US2374011A - Fluid pressure actuated device - Google Patents

Description

April 5- R. GUNDERSON 2,374,011

FLUID PRESSURE ACTUATED DEVICE Filed Sept. 28, 1942 FlG.2.

INVENTOR.

RALPH R.GUNDERSON ATTORNEYS Patented Apr. 17, 1945 UNITED srATss- PATENT fol-"F1 The invention relates to fluid pressure actuated devices and refers more particularly to'fluid pressure actuated devices of that type having fluid receiving chambers of diflerent cross sectional pressure areas for exerting diflerent pressures.

f The invention has for some of its objects to.

provide an improved fluid pressure actuated device which is constructed to conserve the amount of fluid required to actuate the device and to increase the power output of the device during the second'stage 01' its actuation without requiring a fluid pressure greater than that at the end of the first stage of its actuation; to provide a fluid pressure actuated device inwhich fluid under pressure flows to but one fluid receiving chamber at a time and the fluid receiving chambers of smaller and larger pressure areas are successively operable; and to provide a fluid pressure actuated device in which a simple valve mechanism controls the fluid under pressure to but one chamber at a time.

The invention has for other objects to provide a fluid pressure actuated device so constructed that it is eilective in operation and may be economically manufactured; to provide a fluid pressure actuated device in which the fluid receiving chambers are formed by cylinders and a unit piston member and the unit piston member is slidably carried by the cylinders and normally held in predetermined relation to one of the cylinders; and to provide the piston member with a port intermediate its ends and passages extending through the pistons from the port'to the cylinders and'controlled by valves movable in unison.

These and other objects of the invention will become apparent from the following description, taken in connection with the accompanying drawing, in which Figure 1 is a diagrammatic elevation illustrating a structure employing a fluid pressure actuated device embodying the invention:

Figure 2 is a longitudinal central section through a fluid pressure actuated device Figures 3 and 4 are cross sections on the lines 3-3 and 4-4, respectively, of Figure 2.

The fluid pressure actuated device is designed particularly for use in brakes for motor vehicles. although it is apparent that the device may be used in other structures. As illustrated particularly in Figure 1, the device is employed in a brake which may be or standard construction. In detail, the brake comprises the rotatable brake drum I and the non-rotatable friction elements 2 and tengageable with the drum. The friction elen ndiug ends on the backing or carrier plate and operatively connected at their opposite ends to the device by means 01' which the opposite ends are spread apart and moved into engagement with the drum.

The fluid pressure actuated device comprises the opposed cylinders 4 and 5 oi-diil'erent diameters and the piston member 8 having the pistons I and 8 slidable within the cylinders 4 and 5, respectively, and forming therewith fluid receiving chambers of diflerent cross sectional pressure areas. The cylinder 4 is of smaller internal diameter than the cylinder I5 and is operatively conends of the piston nected to the brake shoe 2 by the pivot pin 9 which extends through the web of the shoe and the bifurcations ii on the closed end oi the cylinder. The cylinder 5 is similarly operatively connected to the shoe 3 by the the pivot pin II and the bifurcations I! on the closed end of the cylinder. The piston member 8 is a unit in which the pistons 'l and 8 are integral and at opposite member. 'The piston member has the port It intermediate its ends and adapted to be connected by suitable'tubing to the master cylinder of the motor vehicle. The piston member also has the separate passages l4 and I5 extending from the port II in opposite directions axially through the pistons l and 8 to the ends cylinders 4 and 5. respectively, i'or conducting fluid under pressure from the port to the chambers formed by the cylinders and their pistons. Suitable sealing means are providedbetween the pistons and their cylinders to prevent the escape oi the braking fluid which, in the present instance is a braking liquid. The sealing means, as shown, comprises sealing rings located in annular grooves in the pistons and slidably engaging the walls of the cylinders.

formed with the longitudinal flutes I 9 which provide for the flow of fluid past the valve when in ments are brake shoes pivotally mounted at correthe position shown in Figure 2. The valve is provided with thesealing ring 20 located in an anvalve and adapted to engage vided with the annular flange 2| at its outer end for engaging the end or the piston I to limit the movementoi the valve in an inward direction.

Th valve I8 is cup-shaped and has a cylindrical outer wall of greater diameter than the valve I1 and the diameter is such that the valve is slidable within an enlarged portion 22 of the passage It. The end part of the enlarged portion 22 of the passage 15 is formed with the longitudinal flutes 23 which provide for the flow of fluid past the valve when the sealing ring 28 of the valve is located over the flutes 23. In the position shown in Figure 2. the sealing ring 24 engages the solid part of the enlarged portion so that the valve 18 closes the passage IS. The valves I! and I8 are connected by the rod 28 so that the two valves move in unison. The rod is preferably integral with the valve l8 and extends from the bottom of its cup and is threaded into the valve H.

