US2241821A - Automatically adjustable valve tappet - Google Patents

Description

May 13, 1941. A. E. Lufiwxca 2,241,821

AUTOMATICALLY ADJUSTABLE VALVE TAPPET Filed May 29, 1940 3 Sheets-Sheet 1 flewowformzo {yaw/a a INVENTOR.

May 13, 1941. A. a-wnwxe AUTOMATICALLY ADJUSTABLE VALVE TAPPET Filed May 29, 1940. 3 Sheets-Sheet 2 INVENTOR. Qow/c o ABA/OLD Earmefl May 13, 1941. upw g 2,241,821

AUTOMATICALLY ADJUSTABLEYALVE TAPPET g fi'red May 29, 1940 a Sheets-Sheet s INVENTOR. ,Javom Ewmeo Lao/W4 a BY J A v A ORNEY.

' P d May 13, 1941 AUTOMATICALLY ADJUSTABLE VALVE TAPPET Arnold Edward Ludwig, Asbury Park, N. J. Application May 29, 1940, Serial No. 337,745

7 Claims.

each cylinder for controlling the admission of fuel thereinto. A spring is associated with each valve for maintaining the same seated inclosed position. A cam shaft is driven irom the main drive shait of the engine, and carriesa plurality of cams, there being a cam for each valve. Valve tapp'ets have been interposed between said cams and the valves for actuating the valves to open the same from the cams. In order to provide definite assurance that .the val-ves'will be fully closed at proper periods in the cycle of operation, it has been the practice .toprovide a clearance in the tappets, this being awell accepted theory in the automobile industry.

However, it for any of several reasons the clearance should become excessive, anoisy condition is created which is highly undesirable, and this has proven to be particularly so in the. engines of the so-called overhead-valve type.

In the copending application of Arnold Edward Ludwig, Serial No. 337,054, filed May 2 4 1940, there is illustrated and described a tappet assembly which provides a constantclearance, and which automatically adjusts'itselt to any wear or other factors which ordinarily might disturb the clearance. Suchtappet assembly is more particularly adapted for use in engines of the L head type in which there is a direct push from the'cam toithe valve'to unseat the same.

The present invention is concerned primarily with engines of the overhead valve type. and. has, as its foremost objective, the provision of a tap pet assembly designed to be interposed between an overhead valve and a cam, and which tappet assembly isautomatically adjustable to-accommodate any changing conditions which ordinarily might interfere with the clearance thereof.

In an overhead valve engine each valve is nor- 1 mally carried by a valve stem that is maintained in an upralsed position by a spring to seat the valve in sealing position. 'A rocker arm is pivarm, and is interposed between said end and the respective cam on the cam shait. Thus as the cam shaft is rotated, said push rod is raised upwardly to raise the end of the rocker arm with which it engages, whereby the other end of said rocker arm is depressed to depress the valve stem and open the valve. y

In' accordance with the present invention the rocker arm is mounted on a pivot pin which is eccentrically mounted on a bearing that is rotatably carried by the engine block. An important object 01' the invention is the provision of means which is associated with said bearing-tor maintaining said end of the rocker arm in engagement with the upper end of said valve stem. When such an arrangement is employed it becomes necessary to provide for a clearance in the tappet assembly. Accordingly, another highly important object of the invention is the provision oi push rod mechanism between said cam and rocker arm, and which puslr, rod mechanism includes means for providing a clearance in the tappet assembly.

Particular'objects and advantages of the invention are associated with the manner in which this clearance in the push rod assembly isobtained. Other particular objects and advantages of the invention are intimately tied up with the be hereinafter stated, as the description or the invention proceeds. v

The invention, therefore, comprises a tappet assembly designed to be interposed between an overhead. valve and a cam for actuating the same. The tappet assembly consists of a rocker arm that'is mounted on a pivot that is eccentrically carried by a bearing that is rotatably mounted on the engine block; Associated with said bearing is means for maintaining one end of the rocker arm in engagement with the valve stem of the valve. Also included as an essential part of the tappet assembly is a push rod mechanism that is interposed between the other end of the rocker arm and said cam, and which in- .cludes means for providing a clearance in the tappet assembly.

