US2942595A

US2942595A - Hydraulic tappet

Info

Publication number: US2942595A
Application number: US727333A
Authority: US
Inventors: Sr Paul F Bergmann; Morris V Dadd
Original assignee: Johnson Products Inc
Current assignee: Johnson Products Inc
Priority date: 1958-04-09
Filing date: 1958-04-09
Publication date: 1960-06-28
Anticipated expiration: 1977-06-28

Description

June 28, 1966 Filed April 9, 1958 P. F. BERGMANN, sR., ETAL HYDRAULIC TAPPET 3 Sheets-Sheet 1 E'QE- INVENTOR ATTORN EY June 28, 1960 P. F. BERGMANN, sR., ETA!- HYDRAULIC TAPPET Filed April 1958 3 Sheets-Sheet 3 NvENToR M3,),

ATTORNEY United States Patent HYDRAULIC TAPPET Paul F. B er'gmaun, Sn, North Muskegon and Morris V.

Dadd, Ada, MiclL, assignors to Johnslm Products In- ;aorporated, Muskegon, Mich., a corporation of Michi- Filed Apr. 9, 1958, Se!- No. 727,333 15 Claims. (Cl. 123-40 This invention relates to hydraulic tappets in general, and more particularly to hydraulic tappets for use in englues operating at high speeds.

The engine valves of internal combustion engines are required to be timed to the combustion occurring in the engme cylinders. Generally the engine valves are operated by timing cams acting through some form of valve actuating mechanism. Hydraulic tappets are normally included within the valve actuating mechanism to compensate for any change in the effective length of the parts due to expansion or contraction, as a result of changing engine temperatures, or as a result of wear between the parts.

Hydraulic tappets usually include a blind end hollow tappet body member having a plunger member slidably Patented June 28, 1960 ice 7 2 engaged between the push rod seat member and the upper end of the plunger member.

The reservoir chamber in most hydraulic 'tappets is filled with hydraulic fluid at engine operating pressures. Passageways for such purposes are generally provided through the side wall of the tappet body member and through the push rod seat member. These passageways provide substantially continuous communication between disposed therein. Separate fluid chambers are provided within the tappet body member on opposite sides of the plunger member. By an exchange of fluid between the two chambers the plunger may be relatively adjusted within the tappet body member and, accordingly, the

overall effective length of the valve actuating mechanism may be changed. When the parts of the valve actuating mechanism are expanded due to an increased temperature condition the plunger member is automatically-adjusted to a lower relative position within the tappet body member. This is done by allowing some of the fluid to escape from the pressure chamber space between the end of the plunger and the blind end of the tappet body member. When the parts of the valve actuating mechanism are contracted due to a reduced temperature condition, or when there is wear between the parts which reduces their overall efl'ective length, the plunger member is adjusted to a higher relative position, away from the blind end of the tappet body member. This is accomplished by admitting more fluid to the pressure chamber space.

The means employed in hydraulic tappets for venting or bleeding hydraulic fluid from the pressure chamber space between the lower end of the plunger member and the blind end of the tappet body member, may vary in different hydraulic tappets.

Some hydraulic tappets have a closely controlled clearance space between the side walls of the plunger member and the inner walls of the tappet body member. The clearance space is designed to provide a controlled leakage of fluid from the pressure chamber space below the plunger and about the outer periphery of the plunger.

This means of providingfor the escape of hydraulic fluid from the pressure chamber space is referred to as leakdown. i

Other hydraulic tappets may be provided which include some other means for providing for the escape of hythe reservoir chamber and the source of hydraulic fluid within the engine. The free communication of hydraulic fluid to the reservoir chamber is necessary in most tappets to enable an adjustment of the plunger member when required.

At high engine speeds the free communication of hydraulic fluid to the reservoir chamber, in combination with other factors, may cause a condition known as tappet pump-up. This condition exists when the tappet prematurely responds to certain changes in the valve actuating mechanism and increases its eifective length. This is highly undesirable since it can keep the engine valve from closing as it should. What occurs is that the inherent resiliency in the valve train parts, and the fluctuations of the engine valve spring, set up a false requirement for tappet adjustment during high speed operations. This causes an exchange of fluid between the reservoir and pressure chambers and an increase in the elfective length of the tappet when it is really not required. g .i

It is an object of thlS'lIlVflIllIlOIl to provide a different means of communication between the reservoir chamber of a tappet and its fluid supply source. Such communication' is between the plunger and push rod seat members and requires no passageways to be bored through the push rod seat member. The. fluid flow access that is provided may readily be varied to control the flow of fluid to the reservoir chambers. The fluid accessto the reservoir v,chamber may also be closedduring the Joperation of the tappet and maybe opened as necessary for normal tappet adjustment. Thus, onefactor of tappet pump-up may be controlled.

