US 2797673 A
Description (OCR text may contain errors)
United States atent O VALVE LIFTER Herbert H. Black, Grand Rapids, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application December 10, 1954, Serial No. 474,418 4 Claims. (Cl. 123-90) The invention relates to valve lifters for transmitting valve opening movements from a cam or other actuating means to the push rod or stem of a poppet valve, such as are employed in internal combustion engines for example, and particularly to means for retaining the parts of such valve lifters in assembled relation during installation and removal, handling, etc. The general design of such valve lifters in most common use today comprises a generally cup-shaped cylinder which is slidably reciprocable in a bore provided therefor in the engine crankcase so as to contact the engine driven cam, and a separately formed member which is thrustably supported in the lifter cylinder and serves to transmit movements of the lifter to the push rod. In hydraulic valve lifters which automatically take up all lash, i. e., operating clearance between the cam and the valve, the aforementioned push rod seating member rests on a hydraulically cushioned plunger within the cylinder. In so-called mechanical valve lifters, which do not automatically take up the valve lash, no plunger is used and the push rod seat member is instead thrustably supported on a shoulder just below the open end of the cup. In both types of constructions the push rod seating member has a relatively loose fit with the side walls of the cup, and unless retained therein by some positive means is subject to being inadvertently removed from the lifter cylinder with much consequent inconvenience. For example, in the case of the mechanica type lifters there is a tendency of the push rod seat members to cling to their push rods during removal of the push rods in the course of a minor engine disassembly operation, and either be lost or dropped into the engine crankcase, necessitating in the latter instance the removal of the oil pan at considerable additional expense of time and labor. In the case of hydraulic valve lifters, the push rod seat member has heretofore been retained by a wire snap ring which locks in place in a groove formed in the open end of the cup above the push rod seat, it being especially important toprevent its accidental removal to avoid contaminating the closely fitting surfaces of the lifter plunger and cylinder and the oil which serves as the cushion between them. There is normally a spring urging the plunger outwardly of the cylinder in such hydraulic valve lifters, and the snap ring serves as the only means for holding the parts together when the lifter is removed from the engine.
It is the principal object of the present invention to provide valve lifters of both the aforementioned types with an improved means for retaining the push rod seat against accidental displacement from its cylinder when the lifter is removed from the engine or its parts are not otherwise maintained in their normal assembled relation by the cam and push rod.
The push rod seat retaining means I have devised consists essentially of a generally flat and relatively thin washer-like member whose internal and external dimensions are such that the washer may be conveniently inserted into the open end of the lifter cylinder by application of a moderate axial force thereto, and which will 2,797,673 Patented July 2, 1957 frictionally engage the smooth bore surface of the cylinder when the installation force is removed. Thus, in accordance with my invention there is no need to provide a locking groove or other abutment surface to engage this retaining washer, as is required in conventional snap ring installations. Also, while the washer effects a suflicient grip on the bore surface of the lifter cylinder to ensure retention of the upper portion of the seat member as long as desired, removal of the retaining washer to permit disassembly of the lifter is easily accomplished by prying the same out with a screwdriver or other suitable tool which can be inserted through the washer hole to apply force against its under side. The means by which this and other objects of the invention are accomplished will be more clearly understood from the following description, having reference to the drawing wherein:
Figure l is a transverse view through a portion of an internal combustion engine showing its valve operating linkage including a mechanical lifter in accordance with my invention.
Figure 2 is an enlarged fragmentary view similar to Figure 1 showing the parts of the lifter in longitudinal section and illustrating its novel retaining means for the push rod seat member.
Figure 3 is a view similar to Figure 2 except showing the invention applied to a hydraulic valve lifter.
Figure 4 is a perspective view of the push rod seat retaining washer as used in both the Figures 2 and 3 lifters.
Referring now in detail to the drawing and first to Figures l, 2 and 4 thereof, there is shown a poppet valve 1 mounted for reciprocation in the cylinder head 2 of an internal combustion engine. The poppet valve is reciprocably actuated by a return spring 3 opposing its movement from the closed position shown when the engine driven cam 4 raises the valve lifter 5 and push rod 6 to rotate the rocker 7 about its shaft 8. The lifter, in ac cordance with conventional engine design practice, is slidably supported in a bore 9 formed in a shelf 10 located just above the engine crankcase 11. A piston 12 of the engine is shown in its working cylinder 13 formed in the upper portion of the crankcase 11, and at 14 is a removable cover provided for access to the side of the crankcase during installation and removal of the lifter 5 and push rod 6.
