US2580382A

US2580382A - Hydraulic tappet

Info

Publication number: US2580382A
Application number: US80509A
Authority: US
Inventors: Oscar H Banker
Original assignee: New Products Corp
Current assignee: New Products Corp
Priority date: 1949-03-09
Filing date: 1949-03-09
Publication date: 1952-01-01
Anticipated expiration: 1969-01-01

Description

0. H. BANKER HYDRAULIC TAPPET Jan. 1, 1952 Filed March 9, 1949 INVENTOR. Oscar/i Ban/6 BY mMwm'd/fw Patented Jan. 1, 1952 iiNI ED STATES 2,580,382 HYDRAULIC TAPPET Oscar H. Banker, Era 1 assirn r t New Products Gorporat n, ic go, l a rp r tion-off Delaware Application March 9, 1949, Serial No. 80,509 20 Claims. (01. ize-so) The present invention relates to an improved hydraulic tappet of the type widely employed in automotive engine installations,

Hydraulic tappets new on the. market have certain recognized limitations which it has long been sought to overcome. .In an attempt to hold oil leak-byin the tappet to a minimum, extreme accuracy and closeness. of tolerance in the manufacturing operations are required, incidentally adding materially to thev cost of. production. If the engine oil which is usually employed as the tappet pressure liquid .is not changed, .atsufiiciently frequent intervals, it becomes. heavy and gummy with the result that the check valves and closely fitted, lapped surfaces characteristic of the tappet construction often become clogged and cease to function properly.

Furthermore, the diameter of the parts which subject to hydraulic pressure is kept assmall as possible, with the result that extremely high hydraulic pressures arise, again multiplying the tendency toward leak=by.

It is also a fact that tappets change in their operating characteristics in accordance with the temperature of the engine and vtappet, and re suitant change in size due .to expansion or con? traction of the tappet parts. This change. must be compensated for in a perfect tappeh. vil/Jiore over, inasmuch most existing hydraulic. tappets are designed to take up allcam-tappet baclo lash in an automatic fashion, a new, modified cam shaft is required in order to maintain its original eiiiciency of operation. Frequently a; tappet is notoperable at full efficiency until sev eral cam cycles have been per-iormedand proper operating pressure built up therein. 7

To mytknowledge no one has yet succeeded in devising a hydraulic tappet which meets all of the tappet requirements under the above de scribed conditions or" oil deterioration, variable operating temperature, control of "leakeby and perfect timing with backlash control, yet which can be manufactured reasonably economically;

It is therefore an object 01"- theinvention to provide an improved hydraulic .tappet which ope crates with unimpaired efifioiency under allconditions which it is likely to'meet in the normal life of an automotive motor installation, and. which is not subject to loss of inefiicienoy due to changes in its pressure liquid.

A furtherand more specific object is to provide a hydraulic .tappet which insures minimum oil leak-by in operation, due to :thefact. the pressure in the compression chamber or Seidtappet ectson a surface of irelativelyrlarge area thereby reducing unit pressure on the parts, yet which does not require a high degree of accuracy in the manufacture and interfltting of its parts.

Yet another object is to provide a tappet which automatically compensates for variations in dimension OI itsparts under the effects of temperature changes, thereby maintaining proper valve timing throughout the life of the instai1a-- tion.

Astill further objectis to provide a tappet oi the foregoing type which is instantaneously operable at full efficiency when operation of the motor is started, due to its provisions for constantly mainta n g a s pply im' i liquid availabl a the t pp pre S f The ioregoing 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 an Operation of the vice.

.A sin le em diment of the nve ion is p sented herein tor purpose or illustration, but it will foe appreciated that the invention may also be incorporated other modified forms coining equally Within the scope of the appended claims.

.In. the drawing, the figure is a view on enlarged scale in vertical, axial section through a tappet in accordance with the present invention, showing said tappet in its operative relation to an actuating cam and to a valve stem controlled by the tappet.

