US2752903A - Hydraulic tappet - Google Patents

Description

July 3, 1956 o. H. BANKER 2,752,903

HYDRAULIC TAPPET Filed Nov. so, 195o N i I i l A Y.

37@ awa/Z329@ 25 717 INI/ENTOR.

, j #0 S," 64 7 066m .5am/65 y "/Sv v 6 7 BY 35@ 60 55 M @a .29@ W HYDRAULIC TAPPET @scar H. Banker, Evanston, Illt, assigner to N ew Products Corporation, Chicago, lill., a corporation of Delaware Application November 30, 1950, Serial No. 198,439

26 Claims. (Cl. 12S-90) The present invention relates to improvements in hydraulic tappets, commonly employed in automotive installations to transmit valve opening thrust between an operating cam and a valve stem. The tappet is characterized by improved means for providing an automatic backlash built into the tappet itself for the purpose of maintaining proper timing of valve opening and closing, without requiring re-design of the cam shaft when used as a replacement unit, and of insuring quiet operation.

Generally, it is an object of the invention to provide a tappet of the foregoing type having provisions for producing a predetermined, accurate, controllable backlash or time delay between the commencement of the valve lifting phase of operation of a cam and the commence ment of actual lift of the valve through the agency of the tappet, which provisions include an improved internal sealing member adapted to operate with uniform efliciency over a long period of use, and, furthermore, responsive instantaneously to pressure in the tappet compression chamber at the conclusion of the backlash period to control leak-by from that chamber to a source.

Another object is to provide an improved hydraulic tappet including a hollow cylindrical, cam actuated, external body and a plunger unit mounted for limited axial movement in said body and adapted to transmit thrust through the agency of a hydraulic column in the body on one side of the plunger unit, in which the plunger unit includes relatively movable elements of improved character to achieve accurate control of the intended backlash, represented by a controlled, relative lost motion of the elements before the tappet becomes effective to actuate the valve or related element.

Yet another object is to provide a hydraulic tappet of the sort referred to in the preceding paragraph, in which the plunger unit includes a radially expansible plunger element for the purpose of affording a controlled leak-by of hydraulic operating liquid from a compression chamber on one side of the unit to a source of liquid, the plunger eecting an absolute liquid-tight seal at the conclusion of the relative backlash movement of the elements of the plunger unit.

Still more specifically, it is an object to provide a hydraulic tappet including a cam actuated body and a plunger unit slidable axially therein, in which the plunger unit and body are spring urged for constant engagement, respectively, with a valve and cam, or equivalent elements, and in which the plunger unit includes a tubular radially exible, pressure responsive element exposed to pressure in a compression chamber in the body and ex panded by that pressure into gripping engagement with the wall of the body after a predeterminedly timed lost motion or backlash interval, to check leak-by and enable the tappet to act positively through the hydraulic column in said compression chamber to which the pressure responsive element is disposed.

Another object of the invention is to provide an improved hydraulic tappet characterized by a hollow body Llt) 2,752,903 Patented July 3, 1956 ICC having a plunger unit of novel character mounted for relative axial movement therein, in which the body and plunger unit coact to define an improved anti-aeration liquid reservoir on one side of the plunger unit and a compression chamber on the opposite side thereof.

Another object of the invention, in one of the embodiments thereof, is to provide a hydraulic tappet including, in combination with the features referred to in the preceding paragraphs, a ball check or equivalent movable valve element associated with the plunger unit and acting to positively cut off the main line of communication from the tappet compression chamber to a source of operating liquid immediately after the commencement of tappet actuation.

A further specific object is to provide a tappet having an external body and a plunger unit slidably guided therein, in which said plunger unit includes a rigid thrust transmitting element and a liexible and radially expansible sealing element adapted to be engaged by the thrust transmitting element following a predetermined backlash period so as to control leak-by from the compression chamber of the tappet, the sealing element being radially expanded against the wall of the body by pressure in said chamber in achieving this control.

Still another object is to provide a tappet of the above general description which has a built-in backlash feature atfording a variable backlash control in which a bacio lash measurably smaller at high engine speed than at low engine speed may be obtained, thereby enabling the engine to deliver smooth, economical power while idling and increased power at high rates of operation.

Another object, in one embodiment of the invention, is to provide an automatic backlash tappet in which a definite backlash interval is determined by a relative lost motion between two axially engaging parts of the tappet plunger unit, and in which one of those parts is a sealing member of special improved construction enabling a still further cushioning movement under hydraulic pressure following axial engagement of the parts.

A still further specific object of the invention is to provide a lost motion, built-in backlash tappet construction of the foregoing character in which, in one embodiment thereof, a sealing member of its plunger unit consists of a single, unitary, axially flanged mem ber of molded synthetic plastic or equivalent material; in which, in another embodiment thereof, this member is a composite one including a rigid disk, and a nonmetallic sealing element of rubber, synthetic rubber or plastic appropriately bonded to the disk, preferably in a manner to permit a slight resilient cushioning movement between the disk and sealing element under hydraulic pressure; and in which, in still another embodiment, the element is a composite one including a split, body engaging ring of resilient metal having a circumferentially continuous band of flexible, non-metallic material bonded to a peripheral surface thereof, all of these members acting to produce a hydraulic seal against the wall of the tappet body under pressure exerted internally of the same following the backlash phase of operation of the tappet.

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

Several embodiments of the invention are presented herein for purpose of illustration, and it will be appreciated that the invention may be incorporated in other modified forms coming equally within the scope of the appended claims.

In the drawings:

Fig. 'l is `a view in longitudinal 'section through the axis of a hydraulic tappet in accordance with one embodiment of the invention, showing the tappet parts prior to their backlash operation, it being understood that a valve and actuating cam normally associated with this tappet have been omitted;

Fig. 2 is a fragmentary View partially broken away and sectioned similarly to Fig. l, lillustrating the tappet parts of that figure after their 'backlash operation;

Fig. 2A is a fragmentary view in section similar to Figs. l and 2, illustrating a slightly modified embodiment of the invention in a tappet generally 'similar to that of those figures;

Fig. 3 is a view in axial section through a lhydraulic tappet in accordance with a modified embodiment of the invention, -at -a part of its operating 'cycle corresponding to the phase shown in Fig. l;

Fig. 4 is a fragmentary view in section "similar to Fig. 3, illustrating the -tappet parts of that iigure following the backlash phase, -and showing the cushion action of the particular plunger member employed in this embodiment;

Fig. 5 is a view in axial sec-tion through a still further modified adaptation of the tappet of ythe invention;

Fig. 6 is a 'fragmentary view in axial section through the tappet of Fig. 5, showing the same in another phase of its operation; :and

Fig. 7 is a view in transverse 4horizontal section along line 7-7 of Fig. 6.

