US2580380A - Hydraulic valve tappet - Google Patents

Description

0. H. BANKER j Jan. 1, 1952 DRAULIC VALVE TAPPET Filed Feb. 25, 1946 INVENTOR. O5 Caz/"19 flan/26f,

Patented Jan. 1, 1952 HYDRAULIC VALVE TAPPET Oscar H. Banker, Evanston, Ill., assignor to New Products Corporation, Chicago, 111., a corpora:

tion of Delaware Application February 25, 1946, Serial No. 649,931

18 Claims.

This invention relates to improvements in a hydraulic tappet for an engine valve wherein liquid is supplied under pressure from the engine lubrication pump to thetappet, the latter having simple and inexpensive, but unfailingly operative, internal provisions for utilizing said liquid as a hydraulic pressure medium to maintain unfailing contact of the tappet with the valve stem, preventing noise at the meeting thrust surfaces of the valve stem and tappet.

It is an object of the invention to provide a hydraulic tappet and valve assembly, the valve and tappet of which are constructed and arranged whereby the pressure liquid utilized in the operation of the tappet is.circulated through the valve as an agency for cooling the latter.

A still further object is to provide an improved hydraulic engine tap-pet of the type described, including liquid controlled internal parts con- :structed and arranged in a manner to be selfcleaning and self-priming in operation.

Another object is to provide a hydraulic tappet which automatically replenishes its control liquid and assuming operating conditionrupon its first stroke in the starting of the engine.

A still further object is to provide a hydraulic tappet having an absolutely sealed plunger preventing escape of liquid externally thereof and an internal escape passage of comparatively small and restricted area or capacity.

Another object is to provide a hydraulictappet of simplified and inexpensive construction, having a novel arrangement of parts which eliminates the costly machining operations entailed in the close tolerance fitting of certain coacting parts, as in previous devices of this type.

The foregoing statements are indicative in a general way of the nature of the invention, but

other and more specific objects will be apparent to those skilled in the art upon a full understanding of the construction and operation of the device.

- A single embodiment of the invention is presented herein for purpose of exemplification, but it will be appreciated that the invention is susceptible of incorporation in other modified forms coming equally within the scope of the appended claims. 7

In the drawings,

Fig. 1 is a fragmentary view in central vertical section through a valve and tappet assembly in accordance with the present invention, showing said assembly as operatively mounted in an engine block; and I Figs. 2 and 3 are enlarged transverse sections taken respectively on lines corresponding to lines 2-2 and 3-3 of Fig. 1.

This invention pertains to improvements in a poppet-type valve and to a coacting tappet therefor, including hydraulically actuated provisions whereby the tappet is maintained in continuous end thrust engagement with the valve stem in the novel and improved assembly of the elements. This engagement is preserved regardless of the position of the valve and without knock or noise incident to the lifting of the valve. Associated with the hydraulic operating elements of the tappet, the assembly includes an internal coolant circulation line in the valve, aligned and communicated with the tappet and supplied with operating liquid from the latter for use as a valve coolant. The operating and cooling liquid is supplied from and returned to the engine crank case, employing suitable pumping means such as are well known in the art. The improvements referred to are incorporated in the valve and tappet assembly by means or" a minimum of simply operating elements, and no attention thereto is required following installation, since the tappet structure is unfailingly self-cleaning, as well as self-priming upon commencement of operation of the engine. arrangement of elements eliminates the need for close tolerance'fitting of certain liquid escape surfaces in the tappet, which was required in previous tappets of this type, materially lessening the cost of production.

Referring to the drawings, in Fig. 1 I illustrate the assembly of a poppet-type valve, generally designated l0, and a tappet therefor generally designated H, in an engine cylinder block l2. This block and its associated structure include a bushing or insert I3 in which the stem IQ of valve I0 is guided for longitudinal reciprocating movement, and a beveled inserted seat 15 against which the beveled mushroom head E6 of the valve is engageable in operation. Valve it controls flow of fuel vapor through seal 55 and passage P, in well-known manner.

