GB1592467A

GB1592467A - Mechanical force multiplier

Info

Publication number: GB1592467A
Application number: GB5176677A
Authority: GB
Original assignee: Deutsche ITT Industries GmbH; ITT Industries Inc
Current assignee: TDK Micronas GmbH; ITT Inc
Priority date: 1976-12-27
Filing date: 1977-12-13
Publication date: 1981-07-08
Also published as: DE2757047A1; FR2375509A1; JPS5382964A; CA1081062A; ES465440A1

Description

(54) MECHANICAL FORCE MULTIPLIER (71) We, ITT INDUSTRIES INC, a Corporation organised and existing under the Laws of the State of Delaware, United States of America, of 320 Park Avenue, New York 22, State of New York, United States of America do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to force multipliers and more particularly to mechanical force multipliers.

In a conventional diaphragm valve and air motor combination, a spring is required to exert its maximum force in the valve closed position. However, since the spring can only be compressed from the closed position, any movement of the spring from that point can only result in additional unnecessary force from the spring.

For example, a 3 inch weir diaphragm valve with 300 psi (pounds per square inch) line pressure requires 5,300 pounds of spring force to close the valve. Additional force exerted by the spring being compressed when the valve is open will result in 6,400 pounds of spring force for closure, yet when open, only 1,600 pounds of force is required to move the valve towards closure.

A conventional air motor utilizes a direct communication between the diaphragm of the diaphragm valve and the spring and air motor assemblies. This direct connection delivers the same force to the valve diaphragm that is applied by the spring and/or the air motor.

For example, a direct acting air motor is a fail open operator. That is, if air pressure to the operator is ever broken, then the valve will be opened. A spring is used to maintain the open position or open the valve when air is removed from the air motor. The air motor is used to close the valve. The spring force and the force delivered from the air motor in excess of the spring force will act directly on the valve diaphragm through the valve spindle.

A second example is a reverse acting air motor. This is a fail close operator. If air pressure to the air motor is ever broken, the valve will be closed. A spring is used to maintain the closed position or to close the valve when air is removed from the air motor. The air motor is used to open the valve. The spring force and any air motor force in excess of the spring force is transmitted directly to the valve diaphragm through the valve spindle.

Other valve operators have used linkage arrangements or scissors mechanisms to actuate valves. These devices use a primary link system with either a handwheel or a small air motor reacting directly on the primary link system. These devices are either limited in stroke because angular movement is small, thus limiting the stroke; or unable to accomplish full force multiplication to benefit the air motor size. Also, these devices are not used as fail safe actuators.

An object of the present invention is to provide an improved mechanical force multiplier.

According to the present invention there is provided a mechanical force multiplier comprising: a first link unit having at least a first pair of links, each of said first pair of links having one end thereof pivotably coupled to and in a force transferring relationship with one of an actuator and a device to be actuated and a second pair of links, each of said second pair of links having one end thereof pivotably connected to a stationary point and the other end thereof pivotably connected to the other end of an associated one of said first pair of links; a second link unit having at least a third pair of links, each of said third pair of links having one end thereof pivotably connected to said other end of an associated one of said first and second pair of links and the other end thereof pivotably coupled to and in a force transferring relationship with the other of said actuator and said device to be actuated; and at least one spring in a force transferring relationship with at least one of said first and second link units, said firs, second and third pairs of links defining a volume and said spring being disposed outside of said volume with the force thereof directed from the outside of said volume toward the inside thereof, said first and second link units being disposed between said actuator and said device to be actuated, said first and second link units co-operating with each other and said spring to apply to said device to be actuated an output force which is larger than the input force from the actuator and which increases in proportion to the input force derived from said actuator when said actuator is actuated.

The embodiments described provide a lighter mechanical force multiplier for a diaphragm valve with a lower center of gravity than previously known diaphragm valve operators.

In contrast to conventional air motor operators, the force multipliers to be described do not transmit forces from the spring and air motor directly to the diaphragm of the diaphragm valve. These mechanical force multipliers actually multiply input force from the springs and air motor before they are transmitted to the diaphragm of the diaphragm valve, thus allowing reduction in spring size and air motor size.

A spring acts through a set of linkages (known as primary links or first link units) which actually vary the output force from the spring from approximately 1 times the spring output to approximately 5.67 times the spring output force depending on the angle of the links forming the first link unit. The spring is under minimum required amount of compression at the position where the force multiplying effect is the largest and the spring is under the maximum required amount of compression at the position where the force multiplying effect is the smallest. The air motor forces are also transmitted through a set of linkages (known as secondary links or second link unit) which in turn transmit these forces through the primary or first link unit.