Referring to Figs. 1 and 2 of the drawings, illustrating a hydraulic tappet 110 in accordance with one embodiment of the invention, the reference numeral 11 designates a hollow, cylindrical body `adapted to be actuated by engagement of its closed -end 11a by a cam on an automotive cam shaft ink well known fashion. The numeral 12 designates generally a composite plunger .unit which is mounted for limited axial sliding movement `of 4the body 11.

The unit 12 includesan upper thrust transmittingplunger member 13 having a top anvil lof reduced diameter which is directly engageable with a valve stern or equivalent member (not shown), this yanvil being :integral with an enlarged plunger portion 14 which `is..perfipherally Igrooved at 15 for the receptionof airubberfor synthetic rubber O- ring 16. A split snap ring i14arreceivable in an inwardly opening groove adjacent the upper lendof the bore 17of body 11 serves to prevent separation of the plunger unit from said bore.

O-ring 16 slidably engages bore 17 -to seal `from the atmosphere la secondary reservoir 18 yof the tappetrlocated immediately beneath plunger portion 14, inwhich a supply of hydraulic operating liquid, not shown, `is maintained. One of the features of 'the invention, common to all three of the illustrated embodiments thereof, lconcerns a particular `reservoir construction, to .be described, and, moreover, in all three forms the tappet is shown as a self-contained one. However, it is yto be understood that these particulars are not especially controlling in importance to the operation of the tappet as a whole, i. e., that under certain circumstances :the source of operating liquid may be an engine fed one and that the particular reservoir structure may be altered or omitted.

A reduced diameter stern 19 of substantial length 1integrally connects portion 14 of the plunger member v13 with an enlarged radial guide flange 20 which denes the lower extremity of the secondary reservoirl. Flange 20 is also guided by'body bore `17 and is Vprovided with a lplurality yof milled, slot-like, axially extending passages 21 about its periphery, for a `purpose to be 'described.

An integral neck y22. of 'reduced diameter o-n plunger member 13 connects lthe lower vsurface of Aits .ilange 20 with a :further radially extending .guideand sealing flange 23 of disk-like character. :Flan-ge 23 .coacts with anjge20 in defining a primary reservoir 24 for hydraulic operating liquid. It will be seen that reservoirs 18 and 24 are freely communicated by 'the small passages 21 referred to above. An axial bore is formed in neck 22 and bottom flange 2.3 of plunger 13 to constitute a liquid flow passage or conduit, and radial ports 27 communicate passage 26 with the primary reservoir 24. Upper plunger member 13 constitutes one main subdivision of the composite plunger unit 12.

A second part of the composite, three-.part plunger unit 12 is constituted by a spring and valve retainer 29 and its associated elements. Retainer 29 is of hollow tubular shape, subdivided between its ends by a transverse partition 30, vand it extends downwardly into a restricted diameter portion 31 of the bore of body 11. The last named portion is part of a compression chamber 32 defined bctween the plunger unit 12 and the closed bottom 11a of the body 11. A coil compression spring 33 is housed in retainer 29, abutting partition 30 at its upper end and the closed bottom of the body at its opposite end. Spring 33 maintains the upper end of retainer 29 in engagement with the lower surface of bottom frange 23 of plunger member 13. By the same token, in tending to axially separate body 11 from plunger unit 12 it maintains engagement lof the body and plunger unit with the actuating cam Vand actuated valve stem, respectively.

T he space 34 `in the interior of retainer 29 immediately above partition 30 receives a spherical ball check or equivalent valve element 35, the proportioning `of this ball check vbeing such that when it rests on partition 30 there isa clearance of about .003 between the same and an annular knife-edge seat 36 which is 'defined by the 'lowermost edge 4of passage 26. A small port 37 in partition 30 communicates space 34 with the interior of hollow rerainer member 29, hence with the compression chamber 32.

The third and `final element lof lthe plunger unit 12 is `afspecial, downwardly cupped or `flanged `sealing member 38 of exible non-metallic material. It hasa central axial opening which is slidably guided on a reduced-diameter upper `'extension or neck 39 of the retainer member 29. 4Thetransverselydisposed upper `wall 'Alti-of `sealing member 38 engages veither against an rupwardly facing shoulder 41 on member 29 adjoining its reduced neck 39or against the lower Asur-faceof the flange 23 of plunger member lpdepending upon the ,phase in which the -tappet is operating, as will be described.

The thickness of ltransverse wall di) `is less than the space between shoulder 41 and `flange 23, providing for a predetermined.clearance space, designated rf, between wall it? and plunger member 13 or retainer' 29. This space is .Gly-.020" -in the illustrated embodiment, no attempt having been made to show `the same accurately in the drawing. There will be further reference to the described relationship.

Sealing member 38 is 4fabricated :of a suitable .inonmetallic material .possessing sufficient resistance .to heat and -to deterioration by hydrocarbon operati-ng liquid, Vas well as'suicient toughness and wearability., to adapt rthe same for my purpose. It also Yhas sufficient yiexibility to enable its downwardly extending peripheral ange 33 to exert greater .radial ygripping action on the bore 17 of body `11 under full hydraulic voperating pressure than when that pressure is relaxed. Suitable materials having these characteristics -will readily suggest themselves; synthetic rubber and various synthetic Aplastics having proper heat resistivity, hardness, toughness vand flexibility, characteristics readily controlled by known manufacturing procedures, are examples. Member 38 is riitted into body bore 1.7 with ya frictional slid-e tit, such that it can be `moved up or down therein only by .exertion Aof slight force. It is provided with ports 42 in its transverse wall 40for the-passage'of operating liquid from compres sion chamber 32 in one of the phases of tappet operation.

