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29, 1946. - ' J, sMlsKo I 2,410,132 LINE PRESSURE VALVE Filed April 20, 1944 awe/Mom ' JUHN Ema/‘m3 Fig-f3’ ‘1 , ' Patented Oct. ' flit“; 2.; A: ' ,n‘aisgj; ."Lmlilrn 2,410,132 A ESSUBE VALVE , . ' .Iohn, j’siiiiskiiil Q ‘vasiiingmi; D401.) assigns}, 5y‘ '3 ‘ _ inesnc assignments, tofl‘he B; FJGoodrich Coin; vents i Q .1 .~ rApplication 1,151.20, 1941, serial No. 5313991». ' (01. 188-152)‘ The present invention relates to improvements in‘ hydraulic brake systems,; beingwspeci?cally concerned with line pressure valve structures used in combination with the retracting means brake systems and the like" characterized by a for the brake shoes for controlling the brake shoe . the construction, combination and arrangement reduction in restriction to flow and accelerated closing at a predetermined pressure. clearance and rapidity ofbrake application. and release. , _, v : l' _ 3 ' '7 These and other objects and advantages re siding in the present invention, and pertaining to of parts will be more fully understood mm a consideration ofthe following speci?cation and v Line pressure valves of the type now inuse'in annexed claims. ‘ . - v p i, hydraulic brake systems are of;the> poppet con In the drawing, wherein. one form of the in struction. In practice it has been found thatthis 10 vention‘is illustrated in connection with its use type of valve builds up substantial resistance to in combination with hydraulic brake systems, ’ the return-?ow of oil from the actuating cylinder Fig. 1 is an end elevational .view of the valve, on the brake prior to closing and trapping a pre Fig.‘ 2 is across-sectional view taken on, line determined ?uid pressure in the brakes. 7-, The in of Fig. 1, and . f ’ _, ~ crease in restriction of the fluidrreturning from it) II-II _Fig. 3 is' a diagrammatical illustration» of the they actuating cylinder on, the. brake unduly pro line pressure valve in combination with a hy: longs brake release and the retracting action of 'draulic brake system. the brake. v , - v . 1 » In the illustrated form of the» invention, the - According to the present invention,_it is pro posed to substitute in lieu of ‘the poppet valve 20 valve H3 consistsof tWo cast portions l2 and J4. The section l2 has a chamber 15in which the heretofore used in combination with the hydrau piston 46 is supported for movement and urged lic brake system a valve whichis characterized downwardly, as viewed in_Fig. 2, by a spring l8 by the fact that its movement fromfully open to acting against the head of the piston J6 atone fully closed is exceptionally rapid, nptwithstande ing the fact that it is pressure -ac_tuated;,and~be¢ 25 end andagainst. the spring seat 20. at the opposite ‘end. 1 he. tension of the spring} I8 is’ regulated cause of this characteristic materially ,lleducesthe through, an adjustment bolt 22, ' actingv against time interval during braking application andthe the spring seat 20 and held in position of adjust reduction of line pressure within thegbgralgesgtov a predetermined value following brake release. “In construction and function ‘the preferred formpf valve is characterized by the fact'that the, pre loading of the valve'which determinestheg-hold ing pressure within the brake is counteracted by ment through the lock nut 24. x r _ Cast sections l2 and [4 have threaded engage ment at 26, and when tightly screwed together engage with the peripheral portion 28 of .the flexible diaphragmBDy ;, . _ In the illustrated embodiment the end of. the fluid pressure distributed , over a- relativelygjlarge piston I6 is shown ?at, as at 32, and when in the area with the pressure inthe brake inexcess of 35 position shown in Fig. 2 forces the diaphragm 30 the.predetermined-holding pressure.‘ .As the ‘pres against the complementary flat surface 34 of the sure ' drops withingthe brake, following‘ brake , re, casting l4 de?ned betweenthe port 36 and the lease, this large area is effective to hold the valve recess>39 concentric with the port 36 and into ‘substantially Wide open ,until .- the pressure has droppedjust short of the predetermined holding 40 which the connection38 communicates. To fa cilitate machining, the Y-surfaces32- and 34 are pressure, atwhich-time the diminishing ?owof preferably flat and parallel to each other, but it ‘fluid asdthe pressure drops e?ects a sudden redis will be understood that complementary surfaces tribution of the pressure" within. the valve from a other than'?at may be employed with similar relatively large area- to a, relatively‘small area, a thus accomplishinglan acceleration of thevalve Communicating with the port 316 is a connec as the line 'pressureapproaches the predeter tion 40 through which the valve may becon mined value and-provides the-desired- clearance nected tov the brake operating cylinder, as shown results. . .- ._ - l . between the brake shoes and the brake drum.- . in Fig. 3, through the‘line 42. The'connection Thusv one of the objects of the} present invene 38 couples the line 44 with the cylinder 46,,which tion is to provide an improved line pressurevalve 50 may contain a piston actuated from the brake in combination with the retracting means of 1 the pedal 48 or other conventional structure found in hydraulic brake systems, such as a control hydraulic brake. V g _ _~ -_ ~ ; .-~ I Another object is to provide in combination with a hydraulic brake system an improved, line valve and the like. value. A still further object of the invention is to pro ing mechanism usually in the form of springs, , ; - pressure valve for reducing the timeyintervalbef 5.5 »In operation the valve l0 is inserted in the hydraulic‘ System between the brake and the tween ‘brake __release and the reduction of the source of operating pressure. As it is well un holding pressure in the brakes to a predetermined derstood in the art, the brake shOe has retract which in the case of a radial brake, for example, vide an improved line pressure valve for hydraulic 60 3 2,410,132 tend to draw the brake shoe radially inward on brake release to provide clearance between the brake drum and the brake shoe. In a hydraulic brake system this retracting action of the brake shoe functions to force the hydraulic ?uid from the operating cylinder or its equivalent back' through the line'. The clearance between the . brake drum