US2541953A - Self-cleaning hydraulic tappet - Google Patents

Description

O. H. BANKER SELF-CLEANING HYDRAULIC TAPPET Feb. 113, 1951 Filed May 11, 1946 A2 Sheets-Sheet 2' NN mM M Mw@ i N w/ fv INVENTOR. BY 056m" f/M/e/ WWW Patented Feb. 13, 1951 SELF-CLEANING HYDRAULIC TAPPET Oscar H. Banker, Evanston. Ill., assignor to New Products Corporation, Chicago, Ill., a corporation of Delaware Application May 11, 1946, Serial No. 669,190

12 Claims.

This invention pertains to improvements in a hydraulic tappet such as is employed in the operation of a poppet type valve, the tappet functioning to insure contact of tappet and Valve under Vall conditions and automatically compensating for variations in the latter in operation.

It is an object of the invention to provide a c tappet of the type described which is very simple and inexpensive in construction and assembly, having provision for maintaining an ample supply of operating liquid at hand in the body of the tappet for admission to a compression chamber therein, as required in the operation of the latter. t

A further object is to provide a hydraulic tappet including an internal plunger slidable in a cylinder disposed in the'tappet body and engageable with a valve stem to actuate the Valve, characterized by the provision of an absolute, liquid-tight seal between the coacting surfaces of the plunger and cylinder, there being novel means to effect a controlled escape of liquid act- 4ing on the plunger at a point axially of the plunger, to compensate for excessive hydraulic pressure developed in the operation of the tappet in its compensating function.

Yet another object is to provide a tappet of the type described which is automatically selfcleaning at the liquid escape passage, thereby preventing clogging therein such as would interfere with proper operation of the tappet.

More specifically, an object is to provide a tappet including a pressure chamber and a oneway valve controlling the entryof liquid to said pressure chamber, and means serving to define an escape passage for the controlled escape of hydraulic fluid from said chamber and to limit the movement of said valve, said means being adapted to keep the escape passage free from clogging by carbonization or deposit of impurities in operation, as well as minimizing likelihood of such deposition.

Still another object is to provide a hydraulic tappet having relatively movable parts coacting to define a liquid escape passage from a compression chamber in the tappet, in which the relative movement of said parts in the tappet operation functions to prevent clogging of the passage, thereby rendering the tappet automatically self cleaning.

A more specific object is to provide a tappet as described above in which one of the parts defining the liquid escape passage functions additionally to restrain a valve in the tappet and also as a spring reaction member for a further purpose.

The foregoing statements are indicative in a general way of the nature of the invention, but other and more specific objects will be apparent to those skilled in the art upon a full understanding of the construction and operation of the device.

Various embodiments of the invention are presented herein for purpose of exemplication, but it will be appreciated that the invention is susceptible of incorporation in other modified forms coming equally within the scope of the appended claims.

In the drawings,

Figs. 1-4 inclusive, are enlarged views in central vertical section through tappets in accordance with four different embodiments of my invention; l

The present invention `provides a novel and simplified hydraulic tappet to apply operating force from a cam to a poppet typevalve stem and to maintain contact of the tappet and stern under all conditions of operation. Tappets of this general type are well known; hence, it is Unnecessary to describe the theory and operation thereof in great detail. My improvements are concerned with the elimination to the greatest possible degree of `costly manufacturing operations in the production of such a hydraulic compensating tappet, and include simplified provisions whereby operating liquid is effectively sealed in a compression chamber in the tappet, but is permitted to escape in controlled quantity from said compression chamber in the event of excessive pressure arising as the result of elongation of the valve stern in operation. Each of the various forms of tappet disclosed herein embodies the feature of an absolute, liquid-tighty seal between a pair of coacting, relatively reciprocable parts of the tappet (i. e., a cylinder and plunger movable therein). Each also involves a liquid escape line constituted by a small self-cleaned bore in the plunger, at which the same slidably engages an upright pin of small cross section concentric with the cylinder. In all forms, expense of manufacture is greatly minimized, since ordinarymachine tool accuracy affords amply close tolerances between the coacting parts, byreason of the liquid-tight seal and the liquid escape provisions mentioned. Further specific provisions whereby cost of manufacture is reduced without sacricing effectiveness of operation will be hereinafter referred to.