' It is also an object of this invention to teach the use of a resilient member disposed between the plunger and push rod seat members to take up the surge in the valve actuating mechanism which will otherwise cause tappet pump-up. A compressible wave spring is found highly adapted for such purpose. The wave spring is required to be sufliciently strong to overcome the plunger return spring as necessary to prevent premature plunger adjustment. A wave spring is particularly adaptable because of better load control for a given linear travel.

It is therefore also an object of this invention to teach the use of an anti-surge device within the tappet mechanism to prevent separation the valve train parts due to engine valve spring surge or otherwise. Such an anti-surge device, as with the wave spring suggested, must be stronger in its operating range than the plunger return spring and should have less mass to move.

A further object of this invention is to provide a comchange of fluid between the reservoir and pressure chambers and cause tappet pump-up. Furthermore, the means' provided biases the plunger against premature adjustment and thereby serves to prevent an exchange of fluid. and

consequent tappet pump-up.

A still further object of this" invention is to provide a reservoir fluid control and anti-surge device in combination with means for controlling the escape of hydraulic fluid I from the pressure chamber spaces of a tappet as necessary for normal tappet adjustment.

The aforementioned and other advantages of this invention will be more apparent in the description and illustration of tappets embodying the principles of this invention as hereinafter set forth.

In the drawings:

Fig. l is a cross sectional view of a conventionally known tappet including the improvement taught by this invention.

Fig. 2 is a cross sectional view of the tappet shown by Fig. l, and showing the tappet parts in different relative positions.

Fig. 3 is an enlarged perspective of the wave spring member which is particularly adapted to carrying out the teachings of this invention.

Fig. 4 is a cross sectional view of a hydraulic tappet having a porous plug for controlling the escape of hydraulic fluid from the pressure chamber and including the improvement taught by this invention.

, Fig. 5 is a side elevational view of the plunger member of the hydraulic tappet shown by Fig. 4. Fig. 6 is an enlarged view of the sealing member used in the hydraulic tappet of Fig. 4.

Fig. 7 is a cross sectional view of a hydraulic tappet having a relief valve for controlling the escape of hydraulic fluid from the pressure chamber and which also includes the improvement taught by this invention.

Fig. 8 is a cross sectional view of the hydraulic tappet of Fig. 7 showing the tappet parts in a different relative position.

Fig. 9 is a cross sectional view of a part of the hydraulic tappet shown by Fig. 7 with the parts of the tappet shown in another different adjusted relation. In the discussion of this invention which follows, several different types of hydraulic tappets are disclosed. Those parts of these different hydraulic tappets which are the same will bedesignated by the same numerals.

In general, each of the hydraulic tappets include a blind end tappet body member which is reciprocal within a bore provided in an engine block. The closed end of the tappet body member is engaged by a timing cam which is not shown. An engine valve actuating push rod is shown engaged with the upper end of the tappet body member. Other parts of the engine valve actuating mechanism, the engine valve, and the engine valve spring have 'not been shown because they are considered-sufficiently well-known that their operation will be understood without illustration.

A plunger member is slidably disposed within the tappet body member. The plunger member divides the tappet body into a pressure chamber and a reservoir chamber. The pressure chamber is provided between the lower end of the plunger member and the blind end of the tappet body member. The reservoir chamber is provided within the plunger member. The reservoir chamber is closed by a push rod seat member received within the tappet body member over the plunger member.

In each of the tappets described the timing cam is adapted to reciprocate the tappet body member and in so doing to cause the push rod member to actuate an engine valve. Upon an increase in the effective length of the engine valve actuating mechanism, as due to increased engine temperatures causing expansion ofthe parts thereof, the plunger member is required to seek a lower relative position within the tappet body member. This is perlmitted by allowing fluid to escape from the pressure chamber space. In those instances in which the valve actuating mechanism has contracted due to a change in engine temperatures or wear between the parts, the plunger 'fmember is required to be adjusted to a higher relative "position within the tappet body member. This is accomplished by admitting more fluid to the pressure chamber space below the plunger.

Referring to the hydraulic tappets which are illustrated,

in further detail, each includes a hollow tappet body member 2 which is closed at one end. The tappet body member is reciprocal withina bore provided within an engine block 3. A passageway 4 is provided through the engine block to supply hydraulic fluid to the tappet. A wide annular groove or recess 5 is provided circumferentially around the tappet body member. The recess 5 provides communication with the passageway 4 throughout most of the reciprocal travel of the hydraulic tappet. A passageway 6 is provided through the tappet body member from within the circumferential groove or recess 5.

