENT 0F BELLOWS Filed. Feb. 15, 1961 3 Sheets-Sheet 1 Fig. I

22 22 28' Fig. 2

INVENTORS ATTORNEYS May 21, 1963 Filed Feb. 15,. 1961 w. WEISS ET AL 3,090,395

PNEUMATIC GOVERNOR WITH STAR-SHAPED ARRANGEMENT OF BELLOWS 3 Sheets-Sheet 2 Fig.3

INVENTORS M g) I ATTORNEKS May 21, 1963 w. WEISS ET AL 3,090,395

PNEUMATIC GOVERNOR WITH STAR-SHAPED ARRANGEMENT OF BELLOWS Filed Feb. 13, 1961 5 Sheets-Sheet 3 INVENTORS WALTEE WEISS HAA/S K M/ALSK/ ALFEED KOEEELE ATTORNEYS United 3,090,395 PNEUMATIC GQVERNOR WITH STAR-$HAPED ARRANGEMENT T BELLOWS Walter Weiss, Backnang, Wurttemberg, Hans Kowalski, Rommelshausen, near Waiblingen, Wurttemberg, and Alfred Koebele, Ludwigshnrg, Wurtteniberg, Germany, assignors to J. C. Eckardt A.G., Stuttgart-Bad Cannstatt, Germany, a corporation of Germany Filed Feb. 13, 1961, Ser. No. 89,046 Claims priority, application Germany Nov. 25, 1960 9 Claims. (Cl. 137-86) The present invention relates to an automatic, pneumatically actuated governor which comprises resilient elements upon which pressures of a pressure medium are applied which represent the desired value and the actual value of the controlled variable, and which comprises further resilient elements which are acted upon by pressure media so that a feedback effect will be attained whereby the actual value will approach the desired value in accordance with a predetermined time factor. In governors of the known type, the comparison between the desired value and the actual value of the controlled variable is carried out by means of a spring-loaded balance in which the proportional range of the governor may be set by an adjustment of the transmission ratio of the balance. If the proportional effect should in such governors be adjustable within a large range, it is very difficult to design them so as to permit the transmission ratio to be adjustable within wide limits.

It is an object of the present invention to overcome these difiiculties by providing a resilient elements for comparing the desired value with the actual value and the further resilient elements for producing the feedback effect are disposed in a starshaped arrangement within a common plane in which the two resilient elements of each pair are disposed opposite to each other so that the axes of all of these elements intersect at a central point, and each of them rests at one end on a stationary support, while their other ends which are movable under pressure are connected to a ring which is also disposed within the same plane as the resilient elements and the peripheral surface of which serves as a flapper surface which is associated with a nozzle opposite thereto through which a compressed air current is passed so as to impinge upon the ring. This nozzle is pivotable about the center of the apparatus for varying the proportional range.

Under the effect of a difference between the pressures which are associated with the actual value and the desired value of the controlled variable, and also as the result of the reciprocal action of the pressures which produce the feedback effect, the ring which is secured to one end of each resilient element will be eccentrically displaced. Due to this eccentric displacement the pivotable nozzle will be disposed at different distances from the ring. These distances may be adjusted to different sizes by an adjustment of the nozzle to different points around the periphery of the ring. it is thus possible to adjust the proportional range of the governor within wide limits.

According to one preferred embodiment of the invention, the resilient elements may be mounted in a stationary position at the point of intersection of their axes, and their outer ends which are movable under pressure may be connected to the inner surface of a ring which lies within the common plane of the resilient elements and surrounds these elements, and the outer surface of which serves as a flapper surface. According to another embodiment of the invention, the resilient elements may, however, also be secured in a stationary position at their outer ends, while their inner ends which are movable under pressure \are connected to the outer surface of an governor in which the a Patented May 21, 1963 2 inner ring which also lies within the common plane of the resilient elements and the inner surface of which then serves as a flapper surface which is associated with the nozzle.