Thereiercnce numeral it generally designates the hollow cylindrical body of the tappet, adapted to be slidably mounted in a bore in the engine block. Body it is closed at its lower end by a pressure plate H. adapted to ride on the conventional cam 12 (shown in minimum lift position). Approximately mediallyof its axial length, the body ii] is provided with an annular external groove 13; this, is intended to be positioned in communication with anoil supply passa e leading to the engine tappctbcre, in an n r ly conventional fashions Said tappet body is provided with a radial passage i i leading from the groove I3 toianloil receiving chamber within the hollow interior of the body; aid h m e fi d by the cylindrical internal he e it o t 3 1 5265 body in conjunction with the tappet plunger structure, generally designated which mounted for sliding iflflOVSmfillt in said core.

The plunger stitictill'e referred to includes a hollow, cylindrical, outer plunger member ii which is fitted relatively loosely within the bore l5.. Member Iiisflcharacterized by an'annuiar,

vertically upstanding wall 13 extending above a circumferential groove 19 which is formed on the exterior of the plunger member. Adjacent the lower end thereof said plunger member is circumferentially relieved at 20 for the reception of Said member I! has axial sliding movement in operation relative to a further, inner plunger member 24 of the structure l6, which is disposed in axially telescoping relation thereto, as shown. Said member 24 includes an upper thrust portion 25 provided with an axially disposed, rounded anvil surface 26 which engages the valve stem 21. It also has an upwardly extending, outer, annular abutment 28 which is disposed beneath, a split retainer ring 29 mounted in a groove in tappet body bore l5. Member 24 is further provided with a stem 30 extending downwardly ofits thrust portion 25 and terminating ina cylindrical plunger plug 3|, which plug has a relatively close tolerance sliding reception in an axial bore 32 in the lower portion of the outer plunger member ll. However, this fit is not as close as is commonly regarded as essential in existing high pressure type tappets in order to control leak-by, as will be hereinafter referred to. r

Said. stem plug portion 3i is centrally bored and counterbored from its exposed end to provide an axial passage 33 communicating witha conical valve seat 34. A ball check member35 is mounted within said counterbore, designated 35' for coaction with said valve seat. A further inclined passage 36 communicates the axial plunger passage 33 with an oil reservoir 3'l' in the internal plunger member I! which is defined by the upwardly extending wall 18 of said plunger member.

It should be particularly noted that the overall height of said wall, with reference to the lowermost extremity of its plunger member I1, is slightly less than the overall vertical dimension of the stem 30, with reference to the lower surface of the pressure portion 25 of its plunger member 24. phase of operation, the vertical clearance space 38 between the wall 18 and plunger member 24,

is approximately .012 inch, in a preferred form.

The reservoir 37 maintains a quantity of hydraulic pressure liquid at all times at a substantial level above the passages 33, 36, through which said oil is adapted to flow on the return stroke of the tappet. The oilis supplied to this reser voir past the clearance space 38 through one or more axially extending grooves 39 which are formed on the outer surface of the wall 18 of plunger member I1 and which communicate at their lower ends with the circumferential groove recessed at 4| for an axial abutting engagement with the lower surface of the inner plunger member 24. It is also provided with a downward ex- When the tappet is in a dwell.

This

tension 42 about which a coiled compression spring 43 is disposed, said spring acting between the bottom plate ll of the tappet body and the flange 40 of member 40. An inclined passage 44 in said member leads from the upper surface of the member 40, adjacent the stem counterbore 35 in which the ball check 35 is housed, to the exterior of said lower plunger member. Thus the stem passages 33, 36"are adapted to be communicated with a compression chamber 46 in the tappet I0, defined between the lower portion of the plunger structure l6 and the lower portion of the body. The lower plunger member 40 is merely guided loosely in bore I5.