Referring to Fig. 1, wherein one form of tappet according to the invention is illustrated, the reference numeral I0 generally designates a tappet body which is adapted to be mounted for reciprocation in a suitable guide or bushing in the engine block, in well known manner. The body is generally cylindrical in form and has a heavy circular plate il peripherally welded thereto to close one end thereof. The plate is adapted to be engaged by an operating cam of the engine cam in operation.

The body Il! is restricted at the waist I2 thereof and is ilared outwardly beneath and above said waist to afford an oil reservoir I3 of large capacity below said waist and above end plate Il. An oil supply opening I4 is formed in the wall of the body immediately below the waist I2, i. e., at an elevated point in the reservoir; this assures that a relatively large quantity of oil will be maintained in the reservoir under all conditions of operation of the tappet. The restricted waist I2 telescopingly receives a hollow compression cylinder I5, and the latter is provided adjacent its upper endwith an annular shoulder Iii whichrests on the cylindrical extension I2 of the restricted waist I2 of body I Ei, thereby xedly sustaining the cylinder in the body. A plunger Il is mounted for sliding movement in cylinder I5, having a relatively loose t therein. The clearance permissible between the cylinder and plunger is readily attainable in quantity production by standard machine tools employed in machining these parts.

The upper portion of the plunger is conformed to provide a head 2E engageable with the valve stem to actuate the same in the manner previously described.

A coil spring 2l disposed between the upper end of cylinder i5 and the plunger head 2U normally urges the same upwardly relative to the cylinder. This spring is seated at its opposite ends in undercut portions of the cylinder and plunger head.

Cylinder I5 extends a substantial distance downwardly into reservoir I3, terminating adjacent end plate I I of the body, and has an axial passage 22 in a valve seat insert 23 disposed therein. This passage leads to a compression chamber 24 in the cylinder, dened on one side by plunger Il and on the other by the inner end face of the cylinder I5, and insert 23. Flow of oil through passage 22 may take place in one direction only, i. e., from reservoir I3 to compression chamber 24, under the control of the ball valve 25 which seats over the upper end of the insert passage 22.

AA combined liquid escape metering pin and cage member 25 serves to limit upward movement of valve 25 relative to its seat. This member includes a spider-like cage 21,A concentrically force-fitted in a counter-bore in the lower end of the cylinder i5, and an upwardly extending axial metering pin 23. Plunger Il has a central bore 29 which slidably telescopes on the pin 28 and said bore communicates with a transverse passage 30 in the plunger. From this passage the oil then discharges to a peripheral groove in the plunger, whence it is returned to the engine crank case or other source through other liquid conduit means or passages.

In operation, a supply of oil is fed into the interior of reservoir I 3 through the opening I4, surrounding the lower end of cylinder I5 to a substantial height, and well over the passage 22. On the upstroke of plunger I'I, under the influence of spring 2l, oil is drawn by suction from said reservoir through passage 22, past valve 25 and into the compression chamber 24, filling the 4. same. Thereafter, lifting force applied by the engine-operated cam to the tappet body is transmitted through the compressed body of liquid in chamber 24 to the plunger I'I, thence to the poppet valve stem, all in well known manner. It will be noted that the O-ring I8 prevents leakage of liquid upwardly between the plunger and cylinder surfaces. Accordingly, these surfaces need not be closely machined. Rise in pressure in the compression chamber 24, due, for example, to elongation of the poppet valve stem under the heat of operation, simply results in the oil escaping in controlled amount between the adjacent surfaces of pin 23 and the plunger bore 29. It should be noted that the diameter of the pin and bore are small relative to the diameter of the plunger Il'. This insures a restricted and metered escape or discharge of oil between the coacting pin and plunger surfaces, without requiring close tolerance operations in manufacturing these parts to produce a close t therebetween. Provisions of a generally similar character are illustrated in my copending application, Serial No. 649,931, led February 25, 1946.