.1n o peration, let it beassumed that a suitable Vsupply of hydraulic operating liquid `is ,present in vthe secondary g reservoir 1S, primary' reservoir 24 and compression chamber 32, that the plunger unit 12 has its upper member 13 engaged against a valve stem or equivalent, urged downwardly by a spring (not shown), and that an actuating cam is operating upwardly against the lower surface or body 11. As the cam enters its rise the parts are in the condition shown in Fig. l of the drawings, in which the wall dil of tubular sealing member 3S rests on shoulder lil of retainer 29, presenting clearance space a between its upper surface and flange 23. Body ll is held downwardly by the force of the valve stem on the plunger member lf3, as the result of which liquid in compression chamber 32 is forced upwardly around ball check 35 and through port 27 for an instantaneous period, after which the ball check seats and ends this flow. Further upward force now exerted by the cam on the body lll is resisted by the conventional valve spring (not shown), causing plunger member 13 and retainer 29 to move downwardly as a unit relative to body f1. Being retained in place relative to the body by its frictional engagement with the bore f7 of the latter, the flexible sealing member 38 does not move relative to the body and its transverse wall 40 is approached by flange 23 of plunger member lf3. During this movement a relatively rapid leak-by of liquid occurs through the port l2 in sealing member wall ffl and between flange 23 and the body bore i7, in which the flange is received with relatively loose clearance. Thus a relative lost motion of plunger member lf3 and sealing member 33 of .O15-.020 inch, representing the clearance a, occurs, during which the plunger unit )l2 is ineffective to lift the valve against the force of its valve spring.

Following the aforesaid lost motion, the flange 23 and upper surface of wall di) engage, closing off port 42. The position of the parts is shown in Fig. 2. Thereupon the full hydraulic pressure of the liquid column in compression chamber 32 is exerted against the flexible sealing member 33, thrusting the flange 38 of the latter in a radial direction tightly against the internal body bore i7. Peripheral leak-by is now sealed off and the lifting action of the cam is transmitted positively through the hydraulic column in chamber 32 and plunger unit 12 to the valve. Slow leak-by occurs outside the member 38.

The initial compression of liquid in chamber 32 is accompanied by leak-by of air and liquid from the chamber, and the dual reservoir construction of the upper plunger member f3 insures that all air will be exhausted to the upper reservoir ld, passing through the milled grooves 21 in the flange 2li of member 13. Primary reservoir 24 is constantly replenished from secondary reservoir i8 and being at all times full of liquid, is not subject to aeration during high speed operation.

lt is evident from the foregoing that the amount of backlash between the actuated valve or plunger unit 12 and actuating cam (or tappet body lll) between the time that the cam enters its rise and the time that the valve commences to lift from its seat can be accurately determined by a selective dimensioning of clearance space a. This may be done by a proper proportioning of the depth of shoulder 4l on retainer 29, and selection of the thickness of sealing plunger wall 40. Thus clearance l represents in effect a definite, gauged backlash which is built into the unit, enabling chatter-free operation of the tappet and maintaining proper timing of the valve opening and closing cycle while maintaining constant engagement of an actuating cam, tappet lil and valve stem with one another.

The depending flange 3S of flexible tubular plunger member 3S is sealed against the internal body wall 17 immediately following closing of port 42 by the plunger flange 23, so that escape of liquid between flange 39 and the bore f7 is checked or definitely slowed, to a readily controlled amount, depending on the flexibility of the flange. Because of the fact that rise of pressure in cornpression chamber 32 is sudden, and because of the aforesaid flexible character of the flange, its' sealing act'iori against the body bore will retain its eflciency regardless of how long the tappet is used and the amount of wear on the sealing plunger, Leak-by at any given point is maintained practically constant.

After the lifting cycle is ended, the tappet returns to a dwell or relaxed position. In doing this, the internal spring 33 pushesiretainer 29 and plunger member 13 upwardly with reference to the position of Fig. 2, maintaining contact of unit 12 with the valve stem. and body 1l with the cam. This action causes liquid to be drawn into compression chamber 32 through ports 27, passage 26, and retainer partition port 37. Flexible plunger member 3S remains frictionally retained in. place against the body bore 17 and when the retainer shoulder 4l engages the lower surface of its wall 40, its original clearance of .O15-.020 inch from the upper plunger member flange 23 is present. Liquid will enter readily into the clearance space through port 42 to dissipate any suction effect which might otherwise tend to keep the adjacent surfaces together. The tappet assembly is again in its dwell position shown in Fig. 1, ready for another operating cycle.

In the event of failure of oil supply, should the above structural features be incorporated in a tappet whose pressure chamber 32 is supplied from a hydraulic pressure line rather than from a self-contained reservoir, or in the event all of the liquid is lost from the reservoirs f8, 2d, the lower end of retainer Z9 will ride the bottom of tappet body 11, thus insuring that the tappet will continue to function in a mechanical fashion.

The embodiment illustrated in Figs. l and 2 of the drawings features a sealing member 38 which is illustrated as being fabricated of a suitably tough, wear and heatresistant synthetic plastic. This permits radial llexure of the sealing member flange against the tappet bore f7, as described above; however, the flange is insufficiently yieldable to result in an absolute liquid-tight seal against the bore. A controlled, slow leak-by occurs from the compression chamber about the periphery of flange 3d after the passages 42 are sealed off, thereby accommodating valve stem elongation. In another adaptation resembling the form shown in Figs. 1 and 2, this slow leak-by is accomplished somewhat differently.

Referring to Fig. 2A, in which parts corresponding to those in Figs. 1 and 2 are designated by similar numerals with the subscript a, the cupped tubular sealing member 38a is fabricated of a more elastic or flexible material, such as synthetic rubber. In such a construction the sealing of passages 42a results in the flange of member 3dr: being thrust tightly into absolute sealing engagement with the tappet body bore. Hence, to allow the desired slow leak-by, the flange 23a of the upper plunger is provided with one or more small ports 25 leading to the primary reservoir. Leak-by will occur to ports 25 between the reduced neck of retainer member 29a and the relatively loosely fitted bore of plunger member 38a. ln other respects the operation is the same as that described with reference to Figs. l and 2.

