US3682048A

US3682048A - Force-balance pneumatic regulator with resilient cross fulcrum, having high sensibility and precision and easy, continuous gain regulation

Info

Publication number: US3682048A
Authority: US
Inventors: Giorgio Bergamini
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-09-11
Filing date: 1970-11-06
Publication date: 1972-08-08
Anticipated expiration: 1989-08-08
Also published as: DE1958378B2; DE1958378C3; FR2085560B1; FR2085560A1; DE6945086U; NL6917445A; DE1958378A1

Abstract

A pneumatic force-balance regulator is described that has a pair of bellows which respectively support members, movable in response to differences in the external and internal pressures on the bellows, that are connected through struts to a balance mounted to oscillate around a resilient cross fulcrum so that the regulator gain may vary with continuity and the axes of the struts lie in the plane containing the axis of oscillation of the balance so that parasitic forces, acting on the struts along their axes, do not affect the equilibrium of the balance.

Description

United States Patent Bergamini [45] Aug. 8, 1972 [54] FORCE-BALANCE PNEUMATIC 7 2,365,573 12/ 1944 McGay ..73/407 REGULATOR WITH RESILIENT CROSS 2,816,444 l2/ 1957 Gomez ..73/407 FULCRUM, HAVING HIGH 3,126,744 3/1964 Hermanns ..73/407 SENSIBILITY AND PRECISION AND 3,078,719 2/1963 Cordero et al ..73/407 EASY, CONTINUOUS GAIN 3,354,722 11/1967 Waite et al. ..92/37 REGULATION 3,451,272 6/ 1969 Frey et al ..73/410 [72] Inventor: Giorgio Bergamini, Corso Sicilia, 56 Primary Examiner Marfin R Schwadron Italy Assistant Examiner-Leslie J. Payne [22] Filed: Nov. 6, 1970 Attomey-Ralph M. Watson 3 [21] Appl. No.: 87,495 I I [57] I ABSTRACT:

A pneumatic force-balance regulator is described that [30] Foreign Applmmon Pmmvty Data has a pair of bellows which respectively support mem- Sfipt. ll, bets movable response to difi'erences in the exter.

, nal and internal pressures on the bellows, that are con- }.LE.CCII. ..L nected through truts to a mounted to oscil- I! late around a resilient cross fulcrum so that the regula [58] Fleld OI Search l37/82, 84; 73/410, 407; tor g y y with continuity d h axes f the 7 92/37 39 struts lie in the plane containing the axis of oscillation of the balance so that parasitic forces, acting on the [56] References Cited struts along their axes, do not affect the equilibrium of UNITED STATES PATENTS the balance- 2,75l,457 6/1956 Donaldson ..92/37 X 2 Claims, 3 Drawing figures PAIENTEDAus 8 I972 3,682,048

SHEEIlDFZ INVENTOR. 13%

SHEET 2 [IF 2 INVENTOR.

PATENTEDAus 8 m2 FORCE-BALANCE PNEUMATIC REGULATOR WITH RESILIENT CROSS FULCRUM, HAVING HIGH SENSIBILITY AND PRECISION AND EASY,

CONTINUOUS GAIN REGULATION I The present invention relates to a force-balance pneumatic regulator with resilient cross fulcrum, which, by eliminating clearances, frictions and undesired moments, presents a high sensitivity and precision and allows an easy continuous gain regulation.

It is known that in the designing of a force-balance pneumatic regulator the following problems above all have to be solved:

a. realization of a balance whose fulcrum present neither. clearances nor frictions in such a way to make possible a high sensitivity;

b. the effective areas of the measurement elements (bellows) of the pressures compared two by two, must be the more equal possible to reach a high precision of regulation;

c. the ratio of the thrusts acting on the balance (and i.e. the regulator gain) has to be varied in a simple way and with continuity, by varying the balance fulcrum position, without introducing parasitic forces on the same balance which would reduce noticeably both the sensitivity and the precision of regulation of the regulator. 1

Now, the prior art knows different types of pneumatic regulators having force-balance, none of them, however, is able to satisfy at the same time the three above-mentioned conditions.

Thus are known pneumatic regulators which adopt as fulcrum, ball'bearings, hard stones or pairs of little rolls, which allow to solve well condition but do not I satisfy well condition (a). Said regulators therefore do not present a high sensitivity.

Other pneumatic regulators having force-balance adopt resilient cross fulcra, which satisfy very well condition (a) but make extremely difficult the solution of problem (c), which is really resolved by means of complex devices, noticeable compromises and to detriment of the regulation precision. Therefore, these regulators, besides to a limited precision, do not allow an easy, continuous gain regulation. As far as condition (b) is concerned, have been designed force-balanced pneumatic regulators wherein the equality of the effective areas is reached by making use only of a bellow with which the pressures are compared between the inside and the outside of the bellow self. These regulators have however this drawback: the connection between the bellow, placed inside a pressure chamber, and the balance which is outside said chamber, introduces, due to the frictions, some disturbances which result in a noticeable reduction of the precision of regulation of the same regulators.

