US3618473A - Multistage diaphragm vacuum servo - Google Patents

Abstract

A HOUSING CONTAINS TWO AXIALLY SPACED VACUUM ACTUATED FLEXIBLE DIAPHRAGMS EACH SPRING BIASED TOWARDS THE OTHER AND CONTROLLING MOVEMENT OF A FORCE TRANSMITTER SECURED TO ONE OF THE DIAPHRAGMS, THE SPRING ASSEMBLY BIASING THE ONE DIAPHRAGM INCLUDING TWO SPRINGS OF DIFFERENT PRELOADS AND A SPRING RETAINER THAT IS LOCATED BETWEEN THE TWO SPRINGS AND OF A CONSTRUCTION PROVIDING TWO STAGE OPERATIONAL MOVEMENT OF THE ONE DIAPHRAGM IN ONE DIREACTION IN RESPONSE TO VACUUM CHANGES.

Description

NOV. 9, 1971 G, R, M|| ER 3,618,473

MULTISTAGE DIAPHRAGM VACUUM SERVO Filed Feb. 2, 1970 VACUUM ,C v 6 INVENTOR GIR/M0 /M/Zfl? ATTORNEYS United' States Patent O 3,618,473 MULTISTAGE DIAPHRAGM VACUUM SERVO Gerald R. Miller, N orthville, Mich., assignor to Ford Motor Company, Dearborn, Mich. Filed Feb. 2, 1970, Ser. No. 7,490 Int. Cl. F01b 19/02 U.S. Cl. 92-48 2 Claims ABSTRACT OF THE DISCLOSURE A housing contains two axially spaced vacuum actuated flexible diaphragms each spring biased towards the other and controlling movement of a force transmitter secured to one of the diaphragms, the spring assembly biasing the one diaphragm including two springs of different preloads and a spring retainer that is located between the two sp-rings and of a construction providing two stage operational movement of the one diaphragm in one direction in response to vacuum changes.

This invention relates, in general, to a multistage fluid motor construction. More specifically, it relates to a dual diaphragm vacuum motor assembly in which one of the diaphragms moves in a plurality of stages.

This invention in particular is an improvement over the dual diaphragm fluid motor construciton of Ser. No. 858,567, Frank M. Kittredge, filed Sept. 11, 1969; As stated in the latter application, anti-smog regulations relating to internal combustion engine exhaust emission controls point out the desirability of selectively controlling the ignition timing at all engine speed and load conditions. This is not only to provide minimum engine exhaust hydrocarbon and other undesirable exhaust emissions, but good engine performance and economy as well.

The dual diaphragm actuator of Ser. No. 858,567 provides, among other things, normal engine ignition advance timing as a function of changes in carburetor spark port vacuum during part throttle engine operation. It does not, however, provide means for retarding the advance to permit operation of the engine at a fixed spark setting, for example. Operation at such a setting has been found beneficial in further reducing the output of unburned hydrocarbons and other undesirable elements.

This invention, therefore, provides a dual diaphragm fluid motor construction in which the ignition timing advance is capable of being modulated in a plurality of stages, and the primary diaphragm is spring loaded in a unique manner to provide the staging.

It is an object of the invention, therefore, to provide a multi-stage dual diaphragm vacuum motor actuator in which the movement of the actuator in one direction varies as a function of the changes in a plurality of sources of vacuum operatively acting on the actuator, and a plurality of spring forces.

It is another object of the inventionpto provide a dual diaphragm vacuum servo construction in which a plurality of preloaded springs bias one of the diaphragms in one direction in a manner causing multi-stage operation of the servo.

Other objects, features and advantages of the invention will become more apparent upon reference to the succeeding detailed description thereof, and to the drawings illustrating the preferred embodiment thereof, wherein;

FIG. 1"`is a cross sectional view of a vacuum servo mechanism embodying the invention; and

FIG. 2 graphically illustrates a typical travel movement of the actuator of the servo shown in FIG. 1 with changes in vacuum level.

Ser. No. 858,567 shows and describes an engine ignition timing systemof the type in which the present invention could be used. However, it will become apparent that it will have many other uses wherever a servo control of the type to be described is desired. Therefore, only the servo control per se will be described.