A plunger member 10 is slidably disposed within the tappet body member 2. A reservoir chamber space 11 is provided within the plunger member 10. A passageway 12 is provided through the lower end of the plunger member. The passage 12 provides communication between the reservoir chamber 11 and the pressure chamber space 13 provided between the end of the plunger member 10 and the blind end of the tappet body member 2. The passageway 12 is closed by a check valve which includes .a valve plate 14 biased to a closed position by a coiled compression spring 15. The check valve spring 15 is seated on a retainer cap 16 which is engaged with the end of the plunger member 19.

Accesses

17 and 18 are provided through the lower end of the retainer member 16 and through the side walls thereof. The retainer member 16 is held engaged about a shoulder 19 to plunger member 10 and provides a seat for the plunger return spring 20 which is engaged between the end of the plunger member and the blind end of the tappet body member 2.

A push rod seat member 30 is slidably disposed within the tappet body member above the plunger member 10.

The push rod seat member 30 includes a boss 31 which is received within the open upper end 32 of the plunger member 10. The push rod seat member 30 also includes an annular, shoulder 33 which is disposed for engagement with the upper end 32 of the plunger member. The upper end 34 of the push rod seat member 30 is formed to provide a liquid seal with the internal walls of the tappet body member 2. The push rod seat member 30 is undercut circumferentially at 35 to provide an annular reservoir supply passage 36. The reservoir supply passage 36 is in communication with the passageway 6 formed through the tappet body member 2. The upper face of the push rod seat member 30 is formed to provide a spherical seat 37 within which is received the push rod member 38.

Between the plunger member 10 and the push rod seat member 30 is provided the control means 50 of this invention. A stepped shoulder 51 is provided within the end face of the push rod seat member 30, next adjacent the plunger end 32. A wave spring 52, such as is shown by Fig. 3, is disposed within the space provided between the shoulder 51 and plunger end 32. The undulate spring 52 is under compression. The unrestrained wave spring 52 would provide about .010 of an inch clearance between the push rod seat end surface 33 and the plunger end 32.

However, a .002 of an inch clearance is provided when the spring forces within the tappet are in balance and neutral. The undulating form of the compressible spring member 52 provides parts 53 engaging the push rod seat member 30, and parts 54 engaging the plunger member 10. The inclined form of the spring between these parts provides accesses 55 which, in combination with the separation the spring effects between the plunger and push rod seat members, forms the fluid flow access 56 between the reservoir supply passageway 36 and the reservoir chamber 11.

The different parts of the tappet which have been described are retained within the tappet body member 2 by space 21 between the exterior walls of the plunger member and interior walls of the tappet body member 2.

The operation of the hydraulic tappet 100, as regards the leakdown control, is as follows: During the rise of the tappet body member 2, under the influence of the timing cam, the lift force of the cam is transmitted to the push rod member 10 through the hydraulic fluid trapped in the pressure chamber space 13, and due to its incompressible nature. The rmistance of the engine valve to be opened imposes an increasing resistance force upon the push rod seat member 30. This in turn causes an increased pressure condition to exist within the pressure chamber space 13. Accordingly hydraulic fluid is caused to leak from the pressure chamber space 13, through the clearance space 21, into the reservoir supply passage 36.

Following each stroke of the tappet 100, the check valve plate 14 may open to replenish the loss of hydraulic fluid in the pressure chamber space 13. At the same time the plunger return spring serves to bias the plunger member 10 upwardly and into engagement with the push rod seat member 30. If the engine valve actuating parts have changed their etfective length during the actuation of the tappet the push rod seat member 30 will be required to assume a lower relative position within the tappet body member 2. Accordingly the plunger member 10 will be returned by the plunger return spring 20 to a lower relative position within the tappet body member than if no adjustment were required. If the valve actuating parts have contracted due to a lowered temperature condition or wear between the parts, the push rod seat member 30 will assume a higher relative position within the tappet body member 2. Accordingly the plunger return spring 20 will adjust the plunger 10 to a higher relative position within the tappet body member 2 and the check valve plate 14 will open to admit the necessary fluid to the pressure chamber space 13.

In thehydraulic tappet 100 the pressure chamber 13 loses some hydraulic fluid during each engine valve actuating movement of the tappet. This requires that the plunger member 10 be constantly readjusted withinthe tappet body member 2. It also requires that the check valve member 14 open during substantially each cycle to replenish the necessary hydraulic fluid in the pressure chamber space 13.