A modified and very successful adaptation of the principles of the invention is illustrated in Figs. 3 and 4. Inasmuch as certain of the parts thereof are almost identical in structure and correspond in function to parts shown in Figs. l and 2, they `will be identified by corresponding reference numerals, primed, and further detailed description thereof will be dispensed with. The essential difforence between the tappet l5 of Figs. 3-5 and the tappet 1lb is that the former dispenses with the ball check of the latter and features a flexible walled plunger member of different character.

As illustrated in Figs. 3 and 4, leak-by ports 46 extend through the lower flange 23 of the upper plunger 13' immediately to one side of the neck 47 of the latter, which in this case is solid in cross section. The tubular sealing plunger 48 employed is of composite, two-part construction. It includes a synthetic rubber 4outer sealing member 49 of annular, cup-like, downwardly flanged cross section, the flange 50 thereof being'flared outwardly somewhat in its relaxed condition to insure a fairly tight lit in the body bore 17', as referred to in connection with `the tir-.st embodiment. This inherently flexible member is molded to a rigid metal disk kor washer 51 at its transversely extending or anged upper portion 52. The disk is flanged slightly and nested into the opening of flange 52 in which it is molded. A series of leak-by ports 53 are formed through flange 52, outwardlyof disk 51 and the ports 46 in plunger' member flange 23.

The composite sealing member 48 is guided by a lpin 54 force-titted in a radially flanged, sheet metal sleeve `55, the bore 56 of disk 51 having relatively loosely fitted sliding engagement with the pin. This affords a lealohy passage of restricted area between the pin and disk bore, due to the small diameter thereof land notwithstanding the relatively free tolerance tit of the gparts. The passage is also self-cleaning, as in the tappet illustrated ,and described in my Patent No. 2,541,953 of February 13, 1951, and my copending application, Serial No. 744,975, filed April 30, 1947, now abandoned. A coil spring 58 acts between y the radial flange 59 of this sleeve and the bottom yof tappet body 1l' to urge pin 54 ,against the lowersurface of flange 23 of the upper plunger member 13', thus insuring contact of the upper plunger member with the valve stem and of the body 11 with the actuating cam.

It should be noted -that the nested and bonded sealing member flange 52 and disk51 are capable of some slight axial iiexure or shift relative to the remainder yof sealing member 4%, under pressure in compression chamber 32' (see Fig. 4). This provides a iinal cushioned component of backlash at the conclusion of the normal backlash lost motion, as hereinafter described.

The general operation of the above described form `of tappet will be understood readily, since it is fundamentally similar in that respect .to the form shown in Figs. 1 =and 2 but omits a ball check. Upon commencement of lifting effort by the cam the parts are in the `position `shown in Fig. 3, with axial clearance a between sealing -rnember 49 and ,plunger flange 23. The conventional valve .spring (not shown) resists movement of Vthe upper plunger 13', and pin 54 and sleeve 55 are forced downwardly .relative to body 1.1 against the force of spring .58. The desired rapid leak-by takes place through :ports 53 and 46 as clearance a is closed, until the lower surface .of plunger flange 23 engages sealing member flange 51 to close off ports 53, as shown in Fig. 4. The .hydraulic :pressure in compression chamber .32 now urges depending flange 50 of member 49 radially outwardly against the internal body bore 17 and also acts upwardly against wall lor flange 52. The tappet then transmits yforce through the hydraulic column in chamber 32. The tappet 'body bore is sealed and controlled leak-by may take `place between pin 54 and the bore 56 of disk 51.

Referring to Fig. 4, yit is to -be noted that the flexibility offlange S2 allows a slight upward distortion :thereof under full hydraulic pressure, which cushions the applicw tion of the force and also adds an `.extra increment of backlash b to that represented by the clearance space a'. ln this design ythe backlash space a is' modified so that the total backlash ofthe tappet will bethe sum of clearances a plus b and equal to .O-.020. It is preferable that the sealing member be fabricated of synthetic `rubber or equivalent resilient material so as to effect a permanent liquid seal about its outer diameter, preventing Vleaklby in this zone. Slow .leak-by takes place 'between 4washer and On the reverse stroke the spring 58 causes-pin :54 v.and plunger member v1-3' yto riseagain, opening the Vclearance space .a above member 49 and enablingsliquidto rie-enter compression .chamber 32 through ports V46, IS13. This restores the .tappet to 'the Acondition shown in Fig. 3, ready for the.succeeding;cycle.

A still further modified embodiment `of the invention is illustrated in Figs. 5, 6 and 7, .in which parts corresponding generally in structure and function to those shown in Figs. 3 and 4 are denoted by corresponding reference numerals, double primed. Here again, a composite tubular flexible sealing member, designated 60, is employed, being associated with a spring retainer vand guide member 61 having a relatively loose sliding lit in the bod-y bore 17".

The member 60 comprises an annular outer ring 62 of metal which is split at 63 for radial flexibility. A continuous annular sealing band 64 of resilient material such as synthetic rubber is molded to the inner periphery of ring 62, the band being radially inwardly flanged around its upper margin, `as indicated Iat 65, to deline a cent-ral aperture 65. The upper surface .of sealing plunger 6) is flat for flush sealing engagement with the lower surface of the flange 66 of upper plunge-r i3. Flange 66 is imperforate in this instance. The band 64 is preferably applied to ring 62 in such manner as to till in the joint .63 of the latter, thereby insuring against axial liquid flow at this point. A controlled, slow leak-by may occur about the periphery of metal ring 62, which has a relatively loose lit 4in the tappet body bore 17".

The spring retainer and guide member 61 has an integral upper extension 67 of reduced diameter, which engages against the flange 66, this pin'being of substantially smaller diameter than the axial opening in resilient sealing band 64. Member 61 ,has a wide, ydisk-like intermediate flange 68 which guides the same loosely in body bore 17, and pin-like extension 69 thereon serves to center coil spring 70 which acts between the bottom of tappet body 1li and the radially ,enlarged frange 68 of the retainer. A port 71 yof .substantial size is drilled through liange 68 to communicate compression chamber 32 with the space 72 internally .of the composite sealing member ln operation, hydraulic pressure in compression ,chamber .32 is effective on the inner surface vof the plunger member 6.0, causing the split ring 62 to be expanded and forced outwardly into gripping and ow restricting relation to the body :bore 17". Band 64 seals the plunger member peripherally. The pressure is also effective against the radially inwardly extending exible flange 65 .to urge the same more for efully against flange 66, `ealing against radial flow therebetween. The clearance a insures the same built-in backlash action in the embodiment of .'Figs. 5, 6 and 7 asis found in the other two forms, and its operation in providing the timed backlash is .much the sante. As stated, a slow, controlled lealeby takes place `about the periphery of ring 62, once it has been urged outwardly.