Should any air be entrapped in the liquid compression chamber 2fi, it is discharged at once through a radial passage 3| communicating the O-ring groove I9 with the central bore 29 at a point below the O-ring.k

It should be noted that in the tappet shown in l, and also in the other figures, the oil metering surfaces and escape passage between pin 2lik and bore 29 are self-cleaning, The operating movement of the plunger on the pin prevents carboniaation and clogging such as would quickly render the tappet inoperative.

In Fig. 2, wherein parts common to those appearing in Fig. 1 are designated by the same reference characters, the tappet plunger I l is axially chambered at its upper end, into which chamber the tappet metering pin 32 extends. An annular shoulder 33 is provided on the pin at a point internally of said chamber, against which shoulder a coiled compression spring 34 abuts. At its upper end, the spring engages a plug presstted in the chamber bore as a closure therefor, to urge the plunger upwardly, said spring encircling a vertically extending continuation of the 32. Pin 32 extends through an axial bore in the plunger and rests on the valve confining cage 2l as a support. While this cage is pressfitted in place in assembly, the spring loaded pin 32 additionally acts to prevent possibility of displacement thereof in operation. As in the embodiment of Fig. l, liquid from compression chamber 2li escapes controlledly at one point only, between the adjacent surfaces of the bore in plunger Il and pin S2 as required in the operation of the tappet. Cage 2l functions doubly to support the pin 32 and, as in the previous form, to restrain movement of the valve member 25. An annular expanding spring 36 disposed in an inner groove at the top of cylinder I5 serves to restrain upward movement of a plunger il.

In Fig. 3, wherein parts common to those of Figs. l' and 2 are indicated by like reference numerals, the O-ring I8 is disposed in a groove 37 of specialcharacter. In this form a hollow cylindrical member 38 is employed as a plunger, being closed at the upper end. The material dening the open lower end of plunger 38 serves as the upper wall of the O-ring groove 3l. Pressfitted in said open end is a plug 3S which is machined to provide a stop shoulder 4G engageable with the lower annular edge surface of said i; e plunger and an annular radially projecting flange 4 I. Said ange is spaced from the lower edge of the plunger and completes the annular groove receiving the O-ring I8, which has a` liquid-tight sealing engagement with the internal sealing periphery of the cylinder I5, The plug 39 is slidable on the pin 32, which has a flange above the plug serving as a support for the compression spring 34 urging the-plunger 38 upwardly. At the' same time, pin 32 acts downwardly on a perforated disk-like valve conning element 42, serving to maintain said element in place over the valve 25. In assembly, element 42 is loosely disposed in a recess 43 countersunk in the bottom of cylinder I5 andthe pin, under the force of Spring 34, prevents dislodgement thereof in operation of the tappet. This construction operates similarly to and affords al1 of the advantages of the forms shown in Figs. 1 and 2.

In Fig. 4 I illustrate a still further embodiment which is generally similar to that illustrated in Fig. 3. In this case the disk-like valve confining or restraining element 42 is placed loosely in the bottom of the compression chamber 24, being centrally arched to accommodate the valve. It is maintained in place, as in the embodiment of Fig. 3, by the central spring loaded pin 32.

A pug 45 is press-iitted in the lower end of the cylindrical plunger 38.. This plug has a peripheral flange 46 engaging said lower end and an annular face recess 41 beneath said flange. In this recess a flexible, inverted, cup-like sealing element 48 of L.section is secured by aV bonded connection, and it will be appreciated that under expansive force of liquid in compression chamber 24, the sealing element 48 is vurged outwardly against the wall of the cylinder for a very effective, positive and liquid-tight sealing engagement therewith. l

It will be noted that the embodiments of Figs. 2, 3 and 4 have in common the feature of an oil escape metering pin which functions additionally as a reaction member for the plunger lift 'spring and engages a valve restraining member as its own reaction member, serving thus the further function of holding said' member in xed valve restraining position. Great simplicity and lessened production cost result.