The object of the present invention is that of obviating all the above-mentioned drawbacks and therefore the accomplishment of a force-balance pneumatic regulator which, by satisfying all the three above-mentioned conditions, present a high sensitivity and precision and allows an easy and continuous regulation of its gain. This is achieved by adopting a resilient cross fulcrum and only a bellow for each pair of pressures to be compared.

According to an essential feature of the invention, a resilient cross fulcrum of particular structure is utilized, which allows to vary with continuity the regulator gain by letting simply rotate said fulcrum around an axis perpendicular to the oscillation axis of the balance connecting the two bellows.

Another feature of the invention is given by the fact the connection of the bellows to the balance is realized by means of through struts whose axes lie in the plane containing the .balance of oscillation axis, whereby the parasitic thrusts acting on said through struts and relative seal membranes, being directed along the axes of the struts, do not at all effect the equilibrium of the balance and therefore the precision of regulation of the regulator.

According to a further feature of the invention it is possible to vary the regulator gain also when the regulator is in operation, as moments introduced by friction on the balance by the rotation of resilient cross fulcrum are compensated by a tie rod whose axis lie in the plane containing the balance oscillation axis.

The. invention is now illustrated in detail with reference to the accompanying figures which represent a preferred embodiment of the invention, given only by unrestrictive example, as technical and constructional modifications may be brought without departing from the scope of the present invention.

FIG. 1 shows a cut-away front section of the forcebalance pneumatic regulator with resilient cross fulcrum, according to the invention.

FIG. 2 shows a broken-away perspective view of the resilient cross fulcrum according to the invention.

FIG. 3 shows a cut-away top view of the pneumatic regulator of FIG. 1.

Referring to the figures, reference numeral 1 indicates the supporting plate of the pneumatic regulator on which, by means of threaded screws 2 and suitable gaskets,

boxes

3 and 4 are hermetically fixed. In each of said

boxes

3 and 4 and in

suitable cavities

5 and 6 made in supporting plate 1 are then housed respectively moving equipments 7 and 8 inside which one of the ends of

bellows

9 and 10 is respectively welded, whereas the other ends of the above-mentioned bellows are hermetically fixed to the heads of

boxes

3 and 4 respectively. In such a way four chambers are defined, two of which, 11 and 12 respectively, inside

bellows

9 and 10, and two, 13 and 14 respectively, outside said bellows whose effective areas are perfectly equal between them.

Two

helical springs

15 and 16, respectively inside

bellows

9 and 10, are then retained at one end by

spring bearings

17 and 18 respectively screwed at bottom of the moving equipments and at the other end retained by

other spring bearings

18 and 19 respectively, which may be screwed on the adjusting

screws

20 and 21 supported by the heads of

boxes

3 and 4.

Said adjusting

screws

20 and 21, by varying the tension of the

springs

15 and 16 and consequently the position uprightly of the moving equipments 7 and 8 allow the zero setting of the regulator. The two moving equipments 7 and 8 are then solidly connected to balance 22 of the regulator by means of

struts

23 and 24 respectively, which, extending in a perpendicular direction to the movement of the mobile equipments and protruding from holes placed in

boxes

3 and 4, are screwed on said balance by means of screws 25. To

cause the two

chambers

13 and 14 be hermetically closed, the two above-mentioned holes of

boxes

3 and 4 are closed by elastic seal membranes 26 which allow little vertical shiftings of through

struts

23 and 24 and therefore of mobile equipments 7 and 8.

Whereas set pressure is conveyed into chamber 13, through duct 27, the pressure to be controlled and to be kept always equal to the set pressure, is on the contrary conveyed into chamber 11 through duct 28. An inequality between the two above-mentioned pressures will result therefore in a vertical shift of the mobile equipment 7 and i.e. will give rise to a force which, transmitted by strut 23 to balance 22, will unbalance the balance self, by letting it oscillate around its fulcrum.

Said unbalance of the balance will be then compensated by the action of other two reaction pressures which are produced by a pneumatic relay (not shown in the figures) driven by nozzle 29 shutter plate system, the function of said shutter plate being effected by the same balance 22.

These reaction pressures conveyed into

chambers

12 and 14 respectively, through

ducts

30 and 31, bringing again the balance in a balance position, will compel the pressure to be controlled to become and to maintain itself equal to the set pressure.

The balance fulcrum 22, according a feature of the present invention, is then formed by two

platforms

32 and 33 suitably shaped as better seen in FIG. 2 and having two pivots 34 and 35 jointed to them. Upper platform 33 is inserted with its pivot 35 in a suitable hole made in an overhead plate 36, solidly connected to sup-- porting plate 1 by means of screwed little columns 37, and is fixed to said overhead plate by nut 38 and by carriage spring 39. Likewise, lower platform 32 is inserted with its pivot 34 in a suitable hole of balance 22 and fixed thereto by nut 40 and bycarriage spring 41. In such a way two

platfon'ns

32 and 33 are made integral respectively with balance 22'and with supporting plate 1 but they are free of rotating around a rotation vertical axis aa passing through their pivots. Each platform has then at the ends of its diameter a pair of flexible blades, double L shaped whereby the two platforms are joined between them by a cross resilient constraint. More precisely, flexible blades 42, each of them having a side of double L welded to the vertical wall of platform 33 (see FIG. 2), are let in through the slot of flexible blades 43, of platform 32 and are welded with other sides of the double L to vertical walls 44 of platform 32; flexible blades 43, welded in a side of the double L on the upper wall of platform 32, are on the contrary welded with other sides of double L under the lower wall of platform 33.