and the brake shoe can. be controlled by limiting the amount of brake .fluid_displaced from the brake actuating cylinder. This func-J 10 tion is performed by the line pressure valve In which may be adjusted to change the tensioning of the spring l8 to close the port 36 to maintain a predetermined pressure within the brake. As 4 tern having brake elements moved relative to each other on brake application and release, retract ing means for providing clearance between said elements upon brake release, a brake chamber having a movable wall actuating one of said ele ments and against which said retracting means reacts, a source of hydraulic pressure, and a con duit extending between said brake chamber and said source through'which a hydraulic ?uid ?ows toward the brake chamber upon brake applica tion and in the opposite direction toward said source upon brake release, a line pressure valve for maintaining a predetermined pressure in said chamber to regulate the clearance between said the brake shoe wears in service the clearance may 15 brake elements located in said conduit and char be adjusted by increasing the tension of the acterized by its rapid action reducing the interval spring I8 to provide the higher pressure necessary between brake release and the reduction to line to take up the additional clearance due to wear. pressure within the brake to a minimum, com The function just described with reference to the prising a movable-valve part of relatively large valve I0 is similarly performed by line pressure 20 area, a valve seat for said valve part, a port of valves now in use of the poppet type. relatively small area opening through said seat The improved’ performance of the valve [0 over and communicating with that portion of said con the poppet type, in the combination disclosed, is duit extending to said brake chamber, said mov due to its nonrestricting characteristics and ac able valve part having a face complementary to celerating. ability as the pressure within the brake 25 said seat and imposed over the entire area there approaches the predetermined holding pressure. of, means'continuously stressing said valve part ‘For the reason that the brake actuating pres toward-said seat to close said port to con?ne ?uid sure is substantially‘ greater than the holding under pressure in- said chamber, said valve part pressure, at the time of brake application hydrau having a large area as compared to the area of lic ?uid entering the valve l0 ‘through the con 30 said port subjected to hydraulic ‘pressure with nection‘ 38 readily displaces the diaphragm 30 and said valve part held open by pressure in said piston l6 ‘from ‘the surface 34>surrounding the brake chamber immediately following brake re port 36, with the result that ?uid freely ?ows lease, a second port communicating with that por through the valve I0 into the brake cylinder 50 tion of said conduit extending to said source, a through the line 42. The brake cylinder 50 common chamber into‘ which said ports open, a throughmembers 52 urge the brake shoes 54 out wall of - said common chamber being de?ned by wardly against the tension of the retracting said valve parts, ‘hydraulic pressure from said springs 56. The brake drum is indicated at 58. source acting against said. valve parts to move it Following brake release the high pressure in the from its seat-to enable ?uid to ?ow between said brake continues to hold the valve l0 fully open 40 ports, said‘ valve part in its closed position having as the hydraulic fluid returns through the line only a relatively small area subjected to the pres 42 and connection 46, and port 36, into the line sure in- said ‘brake chamber, whereby following 44. .In view of the large area of the diaphragm brake release said valve part is fully open except 30 and the piston l6, vthe pressure within the when pressure in said brake chamber has been brake experiences no diiliculty in resisting the ac reduced to» the predetermined line pressure at tion of the spring l8 and maintaining the valve which point the valve part rapidly closes against l0 fully open with the restriction to ?ow main ‘pressure distributed over only the area of said tained at a minimum. vThis condition exists ?rst port. throughout substantially the entire return ?ow 2. In combination with a hydraulic brake sys of the hydraulic ?uid from the brake even though 50 tem‘having brake elements moved relative to each the pressure in the brake is rapidly dropping and other on brake application and release, retracting the flow of- ?uid through the valve in is rapidly means forproviding clearance between said ele diminishing. This fully open condition of the ments upon-brake release, a ?uid motor actuating valve [0 and lack of restriction will maintain due one of said elements, a pressure source and a con; to the large area subjected to the pressure in the duitv for ?uid ?ow in communication with said brake until just short of the closing of the valve ?uid motor and said pressure source, a pressure H] to maintain the predetermined holding pres valve in‘ said conduit maintaining a pressure sure in the’ brake. The closing action results from higher than atmospheric between said pressure thediminishing flow of hydraulic ?uid through valve and said ?uid motor, said pressure valve the valve 10 and the decreasing pressure which 60 having a movable part of relatively large area, a permits the surfaces 32 and 34 to approachv each valve seat for said valve part, a port of relatively other, but still being separated so as to permit small area in said valve seat in communication the large area to be subjected to the'line pressure. with said ?uid motor, said movable valve part The pressure area is reduced to the area- of the having a face complementary to said valve seat, port 36 and the stress of the spring I8 is more 65 means for-stressing said valve part to said seat to than adequate to maintain the predetermined maintain pressure in said ?uid motor, a chamber pressure in the valve parts in the closed position eircumscribing said seat in communication with shown in Fig. 2. said movable valve part, and a port in said cir~ Having thus described my invention, what I cumscribing chamber communicating to said desire to secure by Letters Patent and claim is: 70 pressure source. 1. In combination with a hydraulic brake ‘sys JOHN SMISKO.