US2756774A - Pneumatic toggle devices provided with adjustable fulcrums - Google Patents

Description

Pg l July 31, 1956 so 2,756,774

PNEUMATIC TOGGLE DEVICES PROVIDED WITH ADJUSTABLE FULCRUMS Filed April 21, 1950 INVENTOR.

ALFRED A. MAR/{SON [Li Y United States Patent PNEUMATIC TOGGLE DEVICESPRO VIDED WITH ADJUSTABLE FULCRUMS Alfred A. Markson, Mount Lebanon Township, Allegheny County, Pa., assignor to Hagan Corporation, Pittsburgh, Pa., acorporation of Pennsylvania Application April 21, 1950, SerialNo. 157,272

4 Claims. (Cl. 137-620) This invention relates to a pneumatic toggle device of the type having a beam provided with a fulcrum and a plurality of force developing units disposed on opposite sides of the fulcrum.

An object of this invention is to provide a device of the type referred to above in which one of the force developing units is provided with means that controls the conditions under which the force transmitting unit becomes operative to transmit a pressure through or to a sending line or device, or to reduce or shut oif transmission of pressure to such line or device.

Another object of the invention is to provide a device of the character referred to above in which the force developing units act on a beam provided with a doubleacting fulcrum whereby the ratio of the lengths of the lever arms from the fulcrum to the points where such force developing units act on the beam may be adjusted to a value of 1:1 or to values greater or less than 1:1.

A further object of the invention is to provide a pneumatic toggle comprising a beam having a double-acting fulcrum which is adjustable lengthwise of the beam, and a pair of pressure-responsive units on each side of and acting on the beam in opposed relation to one another at distances L1 and L2, respectively, from the fulcrum, each unit having a diaphragm coupled to the beam. In said device one of the units is provided with a valve actuated by movement of the beam for controlling the transmission of pressure from a supply source to a sending or output line, said pressure acting on said unit and on a unit on the opposite side of the fulcrum that exerts a turning force on the beam opposing the turning force of the device provided with the valve; and that a unit acting to oppose the valved unit is provided with means that controls the magnitude of a variable pressure received' thereby at which the beam of the device. is actuated to open the valve for the transmission of pressure or to close the valve and exhaust pressure from the sending line.

The above and other objects of the invention will in part be apparent and will in part be obvious from the following description taken in conjunction with the accompanying drawings, in which:

Figure l is a view in longitudinal vertical section of a totalizing device arranged and constructed in accordance with an embodiment of the invention; and

Fig. 2 is a view in section taken on line IIII of Fig. 1.

Throughout the drawings and the specification like reference characters indicate like parts; As shown in Fig. l, the toggle device embodying what now appears to be a preferred form of the invention, comprises a beam 1 provided with a double-acting fulcrum 2, that is supported in a frame 3.

The device also includes a plurality of pressurereceiving or input devices A, B, C, and D, arranged to exert forces on the beam proportional to the magnitude of the pressure input thereto. As shown, units A- and B are mounted on the same side of fulcrum 2 and are disposed to exert forces on the beam in opposition to "ice each other, the force of unit A being in a direction tending to turn beam 1 clockwise while the force of unit B acts on the beam in a direction to turn it counterclockwise as seen in Fig. 1. Units C and D are disposed on the opposite side of fulcrum 2 and are so connected to the beam that the forces exerted by them on the beam oppose each other. Withreference to Fig. 1, the force developed by unit D acts on beam 1 in a direction tending to turn it counter-clockwise while the force of unit C acts to turn the beam clockwise; therefore the forces of units C and D oppose each other.

Unit D, as will be explained later herein, is a combined pressure-receiving and pressure-sending or output unit. in order to function as a combined unit it embodies a valve 5 that is actuated in response to either clockwise or counter-clockwise motion of' the beam about the fulcrum. The pressures in units A and D are of equal magnitude, as they are interconnected; therefore when lever arms L and L2 are equal the moments of the forces of units A and D on the beam about the fulcrum will be equal and opposite.