For a full andmore complete understanding of the invention reference may be had to the following description and accompanying drawings, wherein-.-

Figure 1 is a vertical section through a portion of an overhead valve engine includiniavalve tappet assembly that isfldeslgned in accordance with the precepts of this invention,

Figure 2 is an enlarged detailed view in section throxlgh the lower end of the pushrod hiechanis Figure sisa' horizontal section in detail taken about on the plane represented by the line 3--3 Referring now to the drawings, wherein like reference characters denote corresponding parts, and first more particularly to Figure 1, the'block and head of an internal combustion engine are referred to generally by the reference character E. The engine E is formed with a cylinder ID on which operates a piston A passageway from the source of fuel supply (not illustrated) to the cylinder I is represented at |2. Just above the cylinder Hi the walls defining the passageway |2 are formed'with a conical valve seat l3. A valve I4 is of a structure complemental to the valve seat l3, and is designed to be seated therein to close the passageway |2. This'valve I4 is carried by a stem l5, which is slidably received in a bearing sleeve [5 that is carried the engine E.

The upper end of the stem |5 carries a spring bearing member I 1, and an expansion coil spring I8 is interposed between said springbearing member l1 and the engine E. This spring I8 exerts a tendency normally maintaining the valve i4 in the seated closing position depicted in Figure 1.

A cam shaft designated I9 is driven.,.by the main drive shaft of the engine in a maner wellcam engaging member 29 and the enlargement 24 on the push rod 23apart.

The cam engaging member 29 is formed with a pair of'arcuate shaped recesses 33 which are disposed substantially diametrically oppositely to one another, and the walls of the enlargement 24 about the socket are formed with recesses 24 that are in alignment with the recesses 22. A pair of arcuate abutment members 35 arepositioned in the recesses 34 and project into the recesses 33, as shown in Figure21 It will be noted that these abutment members 35 are maintained in assembled relation by the walls of the engine E that define the guide passage 22. Moreover, the abutment members 25 are smaller than the recesses 32 so that there is a certain predetermined amount of movement provided for between the cam engaging member 22 and the push rod 23.

The cam engaging member 29 carries a cam engaging head 36 that is in engagement with known in this art. A cam shown at 20 is mounted;

on the cam shaft lBjand is intended to actuate the valve H to open the same. This actuation is accomplished by the following described tappet assembly.

It will be noted from Figure 1 that the engine E is formed with a structure at 2| that provides a guide passage 22, the passage 22 being disposed immediately above the cam 20.

Referring now more particularly to Figures 2, 3, and 5, a push rod mechanism is shown as comprising a push rod 23 that carries, on its lower end, a cylindrical enlargement 24 that is slidably received in the guide passage 22. This cylindrical enlargement 24 is formed with a cylindrical socket 25 that opens downwardly. The upper wall of the socket 25, which is designated 26, is formed with a depression 21, and the upper wall of the depression 21 carries a downwardly projecting central boss 28.

A cam engaging member designated 29 is of a cylindrical formation substantially complemental to'the socket 25. This cam engaging member 29 is slidably received in the socket 25, and its upper end is formed with a spring receiving recess 30. An expansion coil spring 2| is fitted at one end of the recess 30, and at the other end is fitted about the boss 28. A second expansion coil spring 32 engages the upper wall of the depression 21 at one end and the upper wall of the cam engaging member 23 at the other. These springs 3| and 32 have a tendency to spread the the cam surface 31 of. the cam 20. As shown in Figure 2, the enlargement 24 may be provided with oil passages toprovide for lubrication of the relatively movable parts.

A pair of passages 33 extend from the upper end of the enlargement 24 into the depression 2T. Another pair of oil ducts 29 extend from the upper part of the recess 25 to the recesses 22. Additional oil ducts 40 are formed in the cylindrical outer surfaces of the enlargement 24 between the recesses 24 and the lower end thereof.