To normally hold the valve mechanism in a position such that the valve ll opens the passage 44 and the valve 18 closes the passage it, as shown in Figure 2, I have provided the coil spring 28 which at one end abuts the outer end of the valve I8 and at the other end abuts the stop 21 which rests against the split ring 28 seated in an interrupted annular groove formed in the land 29 between which the flutes 28 are formed.

80 is a compression coil spring within the cylinder 4 of smaller diameter and abutting its closed end and the outer end of the piston I for resiliently returning the cylinder and the piston member 6 to their all positions upon release of the pressure on the fluid. The arrangement is such that upon release of fluid pressure the cylinder 5 of larger diameter moves inwardly over the piston 8 until the closed end of the cylinder abuts the outer end of the piston so that the two arepredetermlnedly located with respect to each other. Since the cylinders 4 and 5 are carried by the brake shoes 2 and 3 and in turn carry the piston member, the adjustment of the brake by suitable means, such as eccentrics, to compensate for wear of the brake lining affects the position oi the cylinder 4 relative to the piston member 8 only.

For the purpose of permitting the fluid in the cylinder 5 to escape through the port l3 after the fluid pressure actuated device has been operated, I have provided the ports 3| extending through the bottom of the cup-shaped valve 18, the partition 32 having a central port therethrough and the valve 33 for controlling this port. The partition is fixedly secured within the annular wall of the cup-shaped valve l8 and the valve 33 is located between the partition and the bottom of the cup and has the stem 84 extending through the port in the partition. 35 is a compression coil spring encircling the stem and abutting at one end the partition and at the other end the collar 38 which is secured to the end of the ste the spring acting to resiliently hold the valve against the partition to close the port, but being yieldable during the return of the parts to their of! positions to permit the flow of fluid through the port from the cylinder 5.

In operation and with the parts in their oil positions, as shown in Figure 2, when fluid under pressure is forced through the port l3 and into the passages H and I5 it flows through the passage It only inasmuch as the valve I1 is in open position and the valve i8 is in closed position. Since the piston 8 abuts the closed outer end of the cylinder 5 and the coil spring exerts a predetermined pressure upon the valve mechanism I8 holding the valve I! open and the valve i8 closed, the fluid moves the cylinder 1 outwardposite ly along the piston I to spread apart the brake shoes 2 and 8 to take up all brake clearance and to move the brake shoes into engagement with the brake drum l. At this time the pressure of fluid in the cylinder 4, the passage I8 and the port l8 has reached a predetermined point such that the fluid acting on the larger diametered valve I8 collapses the coil spring 28 andmoves the valve mechanism. The sealing ring 28 of the valve I1 is located to pass completely over the flutes I8 and completely close the passage ll before the sealing ring 24 of the valve i8 moves of! the solid part of the enlarged portion 22 of the passage l5. As a result, fluid in the cylinder 3 is trapped before fluid flows to the cylinder 5 so that the cylinder 8 and the piston 5 act to hold the unit piston member 6 stationary with respect to the cylinder 4. Upon continued forcing of the fluidthrough the port l3, th unit valve mechanism continues to move until the sealing ring 24 of the valve l8 moves over the flutes 28 so that the fluid may flow into the cylinder 5 and cause this cylinder to move outwardly with respect to the piston 8, thereby compelling the brake shoes to more flrmly engage the brake drum. It will be noted that the stop 2| of the valve may act upon the outer end of the piston 7 to limit this movement of the valve mechanism, if necessary. Upon relieving the fluid from pressure, the parts will be returned to their oil positions by the coil springs 28 and 38 during which time the valve 33 will be moved to open position. As a result, the fluid within the cylinders 4 and. 5 is returned to the port i8 and then to the master cylinder. 4

It will be seen that the construction is such that fluid can be forced to but one cylinder at any time since the valve mechanism closes either the one or the other of the passages leading to the cylinders. It will also be seen that the construction is such that the cylinder of smaller diameter will be first moved outwardly with respect to the piston member and then the cylinder of larger diameter will be moved outwardly with respect to the piston member so that the fluid pressure actuated device functions to apply the brake shoes in two separate stages and with a greater force during the second stage without increasing the pressure of the fluid entering the device.