According to another feature of the invention it is of great advantage if the two resilient elements for producing the feedback effect are mounted in the apparatus so that their effective axes are slightly inclined or V-shaped relative to each other and in the direction toward the resilient element which is acted upon by the pressure which represents the actual value. Furthermore, it is advisable also to mount the resilient elements for the comparison of the actual and desired values so that their effective axes are slightly inclined to each other and in the direction toward one of the feedback elements, preferably the resilient element which is acted upon by a pressure which is applied to produce an integral effect. The effective surface area of the last-mentioned resilient element is preferably also made slightly larger than the corresponding area of the opposite resilient element which is acted upon by a pressure which is applied to produce a differential effect. The ring which is connected to the resilient elements and serves as a flapper surface may, if desired, he made of such geometrical dimensions and of such a material that it will be elastically deformed into an elliptical shape of a very small eccentricity when acted upon by a pressure from one side.

A governor according to the invention which may embody any one or several of the above-mentioned features in any suitable combination with each other has the advantage that the initial proportional band and a small residual deviation from the desired value will remain at least substantially constant within the entire adjustable proportional range. The more of these features which are combined in such a governor the better will be the constancy of the initial proportional band and of the small deviation from the desired value.

The initial proportional band has been defined in the art as that range of input values corresponding to the full operating range of output signal when the integralaction time is set at its minimum Value. The initial proportional band can be expressed as a percentage of the scale range. Initial proportional band is mainly determined by the forward-path gain of the controller, i.e. in pneumatic cont-rollers, the gain of the feedback path only, the initial proportional band is practically independent of the baffle-nozzle system and the pilot valve in cats cade. For accurate control, the offset due to the initial proportional hand must be small, e.g., not higher than 1%. For most types of controller, the initial proportional band is dependent on the proportional band setting, in which case it increases with increasing proportional hand. If suitable provisions are made that this initial proportional band will remain constant when the proportional range is changed, it will be insured that the sensitivity of the governor will be equally high at all adjustments of the P range.

The small residual deviation from the desired value as herein referred to is the deviation which remains when the controlled variable has approached the desired value as far as possible. It constitutes a measurement for determining calibration, hysteresis, and zero errors. Aside from complying with the general requirement that the residual deviation should be very small, the governor according to the invention also fulfills the requirement that this deviation will be identical at every P range to which the governor may be set.

The above-mentioned objects, features, .and advantages of the present invention will become further evident from the following detailed description thereof, particularly 3 when the same is read with reference to the accompanying drawings, in which- FIGURE 1 shows a somewhat diagrammatic view partly in section of a governor according to the invention in which the opposite resilient elements of each pair are disposed coaxially to each other and are enclosed by a e;

FIGURE 2 shows a view similar to FIGURE 1 of a modification of the invention, in which the opposite ringencloscd resilient elements are slightly inclined to each other;

FIGURE 3 shows a similar view of a further modification of the invention, in which the opposite resilient elements are coaxial and act upon an inner ring;

FIGURE 4shows a diagram which illustrates the operation of a governor according to FIGURE 1; while FIGURE 5 shows a diagram which illustrates the operation of a governor according to FIGURE 2.

The governor according to the first embodiment of the invention as illustrated in FIGURE 1 primarily consists of four resilient elements in the form of bellows 11 to 14, the inner ends of which are secured to a central support 15 which is rigidly connected to the housing of the apparatus, not shown. These bellows are arranged in pairs opposite to each other from a common center .and are :all disposed within the same plane, and the bellows of each pair have a common axis which is disposed at right angles to the common axis of the other pair.

The outer ends of bellows 11 to 14 are tightly sealed and secured to the inner surface of a cylindrical ring 16 which also lies within the same plane as the bellows. If bellows 11 to 14 are not under pressure, the center 17 of ring 16 coincides with the point of intersection of the axes of the bellows.

In front of the central 14 a nozzle arm 18 is support 15 and bellows 11 to pivotably mounted at one end about the axis of support 15 which extends transverse to the taxes of the bellows. This nozzle arm 18 is adjustable within an angle of 90 for the purpose of setting the governor to the desired proportional range. The position of nozzle 18 may be read on a scale 19'.