Referring now more particularly to Figures 1 and 6, a pedestal 4| is shown as upstanding from the engine E. The upper end of the pedestal 4| is reduced in thickness to provide a tongue 42 formed with a bearing, opening 42. Rotatably mounted in the bearing opening 42 is a bearing member 44. This bearing member 44 is carried by an end piece 45 that also carries a downwardly extending arm 46. A groove of arcuate cross section is designated 41, and is shown in dotted lines in Figures 1 and 6. This groove is formed on the inner face of the arm 45.

A bracket designated 48 may be affixed to the pedestal 4| in any preferred manner such as by the screw fastening elements illustrated. The bracket 43 has a bottom wall 49 against which bears the lower end of a spring 52. The upper end 'of the spring 5|] engages a ball 5| that is partially received in the groove 4|,and which engages the surface of the pedestal 4|. The bracket 48 also includes an upwardly extending part 52 that is spaced from the pedestal 4|, and which acts as a stop for the arm 45.

A pivot pin 53 projects outwardly from the bar 44 and is disposed eccentrically with respect to the axis thereof. The free end of the pivot pin 53 is formed with a threaded socket 54, a rocker arm referred to in its entirety by the reference character 55, and a hub portion 56 formed with a bearing opening 51 which receives the pivot pin 53. A retaining screw 58 is threaded into the socket 54, and maintains the rocker arm 55 assembled on the pivot pin 53. This also serves to maintain the bearing 44 assembled in the bearing opening 43.

A rocker arm 55 carries a head 59 at one end which engages the upper end of the valve stem. The other end of the rocker arm 55 is formed with a depression 60 in which is fitted the upper end of the push rod 23 which is rounded, as shown at 6|. The operation of the above-described tappet assembly may be described by noting that the springs 3| and 32 normally maintain the cam engagingsmember 23 and the push rod 23 in a relatively spread apart position. Thus the head 36 of t cam engaging member 29 is always in eng ement with the cam surface 31 of the cam Also, the rounded end ii of the push rod 2 is in snug en a ement with the surface of t pressionil).

Moreover, thespring 50 tends to move the ball 5| upwardly. -Thus the ball 51 acts as a wedge, tending to" spread the arm 41 apart .from the pedestal 4!. Thus there is a tendency for the bearing 44 to rotate, and due to the eccentric arrangement of the pivot pin 53 the pivotal mounting of the rocker arm 55 is moved downwardly. Thus the end 53 of the rocker arm 35 ls maintained in engagement with the upper end of the valve stem l5.

When the cam 20 rotates from the position shown in Figure 1, in which it will be noted the valve i4 is in closed position, the initial movement of the cam tends to close the clearance of the tappet assembly; that is the member 28 is moved upwardly with respect to the push rod 23 just as far as is permitted by the clearance be:

tween abutment members 35 and recesses 33. When this clearance is closed, further rotation of the cam 20 causes a positive actuation of the push rod 23 to unseat the valve l4 from its After the cam is rotated through 180, the spring l8 urges the end 59 of the rocker arm 55 upwardly as the valve l4 returns to its seated position; Thus the other end of the rocker arm is moved downwardly, causing the push rod mechanism to also be moved downwardly. Ii, after continued use of the engine, there should be any wear aslbetween the valve stem I! and the end 59 of the rocker arm, or should carbon deposits be built up on the conical seat l3 or valve l4, or should-any other factors arise which ordinarily might disturb the relative disposition of the parts, the same will be accommodated by the automatic adjustment provided by the eccentric bearing arm 46, wedge ball iii and spring 50.

A slightly modified form oi! the mechanism that. is associated with the bearing for the rocker arm is' depicted in Figure 7. In this form of theinvention the wall of the pedestal opposite to the arm 46 is formed with a spring receiving recess-6'2. A similar recess is formed on the opprovided for the insertion of a small tool to press against ball 36 to effect the release.

It will be noted that the part 52 of the bracket 48 acts as a stop limiting outward movement of the arm 46; this being true for the modification of Figure has well as the form of Figure 6.