A novel The valve I is of hollow construction, being fabricated of a plurality of parts hydrogenbrazed or otherwise secured together in the following manner. The valve head I6, of heatresisting alloy steel, is secured to the radially and longitudinally flaring end of an elongated external tube 2I of medium carbon steel which constitutes the outer member of the stem I4. At the opposite end of the valve stem a thrust nose 22, which supports stop ring washer I8, has a length of secondary tubing 23 axially secured thereon concentric with tube 2! and in alignment with an axial port 24 through nose 22. A. coolant is supplied to port 24 in the operation of the valve assembly, as will be de-" scribed. Since the tube 23 is of less diameter than tube 25, an annular coolant return passage 25 is defined around the secondary tube.

Passage 25 and inner tube 23 communicate adiacent the valve head with the hollow interior of the latter; and in order :to insure adiffusion and transverse now of a liquid-coolant against the under side of the head :IG-during operation of the valve I provide a perforated annular spider 26 surrounding the upper end of secondary tube 23 and secured thereto during assembly, or to the flared end '20 of stem tube "2!. i This spider deflects coolant liquid which is supplied upwardly through the interior of inner tube 23 in a lateral or radially outward direction against and over the inner area of head I6 prior to return of the fluid through the spider into the annularreturnpassage 25. SpiderZE may also serve to locate and support tube 23'1centrally of outer tube ZI.

Said outertube is provided with a radial hole 2! adjacent its lower end, through which coolant in annular passage 25 returns to the engine crank case.

The coolant referred-to is preferably a good grade of lubricating oil of appropriate viscosity, as employed in the standard engine lubricating system, and serves likewise as the operating liquid for thehydraulically controlled tappet II now to bedescribed.

'Iappet II comprises an outer, elongated, hollow cylindrical body 28 closed at itslower end and provided. with a hardened thrust member 29 at that end which rides on the valve actuating cam 33 in a well known manner. guided for its axial stroke in an enlarged boss 3I of the engine block and in turn has a tubular thrust member 32 mountedfor axial sliding movement in its cylindrical bore. A relatively large tolerance for said sliding ispermitted, be-

tween the thrust member and body 28, which makes possible an inexpensive manufacturing operation at the meeting surfaces of these parts. At the same time sticking of member 32 in the body 28is prevented by reason of the generous clearance.

An O-ring 33 disposed in anexternal annular groove in the thrust member 32 provides an absolute seal between said member and the internal surface of body 28 which prevents escape of oil between the member and body above said O-ring under any circumstance in the operation of the valve and tappet assembly.

The thrust member 32 is of elongated cylindrical shape and at its upper end has fixedly secured thereon a thrust transmitting nose' 34 which constantly and snugly engages the nose 22 on valve stem I4. Member 32 is axially bored out at its upper end to provide a main liquid reservoir 35 and the nose 34' is axially'ported at I? and spring or Body 28 is 36 for the communication of the liquid under pressure in said reservoir 35 through port 33 to the internal or secondary tube 23 of the stem. Accordingly, tappet operating liquid, under the pressure existing in tappet reservoir 35, circulates freely through the valve Ii! to cool the head thereof, then returns through annular passage 25 of the'stem, likewise cooling said stem, and

discharges out the radial hole 27. 7

Operating liquid (i. e. engine oil) is pumped under pressure to the reservoir 35' through a pressure line 31 which is tapped in an opening in boss 3I,' in communication with an annular liquid distribution'groove 38 on the interior surface of the boss-bore. The tappet body 28 has a radial port 39- communicating with said annular groova-saidgroove being of sufiicient axial di mension that communication of the port 39 therewith will be maintained in any vertical position of the tappet body. The cylindrical thrust member-32 has :the-outer-periphery thereof relieved for a substantial vertical distance at ,0 to provide an annular'clearance space through whichliquid supplied from port 33 may circulate, passing through a further intake port 4B adjacent thetop of space 40 into the reservoir '35. This liquid is pumped under a pressure of about 30 pounds per square inch.