In all four embodiments the liquid escape pas sage is deiined between a relatively small diameter bore in the reciprocable plunger and a small diameter pin xedly disposed in the compression chamber and telescoped into said bore. The relatively loose iit of the pin in the bore provides for the desired,controlled escape of liquid in limited quantity, in view of the small peripheral dimensions of pin and bore. Yet this generous clearance eliminates the need for close tolerance machining in the production of the part. Furthermore, it prevents any tendency ofthe escape passage to catch and become clogged with paral ticles of foreign matter which would destroy the intended operation of the tappet. Additionally, the relative reciprocation of the pin vand plunger in operation insures that the escape passage is kept clean and in good operating condition.

l. A hydraulic tappet comprising a liquid source, a cylinder, a plunger reciprocable in the cylinder and in part defining a compression chamber therein, means defining a passage communieating said liquid source and chamber, a valve controlling said passage to permit iiow of liquid therein only in the direction from said source toy the chamber, a stop'memberA restricting move- 2. A hydraulic tappet comprising a liquid source, a cylinder, a plunger reciprocable in the cylinder and in part defining a compression chamber therein, means defining a passage communicating said liquid source and chamber, a

valve controlling said passage to permit flow of liquid therein only in the direction from said source to the chamber, said plunger having an axial opening therein, a pin disposed in said opening to denne therein an annular liquid escape passage through the plunger, and spring means abutting said pin and plunger above said opening to urge the same in opposite directions.

3. A hydraulic tappet comprising a liquid source, a cylinder, a plunger reciprocable in the cylinder and in part defining a compression chamber therein, means defining a passage communicating said liquid source and chamber, a valve controlling said passage to permit flow of liquid ytherein only in the direction from said source to the chamber, a stop member restricting movement of the valve, said plunger having an axial opening therein, a pin disposed in said opening to define therein an annular liquid escape passage through the plunger, said pin resting on said stop member, and spring means abutting said pin and plunger above said opening to urge the same in opposite directions whereby the pin maintains said stop member in operative position relative to the valve.

4. A hydraulic tappet comprising a liquid source, a cylinder, a plunger reciprocable in the cylinder over a compression chamber therein, means defining a passage communicating said liquid source and chamber, a valve controlling said passage to permit flow of liquidV therein only in the direction from said source to the chamber,

a stop member restricting movement of the valve, said plunger having an axial borevtherein, a pin disposed in said bore and resting on said stop member, and spring means engaging said pin to cause the pin to maintain said stop member in operative position over the valve, said pin and bore defining therebetween an axial liquid escape passage from said chamber and being relatively movable axially in the operation of the tappet to prevent clogging of said passage.

5. A hydraulic tappet comprising a liquid source, a cylinder, a plunger reciprocable in the cylinder over a compression chamber therein, means defining a passage communicating said liquid source and chamber, a valve controlling said passage to permit flow of liquid therein only in the direction from said source to the chamber. a stop member restricting movement of the valve, said plunger having an axial bore therein, a pin disposed in said bore and resting on said stop member, and spring means engaging said pin and plunger above said bore to cause the pin to maintain said stop member in operative position over the valve, said pin and bore defining therebetween an axial liquid escape passage from said chamber and being relatively movable axially in the operation of the tappet to prevent clogging of said passage.

6. A hydraulic tappet comprising a liquid source, a cylinder, a plunger reciprocable in the cylinder and in part dening a compression chamber therein, said cylinder having a passage communicating the chamber and source, a Valve `controlling said passage for flow of liquid therein only in the direction from said source to the chamber, said plunger being externally sealed with relation to said cylinder to prevent flow of liquid between adjacent surfaces of the plunger and cylinder, a stop member restricting movement of the valve, said plunger having an axial bore therein, a pin disposed in said bore and engaging said Astop member to maintain the same in operative position, said pin and bore coacting to define annular liquid escape passage from said chamber 'which is of limited area, and spring means abutting said pin and plunger to urge the same in opposite directions and maintain said stop member in operative position relative to the valve.

