June 21, 1955 A

June 21, 1955 A. W. RCKENEBACH 2,711,161 HYDRAULIC TAPPET Filed Sept. 16, 1952 Sheets-Sheet l ÆTTF|- | ?%zzzzzzzzzzzzzz INVENTOR AUGUST W. RICKENBACH ATTORAVEYS June 21, 1955 A. W. RICKENEBACH 2,711,161 HYDRAULIC TAPPET 2 Sheets-Sheet 2 S ??? È INVENTOR. AUGUST W. RICKENBACH. AT TORNEYs. 2,711,16 United States Patent Office Faterated Jurae 25, 1955 2 way, slight spurious movements delivered to the tappet are not transferred to the valves. - 2,711,161 In view of the foregoing, it will be appreciated that it is an object of the present invention to provide an im HYDRAULIC TAPPET 3 proved hydraulic tappet. August W. Rickenbach, Williamsport, Pa., assignor to Another object of the invention is to provide means Avco Manufacturing Corporation, Cincinnati, Ohio, a for improving hydraulic tappet operation which can be corporation of Delaware readily added to existing tappets at very little cost. It is also an object of the invention to provide a hy Application September 16, 1952, Serial No. 309,787 draulic tappet which will prevent the transmission of very 1 Ciaim. (Cl. 123-90) small movements to the valve linkage. Stated otherwise, it is an object of the invention to provide a hydraulic tappet, the components of which must undergo a slight The present invention relates to a component of an relative movement before the tappet will be effective to internal combustion engine, and, more specifically, to an transfer motion from a camshaft to an associated valve. improved hydraulic tappet for use in an internal combus A still further object of the invention is the provision tion engine having valves for controlling the intake or of an improvement for a hydraulic tappet which will exhaust of gases from a cylinder of the engine. significantly improve its performance without jeopardizing A problem frequently encountered in the construction any of its well-known desirable characteristics. and operation of internal combustion engines is that of Another object of the invention is the provision of a maintaining proper adjustment of the mechanical elements hydraulic tappet which will preclude the transmission of which actuate the inlet and exhaust valves. This problem spurious camshaft motions regardless of the position is aggravated by thermal expansion and contraction of assumed by the tappet while in use. This is a particularly the engine which make it difficult to maintain adjust important feature of the invention since hydraulic tap ment of the valve actuating elements. As is well-known 5 pets are widely used in the aircraft field in which engines to those skilled in this art, proper adjustment is im commonly assume a wide variety of positions while in portant, for it assures that the valves will seat fully and Se. - - prevents the actuating elements or valve linkage from The novel features that are considered characteristic holding the valves in an open position in which burning of the invention are set forth in the appended claim; the of the valves would occur. invention itself, however, both as to its organization and Because of the importance of proper adjustment, hy method of operation, together with additional objects. draulic tappets are often incorporated in engines. Basi and advantages thereof, will best be understood from cally, a hydraulic tappet incorporates a piston and cylin the following description of a specific embodiment when der assembly which is expanded by high pressure oil, read in conjunction with the accompanying drawings, in supplied by the engine, to take up the clearance within the which: valve linkage. The areas within the tappet assembly on Figure 1 is an enlarged longitudinal sectional view of a which the oil acts and the pressure of the oil used, are hydraulic tappet incorporating a spring washer in keep such that the tappet itself cannot open the valves; thus ing with the novel teaching of the present invention; proper adjustment is maintained and the valves are not Figure 2 is a greatly enlarged cross sectional view of prevented from seating properly. Hydraulic tappets, the spring washer used within the tappet assembly; and therefore, make it possible to avoid many of the difficul Figure 3 is a longitudinal sectional view through one ties previously encountered. cylinder and its associated valve actuating system of an On the other hand, hydraulic tappets are not entirely internal combustion engine, certain parts of the engine satisfactory since their inherent operation is such that all being broken away to facilitate a description of its in clearance is eliminated from the valve linkage. This be ternal construction. ?