US 3101077 A
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Description (OCR text may contain errors)
Aug. 20, 1963 J. H. ENGLE ROLLER TAPPET CONSTRAINING DEVICE Filed June 21, 1962 INVEN TOR. ./5N6L & ATTORNEYS J0 N H BY United States Patent 3,101,077 ROLLER TAPPET CONSTRAINlNG DEVICE John H. Engle, 1044 Maple St, Santa Monica, Calif. Filed June 21, 1962, Ser. No. 204,258 6 Claims. (Cl. 123-99) This invention relates generally to components employed in internal combustion engines and more particularly to a novel roller tappet constraining device or guide useful in high quality internal combustion engines such as used in racing cars.
Conventional tappets are employed to actuate push rods in an internal combustion engine. Towards this end, the tappets are arranged to reciprocate within suitable bores in the engine block. This motion is provided by a cam shaft having cam surfaces circumferentially and axially spaced in such a manner as to actuate the roller tappets and thereby move the push rods in the proper sequence for operating the cylinder valves in the internal combustion engine.
In most commercial automobile engines, the lower ends of the tappets constitute smoothly rounded surfaces that simply ride on the cam surfaces, there being provided suitable oil lubrication. In higher quality internal combustion engines, such as used in racing or sports cars, it is common practice to employ roller tappets wherein the lower ends of the tappets themselves are provided with rollers for riding on the cam shaft sur faces to provide a smoother action, less friction, and greater accuracy in the actual movements taking place by minimizing wearing of the engaging surfaces. It is with this latter type of tappet that the present invention is concerned.
i It has been found that the roller type tappets may [tend to rotate within the bores in the engine block after being subjected to their normal reciprocal motion by the cam shaft. When rollers are used, slight rotations Otf the tappets will misalign the rollers themselves with the direction of motion of the cam surface with [the result that some sliding action will take place rather than rolling action. This sliding action is undesirable not only because of friction but because of resulting wear which may render the motion erratic and inaccurate.
Ilt is possible, of course, to avoid the above problem by providing a small key in the tappet adapted to fit within a vertical groove in the engine block bore to constrain the tappet against rotation. This solution, however, requires an expensive machining operation on the engine block.
Since it is common practice for individuals themselves to start with a conventional internal combustion engine, as from a stock automobile, and rework the same to provide an improved racing car type engine, it is preferable to avoid expensive machining operations. It has, therefore, been the practice to provide some other type of means coupling adjacent roller tappets together to prevent their rotation and yet permit the desired vertical motion. Such means, however, has generally required a modification in the push rods in order to avoid interference between the push rods and the constraining means. Moreover, any such means is usually only useful on the particular engine for which it is designed.
With all of the foregoing in mind, it is a primary object of this invention to provide an improved device 3,101,077 Patented Aug. 20, 1963 for constraining rotational movement between roller tappets in internal combustion engines.
More particularly, it is an object to provide a constraining device which does not require any modifications of the engine block bores or any expensive modification of the roller tappets themselves.
Another important object is to provide such a device in which normal type push rods may be employed and which isadaptable to engine blocks with roller tappets of varying spacing from each other so that great versatility is provided.
Still another important object is to provide a constraining device in which a small amount of play for rotational movement of the tappets may still exist so that they can properly accommodate any chance misalignments between the rollers themselves and the cam surfaces engaging the rollers.
Another object is to provide a constraining device which is extremely simple to insert and remove and in which once inserted, and the push rods assembled, an automatic locking of the constraining device in place is effected.
Still another important object is to provide a constraining device which may be formed from a single stamping operation to the end that great economy is realized in the provisionof the device.
Briefly, these and many other objects and advantages of this invention are attained by providing a constraining device in the form of a single integral resilient strip of material having opposite ends arranged to engage the upper ends of two adjacent tappets in a pivotal type coupling such that the strip is arched between the tappets. Towards this end, the opposite ends of the strip terminate in logs, the extreme ends of which are coupled to the tappets so that the push rods may pass between the legs free of engagement therewith. By effecting a loose coupling between the ends of the legs and the respective roller tappets, some slight play is provided to accommodate any misalignments of the rollers on the tappets with the cam shaft surfaces. Moreover, because of the arched construction, small variations in spacing between adjacent tappets can be accommodated so that a single strip may be adapted to many different types of engines.