Assuming that the tappet body I5 is properly fitted in a bore in the engine block, with its pressure plate ll riding the cam l2 and its anvil surface 26 engaging the valve stem 21, that the external groove I3 is supplied with oil under pressure, that the reservoir 3'! has been thus filled with oil through the vertical passages 39 and the clearance space 33, and that this oil has been supplied under pressure to the compression chamber 46 through the passages 36, 33 and 44, then the relationship of the main components of plunger structure l6 and tappet body It] at the dwell phase of tappet operation is approximately as indicated in solid lines in the figure. The extension 42 of the lower plunger member 40 is spaced approximately inch from the body pressure plate I i.

In operation, as the lobe of cam I2 rises, exerting force on the pressure plate II, the stem 30 of plunger member 24 tends to slide relative to the internal bore 32 of outer plunger member ll, thus exerting pressure against the lower plunger member 40 and spring 43. The resultant slight movement of said member into the compression chamber 46 causes the oil therein to flow upwardly through passage 44, lifting the ball check 35 into sealing relation in the passage 33. Further escape of liquid from compression chamber 46 to the reservoir 31 is prevented.

However, the plunger structure It continues to advance, relatively, into the compression chamber 46, increasing the pressure therein, which thus becomes effective on the lower surface of the cylindrical lower portion of plunger member l1. Since this member is absolutely sealed by the O-ring 22, preventing escape of oil around said plunger member, the latter is bodily lifted while the spring-urged member 40 is being held depressed by plunger stem 30. This upward movement of the member I! is relative to the body It and the stem 36. Hence member 4! takes up the clearance 38 between the plunger members I1, 24, causing member I! to abut member 24. Thereafter the full hydraulic pressure of the compression chamber is effective across the entire transverse area of the plunger member l1, stem 39 and O-ring 22 to elevate the anvil 26 and valve stem 21. Inasmuch as this area is large, the unit pressure is relatively small. In fact, the maximum pressure in compression chamber 46-during operation of the tappet is approximately a third of that involved in the operation of present-day hydraulic tappets. This factor naturally makes possible a much more effective control of leak-by.

As in many hydraulic tappet structures, it is necessary to make provision for the displacement of a slight amount of operating liquid from the compression chamber 46 when the overall length of the plunger-structure 16 increases as: the result of heat expansion, Such compensa .conventional high pressure types.

non ls-accomplished in two ways in the present tappet. Ordinarily, any slow and. gradual heat expansion is compensated constantly during the dwell" phases because the ball check 35 is :always open atsaid dwell phase of operation and the liquid volumes adjust themselves automatically. This .is trueeven with an absolute, liquid tight seal between plunger :bore 32 and the relatively slidable stem 33. In the event a sticky valve developes and becomes stuck in an open position, whereas a conventional hydraulic tappet so operates that its plunger-would follow and maintaincontact with the valve stem, hold ing-the valve in stuck position even-after it had freed itself, this possibility is prevented in the present construction by reason of the substantially less close fit of the-stem 39 in the bore 32 than in conventional existing tappets. Since the pressure in chamber-d6 is low, and since the diameter involved small, the fit between said bore and stem need not be as close as the Accordingly, after the stuck valve frees itself and the full force of the spring 33 is effective on plunger member 2d, the liquid will escapearound stem til while ball check 35 is closed until the valve seats itself properly. The-nOrmaloperating cycle of the tappet then resumes.

The above described tappet can be installed ina standard'motor in association with a-standard cam shaft, it being onlynecessary-to provide a supply of oil to the tappet from themotor lubrication pressure system. The functioning "and timing of the motor are perfectly maintained because the gap-or clearance '38 compensates for the backlash which is, at present, built into said cam shaft as a standard matter of design.

Inasmuch as this clearance is taken up gradually and hydraulically 'in 'a chamberwhich is full "of oil, there is no noticeable noise attending the physical contacting of the plunger members I1, 24. Furthermore, in view "of the sealing action of the O-ring against bore l5, the latter surface need only be areamed surface; the'outer-surface of plunger member I"! may be 'centerless ground with generous tolerances. No 'appreciabledifierence in tappet perform ance is occasioned by *hot-or cold *motor operation,"or hot or-cold oil. The generous clearance between the upper plunger member "24 and'the body bore 152180 enables the oil to constantly circulate past these surfaces and carry out of'the tappet any vapor "or air bubbles that might-enter the system.

