US2742031A - Self-contained automatic tappet - Google Patents

Description

I Enzbr MAX muse/1.5K 2

April 17, 1956 M. J. TAUSCHEK SELF-CONTAINED AUTOMATIC TAPPET Filed June 25, 1953 United States atent SELF-CONTAINED AUTOMATIC TAPPET Max J. Tauschek, Lyndhurst, Ohio, assignor to Thompson Products, Inc., Cleveland, Ohio, a corporation of Ohio Application June 25, 1953, Serial No. 364,175

1 Claim. (Cl. 123-90) This invention relates to a self-contained hydraulic clearance regulator. Particularly, this invention deals with an automatic hydraulic tappet for engine valve linkages.

The invention will be hereinafter particularly described as it is embodied in a tappet for an internal combustion engine but it will, of course, be understood that the principles of this invention are generally applicable to clearance regulators and, therefore, the invention is not limited in scope to the hereinafter preferred and described embodiment.

According to this invention, there is now provided a simplified self-contained hydraulic tappet adapted to be produced without difliculty in large commercial quantities and having the parts thereof arranged for easy assembly.

The tappets of this invention include a tappet barrel or body, a valve and return spring assembly slidably mounted in the body, a choke ring or piston coacting with the valve, and a light spring for urging the choke ring toward the valve head.

A feature of this invention resides in the provision of a stemmed valve with an integral head having a plunger press fitted on the end of the stem to slidably guide the valve in the tappet body while retaining a return spring, a second plunger, and a seal on the valve stem. The press flt plunger or headpiece on the stem maintains an assembly of all of the valve parts so that they can be easily inserted as an assembly in the tappet barrel.

Another feature of the invention relates to the type of hydraulic fluid that is sealed into the tappets of this invention. This fluid is a high viscosity material with a shear rate that does not materially vary over a large range of temperatures and which is chemically inert and adapted to remain fluid without loss of components over a very wide temperature range. The fluid is sealed in the tappet for the operating life of the tappet and will not deteriorate or change its operating characteristics throughout all of the conditions encountered in engine operations in all seasons of the year.

It is then an object of this invention to provide a hydraulic clearance regulator with a valve assembly insertable as a unit into a tappet body partially filled with a high viscosity fluid having a viscosity lying between 50,000 and 1,000,000 centipoises at 75 F. and being flowable at temperatures between 40 F. to +250 F. without any loss of components.

Another object of this invention is to provide a selfcontained hydraulic tappet of the thrust load transmitting valve type wherein the valve has a plunger head pressed on the stem thereof to retain around the stem a return spring, a guide plunger and a cup-type seal.

A specific object ofthe invention is to provide a tappet which has a sealed-in hydraulic fluid which will not deteriorate or vary throughout the life of the tappet.

Another object of this invention is to provide a sealedfor-life automatic hydraulic tappet with a valve and leakv down construction accommodating the use of highly viscous fluid.

Other and further objects of this invention will be apparent to those skilled in the art from the following detailed description of the annexed sheet of drawings which, by way of a preferred example only, illustrates one embodiment of the invention.

In the drawings:

Figure 1 is a longitudinal cross-sectional view, with parts in elevation, of an engine valve linkage including a tappet according to this invention and showing the position of the tappet parts just before the engine valve is opened.

Figure 2 is a view of the tappet similar to Figure 1 but omitting the engine valve and illustrating the position of the tappet parts just after the engine valve is closed.

Figure 3 is an exploded longitudinal sectional view, with parts in elevation, illustrating the manner in which the tappet parts are assembled and showing the subassembly of the valve.

As shown on the drawings:

In Figure 1, an engine poppet valve V is reciprocally mounted for controlling the port P of an engine E. The conventional valve spring V. S. urges the valve into a closed or seated position. The tappet 10 of this invention is slidably mounted in the engine and is acted upon by the cam C.

The tappet 10 includes a cylindrical barrel or body 11 having a closed bottom 11a, and open top 11b, a smooth cylindrical bore extending from the open top to the closed bottom, and an annular recess 11d near the open top 11b and providing an abutment shoulder. The cam C actson the closed bottom 11a of the barrel 11 to raise and lower the tappet in the engine E.

A cylindrical coiled spring 12 rests on the bottom 11a of the barrel inside the bore 110 and exerts a light spring force on a choke ring 13 which is freely slidable in the bore 110. This choke ring 13 has an outer periphery 13a somewhat smaller than the bore 11c so as to provide a leakdown gap or clearance relationship between the choke ring and bore. The choke ring has a converging hole therethrough providing a tapered seating face 13b with the divergent end of the hole facing the top of the tappet barrel.

