CA1037504A - Damper mechanism - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A damper for a lever mechanism wherein a lever beam is mounted for pivotal movement about a pivot axis.
The damper includes a rigid enclosure formed with a cavity having fluid contents therein, and a paddle extends through the opening and into the fluid. A flexible seal extends from the opening in the enclosure and supports the paddle in the fluid. The flexible seal functions as a variable pivot for controlling the pivotal movement of the paddle within the cavity. The arrangement is such that the damper enclosure can be fastened to a base of the lever mechanism and the free end of the paddle is attached to the lever mechanism so that the pivot axis of the lever mechanism extends through the flexible seal, wherein the paddle, in response to the movement of the lever mechanism, pivots about the pivot axis of the lever mechanism since the damper mechanism is a sealed unit, it can be used in any orientation. The mass of the paddle can be selected and the center of gravity located relative to the pivot axis so that a static balance of the lever mechanism can he achieved wherein the operation of the entire transducer is sensitive to position or orientation.

Description

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This inven~ion per~ains to damper mechanisms in general, and more particularly to pivotal damper mechanisms for lever systems .
This is a division of copending Canadian Patent Appli-cation Serial No. 217,80~, filed January 13, 1975.
In various types of control systems, lever mechanisms are used to provide a desired control function or conversion.
Such lever mechanisms are often found in electro-pneumatic transducers Eor converting electrical signals into pneumatic signals, or vice versa. Because of the low level signals involved and the desired degree of accuracy, the lever mechanisms in such control instruments are generally made of a light weight structure. However, the lever mechanisms are of a rugged construction so that the control instruments can be mounted at almost any appropriate location, such as for example on pipes, valves, etc. Quite o~ten, the control instruments are subject to a great deal of vibration, which in turn tends to create noise in the electrical and pneumatic signals involved. The ef~ect of the vibration, and the corresponding signal noise problems, can be reduced to an acceptable level by proper damping o~ the lever mechanisms.
- Because o~ the low level signals involved and the low mass of lever mechanisms, the damper is required to provide a low level type of damping function that will climinate problems ; due to vibration and th~e like but wlll not effect the desired `response of the instrument. In addition to the foregoing the control instruments are also often located in areas that ex-perience wide fluctuations in temperatures. A damper used with .:
the lever mechanisms should not, as a result of the temperature , kh~

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chan~3ec;, introcluce extraneous forces into the mechanisms that will oEEset the Eorce b~lance of the lever mechanisms and thereby introduce undesirable errors. In addition to the fore-going, because of the variety of potential applications, it is highly desirable that the damper includes a cons~ruction so that it can be positioned in any orientation without affecting the operation and balance of the control instruments.
Control instruments of this type often also include a span adjustment, a zero bias ad]ustment, and a nozzle alignment ~`
adjustment. An electro-pneumatic transducer of this type is ~ ;
disclosed in United States Patent No. 3,861,411, January 1, 1975, for Wayne D. Mitchell and Paul T. Met~ger, entitled "Electro- ~ -~
Pneumatic Transducer". With these various adjustments involved, the damper should not affect the setting o~ the adjustments, nor should the damping effect vary with changes of the adjustments.
In addition to the foregoing, it is highly desirable that the damper be of the type that is readlly connectable to the lever mechanism without the need for any adjustments thereby reducing the cost involved in the assembly of the transducers, or in-~0 volved in the replacement of the damper in the event of a failure.
It is therefore an object of this invention to provide a new and impr~ued pivo~al d2mping mechanism. ~ i It is also an object of this invention to provide a nev , and improved pivotal damping mechanism for lever mechanisms - , . ~:
and the like.
It is still a further object of this in~ention to provide a new and improved pivotal damping mechanism for connection to lever mechanisms and the like that does not effect the various span, zero bias, and nozzle adjustments ~,' ' ~.
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It is still a further object of this invention to provide a new and improved pivotal damper mechanism that can be used in any orientation.
According to the present invention there is provided a lever beam mounted for pivotal movement about a pivot axis and the damper for damping the pivotal movement of the lever beam, wherein the damper includes a rigia enclosure forme~
with a cavity and an opening into the cavity, a liquid being contained within the cavity. A paddle extends through the opening into the liquid in the cavity, and there is provided a flexible seal extending from the opening in the enclosure supporting the paddle in the liquid and providing a pivot point therefore so that the lever beam is secured to the paddle so that the pivotal axis of the lever beam corresponds to the pivot point of the paddle. Since the damper mechanism is a sealed unit, it can be used in any orientation. Therefore, in accordance with another feature oP the invention, the mass o~
the paddle can be selected and its center of gravity located relative to the pivot axis, so that a static balance of the lever mechanism can be achieved, wherein the operation of the er.tire trans~ucal- .s positior., or orientatlon, in~ellsitive. ~-BRIEF DESCRIPTION OF TME INVENTION:

Figure 1 is a top view of a damped lever mechanism including the invention.