As stated above, in view 'of'the fact that the pressure incompressionbhamber 8B is low, the fit of stem portion 3! in the bore 32 need not be as "close as in'c'onventional 'tappet construction, in order to'control leak-by. This advan tage of efficient leak-by control is further contributed to by the smallness of diameterofsaid stemportionand bore'for areiatively small total leakby area is presented.

It will be noted further that -the passage -36 in stem 36 is arranged some distance'above the bottom of reservoir 1, which insures that any impurities-or sludge in the'oil which accumulatein the bottom of the -reservoir will not clog said discharge or becarried therethrough into compression chamber 46. Moreover, the eonstant'sliding action of the stem portion '39 throughout a distance of approximately -.012 inch ;at every oy'cle'of tappet operation insures'that these surfaces -be kept cleanand-open regardless of how dlrvyorisludgy thepil inay become. i

. "Generally; and this applies to the "tappet' as a whole, the avoidance of close tolerances in the manufacture ofth'e abovezdescribed tappet contributes substantially to a :low cost of production.

I claim:

-1. A hydraulic tappet comprising .a hollow tubular tappet body, a plunger 'structurelslidable insaid body and :coac'ting therewith to define a liquid receiving compression-chamber, said-structure comprising inner :and outer plunger members guided for-axial sliding movement in said body and mounted :in axially shiftable :relation to one another, springnrged rmeans acting .between said plunger. structure and body .to maintain their respective engagement with a valve stem and actuatingzcam, said plunger members being "normally disposed-inpredetermined axially spaced relation for axial abutting engagement following a predetermined relative axial travel, both of said plunger members being subject to pressure in said compression chamber tending to urge said members in the same axial direction and one thereof being movable in response to said pressure intoabutting-engagement with the other member after saidpredetermined relative travel, means providing a liquid-tight seal be: tween said one of said-plunger members and said body, and means providing .a one-way liquid fiow passage between lsaidcompression chamber and the side of said plunger structure opposite said chamber, one of said iplungersmembers having a bore parallelingtthe axis thereof and the other plunger member having a portion slidably received'in said bore with relatively small radial clearance to define an annular leak-by passage from said pressure chamber, which leak-by passage is self-cleaning in character due to said relative axial travel and sliding engagement of said-last named-plunger member portion in said last named plunger member bore.

1 2. A hydraulic tappet comprising va hollow tubulartappet body, a plunger structure, slidable in said body and coacting therewith to define .a liquid receiving compression chamber, said structure comprisingxinner and outer plunger members guided for axial sliding lmovementin isaid body and mounted in .axially-shiftable relation to one another, spring urged means acting between said plunger structure and body to maintain engagement thereof with a valve stem and actuating 0am, said plunger members being normally disposed in predetermined axially spaced relation for axialabutting engagement following a predetermined relative :axial travel, both of said plunger members being subject to the pressure said compression chamber tending to'urge said members in the same axial direction and the outer memberibeing movable in response to said pressure sintorabutting en agement with the inneiumemberiafter.sald :predeter-- mined relative travel, means providing a liquidtight seal betweensaidouter plunger member and said body, and means providing a one-way liquid flow passage between said compression chamber and the 'sideof said plunger structure opposite said chamber, both members being pressure-shifted after said abutting engagement thereof, one of said plunger members having a boreparalleling the axis thereof and the other plunger member having a portion slidably received in said, bore with relatively small radial clearance to define :aniannuiar leak-by passage from said pressure 'achamber, which leakeby 11125? .saee isnselr-lcleanins in 'zcharacter. due to said relative axial travel and sliding engagement of said last named lunger member portion in said last named plunger member bore.

