US2893721A - Dashpot mechanism - Google Patents

Description

July 7, 1959 E, E, HUPP l DAsHPoT MECHANISM Filed Dec. 27, 1956v 'INVENTOR y EDWARD E. HUPP.

UnitedStates Patent Q DAsHPoT i" The' present inventiri relates to' meansy for slowing motion in one direction; andV more'pa'rticularly to dashpot means particularly of the pneumatic type. An object of the present invention is the provision of new and improved ydashpot apparatus which is simple in design, eicient in itsv operation and inexpensive to manufacture. l l

Another object fof thinveition is the provision 4of new and improved kmotion dampening means for dash-. pot apparatus andthe like wherein a groove is provided in one end face, f a movable wall, the opposite ends of which groove communicate with opposite sides of said movable wall, and against which a membrane or cover member is vbiased to cause uid How between opposite sides of said movable wall to be throttled through the covered section ofsaidgroove.

:A further object of the invention is the provision of a new and improved cylinder and piston device one end face of which piston is provided witha groove opposite ends of which extend between opposite sides of said piston and which end face iscovered by a flexible membrame-the radially outer edges ofA which are in sliding sealing engagement withsaid cylinder and a radially inner portion of which overlies an intermediate portion of the groove, whereby iiow in one direction across said piston is throttledvthrough the intermediate section of said groove and flow in the opposite direction across said piston causes said membrane tobebiased out of sealing engagement with` said face of said piston.

'Ihe invention resides in certain constructions and combinations and arrangements of parts and further objects and advantages will become apparent to those skilled in the art to which the invention relates from the following description-of the preferred embodiment described with reference to the accompanying drawing forming a part of this specication, and in which:

- Figure;1 isafragmentary sideelevational View of a uid pressure servo-motor` embodying` principles of the present invention-and-inwhich sections are broken away toY better illustrate the features of the invention;

.A Figure 2 isan'endviewof a sealing membrane used inthe structure shown in Figure 1; and y Figure 3 is an'endview of the dashpot piston` shown infligurenl.' ,A K g, ,A

,The fluid pressure servo-motor shown in Figure 1 is offthe type4 shownand `described in detail in the Earl R. Price' applicationf41186, and now Patent Number 2,- 818,710. Thevservomotor generally comprises a cylinder' or power chamber enclosure A which is divided into opposing fluid pressure chambers by means of a movable wall or piston B. The piston B is actuated by means of ar control valve structure portions `of which are shown at C adapted to provide differential pressure across the pistonJ and .control valve'is' regulated by means of apush' rod D adapted to be controlled manually by an peraton 'Ifliepiston' B is s howriin a' position wherein itjis spacedjslighllyjnwardly (or to' theright of) its refract'edo'r left-hand o'ff travel. In the retracted .Y position of the piston,

l 2,893,721 Patented July 7v .1?59

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a nonmetallic washer engages the dared portion 12 of the end cover plate 14 of ythe enclosure A. a

The uid pressure servo-motors shown in the drawing have been used for the power actuation of hydraulic braking systems in automobiles; and atroblesome ing has been experienced 'hen the brakes are gui retracted to bring the disc 10 into sharp engagement with the end cover plate 14. A

This clicking of the piston B has been overorn y the embodiment shown in the drawing byarneans ,ofy dashpot arrangement E positioned on the end coverplate '14 of the servo-motor; and which dashpotdisadapteclhto gradually absorb the kinetic energyof the turning. piston, The dashpot E generally comprises a lluid pressure or cylinder housing and a movable wall or piston v22 adapted to be moved into the cylinder 20 bythe returning servo-motor piston B. The piston 22 isl providedgwith a headed portion having oppositely facing; `generally radially extending end surfaces-the innersunface24 of which is provided with an axially positioned cylindrical boss 26 Awhich projects inwardly into the iluid. pressure chamber 28 yformed by the cylinder enclosure 20. The inner face 24 of the piston 22 is provided witha general@ ly spirally shaped groove 30 one end of which proceeds axially along the side edge of the boss 26 and the other end of which proceeds outwardly along theradially outer edge of the piston 22 to provide flow communication between opposite sides of the piston. An annular. cover member 32 is provided for the inner facel 24 of :the piston and is adapted to overlie an intermediate' portion of the groove 30 such that flow communication lbetween gpposite sides of the piston will be throttled through the intermediate section of the groove 30. It will be seen that by this expedient throttling means of the conduit type is provided very inexpensively and eiiectively.`