Reference has been made ,to my copending application Serial No. 744,975 .in connection with the particular selfcleaning lealoby feature possessed. by the modification of Figs. 3 .and 4 of the drawings. That application also is directed to abuilt-in backlash `feature involving a delayed action ball check. However, it has been found that the delayed action ball check arrangement tends to be erratic, particularly at high engine speeds. It loses needed valve lift at such high speeds and thus causes the valve to fail to supply the delinitely increased fuel requirements which accompanying the same. However, in the present improvements, particularly 'the form illustrated in Figs. l and 4 of the drawings, not only is proper backlash provided for economical, noise-free `operation when idling or at lower drive speeds, but adequate fuel Vis also supn plied for best operation at high engine rate. That is, it :has been established that at high speeds Ithe tappet loses part of the original built-in backlash, causing the valve to be opened more than the actual tappet design contemplated. Thus, assuming that the designed built-in backlash ought `to amount to .02() inch, it has been found by electronic measuring equipment used ,in actual `engine operation that this backlash is fully -retained up to an engine .speed of, ysay, '700 .'R. l. M. As the speed is araches gradually increased further the backlash gradually diminishes, so that at full engine speed of 4000 R. P. M. only .002 inch backlash is measurable, instead of the .020 inch actually intended to be built into the design. This is a very desirable phenomenon because it allows the engine to idle smoothly and with economical fuel consumption, taking full advantage of the designed backlash; yet as the engine speed increases, the effective valvelift increases, enabling more fuel to be delivered to satisfy the increased requirement at the high rate.

it has been found in the operation ol existing types of hydraulic tappets that at extremely high engine speeds there is a tendency, due to inertia, of the tappet-actuated valve to toss up beyond the normal stroke mechanically exerted by the cam. Conventional hydraulic tap-pets will follow up this valve toss up, expanding the internal plunger structure of the tappet relative to its cam-actuated body, so that at the next cycle the valve will remain This failure of the valve to close continues until such time as the engine is decelerated and the plunger structure again allows the valve to re-seat, by forced leak-by of hydraulic operating fluid at the plunger. However, it the high speed action is prolonged there is a danger that the valve will be burned. The tappets in accordance with the various modifications herein illustrated and described avoid this characteristic objectionable high speed action, since the O-rings i6, 16', lo act as brakes resisting movement of the respective axially engaged plunger units during the split-second action at which toss up otherwise occurs.

i claim:

l. A hydraulic tappet comprising a hollow cylindrical body and a plunger unit mounted for limited axial sliding movement in said body and delining a compression chamber between the same and said body, said plunger unit comprising upper and lower, axially engageable plungers mounted in predetermined, axially spaced relation to one another to provide a lost motion backlash clearance space of predetermined size the ebetween, said lower plunger including a radially expansible sealing member having a portion of llexible non-metallic material exposed to pressure in said compression chamber, which sealing member is adapted to ex into sealing engagement with the wall of said body under augmented pressure in said chamber, there being a leak-by path of substantial capacity from said compression chamber through said sealing member which is closed by said plungers upon axial engagement thereof following relative lost motion equal to said clearance space, thereby to augment said chamber pressure and cause said sealing member to radially expand and envage said wall with increased force, and means to urge said plunger unit outwardly of the bottom of said body.

2. A hydraulic tappet comprising a hollow cylindrical body and a plunger unit mounted for limited axial sliding movement in said body and defining a compression chamber between the same and said body, said plunger uni't comprising upper and lower, axially engageable plungers mounted in predeterm-ined, axially spaced relation to one another to provide a lost motion backlash clearance space of predetermined size therebetween, said lower plunger including a radially expansible sealing member having a portion of flexible non-metallic material exposed to pressure in said compression chamber, which sealing member comprises a central disk to which said sealing portion is peripherally bonded in a manner enabling said disk to shift axially relative to the remainder of the sealing member under said compression chamber pressure, thereby aiiording an additional 'backlash increment, said sealing member being adapted to flex into sealing engagement with the wall of said body under augmented pressure in said chamber, there being a leak-by path of substantial capacity from said compression chamber through said sealing member which is closed by said plungers upon axial engagement thereof following relal@ tive lost motion equal to said clearance space, thereby to augment said chamber pressure and cause said sealing member -to radially expand and engage said wall with increased force, and means to urge said lower plunger outwardly ofthe bottom of said body.

3. A hydraulic tappet comprising a hollow cylindrical body and a plunger unit mounted for limited axial sliding movement in said body and defining a compression chamber between the same and one end of the body, said plunger unit comprising upper and lower, axially engageable plungers mounted in predetermined, axially spaced relation to one another to provide a lost motion backlash clearance space of predetermined size therebetween, and a spring urging said plungers for constant engagement with one another, said lower plunger including a radially expansible sealing member in the form of a rigid annular disk and a sealing element of exible nonmetallic material bonded peripherally to said disk and exposed to pressure in said compression chamber, said sealing member being adapted to Hex into sealing engagement 'with the wall of said body under said pressure, and a central guide pin on. which the bore of said annular disk is slidably mounted, there being a leak-by path of substantial capacity from said compression chamber through said plungers which is closed by axial engagement of said upper plunger and sealing member following relative lost motion equal to said clearance space, thereby to augment said chamber pressure and cause said sealing member to radially expand and engage said wall with increased force.

4. A tappet in accordance with claim 3, in which said pin and the surrounding bore of said disk define a leakby path from said chamber which is of substantially restrioted capacity compared to the first named leak-by path.