In general, the vacuum motor assembly 10` shown in FIG. l includes two flexible diaphragms 12 and 14 mounted in a housing 16 and defining separate vacuum chambers 18 and 20 to provide various control movements of an actuating rod 22. Chamber 20 is connected by a hose or line 24 to a first source of varying vacuum, such as, for example, the vacuum of an engine intake manifold. The other chamber 18 is connected 'by a hose or line 26 to a source of vacuum that alternates from an essentially zero level to a maximum.

No controls are shown for varying the vacuum levels in chambers 18 and 20l since they can be conventional, can be manually or automatically operated, and the details and operation thereof are believed to be unnecessary for an understanding of the invention. Furthermore, reference may be had to Ser. No. 858,567 describing one such system changing the vacuum levels.

More specifically, the vacuum motor housing 16 in cludes a bell-like, hollow, left hand portion 28, and a donut-shaped, right hand portion 30, vthe latter having a stepped diameter central opening 32. Axially between the two housing portions is a ring-like stop plate 34 contiguous to a ring-like stop plate 36. The latter has a stepped inner diameter 38 defining, with stop plate 34, an annular groove 40. Projecting into and axially movable within groove 40 is the bent edge 42 of a washer-like diaphragm retainer 44. The latter retainer, together with a semitoroidal shaped retainer 46, is clamped to the annular flexible diaphragm 14 having a central aperture 48.

The diaphragm 14 extends across the hollow interior of the housing and is sealingly mounted at its outer edge between stop plate 36 and the flange on housing portion 30. It is sealingly clamped against the housing at its inner edge. A spring 50 normally biases diaphragm 14 to the position shown locating flange edge 42 against the face of stop plate 34. The diaphragm, together with the Walls of housing portion 30, defines the fluid or vacuum chamber 20.

The second flexible annular diaphragm 12 is sealingly mounted between housing portion 28 and stop plate 34, and extends across the housing to define with it the fluid or vacuum chamber 18 connected to hose 26. The two housing portions and stop plates and diaphragms are fixedly secured together by means of an annular cap plate 54.

Rod 22, which, in the preferred installation, is a distributor advance plate actuating rod, is fixedly secured to diaphragm 12 by means of two cup-shaped plates 56 and 58. Movement of the diaphra-grn in either direction, therefore, will cause a corresponding pivotal movement of the conventional distributor advance plate (not shown). The radially outermost bent edge of plate 56 at times is adapted to abut the inner edge of the diaphragm stop plate 44 to limit movement of the (primary) diaphragm 12 in one direction, for a purpose to be described later.

A spring assembly identified as a whole as 62 normally biases the primary diaphragm 12 and rod 22 to the right to seat or abut edge 60 against plate 44. The spring assembly seats at one end against a combination spring seat and guide plug l64 that is threaded into housing 30. The plug also acts as an adjustable stop to limit movement of diaphragm 12 in a leftward direction, as will be explained more fully later.

As thus `far described, the construction is the same as shown and described in Ser. No. 858,567. Turning now to the invention, the spring assembly 62 is con- ACC structed in a manner providing dual stage operational movement of diaphragm 12 in a leftward direction.

More specifically, assembly 62 includes first and second axially aligned springs 66 and 68. The adjacent end of the springs seat against the sides of a ring-like flange 70 projecting radially from a spring retainer 72. The opposite end of spring7 66 seats against plug 64, while spring 68 seats against the lip flange 74` of a spring guide 76.

Guide 76, which can be of elastomeric or plastic material, comprises a sleeve having an internal annular boss 78. The latter defines a shoulder 80 in the stepped diameter internal periphery. On the other hand, the retainer 72 comprises a plastic sleeve having four (only three shown) fiexible finger-like portions 82. The fingers, in an assembled condition of the retainer and guide, extend laterally to a position inside sleeve 76. Each finger has a hook-like part 84 projecting radially from its outer periphery and adapted to cooperate with shoulder 80 constituting an axial stop.

In effect, boss 78 of sleeve 76 and parts 84 of retainer fingers 82 are interengaging portions axially slidably connected. To assemble, the fingers 82 are bent inwardly sufficient to clear the boss 78, inserted into sleeve 76 through the hole defined by boss 78 and then released. The resiliency of the fingers returns them to the shape shown. This prevents complete separation of the two while permitting a limited sliding movement between.