Immediately beneath the reservoir 35 the tappet thrust member 32 has a transverse partition provided with a central' bore coaxial with the member. This bore has axial sliding engagement with a hollow upstandingliquid passage tube 43, thereibeing. a close: sliding fit'between' the parts. The tube 43 is urged downwardly against the bottom 'of'the'hollow cylindrical tappet body 28 bya coil spring 44 encircling the tube and abutting transverse partition member '42 and the enlarged lower-end of the tube. A ball check valve 'disposed-in said enlarged end coacts with the tube in controlling the flow of liquid under pressure from the reservoir 35 into a high pressure chamber 46, which is defined between partition 42 and the internal end of body 28. O-ring 33 prevents return flow of liquid above said O-ring between the relatively loosely engaging surfaces of the body 28 and thrust member 32 i. e., between the O-ring and supply port 39 in the body. However, escape of liquidunder excessive pressure-in chamber 46, as well'as air'and vapor, and return thereof to the reservoir. 35 may take place be tween the coacting surfaces of the tube 43 andthe bore in partition 42'. Likewise, a small bleeder' passage 41 is provided-from the O-ring groove to the bore in which the tube 43 isreceived, for the return of any air or vapor present beneath O-ring 33, i. e., on the side thereof opposite liquid supply port 39. Thetappet is' normally installed with the spring 44oompresseusomewhat. A split ring encircling the nose 34 and received in an internal groove in the tappet=body 2s serves to limit axial separation of the tappet and body.

In operation, the spring 44 constantly urges tube 43 and the thrust member 32 in opposite directions, maintaining contact of the latter with valve stem I4 even when pressure is lackin in chamber'35. When the-engine is standing idle, some of the valves II! will be in fully open position and some partly open. In such case spring I9 urges thrust member 32 downwardly in body 28 so that the lower edge of the latter engages the closed bottom of the bore in said body. When the engine is cranked to start its operation, turning' of cam 39resu1ts in elimination of the pressure exerted by spring la on member 32. At-that at a controlled volume and rate.

time spring '44 urges thrust member 32 in the opposite direction, i. e., upwardly in Fig. 1, causing liquid to besucked from reservoir 35 through 'the'in'terior of tube 43 into the lower pressure chamber 46, passing check valve 45. Said valve 'willprevent liquid flow through the interior. of tube 43 in the reverse direction. Hence, even though the engine has not commenced operation and liquid is not being pumped through line 31,

operating liquid is'present in the pressure chamber 46, supplied from oil held in reserve in the reservoir 35. For this reason, the entrance port 4| to said reservoir is placed as high as possible in the wall thereof; the reservoir is always filled with sufficient liquid to supply the bottom pres- .sure chamber 46; -It will be appreciated that the tappetis self-priming by reason of the above features, and no matter how long the engine stands idle, it immediately primes itself from the reserve of operating liquid at hand. In the event too much liquid escapes from the pressure chamber during the operation of theengine at certain speeds it is immediately replenished upon a spring-urged suction stroke of member32 in the manner described above.-

Rotation of cam results in transmission of pressure from the body, through the trapped volume of liquid under pressure in lower chamber 46 to. the thrust member 32 and thrust nose 34 to the valve stem, in a way which will be apparent. *Duringengine operation, heating of valve I6 and consequent elongation thereofnaturally results-in-incre'ase of pressure on the liquid trapped in chamber. This liquid cannot escape externally ofthrustmember 32, by reason of the absou lute seal at O-ring 33, nor can it pass check valve 45. Therefore; there must be other provisions for escape of 'oil and relief of the excesspressure. This is accomplished by seepage or leakage of the liquid between tube 43 and the bore in partition Previous hydraulic tappets of this general type have been characterized by the use of coacting liquid escape surfaces of relatively large circumference through which the liquid escapes in the operation of the tappet, i. e., of the order in size of the am'acent diameters of member 32 and body 28. In'order to accomplish a controlled escape of said liquid, it has been necessary to provide a very close tolerance or clearance between these relatively large circumference surfaces. This in turn calls for expensive machining operations, and, moreover, the parts aresubject to clogging so as to become inoperative. However, in any event, a close tolerance is critical in such prior tappets. Asdistinguished from this, the present tappet provides a relatively large tolerance or clearance between the surfaces of larger circumference, i. e., member 32 and body 28, employing an absolute seal in the form of O-ring 33 to prevent longitudinal Passage of liquid at this area. Coacting liquid escape surfaces of comparatively small circumference are present at tube 43 and the bore through partition 42, so that a comparatively ample radial tolerance is possible at this point without resulting in an excessive escape of liquid. Return flow of the liquid to the reservoir between the tube and partition bore is effective Yet the need for expensive machining operations is eliminated by reason of the generous tolerance referred to.