Because the air motor force uses the force multiplying effect of both the primary and secondary links, the air motor size can substantially be reduced. The force multiplying effect of the secondary links is the smallest when the force multiplying effect of the primary links is the largest. The force multiplying effect of the secondary links is the largest when the force multiplying effect of the primary links is the smallest. This stacked mechanical force multiplier arrangement effectively reduces the air motor size required.

In order that the invention can be clearly understood, reference will now be made toS the accompanying drawings, in which: Figs. 1 and 2 are diagrams illustrating how an applied spring force changes as the primary link angle changes when a constant output force is required; Fig. 3 is a chart illustrating how the spring force required for a spring to close the diaphragm of a diaphragm valve varies in a mechanical force multiplier in accordance with the principles of the present invention; Figs. 4 and 5 are force diagrams to enable equations (1) - (3) as set forth hereinbelow to be derived for a complete linkage or actuator system in accordance with the principles of the present invention; Figs. 6A and 6B are schematic drawings comparing the prior art valve operator unit with a valve operator unit embodying a multiplier according to an embodiment of the present invention; Fig. 7 is an overall diagrammatic view of a diaphragm valve with an operator unit incorporating the mechanical force multiplier in accordance with the embodiment of the present invention taken along line 7-7- of Fig: 8; Fig. 8 is a diagrammatic illustration of the overall diaphragm valve taken along line 8-8 of Fig. 7; Fig. 9 is a diagrammatic illustration of one mechanical force multiplier embodiment for a reverse acting diaphragm valve actuator in accordance with an embodiment of the present invention taken long line 9-9 of Fig. 10 with the diaphragm valve in a closed position; Fig. 10. is a diagrammatic illustration of the embodiment of Fig. 9 taken along line 10-10 of Fig. 9; Fig. 11 is a diagrammatic view of the mechanical force multiplier of Fig. 9 taken along line 11-11 of Fig. 12 with the diaphragm valve in a full open position; Fig. 12 is a diagrammatic view of Fig. 11 taken along line 12-12 of Fig. 11; Fig. 13 is a diagrammatic view of a second embodiment of the mechanical force multiplier for a direct acting diaphragm valve actuator taken along line 13-13 of Fig. 14 with the diaphragm valve in a full open position; Fig. 14 is a diagrammatic view of the mechanical force multiplier of Fig. 13 taken along line 14-14 of Fig. 13; Fig. 15 is a diagrammatic view of the mechanical force multiplier of Fig. 13 taken along line 15-15 of Fig. 16 with the diaphragm valve in a fully closed position; Fig. 16 is a diagrammatic view of Fig. 15 taken along line 16-16 of Fig. 15; Fig. 17 is athirdembodimentofamechan- ical force multiplier for a direct acting diaphragm valve actuator taken along line 17-17 of Fig. 18 with the diaphragm valve in a full open position; Fig. 18 is a diagrammatic view of the mechanical force multiplier of Fig. 17 taken along line 18-18 of Fig. 17; Fig. 19 is a diagrammatic view of the mechanical force multiplier of Fig. 17 taken along line 19-19 of Fig. 20 with the diaphragm valve in a fully closed position; Fig. 20 is a diagrammatic view of the mechanical force multiplier of Fig. 19 taken along line 20-20 of Fig. 19; Fig. 21 is a fourth embodiment of a mechanical force multiplier for a direct acting diaphragm valve actuator taken along line 21-21 of Fig. 22 with the diaphragm valve in a fully closed position; Fig. 22 is a diagrammatic view of the mechanical force multiplier of Fig. 21 taken along line 22-22 of Fig. 21; Fig. 23 is a diagrammatic view of the mechanical force multiplier of Fig. 21 taken along line 23-23 of Fig. 24 with the diaphragm valve in a full open position; and Fig. 24 is a diagrammatic view of the mechanical force multiplier of Fig. 23 taken along line 24-24 of Fig. 23.

Referring to Figs. 1 and 2 there is illustrated therein how the applied spring force Fs changes as the primary link angle changes when a constant output source FD is required.