7 Unit C may be termed a pneumatic toggling unit in that it is provided with means which renders it inoperative to apply a positive force to beam 1 until a predetermined pressure has been received by the unit. When the pressure received by the unit exceeds such predetermined value, the beam will be actuated in such a direction as to cause valve 5 to be actuated to admit afluid pressure to unit D from which the pressure is transmitted through a pipe to a pressure sending line.

The term pneumatic toggle as used herein means that valve 5 is either in zero or minimum pressure position or in a position to transmit a maximum pressure. That is to say the pneumatic toggle is one which is either on or off with respect to the output pressure.

In the form of device shown in Fig. l, the output pressure of unit D is connected to unit A through a pipe 6 and constitutes the input pressure for that unit. Unit B is provided with an input pipe 7 so that any desired predetermined constant pressure may be delivered to unit B. The pressure delivered to unit B may be zero gage or anyhigher gage pressure of constant value according to the operative characteristics required of the device.

Unit C is supplied with a variable input pressure from a pipe 8. The pressure supplied to unit C may be a single pressure sent out by a device (not shown) that responds to a condition at some point in a control or regulating system. The operation of the device shown in Fig; l is dependent upon the magnitude of the pressure supplied through pipe 8, as will be explained infra.

Beam 1 comprises spaced parallel bars 9 and 10, between which spacing blocks 11' are disposed at the opposite ends thereof. The bars and the spacing blocks are secured together in any suitable manner as by dowel pins 12, whereby the bars and the spacing blocks form a rigid beam having a slot 13 between them for accommodating fulcrum 2. Fulcrum 2 and units A, B, C, and D are mounted on frame 3.

Frame 3 comprises plates 15 and 16 disposed respectively above and below the beam 1. Plates 15 and 16 are spaced apart by means of spacing blocks 17 and 18 located at the opposite ends of the plates, the plates and spacing blocks being rigidly secured together by means of bolts 19.

Fulcrum 2 comprises a roller 21 that extends through slot 13 between beam bars 9 and.10, and a supporting axle 22. The supporting axle extends through the fulcrum roller 21 so that the roller is free to turn thereon. Axle 22 is mounted at its opposite ends in support blocks 23 disposed on opposite sides of-frame 3 and between the frame pIates-IS and 16, as shown. The upper and lower edges of blocks 23 are provided with clamping flanges 24 that engage the respective sides of plates 15 and 16. By mounting the axle 22 in blocks 23 as shown, the fulcrum may be adjusted lengthwise of beam 1. When the fulcrum has been placed in a particular desired location, the fulcrum is locked in place by tightening a nut 25 on one end of axle 22, whereby the support blocks 23 are clamped at their flanges 24 to the sides of plates 15 and 16.

Spacing block 18 may, if desired, be provided with tapped bores 27, by means of which the device may be mounted on a support (not shown).

As shown in Figure 1, the lines of action of the forces exerted by units A and B on beam 1 are equi-distant from the center of fulcrum roller 21. Therefore, the distance from these lines of action to the center of the fulcrum may be designated as lever arm L1. Also, the lines of action of the forces of units C and D on beam 1, are equi-distant from the center of fulcrum roller 21, therefore, this distance is designated as lever arm L2. By adjusting lever arms L1 and L2 relative to each other, as by moving the fulcrum one way or the other along slot 13, the operating characteristics of the device may be modified.