Clogging-jamming, or freezing of .the parts, by lodgment of dirt or other impurities between the escape surfaces, is eliminated in the above described arran ement, by the proportioning of -the,clearances referred to,., whether between the adjacent relatively large diameter surfaces of .member 32 and body 28, or between the much smaller tube 43 and bore surface of partition 42.

ing the tappet of the likelihood of becoming inoperative in use and of greatly reducing the cost of production thereof.

Downward movement of the thrust member 32 causes the hole in partition 42 to rub past the tube 43, since said tube is constantly urged against the bottom of the body bore by spring 44. Even though small, this relative movement and rubbing action maintains the clearance between the partition 42 and tube 43 in clean, open condition, free for oil return to reservoir 35. If this rubbing and cleaning action did not exist, the sliding parts would soon clog and carbonize, preventing escape or return of the liquid. When such escape does not'occur. the device becomes unsatisfactory in operation, causing the valve to remain partially open. It will be appreciated that downward movement of thrust member 32 relative to the tube 43 must occur if spring I9 is to exert its valve closing function.

The axial spacing between the lower end of thrust member 32 and'the bottom of the bore in body 28 is such that these parts will engage and continue the operation of the valve should insufi'icient liquid be present in high pressure chamber 46 to operate the tappet in the intended fashion. This mechanical engagement of the parts, even though it may be accompanied by some noise, will insure operation of the engine tappets toenable the engine driven vehicle to be brought to a place of repair. Such mechanical engagementof the member 32 and the body 28 may take place at some other location than the bottom of the bore of the latter, obviously, for example, at the upper end of said body. flowever, I consider all such modifications as this, as well as any other slightly modified or redesigned construction and/or arrangement of the co-acting parts ofthe tappet, such as would be apparent to oneskilled in the art, to be within the scope of the present invention.

,. .It will be noted that the positioning of the ball check valve 45 relative to the lower end liquid inlet to tube 43 is such that a predetermined and readilyregulable time interval of short duration intervenes between the instant when the liquid in pressure chamber. 46 is initially compressed and the instant that said check valve engages and seats against the tube entry to seal the same. Said interval represents the time required for the liquid flowing upwardly toward the tube passage, to overcome the weight of the ball check valve and elevate the same the proper distance for seating. By affording a brief, though finite and readily determinable, period during which the body 28 shifts upwardly relative to member 32, and during whichthe latter is not correspondingly shifted, the tappet automatically compensatesfor the intentional clearance ordinarily left between the valve and actuating tappet therefor in an original mechanical installation. The lostmotion phase referred to distinguishes the present tappet construction from conventional types, in which immediate responsiveness in elevating the valve stem upon compression of the hydraulic column the tappet is characteristic. In consequence, the original valve timing may be retained without change. Moreover, the elimination of noise due to recurrent engagement of the tappetw-ith the valve stem, and characteristic of mosthydraulic tappet-s, is likewise a feature of the present construction.

The valve and tappet assembly herein shown and described is unfailing in operation under all conditions and at any position of the valve in the engine cycle. A constant, noiseless engagement of the valve and tappet is insured, as well as improved operation of the valve assembly as a whole. A continual flow 'of coolant takes place through the valve Ill, thus insuring uniform temperature thereof for most effective sealing against seat i5. Only the simplest operations of machining and assembly are required in manufacturing the entire structure; and standard production machine tools may be employed quite satisfactorily in producing the component parts thereof.

I claim:

1. A hydraulic tappet, comprising a hollow tubular body closed at one end. and adapted to be actuated endwise by an actuating device, a

member mounted to shift axially in said body with a relatively loose clearance therein, and adapted to forward the end thrust imparted to the body by said device to a further device, a pressure chamber between said member and closed l body end, means providing an absolute liquid seal between said member and body to prevent end escape of liquid in said chamber, between the member and body, asource of liqulchmeans providing a passage communicating said source 1 with said chamber to supply liquid thereto, and a valve preventing reverse flow of liquid through said passage from the chamber, said member having a surface movable therewith and slidably engaging said last named means With relatively close clearance to define therebetween a liquid escape passage of relatively restricted capacity for the escape of liquid trapped in said pressure chamber.

