US3238933A - Tappet - Google Patents

Abstract

1,089,259. Tappets. JOHNSON PRODUCTS Inc. March 26, 1965 [May 25, 1964], No. 12980/65. Heading F2K. The cam follower foot 26 of a cylindrical tappet is integrally connected thereto by a reduced integral pillar 40 of circular, square, triangular, X or Y cross-section.

Description

March 8, 1966 J. w. HUMPHREYS 3,238,933

TAPPET Filed May 25. 1964 United States Patent 3,238,933 TAPPET John W. Humphreys, Muskegon, Mich., assignor to Johnson Products Inc., Muskegon, Mich., a corporation of Michigan Filed May 25, 1964, Ser. No. 369,704 4 Claims. (Cl. 123-90) This invention relates to valve train tappets for internal combustion engines, and more particularly to a lightweight, low inertia tappet.

Continued development of internal combustion engines has resulted in shorter piston stroke with markedly increased stroke rate. Overhead valve trains are consequently operated at tremendously high rates of speed in their reciprocal action. To achieve high stroke rate, the elements of the valve train should be as lightweight as possible to prevent lag due to inertia in the constantly reversing train.

One relatively heavy component of the conventional valve train is the tappet which is positioned to ride on one cam of the cam shaft. It is operable to shift the push rod, which operates the rocker arm for the overhead valve. The tappet must have an elongated body to maintain proper alignment during reciprocation in the engine block tappet bore. Also, the tappet must extend out of the bore to constantly contact the operating cam shaft cam. Since the elongated tappet must also be sturdy under the constant forces applied to it, conventional tappets, especially mechanical tappets, have a substantial weight.

It is an object of this invention to provide a tappet having significantly less Weight and inertial resistance than conventional tappets employed, without sacrificing the strength and reliability of the tappet.

Another object of this invention is to provide a lightweight tappet which actually has greater stability than conventional tappets during reciprocation in the engine block bore. Slight rocking of the novel tappet in the bore does not create a tendency to bind or score the bore walls as can occur conventionally with a tappet having a push rod on one end and a cam on the other end. The novel lightweight tappet is furthermore relatively easy to manufacture since the unique structure lends itself to automatic handling so necessary to compete in todays market.

These and several other objects of this invention will become apparent upon studying the following specification in conjunction with the drawings, in which:

FIG. 1 is a side elevational, fragmentary view of a tappet assembly in an engine block;

FIG. 2 is a plan view of the novel tappet in FIG. 1; and

FIG. 3 is a sectional view of the tappet in FIG. 1 taken on plane III-III.

Referring now specifically to the drawings, assembly includes a section of engine block 12, and a cam shaft 14 having a plurality of individual cams thereon. Each cam 16 contacts the novel tappet 18 which in turn cooperates with push rod 20 to the rocker arm (not shown) for an overhead valve (not shown).

Novel tappet 18 includes three essential portions in its elongated body. The lower end has a foot 24 with a camming surface or cam follower surface 26 on the end thereof for contacting cam 16. The opposite end of the tappet includes an elongated cylindrical portion formed of a peripheral shell-type wall 28 having a cylindrical outer peripheral surface of the same diameter over its length. The cylindrical portion extends over a major portion of the tappet, preferably more than half its length.

Extending inwardly from the upper end of the tappet is an elongated inner cavity 30 of substantial size. This cavity is axially elongated over a major share, preferably "ice about one-half, of the tappet length. It has a diameter substantially larger than the diameter of push rod 20 and of the push rod seat concavity 34 formed in the bottom of the cavity. The diameter is usually at least about twice as large as the push rod diameter. Its length is greater than its diameter. The bottom of the cavity is, therefore, solid, having concavity 34 in the center thereof. Cavity 30 is open ended and, because it has a diameter at least about twice as large as push rod 20, enables the push rod to rock back and forth in the cavity without contacting the wall.

integrally connecting foot 24 with bottom 36 of cavity 30 is a pillar portion having a reduced diameter significantly smaller than the cylindrical peripheral wall of the upper portion of the tappet. The pillar is preferably composed of integrally interconnected webbing panels or ribs 40, preferably in the shape of an X in cross section (FIG. 3). The X-shaped panel section is preferred because of the maximum strength achieved, yet lightweight. The diameter is smaller than the rest of the tappet to prevent premature bore wall scoring.