These Figures illustrate that the mechanical force multiplier of the present invention changes from 1 to 5.65, depending on the angle of primary mechanical force multiplier links. The spring force will be maximum as illustrated in Fig. 1 where the force multiplication is the smallest (FD =Fs); whereas, the spring at minimum compression in Fig. 2 when the force multiplication is the largest (FD = 5.67 Fs).

Referring to Fig. 3, there is illustrated therein how the spring force required for a spring to close the diaphragm of a diaphragm valve varies in the mechanical force multiplier of the present invention. It should be noted that the maximum required force is 1,857 pounds and the minimum required force is 934 pounds. Due to this force multiplying effect, it is possible to use smaller springs in the mechanical force multiplier of the present invention, thus reducing the total spring weight and cost.

Referring to Figs. 4 and 5, the following equations are derived which are used to calculate force for a complete diaphragm valve actuator system in accordance with the principles of the present invention.

FD = i of Total Stem Thrust Fs = Force Required to Keep Primary Links in Equilibrium FL = Force Required in Secondary Link to Keep Primary Links in Equilibrium FA = 9 of Total Air Motor Force Required to Keep Primary Links in Equilibrium 2 FD Fs - (1) TAN 8

/SIN(180-8) \ FL=Fs(SIIN{(18$I)) (2) FFA=FLSIN (3) Equation (2) is obtained as follows: Definition: In a triangle with angles A, B, and C and sides opposite a, b, and c respectively, then: a b c SIN A = SIN B = SIN C Applying these equations to the triangle of Fig. 5 Fs FL SIN(o-)l SIN (180-0) therefore:

SIN (180 - H) FL = Fs SIN (180-0) SIN ( 8 - Referring to Figs. 6A and 6B, there is illustrated therein a comparison of the prior art diaphragm valve operator as shown in Fig.

6A and the diaphragm valve operator of the present invention as shown in Fig. 6B. Both the prior art operator of Fig. 6A and the operator of the present invention of Fig. 6B are reverse acting air motor assemblies for a 3" weir diaphragm valve. It will be noted that the center of gravity (C.G.) is lower in the operator shown in Fig. 6B. The weight of the prior art operator of Fig. 6A is approximately 300 pounds as compared to approximately 150 pounds for the operator shown in Fig. 6B. Both of these air motor assemblies develop enough force to close a 3" weir diaphragm valve with 300 psi line pressure at 0% pressure drop. The prior art arrangement of Fig. 6A employs a Model 32130 ITT Grinnell air motor while the present invention as shown in Fig. 6B employs a Model 3350 ITT Grinnell air motor.

It will be appreciated that the prior art diaphragm valve operator as shown in Fig.

6A is relatively heavy and the center of gravity is rather far above the diaphragm valve.

As can be seen from Figs. 6A and 6B, the spring S of Fig. 6A has been moved from the top of the air motor AM to a position between the diaphragm valve and the air motor AM of Fig. 6B, moving the center of gravity closer to the diaphragm valve. In order to transmit the horizontal spring motion of springs S of the present invention as shown in Fig. 6B into a vertical spindle movement, a pair of stacked link units is used as will be discussed hereinbelow with respect to the remaining Figures.

The same reference characters will be employed for the same components throughout the following description of the various embodiments of the mechanical force multiplier of the present invention.

Referring to Figs. 7 and 8, there is illustrated therein a diagrammatic view of an overall operator including an air motor 16 and the mechanical force multiplier disposed between air motor 16 and the controlled diaphragm valve 26. The arrangement illustrated in Figs. 7 and 8 is a reverse acting mechanical force multiplier which is built around a yoke. The yoke serves to support air motor 16, houses link units I and 2 and supports the stationary link pin 19. The yoke can be made as shown in Fig. 8 by using two side yoke plates 15 bolted to a top and bottom yoke plate 18 and 17 or by casting or forging the yoke as one piece. The yoke is attached to the bonnet 20 of the diaphragm valve housing using an adaptor bushing nut 21 and is attached to the air motor 16 in a similar manner. However, any other form of attachment of the yoke to the diaphragm valve bonnet and the air motor is possible, such as bolting or casting the yoke as an integral part of the bonnet and/or the lower air motor cover. The same yoke can be made to accommodate direct acting mechanical force multipliers also. Slots 27 in the yoke plate 1 5 are for valve spindle position indicators.

Springs 14 and 1 4a are sized depending upon the diaphragm valve size and line pressure. Springs 14 and 14a are in compression.