, In the preferred embodiment shown in the drawing' the cover member 32 is formed from a relatively thin flexible annular membrane the radially outer edges of which' are biased into sliding sealing. engagement with the side walls of the cylinder 20. Inasrnuch as the piston 22 is forced inwardly into the chamber 20 to compress therein, the resulting increase in pressure within the chamber 2S biases the membrane 32 into irm sliding sealing engagement with the side walls of the cylinder 20. Pressure within the chamber 28 also biases? the membrane 32 up against the inner face 24 of the piston 22 to provide a seal therebetweenV andr limit flow com-V munication between opposite sides of the piston to tlie cross-sectional area of the groove 30. Rapid movement of the piston 22 outwardly o'f the chamber 20 (orftol the' right as shown in the drawing) will of course increase the pressure between the membrane 32 and theinner face 24 of the piston to force the membrane- 32""out7of'V sealing engagement with respect to both the inner face' 24 of the piston and the side walls of the ,cylind'erluj thereby permitting substantially unrestricted flowccmry munication across the piston in the reverse direction. The embodiment shown in the drawing further incorpo; rates a coil spring 34 one end of which is centered ,enf the closed end of the cylinder 20 and the oppositee'ndf of which abuts the membrane 32 adjacent its radially outer edge. Spring 34 therefore biases the membrane` 32 i'n sealing engagement with the sidewalls of the cylinde'ij 2t) and with the inner face 24 of the piston 22; and .at the same time urges the piston 22 into its outer posit The device operatesas followszmAnysuitable may be used to transfer movementof' the b serv mot piston B- to the piston 22 of the dashpot assembly T embodiment shown in the drawing' utilizes an' a extending projection36 on the piston 22v adapted the piston B a predeterminedA distance aheadof" its fully retracted position during its retractile stroke. Engagement of the projection 36 with the piston B thereafter forces the piston 22 inwardly into the chamber 28. Press ure is Ythereupon built up in the chamber 28 causing the membrane 32 to be held in firm sliding sealing engagement with the side walls of the cylinder 20; and at the same time forcing the membrance 32 into tirm engagement with the inner face 24 of the piston. Increased pressure within the chamber 28 causes air to flow into the groove 3l) adjacent the inwardly projecting boss 26 and to thereafter proceed through the tortuous path provided by the spiral groove *32 to the radially outer edge of the piston 22 where the groove proceeds axially rearwardly into communication with the opposite side of the piston. The pressure'within the chamber 28 will increase generally proportional to the speed at which the piston 22 is forced into the chamber 28 by the servo-motor piston B to provide anideal condition for gradually slowing down the servo-motor piston until it comes vinto easy engagement with the end closure 14 of the servo-motor cylinder A. It vwill be seen that the coil spring 34 not only biases the piston 22 into its outer position but holds the membrane 32 into engagement with the piston 22; such that substantially no lost motion is involved in bringing the membrane 32 into hrm sealing engagement with both the piston 22 and cylinder 20. It is a further very desirable feature of applicants invention that the piston 22 is free to move outwardly of the chamber 28 quickly at all times. Movement of the piston 22 to the right as seen in Figure l permits air from the right-hand side of piston 22 to flow past its radial outer edges (inasmuch as considerable clearance may be provided between the piston and cylinder in this construction) causing the radially outer edges of the membrane 32 to be bent inwardly out of sealing engagement with the side walls of the cylinder 2t). At the same time a pressure dierential will be created across the membrane 32 causing it to move out of hrm sealing engagement with the inner surface 24 of the piston. This permits air to flow radially inwardly between the membrane 32 and the face of the piston and thence past the boss 26 into the chamber 28. Fluid how through this latter path will not be required to follow the convolution ofthe groove 30 thereby greatly reducing the pressure drop in this reverse flow direction.

While the invention has been shown and described as embodied in a device wherein a movable wall is moved into an enclosure to increase the uid pressure therein it is not to be so limited. Presumably the same principles may be utilized in a device wherein the movable wall is moved outwardly of the enclosed chamber causing a decrease of pressure within the chamber and thereby a corresponding pressure drop across its piston. With such an arrangement the sealing membrane 32 and annular groove 30 could advantageously be placed on the opposite side of the piston from that shown in Figure l.

While the invention has been described in considerable detail I do not wish to be limited to the particular construction shown and described; and it is my intention to cover hereby all adaptations, modiiications, and uses thereof which come within the practice of those skilled in the art to which the invention relates.

I claim:

l. In a dashpot apparatus and the like: a housing having a variable volume uid pressure chamber; a movable wall for said variable volume chamber, said movable wall having a normal position in said fluid pressure chamber from which it is moved in a rst direction when retarding an externally applied force and during which movement a high fluid pressure lis applied to a first face of the movable wall and a lower fluid pressure is applied to the opposite face of the movable wall; said movable wall having a ow restricting groove in its tirst face subjected to the higher pressure which groove starts at one point on said face and extends to a second point on said face which communicates with said opposing face of said movable wall; a'cover member for said face in which said groove 4 v V is formed, said cover member overlying all but the beginning portion of said groove and being constructed and arranged to abut said first face when said movable wall is moved in said first direction and cause uid to flow through said groove', and means for biasing said movable wall toward its normal position, said means being positioned against said cover member to bias it against said A face of said movable wall.

