US2749892A - Hydraulic lifter - Google Patents

Description

Jim 12, 1956 G. D. LINE HAL 2,749,892

HYDRAULIC LIFTER Filed April 3, 1952 IJ; E .L 1e

\7. se a4 IN V EN TORS E E GERALD D. LINE SIDNEY L. Rmsv BY M r/w ATTORN EYS HYDRAULIC LIFTER Gerald D. Line, Royal Oak, and Sidney L. Riley, Berkley, Mich, assignors to Eaton Manufacturing Company, Cleveland, Ohio, a corporation of Ohio Application April 3, 1952, Serial No. 280,332

2 Claims. (Cl. 123-90) This invention relates to tappets and more particularly to hydraulic tappets for internal combustion engines.

Broadly the invention comprehends the provision of a hydraulic tappet or lifter of the flat check valve type, for use in a valve gear system of internal combustion engines, which incorporates structure for minimizing or eliminating pump-up thereof.

Flat check valve type hydraulic tappets heretofore devised have been unsuccessful primarily because of the pumping-up thereof at elevated engine speeds. The presently devised tappet, through the provision of a loose or floating cap as part of the plunger construction for the tappet, has entirely or almost entirely eliminated pump-up.

Among the principal objects of the invention is the provision of a hydraulic tappet of the flat check valve type, that:

1. Is of simple and economical construction;

2. Incorporates anti-pump-up features;

3. Incorporates a two-piece plunger, wherein during operation the two pieces can move relative to one another and thus function as a relief valve; and

4. Incorporates a loose cap on one axial extremity of the tappet plunger, opposite the check valve end of the plunger, said cap being subject to fluid pressure of the plunger reservoir.

Other objects and advantages of the invention will appear from the following description taken in connection with the drawings forming a part of the specification, and in which:

Fig. l is a vertical cross-sectional view of a hydraulic tappet, embodying the invention;

Fig. 2 is a cross-sectional view taken substantially along lines 22 of Fig. l;

Fig. 3 is a top elevation view of the tappet of Fig. l; and

Fig. 4 is a fragmentary enlarged cross-sectional view of the plunger and flat check valve arrangement of the tappet.

This invention was devised primarily as a simple and economical manner of minimizing or eliminating pumpup in flat check valve type engine tappets.

Pump-up has been determined as occurring due to hydraulic tappet expansion while on the cam lobe, wherein the expansion results from vibrating action within the valve gear causing the load on the tappet to come down to a very low value and allowing the internal forces within the tappet, such as hydraulic pressure and plunger spring force, to expand it.

Through the provision of a loose cap, on one end of the plunger opposite the valve end thereof, acting as a pop-off valve, pump-up as above defined can be minimized or entirely eliminated.

Referring to the drawings for more specific details of the invention 10 represents a hydraulic tappet for incorporation in a valve gear for internal combustion engines between a cam, not shown, and pushrod 14.

The tappet 10 comprises basically a hollow cylindrical nited States Patent 2,749,892 Patented June 12, 1956 body 12 closed at one end 16, a plunger 18 reciprocable in the hollow of the body, a flat check valve 20 supported for engagement with one end of the plunger and a spring 22, arranged in the hollow of the body, axially biasing the plunger outwardly thereof.

A spring clip 24 is appropriately held in an annular groove 26, on the internal peripheral wall of the body 1'2, for limiting the outward axial movement of the plunger.

The plunger 18 consists of two parts, a sleeve member 28 and a cap member 30 appropriately arranged on one end 32 of the sleeve, the purpose of which will hereinafter appear.

The end 34 of the sleeve opposite end 32 thereof provides a fluid port or passage 36 adapted to be controlled by valve 20 and includes an axial extension 38 serving in eflect as a cage within which the valve 20 is movable. Appropriate circumferentially spaced radial slots 40 in the extension 38 provide communication between the inner confines and exterior thereof permitting of an unrestricted flow of fluid around the valve when it is unseated.

A fluid reservoir 42 provided centrally of sleeve member 28 has communication exteriorly thereof by Way of port 36 and a port 44 provided in the wall thereof. Port 44 is the means by which hydraulic fluid is supplied to the tappet for the operation thereof wherein an annular groove 46, on the outer periphery of the sleeve, is connected therewith and is in turn adapted to be continuously associated with an annular groove 48, arranged on the internal peripheral wall of the body 12.

A port 50 arranged in the wall of body 12 provides communication between the annular groove 48 and another annular groove 52 arranged on the outer peripheral surface of the body whereby as hydraulic fluid is supplied to groove 52 it can pass in a continuous path through port 50, groove 48, groove 46, and port 44 to reservoir 42.

Valve 20 as arranged in extension 38, is of smaller diameter than the internal diameter of the extension and is adapted on one axial end to have seating engagement with an annular edge valve seat 54 arranged adjacent the port 36.

The valve is confined to axial movement on one end by the valve seat 54 and at its other end by one end of spring 22, wherein the spring is of coiled construction having one end in axial abutting inward overlapping relation to a shoulder 56 formed internally of the extension 38 and its other end in axial abutting relation to the inner surface of end 16 of the body 12. Fig. 4 clearly shows the overlapping relation between the spring and shoulder whereby the valve cannot move axially beyond the shoulder 56.