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1~37~4 Figure 2 is a side view of the damped lever mechanism of Figure l.
Figure 3 is a sectional side viaw of the damper in the damped lever mechanism of Figures l and 2.
Figure 4 is a top view of the damper ofi Figure 3.
Figure 5 is another side view of a damper paddle in~
cluded within the damper mechanism of Figure 3.
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DETAILED DESCRIPTION OF THE INVENTION:
As illustrated in Figures l and 2, a lever beam 12 ` .
is mounted for pivotal movement about a pivot axis designated `~
by the dashed line 14. One end 16 of the lever mechanism can -' ~, `' .,;
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be coupl~d to an electromagnetic transducer, while th~ other end 18 can be coupled to a nozzle-bafEle arrangement, to ~unction as an electro~pneumatic transducer of the type disclosed in the above-mentioned United States Patent No. 3,861,411. An adjustable baffle mechanism 20 is provided for setting the opera-tion of the baffle-nozzle assembly as described in greater detail in the above-mentioned United States Patent No. 3,861,411. A zero bias ad-justment (not shown) can also be connected to the lever beam 12 to set the mechanism to a balanced position for a zero signal input condition. A zero bias adjustment is disclosed in the above-mentioned United States Patent ~o. 3,861,411 and also in United `
States Patent No. 3,895,543 issued on July 22, 1975, for Paul T.
Metzer and Wayne 0. Mitchell and entitled "Adjustment Mechanism".
The span adjustment ~or the lever mechanism can be provided by means of adjusting the position of the nozzle assembly relative -- to the baffle plate mechanism 20, as disclosed in the above-mentioned United States Patent No. 3,861,411 or by adjusting the ~ -electromagnetic transducer, as disclosed in a U.S. Patent 3,009,084, issued on November 14, 1961 to C.G. Ba]liett and entitled "Electro-mechanical Transducer". A damper 22, i.n accordance with the invention, is secured to the lever mechanism base 24 and the lever beam 12 in an arrangement wherein the damper does not effect any of the settings of the spani zero bias, and!or nozzle-baffle adjustments, is position or orientation insensitive in its operatiQn and does not need any adjustments to conform with the pivotal move-ment of the lever beam 12.
The lever beam 12 is mounted to the base ~4 by a "C"
shaped bracket 26, the screws 30, and a pair o~ leaf spring assem-blies 34. The bracket 26 and the leaf spring assemblies 34 are ..
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].ocntcd on op~ e s:Lcle~; oE the damller 22. A pa:ir of projectlons 38 a~d 40 cxtend from ~he lcver heam 12. The projectlons 38 and 40 lnclude A leg ~2 and ~ foot 46 extcnding generally normal to each other. The bracket 26 has generally S-shaped ends wlth `~
portlons 50 and 52 thereof lying parallel to their respective extenslon foot 46. In addition, the bracket 26 includes t~70 ~abs 54 that extend therefrom through the base 24 to serve as an alignment means for mounting the damper 22 as will be discussed in greater detail in a later portion of the speclfication. Each ~0 of the spring assemblies 34 are formed of two leaf springs 56 and 58 that are disposed generally normal to each other. The foot 46 of each lever projection 38 and 40 is secured to the respective bracket portion 50 via the leaf spring 56. The leg 42 of each ex-tension 38 and 40 is secured to the respective tab 54 of the bracket .
26 via the leaf spring 58. The points at which $he leaf springs 56 and 58 cross define the pivot axis of the lever beam 12. The pivot axis 14 extends through the cross-over points of ~he springs 56 and 58 of both the spring assemblies 34. The pivotal mounting of the lever beam 12 is disclosed in greater detail in the above-mentioned United States Paten~ No. 3,861,411.
As illustrated in Figure 4, the damper 22 includes a flat ba8e 60 that is formed with a pair of aperatures 62 and a pair of slots 64 extending through the base 60. When mounting the damper 22 to the base 24, the slots 64 align with the tabs 54 of the bracket 26. A pair of screws 66 extend through the aperature~
62 and secure the damper 22 to the base 24. A pivotal paddle or post 70, in the damper 22 is secured to the lever beam 12 by the use of a screw 72 that extends through a washer 74 and a collar 76 into a threaded aperature 78 formed ~()3~75~4 in the end o~' the paddle 70. ~I'he damper 22 includes an elongated rigid housing 80 formed with an elongated cavi-ty 82 having a cylindrical shaped section 81 wi-th an opening, and a converging closed section 83 all of which is filled with a fluid 84, such as for example a silicone liquid. A flexible seal 86 extends between the opening to the cavity 82 and the paddle 70 in an arrangement wherein a fluid tight seal is provided between the enclosure 80 and the paddle 70. The end 87 of the flexible seal fits with the annular recess in the base 60 adjacent the cavity opening and is cemented thereto. The end 89 of the flexible seal fits within a groove formed in the paddle 70.
The groove 88 has a diame-ter that is slightly larger than the underformed diameter of the flexible seal 89 that engages the groove 88. When assembled, as illustrated, the flexible seal 89 forms a compression seal with the groove 88. The lever beam 12 is formed with a rectangular shaped aperature (not shown) having the same conf:iguration as the top of the paddle 70 (as viewed in Figure 4). The compression type seal between the flexible seal 89 and the groove 88 provides a slip type fitting that allow the rotational movement of the paddle 70 (relative to the flexible seal 89) for aligning the paddle top 78 relative to -the aperature ;~
in the lever beam. The portion of the damper 22 between the paddle 70 and the flexible seal 86 is also filled with the silicone liquid leaving no air or voids inside the damper assembly. As a result, the paddle 70 is continuously immersed in the silicone fluid and therefor the damping effect of the damper 22 is insensitive to its position or orientation. ''~