2. In a dashpot apparatus and the likei a housing having a variable volume iluid pressure chamber; a movable wall for said variable volume chamber; said movable wall having a normal position in said Huid pressure chamber from which it-ismoved in a iirst direction when retarding an'externally applied force and during'which movement a high huid pressure is applied to a rst face of the movable wall and a lower fluid pressure is applied to the opposite face of the movable wall; said movable wall having a projection on said irst face and a tiow restricting groove which starts at one point `on the side of said projection and continues across said rst face to a second point on said face which communicates with said opposing face of said movable wall; a loose disk-shaped cover member for said face in which said groove is formed, said cover member being centered by said projection and overlying all but the beginning portion of said groove being constructed and arranged to abut said first face when said movable wall is moved in said first direction and cause fluid to flow through said groove; and means for' biasing said movable wall toward its normal position, said means being positioned against said cover member to bias it against said face of said movable wall.

3. In a dashpot apparatus and the like: a housing having a variable volume chamber; a piston forming one end of said variable volume chamber, said piston having a normal position from lwhich it is moved in a first direction when retarding an externally applied force and during which movement a high fluid pressure is applied to a first face of the piston and a lower pressure is applied to the opposite face-of the piston; said'piston having a how restricting groove in its iirst face subjected to the higher pressure which `groove starts atv one point on said face and extends to a second point on said face which communicates with said opposing face of said piston; a diskshaped cover member for said iirst face, said cover member being exible with its outer periphery being in sliding sealing engagement lwith the sidewalls of said chamber, said cover member overlying all but the portion of said groove adjacent said one point and being constructed andv arranged to abut said rst face and thereby cause fluid to flow through said groove when said piston is moved in said direction, and saidA cover member being ilexible enough to bend away from said side walls and permit uid flow therepastvwhen said piston is moved in the opposite direction. y y I y Y f 4. In a dashpot apparatus and the like: a housing having a variable volume chamber; a piston formingrone end wall of said variable volume chamber, said piston having a normal position from which it is moved in a direction decreasing the volume of said chamberwhen retarding an external force in said direction, said piston having a generally centrally located projection on its inside faceexposed to said chamber and a ow restricting groove which extends alongthe side of said projection across the face of said piston to a point on said face which communicates with the opposite side of said piston; a loose disk-shaped cover member for said inside face which cover member surrounds and is centered by'said projection, said cover member being shaped to overlie the portion extending across the face of said piston and not extend into the cross section of the groove in said projection; and a piston returned spring biasing said cover member against said one face of said piston; whereby said cover member abuts said piston and causes iluid to iiowlengthwise through Ysaid groove during inward movement of said pieve ,and Saidovsr member is loosely guided in a manner preventing a'complete closing oi':l of said groove in said projection.

5. ln a dashpot apparatus and the like, a housing having a variable volume chamber; a piston forming one end wall of said variable volume chamber, said piston having a normal position from which it is moved in a direction decreasing the volume of said chamber when retarding an external force in said direction, said piston having a generally centrally located projection on its inside face exposed to said chamber and a flow restricting groove which extends along the side of said projection across the face of said piston to a point on said face which communicates with the opposite side of said piston; a loose disk-shaped cover member for said inside face which cover member surrounds and is centered by said projection, said cover member being ilexible with its outer periphery being in sliding sealing engagement with the sidewalls of said chamber, said cover member overlying all but the portion of said groove in said projection and being constructed and arranged to abut said inside face and thereby cause fluid to ow through said groove when said piston is moved in said direction and a piston return spring biasing said cover member against said inside face of said piston.

6. In a dashpot apparatus and the like, a housing hav- L' ing a variable volume chamber; a piston forming one end wall of said variable volume chamber, said piston having a normal position from which it is moved in a rst direction decreasing the volume of said chamber when retarding an external force in said direction, said piston having a generally centrally located projection on its inside face exposed to said chamber and a ow restricting groove which extends along the side of said projection across the face of said piston to a point on said face which communicates with the opposite side of said piston; a loose disk-shaped cover member for said inside face which cover member surrounds and is centered by said projection, said cover member being exible with its outer periphery being in sliding sealing engagement with the sidewalls of said chamber; a piston return mechanism positioned against said cover member adjacent its outer periphery to bias it against said piston, said cover member being sutciently stiff that its resistance to bending biases its outer periphery in engagement with said sidewalls when pressure forces are not acting thereon but will bend away from said sidewalls during piston movement in the opposite direction.

References Cited in the le of this patent UNITED STATES PATENTS

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