As shown in the drawings, units A and B are identical in construction. Therefore, a description of one of them will serve as a description for the other. Units A and B each comprise a flexible diaphragm 30, the marginal edge of which is seated in an annular recess 31 formed in the frame plate 15 or 16 and upon which is mounted a bonnet or housing 32 having a cavity 33 therein. The bonnets 32 are secured to the frame plates 15 and 16 by means of bolts 39. Cavity 33 is closed by the diaphragm when the bonnet is secured to the frame plate so as to clamp the marginal edge of the diaphragm firmly between the bonnet and the plate. The free portion of the diaphragm lies in an opening 33 in its supporting plate and is operatively connected to beam 1 by means of a bolt having a flanged head 34 and a threaded shank 35. A ring 36 is clamped against the diaphragm by a nut 37 threaded on the shank 35, as shown. Thus, the central portion of the diaphragm is clamped between the flanged head 34 and the clamping ring 36 whereby the central portion of the diaphragm is made rigid. As shown, each diaphragm of units A and B has a slack portion 4-9 disposed between the clamped marginal edge thereof and its rigid central portion. The walls of the slack portion engage the sides of the clamping ring 36 and the sides of the openings 33 in the frame plates, By this form of construction the effective areas of the diaphragms will be substantially unaffected by the magnitude of the pressure imposed thereon throughout the operating range of the device. The end of'the threaded shank 35 engages the beam. In a preferred form of construction, the outer end of the threaded shank is reduced in diameter so that it may be received in a locating aperture 41 in beam 1.

From the above description it will be seen that units A and B each have a pressure chamber to which either a constant or a variable pressure may be supplied. In the arrangement as shown, the pressure supply to unit A will be equal to and vary in magnitude with the pressure in unit D.

Unit C comprises a diaphragm 50, the marginal edges of which are seated in an annular recess 51 in frame plate 15. The portion of the diaphragm within the recess 51 is disposed across an aperture or opening 52 in plate 15 so that the diaphragm may be operatively coupled to beam 1. The marginal edge of the diaphragm is clamped to plate 15 by means of a bonnet 53 having a cavity 54 therein which, when closed by the diaphragm, forms a pressure-tight chamber. The central portion of the diaphragm is rigid and coupled to the beam by features like those employed in units A and B and are therefore designated by the same reference characters.

The diaphragm of unit C is provided with means for exerting a loading force FS thereon in opposition to the force of the pressure in chamber 54 acting on the diaphragm. This means comprises a tension spring 57, the lower end of which is anchored by means of a ferrule 53 to the flanged head 34 of the clamp bolt and the opposite end of which is secured to a block 58 by means of a ferrule 59, block 58' being carried on a threaded support member 60.

Threaded member 60 is supported by a tubular housing 1, the lower end of which is secured to the top of bonnet 53 in pressure-tight relationship therewith. As shown, element 60 is threaded through the top of hous ing 61 and is provided with a gasket 62 and a nut 63 whereby a pressure-tight joint may be formed at the place where the element 60 passes through the upper end of housing 61. By means of threaded member 60, the initial tension in spring 57 may be adjusted. If, for example, L1=L2 and the initial tension in spring 57 is such as to exert an upward force on the diaphragm 50 of 10 lbs. it will be apparent that the diaphragm 50 will not exert a force on beam 1 until the force of the pressure introduced into the chamber 54 by pipe 8 exceeds 10 lbs. per sq. in., it being assumed that the effective area of diaphragm 50 is 1 sq. in. When the force exerted by the pressure introduced into the chamber 54 exceeds 10 lbs. per sq. in. gage, diaphragm 50 will exert a force on the beam that is proportional to the excess of pressure over the initial restraining force of 10 lbs. imposed by the spring. When the force exceeds 10 pounds, beam 1 is tilted in the direction required to open valve 5 whereby pressure is transmitted from the supply source to the sending line.

Unit D includes a diaphragm 65 having its marginal edge seated in a recess 66 in frame plate 16. This diaphragm has a rigid central portion formed by elements similar to those employed in units A and B, therefore, these elements are designated by the same reference characters. As in the diaphragms of units A, B and C, diaphragm 65 has a slack portion located between its rigid central portion and the marginal edge thereof. The diaphragm operates in an opening 67 in the plate. Unit D includes a bonnet 68 which is designed to accommodate valve 5. This bonnet is secured to the frame plate 16 by means of bolts as shown, and clamps the marginal edge of the diaphragm to the plate.

