US2983991A

US2983991A - Valve tappet and method of making

Info

Publication number: US2983991A
Application number: US567118A
Authority: US
Inventors: Carlson Ernest
Original assignee: Chrysler Corp
Current assignee: Old Carco LLC
Priority date: 1956-02-23
Filing date: 1956-02-23
Publication date: 1961-05-16
Anticipated expiration: 1978-05-16

Description

y 1961 E. CARLSON 2,983,991

VALVE TAPPET AND METHOD OF MAKING Filed- Feb. 23, 1956 INVENTOR. $777652 647K907! WMJLH United States Patent VALVE TAPPET AND METHOD or MAKING Ernest Carlson, Detroit, Mich., assignor to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Filed Feb. 23, 1956, Ser. No. 567,118

3 Claims. (Cl. 29156.7)

This invention relates to a valve tappet or similar device and to the method of making same.

It is a primary object of this invention to provide an improved, low cost, light weight, wear resistant, readily manufactured, mechanical valve tappet that lends itself to high speed, accurate, production by a simple, inexpensive method.

It is another object of this invention to provide a method of manufacturing valve tappets that eliminates a major portion of the former required machining operation of such elements and also eliminates all waste of material while at the same time insuring accurate formation of the push rod journal seat on the valve tappet.

It is still another object of this invention to provide a valve tappet having a minimum weight and a minimum of open chamber space in which oil or the like might accumulate and thereby vary the Weight of the tappet and cause unbalance in the valve gear.

It is a further object of this invention to provide a mechanical tappet formed from a tubular body element having an interior web portion intermediate the length thereof that divides the tubular element into a pair of longitudinally spaced apart chambers, said web providing a push rod journal surface interiorly of one of said chambers, one of said chambers being shaped to receive the journaled end of the associated push rod, and the other of said chambers being closed olf by a cam engaging wear cap.

It is a further object of this invention to provide a method of tappet manufacture that comprises cold extrusion of the tappet by a pair of simultaneously acting, oppositely disposed die punches.

Other objects and advantages of this invention will become readily apparent from a reading of the following description and a consideration of the related drawings wherein:

Fig. 1 is a fragmentary sectional elevational view of a portion of .an engine valve operating mechanism utilizing a valve tappet embodying this invention;

Fig. 2 is an enlarged sectional elevational view of the valve tappet shown in Fig. 1;

Fig. 3 is a sectional elevational view similar to Fig. 2, of a modified form of valve. tappet embodying this invention; and

Fig. 4 is a sectional elevational view of an extrusion die mechanism for cold extruding valve tappets in accordance with this invention.

It has formerly been the conventional practice in the forming of mechanical valve tappets to take a cylindrical stud of cast iron or some other suitable metal or alloy thereof and to machineout the interior portions at one end of the stud to provide a cylindrical recess that would receive one end of a valve rocker push rod. This machining operation was costly and time consuming and it wasted a good portion of the stud material. In addition it was quite difficult to center and accurately machine the push rod end seat in the stud recess by a process that By the method herein disclosed a relatively lightweight,

accurately formed, valve tappet is produced by a fast, inexpensive, cold extrusion process such that there is no Waste of tappet material during the forming process and at the same time the push rod seat on the tappet interior web is formed by a process that will insure accuracy irrespective of a high rate of tappet production. It is important to have each tappet identical to the other so that there will not be weight variation or push rod misalignment in the sets of tappets for any engine that could cause unbalance in a valve operating mechanism utilizing a set of these valve tappets.

Referring to the drawings, Fig. 1 shows an engine E with a cylinder head 2 having a cylinder charge inlet or exhaust port valve seat 3. A spring loaded valve V having a head portion 4, engageable with the seat 3, is connected by its stem portion 5 to a washer 6. Threaded about the valve stem 5 and compressed between the washer 6 and the cylinder head 2 is a valve spring 7. The free end 5a of valve stem 5- is rounded off to provide a cam surface engageable with a similar type of cam surface So on one end of the valve rocker 8. Valve rocker 8 is essentially a lever that is pivotally supported intermediate its ends, on a rocker shaft 9. The other end portion 10 of the valve rocker 8 is formed with a hemispherically shaped, concave recess (not shown) that receives the round upper end 11 of the push rod 12. The lower end 13 of the push rod 12 is rounded and arranged to seat in a mating, concave, hemispherically shaped recess 14 formed on the interior web 23 of tappet T. Valve tappet T is reciprocably mounted in a bore 15 formed in a portion 16 of the associated engine block. The closed lower end 18 of valve tappet T is arranged to be vertically reciprocated by means of its sliding engagement with the cam 19 that forms a part of the rotatable engine camshaft 20.

As this invention relates only to the valve tappet T, and its method of manufacture, no additional explanation or description of the engine E, or its associated parts, other than the tappet T, is thought to be necessary.

Valve tappet T is composed of two parts, a substantially hollow tubular body portion 22 and the cap element 18 that is fixed to and closes off one end of the tube 22. The tube 22 is not a true hollow tube for it has a web portion 23 extending across the interior thereof at substantially the mid-length of the tube so as to divide the tube 22 into a pair of spaced apart upper and lower chambers or recesses 24 and 25 respectively. The upper recess 24 is adapted to receive and journal the rounded lower end 13 of the push rod 12 and for that reason an accurately formed hemispherically shaped push rod seat 14 must be provided on the inner closed end or bottom Wall of the cup-shaped upper recess 24. From the seat portion 14 the side walls 24a of the upper recess 24 diverge outwardly towards the open upper end of the tappet T. The diverging side walls 24a of the recess 24 permit the required transverse rocking of the push rod 12 about its seat 14 without tappet body interference.