2. A hydraulic tappet, comprising a hollow of said member andbody to prevent end escape of liquid in said chamber between the member and body, a source of liquid, tubular means communicating said source with said chamber to supply liquid thereto, and a valve preventing reverse flow of liquid from said chamber through the last named means, said member concentrically en gaging and having a slidingfit' on said tubular means to define a self-cleaning annular liquid escape passage of relatively restricted capacity therebetween for the escape of liquid trapped in said pressure chamber.

3. A hydraulic tappet, comprising a hollow tubular body closed at one end and adapted to be actuated endwise by an actuating device, a member mounted to shift axially in said body with a relatively loose clearance therein, and adapted to forward the end thrust imparted to the body by said device toa furtherdevice, a pressure chamber between said member and closed body end, means providing an absolute 8 liquid 'seal between adjacent peripheral surfaces of said member and body to prevent end escape 'of liquid in said chamber between the member and body, a source of liquid, a pasSage definin'g element communicating said source with said chamber to supply liquid thereto, a valve engaging said element and preventing reverse flow of liquid from said chamber through the passage defined by said element, means slidably engaging and coacting with said element in defining a further self-cleaning liquid escape passage ofrelatively restricted capacity for the escape of liquid trapped in said pressure chamber, and means urging said body and member in opposite directions.

' 4. A hydraulic tappet comprising a hollow tubular body closed at one end and adapted to be actuated endwise, a member mounted to shift axially in said body with a relatively loose fit, a pressure chamber between said member and closed body end, means effecting an absolute liquid seal between adjacent peripheral surfaces of said member and body preventingescape' of liquid under compression in said chamber, a source of liquid, means providing a one-way liquid supply passage from said source to said chamber, said last named means being externally telescoped by said member to define therebetween a further liquid escape passage of relatively restricted capacity leading from said pressure chamber for the escape of liquid trapped in said pressure chamber. I I

5'. A hydraulic tappet comprising a hollow tubular body closed at one end and adapted to be actuated endwise,a member mounted to shift axially in said body with a relatively loose fit, a pressure chamber between said member and closed body end, means effecting an absolute liquid seal between adjacent peripheral surfaces of said member and body preventing escape therebetween of liquid under compression in said chamber, a source of liquid, means providing a one-way liquid supply passage from said source to said chamber, and a surface in fixed relation to said body having sliding engagement with said member and coacting therewith in defining a liquid escape passage of relatively restricted capacity leading from said pressure chamber for the escape of liquid trapped in said pressure chamber. 6. A hydraulic tappet comprising a hollow tubular body closed at one end and adapted to be actuated endwise, a member mounted to shift axially in said body with a relatively loose fit, a pressure chamber between said member and closed body end, means eifecting an absolute liquid seal between adjacent peripheral surfaces of said member and body preventing escape therebetween of liquid under compression in said chamber, a source of liquid, means providing a one-way liquid supply passage from said source to said chamber, said last named means being externally telescoped by said member to define therebetween a liquid escape passage of relatively restricted capacity leadingfrom said pressure chamber for the escape of liquid trapped in said pressure chamber, and means urging said body and member in opposite directions.

7. A hydraulic valve-actuating tappet, com"- prising a hollow tubular body closed at one end and adapted to be engaged at said-end by an actuating member, a thrust membertelescoped relative to said body and adapted to transmit thrust to a valve, sealing meansproviding' a liqui'cl tight annular seal between said member assua e and body, a source of liquid, a pressure chamber between said thrust member and the closed end of the body, whereby liquid under pressure in said last named chamber sustains thrust between said member and body, tubular means providing an interior duct communicating said source and chamber for the supply of liquid to said chamber, and valve means controlling the flow of liquid through the interior of said duct and preventing reverse flow from said chamber through said duct to said source, said member slidably engagin said tubular means and providing therebetween an escape passage of relatively small capacity leading from said pressure chamber to the source for the return thereto of liquid trapped in said pressure chamber by said sealing and valve means.