The spring retaining spindle 7 passes through the center of the inner and outer spring retaining plates 12, 12a and 13, 13a and restricts the springs by use of a nut against the spring outer plates 13 and 13a. This arrangement also provides spring force adjustment and balances the spring forces.

The spring inner plates 12 and 12a rest directly against link pivot pins 22 and 22a respectively. At pivot pins 22 and 22a the spring forces are transferred from the springs to the links.

The diaphragm spindle to link adaptor 5 is used to transmit force from the primary links to the diaphragm valve spindle.

The air motor link adaptor 4 is used to transmit the air motor force to the secondary links.

Referring to Figs. 9 and 10, there is illustrated therein one embodiment of a mechanical force multiplier that may be employed in the diaphragm valve operator of Figs. 8 and 9. The first or primary link unit 1 includes a first identical pair of spaced parallel link assemblies each having a link la having one end thereof pivotably connected to stationary point 19 adjacent adaptor 4, a link 1b having one end thereof pivotably connected to the other end of link la by pivot pin 22 and the other end thereof pivotably connected to adaptor 5 by pivot pin 31, a link 1d having one end thereof pivotably connected to stationary point 1 9a adjacent adaptor 4 and a link 1c having one end thereof pivotably connected to the other end of link id by pivot pin 22a and the other end thereof pivotably connected to adaptor 5 by pivot pin 33.

The secondary link unit 2 includes a second identical pair of spaced parallel link assemblies each having a link 2a having one end thereof pivotably connected to adaptor 4 by pivot pin 32 and the other end thereof pivotably connected to links la and 1b by pivot pin 22 and a link 2b having one end thereof pivotably connected to adaptor 4 by pivot pin 30 and the other end thereof pivotably connected to links lc and id by pivot pin 22a. The arrangement of the mechanical force multiplier just described is for a reverse acting mechanical force multiplier with the orientation of the various links illustrated in Figs. 9 and 10 being that orientation when the diaphragm valve is in a fully closed position.

Referring to Figs. 11 and 12, the mechanical force multiplier is that of Figs. 9 and 10, but with the diaphragm valve in a full open position.

The operation of the reverse acting mechanical force multiplier of Figs. 9 - 12 will now be described. In the closed position the reverse acting mechanical force multiplier appears as illustrated in Figs. 9 and 10.

Springs 14 and 14a of Fig. 7 act on the primary link unit 1 with minimum spring force.

However, the links are in a position where the force multiplying effect is a maximum thus, high force is delivered to the diaphragm spindle 6 of the diaphragm valve thereby closing this valve. To open the diaphragm valve the top chamber of the air motor 16 of Fig. 7 is pressurized. As the air motor spindle 3 moves down, the secondary link unit 2 push the pivot pins 22 and 22a outboard, compressing springs 14 and 14a of Fig. 7. The upper primary links la and id rotate on the stationary link pins 19 and 19a, respectively, thus the angle of the links of the primary link unit starts to decrease resulting in smaller force multiplying effects. However, springs 14 and 14a are being compressed so the resultant output force to the diaphragm of the diaphragm valve remains fairly constant.

During this time the links of the secondary unit 2 are moving from a low force multiplying effect to a higher force multiplying effect.

As the pivot pins 22 and 22a move outboard, the adaptor 5 is allowed to move up, opening the valve. Finally as a full open position, the links of the mechanical force multiplier are as shown in Figs. 11 and 12. The stationary points 19 and 19a have not moved. the air motor spindle 3 has moved down. The diaphragm spindle 6 has moved up. The springs 14 and 14a are in maximum compression.

To close the diapragm valve, air pressure is released from the air motor. The spring force moves the links of the mechanical force multiplier back to the position shown in Figs. 9 and 10.

Referring to Figs. 13,14, 15 and 16, there is illustrated diagrammatically the link configuration for a direct acting mechanical force multiplier. Figs. 13 and 14 illustrate this embodiment of the mechanical force multiplier in the diaphragm valve full open position, while Figs. 15 and 16 show the mechanical force multiplier in the diaphragm valve closed position.

The direct acting mechanical force multiplier is built around a yoke as is the reverse acting mechanical force multiplier as illustrated in Figs. 7 and 8. All aspects of the yoke pertaining to the reverse acting mechanical force multiplier of Figs. 7 - 12 also apply to the direct acting mechanical force multiplier of Figs. 13 - 16.