5. A hydraulic tappet comprising a hollow cylindrical body and a plunger unit mounted for limited axial sliding movement in said body and defining a compression chamber between -the same and one end of lthe body, said plunger unit comprising separate upper and lower, axially engageable plungers mounted in predetermined, axially spaced relation to one another to provide a lost motion backlash clearance space of predetermined size therebetween, said upper plunger being provided with an external non-metallic sealing ring in frictional engagement with the internal wall of said body to prevent upward overthrow of said upper plunger relative to said lower plunger and said body, said lower plunger consisting of a one-piece, tubular radially expansible sealing member of flexible non-metallic material in relatively fixed `friotional engagement with the internal wall of said body and exposed to pressure in said compression chamber, which sealing member is adapted to hex into tight sealing engagement with said `body wall under augmented pressure in said chamber, and a guide member on which said sealing member is mounted for relative axial movement, there being a leak-by path of substantial capacity from said compression chamber through said sealing memberwhich is closed by axial engagement thereof with said upper plunger following relative lost .motion equal to said clearance space, thereby to augment said chamber pressure and cause said sealing member to radially expand and engage said wall with increased force, and means to urge said guide member outwardly of the bottom of said body.

6. A hydraulic tappet comprising a hollow cylindrical body, and a plunger unit mounted `for a limited axial movement in said `body and coacting therewith in defining a compression chamber between the: unit and an end of the body, said plunger unit comprising an upper plunger member, a lower plunger member, a spring urging said plunger members for constant axial contact with one another, said upper plunger being provided with an external non-metallic sealing ring in frictional engagement with the internal wall of said body to prevent upward overthrow of said upper plunger relative to said lower plunger and said body, s aid lower plunger member including a guide .and a .sealing element disposed in axially slidable relation to and guided by said guide, which element is in frictional peripheral engagement with said body bore, said sealing element being exposed to said compression chamber and being .radially expansible under hydraulic pressure therein .to seal against said body bore, said -upper and lower plunger members having .pre determined axial clearance therebetween providing a leakby path from said compression chamber which is yclosed by axial engagement .of said plunger members, said scaling element normally having iixed peripheral frictional engagement with .said body .bore prior to said vengagement, but expanding radially under increased pressure in said compression .chamber lwhen said path is closed to grip said body bore with substantiallygreater radial force.

7. A hydraulic .tappet comprising a hollow cylindrical body, and a plunger unit mounted for a limited axial movement in said body and coacting .therewith in defining a compression chamber between the unit and an end 4 of the body7 said plunger imit comprising an upper plunger member .having axially spaced, radially .extending walls guided by .the bode of said body and delning separate communicating primary and secondary reservoirs, a lower plunger member, and a spring urging said plunger members for constant axial contact with one anomer, said lower plunger member including a guide and a sealing element disposed in axially slidable relation to said guide, which .element is in frictional peripheral engagement with said body bore` said sealing .element being exposed to said compression chamber and being radially expansible under hydraulic pressure therein to seal against said body bore, said upper and lower plunger members having predetermined ,axial clearance therebetween providing a leak-by path from said compression lchamber to said primary reservoir which is closed .by axial engagement `of said plunger members, said sealing element normally having lixed peripheral friotional engagement with said body bore prior to lsaid engagement, but expanding radially .under increased ,pressure in said compression chamber when said path is closed `to grip said .body bore with substantially greater radial force.

8. A hydraulic .tappet comprising a hollow cylindrical body and. a plunger unit .mounted for ,a limited axial sliding movement in said body on .one side .of a compres sion chamber therein, said unit .comprising .an integral, one-piece, upper vplunger member having radially extending tlauges slidably guided by `the wall Aof said .body and spaced .axially from one another .to define primary and secondary reservoirs, `a flange between said reservoirs tbeingprovided withone or more passages for commuhication between the reservoirs, and a lower plunger member separate from 'said upper plunger ,member frictonally engaging said .body wall and exposed to pressure in said compression chamber, said lower plunger member being engageable yaxially by Athe lower bange of. said upper member, and means to urge said plunger unit outwardly of thebottom of said body.

-9. A hydraulic tappet comprising ,a hollow cylindrical body and a plunger unit mounted for a limited axial sliding .movement .in said body on one side of a vcornpression chamber therein, said .unit comprising .an integral, one-piece upper plunger member 4having radially extending flanges slidably guided by the wall of said body and spaced axially from one another 'to .deiine primary and .secondary reservoirs, ,a ange between said reservoirs being provided with one or more passages for communication between the reservoirs, and a lower plunger member separate from .said upper plunger member .of relatively .exible material frictionally engaging said body 'wall and .exposed to pressure in said cornpression chamber, said lower plunger member being engageable axially by the lower '.iiange. ,of said upper inember following Ipredeterrniut-:d relative lost motion .of the members, and means to .urge said plunger unit outwardly ofthe .bottom of said body.

l0. A hydraulic tappet comprising a hollow, generally cylindrical body, and a plunger unit mounted for a limited axial sliding movement in said body on one side of a compression chamber in the latter, said unit cornprising `an upper plunger member defining separate, communicating `primary and secondary reservoirs, a lower plunger member, a spring urging said plunger members against one another, and a radially expansible annular sealing member in concentric, axially telescoped rela tion to one of said plunger members and in frictionally engaged, relatively iixed relation to the internal wall of said body, said sealing member providing a passage to by-pass liquid past its associated plunger member and being ninternally exposed to hydraulic pressure in said compression chamber whereby to be expanded radially outwardly into sealing engagement with said internal wall under augmented force when said passage is closed, the other plunger member being axially engageable with said sealing member to close said passage.

ll. A hydraulic tappet comprising a hollow cylindrical tappet body closed at one axial end and having a plunger structure mounted coaxially therein, .said plunger structure comprising a tubular plunger member in engagement with the internal wall of said body and coacting with the latter in .defining a compression chamber beneath the member, a plunger unit above said member and free to shift upwardly relative to the latter and further adapted for axial abutting engagement with said member in response .to a downwardly directed force applied thereto, said member and unit having axially spaced portions at which said abutting engagement takes place after predetermined relative axial movement thereof and there being a liquid flow path from said compression chamber past said plunger member which is at least substantially closed by said abutting engagement, means for urging said plunger structure upwardly from the closed end of said body, and an annular sealing ring on said plunger unit in frictional sealin-g engagement with said internal body wall to lprevent upward overthrow thereof relative to said tubular plunger member and body.