As shown in Figure 2 the lifter 5 comprises an assembly of a cup-shaped cylinder member 15 having an open end 16, and in which is received the lower end of the push rod 6, and a push rod seat member 17 by which thrust is transmitted between the lifter cylinder 15 and the push rod during engine operation. The particular lifter cylinder 15 illustrated is, in turn, comprised of a generally tubular wall portion 18 and a foot 19 which are made separately and subsequently permanently secured together as by placing a ring 20 of brazing metal between their abutting ends and subsequently heating to both fuse the brazing material and obtain the desired heat treatment of the respective parts. The particular manner of forming the lower end of the cup-shaped cylinder 15, however, does not form any part of the instant invention, it being sutfieient to point out that the tubular wall portion 18 is provided with a shoulder 21 below its open end 16 and that the bore or internal wall surface 22 of the tubular portion is substantially uninterrupted by grooves, recesses, shoulders, etc., between the shoulder 21 and the open end 16. The push rod seat member 17, which may be suitably formed in any desired manner as by stamping or forging from flat stock, has a central seating surface 23 which may be spherically concave as shown to socket the correspondingly shaped end 24 of the push rod 6. Surrounding this socketing portion is a flange portion 25 which loosely fits the bore surface 22 of the lifter cylinder and is adapted to overly and abut the shoulder 21 of the latter. The upper annular face 26 of this flange is generally flat and is of substantial width as shown. Overlying substantially the full width ofthe-fiange surface "surface 26 is a retaining means in the form of a generally flat and relatively thin washer 27, best shown in Figure 4. A suitable material for this washer has been found to be shim stock of SAE 1020 steel with a thickness on the order of .0l.012 inch. Although the washer may be heat treated or cold worked to increase its stiffness, such has not been found necessary to accomplish its desired function as hereinafter described. The external periphery 28 of the washer is made sufiiciently larger than the internal bore surface 22, however, as to provide a substantial diametral interference between them when the washer is inserted into the open end'l of the lifter. While the amount of such oversize will vary somewhat depending on the thickness and material used, as Well as the diameter of the particular valve lifter involved, an interference fit of .002-.098 inch has been found to provide very satisfactory results using the aforementioned shim stock in a lifter whose internal diameter of the bore surface 22 is approximately /4 of an inch. In any event, the Washer has sufficient interference fit with the bore surface 22 that when the mean plane of the Washer is substantially normal to its axis a force fit between them is obtained of sufficient magnitude to exceed any forces normally applied to the washer by the push rod seat during the handling of the lifter or during removal of the push rod from the engine. Due to the relative thinness of the washer to its diameter it has flexibility enabling it to be radially deflected out of a plane normal to its axis with the result that the washer may be pressed into place by application of a moderately light axial force, using a suitable tool (not shown) which is engageable adjacent its inner periphery 2?. The degree of force required is indicated by the fact with only .002 inch interference fit I have found that the installation can be effected by finger pressure only. After such insertion of the washer to its position shown wherein its convex underside abuts adjacent its inner margin with the relatively fiat upper surface 26 of the push rod seat member, any axial force in the opposite or outward direction as may be applied to the washer adjacent its inner margin by the push rod seat member will be resisted at an increasing rate to the extent the washer is thereby forced into a full mating engagement with the surface 26. It will be appreciated that with the push rod seating member surface 26 substantially normal to the washer axis all forces imposed on the washer by the push rod seating member in the direction outwardly of the lifter cylinder are incapable of radially deflecting the washer more than sufiicient to effect its initial flat configuration, hence the full force fit of the washer serves to restrain its dislodgement.