The springs 14 and 14a of Fig. 7 are sized depending on diaphragm valve size. The springs are in compression. The spring retaining spindles 7 as shown in Fig. 7 pass through the center of the inner and outer spring retaining plates 12, 12a and 13, 13a and are attached to the spring retaining spindle connector 9 as illustrated in Figs. 13 - 16.

Connector 9 is required to bridge the diaphragm valve spindle 6 which must pass through it. The spring retaining spindles 7 restrict the springs 14 and 1 4a by use of a nut against the spring outer plates 13 and 13a, provided spring force adjustment, and balances the spring forces from both springs.

The spring inner plates rest directly against pivot pins 22 and 22a. It is these pivot pins at which the spring forces are transferred directly to the links.

The valve diaphragm spindle to links adaptor 5 is used to transmit force from the primary links 1 to the diaphragm spindle 6.

Forces from the air motor to the air motor link adaptor 4 are transferred by means of an intermediate adaptor 11 and an air motor link adaptor to intermediate adaptor rods 8.

The forces are then transferred to the secondary link unit 2.

The first link unit includes link adaptor 5 having a force transferring relationship with diaphragm spindle 6 and a first identical pair of spaced parallel link assemblies. These link assemblies include a link la having one end thereof pivotably connected to one end of link adaptor 5 by pivot pin 34, a link 1b having one end thereof pivotably connected to the other end of link la by pivot pin 22 and the other end thereof pivotably connected to a stationary point 19 adjacent spindle 6, a link 1d having one end thereof pivotably connected to the other end of link adaptor 5 by pivot pin 35 and a link 1c having one end thereof pivotably connected to the other end of link 1d by pivot pin 22a and the other end thereof pivotably connected to a stationary point 1 9a adjacent spindle 6. The second link unit 2 includes a second identical pair of spaced parallel link assemblies each having a link 2a by pivot pin 31 and the other end thereof pivotably connected to links 1c and 1d by pivot pin 22a and a link 2b having one end thereof pivotably connected to adaptor 4 by pivot pin 33 and the other end thereof pivotably connected to links la and 1b by pivot pin 22.

The operation of the embodiment of the mechanical force multiplier of Figs. 13 - 16 are as follows. In the open position, the direct acting mechanical force multiplier appear ance is similar to the arrangement shown in Fig. 7. The springs 14 and 14a act on the primary or first link unit 1 to keep the diap hragm valve open. The primary link unit 1 at this point is in position where the force mul tiplying effect is at a maximum. To close the diaphragm valve, the bottom chamber of the air motor 16 is pressurized. As the air motor spindle 3 moves up, the secondary or second link unit 2 push pivot pins 22 and 22a out board, compressing the springs 14 and 14a as illustrated in Figs. 13 - 16. The lower links 1b and ic of the primary link unit 1 rotate out board about the stationary pivot pins 19 and 19a, respectively, thus the angle of the links of primary link unit 1 starts to decrease. As the links of primary unit 1 rotate outboard they pull down link adaptor 5, closing the diaphragm valve, moving from a high force multiplying effect to a smaller force multiply ing effect. During this time, the links of the second link unit 2 are moving from a low force multiplying effect to a higher force mul tiplying effect as adaptor 4 moves up. Finally, at a full closed position, the linkage of the two link units look as illustrated in Figs. 15 and 16. The stationary points 19 and 19a have not moved. The air motor spindle 3 has moved up. The diaphragm valve spindle 6 has moved down to close the diaphragm valve. The springs 14 and 14a of Fig. 7 are compressed to re-open the diaphragm valve.

To open the diaphragm valve, air pressure is released from the air motor 16. The forces of springs 14 and 14a move the links of the two link units back to the position as illus trated in Figs. 13 and 14.

As illustrated in Figs. 7 - 16 two springs 14 and 14a are used, one on each side of the mechanical force multiplier. It is possible to use only one spring. For instance, the spring retaining rod 7 could extend through spring plate 13, spring 14, inner spring plate 12 and inner spring plate 1 2a, omitting spring 14a and plate 13a. It should also be noted that spring plate 13a, spring 14a, retaining rod 7, inner spring plate 12a and inner spring plate 12 could be used by itself in place of the single spring arrangement just described.

In addition to the direct acting mechanical force multiplier as shown by the link configuration in Figs. 13 - 16, there are two other link configurations that can be used for direct acting mechanical force multipliers for controlling diaphragm valves.