8. A hydraulic valve-actuating tappet, comprising a hollow tubular body closed at one end and adapted to be engaged at said end by an actuating member, a thrust member telescoped relative to said body and adapted to transmit thrust to a valve, sealing means providing a liquid-tight annular seal between said member and body, a source of liquid, a pressure chamber between said thurst member and the closed end of the body, whereby liquid under pressure in said last named chamber sustains thrust between said member and body, tubular means in fixed operating relation to said body providin an interior duct communicating said source and chamber for the supply of liquid to said chamber, valve means controlling the flow of liquid through the interior of said duct and preventing reverse fiow from said chamber through said duct to said source, said member slidably engaging said tubular means and providing therebetween'an escape passage of relatively small capacity leading from said pressure chamber to the source for the return thereto of liquid trapped in said pressure chamber by said sealing and valve means, and spring means normally urging said body and thrust member in opposite directions.

9. In a tappet of the type described, an externally guided, elongated, tubular body closed at one end, a cylindrical thrust member shiftable axially in said body, means for sealing said member and body against axial leakage therebetween, said member having an internal reservoir of substantial capacity, said body and member having a fluid supply opening therein for communicating said reservoir with a source of operating fluid, a hollow fluid supply tube in fixed operative relation to and within the closed end of said body, a pressure chamber adjacent said closed end to which said tube opens, said thrust member being slidably engaged on said tube, with the latter extending into said reservoir, whereby fluid under pressure may pass through the interior of the tube to the chamber, valve means at the chamber end of said tube coacting therewith to control flow of fluid from said reservoir through said tube to the chamber, fluid trapped under excess pressure in said chamber between the valve and sealing means escaping to the reservoir past the slidably engaging surfaces of the thrust member and tube and spring means normally urging said thrust member in a direction to cause fiuid to flow from the reservoir through said tube and past said valve means.

10. In a tappet of the type described, an externally guided, elongated, tubular body closed at one end, a cylindrical thrust member shiftable axially in said body, means for sealing said member and body against axial leakage therebetween, said member having an internal reser voir of substantial capacity, said body and member having fluid supply openings therein for communicating said reservoir with a source of operating fluid, a hollow fiuid supply tube in fixed operative relation to and within the closed end of said body, a pressure chamber adjacent said closed end to which said tube opens, said member being slidably engaged on said tube, with the latter extending into said reservoir, whereby fluid under pressure may pass through the interior of the tube to the chamber, valve means at the chamber end of said tube coacting therewith to control flow of fluid from said reservoir through said tube to the chamber, fluid trapped under excess pressure in said chamber between the valve and sealing means escaping to the reservoir past the slidably engaging'surfaces of the thrust member and tube and spring means normally urging said thrust member in a direction to cause fluid to flow from the reservoir through said tube and past said valve means, said thrust member being ported at its end opposite said pressure chamber.

11. A hydraulic tappet comprising a hollow tubular body, a member mounted in said body for relative axial movement therein, said body and member defining a pressure chamber between adjacent ends thereof, a soruce of liquid adapted to be communicated with said chamber, a one-way valve in the path of communication of said chamber and source, said valve being adapted to prevent substantial escape flow of liquid from the chamber and to permit flow in the opposite direction, means to peripherally seal said member and body against escape of liquid from said chamber between the member and body, and means telescoped into and slidably en'- gaging said member with a relatively close tolerance fit to denne a liquid escape passage of restrlcted capacity between said member and last named means Ior the controlled escape of liquid under pressure from said chamber.

12. A hydraulic tappet comprising a hollow tubular body, a member mounted in said body for relative axial movement therein, said body and member defining a pressure chamber between adjacent ends thereof, a source of liquid adapted to be communicated with said chamber, a one- Way valve in the path or communication of said chamber and source, said valve being adapted to prevent substantial escape flow of liquid from the chamber and to permit now in the opposite direction, means to peripherally seal said member and body against escape or liquid Irom said chamber between the member and body, and means in nxed relation to said body and Slidaoly engaging said member with a relatively close tolerance ht internally or said peripheral sealing means to oenne a liquid escape passage of restricted capacity between said member and last named means ior the controlled escape or liquid under pi essure from said chamber.