In the Figure 3 modification the washer 27 functions in identically the same manner as in that heretofore described, the only difference being that a push rod seat member 117 of somewhat modified form is employed which rests on the upper open end of the cup-shaped plunger 140 instead of a shoulder formed in the tubular wall of the cylinder 115. The washer 27 is installed in identically the same manner and may be made of the same material having the same relative dimensions with respect to the cylinder 115 as that referred to in Figure 2. When thus installed it functions additionally to limit outward movement of the push rod seat 117 and the plunger 14!} under the biasing force of the plunger spring 141, thereby ensuring against disassembly of the parts and consequent danger of contaminating the relatively sliding surfaces of the cylinder and plunger and the oil which is introduced from the engine lubricating system through the crankcase port 142 and lifter cylinder and plunger ports 143, 144, respectively. Such oil entering the reservoir chamber 145 formed by the hollow plunger is used 2,797,673 I i i to replenish the pressure or cushion chamber 146 between the respective closed ends of the lifter cylinder and plunger, passing thereto through the ball check valve controlled passage 147. Surrounding the check valve ball 143 is a stamped cup-shaped retainer 149 which is made of sufficiently heavy'stock to provide a stop for the plunger through engagement with the end wall 150 of the foot 19. Thus, in this hydraulic lifter the cake 149 limits movement of the plunger inwardly of the lifter cylinder under extreme leakdown conditions, and the retainer washer 2'7 limits outward movement of the plunger therefrom when the push rod 6 is removed.
It is appreciated that minor changes and modifications of the parts and their arrangement may be made without departing from the spirit and scope of the invention as hereinafter claimed.
I. In a valve lifter for transmitting valve operating thrust from an actuator to a push rod, a generally cupshaped member having its open end providing an enclosure for the adjacent end of the push rod, a seat member for said pushrod end formed separately of the cup-shaped member and thrustably supported therein below said open end, said cup-shaped member having a smooth uninterrupted bore surface between its open end and said seat member, and an annular generally flat and relatively thin washer overlying said seat member and accommodating access thereto for seating by the push rod, said washer having its outer diameter normally exceeding the diameter of said bore surface by an amount such that with application of axial force to radially deflect the same out of parallelism with the opposing surface of the seat member the washer may be inserted in said open end but which will effect a press fit with said bore surface when the washer conforms in radial configuration with said seat surface.
2.. In a valve lifter adapted to reciprocate in a bore of an engine crankcase for transmitting valve opening movements from an engine driven cam disposed below said bore, an upwardly open cup-shaped member having a smooth uninterrupted bore surface adjacent its open end, a push rod seat member thrustably supported Within said cup-shaped member and having a loose fit with said bore surface, and a retainer for limiting axial displacement of said seat member outwardly of said open end consisting of a relatively thin and flat washer of sufliciently small internal diameter'to substantially overlie the lateral extremities of the seat member and having an outer diameter normally exceeding the internal diameter of said bore surface by an amount which will permit the washer being inserted into said open end by application of axial force thereto sufiicient to radially deflect the washer out of parallelism with the opposing surface of the seat member.
3. In a valve lifter for transmitting valve operating thrust from an actuator to a push rod, a generally cupshaped member having its open end adapted to receive the adjacent end of the push rod, a smooth uninterrupted bore surface below said open end and an internal shoulder below said bore surface, a seat member abuttingly engageable with said shoulder and having an annular generally fiat surface disposed laterally adjacent said bore surface, said flat surface facing outwardly of the cup-shaped member and defining a central seating surface on the seat member for the push rod, and a generally flat washer adapted to loosely encircle the push rod and frictionally engage said bore surface for preventing inadvertent removal of the seat member from the cup-shaped member during disassembly of the push rod from the valve lifter, said washer being externally oversize relative to said bore surface to provide a press fit therebetween.
4. In a hydraulic valve lifter for transmitting valve operating thrust from an actuator to a push rod, a generally cup-shaped cylinder having its open end adapted to receive the adjacent end of the push rod and having a smooth uninterrupted bore surface below said open end, a nesting generally cup-shaped plunger slidably fitting said cylinder below said bore surface, a push rod seat member closing the open end of the plunger and loosely fitting said bore surface, and a generally flat washer adapted to loosely encircle the push rod and serving to limit axial displacement of said seat member outwardly of the cylinder, said washer having its external diameter normally exceeding the diameter of said bore surface by an amount such that with application of axial force to radially deflect the same out of parallelism with the opposing surface of the seat member the washer may be inserted in said open end but upon said washer being forced into radial conformity with said seat member surface by pressure of the seat member in the opposite direction a press fit of said external diameter with the bore surface is efl'ected.
References Cited in the file of this patent UNITED STATES PATENTS