3. A hydraulic tappet comprising a hollow tubular tappet body, a plunger structure slidable in said body and coacting therewith todefine a liquid receiving compression chamber, said structure comprising inner and outer plunger .members guided for axial sliding movement in said body and mounted in axially shiftable relation to one another, spring urged means acting between said plunger structure and body to maintain engagement thereof with .a valve stem and actuating cam, said plunger members being normally disposed in predetermined axially spaced relation for axial abutting engagement following a predetermined relative'axial travel, and both being subject to the pressure in said compression chamber tending to urge said members in the same axial direction and the .outer member being movable in response to said pressure. into abutting engagement with the other after said predetermined relative travel, means providing a liquid-tight seal between said outer plunger member and said body, and means providing a oneway liquid flow passage between said compression chamber and the side of said plunger structure opposite said chamber, both members being pressure-shifted after said abutting engagement thereof, one ofrsaid'plunger members having a bore paralleling the axis thereof and the other plunger member having aportion slidably received in said bore with relatively small radial clearance to. define an annular leak-by passage from said pressure chambenwhich leakby passage is self-cleaning in character due to said relative axial travel and sliding engagement of said last named plunger member portion in said last named plunger memberbore.

4. A hydraulic tappet comprising a hollow tubular tappet body,.a plunger structure slidable in said body anclcoacting therewith to define a liquid containing compression chamber, said structure comprising an outer plungermember guided for axial sliding movement in said body, an inner plunger member guided for axial shiftng movement in .said' outer member and a further member on the compression chamber side of said structure normallydisposed inaxial abutting engagement with, said, inner and, outer plunger membe'rsthereof, a spring normally acting to maintain said abutting engagement, said inner and outer plunger members being normally disposed in predetermined axially spaced relation to one another and both being subject to pressure in saidcompression chamber tendingto move the same in the same axial direction, means providing a liquid-tight seal between said plunger structure and said body, and means providing a one-way liquid flow passage between said compression chamber and the side of said plunger structure opposite 'said chamber, said outer plunger member having separating movement away from said further member and axially relative to said inner. plunger member under increased pressure in said chamber saidinner and outer members'being shiftable as unit under said increased pressure after said lost motion shifting.

5. A hydraulic tappet. comprising a hollow tubular tappet body, a plunger structure slidable in said body and coacting therewith to define a liquid containing compression. chamber, said structure comprising: an outer iplunger member guided for axialisliding movementiri said body;

an inner plunger member guided for axial shift ing movement-in said outer member and a further member on the compression chamber side of said structure normally disposed in axial abutting engagement with said inner and outer plunger members thereof, a spring normally acting to maintain said abutting engagement, said inner and outer plunger members being normally disposed in predetermined axially spaced relation to one-another ior abutting engagement after a predetermined relative axial shifting movement and both beingsubject to pressure in said compression chamber tending to move the same in the same axial direction, means providing a liquid-tight sealbetween said plunger structure and said body, and means providing acne-way liquid flow passage between said compression chamber and the side of said plunger structure opposite said chamber, said outer plunger memberhaving separating movement relative to said further member and into abutting engagement with said inner plunger member under increased pressure in said chamber, said inner and outer members being shii'table as a unit under said increased pressure aiter said lost motion shifting and engagement.

6. A hydraulic tappet comprising a hollow tubular tappet body, a plunger structure mounted relatively loosely in said body for axial sliding movement therein and coacting therewith to define a compression chamber, said structure comprising an outer tubular plunger member guided for axial sliding movement in said body and provided with an abutment element, an inner plungermember mounted in axially slidable relation to said first plunger and having a portion normallylocated in predeterminedly spaced relation to said abutment element, and a further member on the compression chamber side of said structure normally disposed in axial abutting engagement with said inner and outer plunger members thereof, a spring urging said'plunger structure for engagement with a valve stem and actuating cam, both said plunger members being subject to the pressure of said compression chamber tending to urge the same in the same axial direction and said outer member bein'g'mov'able relative to said inner and further members in response tov increase in said pressure, whereby to axially engage said abutment element with said inner plunger portion after traversing said predetermined spacing between said plunger members, means providing a liquid-tight seal between said outer plunger member and said body, and means providing a one-way liquid fiow passage between said compression chamber and said reservoir; I