Valve 5 comprises a body 63 that is threaded into the bonnet, as shown, and a valve stem 70. The outer end of the valve stem is provided with a valve element 71 disposed to seat on a valve seat 72 at the inlet port of the valve body. The inner end of valve stem seats in an exhaust port seat 72 formed in the flanged head 34. The shank 35 is provided with a longitudinal bore that provides communication between the chamber 75 of bonnet 68 and the atmosphere. The valve stem may, if desired, be provided with a light compression spring 76 disposed between the inner end of the valve body 59 and a collar 78 secured to the valve stem, whereby the valve stem may be urged in a direction to normally close the inlet port. The type of valve shown is what may be designated as a neutral position valve, that is, when the sum of the moments of the forces acting on beam 1 about fulcrum 2 is Zero, both the inlet port and the exhaust port of valve 5 are closed.

The operation of the device is as follows:

Let the pressures applied to the diaphragms of units A, B, C, and D be designated P1, P2, P3, and P4, respectively, and the force exerted by spring 57 in a direction opposing the force of pressure supplied to chamber 54 and acting on the diaphragm of unit C be designated FS, then the following equation satisfies the conditions under which the sum of the moments of the forces exerted by the diaphragms on beam 1 is equal to Zero:

From which it follows that If L1 is equal to L2 then P4=P1-P2+ (Ps-FS). When the sum of the moments about the fulcrum is zero, then (P1P2)+(P3FS) P4=0. If Pl=P2 and FS is greater than P3 then P4 goes from maximum to zero when FS exceeds Pa.

By changing the position of fulcrum 2, thereby either increasing or decreasing L1 with respect to L2, it will be seen that the conditions under which the pressure P4 goes from zero to P4 maximum or from P4 maximum to zero, are modified as the ratio of L1 to L2 is modified.

If the pressure P2 is greater than zero, it follows that the effect of this pressure on the operation of unit D will be additive to the force exerted by spring 57 on the diaphragm of unit C.

When the length of lever arm L1 is equal to the length of lever arm L2, the pressure P4 will increase from zero gage to the value of the pressure in the supply pipe connected to the inlet port of valve 5 when the force of pressure P: exceeds the opposing force P8 of spring 57. If the pressure P2 is Zero, or whenever the force of pressure Pa exceeds the opposing force of spring 57 and the opposing force exerted by the diaphragm of unit B when the pressure P2 is greater than zero, valve 5 will be opened as above described. The ratio L1/L2 determines the change in pressure P3 required to return or decrease the pressure of P4 of unit D to zero.

Having thus described the invention, it will be apparent to those skilled in this art that various modifications and changes may be made in the construction and arrangement of the details thereof without departing either from the spirit or the scope of the invention.

Therefore, what is claimed as new, and desired to be secured by Letters Patent, is:

1. A pneumatic toggle device comprising a beam, a double-acting fulcrum for said beam disposed between the ends thereof, a pressure-receiving unit mounted on each side of said fulcrum, said units acting on said beam at distances L1 and L2, respectively, from said fulcrum, and exerting opposed turning forces on the beam, and a pressure-actuated toggling unit mounted on one side of the fulcrum in opposed relation to one of said units, and acting on said beam at a distance L2 from the fulcrum, each of said pressure-receiving units comprising a bonnet having an open side facing said beam, and a flexible diaphragm secured across said open side to form in its associated bonnet a pressure-tight chamber, said diaphragms being operatively connected to said beam and exerting opposed turning forces on the beam with respect to said fulcrum, a valve actuated by said beam for supplying a medium under pressure to said pressure-receiving units, said valve being normally closed, said toggling unit comprising a bonnet having an open side facing said beam, a diaphragm across said opening forming in said bonnet a pressure-tight chamber, said toggling unit diaphragm having means for applying a force to said beam at a point directly opposite to the point where the adjacent pressurereceiving unit acts on said beam, a pressure-tight member supported by said bonnet in pressure-tight relationship therewith, said member having communication with the interior of the bonnet, and having therein a yieldable tension member connected to the diaphragm and exerting a predetermined force thereon in a direction to urge the diaphragm out of force-exerting relation with said beam, said toggling unit diaphragm acting on said beam to exert a turning force thereon to unbalance said beam and actuate" said. valve to open position when. the force of pressure actingron said toggling unit diaphragm exceeds the opposing force of said tension member.