The nozzle opening of arm 18 is disposed opposite to the outer peripheral surface of ring 16 which serves as a flapper surface for a jet of compressed air which is supplied through a conduit 18' and serves for controlling a pneumatic amplifier, not shown.

The actual value and the desired value of the controlled variable are provided in. the form of pneumatic pressures which are supplied through inlet conduits 11' and 12' to the inner ends of bellows 11 and 12 which are secured to the central support 15 and are otherwise tightly sealed. A compressed air conduit 60 branches off of conduit 18' and leads to a conduit 14 supplying compressed air to bellows 14, and also leads to exhaust line 62. A control throttle 64 is provided in conduit 14". Downstream of throttle 64, a conduit 13' leads from conduit 14 to bellows 13. Conduit 13 is provided with a control throttle 66. By providing

pneumatic throttles

68, 70, effectively regulating the pressure in the lines leading to

bellows

13 and 14, respectively, it is possible to adjust the feedback eifect which is exerted by

bellows

13 and 14. Within the path between

throttles

68 and 70, the air pressure will depend on the distance of discharge nozzle 18 from the impact ring 16. This air pressure will reach differential bellows 14 through conduit 60, control throttle 64 which causes a slight delay, and conduit 14. The air pressure reaclu'ng integral bellows 13 through conduit 13 is further delayed by throttle 66.

The pneumatic governor as illustrated in FIGURE 2 is of a construction very similar to that as above described. It also comprises four resilient elements in the form of bellows 21 to 24, the inner ends of which are secured to the central stationary support 25 on the housing of the apparatus, and which are tightly sealed excompressed air.

necessary. The outer ring 26 wlu'ch again serves as a flapper plate surrounds bellows 21 to 24, the closed cuter ends of which engage against the inner surface of ring 26. Nozzle arm 23 is again pivotably mounted at 27 on the central support 25 in front of bellows 21 to 24, and it is supplied with compressed air through a conduit 28'. For reading the position of the end of arm 28, a scale 2% is provided. If bellows 21 to 24 are not under pressure, the axis of ring 26 coincides also in this case with the pivotal axis of nozzle arm 28.

The important difference between this embodiment according to FIGURE 2 from that according to FIGURE 1 resides in the fact that the opposite bellows of each

pair

21, 22 and 23, 24, respectively, are not disposed coaxially to each other, but they are slightly inclined to each other. However, also in this case, the axes of all bellows intersect with the axis of rotation of nozzle arm 28.

More specifically, the bellows of the governor accord ing to FIGURE 2 are arranged so that the axes and thus the effective directions of the two bellows 23 and 24 for the feedback action are slightly inclined toward a V-shape relative to each other and in the direction toward the bellows 21 for the actual value. Similarly, the axes and thus the effective directions of the two bellows 2-1 and 22 for the comparison of the actual value and the desired value are also slightly inclined toward a ii-shape relative to each other and in the direction toward the bellows 23 forming the integral resilient element. Furthermore, the effective surface area of this bellows 23 is slightly larger than that of the difierential bellows 24-. In addition, ring 26 which is connected to bellows 21 to 24 and serves as a flapper surface may be made of such a material and of such geometrical dimensions that it will be elastically deformed to an elliptical shape of a very small eccentricity when acted upon by a pressure from one side. 7

While in the embodiments according to FIGURES l and 2, the ring which serves as a flapper surface surrounds the belloWs-shaped resilient elements, this is not absolutely necessary, but this ring may also be disposed between these elements, as diagrammatically illustrated, for example, in FIGURE 3. This pneumatic governor is again provided with four bellows-shaped resilient ele' ments 31 to 34. However, in this case the outer ends of the bellows are supported on a ring 35 which is rigidly secured to the housing of the governor, not shown, while the inner ends of the bellows are positively connected to the outer surface of a cylindrical ring 36 which lies within the point intersection of the axes of bellows 31 to 34 when the later are not under pressure, and it also forms the axis of rotation of the nozzle arm 38. The nozzle opening of arm 38 faces in this case toward the inner peripheral surface of ring 36 which thus serves as a flapper surface. Bellows 31 and 32 are acted upon by compressed air which is supplied through conduits 31' and 32, while the jet of compressed air which is directed upon ring 36 through nozzle 38 is supplied thereto through a conduit 38. The angular position of the nozzle may also in this case be read on a scale 39. Conduit 38 is provided with