7. A hydraulic tappet comprising a hollow tubular tappet body, a plunger structure mounted relatively loosely insaid body for axial sliding movement therein and coacting therewith to define a compression chamber, said structure comprising an outer tubular plunger member guided for axialsliding movement in said body and provided with an annular abutment wall affording a liquid; reservoir, an inner plunger member mounted in axially slidable relationto said first plunger and having a portion normally located in predeterminedly spaced relation to said abutment wall, and a further member on the compression chamber side of said structure nor mally disposed in axial abutting engagement with said inner and outer plunger members thereof. a springurging said plunger structure for engage-'- ment with a valve fitemrand actuating cam.- said plunger members being. subject to the pressure of said compression chamberand said outer member being movable relative to said inner and further members in response to increase in-said. pressure, whereby to axially engage said annular abutment wall with said inner plunger portion after traversing said predetermined spacing between said plunger members, means providing a liquid-tight seal between said outer plunger mem ber and said body, and means providing a oneway liquid flow passage between said compression chamber and said reservoir.

8. A hydraulic tappet comprising a hollow tubular tappet body, a plunger structure mounted relatively loosely in said body for axial sliding movement therein and coacting therewith 516.- fine a compression chamber, said structure comprising an outer tubular plunger member guided for axial sliding movement in said body and provided with an annular abutment wall affording a liquid reservoir, :an inner plunger member mounted in axially slidable relation to said first plunger and having a portion normally located in predetermi-nedly spaced relation to said abutment wall, and a further member on the compression chamber side of said structure normally disposed in axial abutting engagement with said inner and outer plunger members thereof, a spring urging said plunger structure for engagement with a valve stem and actuating cam, said plunger members being subject to the pressure of said compression chamber and said outer member being movable relative to said inner and further members in response to increase in said pressure, whereby to axially engage said annular abutment wall with said inner plunger portion after traversing said predetermined spacing between said plunger members, means providing a liquid-tight seal between said outer plunger member and said body, and means providing a oneway liquid flow passage between said compression chamber and said reservoir, said passage opening to said reservoir substantially above the bottom of the latter.

9. A hydraulic tappet comprising a hollow tubular tappet body, a plunger structure mounted relatively loosely in said body for axial sliding movement therein and coacting therewith to define a compression chambensaid structure comprising an outer tubular plunger member guided for axial sliding movement in said body and provided with an abutment element, an inner plunger member mounted in axially slidable relation to said first plunger and having a portion normally located in predeterminedly spaced relation to said abutment element, and a further member on the compression chamber side of said structure normally disposed in axial abutting engagement with said inner and outer plunger members thereof, a spring urging said plunger structure for engagement with a valve stem and actuating cam, said plunger members being subject to the pressure of said compression chamber and said outer member being movable relative to said inner and further members in response to increase in said pressure, whereby to axially engage said abutment element with said inner plunger portion after traversing said predetermined spacing between said plunger members, means providing a liquid-tight seal between said outer plunger member and said body, and means providing a one-way liquid flow passagebetween said compression chamber and said reservoir,

said inner and outer members having portions 10 slidably associated with one another with relativcly small radial clearance. to safiord a leak-by passage from said pressure chamber.

10. A hydraulic tappet comprising a hollow tubular tappet body, a plunger structure mounted relatively loosely in said body for axial sliding movement therein and coacting therewith to define a compression chamber, said structure comprising an outer tubular plunger member guided for axial sliding movement in said body and provided with an annular abutment wall aifording a liquid reservoir, an inner plunger member mounted in axially slidable relation to said first plunger and having a portion normally located in predeterminedly spaced relation to said abutment wall, and a further member on the compression chamber side of said structure normally disposed in axial abutting engagement with said inner and outer plunger members thereof, a spring urging said plunger structure for engagement with a valve stem and actuating cam, said plunger members being subject to the pressure of said compression chamber and said outer member being movable .relative to said inner and further members in response to increase in said pressure, whereby to axially engage said annular abutment wall with said inner plunger portion after traversing said predetermined spacing between said plunger members, vmeans providing a liquid-tight seal between said outer plunger member and said body, and means providing a one-way liquid flow passage between said compression chamber and said reservoir, said inner and outer members having portions slidably asso ciated with one another with relatively small radial clearance to aiiord a cleak by passage from said pressure chamber.