2. A device according toclaim 1 characterized'by the fact that the device includes a pressure receiving, unit having a bonnet and a pressure responsive diaphragm arranged to exert a force of a predetermined value on said beam in the same direction as the toggling unit but on the opposite side of said fulcrum.

3. A pneumatic toggle device comprising a beam, a double-acting fulcrum for said beam disposed between the ends thereof, a pressure-receiving unit mounted at each side of said fulcrum, said units being connected to receive the same pressure and acting on said beam in opposed relation at distances L1 and L2, respectively, from said fulcrum, and a pressure-actuated toggling unit mounted on one side of the fulcrum in opposed relation to one of said units and acting on said beam at a distance L2 from the fulcrum, each of said pressure-receiving units comprising a bonnet having an open side facing said beam, and a flexible diaphragm secured across said open side to form, in its associated bonnet, a pressure-tight chamber, said diaphragms being operatively connected to said beam to exert opposing forces thereon and tending to turn said beam in opposite directions about said fulcrum, said toggling unit comprising a bonnet having an open side facing said beam, a diaphragm across said opening forming in said bonnet a pressure-tight chamber, and means urging said diaphragm in a direction opposing the force of the pressure acting thereon, a valve embodied in the pressure-receiving unit that is directly opposed to said toggling unit, said valve being normally closed and com prising a valve body secured to said bonnet and communicating with the chamber therein, said bonnet having an inlet port provided with a seat, a valve stem in said body having a valve element adjacent one end thereof disposed to seat on the inlet port seat, said diaphragm having an exhaust port and a seat therefor, the opposite end of said valve stem being disposed to seat in the exhaust port seat, both valve ports being closed by said stem when the beam is in neutral position, the inlet port being opened when the force of pressure on the toggling unit diaphragm exceeds the restraining force acting thereon by said urging means, whereby the pressure in said receiving units is increased to a value equal to that of the supply source connected to the valve, when the pressure on the toggling unit diaphragm exceeds the force of the urging means thereon.

4. A device of the character described, comprising a beam, a double-acting fulcrum for said beam, pressurereceiving units on opposite sides of said fulcrum and disposed to exert opposed turning forces on the beam, one of said units being a pressure-receiving and sending unit, each unit being provided'with a flexible diaphragm disposed to exert a force on said beam whose magnitude is proportional to the value of the pressure acting thereon, valve means actuated by said beam for normally supplying a predetermined minimum fluid pressure to said pressure-receiving and sending unit, and to said pressurereceiving unit when the beam is in one position, and for supplying a predetermined maximum pressure to said pressure-receiving and sending unit and said pressurereceiving unit when the beam is actuated to another position, a pressure-receiving toggling unit having a flexible diaphragm disposed to exert a force on said beam opposing the force developed by the pressure in said receiving and sending unit, and means acting on the diaphragm of the toggling unit for rendering said toggle unit inoperative to exert a turning force on said beam until a pressure of a predetermined value is applied to its diaphragm, at which time the beam is actuated by the toggling unit diaphragm to cause the valve means to be actuated to supply a maximum pressure to said pressure-receiving and pressure-receiving and sending units.

(References on following page) 7 References Citedin the file of this patent 2,436,451 UNITED STATES PATENTS 2,073,838 Hammond Mar. 16, 1937 2,247,056 Howard June 24, 1941 2,304,783 Donaldson Dec. 13, 1942 536,537

' 8 Rosenberger Feb. 12, 1948 Markson Nov. 30, 1948 McLeod May 2, 1950 FOREIGN PATENTS Great Britain May 19, 1941

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