The tappet 10 has a thrust load transmitting valve 14. This valve is equipped with an enlarged head 14a having a tapered seating face 14b around the bottom thereof. The tapered seating face coacts with the tapered seat 13b of the choke ring to control flow through the hole in the valve. member has a sliding fit through a flexible type seal 15 preferably of the rubber cup type which sealingly engages both the bore 11c and the shank to confine fluid in the bottom portion of the tappet barrel 11.

A lower plunger member or guide 16 composed of metal is slidably mounted in the tappet barrel and slidably receives the shank or stem 140 of the valve 14. This plunger has a major diameter 16a with a free sliding fit in the bore 110 of the tappet barrel and a shoulder 16b is provided on top of this major diameter portion to act as a bottom support for a cylindrical coiled return spring 17 mounted in the tappet barrel. The plunger has a reduced cylindrical neck portion 16c of smaller diameter than the portion 16a which is spun inwardly or staked at its top to provide a reduced diameter portion 16d. This portion 16d slidably receives a reduced diameter portion 140 of the valve stem or shank 140. The portion 140 and 14c of the valve stem or shank are joined by a tapered shoulder 14d. This tapered shoulder will abut against the reduced portion of the plunger neck Me to limit downward movement of the plunger on the valve shank.

An upper plunger member 18 is press fitted on to the top A cylindrical shank 140 on the valveend of the shank 140 above the reduced diameter portion 14c thereof. This plunger has a shoulder 13a engaged by the upper end coil of the return spring 17. The plunger forms a head slidably fitting in the bore 11c and has a peripheral groove 18b receiving an annular seal preferably of the O-ring seal 19 therein. This O-ring seal is composed of rubber or other resilient sealing material and sealingly engages both the bore 11c of the tappet barrel and the bottom of the groove 18b.

The head or plunger 18 has a shoulder 18c at the top thereof engaged by a snap-ring which is seated in the groove 11d of the body 11 against the abutment shoulder thereof. This snap-ring 20 serves as a retainer to maintain the tappet parts in the barrel.

The top of the upper plunger 18 has a hole in the center thereof coacting with a recess 142 in the top of the shank 14c to provide a seat for a push rod, the top of a valve stem or the like. As shown in Figure l, the valve stem has a tip member seated in the head and bottomed on the recess 142 of the shank.

The bottom of the tappet barrel is filled with a high molecular weight fluid F selected from organic carbon compounds and the silicone polymer compounds. Examples of suitable organic carbon compounds are petroleum oils, synthetic lubricants, diesters, polybutanes, polyalkanes, and glycols. These materials can be compounded and mixed with oxidation inhibitors, viscosity index modifiers, and similar additives to improve their properties and bring them within a preferred range of specifications. The silicone polymers include the silicone oils as well as the more viscous bouncing putty type of polymer. The selected fluid should preferably have a viscosity between 50,000 to 1,000,000 centipoises, should not change materially in its viscosity at temperatures between F. to +250 B, should be chemically inert to the metals and sealing materials used in the tappet and should not freeze above 40 F. The material should likewise have no components which vaporize at temperatures below 400 F. and at pressures from 60 to 150 pounds per square inch.

The hydraulic fluid in the bottom of the tappet barrel is divided into a lower or pressure compartment A and an upper or storage compartment B by the choke ring 13 and valve head 14a. During assembly the cup seal 15 is bottomed on the hydraulic fluid in the storage compartment B and the spring 17 is partially compressed by fluid transferred into compartment B during assembly. This spring 17 will thus always hold the cup seal against the top surface of the hydraulic fluid and no vapor or air space will be provided. The hydraulic fluid is, in effect settled for life in the compartments A and B but if any leakage should occur past the cup seal 15, the fluid will only flow into the spring chamber between the upper and lower plungers 18 and 16 in the tappet barrel where its only effect will be to lubricate the return spring 17 and the sliding mounting of the plungers.

In operation of the tappet 10, the cam C imparts a lifting action to the tappet barrel 11 for opening the poppet valve V. The load of the valve spring-V. S. is then transmitted to the tappet valve 14 and through this valve to the choke ring 13. The choke ring and head of the valve, however, rest on the body of hydraulic fluid in the pressure compartment A and the lifting action from the tappet barrel is thereby transmitted through this trapped hydraulic fluid in compartment A to the thrust load transmitting tappet valve M and thence to the engine valve V. Since, as explained above, the choke ring has a clearance relationship with the bore 110 of the tappet barrel, some leakdown will occur around the choke ring so that the fluid can flow from the pressure compartment A to the storage compartment B. This leakdown permits the tappet valve 14 to drop in the barrel thereby shortening the assembly. The shortening of the assembly moves more of the shank or stem 14c of the valve 14 into the compartment B and thus, some of the fluid in the compartment is displaced by the stem or shank resulting in an upward movement of the cup seal to accommodate the increased displacement. The return spring 17 will be further compressed to accommodate this upward movement of the cup seal and the lower plunger 16. Of course, the return spring also is compressed as the upper plunger 18 moves downwardly toward the bottom of the tappet barrel with the thrust valve assembly.