If the wave spring 52 were not provided, and the fluid flow access 56 were such as enabled substantially continuous fluid flow to the reservoir 11, the condition known as tappet pump-up would occur in tappet 100 at high engine speeds. When the surge of the engine valve spring, or the inherent resiliency in the valve train parts, caused a momentary separation in the valve train linkage, the plunger return spring 20 would respond as for a normal call for plunger adjustment and raise the plunger 10 to take up the slack. In doing so the volume of the pressure chamber space 13 would be increased,

; the pressure would drop below the engine operating pressure condition in the reservoir chamber 11, and the check -valve plate 14 would open to replenish the lost fluid. This exchange of fluid is due to the false response of :the plunger 10, the pressure condition in the reservoir chamber 11, and the flow of fluid allowed due to the open communication of the reservoir with the fluid supply :source. After the fluid exchange has occurred the plunger 10 cannot regain its previous position and only a fast leakdown through the clearance space 21 can correct the false response. When the leakdown cannot occur as fast as required under such conditions, as at [high engine speeds, the engine valve will be held open while the tappet is on the base circle of the actuating cam. I v

Ihe operation of tappet 100, as adapted to include the control means 50, is as follows: On the initial effort of the timing cam to raise the tappet body 2, the plunger member 10'is moved into engagement with the push rod seat member 30. The wave spring 52 is compressed and the push rod seat shoulder 33 engages the plunger end 32 to close the fluid access 56 to the reservoir chamber 11. During the rise and fall of the tappet 100, on the timing cam, the reservoir access 56 remains closed. The escape of fluid from the pressure chamber space 13 is through the clearance space 21', as has been described. However, whenever the force of the engine valve spring is momentarily withdrawn from the push rod seat member 30, the resilient character of the compressed wave spring 52 comes into play. At such times the wave spring 52 will momentarily react to take up the slack in the valve train and will hold the plunger 10 against any premature adjustment. Consequently there is no change in the volume of the pressure chamber space 13, no requirement for fluid from the reservoir 11, and nortappet pump-up.

The presence .of the fluid flow control means 50, and its alternate action in opening and closing the fluid flow access 56, also serves to restrict the flow of fluid into the reservoir chamber 13 and consequently a lower pressure condition, than the engine pressure condition, will exist in the reservoir chamber. This necessitates that the pressure in chamber 13 drop lower than would normally be required before the check valve plate 14 will open. This reduced pressure condition exists at higher engine speeds in particular, and when most desirable. The effect decreases as engine speeds are reduced.

The disclosed control means 50 does not disturb the normal operation of the tappet 100 in changing its effective length. The plunger 10 is still required to be moved the push rod seat, and

as in tappet 100. The only quite diiferently than tappets and V r V The tappet 300 includes a pressure chamber relief 'valve 60 which is disposed between the push roam:

upward after each stroke of the tappet to compensate for fluid lost from the pressure chamber 13 by leakdown. Any change in the effective length of the valve train parts merely changes the distance the plunger is required to'be returned. The fluid control and antisurge spring 52 is slightly stronger than-the plunger return spring 20 so that a slight separation is always provided between plunger members upon 'a return of the tappet to the basecircle of the actuatingcam.

The tappet 200 shown by Fig. 4, and having the parts shown by Figs. 5 and 6, operates difierently than the tappet 100 shown by Figs. 1 and 2.

This tappet 200 has a larger clearance space 22. be-

tween the plunger :10 and tappet body member 2. A:

passageway 23 is formed through the plunger 10 and'is in communication with the-reservoir 11. One end of the passageway 23 is enlarged and a porous plug 24 is disposed therein. A sealing ring 25 is disposed about the plunger 10, above the porous plug 24, and within a peripheral recess or groove 26 provided about the plunger. The sealing ring is known as a quadring and has annular flanges 27 at each corner, separatedby fluid receptive pockets 28. When the fluid pocket next adjacent the annular space 22 is filled flanges on each side thereof are forced vide a good seal against fluid flow.

The tappet 200 operates similar to tappet 100 except that the escape of fluid from the pressure chamber 13 is controlled by the porous plug 24. 'The use of the porous plug 24 in combination with the sealing ring 25 eliminates the necessity of close tolerance machining, sorting, and selective fitting of plunger and tappet body members since the clearance space 22 neednot be con trolled so accurately as in tappet 100.