throttles

72, 74, corresponding to the throttles provided in conduit 18' of the FIGURE 1 embodiment. A conduit 76 branches oil of 38 between

throttles

52 and 54 and leads to a vent conduit 78 and to a conduit 34' supplying compressed air to bellows 34. Conduit 34' is provided with a throttle 80 for controlling the differential effect. Downstream of throttle 80 to 24' through which these b6l-' Compressed} may be supplied in the same manner as described above in connection with the corresponding conduits of the FlGURE l ein-' bodiment; accordingly, further description thereof is uh a conduit 33 leads from conduit 34 through a throttle 82 for controlling the integral effect to bellows 33.

Although the two bellows of each pair 31, 3-2, and 33, 34 are illustrated in FIGURE 3 as being coaxial and as extending at right angles to the other pair similarly as in the embodiment according to FIGURE 1, they can also be slightly inclined to each other toward a V-shape similarly as in the embodiment according to FIGURE 2. Furthermore, the integral bellows 33 may also be provided with a larger effective surface area than the differential bellows 34-, and ring 36 may also be elastically deformable.

Aside from designing the governor according to the invention in the manner as illustrated in FIGURES 1 and 2, it is also possible to design the outer ring which surrounds the bellows and serves as a flapper surface so as to extend in the axial direction thereof beyond the bellows so that the inner peripheral surface of the ring may then be used as the flapper surface against which the compressed air is blown from the nozzle in a manner similarly as shown in FIGURE 3. Finally, instead of making the ring which forms the flapper surface so as to be movable relative to the stationary center of the system and to mount the nozzle arm so as to be pivotable about this center, it is also possible to mount the flapper ring in a stationary position and to design the rotary axis of the nozzle arm so as to be adjustable under the action of the resilient elements.

The manner of operation of the governors according to the invention will now be described in detail with reference to the diagrams according to FIGURES 4 and 5.

The diagram as shown in FIGURE 4 corresponds to a governor according to FIGURE 1. The vectors 41 to 44 represent the forces which are exerted from the center part 45 of the governor by the bellows under action of the compressed air upon the ring which is indicated by the circle 46.

Vectors

41, 42, and 43, 44, respectively, have the same 'eflective directions and the two pairs of vectors are disposed at right angles to each other.

A deviation from the desired value, at which the pressure in the bellows for the desired value and at which the force component 41 is therefore greater than the force component 42 may result, for example, in a displacement of ring 46 from the position a to the position b, as indicated by dotted lines, by a certain amount x Depending upon the position of nozzle 48 at the periphery of ring 4d, the change in distance s between the nozzle and the outer surface of the ring which serves as a flapper surface will be of a different size. The greater the angle a is between the axis of the resilient elements for the actual and desired values, that is, between the elfective line of vectors 41 and 4-2 and the position of nozzle 48, the smaller will be the influence which a deviation from the desired value exerts upon the control element, ie the nozzle 48. This means that the proportional range of the governor changes with a change of the position of the nozzle. The proportional range which may be adjusted by pivoting the nozzle may be read on scale 19 as shown in FIGURE 1. If the angle a, which is indicated in all of the drawings, amounts, for example, to the governor is adjusted to the smallest proportional range, whereas if the angle 04 increases, the proportional range also increases, and at an angle of 90 it reaches the value infinity. The influence 'of the

forces

43 and 44 which exert a feedback effect is, however, the greatest at an angle a of 90. The more the angle on decreases, the smaller will also be the feedback influence which will reach its smallest value at the angle of 0.

Although a governor as previously described may be used for many purposes, it has the disadvantage that, if the nozzle is pivoted about the angle a, not only the proportional range of the governor, but also its initial proportional band will be changed. If nozzle 48 is placed at the position as indicated in FIGURE 4 in full lines, ring 46, when deflected by an amount x will move toward the nozzle by a distance s which depends upon the angle and is approximately equal to the formula s=x .cos a.