11. A hydraulic tappet comprising a hollow body and a plunger structure slidably mounted in said bod-y, said plunger structure comprising a pair of plunger members in telescoping relation to one another and adapted for axial abutment with one another in the operation of the tappet, means operatively engaging both of said members in a predetermined relative position thereof, the effective'length of one of said plunger members with reference to said engaging means being slightly greater than that of the other to provide'an axial space between said members in said predetermined relative position thereof, means subjecting one of said members to hydraulic pressure in the operation of the tappet to shift the same axially the distance of said space relative to the other for said axial abut tingengagement, and spring means acting on said engaging means to urge the same and said other member axially in the same direction, said plunger members and engaging means being mounted in said body for axial movement relative to one another.

12. A. hydraulic tappet comprising a body and a plunger structure slidable therein, said plunger structure comprising a hollow plunger member of substantial diameter, a further plunger member provided with an axially extending stem portion of relatively small diameter in internalsmall clearance telescoping engagement with said first named plunger member, said plunger members defining an annular reservoir between said stem portion and the wall of said hollow plunger member and an annular leak-by path externally of said stem portion, and means providing a one-Way valve controlled passage through said stem portion. a

13. A hydraulic tappet comprising a hollow external body and a plunger structure slidable therein, said plunger structure comprising a hollow barrel-like plunger member, a further plunger member of generally T-shaped outline in slidable engagement with the wall of said tappet to seal the latter, said first named plunger member having an axially extending bore in which'the stem portion of said further plunger member is slidably received, said plunger members defining an annular reservoir therebetween receiving and confining pressure liquid supplied to the tappet body and an annular leak-by path externally of said stem portion, and means providing a oneway valve controlled passage through said stem portion.

14. A hydraulic tappet comprising a hollow tubular tappet body, a plunger structure slidable in said body on one side of a liquid receiving compression chamber therein, said structure comprising a pair of plunger members mounted in axially shiftable relation to one another, said plunger members being normally disposed in predetermined, axially spaced relation for axial abutting engagement following a predetermined relative axial travel, both of said plunger members being operatively subject to pressure in said compression chamber tending to urge them in the same axial direction and one thereof being movable axially in res onse to said pressure into abutting engagement with the other after said predetermined relative travel, and means providing a one-way passage through one of said plunger members communicating with said compression chamber, said means including a alve element movable relative to both said members.

15. A hydraulic tappet comprising a hollow tubular tappet body, a plunger structure slidable in said body on one side of a liquid receiving compression chamber therein, said structure comprising a pair of plunger members mounted in axially shiftable relation to one another, spring means acting to maintain engagement of said plunger structure and body with external actuated and actuating members, said plunger members being normally disposed in predetermined, axially spaced relation for axial abutting engagement following a predetermined relative axial travel, both of said plunger members being operatively subject to pressure in said compression chamber tending to urge them in the same axial direction and one thereof being movable axially in response to said pressure into abutting engagement with the other after said predetermined relative travel, and means providing a one-way passage through one of said plunger members communicating with said compression chamber, said means including a valve element movable relative to both said members.