• ing the case, even slight spurious movements of the As illustrated in Figure 3, a hydraulic tappet, gener associated cam shaft are transmitted through the linkage ally designated 1, is slidably positioned in the crankcase to the valves, causing the valves to open erratically and 2 of an internal combustion engine, generally designated leading to backfiring and rough running of the engine. ; 3. Cylinder 4 of the engine is bolted to the crankcase, The source of such spurious movements is not entirely the cylinder including a cylinder head 5 in which is formed clear at this time, but it is thought that such movements a rocker box 6 covered by rocker box cover 7. Hy might result from whipping, i.e., flexing of the can shaft, draulic tappet 1 cooperates with a valve linkage, gen or shifting of the cam shaft because of excessive cam erally designated 8, the valve linkage including rocker shaft bearing clearances. On the other hand, it is thought arm 9, pivoted as at 10, within rocker box 6. The possible that the tappet may tend to bounce on its as 55 rocker arm transfers motion to valve 11 which, for con sociated cam, particularly during high speed operation. venience of illustration, is an inlet valve for admitting a Regardless of the source of spurious motions, it is a fact combustible charge to cylinder 4. As is conventional, that difficulty has been encountered in operation of en an inlet pipe 12 is connected to intake port 3 from gines having hydraulic tappets, the difficulty manifesting which the combustible charge is admitted to the cylin itself in rough running of the engine, backfiring, and 30 der by valve 11. : generally unsatisfactory performance. The engine is conventional in its provision of a re The present invention eliminates all of these difficulties ciprocating piston 14 connected to a connecting rod 15 and assures that hydraulic tappets can be used without which, in turn, is rotatably secured to a crank pin ió concern for any spurious movements delivered to the of crankshaft 17. A spark plug 18 is also provided for tappets. Briefly stated, the present invention comprises a 65 igniting the combustible charge within the cylinder, the spring-type washer disposed between two components of energy resulting from combustion being transferred to the hydraulic tappet through which motion must be trans piston 14 and crankshaft 17. ferred when the cam shaft acts on the tappet to move the While the engine is in operation, cam shaft 9 is con valve linkage. This spring-type washer permits a small tinuously rotated at one-half the rate of crankshaft 17. 70 The cam shaft includes cam 20 positioned for coopera amount of motion between the tappet components before tion with face 21 of the hydraulic tappet. In a con movement is transferred to the valve linkage and, in this ventional manner cam. 20, in the course of its rotation, 2,711,161. 3 4 imparts a periodic reciprocating movement to the hy turn the valve 1i to a fully seated position and check valve draulic tappet which, in turn, transfers this motion to 33 again admits oil to the interior of cylinder 27 to expand valve linkage 8 which operates valve 1 through the the length of the tappet and thereby take up any clear rocker arm 9. Valve springs 22 are provided within ance in the system. the rocker box, the springs being engaged with the valve 5 The foregoing description outlines briefly the oper washer 23 which is locked at 24 to the stem of the valve. ation of a conventional hydraulic tappet under optimum The springs act to hold the valve closed against its seat conditions. As has been described, however, such 25 at all times, and, thus, the valve linkage must over optimum conditions do not always prevail and occasional come the load of these springs in addition to the net gas ly very small motions are delivered by the cam shaft to forces acting on the valve before the valve can be forced O the tappet. To prevent such motions from opening the open. - valves at improper times, a spring washer 37 is provided in The particular form of engine used is not of impor an annular space 38 defined by sleeve 26 and cylinder tance to this invention, although the invention has found 27. This spring washer is shown in enlarged view in most widespread use in 4-cycle engines. In a typical Figure 2. It will be noted that the faces of the washer engine of this type, the inlet valve is opened during every 39 and 40 define conical surfaces inclined at an angle to : other revolution of the crankshaft, the inlet valve remain the axis of the washer. This type washer per se is not ing closed during the time that combustion occurs within novel. It is characteristic of this washer that it can be the cylinder and the exhaust gases are expelled there deflected from its normal position shown in Figure 2 into from. It will be appreciated that if the valve lifts off a flexed position in which faces 39 and 40 lie within paral of its seat during the time that combustion is taking place, lel planes perpendicular to the central axis.

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