As shown in the comparative positions of Figures 1 and 2, during the open engine valve cycle the lcakdown of the hydraulic fluid arouiid the choke ring permits the choke ring and the bottom of the tappet barrel to move closer together. However, as shown in Figure 2, as soon as the engine valve closes, the load of the engine valve spring V. S. on the tappet is removed and the tappet return spring 17 thereby becomes effective to reclaim the starting length or" the tappet assembly by forcing the upper plunger or head 13 of the valve toward the open end of the barrel. This raises the valve head 14a off of the choke ring seat 13b to place the compartments A and B in full communication. The fluid in compartment B is also under the load of the return spring 17 through the lower plunger 16 and cup seal 15 and will flow through the choke ring back to the compartment A. The light spring 12 acting on the choke ring will thus be effective to raise the choke ring toward the valve head to again seat against the head thereby placing the tappet parts in position for the next engine valve opening cycle.

Any leakage of fluid out of the compartment B into the space between the plungers 16 and 18 will be compensated by the return spring 17 which will slide the lower plunger toward the bottom of the tappet barrel so as to always maintain the cup 15 on top of a solid column of hydraulic fluid.

As illustrated in Figure 3, the tappet parts are easily assembled in the tappet barrel. Thus, the spring 12 is readily dropped into the bottom of the tappet barrel, the choke ring is easily dropped into the barrel on top of the spring 12, and the lower portion of the barrel is easily filled with hydraulic fluid from the open top of the barrel.

The valve assembly is held as a unit by placing the cup 15, the lower plunger 16, and the spring 17 around the valve stem or shank 14c and by press fitting the head or upper plunger 18 on the end of the shank. Thus provides a sub-assembly which is easily insertable into the tappet barrel. it will be noted that the shoulder 14d coacts with the reduced diameter portion of the lower plunger 1d so that the cup 15 will not be moved by the spring 17 against the valve head 14a. The shoulder thereby protects the cup seal during assembly. After the valve assembly is inserted in the tappet barrel to seat the cup firmly on top of the hydraulic fluid in the bottom of the barrel and to position the O-ring seal in the barrel, the assembly is depressed so that the head 13 will be moved into the barrel beyond the groove 11d whereupon the snap-ring is positioned around the head and snapped in the groove to hold the assembly together. Itwill be appreciated that this snap-ring is not engaged by the head 18 once the tappet is installed in a valve train. The snap-ring can, therefore, be a very light member since it is only used to retain the parts in assembled relation prior to actual installation.

- From the above description it will, therefore, be understood that this invention provides a hydraulic tappet of the thrust valve transmitting type wherein the hydraulic fluid is sealed in the tappet body and is maintained under load by the return spring of the tappet. it will also be understood that this invention provides a thrust load transmitting valve assembly which is easily inserted in a tappet barrel.

It will be appreciated that various modifications and variations may be effected without changing the novel scope of the present invention.

I claim as my invention:

A thrust valve type hydraulic tappet which comprises a tappet barrel having a closed bottom and an open top with a cylindrical bore between the open top and closed bottom, a light spring bottomed on the bottom of said barrel, a choke ring slidable in said bore and resting on said light spring, said choke n'ng coacting with said bore to provide a concentric annular leakdownclearance passageway therebetween, a stemmed thrust load transmitting valve having an integral head at the lower end thereof coacting with said choke ring to provide a concentric annular valve passage through the ring and to aid in concentrically guiding the choke ring, a movable end wall in said tappet barrel slidable on the stem of the valve, resilient means urging said end wall toward the bottom of the barrel to confine a body of hydraulic fluid in the barrel on opposite sides of the choke ring, a separate head rigidly secured to the upper end of the stem of said valve at a point remote from said integral head whereby any misalignment of said valve stem structure resulting from machining tolerances must take place at a point remote from said integral valve end and whereby said head and the choke ring are necessarily properly aligned, said separate head being slidably mounted in said bore and providing an abutment coacting with said movable end wall to retain the resilient means under load, said hydraulic fluid comprising fluid selected from the group consisting of high molecular weight organic carbon compounds and silicone polymers with a viscosity of from 50,000 to 1,000,000 centipoises at 75 F. and being flowable at temperatures from -40 F. to +250 F.

References Cited in the file of this patent

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