l2. A hydraulic tappet comprising a hollow cylindrical body closed at one axial end and having a plunger structure mounted coaxially therein, said plunger structure comprising a tubular plunger member in engagement with the internal wall of said body and coacting with the latter in defining a compression chamber beneath the member, a plunger unit above said member and free to shift upwardly relative to the latter and 'further adapted for axial abutting engagement lwith said member in response to a downwardly direc-ted force applied thereto, said lmember and -un-it having axially spaced portions at which said abutting engagement takes place after predetermined relative axial movement thereof and there being a liquid -flow path from said compression chamber past said plunger member which is at least substantially closed by said abutting engagement, means vfor urging said plunger .unit upwardly and lout of axial abutting enga-gement with said member when said plunger unit is free to move upwardly, and an annular sealing ring on said plunger unit in frictional sealing engagement with said internal body wall to prevent upward overthrow thereof relative -to said -tubular plunger member and body.

13. A hydraulic tappet comprising a hollow cylindrical tappet body closed at one axial end and having a plunger structure mounted coaxially therein, said plunger structure -comprising a tubular plunger member in engagement with the internal l,wall of said body and .coacting with the latter yin defining a compression chamber beneath the member, a plunger unit above said member and free to shift upwardly relative to the latter and further adapted for axial abutting .engagement with said member in response to a downwardly vdirected force .applied thereto, said ymember and -unit having axially spaced portions at which Said abutting :engagement takes :place after predetermined .relative axial movement .thereof and ,there .being a liquid ow path .from said .compression chamber past said plunger member which is closed by said abutting engagement, said tubular plunger member comprising a plug member received in thel axial bore of said tubular plunger member and a further plunger member adapted for axially abutting engagement with said plug member, means for urging said further plunger member upwardly from the closed end of said body, and an annular sealing ring on said plunger unit in frictional sealing engagement with said internal body wall, said sealing ring being applied to said plunger unit in an annular zone thereof above said 'tubular plunger member, said plunger unit having means subdividing the interior of said body between said sealing ring and said tubular plunger member into primary and secondary reservoirs.

14. A hydraulic tappet comprising a hollow cylindrical tappet body closed at one axial end and having a plunger structure mounted coaxially therein, said plunger structure comprising a tubular plunger member in engagement with the internal wall of said body and coacting with the latter in defining a compression chamber beneath the member, a plunger unit above said member and lfree to shift upwardly relative to the latter and further adapted for axial abutting engagement with said member in response to a downwardly directed force applied thereto, said member and unit having axially spaced portions at which said abutting engagement takes place after predetermined relative axial movement thereof and there being a liquid flow path from said compression chamber past said plunger member which is closed by said abutting engagement, an annular sealing ring on said plunger unit in frictional sealing engagement with said internal body wall to preven-t upward overthrow thereof relative to said tubular plunger member and body, said tubular plunger member comprising a plug member received in the axial bore thereof, 'a further plunger inember adapted for axially abutting engagement with said plug member, and means for urging said further plunger member upwardly from the closed end of said body, said sealing ring being applied to said plunger unit in an annular zone thereof above said tubular plunger member.

l5. A hydraulic tappet comprising a hollow cylindrical body and a plunger unit mounted for limited axial sliding movement in said body and defining a compression chamber between the same and said body, said plunger unit comprising separate upper and lower, axially engageable plungers mounted in predetermined, axially spaced relation to one another to provide a lost motion backlash clearance space of predetermined size therebetween, said upper plunger being provided with an external non-metallic sealing ring in frictional engagement with the internal wall of said body to preventupward overthrow of said upper plunger relative to said lower plunger and said body, said lower plunger including a radially expansible sealing member having a portion of Flexible non-metallic material exposed to pressure in said compression chamber, which sealing member is adapted to flex into sealing engagement with the wall of said body under augmented pressure in said chamber, there being a leak-by path of substantial capacity from said compression chamber through said sealing member which is closed by said plungers upon axial engagement thereof following relative lost motion equal to said clearance space, thereby to augment said chamber pressure and cause said sealing member to radially expand and engage said wall with increased force, and means to urge said lower plunger outwardly of the bottom of said body.

16. A tappet in accordance with claim l5, in which said sealing member comprises a center disk to which said sealing portion is peripherally bonded in a manner enabling said disk to shift axially relative to the remainder of the sealing under said cup chamber pressure, thereby affording an additional backlash increment.

17. A hydraulic tappet comprising a hollow cylindrical body and a plunger unit mounted for limited axial sliding movement in said body and deiining a compression chamber between the same and said body, said plunger nuit comprising separate upper and lower, axially engageablc plungers mounted in predetermined, axially spaced relation to one another to provide a lost motion backlash clearance space ol predetermined size therebetween, said upper plunger being provided with an external nonmetallic sealing ring in frictional engagement with the internal wall of said body to prevent upward overthrow of said upper plunger relative to said lower plunger and said body, said lower plunger including a sealing member exposed to pressure in said compression chamber, there being a leak-by path of substantial capacity from said compression chamber through said sealing member which is closed by said plungers upon axial engagement thereof following relative lost motion equal to said clearance space, thereby to augment said chamber pressure and cause said sealing member to radially expand and engage said Wall with increased force, and means to urge said lower plunger outwardly of the bottom of said body.

lfS. A tappet in accordance with claim 8 in which said plunger members are mounted in predetermined axially spaced relation to one another to provide a lost motion backlash clearance space of predetermined size therebetween, said lower plunger member including a composite, radially expansible sealing member in the form or' a split annular expansible ring having bonded thereto a continuous annular band of exible non-metallic material exposed to pressure in said compression chamber', which sealing member is adapted to tici; into tight sealing engagement with said body wall under augmented pressure in said chamber, there being a leak-by path of substantial capacity from said compression chamber through said sealing member which is closed by said plunger members upon axial engagement thereof following relative lost motion equal to said clearance space, thereby to augment said chamber pressure and cause said sealing member to radially expand and engage said wall with increased force.