The first configuration is illustrated in Figs. 17 - 20. As shown in Figs. 17 - 20, the link configuration of the link units of the mechanical force multiplier are the same as illustrated in Figs. 13 - 16. The difference between these two mechanical force multipliers is that the two springs mounted on the side, used to return the diaphragm valve to the open position, have been replaced by one spring 36 disposed between the top cover 37 and diaphragm 38 of air motor 16. Spring 36 is placed between the upper air motorcover 37 and the air motor diaphragm 38 so that spring 36 will always exert a force down on air motor spindle 3 forcing the diaphragm valve into the full open position. When air is supplied through port 39 in the lower chamber of air motor 16, the air motor force counteracts the spring force in addition to the force in the linkage of the two link units due to pressure in the diaphragm valve and closes the diaphragm valve.

The second alternative configuration is illustrated in Figs. 21 - 24. This direct acting mechanical force multiplier is similar to that illustrated in Figs. 17 - 20 in that the spring 36 is located between the upper air motor cover 37 and the air motor diaphragm 38 as illustrated in Fig. 17. However, as illustrated in Figs. 21 - 24 the reverse acting link configuration of the two link units 1 and 2 as illustrated in Figs. 9 - 12 is used as the linkage arrangement for the two link units 1 and 2 for this direct acting mechanical force multiplier.

Spring 36 in air motor 16 exerts a force down on air motor spindle 3 which forces the diaphragm valve into the open position. When air is supplied to air inlet 39 in the bottom chamber of air motor 16, the air motor force counteracts the spring force in addition to the force in the linkage of link units 1 and 2 due to pressure in the diaphragm valve and closes the diaphragm valve.

The advantage of using these two types of alternate forms of the mechanical force multiplier is basically that the number of parts required is reduced and the mechanical force multiplier will be easicr to assemble and less expcnsive.

The above alternative forms are practical on a direct acting mechanical force multiplier because of the relatively small force required to open the diaphragm valve against vacuum.

Throughout the description of the Figs. 7 24 the operator for the mechanical force multiplier has been referred to as an air motor. At this point, it should be noted that the mechanical force multiplier can be used with any type of operator that provides a linear motion or any motion that can be converted to a linear motion. Examples of such alternate operators are: (1) handwheel operator; (2) electric operator; (3) piston operator; and (4) in general, any type of operator that could be conceivably used with the mechanical force multiplier.

Any operator used will be mounted on top of the mechanical force multiplier unit as is the air motor as shown in Figs. 7 and 8.

As examples, primary link unit angles of 45" and 80" with respective force multipliers of 1 and 5.67 have been used throughout this description. It should be pointed out that these are only examples and any angle and associated force multiplier can be used for the primary link unit and secondary link unit.

WHAT WE CLAIM IS: 1. A mechanical force multiplier comprising: a first link unit having at least a first pair of links, each of said first pair of links hav