The operation of the fluid flow control and anti-surge means 50, of this invention, is the same in tappet200 diflerence is in having the pressure chamber fluid bled, into the reservoir 11 rather than into the reservoir supply passage36. p

The tappet 300, shown by Figs. 7, 8 and 9, operates outwardly to pro- With fluid under pressure the member 30 and plunger 10. The relief valve 60 includes a flat annular sealing ring 61 sandwiched between thin

metallic discs

62 and 63. 'The sealing ring '61 has its outer periphery disposed in fluid sealing engagement with the inner peripheral walls of the tappet body member 2. The

discs

62 and 63 serve to prevent the sealing ring 61 from being distorted under the high fluid pressure conditions to which it is subjected, and provide a better valve seat facing, as will be seen. The relief valve 60 may be made in another manner, but thisis one of its preferred forms.

The relief valve 60'closes the annular clearance'space 22 between the plunger and tappet body members. This clearance space has been given the same numeral designation as the clearance space in tappet 200 because they are about the same, as contrasted to the clearance space 21 in tappet 100. One advantage of providing the relief valve 60 is that the close tolerance machining, sorting and selective fitting of plunger and tappet body parts, to provide proper leakdown control, is avoided. The clearance space 22 is not, however, such as is conducive to free fluid flow. There is a restriction to fluid such as provides a pressure gradient between the ends of the clearance space 22 near the pressure chamber 13 and the relief valve 60.

The lower disc 63, of the relief valve 60, seats on the plunger end 32. The upper disc 62 of the relief valve is engaged by the shoulder 33 of the push rod seat member 30. The reservoir fluid flow control means 50, is disposed within the stepped shoulder recess 51 of the push rod seat member 30. As in

tappets

100 and 200, a Wave spring 52 is used. The Wave spring 52 is engaged, under slight compression, with the relief valve 60.

The operation of tappet 300 is as follows: When the tappet is first raised by the actuating cam, the plunger 10 moves the relief valve member 60 into engagement with the shoulder 33 of the push rod seat member 30. The fluid flow access 56 to the reservoir chamber 11 is closed, the relief valve 60 is held in a closed position over the end of the clearance space 22, and the wave spring 52 has been compressed as necessary to accomplish this. The tappet parts are substantially as shown in Fig. 7.

During the rise and fall of the tappet '300 on its actuating cam, the fluid control and anti-surgespring 52 acts as necessary to prevent engine valve spring surge, or other means causing momentary separation between any of the valve train parts, from causing premature adjustment of the plunger member 10. The control means '50 operates substantially as in

tappets

100 and 200. In addition the force of the compressed resilient spring member 52 also serves to keep the relief valve 60 seated on the end 32 of the plunger 10. The parts are shown under these conditions in'Fig. 8.

In the course of operation of the tappet 300, large unit pressure conditions are built up in the pressure chamber space 13 and the annular pressure chamber space 22. The pressure condition in space 22 seeks to attain the level of pressure in pressure chamber 13 but always lags due to the flow restriction and rapidity of tappet operation. As a result, a higher fluid pressure condition exists near the pressure relief valve 60, than in the pressure chamber space 13, when the tappet returns to the base circle of the actuating cam. This higher pressure condition is suflicient to keep the wave spring 52 compressed, when the tappet returns to the base circle of the actuating cam, and to cause a separation between the valve 60 and the end 33 of the plunger 10. The parts are shown at the time of the opening of the relief valve by Fig. 9.

Upon a bleeding off of fluid from the pressure chamber space 22 the wave spring 52 takes over and closes the relief valve 60. Atthe same time the fluid flow access 56 to the reservoir chamber 11 is opened.

. Except. for the additional purpose served by the wave .spring52, ,as regards the relief valve 60, it operatessubstantially as in tappets and 200 to prevent tappet pump-up.

This invention has been described, as employed in one acceptable form, with three different types of tappets. The solution for tappet pump-up operates substantially the same in each of the

tappets

100, 200 and 300. However, as shown in tappet 300, the means employed to counteract the pump-up problem is capable of performing other operating functions.

It should be remembered that the actual size of a hydraulic tappet is usually smaller than is shown by the illustrations and that certain parts, clearance spaces, etc., have had to be exaggerated for illustration purposes. The high speeds of tappet operation and their small size require only minute changes in length and the exchange of extremely small amounts of fluid for each cycle of tappet operation.

While a preferred embodiment of this invention has been described it will be understood that other modifications and improvements may be made thereto. Such of these modifications and improvements as incorporate the principles of this invention are to be considered as included in the hereinafter appended claims unless these claims by their language expressly state otherwise.