19. A tappet in accordance with claim 8 in which said upper plunger member is provided with an external nonmetallic sealing ring in frictional engagement with the internal wall of said body to prevent upward overthrow of said upper plunger member relative to said lower plunger member and said body, said lower plunger member disposed coaxially of said upper plunger member and having a valve element sustained thereby in operative closing relation with one of said reservoirs, said lower plunger member further having an inherently liexble sealing member disposed in telescoped relatively slidable relation to a portion of said lower plunger' member and in radially expansible frictional sealing engagement about its periphery with said body bore, said sealing member expanding radially to grip said body bore with augmented force upon an increase in pressure in said bore upon the movement of said valve element into closing relation.

20. A tappet in accordance with claim 8 in which said upper plunger member is provided with an external nonmetallic sealing ring in frictional engagement with the internal wall ot' said body to prevent upward overllow of said upper plunger member relative to said lower plunger member and said body, said lower plunger member disposed coaxially of said upper plunger member, a valve element sustained by said lower plunger member in operative closing relation to one of said reservoirs, said lower plunger member further having an inherently ilexible, axially flanged, cup-like annular sealing member disposed in telescoped relatively slidable relation to a portion of said lower plunger member and in radially expansible frictional sealing engagement about its periphery with said body bore, said sealing member expanding radially to grip said body bore with augmented force upon an increase in pressure in said bore resulting from the closing oli? by said valve element of said reservoir.

2l. A tappet in accordance with claim 8 in which said lower plunger member' is disposed coaxially of said upper plunger member, a valve element is sustained by said lower plunger member in ,cooperative closing relation to one of said reservoirs, said lower plunger member further having an inherently llexible, axially flanged, cup-like annular sealing member disposed in telescoped relatively slidable relation to a portion of said lower plunger member and in radially expansible frictional sealing .engagement Vabout its periphery with said body bore, said sealing member being provided with a port opening therethrough in an axial direction which is engageable by said upper plunger member to seal the same, said sealing member expanding radially to grip said body bore with augmented force upon Aan increase in pressure in said bore upon the movement of said valve element into operative closing relation with its associated reservoir.

22. A tappet in accordance with claim 8 in which said plunger members are mounted in predetermined axially spaced relation to one another to provide a lost motion backlash clearance space of predetermined size therebetween, said lower plunger member including a composite, radially expansible sealing member in the form of a split annular' expansible ring having bonded thereto a continuous annular band of llexible non-metallic material exposed to pressure in said compression chamber, which member is .adapted to llex into tight sealing engagement with said body wall under augmented pressure in said chamber, there being a leak-by path of substantial capacity from said compression chamber to said sealing member which is closed vby said plunger members upon axial engagement thereof following relative lost motion equal to said clearance space, thereby to augment said chamber pressure and cause said sealing member to radially expand and engage said wall with increased force, said upper plunger member being provided with an external nonmetallic sealing ring in frictional engagement with the internal wall of said body to prevent upward overthrow of said upper Vplunger member relative to said lower plunger member and said body.

23. A hydraulic tappet comprising a hollow cylindrical body and a plunger unit mounted for limited axial sliding movement in said body on one side of a compression chamber therein, said unit comprising on the upper portion thereof upper and lower radially .extending flanges slidably guided by the wall of said body and spaced axially from one another to deline primary `and secondary reservoirs, said lower flange provided with one or more passages for communication between the reservoirs, said upper flange provided with an external non-metallic sealing member in frictional engagement with the internal wall of said body, means on the lower portion of said unit delning said compression chamber, and resilient means associated with said Aunit to urge the same upwardly relative to said body.

24. A hydraulicftappet .comprising a hollow cylindrical body and a plunger unit mounted for limited axial sliding movement in said body on one side of a compression chamber therein, said unit comprising on the upper portion thereof upper and lower radially extending flanges slidably guided by the wall of said body and spaced axially from one .another to dene primary and secondary reservoirs, said lower llange provided with one or more passages for communication between the reservoirs, said upper flange provided with Van external non-metallic sealing member in frictional engagement with the internal wall of Ysaid body, means on the lower portion of said unit delining said compression chamber, said means having a v alve element sustained Vthereby `in operative yclosing relation with one of said reservoirs, `and resilient means .associated with said unit ,to urge .the vsame upwardly relative .to said body.

25. A hydraulic tappet comprising a .hollow cylindrical body and a plunger unit mounted for limited axial sliding movement in said 4body on one side .0f .a compression chamber therein, said unitcomprising on the upper .portion thereof a radially extending flange slidably guided by the wall of Said body, a non-metallic sealing ring mounted externally about said flange and in frictional engagement with ,the internal wall .of -said body, .separate means in the lower ,portion yof said body independent of said plunger unit and in combination with :Said body defining said compression chamber, a .compression .chamber closing element von said unit adapted `to move into its koperative position upon .the downward movement of said unit relative :to said body, and .resilient means ,associated with said separate means .delining 4said compression chamber to urge the same .upwardly .relative to rvsaid body.

26. A hydraulic tappet comprising a hollow cylindrical body `and a plunger unit mounted for limited axial sliding movement in said .body on one side of a compression chamber therein, said unitcomprising lon the upper portion thereof a radially extending tlange slidably guided by the wall of said body, a non-metallic sealing ring mounted externally about said flange and in frict-ional engagement with the internal wall of said body, separate means in the lower portion of :said body independent of said plunger unit and incombination -with said body defining said compression chamber, a valve element sustained by said unit and adapted to move .into operative closing relation with a valve lseat included `in `said separate means defining said compression chamber @in response to downward movement of said unit relative to said body, and resilient means associated with said separate means defining said compression chamber to urge the same upwardly relative to said body.

References Cited in the le of this patent UNITED STATES PATENTS Re. 21,931 Voorhies et al Oct. 21, 1941 1,062,580 Bollee May 27, 1913 2,098,115 Voorhies Nov. 2, 1937 2,108,514 Sommers Feb. 15, 1938 l2,160,257 Appel May 30, 1939 2,250,011 Dayton July 22, 1941 2,325,932 Banker Aug. 3, 1943 2,346,525 Voorhies Apr. 1l, 1944 2,394,354 Barr Feb. 5, 1946 2,438,631 Bergmann Mar. 30, 1948 2,539,877 Voorhies Jan. 30, 1951

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