13. A hydraulic tappet comprising a hollow tubular body, a member mounted in said body for relative axial movement therein, said body and member oelining a pressure chamber between adjacent ends thereof, a source of liquid, a port for communicating said source with said chamber, an upwardly acting valve shiftable by the flow of liquid compressed in said chamber through said port to seat said valve against said port and seal the latter, said valve being predeteiminedly positioned with relerence to said port to afford a time delay interval of predetermined duration prior to; sealing of said port, clur; mg which said. body is shiftable' axially relative to said member, means to peripherally seal said member and body against escape of liquid: irqmsaid chamber between the member and body and means telescoped into" and slidably engaging said member with a relatively close 'tolerance' fit to definea liquid escape passage of restricted ca pacity between said member and last named means for the controlled'es'cape or liquid under pressure from said chamber.

1a. A hydraulidtappet comprising a tubular and'axially shiftableactu ated member, an actuating membe mounted in said actuated member to shift axially relative thereto and having an in-,

e m er u ei d i s axia t s d members definmg a pressure chamber between adjacent ends thereog mean s engaging "and ef reeun 'a' liquid-tight peripheral seal between said merr ibersf; a souree of liquid, and means pro v'iding one-way communication from said source to said pressure chamber; said last named means having interhal axial sliding, relatively close tolerance engagement with said aperture in said actuating member to define therebetween a selfcleahin 'liquid escape passage of restricted ca: pacity'communieating with said chamber for the escape of liquid trapped therein.

155A dr i fi tl pr in a cyl nder a plunger reciprocable. t ylinder on one side of a compression chamber therein, meansproriding a i oi qu d a oneay a a o mumeaung' im said source and chamber tor e?!" rfia le nthe Pder o n side:

of i m s n. Winte here n e n o-i vidi'ng a spurceo f liquid acneway passage com-. mu'riica'ting said source -and chamber for new of liquid only in the direction from said source to said chamber, said 'plung erhaving an axially extendingope'ning therein,- and an axially extend ing' metering. pin "in fi'zie'd relation to saideyling der and'dispos'd in said openingfm axial move;

ment of thepluiiger relative to the pin, said pin and opening co'actingto'defii'ie an annular liquid escape passage from s'aid'chamber which is of la ve mal d te nd iiedar a q az tive' axial'r'rjovementbfth plunger and pin in the operation drum tappet serving to prevent ciogg'mgbr 'saidescape passage.

17. A hydraulic rapper comprising a cylinder, a plungerreciprocable in the cylinder on one side 'of-"afcompression chamber therein, means providing" a sourceoi liquid 'a one-way passage communicatin gi said source and v chamber for flow of liquid 'only in the direction from said source to said chamber, said plungerhaving an axially extending'bore of small periphery therein, and an axially extending metering pin of small periphery in fixed relation to said cylinder and telescopedfin said borejwith a relatively tree:

ciearane j said pin and bare eoactin to define an annular liquid escape passage from said chamber which ispj limited area, said plunger being externally sealed with relation to said cylinder to prevent fiowo f liquid between adjacent surfaces of the plunger and cylinder, relative axial xriovement of the -plunger and pin in the operation of the tappet serving to prevent clogs n 3 aid es a e passage- 18. A hydraulic tappet comprising a hollow tubular body, a plunger. guided for axial sliding movement by said body on one side of 'a pressure chamber therein, a source of liquid, a passage communicating said chamber with said source during the operation of the tappet, and an axially extending pin supported in fixed relation, to said body, said plunger having an axial open: ing which slidably receives said pin in the opera-,. tion of'the tappet and which coacts with the pin in defining a further; annular liquid escape passage from. said chamber which is of relatively small diameter and limited area, relative, sliding movement of the plunger and pm during the operation ofthe tappet serving to insure against cloggin of; said escape passage.

- OSCAR H; BANKER.

. arr wrcr an The followingv references. are of record in the file of this patent:

UNITED STATES PATENTS Num' er Nam Date Re,2l,93l Voorhies et a1. Oct. 21, 1941 1,793,935 Hallett Mar. 31, 1931 1 ,953,6l1 Jardine Apr. 3', 1934 2,( )"73 ,7 09 Eaton-n; Mar. 16, 1937 2,195,514 Summers Feb.;15, 193a. 2,237, 85,9 Voorhies Apr. 8; 19.4]; 2,345,525, Voorhies -Apr. 11', 1944 ang na 4 Barri Feb. 5, 1946 2,40f1,24;1 MacMillan July 16', 1946 2,442,556 Hufferd l 'June 1, 194a

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