The lower recess 25 in the tappet T is of substantially cylindrical shape, in Fig. 2 form, and its lower end is closed by the cap member 18. The cap 18 is preferably of hardenable cast iron or some similar material that exhibits excellent wear characteristics when in rubbing engagement with the rotatable cam element 19. Cap 18 is connected to the lower end of tube 22 by welding or some similar bonding means or by a mechanical attaching means. When the cap 18 is fixed to the lower end of the tube 22 then the lower chamber 25 is sealed off and it can not provide an open ended chamber that might receive and retain lubricating oil or any other material that might seriously affect the weight balance of the tappet.

It will be obvious from the above description that a tappet of the disclosed design is substantially a hollow tube of minimum weight wherein a centrally located web portion 23 provides an integral seat 14 for the lower end of the push rod 12. By forming the cap 18 of a hard, long wearing, material and attaching this cap 18 to the lower end of the tappet tube 22, it is possible to use a less expensive, relatively light weight material for the tube portion 22 of the tappet T. The advantages of a hollow light weight tappet are well known and need no further discussion. Furthermore, by restricting the open-ended upper recess 24 to a size merely large enough to accommodate the rocking movement of the lower end of the push rod 12, the minimum size open-ended tappet chamber 24 is provided and thus oil accumulation in the open chamber 24 can have less eifect on the balance or inertia of the tappet and the associated valve operating mechanism.

A primary part of this invention is the method of making the improved tappet T. This tappet T lends itself to formation by a cold extrusion process. With such a process, see Fig. 4, a relatively small stud 30 of some metal such as low carbon steel, aluminum alloys, or any non-ferrous extrudable material, is placed in the tubular bore 31 of a die D that has open ends. After mounting of the metal stud 30 in the tubular bore 31 of die D, a pair of male punches 32 and 33 are simultaneously forced into the bore 31 from the opposite ends thereof. Each of the punches 32 and 33 is of a smaller diameter than the bore 31 so that portions of the metal stud 30 may be extruded backwardly along the sides of the punches as the punches 32, 33 are driven into the die bore 31 towards one another. The cold extrusion process works the metal of stud 30 during the formation of the tappet T and improves its physical properties. The shape of the punch 32 can be readily varied to provide the exact shape of push rod seat 14 and clearance chamber 24 that is desired. Furthermore, each push rod seat 14 on any group of tappets T will be substantially identical to all other tappet seats because there is not the tool wear problem with a die punch 32 that is present when cutting tools are used to form the push rod seat by a machining operation. Operator skill is not required to effect accurate push rod seat formation by an extrusion process whereas accurate formation of the push rod seat by a machining process does require operator skill, considerable time, and expensive, well serviced, machining equipment. Furthermore, with the extrusion process, tappet formation is fast and there is no loss of material during the tappet formation process. On the other hand, a machining process produces considerable loss of material as Well as loss of time that is quite valuable. It is thought that the formation of an interior web in a tubular valve tappet by an extrusion process wherein the web is formed with an integral .seat for the push rod, is a new and novel invention that distinguishes this tappet and its method of making from the prior art.

Fig. 3 shows a second form of tappet T wherein the tubular body portion 22' is formed by a pair of die punches of identical tapered configuration. Under such circumstances the chambers 24 and are identical and each includes a push rod seat 14' and 14". The web 23 may be somewhat thicker than the web 23 of the tappet T but there is still a considerable saving in material over a tappet of this type formed by a machining process. One advantage of the tappet T is that the cam cap 18 can be attached to either end of the body 22 and this will speed up the manufacturing process for then care need not be exercised in determining which end of the tappet tubular body portion 22 should have the cap 18 affixed thereto. The cap 18 can be attached to either end of the tubular body portion due to the fact that the tappet body T is symmetrical with opposite ends identical.

I claim:

1. The method of making a valve tappet comprising cold extruding a tubular tappet body portion from a solid stud of extrudable material by simultaneously forcing a pair of rounded end male punches against the opposite ends of said stud while said stud of material is mounted in an open-ended cylindrical die of greater diameter than said punches, applying compressive forces to said opposite ends of said stud by said punches to cause portions 7 of said stud material to be extruded rearwardly from said stud around each of said punches toward the open ends of said die while reshaping the stud material between the punch ends to simultaneously provide a narrow imperforate push rod supporting web therebetween, said compressive forces causing said punches to penetrate said stud sufficiently to form a pair of deep, rounded bottom, outwardly opening, oppositely disposed, cup-shaped chambers in the stud ends having said web of stud material therebetween with the rounded bottom of one of said chambers providing an integral push rod seat, and thereafter aflixing a cap member to the open end of the other one of said chambers to seal off the opening thereto.

2. The method of making a valve tappet as set forth in claim 1 wherein the punch applied to said stud to form the chamber with the seat therein is shaped to provide a rounded end chamber with outwardly diverging wall portions.

3. The method of making a valve tappet as set forth in claim 1 wherein the punches applied to said stud to form the chambers therein are identical.

References Cited in the file of this patent UNITED STATES PATENTS 1,247,366 Brockway Nov. 20, 1917 1,543,438 Hutt June 23, 1925 1,594,471 Short Aug. 3, 1926 1,674,310 Topping June 19, 1928 1,798,738 Hoern Mar. 31, 1931 1,848,083 Wetherald Mar. 1, 1932 1,971,083 Schlaa Aug. 21, 1934 2,055,341 Dyer Sept. 22, 1936 2,089,478 Heiss Aug. 10, 1937 2,247,278 Daisley June 24, 1941 2,280,753 Essl Apr. 21, 1942 2,564,902 Houser et a1. Aug. 21, 1951 2,891,525 Moore June 23, 1959