Claims

**WARNING** start of CLMS field may overlap end of DESC **. plate 13, spring 14, inner spring plate 12 and inner spring plate 1 2a, omitting spring 14a and plate 13a. It should also be noted that spring plate 13a, spring 14a, retaining rod 7, inner spring plate 12a and inner spring plate 12 could be used by itself in place of the single spring arrangement just described. In addition to the direct acting mechanical force multiplier as shown by the link configuration in Figs. 13 - 16, there are two other link configurations that can be used for direct acting mechanical force multipliers for controlling diaphragm valves. The first configuration is illustrated in Figs. 17 - 20. As shown in Figs. 17 - 20, the link configuration of the link units of the mechanical force multiplier are the same as illustrated in Figs. 13 - 16. The difference between these two mechanical force multipliers is that the two springs mounted on the side, used to return the diaphragm valve to the open position, have been replaced by one spring 36 disposed between the top cover 37 and diaphragm 38 of air motor 16. Spring 36 is placed between the upper air motorcover 37 and the air motor diaphragm 38 so that spring 36 will always exert a force down on air motor spindle 3 forcing the diaphragm valve into the full open position. When air is supplied through port 39 in the lower chamber of air motor 16, the air motor force counteracts the spring force in addition to the force in the linkage of the two link units due to pressure in the diaphragm valve and closes the diaphragm valve. The second alternative configuration is illustrated in Figs. 21 - 24. This direct acting mechanical force multiplier is similar to that illustrated in Figs. 17 - 20 in that the spring 36 is located between the upper air motor cover 37 and the air motor diaphragm 38 as illustrated in Fig. 17. However, as illustrated in Figs. 21 - 24 the reverse acting link configuration of the two link units 1 and 2 as illustrated in Figs. 9 - 12 is used as the linkage arrangement for the two link units 1 and 2 for this direct acting mechanical force multiplier. Spring 36 in air motor 16 exerts a force down on air motor spindle 3 which forces the diaphragm valve into the open position. When air is supplied to air inlet 39 in the bottom chamber of air motor 16, the air motor force counteracts the spring force in addition to the force in the linkage of link units 1 and 2 due to pressure in the diaphragm valve and closes the diaphragm valve. The advantage of using these two types of alternate forms of the mechanical force multiplier is basically that the number of parts required is reduced and the mechanical force multiplier will be easicr to assemble and less expcnsive. The above alternative forms are practical on a direct acting mechanical force multiplier because of the relatively small force required to open the diaphragm valve against vacuum. Throughout the description of the Figs. 7 24 the operator for the mechanical force multiplier has been referred to as an air motor. At this point, it should be noted that the mechanical force multiplier can be used with any type of operator that provides a linear motion or any motion that can be converted to a linear motion. Examples of such alternate operators are: (1) handwheel operator; (2) electric operator; (3) piston operator; and (4) in general, any type of operator that could be conceivably used with the mechanical force multiplier. Any operator used will be mounted on top of the mechanical force multiplier unit as is the air motor as shown in Figs. 7 and 8. As examples, primary link unit angles of 45" and 80" with respective force multipliers of 1 and 5.67 have been used throughout this description. It should be pointed out that these are only examples and any angle and associated force multiplier can be used for the primary link unit and secondary link unit. WHAT WE CLAIM IS:

1. A mechanical force multiplier comprising: a first link unit having at least a first pair of links, each of said first pair of links having one end thereof pivotably coupled to and in a force transferring relationship with one of an actuator and a device to be actuated and a second pair of links, each of said second pair of links having one end thereof pivotably connected to a stationary point and the other end thereof pivotably connected to the other end of an associated one of said first pair of links; a second link unit having at least a third pair of links, each of said third pair of links having one end thereof pivotably connected to said other end of an associated one of said first and second pair of links and the other end thereof pivotably coupled to and in a force transferring relationship with the other of said actuator and said device to be actuated; and at least one spring in a force transferring relationship with at least one of said first and second link units, said first, second and third pairs of links defining a volume and said spring being disposed outside of said volume with the force thereof directed from the outside of said volume toward the inside thereof, said first and second link units being disposed between said actuator and said device to be actuated, said first and second link units co-operating with each other and said spring to apply to said device to be actuated an output force which is larger than the input force from the actuator and which increases in proportion to the input force derived from said actuator when said actuator is actuated.

2. A multiplier according to claim 1, wherein said actuator and said device to be actuated are disposed coaxial of a common axis and said spring is disposed coaxial of an

axis normal to said common axis and said spring force is transferred at right angles to said common axis.

3. A multiplier according to claim 2, wherein two springs are diametrically disposed on opposite sides of said first and second link units and coaxial of said normal axis, said force of said two springs being directed toward each other in a force transferring relationship with at least one of said first and second link units.

4. A multiplier according to claim 1, wherein said actuator and said device to be actuated are disposed coaxial of a common axis and said spring is disposed coaxial of said common axis, said force of said spring being transferred parallel to said common axis.

5. A multiplier according to any one of claims 1 to 4, wherein said actuator force is directed toward said device to be actuated.

6. A multiplier according to any one of claims 1 to 4, wherein said actuator force is directed away from said device to be actuated.

7. An assembly consisting of an actuator, comprising an air motor, and a device to be actuated, comprising a diaphragm valve, interconnected by a mechanical force multiplier as claimed in any one of the preceding claims.

8. An assembly as claimed in claim 7 as appended to claim 4, wherein said spring is disposed in said motor coaxial of said common axis.

9. A mechanical force multiplier substantially as hereinbefore described with reference to and as illustrated in Figs. 9, 10, 11 and 12, or 13,14,15 and 16, or 17,18,19 and 20, or 21, 22, 23 and 24, of the accompanying drawings.

10. A valve operator unit substantially as hereinbefore described with reference to and as illustrated in Figs. 7 and 8 of the accompanying drawings