With such a constraint the two

platforms

32 and 33 are so made integral between them as far as the rotation around rotation axis an is concerned and moreover oscillations of lower platform 32 are made possible, and consequently of balance 22, around axis bb passing through the blades and perpendicular to rotation axis aa, Said oscillation axis bb represents just the axis around the which balance 22 will oscillate to restore the balance between the forces generated by the pressures acting on the

chambers

1 l, 12, 13 and 14.

Now, according to a constructional feature of the invention, oscillation axis bb lies always in the plane (designated cc in FIG. 1) passing through the center line of through

struts

23 and 24. This has, as a result,

the elimination of all the disturbances which arise in usual regulators due to the connection if a bellows inside a pressure chamber to a balance outside said chamber, disturbance which results in a noticeable lowering of the precision of regulation of the regulator self. As a matter of fact, the parasitic thrusts exerted by the pressures at stake on the through

struts

23 and 24 and on the relative resilient seal membranes 26, result in direct forces along the axis of the struts selves and i.e. in forces which, by acting in the same plane cc containing oscillation axis bb, cannot absolutely generate moments which tend to let oscillate balance 22 around axis bb and therefore to disturb the equilibrium of the balance self.

On the other hand, by adopting the above-mentioned cross fulcrum, the gain of the regulator may be now easily regulated with continuity by letting simply rotate the two

platforms

32 and 33 around their rotation axis aa. In this way, as matter of fact, the oscillation axis bb is put to rotation and consequently change the values of the distances d and e (see FIG. 3) from said axis bb of points F and G.

As these points F and G are the points of applications of the forces exerted on balance 22 respectively by the pressures acting on the bellows 10'and by the pressures acting on the bellows 9 and therefore distances d and e are lever arms of said forces it is evident that, by varying said lever arms, the moments exerted on the balance by said forces are varied and consequently the ratio of the thrusts acting on the balance and i.e. the gain of regulator is varied.

In order to facilitate the rotation operation of the platforms around axis aa as to regulate the regulator gain, to pivot 35 of upper platform 33, between nut 38 and carriage spring 39, is keyed a rack 45 meshed on a toothed small wheel 46 mounted idle on overhead plate 36. In such a way to vary the regulator gain it is sufficient to shift angularly rack 45.

To make possible the gain regulation also when the regulator is in operation and therefore to eliminate the moments introduced by friction on balance 22 by the rotation around axis aa of resilient cross fulcrum, on the end of the balance in correspondence of nozzle 29 is screwed a block 46 to which is hinged an end of a tie rod 47 the other end of which is hinged to another block 48 firmly screwed to supporting plate 1. The system of two blocks and of the tie rod is then arranged in such a way that the axis of tie rod lies on already cited plane cc containing oscillation axis bb so that the torque generated by it compensates always the abovementioned friction moments.

What I claim is:

l. A force-balance pneumatic regulator comprising a supporting plate, a pair of boxes fixed to said supporting plate to provide air chambers, bellows moving equipment contained in each of said boxes, a balance, a supporting plate, a resilient cross fulcrum for said balance comprising upper and lower platforms pivoted, respectively, to said balance and said overhead plate and solidly connected to said supporting plate, and pairs of double L-shaped flexible blades welded at the ends of a diameter of said platforms to join them together, and means to vary the gain of said regulator.

- 2. A force-balance pneumatic regulator comprising a supporting plate, a pair of boxes fixed to said supportrack keyed to the pivot for said upper platform, a toothed idler gear mounted on the overhead plate and meshing with said rack, and a tie rod hinged to said balance and to the supporting plate so that its axis lies on the plane containing the oscillation axis of the balance.

Claims

1. A force-balance pneumatic regulator comprising a supporting plate, a pair of boxes fixed to said supporting plate to provide air chambers, bellows moving equipment contained in each of said boxes, a balance, a supporting plate, a resilient cross fulcrum for said balance comprising upper and lower platforms pivoted, respectively, to said balance and said overhead plate and solidly connected to said supporting plate, and pairs of double L-shaped flexible blades welded at the ends of a diameter of said platforms to join them together, and means to vary the gain of said regulator.

2. A force-balance pneumatic regulator comprising a supporting plate, a pair of boxes fixed to said supporting plate to provide air chambers, bellows moving equipment contained in each of said boxes, a balance, a supporting plate, a resilient cross fulcrum for said balance comprising upper and lower platforms pivoted, respectively, to said balance and said overhead plate and solidly connected to said supporting plate, and means to vary the gain of said regulator comprising a rack keyed to the pivot for said upper platform, a toothed idler gear mounted on the overhead plate and meshing with said rack, and a tie rod hinged to said balance and to the supporting plate so that its axis lies on the plane containing the oscillation axis of the balance.