What I claim as my invention is:

1. A fluid pressure actuated device comprising a unit piston member having pistons of different diameters, a port and passages extending in opdirections from said port to the free ends of said pistons, cylinders within which said pistons are slidable, and valve mechanism for controlling said passages comprising a valve for controlling the passage extending to the free end of the piston of smaller diameter, said valve normally occupying an open position to place the cylinder with the port, said valve mechanism also comprising a second valve for controlling the passage extending to the free end of the piston of larger diameter, said second valve normally occupying a position closing said last mentioned passage, said valves being movable in unison and being relatively positioned so th'atsaid first mentioned valve is moved to closed position before said second valve is moved to open position.

2. A fluid pressure actuated device for actu-r ating friction elements, said device comprising a unit piston member having pistons at its ends of difierent diameters, a port between its ends of smaller diameter in communication.

and passages extending in opposite directions from said port to the free ends of said pistons, cylinders within which said pistons are slidable, said cylinders being operatively connected to the friction elements and carrying said unit piston member, and unit valve mechanism for controlling the flow of fluid through said passages, said unit valve mechanism being movable by the fluid to positions permitting the flow of fluid through said passages to One only of said cylinders at any time.

3. A fluid pressure actuated device comprising fluid receiving chambers of different cross-sectional pressure areas, separate ports for conducting fluid under pressure to each of said chambers; and unit valve mechanism normally opening the port to the chamber of smaller area and closing the port to the chamber of larger area, said unit valve mechanism moving successively, when the fluid attains a predetermined pressure, to positions which will first close the port to the chamber of smaller area, and subsequently open the port to the chamber of larger area.

4. A fluid pressure actuated device comprising fluid receiving chambers of different cross-sectional pressure areas, separate ports for conducting fluid under pressure to each of said chamhers, and unit valve mechanism for controllin the flow of fluid through said ports to both of said chambers, said unit valve mechanism being movable, when the fluid attains an increased predetermined pressure, to positions which will close the port to the chamber of smaller cross-sectional pressure area before opening the port to the chamber of larger cross-sectional area.

5. A fluid pressure. actuated device comprising fluid receiving chambers of different cross sectional pressure areas, different means for conducting fiuid under pressure to each of said chambers, and unit valve mechanism for controlling the flow of fluid through said conducting means to both of said chambers, said unit valve mechanism comprising a valve for closing each of said conducting means, and means dependent upon the pressure of the fluid for moving said valves in timed relation whereby either occupies a closed position before the other occupies an open position.

6. A fluid pressure actuated device comprising a unit piston member having pistons of different diameters at its opposite ends, a port intermediate its ends, and passages extending from said port through said pistons to the ends thereof, cylinders within which said pistons are slidable, and spring means between the piston of smaller diameter and its cylinder for resiliently urging the piston of larger diameter toward its cylinder.

'7. A fluid pressure actuated device for spreading apart a pair of brake shoes comprising opposed cylinders of difierent diameters operatively connected to said brake shoes, a unit piston member carried by said cylinders and having pistons at its opposite ends slidably extending within said cylinders, a port intermediate its ends and passages extending from said port through said pistons to said cylinders, a compression spring between the cylinder of smaller diameter and its piston for resiliently holding said piston member in predetermined relation to the cylinder of larger diameter, a unit valve mechanism comprising a valve for closing the passage leading to the cylinder of smaller diameter and a second valve for closing the passage leading to the cylinder of larger diameter, and a compression spring for resiliently holding said valve mechanism in a position with said first mentioned valve in open position and said second valve in closed position.

8. A fluid pressure actuated device for spreading apart a pair of brake shoes comprising opposed cylinders of diflerent diameters operatively connected to said brake shoes, a unit piston member carried by said cylinders and having pistons at its opmsite ends slidably extending within said cylinders, a port intermediate its ends and passages extending from said port through said pistons to said cylinders, a compression spring between the cylinder of smaller diameter and its piston for resiliently holding said piston member in predetermined relation to the cylinder of larger diameter, a unit valve mechanism comprising a valve for closing the passage leading to the cylinder of smaller diameter and a second valve for closing the passage leading to the cylinder of larger diameter, a compression spring for resiliently holding said valve mechanism in a posi- 40 tion with said first mentioned valve in open po sition and said second valve in closed position, and means comprising a valve movable to open position during the return of said cylinders and piston member to off positions to provide for escape of the fluid from the cylinder of larger diameter.

9. A fluid pressure actuated device comprising fluid receiving chambers of different cross sectional pressure areas, means for conducting fluid under pressure to each of said chambers, and unit valve means for controlling the flow of fluid through said conducting means to both of said chambers, said unit valve means being operable upon movement in one direction to trap the fluid in one of said chambers prior to permitting the flow of fluid to the other of said chambers.

RALPH R. GUNDERSON.

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