We claim:

1. In a hydraulic tappet comprising a hollow tappet body member closed at one end, a plunger member and a push rod seat member slidably disposed within said hollow tappet body member and disposed for engagement with each other, and a hydraulic fluid reservoir chamber provided between said plunger and push rod seat members: control means for opening and closing said reservoir chamber to a fluid supply source under normal operative conditions of said hydraulic tappet; said control means including, a resilient member disposed between said plunger and push rod seat members and having fluid flow passageways provided therethrough, 'said resilient member normally holding said plunger and push rod seat members separated to provide a fluid flow access therebetween and yielding to the forces of compression in the actuation of said tappet to permitthe engagement of said plunger and push rod seat members and the closing of said fluid flow access.

2. In a hydraulic tappet comprising a hollow tappet body member closed at one end, a plunger member and a push rod seat member slidably disposed within said hollow tappet body member and disposed for engagement with each other, and a hydraulic fluid reservoir chamber provided between said plunger and push rod seat members: control means for opening and closing said reservoir chamber to a fluid supply source under normal operative conditions of said hydraulic tappet; said control means including, a spring member disposed between the adjacent ends of said plunger and push rod seat members and in compression for holding said members separated and providing a fluid flow access therebetween, said spring member being further compressible for enabling said plunger and push rod seat members to be engaged for closing said fluid flow access during the actuation of said tappet.

3. In a hydraulic tappet comprising a hollow tappet body member closed at one end, a plunger member and a push rod seat member slidably disposed within said hollow tappet body member and disposed for engagement with each other, and a hydraulic fluid reservoir chamber provided between said plunger and push rod seat members: control means for opening and closing said reservoir chamber to a fluid supply source under normal operative conditions of said hydraulic tappet; said control means including, an undulate spring disposed between the ends of said plunger and push rod seat members for biasing said members apart and providing a fluid flow access therebetween, said spring being axially compressed and permitting said plunger and push rodseat members to; be engaged and to. close said fluid flowaccess during the actuation of said tappet.

4. In a hydraulic tappet comprising a hollow tappet body member closed at one end, a plunger member and a push rod seat member slidably disposed'within said hollow tappet body member and disposed for engagement with each other, and a hydraulic fluid reservoir chamber provided between said plunger and push rod seat members: control means for opening and closing said reservoir chamber to a fluid supply source under normal operative conditions of said hydraulic tappet; said control meansincluding, a stepped shoulder recess provided in the end face of one of said plunger and push rod seat members, a wave spring received in said stepped shoulder recess and engaged with the other of said plunger and push rod seat members, said wave spring being operative to hold said plunger and push rod seat members separated to provide a fluid flow access therebetween, and said wave sp'ringyielding axially to the forces of compression imposed thereon during the actuation of said tappet and allowing said plunger and push rod seat members to be engaged for closing said fluid flow access.

5. In a hydraulic tappet comprising a hollow tappet body member closed at one end, a plunger member and a push rod seat member slidably disposed within said hollow tappet body member and disposed 'for engagement with each other, a hydraulic fluid reservoir chamber provided between said plunger and push rod seat members, and means provided between said plunger and i the closed end of said tappet body member for biasing said plunger member into engagement 'with said push rod seat member: control means provided between said plunger and push rod seat members for preventing the premature adjustment of said plunger member; said control means including a resilient member of greater strength than said biasing means for holding said plunger and push rod seattmembers separated and providing a fluid flow access to said reservoir chamber therebetw'een, when said tappet is inactive, and for separating said plunger and push rod seat members, during the actuation of said tappet, only as necessary to counteract the tendency of said biasing means to adjust the relative position of said plunger Within said tappet body member in response to the fluctuation of external forces on .said tappet, said resilient member otherwise yielding to the external forces imposed on said tappet and permitting said plunger and push rod seat members to be engaged for closing said fluid flow access to said reservoir. V

6. In a hydraulic tappet comprising a hollow ,tappet body member closed at one end, a plunger member and a push rod seat member slidably disposed within said hollow tappet body member and disposed ,for engagement with each other, a hydraulic fluid reservoir chamber provided between said plunger and push rod seat members, and means provided between said plunger and the closed end of said tappet body member for biasing said plunger member into engagement with said push rod seat member: control means provided between said plunger and push rod seat members for preventing the premature adjustment of said plunger member; said control means including a compression spring member of greater strength than said biasing means for holding said plunger and push rod seat members separated and providing a fluid flow access to saidreservoir chamber therebetween, when said tappet is inactive, and for separating said plunger and push rod seat members, during the actuation of said tappet, only'as necessary to counteract the tendency of said biasing means to adjust the relative position of said plunger within said tappet body member in response to the fluctuation of external forces on said tappet, said compression spring member otherwise yielding to the external forces imposed on said tappet and permitting said plunger and push rod seat members to be engaged for closing said fluid flow access to said reservoir. 7 t