Intially, therefore, the preload of spring 68 separates retainer 72 from guide 76 a maximum distance, as shown. The preload of spring 66 maintains the retainer 72 and guide 76 against diaphragm retainer plate 58, and biases the diaphragm against stop plate 44.

The preload of primary spring 66 is chosen to be of a lower value than that of second spring 68, for a purpose that will become clear later. Also, the preloads of both springs 66 and 68 are lower than the preload of secondary diaphragm spring S0.

It will be clear that the preloads of the springs can be chosen to suit the particular results desired, as will be explained in connection with FIG. 2, for example. Also, varying the axial extent or position of the stops will change the characteristics of operation of the servo.

FIG. 2 illustrates `graphically typical changes in travel distance of rod 22 for changes in vacuum level from an initial setting. Assume, for example, the vacuum level in chambers 18 and 20 initially is zero, or at atmospheric pressure. In operation, therefore, with the preloads of the springs as described, the parts are positioned as shown. The preload of secondary spring `50 moves diaphragm 14 to the left and abuts edge 42 against stop plate 34 to provide an initial position of rod 22 at O in FIG. 2..

Assume now that vacuum is applied only to chamber 18. Until the preload of first spring 66 is overcome, an increase in vacuum produces no movement of rod 22. This is represented by the horizontal line OA in FIG. 2. Upon increase in vacuum, once the preload of spring `66 is overcome, retainer 72 and guide 74, diaphragm 12 and rod 22 then will begin moving to the left as a unit without compression of spring 68. Thus, as the vacuum in the primary chamber 18 increases, the rod 22 will move progressively between the points A and B in FIG. 2. The slope of the curve will be determined by the rate of spring `66. Point B represents the position of diaphragm 12 when the retainer 72 has bottomed against the end of plug 64. This ends the first stage of movement. Further increases in vacuum, therefore, produce no further leftward movement of the rod 22 until the preload of spring 68 is overcome. That is represented by the horizontal line BC in FIG. 2. Once this latter vacuum level is attained, the guide 76 begins moving axially on the fingers 82 by compressing spring 68. This is represented by the line CD in FIG. 2, the

l slope varying with the spring rate of spring 68. Finally, point D represents the end of stage two by the bottoming of guide 76 aginst retainer 72, which has previously bottomed against plug 64. Further increase in vacuum produces no further leftward movement of rod 22, as indicated by the horizontal line DE in FIG. 2.

The action is reversed, of course, during a decrease 1n vacuum.

The movement of rod 22 in a rightward direction is the same as is already fully described in Ser. No. 858,567. Therefore, only a brief description will be given. Assume, therefore, that there is no vacuum (atmospheric pressure) in chamber 18 and that we begin applying vacuum to chamber 20. Until the preload of secondary spring 50 is overcome, rod 22 will remain stationary. Again, this is represented by the horizontal distance OA in FIG. 2. As the vacuum increases above the preload of the spring, secondary diaphragm 14 will be drawn rightwardly until the flange 42 of plate 44 abuts stop plate 36. This is represented by the dotted line AF in FIG. 2. Further increases in vacuum, therefore, will not cause a further travel of rod 22, as indicated by the horizontal dotted line FG.

Assume now, therefore, that vacuum is applied in a controlled manner to both vacuum chambers 18 and 20 in a varying manner. It will be clear from a consideration of FIG. 2 that the two curves A-E and A-G can be combined to provide a varying slope curve (not shown).

Thus, from the above, it will be seen that by varying the levels of vacuum in the primary and secondary vacuum chambers 18 and 20 in a selective manner, and/or varying the preloads of the springs 50, 66 and 68, and/ or varying the spring rate of the springs and/or varying the axial locations of the stops and other adjustable changes previously described, that the curves shown in FIG. 2 can be made to assume substantially any number of shapes desired to provide a particular desired movement of rod 22 in either or both directions.

While the invention has been illustrated in its preferred embodiment in the drawings, it will be clear to those skilled in the arts in which it pertains that many changes and modifications may be made thereto without departing from the scope of the invention.