The initial proportional band depends upon the angle on in accordance with the formula initial proportional band=k/ cos a, in which k means a constant.

As already mentioned, it the governor is to comply with high requirements, the extent of the dependence of the initial proportional band upon the angle or should be as small as possible. This will be attained by a governor which is designed as illustrated in FIGURE 2, since the initial proportional band will then remain constant at all positions of nozzle 48.

The manner of operation of a governor according to FIGURE 2 will now be described with reference to the diagram as shown in FIGURE 5. In this diagram, the arrows 51 to 54 again represent the forces which are exerted by the slightly inclined, V-shaped resilient elements 21 to 24 upon the flapper ring 26 which is indicated in FIGURE 5 in its basic position a by the fullline circle 56. If the actual value differs from the desired value, ring 56 will at first move for the distance x to the position b, as it has already been described with reference to FIGURE 4. Due to the V-shaped arrangement of the feedback bellows 53 and 54, the same deviation from the normal position will in this case result in an additional travel for a distance x which moves the ring to the position 0. The movement of distance x; occurs because the

inclined vectors

53 and 54 have a resultant in the upward direction in FIGURE 5, that is, in the direction of movement x Due to the tilt of the bellows and the increase of the effective area of integral bellows 23, the pneumatic forces will no longer counterbalance each other, but will create a resultant force effecting the described movement of the ring. Simultaneously with the movement of the ring, an increase in the mechanical restoring forces takes place. The magnitude of the restoring forces is determined by the resilient property of the bellows and the direction of the restoring forces is determined by the position of the bellows ends. The movement of the ring will cease when the pneumatic forces and the mechanical forces have reached equilibrium. Since the effective surface area of the integral bellows 53 is slightly larger than that of the differential bellows 54, the ring will be further shifted for a distance x;, to the position d. If the ring 1s made of a suitable resilience it will under the influence of the force of the feedback bellows which is of a greater strength than the force of the bellows for the actual and desired values, be deformed to an elliptical shape of a small eccentricity, as indicated by the line e. In this position, the quadrant of the ring which forms the flapper surface along which the proportional range may be adjusted extends almost parallel to the quadrant r along which the nozzle 58 is pivoted. The initial proportional band is thus no longer dependent upon the angle on to which the nozzle is adjusted, that is, upon the proportional range to which the governor has been set.

The V-shaped inclination of the

bellows

51 and 52 for the actual and desired values in the direction toward the integral bellows 53 produces the advantage that the small residual deviation from the desired value will be independent of the setting of the proportional range.

In accordance with the very small control movement of the nozzle relative to the flapper surface which amounts only to a few ,u, that is, about 0.1 mil, the actual deviations of the geometrical dimensions of the governor according to FIGURE 2 from the dimensions of the gov ernor according to FIGURE 1 are very small, even though the effect of these small deviations is very considerable as can be seen in FIGURE 5.

The foregoing statements relating to the governors according to FIGURES 1 and 2 and the diagrams as shown in FIGURES 4 and 5 also apply similarly to a governor which is designed according to FIGURE 3.

Although our invention has been illustrated and described with reference to the preferred embodiments thereof, we Wish to have it understood that it is in no way limited to the details of such embodiments, but is capable of numerous modifications within the scope of the appended claims.

Having thus fully claim is:

1. An automatic pneumatic governor comprising at least a pair of resilient elements adapted to be acted upon by a pressure medium representing a desired value and an actual value of a controlled variable and disposed substantially diametrically opposite to each other, at least a second pair of resilient elements also adapted to be acted upon by a pressure medium for producing a feedback efiect and also disposed substantially diametrically opposite to each other and at substantially right angles to said first pair, all of said elements being disposed within a common plane and together forming a star-shaped arrangement having a common center, means for supporting one end of each of said elements in a fixed position, the other end of each element being movable under pres-' sure, means for supplying said pressure media to said elements, a ring disposed within said common plane, said other ends of said elements being in engagement with and acting upon said ring, a nozzle member pivotably mountdisclosed our invention, what we ed for rotation about said common center, said ring having a peripheral surface disposed opposite to the nozzle opening of said nozzle member and serving as a flapper surface, and means for supplying a pressure medium-to said nozzle member and for directing it through said nozzle opening upon said flapper surface.