,7. In a hydraulic tappet comprising a hollow tappet 10 body membercloseld at one end, a plungermember and a push rod seat member slidably disposed withinp said hollow tappet body member and disposed for engagement with each other,- a hydraulic fluid reservoir chamber provided between said plunger and push rod seat members, and means provided between said plunger and the closed end of said tappet body member for biasing said plunger member into engagement with said push rod seat member: control means provided between said plunger and push rod seatmembers for preventing thepremature adjustment of said plunger member; said con trol means including an undulate spring member of greater strength than said biasing means for holding said plunger and push rod seat members separated and pro-- viding afluid flow access to said reservoir chamber therebetween, when said tappet is inactive, and'for separating said plunger and push rod seat members, during the actuation of said tappet, only as necessary to counteract the tendency of said biasing means to adjust the relative position of said plunger within said tappet body member in response to the fluctuation of externalforces,

member, a-push rod seat received in said tappet body member and disposed over said-plunger member for engagement therewith, a reservoir chamber space. provided between said plunger and push rod seat members, and a resilient member received between said plunger and push rod members in compression for holding said plunger and push rod members separated and providing a fluid flow access to said reservoir chamber therebetween, said resilient member being further compressed and closing said fluid flow access during actuation of said tappet, said resilient member being stronger under compression than said plunger biasing spring for separating said push rod seat from said plunger member in response to external force fluctuations otherwise causingsaid biasing spring to member. I

9. A hydraulic tappet, comprising; a hollow tappet body member closed at one end and having a plunger member slidably disposed therein and forming a pressure chamber space with the closed end thereof, a compres: sion spring within said pressure chamber forbiasing said plunger away from the closed end of said tappet body member, a pushrod seat received in said tappet body member and disposed over said plunger member for engagement therewith, a reservoir chamber space provided between said plunger and push rod seat memprematurely adjust said plunger bers, and a resilient member received between said plunger and push rod members in compression for bolding said plunger and push rod members separated and providing a fluid flow access to said reservoir chamber therebetween, said resilient member comprising a wave spring and one of said plunger and push rod seat members being formed to provide a stepped shoulder recess within the 'end face thereof for receiving said wave spring, said wave spring being further compressed between said plunger and push rod seat members during the actuation of said tappet until said plunger and push rodseat members are engagedand close said fluid flow access, said wave spring being stronger under compression than said plunger biasing spring for separating said spring to prematurely'adjustsaid plunger member;

10. In a hydraulic tappet comprising a hollow tappet body member closed at one end and having a plunger member slidably disposed therein and forming a pressure chamber space with the closed end thereof, a push rod seat member received within said tappet body member and disposed for engagement with said plunger member, a reservoir chamber formed between said plunger and push rod seat members, and a pressure differential responsive check valve disposed between said reservoir and pressure chambers for controlling the flow of fluid from said reservoir to said pressure chamber and accordingly the relative adjustment of said plunger member within said tappet body member; means for controlling the fluid pressure condition attainable within said reservoir chamber and accordingly modifying the responsive character of said check valve, the flow of fluid from said reservoir to said pressure chamber, and the adjustment of said plunger member in accordance therewith, said means including a variable restricted fluid flow access provided between a source of hydraulic fluid under pressure and said reservoir chamber.

11. In a hydraulic tappet comprising a hollow tappet body member closed at one end and having a plunger member slidably disposed therein and forming a pressure chamber space with the closed end thereof, a push rod seat member received within said tappet body member and disposed for engagement with said plunger member, a reservoir chamber formed between said plunger and push rod seat members, and a check valve provided between said reservoir and pressure chambers and responsive to a lower pressure condition in said pressure chamber than exists in said reservoir for opening said valve and admitting fluid from said reservoir to said pressure chamber for the operative adjustment of said plunger member within said tappet body member; means for controlling the flow of fluid to said reservoir chamber and accordingly controlling the operative adjustment of said plunger member attainable during any one cycle of said tappet, said means including providing a fluid flow access to said reservoir chamber between said plunger and push rod seat members and having a member disposed between said pltmger and push rod seat members for spacing said members apart and restricting the flow of fluid through said access as desired.

