US2197125A - Thermostatically controlled means for rotating packing cups - Google Patents

Description

' April 1s, 1940.

THERIOSTATICALLY Apl 16, 1940.

THERMO STAT I CALLY Patented Apr. 16, 1940 PATENT or-FICE THERMOSTATICALLY CONTROLLED MEANS C FOR,Av ROTATING PACKING CUPS John o. Cox, st. Louis,

Mo., assignor to Wagner Electric Corporation, St. Louis, Mo., a corpora- Vtion of Delaware Application February 19, 1938, Serial No. 191,460

14 Claims.

My invention relates to iluid compressors and more .particularly to uid compressors of the compensating ,type which are employed, for example, in hydraulically actuated brakes.

These compressors (commonly referred to as master cylinders) employ a packing cup for sealing the piston and in the form now in use in braking apparatus a porthole places the po-rtion of the cylinder ahead of the piston in communication with a reservoir when the piston is in retracted position, whereby contraction and expansion of the fluid in the braking system due to temperature changes will not cause decrease or increase of pressure in, the system.

When the piston is initially operated, a fluid pressure is developed in the cylinder ahead of the pist'on and packing cup and as the forward edge of the lip of the cup becomes partially positloned over the porthole, the lip will be forced sulciently into the hole that the forward edge of the cup will rub on the forward edge of the hole as the cup is moved forward. Since in apparatus now in` commercial use the same portion of a cup may pass over the porthole on many successive protractile strokes of the piston, a chafing or cutting of the cup frequently results, thus reducing the length of its effective service.

It is the object of my invention to provide thermostatically controlled means subject to the varying temperature of the fluid in the compressor for intermittently rotating the packing cup whereby the same portion thereof will not pass the porthole on all successive strokes of the piston, thus distributing the wearing action of the porthole over the periphery of the cup instead oi' permitting it tobe concentrated at one point. Y

[Other objects of my invention will become apparent from the following description taken in connection ywith the accompanying' drawings 40 showing two embodiments thereof. Figure 1 is a. longitudinal cross-sectional view, partly in elevation, of a compressor embodying my invention, said figure also diagrammatically showing a brake mechanism as an example of apparatus which may be actuatedthereby; Figure 2 is an enlarged, cross-sectional view of the thermostatically controlled rotating means; Figure 3 is 'a cross-sectional view taken on the line 3 3 of 'Figure 1; Figure 4 is a longitudinal cross-sectional view of Aa modiiication; and Figure 5 is a cross-sectional view. taken on the line 5 5 of Figure 4.

Referring to Figures 1, 2 and 3 in detail, numeralv I indicates the cylinder in which is re- (Cl. Sii-54.6)

` ciprocable a piston 2 having a head 3, a rear ange 4, and an intermediate reduced cylindrical portion 5. Above the cylinder is a reservoir 'Ii cast integral with the cylinder and containing a reserve supply of uid. 'I'he rear portion 4` of the piston engages a stop 'I to predetermine itsu inoperative position to which it is normally biased by a spring 8 interposed between the head of the piston and the forward end of the cylinder. The rear end of the cylinder adjacentA the portion 4 is provided with an annular packing cup 9 to prevent leakage of fluid from the space surrounding the reduced cylindrical portion 5.

The head 3 of the pton has associated therewith a packing cup III for preventing iluid from passing the piston head on the protractile stroke of the piston. The piston and cup, however, are so constructed that uid may pass the lip of the cup during the retractile stroke of the piston and to facilitate this, the piston head 3 is formed with a plurality of passages II adjacent its periphery. When the piston is in retracted position, as shown in Figure l, a compensating porthole I2 places the reservoir in communication with the portion of the cylinder ahead of the piston and the packing cup. A passageway I3 is valso provided between the reservoir and the portion of the cylinder at the rear of the head of the piston in order that the space surrounding the reduced cylindrical portion 5 of the piston mayalways be iilled with fluid.

The forward end of the cylinder is provided with a two-way valve structure I4 of known construction for controlling the ow of iiuid to and from the cylinder. The dome part of the valve structure is wedged into the end .of the spring 8 to prevent relative rotation between'these mem-4 bers and the valve structure is yprevented from rotating relatively to the cylinder by a projection 50 cooperating with a slot 5I in a guide ring 52. The cylinder is connected by a suitable conduit I5 to the conduits I6 leading to the actuating cylinders `I1 of the brake assemblies i8 (only two being diagrammatically shown). The piston 2 is actuated by a pistonl rod I9 `which may becontrolled by a pedal (not shown) in the usual manner. v