While preferred specific embodiments of the invention are hereinbefore set forth it is to be clearly understood that the invention is not to be limited to the exact constructions illustrated and described, because various modifications of these details may be provided in putting the invention into practice within the purview of the i said pedestal, and an expansion spring engaging said bracket at one end and said ball at the other, said spring and ball exerting a tendency to spread said arm apart from said pedestal to rotate said bearing member.

2. A valve tappet assembly of the character described comprising push rod mechanism, a rocker arm having one end in operative e ement with said push rod mechanism and its other end adapted to operatively engage a valve stem, a pedestal formed with a bearing opening,

posite face of the arm 46. such recess being shown An expansion spring 64 has one end received in the recess 63 and the other end received in surfaces, one end of each of which merges in with the bearing surface 43. A clutch ball element 66 is positioned in each of the grooves 65, and an expansion spring 61 is associated with each clutch ball element. When the bearing member 44 is positioned within the bearing opening 43, the arouate grooves 35 provide what are, in efl'ect, tapered recesses, and thespring 61 normally urge the balls 66 to-the smaller end of the recesses. Thus rotation in a clockwise direction, such as caused by the spring 84, is permitted. However, rotation in a reverse direction is prevented by this overrunning clutch mechanism. In order to release eccentric bearing 44 for the purpose of reverse rotation a bore. 63 is a bearing member rotatable in said opening, a pivot pin eccentrically carried by said bearing member, said rocker arm being mounted on said pivot pin, overrunning clutch mechanism disposed between said bearing member and said pedestal whereby rotation of said bearing member in only one direction is permitted, and means associated with said bearing member tendingto rotate said bearing member in the direction in which rotation is permitted.

3. A valve tappet assembly of the character described comprising push rod mechanism, a rocker arm having one end in operative engagement with said push rod mechanism and its other end adapted to operatively engage a valve stem, a pedestal formed with a bearing opening, a bearing member rotatablein said opening, a pivotpin eccentrically carried by said bearing member, said rocker arm being mounted on said pivot pin, overrunnlng clutch mechanism disposed between said bearing member and said pedestal whereby rotation of said bearing member in only one direction is permitted, an arm carried by said bearing member, and an expansion spring interposed between said arm and said pedestal, said spring tending to rotate said bearing member in the direction in which'rotation is permitted. s

4. A valve tappet assembly of the character described comprising push rod mechanism, means included in said push rod mechanism for providing a clearance in said tappet assembly. a

rocker arm having one end in operative engagement with said push rod mechanism and its other end being adapted to operatively engage a valve stem, a pedestal formed with a bearing opening, a bearing member rotatably mounted in said bearing opening, a pivot pin eccentrically carried by said bearing member, said. rocker arm being mounted on said pivot pin, means for rotating said bearing member, and stop means for limiting rotation of said bearing member.

5, A valve tappet assembly of the character described comprising push rod mechanism, a rocker arm having one end in operative engagement with said push rod mechanism and its other end adapted to operatively engage a valve stem, a pedestal formed with a bearing opening, a bearing member rotatable in said opening, a pivot pin eccentrically carried by said bearing member, said rocker arm being mounted on said pivot pin, spring means associated with said bearing member tending to rotate the same, and

stop means for limiting rotation of said bearing member.

6. In a valve actuating assembly including a push rod, a pivoted rocker arm supported by a pedestal, and a spring closed valve, the improvement of which comprises a bearing eccentrically said guide, and means for urging said wedge member into said guide to cause said lever arm to rotate said bearing and alter the axis of oscillation of said pivoted rocker arm.

7. In a valve actuating assembly including a push rod, a pivoted rocker arm supported by a pedestal, and a spring closed valve, the improvement of which comprises a bearing eccentrically supporting said pivoted rocker arm in said pedestal, a lever arm carried by said bearing and arranged with respect to said pedestal to form an intervening wedge guide, a wedge member in said guide, means for urging said wedge member into said guide to cause said lever arm to rotate said bearing and alter the axis oi. oscillation of said pivoted rocker arm, and means for limiting rotation of said lever arm and bearing.

ARNOLD EDWARD LUDVIG.

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