12. In a hydraulic tappet comprising a hollow tappet body member closed at one end and having a plunger member slidably disposed therein and forming a pressure chamber space with the closed end thereof, a push rod seat member received within said tappet body member and disposed for engagement with said plunger member, a reservoir chamber formed between said plunger and push rod seat members, and a check valve provided between said reservoir and pressure chambers and responsive to a lower pressure condition in said pressure chamber than exists in said reservoir for opening said valve and admitting fluid from said reservoir to said pressure chamber for the operative adjustment of said plunger member Within said tappet body member; means for controlling the flow of fluid to said reservoir chamber and accordingly controlling the operative adjustment of said plunger member attainable during any one cycle of said tappet, said means including providing a fluid flow access to said reservoir chamber between said plunger and push rod seat members and having a resilient member under compression disposed between said plunger and push rod seat members, said resilient member being further compressed during the actuation of said tappet until said plunger and push rod seat members are engaged to close said fluid flow access and cutoff said reservoir chamber from the fluid pressure source otherwise in communica tion therewith.

13. A hydraulic tappet comprising; a hollow tappet bodymember closed at one end and having a plunger member, slidably disposed-therein, said plunger member.

forming a pressure chamber space with the closed end of said tappet body member, a reservoir chamber space formed within said plunger member, a push rod seat member slidably disposed within said tappet body member for engagement with said plunger member and closing said reservoir chamber space, said push rod seat member being circumferentially relieved to provide an annular reservoir supply passage next adjacent the inner peripheral wall of said tappet body member, said pressure chamber space being relieved of hydraulic fluid by the escape of fluid between said plunger and the inner peripheral wall of said tappet body member into said reservoir supply passage, and means disposed between said plunger and push rod seat members for separating said plunger and push rod seat members to provide a fluid flow access between said reservoir supply passage and said reservoir chamber space, when said tappet is inactive, and during high speed fluctuations of external forces thereon to prevent the premature adjustment of said plunger member within said tappet body member, said separation means being spaced from the inner peripheral wall of said tappet body member for the least interference with the escape of fluid from said pressure chamber space, and said separation means being overcome and permitting said plunger and push rod seat members to be engaged for closing said fluid flow access at all other times during the actuation of said tappet.

14. In a hydraulic tappet comprising a hollow tappet body member closed at one end and having a plunger member and a push rod seat member slidably received therein and separating the interior of said tappet body member into pressure and reservoir chamber spaces, and in which the relative disposition of said plunger member within said tappet body member is determinative of the effective length of the tappet and such disposition is dependent upon the amount of hydraulic fluid within said pressure chamber space: a relief valve disposed between the ends of said plunger and push rod seat members for controlling the escape of fluid from said pressure chamber space through the annular clearance space between said plunger and tappet body members, said valve comprising; an annular sealing ring sandwiched between metal discs, said sealing ring engaging the interperipheral wall of said tappet body member for closing said annular clearance space, said valve being responsive to fluid pressure conditions built-up within said clearance space next adjacent thereto for separation from said plunger member and for venting said pressure chamber space, via said clearance space, to said reservoir, and a resilient member disposed between said push rod seat member and said relief valve in compression for biasing said relief valve in engagement with said plunger member and for holding said push rod seat member separated from said valve to provide a fluid flow access to said reservoir therebetween, said resilient member being such as is further compressed during the actuation of said tappet and permits the engagement of said push rod seat member with said relief valve for the closing of said fluid flow access to prevent tappet pump-up, and said resilient member also being such as remains in such further compressed state during the lifting of said relief valve from said plunger member.

15. In a hydraulic tappet comprising a hollow tappet body member closed at one end and having a plunger member and a push rod seat member slidably received therein and separating the interior of said tappet body member into pressure and reservoir chamber spaces, and in which the relative disposition of said plunger member within said tappet body member is determinative of the eflective length of the tappet and such disposition is dependent uponithe amount of hydraulic fluid within said pressure chamber spacez a relief valve disposed between the ends of said plunger and push rod seat members for controlling the escapeof fluid from said pressure chamber space through the annular clearance space between said plunger and tappet body members, said valve comprising; an annular sealing ring sandwiched between metal discs, said sealing ring engaging the interperipheral Wall of said tappet body member for closing said annular clearance space, said valve being responsive to fluid pressure conditions built-up within said clearance space next adjacent thereto for separation from said plunger member and for venting said pressure chamber space, via said clearance space, to said reservoir and a wave spring received within a stepped shoulder recess provided within an end face of one of said plunger and push rod seat members, said wave spring being disposed between said push rod seat member and said relief valve in compression for biasing said relief valve in engagement with said plunger member and for holding said push rod seat member separated from said valve to provide a fluid flow References Cited in the file of this patent UNITED STATES PATENTS Johnson May 6, 1952 2,784,707

Skinner Mar. 12, 1957