With the structure just described, when the piston is moved forward, the compensating porthole I2 will first be cut oif and then fluid under pressure will be forced through'the` holes 20 of the two-way valve device. and into the brake line. When the piston is allowed to retract; iluid will be forced back through the brake lines into the' bythe action of the return springs of the brake assemblies, the two-way valve structure unseating against the action of springt to In accordance with my invention, l provide thermostatically controlled means for rotatingv the packing cup relative to' the cylinder wall,

thus preventing the same portion of the lip of the cup from passing over the porthole on all successive strokes of the piston. 'Ihe head 3 of the Vpiston is provided with a plurality of recesses 2l .and the rear surface of the packing cup' iii is formed with a like number of projections 22 which are adapted to snugly t into the vrecesses, thus so connecting the cup and the piston lthat the two will. rotate together. face of the cup has secured thereto a member- The forward 23 by means of prongs 24. The central part of the member is formed with a square portion 25 having a'conical tip and cooperating with member 23 is a cup-shaped member 28 having a recess for mounting on ,the conical tip of portion 25 where it isheld by spring 8. 'Ihe cup-shaped member 26 is so constructed as to wedge linto the end coil of spring 3 vso that relative rotative movement between these two members is prevented.. The inner cylindrical surface of theV cup-shaped member 23 is formed with/I' a plurality of teeth 21v and mounted on the square portion 25 of member 23 is a spiral-shaped tem perature sensitive element 28 of the bimetallic Y type provided'with a detent end 23 for cooperation with teeth 21.

The fluid in the'cylinder surrounds the element 28. and this fluid is subjected -to the changes in temperature due to atmospheric changes and also the changes in temperature due to the operation of the brake assembly since the uid motors l1 are adjacent the brake drum. As the temperature ,01 the uid rises, the spiral temperature sensitive.element 28 will tend to wind up in a clockwise direction, as seen in Figure 3, and since the detent end engages teeth 2l,- the resulting effect will be to cause member 23,to rotate relative to the cup-shaped`xnember 23 as the latter member is held against rotation by the action of spring 8 in a manner already described. Since member 23 is secured to the cup, the cup will, therefore, be rotated relative to the cylinder wall, thus placing a dierent portion of the lip of the cup in position for`movement over the compensating port. The rotation of the packing cup will generally take place after the cup becomes positioned rearwardly of the compensating porthole since at this time there is no uid pressure acting on the lip of the cup to hold it in tight frictional engagement with the cylinder wall. At this time spring 8 is exerting a minimum retracting force on the piston. Consequently, the wearing" on the cup will not all take'place at one point but will be distributed about the peripheryof -the cup, thereby p longing the life of the cup.

' When' the ui'd in the cylinder cools, the spiral element will tend to "unwind but since the deaievnao Y tent end is free m -move over teeth -21 m this direction of movement. no relative movement will tak e. .place between members 23 and 23. The tentefwill thus be placed .in cooperative relation termittently rotated, the intervals at/which such rotation takes place depending upon the time aridextent of changes in the temperature of the il Referring to the modification shown in Figures 4 and 5, the piston head 3' is formed with a cylindrical recess 30 in which is press-fitted a cylindrical ring 3|A provided with teeth 32 on its inner surface. 'Ihe forward edge of recess 3 0 is beveled fgr cooperation with a disk `v 33 havv ,ing an annular beveled'surface 34.

When the two beveled surfaces are in contact, the for- 7.a. different tooth for turning the packing y cup when the temperature of the fluid agair i`n creases. It is thus sen that the cup will be in` ward end of passages extending through the 1 piston head will be closed, thus preventing fluid from flowingffrom the rear of the' head of the piston to the portion of the cylinder ahead of the piston. The disk 33 has secured thereto two of the piston head and mounted on these pinsis a temperature sensitive element in the form of an 8-shaped bimetallic element 38 (Figure 5). One end of the bimetallic element is formed pins 36 and3'l which project into the recess 30 L with a detent '39 for cooperation with' teeth 32 for preventing the disk from rotating in ya counter-clockwise direction (Figure 5) andA the other end of the element is provided with a detent 40 for cooperation with teeth 32`for pre'- venting I:this end from also moving in a counter-' i clockwise direction.

The piston packing. cup 4I has formed on'its rear surface a plurality of projections 42 which oproject into holes 43 in the forward surface of disk 33, thus connecting4 the disk and cup for rotation as a unit. The forward surface ofthe cup cooperates with a bearing plate 44 having a central protuberance 45 for receiving the recessed portion of a member 43 engaged by the end of spring 8 which returns the piston to its normally inoperative'position. 'Ihe piston 2 is held against rotation by providing the end of the piston rod I3 with a prong C4'l for engagement in a slot 48 in the piston.`