30 The flexible seal 86 provides a variable pivot point for ~ ' the damper 22 and also provides means for allowing for the expansion and contraction of the silicone fluid within the ~3~5~4 damper 22 due to temperat-lre changes. [`he paddle 70 includes a cylindric~l portion 90 and a wedge shape portion 92 extending -therefrom wherein the width of -the paddle (as viewed in Figure 5) subs-tantially less than the length, and -the thickness of the wedge shaped portion 92 at the end of the paddle is substantially less than the width to optimize the damping action of the motion indicated by the arrows 94.
When the damper 22 is secured to the lever mechanism, the damper, through -the use o~ the flexible seal 86, automatically assumes a pivot point that lies along the pivot axis 14.
In the arrangement illustrated on Figure 1 and 2, the pivot point assumed by the damper 22 will lie within the circle 93 of Figure 3. In response to a force applied to the paddle 70 in the direction of` the arrows 94, the paddle 70 pivots within the the limits of the cavity 82. The silicone fluid resists the pivotal movement of the paddle 70 to provide the damping function. It should be noted, forces due to temperature are symetrically developed about the center :line 98 of the paddle 70 with a resultant f`orce on -the center :line that passes through the pivot axis 14. As a result, a moment summation of these forces about -the pivot axis 14 is theoretically :: , zero and therefore changes in temperature and the resulting : ~:
expansion and contraction of the fluid will leave no appreciable effect on force balance operation of the lever mechanism.
The mass of the paddle 70 is selected, and its center gravity located relative to -the pivot point 93, so -that a static balance is achieved between the portion of damper paddle 70 that extends on one side of the pivot ; ~ .
axis 14 and the mass of the lever mechanism (such as the . :

baffle mechanism 20 and the moving coil mechanism of .
an electromagnetic transducer) that ex-tends on the other ~ ~
side of the pivot axis 14. A static balance is continuously ~ .

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~3~S~J4 mairltclinecl regardless of the orientation of` the lever mechanism making the mechanis~ position insensitive (ie can be opera-ted in any orientation without an noticeable detrimental affect). Hence, the control instrument includin~ the damped lever mechanism can be usually repositioned without any further readjustment of its operation.
The combination of the elongated paddle 70, the cavity 82 within the housing 80, and the flexible seal 86 supporting the paddle 70 within the fluid in the cavity 82, provides a damper arrangement that can be secured to a lever mechanism so that the flexible seal 86 is positioned within the pivot axis wherein the damper 22 automatically assumes the pivot axis of the lever mechanism as its pivo-t point. ~ith this type of arrangement, there is no need to align the pivot of the damper with the pivot o~ the lever mechanism. The pivot of the damper will conform to the particttlar design of the lever mechanism without any adjustment. Because of the sealed structure of the damper 22, the damper can be used in any orientation. In addition to the foregoing, since the damper 22 accepts the pivot point of the lever beam 12, it does not effect any of the span, zero bias, and/or nozzle-baffle adjustment. ~;
The static balance provided by the damper 22 allows the lever mechanism to be used in any orientation. The damper 22, in the case of failure, can be simply replaced with another ;
unit without the necessity of readjusting the operation of ;~
the transducer. Furthermore, since the moment of summation of forces on the paddle 70 due to temperature changes approaches zero, the damper does not upset the force balance arrangement of the lever mechanism. It was found, that the damper 22, of the invention, provided an adequa-te damping effect on `~

the disclosed lever mechanism to eliminate noise problems ~375~)4 due to vibration and the like, and WEIS effective over the wide range O-r temperature vara:tions (-40 F to +200 F) without materially upset-ting the force balan~e of the lever mechanism. ~ ~

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Claims (2)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A damper lever mechanism comprising:
a lever beam mounted for pivotal movement about a pivotal axis, and a damper for damping the pivotal movement of the lever beam, said damper including a rigid enclosure formed with a cavity and an opening into the cavity;
a liquid contained within the cavity;
a paddle extending through the opening into the liquid in the cavity, and a flexible seal extending from the opening in said enclosure supporting said paddle in said liquid, and providing a pivot point therefore, wherein said lever beam is secured to the paddle so that the pivotal axis of the lever beam corresponds to the pivot point of said paddle.

2. A mechanism as defined in claim 1 where the mass of said paddle and the center of gravity of the paddle relative to said pivotal axis provides a static balance for the lever beam.