16. A hydraulic tappet comprising a hollow tubular tappet body, a plunger structure slidable in said body on one side of a liquid receiving compression chamber therein, said structure comprising inner and outer plunger members mounted in axially shiftable relation to one another, said plunger members being normally disposed in predetermined, axially spaced relation for axial abutting engagement following a predetermined relative axial travel, both of said plunger members being exposed to pressure in said compression chamber tending to urge them in the same axial direction and one thereof bein movable axially in response to said pressure into abutting engagement with the other after. said predetermined relative travel, and means p viding a one-way passage through one of said plunger members communicating with said compression chamber, said means including a valve element movable relative to both said members. -17. A hydraulic tappet comprising a .hollow tubular tappet body, a plunger structure slidable in said body on one side of a liquid receiving compression chamber therein, said structure comprising inner and outer plunger members mounted in axially shiftable, slidably engaging relation to one another, said plunger members being normally disposed in predetermined, axially spaced relation for axial abutting engagement following a predetermined relative axial travel, both of said plunger members being exposed to pressure in said compression chamber tending to urge them in the same axial direction and one thereof being movable axially in response to said pressure into abutting engagement with the other after said predetermined relative travel, there being a restricted leak-by passage between the slidably engaging surfaces of said plunger members for the controlled escape of liquid under pressure from said compression chamber, and means providing a one-way passage through one of said plunger members communicating with said compression chamber, said means including a valve element movable relative to both said members. I

18. A hydraulic tappet comprising a hollow tubular tappet body, a plunger structure slidable in said body and coacting therewith to define a liquid receiving compression chamber, said struc' ture comprising inner and outer plunger members mounted in axially shiftable relation to one another, said plunger members being normally disposed in predetermined, axially spaced rela tion for axial abutting en agement following a predetermined relative axial travel, a source of pressure liquid, and means providing a one-way liquid flow passage between said compression chamber and said source, said means including a valve element movable relative to both of said plunger members, said members being exposed to pressure in said compression chamber tending to urge them in the same axial direction and one thereof being movable axially in response to said pressure into abutting engagement with the other after said predetermined relative travel.

19. A hydraulic tappet comprising a hollow tubular tappet body, a plunger structure slidable in said body and coacting therewith to define a liquid receiving compression chamber, said struc ture comprising inner and outer plunger iris-rm" bers mounted in axially 'shiftable, slidably engag-" ing relation to one another, said plunger members being normally disposed inpredetermined, axially spaced relation for axial abutting engagement following a predetermined relative axial travel, a source of pressure liquid, and means providing a one-way liquid flow passage between said compression chamber and said source, said means including a valve element movable relative to bothiof said plunger members, said members .bein exposed to pressure in said compression chamber tending to urge them in the same axial direction and one thereof being movable axially in response to said pressure into abutting engagement with the other after said predetermined relative travel, there being a restricted leak-by passage between the slidably engaging surfaces of said plunger members for the controlled escape of liquid underpressure from said compression chamber to said source.

- 20. A1 hydraulic tappet comprising a hollow tubular tappet body. a plunger structure shdable in said body on one side of a liquid receiving compression chamber therein, said structure comprisin inner and outer plunger members mounted in axially shiftable, slidably engaging relation to one another, spring means acting to maintain engagement of said plunger structure with external actuated and actuating members, said plunger members being normally disposed in predetermined, axially spaced relation for axial abutting engagement following a predetermined relative axial travel, a source of pressure liquid, and means providing a one-way liquid flow passage between said compression chamber and said source, said means including a valve element movable relative to both of said plunger members, said members being exposed to pressure in said compression chamber tending to urge them in the same axial direction and one thereof being movable axially in response to said pressure into abutting engagement with the other after said predetermined relative travel, there bein a restricted leak-by passage between said plunger members for the controlled escape of liquid under pressure from said compression chamber.

OSCAR H. BANKER.

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

UNITED STATES PATENTS Number Name Date Re. 21,931 Voorhies et a1 Oct. 21, 1941 1,248,405 Russell Nov. 27, 1917 2,096,257 Moorhouse Oct. 19, 1937 2,098,115 Voorhies Nov. 2, 1937 2,108,514 Summers Feb. 15, 1938 2,116,749 Daisley May 10, 1938 2,140,826 Bettison Dec. 20, 1938 2,220,336 Johnson et al Nov. 5, 1940 2,250,752 Dayton July 29, 1941 2,468,332 Johnson Apr. 26, 1949