Cap member 30 comprises a main body portion 58 of a diameter less than the diameter of the internal wall of the sleeve member in whose end 32 it is loosely fitted, an annular flange 60, one axial surface of which is adapted to axially abut the axial extremity of end 32 of the sleeve member, and a socket 62 extending into the main body portion 58 thereof, within which the pushrod 14 is received.

Cap member 30 is purposely made loose relative to sleeve member 28 and additionally is provided with ample clearance between the external periphery of its flange 60 and the internal peripheral surface of the body 12 so that the cap can move axially relative to sleeve 28 and thus permit of the passage of fluid from the reservoir past the end 32 of sleeve 28 as necessity arises.

Valve 20 as it operates to control the passage of fluid through port 36 serves to divide the hollow in the cylinder into high and low pressure chambers with the reservoir 42 constituting part of the low pressure chamber and the high pressure chamber constituting that volume on the axial side of the valve opposite from the port 36. As such with the tappet interposed for operation in a valve gear system. and with an axial load impressed thereon fluid is. trapped in the high pressure chamber with the valve seated. A prescribed leak-down is provided from the high pressure chamber along between the plunger and inner wall of the cylinder whereupon as it is necessary tom the tappet to be contracted the leak-down will account therefor. Expansion of the tappet as may be required to take up for wear occurring in the various component parts of the valve gear system results when the cam reaches its base circle and as spring 22 serves to bias plunger 18 outwardly of the cylinder, a temporary vacuum is created. in the high pressure chamber serving to move the valve 20 off its seat and permitting the flow of hydraulic liquid from the reservoir, in the plunger, to the high pressure chamber. Immediately thereafter the valve 20 is once again seated and the tappet in readiness for a subsequent engine valve operation.

Under normal conditions of operation of conventional internal combustion engines, bounce usually occurs in the valve gear of said engines when the hydraulic tappet of said valve gear is on the closing side of the cam. As a result thereof the component parts of the valve gear become. separated and in most instances the pushrod separates from the tappet thereby leaving the plunger free to move axially outwardly of the cylinder in which it is reciprocable. Through the provision of the loose cap 30 on the plunger a condition of bounce occurring in the valve gear will be compensated for by movement of the cap with the pushrod, wherein hydraulic fluid as supplied to the reservoir will operate to account for any cavitation resulting from the movement of the cap relative to the sleeve. Immediately as the valve gear load returns to the tappet the excess volume of fluid in the reservoir will leak rapidly past the end 32 of the sleeve and the cap 30 so as to return the tappet to substantially the same operative length thereof as it was before the closing side of the cam was reached.

With pump-up materially reduced or eliminated as herein provided, the tappet 10 is effective to compensate, as intended, for either expansion or wear in the various component parts of the valve gear through the elongation or contraction of the tappet.

While this invention has been described in connection with certain specific embodiments, the principle involved is susceptible of numerous other applications that will readily occur to persons skilled in the art. The invention, therefore, is limited only as indicated by the scope of the appended claims.

What we claim is:

1. A hydraulic tappet comprising a hollow cylinder having an open end and a closed end, a reciprocal plunger telescopically mounted within said cylinder and having a passageway therethrough communicating at one end thereof with a chamber defined by the inner end of said cylinder, an imperforate cap member loosely mounted on the outer end of the plunger freely operably axially moveable relative thereto, said cap member having a flange portion engageable with the end of said plunger and a major body portion telescopically received within a portion of said plunger with annular clearance therebetween to provide for the passage of fluid from said reservoir toward said open end of said cylinder between said cap member and said plunger, said cylinder having a pair of spaced annular grooves in the inner wall thereof, said plunger having an annular groove in the outer wall thereof, said annular groove having an overlapping relation with one of the grooves in said cylinder and'a port in the wall ofeach said cylinder and plunger, each port being in communication With the pair of overlapping grooves and said passageway to provide a continuous fluid channel.

2. A hydraulic tappet comprising a hollow cylinder having an open end and a closed end, a hollow cylindrical plunger reciprocally mounted within said cylinder, a chamber formed between the inner end of said plunger and the closed end of said cylinder, a one-way flat check valve controlling communication between said plunger and said chamber, an imperforate cylindrical cap member having a flange portion directly seated on one end of said plunger and having a major cylindrical body portion telescopically received within said plunger along a portion of the length of said plunger, the maximum diameters of the flange and body portion of said cap member being smaller respectfully than the maximum diameters of the cylinder and plunger to provide a loose, freely axially moveable fit between said cap member and said plunger, said cap member being operative to move olf its seat on the plunger to permit the passage of hydraulic fluid from said chamber toward said open end of said cylinder between said cup member and said plunger.

References Cited in the file of this patent UNITED STATES PATENTS 1,792,836 Handwerker Mar. 1, 1928 2,096,257 Moorhouse Oct. 19, 1937 2,220,336 Johnson et al Nov. 5, 1940 2,237,854 Voorhies Apr. 8, 1941 2,645,215 Moser July 14, 1953 2,654,356 Oldberg Oct. 6, 1953 2,665,669 Ellis Jan. 12, 1954 FOREIGN PATENTS 988,202 France Aug. 24, 1951

Images