In lesser preferred forms of the invention, this pillar could conceivably be of some other configuration having sufiicient strength to support the element. For example, some of the reduced diameter configurations illustrated in the prior Patent No. 3,089,473 (assigned to the assignee herein) could conceivably be used.

Since the cylindrical upper section of the tappet is made as light as possible in weight, the peripheral shell wall is as thin as possible. It will be realized that this wall can be made unusually thin since its major function is to serve as a guide surface in the bore of the engine block 12, and really has only slight additional forces applied during operation. The normal axial and diagonal forces of the I tappet are concentrated in the zone between surface 26 and push rod seat 34, rather than over the entire length of the tappet. Hence, the forces are concentrated in foot 24, pillar 4i) and bottom 36. Since these elements are relatively close together, the diagonal forces normally imparted to a tappet are relatively small. The total distance between the push rod seat and the camming surface is preferably significantly less than half the total length of the tappet as shown. Therefore, the tappet does not tend to bind in the engine bore or score the bore walls, as is prone to occur when the push rod is engaging the tappet on the upper end of the tappet displaced the entire length of the tappet from the lower camming surface.

The improved lightweight tappet has been shown in fact to have remarkable stability during operation due to this close relationship of the push rod seat and the camming surface. Yet, it has proper alignment characteristics in the engine bore due to the elongated cylindrical shell which extends axially from the push rod seat away from the camming surface.

It is believed that those having ordinary skill in this art will readily see other advantages to this novel tappet design configuration that are not specifically mentioned herein. Also, it is conceivable that certain minor variations can be made in the particular preferred structure shown, in accordance with teachings set forth. Hence, the patent is not to be limited, in its broader aspects, to the specific preferred form illustrated in the drawings, but only by the scope of the appended claims attached hereto.

1 claim:

1. A tappet comprising: an elongated body having a foot on one end including a cam follower surface; the opposite end of said body having a peripheral cylindrical wall around a hollow, axially extending, elongated, central cavity extending from said opposite end into said body; and an integral elongated support pillar between said foot and said cavity, having a reduced cross section.

2. A tappet comprising: a camming foot; a hollow portion having a solid bottom spaced from said foot and including a peripheral wall having a cylindrical outer surface of constant diameter; and said foot being integrally joined to said solid bottom by rigid integral ribbing panels having an over-all width substantially less than the diameter of said cylindrical wall.

3. A mechanical tappet comprising: an elongated body of integral, unitary construction, having a foot on one end including a camming surface, a cylindrical section on the opposite end including a peripheral wall and an axially elongated open ended cavity having a solid bottom; a push rod seat concavity in said bottom, axially centrally of said cavity and bottom; and a connecting column between said bottom and said foot, formed of rigid integral ribbing panels of X-shaped configuration, and with an over-all width less than the diameter of said cylindrical section.

4. A tappet comprising: a tappet foot having an end camming surface; a reduced diameter elongated pillar References Cited by the Examiner UNITED STATES PATENTS 2,322,514 6/1943 Goodwin 123--90 2,891,525 6/1959 Moore 123--90 3,089,473 5/1963 Kueny 12390 FOREIGN PATENTS 647,401 8/ 1962 Canada.

MARK NEWMAN, Primary Examiner.

FRED E. ENGELTHALER, Examiner.

Claims (1)

1. A TAPPET COMPRISING: AN ELONGATED BODY HAVING A FOOT ON ONE END INCLUDING A CAM FOLLOWER SURFACE; THE OPPOSITE END OF SAID BODY HAVING A PERIPHERAL CYLINDRICAL WALL AROUND A HOLLOW, AXIALLY EXTENDING, ELONGATED, CENTRAL CAVITY EXTENDING FROM SAID OPPOSITE END INTO SAID BODY; AND AN INTEGRAL ELONGATED SUPPORT PILLAR BETWEEN SAID FOOT AND SAID CAVITY, HAVING A REDUCED CROSS SECTION.

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