7. A hydraulic tappet comprising a liquid source, a cylinder, a plunger reciprocable in the cylinder and in part dening a compression chamber therein, said cylinder having a passage communicating the 'chamber and source, a ball valve controlling said passage for iiow of liquid therein only in the direction from said source to the chamber, said plunger being externally sealed with relation to said cylinder to prevent flow of liquid between adjacent surfaces of the plunger and cylinder, a stop member restricting movement of the valve, said plunger having a relatively small axial bore therein, a relatively small pin disposed in said bore with a relatively free clearance therein, said pin engaging said stop member to maintain the same in operative position, said pin and bore coacting to define an annular liquid escape passage from said chamber which is of limited area, and spring means abutting said pin and plunger above said bore to urge the same in opposite directions and maintain said stop member in operative position relative to the valve.

8. A hydraulic tappet comprising a cylinder providing a compression chamber, a plunger shiftable axially in said cylinder at one side of' said chamber, a source of liquid, means defining a one-way passage from said source to said chamber, said plunger including a body openl at one end and a flanged, axially-bored plug s cured in said oren end, said body and the plug ange coacting to denne an annular groove concentric with the plunger, a sealing element disposed in said vgroove in sealing relationr to the internal wall of Ythe cylinder to prevent escape of liquid between adjacent surface 'of the plunger and cylinder, a pin disposed in the bore of ksaid plug and coasting therewith to define an annular liquid lescape passage from said chamber of limited area, and a spring disposed between said pin and plunger' body to separate the same axially.

9. A hydraulic tappet comprising a cylinder providing a compression chamber, a plunger shiftable axially in said cylinder at one side of said chamber, a source of liquid, means dening a one-way passage from said source to said chamber, including a valve member, and a perforated restraining element maintaining said valve member in position relative to said passage, said plunger including a body open at one end and an axially-bored plug secured in said open end, said body and plug coacting to dlfne an annular groove concentric with the plunger, a sealing element disposed in said groove in sealing relation to the internal wall of the cylinder to prevent escape or" liquid between adjacent surfaces of the piunger 'and cylinder, a pin disposed in the bore of saidzplug and resting on Vsaid restraining element, said plug bore and pin defining 'an annular liquid escape passage from said chamber df limited area, and a spring disposed between said pin and plunger body to separate the same axially and 'maintain said pin in engagement with said retaining element.

10. A hydraulic tappet comprising a cylinder providing a compression chamber, a plunger shiftable axially in said cylinder at one side of said chamber, `a sourceof liquid, means dening a one-way passage Afrom said source to said chamber, said plunger including a body open at one end and an axially bored plug secured in said open end, said body and the plug iiange coacting to denne an annular groove concentric with the plunger, a sealing element disposed in said groove in sealing relation to the internal wall of the cylinder to prevent escape of liquid between adjacent surfac.s-of the plunger and cylinder, and means defining an annular liquid escape passage of limited area from 'said chamber through the plunger.

1l. A hydraulic tappet comprising a cylinder, a source of'liquid, valve vcontrolled means providing Va one-way passage communicating the interior of said Vcylinder 'with said source, and a plunger sh-iftable axially 'in said cylinder and deiining therein a compression chamber adapted to be communicated with said passage, said plunger comprising a hollow head closed at one end, sealing means to prevent escape of liquid under compression in said chamber between adjacent surfa-c'es of the cylinder and plunger, said plunger being centrally apertured, a pin extend ing through said aperture to dene a liquid escape passage of restricted capacity through the plunger, and a coil spring surrounding said pin above said aperture, with its opposite ends respectively abutting the pin vand the closed end of the plunger head to urge the pin and plunger in opposite directions.

12. A hydraulic tappet comprising a cylinder, a source of liquid, Valve controlled means providing a one-way passage communicating the interior of said cylinder with said source, and a plunger shiftable axially in said cylinder and dening therein a compression chamber adapted to be communicated with said passage, said plunger comprising a hollow head closed at one end and open at the other, a plug telescopingly fitted in the open end of said head, sealing means to prevent escape of liquid under compression in said chamber between adjac. nt surfaces 'of the cylinder and plunger, said plug being centrally apertured, a pin extending through said aperture to define a liquid escape passage of restricted capacity through the plug, and a coil spring surrounding said pin above said aperture, with its opposite ends respectivcly abutting the pin and the closed end of the plunger head to urge the pin and plunger in opposite directions. l

OSCAR H. BANKER,

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS

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