2. A governor as defined in claim 1, in which the axes of all of said resilient elements intersect with each other at said common center, said inner ends of said elements facing toward said center being connected to said fixed supporting means, said ring surrounding said elements and being positively connected to the outer ends thereof, the outer peripheral surface of said ring being adapted to serve as said flapper surface.

3. A governor as defined in claim 1, in which said ring is disposed intermediate said resilient elements and the inner ends of said elements are movable and in engagement with the outer peripheral surface of said ring, While the outer ends of said elements are connected to said fixed supporting means, the inner peripheral surface of said ring being ward each other and toward disposed opposite to the opening of said nozzle member and serving as said flapper surface.

4. A governor as defined in claim 1, in which said resilient elements of said second pair are slightly inclined toward each other and in the direction toward one of the elements of said first pair.

5. A governor as defined in claim 1, in which said resilient elements of said first pair are slightly inclined toone of the elements of said second pair.

6. A governor as defined in claim 1, in which one of said resilient elements of said second pair has a greater elfeotive surface area than the opposite element of said pair.

7. A governor as defined in claim 1, in which said ring serving as a flapper surface is made of such a material and has such geometrical dimensions that when acted upon by a pressure from one side it will be elastically deformed to an elliptical shape having a very small eccentricity.

8. A governor as defined in claim 1, in which'each of said resilient elements consists of a bellows.

9. An automatic pneumatic governor comprising resilient means adapted to be acted upon by a pressure fluid representing a desired value and an actual value of a controlled variable, be acted upon by a additional resilient means adapted to pressure fluid for producing a feedback effect, each of said resilient means having one end thereof secured in a fixed position, and the other end thereof being movable under pressure, means for supplying said pressure fluid to each of said resilient means, a nozzle member, means constituting a flapper surface contiguous to said nozzle member, means to enable pivotable movement of said nozzle member relative to said flapper surface to vary the proportional range of the governor, and means operatively connecting each of said resilient means with said means forming said flapper surface to vary the contour of said flapper surface to maintain the sensitivity of the governor substantially constant over its entire proportional range.

References Cited in the file of this patent UNITED STATES PATENTS 2,585,347 Robins Feb. 12, 1952 2,736,199 Ibbott Feb. 28, 1956 2,742,917 Bowditch Apr. 24, 1956 FOREIGN PATENTS 568,634 Great Britain Apr. 13, 1945

Claims

1. AN AUTOMATIC PNEUMATIC GOVERNOR COMPRISING AT LEAST A PARI OF RESILIENT ELEMENTS ADAPTED TO BE ACTED UPON BY A PRESSURE MEDIUM REPRESENTING A DESIRED VALUE AND AN ACTUAL VALUE OF A CONTROLLED VARIABLE AND DISPOSED SUBSTANTIALLY DIAMETRICALLY OPPOSITE TO EACH OTHER, AT LEAST A SECOND PAIR OF RESILIENT ELEMENTS ALSO ADAPTED TO BE ACTED UPON BY A PRESSURE MEDIUM FOR PRODUCING A FEEDBACK EFFECT AND ALSO DISPOSED SUBSTANTIALLY DIAMETRICALLY OPPOSITE TO EACH OTHER AND AT SUBSTANTIALLY RIGH ANGLES TO SAID FIRST PAIR, ALL OF SAID ELEMENTS BEING DISPOSED WITHIN A COMMON PLANE AND TOGETHER FORMING A STAR-SHAPED ARRANGEMENT HAVING A COMMON CENTER, MEANS FOR SUPPORTING ONE END OF EACH OF SAID ELEMENTS IN A FIXED POSITION, THE OTHER END OF EACH ELEMENTS BEING MOVABLE UNDER PRES-