In the structure just described, 1r there, is a rise in temperature of the-iluidvin the cylinder, the U portion of the bimetallic element 38 will tend to "open up but since detent 40 cannot move because it engages one of the teeth2'1, the result will be a clockwise rotation of disk 33 relative to piston 2. Under these conditions, detent 39 will slide over teeth 32. A As the cup is secured to the disk, it will-be rotated relative to the cylinder wall, thus presenting a different portion of the periphery of the cup for movement past the compensating porthole I2 when the piston is moved forward. When the temperature of the fluid decreases, -detent end 40 of the thermostatic element will be moved toward the portionsupported by pins 36 and 3l and since detent 33 will not permit the disk to mmfe counter-clockwise, detent 40 will be drawn over one or more of teeth 32 depending upon the amount of decrease in temperature.` l A If during theretractile stroke of the piston there is a tendencyo for a subatmospheric pressure to become established ahead of the cup, fluid will be free to ow through the piston head passagesf35, past disk 33 and the periphery. of the cup since, under these conditions, the cooperating beveled surfaces ofdisk 33 and the piston head will move sufficiently apart to per- @out` departing from the fundamental principles of my invention, I do not intend that its scope be limited except as set forth by the appended claims.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In apparatus of the class described; a cylinder, a piston lreciprocable in said cylinder, a packing cup for the head of the piston, and thermostatically controlled means for rotating the cup relative to the cylinder wall.

2. In apparatus of the class described, a cylinder, a piston reciprocable in said cylinder; a packing cup for the head of the piston, and thermostatically controlled vratchet means for intermittently rotating the cup relative to the cylinder wall. 0

3. In apparatus of the class described, a cylinder, a piston reciprocable in said cylinder, a packing cup for the head of the piston, and

vtlierrnostatically controlled 4means cooperating with the cup and the piston for rotating the cup relative to the cylinder wall.

4. In apparatus of the class described, a cylinder, a piston reciprocable in saidcylinder, a packing cup associated with the head of the piston, a iiuid` reservoir, means including a passage in the cylinder wall and positioned ahead ofa, the cup when the piston is in retracted position for permitting communication between the cylinder and reservoir, and thermostatically controlled means for rotating the packing cup relative to I the cylinder wall when the cup assumes a posi- L,tion rearwardly of the passage whereby the vsame portion of the cup will not move past the vopen end of the pe on all successive strokes of the piston. l 5. In apparatus of the class described, a cylinder, a-piston reciprocable in said cylinder, a

inder, a piston reciprocable in said cylinder, a

packing cup associated with the head of the plston, a uid reservoir, means including a passage in the cylinder wall and positioned ahead of the cup when the piston is in retracted position for permitting communication between the cylinder and reservoir, a member secured against rotation, and ratchet means associated with the member and the cup for rotating the cupv relative to the cylinder wall when the cup assumes a position rearwardly of the passage whereby the same yportion thereof will not pass the end of the passage 'on all successive protractile strokes of the piston, said ratchet means including a thermostatically controlled detent.

'1. In apparatus of the class described, a cylinder, a piston reciprocable in said cylinder, a packing cup associated with the head of the y,pis-

ton, a member-secured to the packing cup, a

non-rotatable member provided with teeth, and a thermostatically controlled detent mounted on the member on the packing cup and cooperating with the teeth on the non-rotatable member.

8. In apparatus of the class described, acyl- 'inder, a piston reciprocable in said cylinder, a

packing cup associated with the head of the piston, a member 'secured to the packing cup and provided with a pivot, a cup-shaped member positioned on said pivot and provided with teeth on its inner cylindrical surface, a spring -for holding said cup-shaped member in, position and preventing it from rotating, and a spiral temperature sensitive element having one end secured to the member on the packing cup and its other end provided with a detent for cooperation with the teeth of the cup-shaped member.

9. In'apparatus of the class described, a cylinder, a piston reciprocable in said cylinder, a packing cup associated with the head of the piston, a temperature sensitive element carried by the packing cup, means forming teeth on the piston. and detent means controlled by the temperature sensitive element and cooperating with the teeth for causing the cup to be rotated relative to the piston.

10. In apparatus ef the class described, a cylinder, a piston reciprocable in said cylinder and provided with a recessed head, a packing cup, a plate secured to the rear of the packing cup and associated with the piston head, means forming teeth on the inner wall of the recess, a temperature sensitive element carried by the plate, and detent means controlled by the temperature sensitive means and cooperating with the teeth for causing the plate and cup to be rotated relative to the piston.

11. In apparatus of the class described, acylinder, a piston reciprocable in said cylinder, a packing cup for the head of the piston, and means having operatively associated parts carried by the piston and by the cup for causing the piston and cup to have intermittent relative rotation.

12. In apparatus of the class described, a cylinder, a piston'reciprocable in said cylinder, a packing cup for the head of the piston, and thermostatically controlled means for causing the piston and cup to have relative rotation.

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18. In apparatus of the class described, a cyl- Y inder, a piston reciprocable in said cylinder, a

packing cup for the head of the piston, andratchet means for causing the piston and cup to have relative rotation, said means embodying a thermostatically controlled pawl.

14. In apparatusof the class' described, a cylinder, a pistonreciprocable in said cylinder and provided with a recessed head, a packing cup, a plate secured to the rear of the packing cup and associated with the piston head, means forming teeth on the inner wall of the recess, a temperature sensitive element carried by the plate, and detent means controlled by the temperature sensitive means and cooperating with the teeth for causing the plate and cup to be rotated relative tothe piston and the cylinder wall.

JOIl'lfll C. COX.

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