I claim:

1. A multistage fluid motor assembly comprising, a housing, a pair of flexible annular diaphragm members each mounted in said housing for an independent movement relative to the other and each with said housing defining a different vacuum chamber, means connecting each of said chambers to separate source of fiuid varying from a maximum essentially atmospheric pressure level to a minimum sub-atmospheric pressure or vacuum level for reciprocable movement of each of said members as a function of the changes in vacuum acting thereon, spring means biasing each of said diaphragm members towards the other, and movable force transmitting means operatively connected to one of the said pair of diaphragm members engaging at times with the other of said members upon movement of the said one ember in one direction for limiting the movement of the said one member in said one direction in a variable manner as a function of the position of the said other of said members, said one diaphragm member being `movable in the opposite direction as a function of the changes in vacuum in said chambers and the forces of said spring means, said spring means biasing said one diaphragm including first and second springs serially arranged, said first spring providing a lesser force then said second spring whereby said one diaphragm moves in stages as the vacuum forces successively overcome the different forces of said springs, said spring means biasing said one diaphragm including a spring retainer floatingly mounted between said rst and second springs, an increase in net vacuum force acting in the opposite direction on said one diaphragm to a level above the force exerted by said first spring progressively moving said retainer and force transmitting means in the said opposite direction at `a rate varying as a function of the spring rate of said rst spring, second seat means for the other end of said second spring, and means interconnecting said retainer and second seat means -for a limited relative movement therebetween, the force of said second spring initially biasing said retainer. and second seat means apart, an increase in the net actuating force on said one diaphragm above the force of said second spring moving said second seat means towards said retainer thereby permitting movement of said force transmitting means in the said opposite direction, said second seat means comprising a sleeve having an internal projection, said retainer having a springable, deformable finger with a hook-like portion slidable initially Linto said latter sleeve by springing of said portion over and past said projection thereby preventing disengagement of said sleeve and portion while permitting axial sliding movement therebetween.

2. A multistage fluid motor assembly comprising, a housing, a pair of tiexible annular diaphragm members each mounted in said housing for an independent movement relative to the other and each with said housing dening a different vacuum chamber, means connecting each of said chambers to a separate source of iluid varying from a maximum essentially atmospheric pressure level to a minimum sub-atmospheric pressure or vacuum level for reciprocable movement of each of said members as a function of the changes in vacuum acting thereon, spring means biasing each of said diaphragm members towards the other, and movable force transmitting means operatively connected to one of the said pair of diaphragm members engaging at times with the other of said members upon movement of the said one member in one direcvtion for limiting the movement of the said one member in said one direction in a variable manner as a function of the position of the said other of said members, said one diaphragm member being movable in the opposite' direction as a function of the changes in vacuum in said chambers and the forces of said spring means, said spring means biasing said one diaphragm including first and second springs serially arranged, said rst spring providing a lesser force than said second spring whereby said one diaphragm moves in stages as the vacuum forces successively overcome the different forces of said springs, said spring means biasing said one diaphragm including a spring retainer oatingly mounted between said rst and second springs, an increase in net vacuum force acting in the opposite direction on said one diaphragm to a level above the force exerted by said first spring progressively moving said retainer and force transmitting means in the said opposite direction at a rate varying as a function of the spring rate of said first spring, second seat means for the other end of said second spring, and means interconnecting said retainer and second seat means for a limited relative movement therebetween, the force of said second spring initially biasing said retainer and second seat means apart, an increase in the net actuating force on said one diaphragm above the force of said second spring moving said second seat means towards said retainer thereby permitting movement of said force transmitting Imeansin the opposite direction, said retainer having an axially extending portion that is flexible and the end of which is yieldingly movable in a lateral direction, said portion having a projection on the end extending radially outwardly, said second seat means comprising a stepped diameter sleeve defining an internal shoulder, said projection being sprung inwardly in response to movement into said sleeve past said shoulder and subsequently returned outwardly to its free state whereby separating movement of said sleeve and retainer is prevented and limited axial sliding -relative movement is permitted.

References Cited UNITED STATES PATENTS 2,379,306 6/1945 Larson et al. 92-130 X 3,082,792 3/ 1963 Jenkins 92-98 RD 3,385,275 5/ 1968 Burnia et al 92-64 UX 3,508,469 4/ 1970 Williams 92-63 MARTIN P. SCHWADRON, Primary Examiner I. C. COHEN, Assistant Examiner U.S. C1. X.R.

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