The width of the cuived strip is slightly less than the outside diameter of the roller tappets but greater than the outside diameter of the push rods so that the legs at the opposite ends of the strip may straddle the push rods free of engagement therewith. This width provides sufficient strength so that it is not possible for the tappets engaged by the strip to rotate relative to each other nor relative to the engine block itself.
A better understanding of the invention will he had by now referring to a preferred embodiment thereof as illustrated in the accompanying drawings, in which:
FIGURE 1 a side elevational view partly in cross section illustrating a cam shaft and series of roller tappets with which the constraining device of this invention is employed;
FIGURE 2 is a fragmentary plan view of a portion of the structure taken in the direction of the arrows 22 of FIGURE 1; and,
FIGURE 3 is a perspective exploded view of the constraining device and roller tappets with which it is used.
Referring first to FIGURE 1, there is illustrated :a portion of an internal combustion engine cam shaft provided 'with cam surfaces such as indicated at 11. These surfaces are axially and circumferentially spaced in such a manner that proper sequential lifting of roller tappets may be effected. The roller tappets themselves are indicated at 12, 13, 14, and and are guided for up and down movement through circular bores 16, 17, 18, and 19 in the engine block 20. Suitable push rods 21, 22, 23, and 24 extend from the upper ends of the roller tappets as shown. The upper ends of these push rods in turn operate conventional type rocker arms (not shown) for opening and closing valves in the cylinders of the engine, all as well known to those skilled in the art.
The type of tappets illustrated in FIGURE 1 are provided with rollers 25, 26, 27, and 28 at their lower ends for rolling engagement with the cam surfaces. When such roller type tappets are employed, it is important, as discuss-ed heretofore, to prevent rotation of the tappets within the bores in the engine block in order that the rollers will not become misaligned with the cam surfaces. In accordance with the present invention, this rotation is prevented by constraining devices in the form of integral curved strips of resilient material associated with pairs of tappets such as the strip 29 for the tappets l2 and 13 and the strip 30 for the tappets 14 and 15.
.Since each of the constraining devices for respective pairs of tappets are identical, detail description of one will suffice for all. Thus, with reference to FIGURE 2, which illustrates a plan view of the tappets 14 and 15, it will be noted that the curved strip includes longitudinal slots 31 and '32 extending inwardly from opposite ends and terminating short of the mid-point of the strip 30. These slots, respectively, define legs 33, 34 and 35, 36. The
extreme tips of the legs themselves terminate in laterally extending pins such as indicated at 37, 38, and 32 40.
is achieved by providing s-m'all transverse openings 41 and 42 in diametrically opposite portions of the upper cylindrical end of the tappet 1'4 and similar diametrically opposite transverse openings 43 and 44 in the upper end of the tappet 15. The provision of these openings in the roller tappets is the only modification required to adapt the constraining device to any engine.- 7
To insert the constraining device, the legs such as 33 and 34 are urged together until the pins 37 and 38 are adjacent the inside portions of the diametrically opposite openings 41 and 42. The legs 33 and 34 are then released so that the pins 37 and 38' project through the openings 41 and 42. Similarly, the legs 35 and 36 are urged together to insert the pins 39 and'40 in the openings '43 and 44. in the upper end of the roller tappet 15. After the curved strip 30 has been inserted as described so as to form an arched configuration between the adjacent tappets, the push rods such as the push rods 23 and 24 may then be inserted into the upper ends of the tappets so that they are straddled by the legs. The slots 31 and 32 are of sufiicient Width and 'arcuate extent to be free of any engagement with the push rods during relative up and down motion of the tappets. On the other hand, the insertion of the push rods will prevent urging of the legs towards each other sufficiently to release the pins so that the push rods effectively lock the pins within the openings.
the roller and the cam surfaces on the cam shaft. Further, as a consequence of the arched configuration and the resilient nature of the curved strip, some accommodation of varying spacing between adjacent tappets in dif-' ferent types of engines is possible so that the curved strip is adaptable to a variety of diiferent engine constructions.
Preferably, the curved strips are formed by a single stamping operation from spring steel.
In operation, it will be evident that with the curved strips assembled, the push rods in place on adjacent pairs of tappets such as illustrated in FIGURE 1, and the cam shaft 10 rotated, the usual vertical relative motion hetween the roller tappets can take place to operate the push rods and any relative rotation between the tappets themselves and the engine block prevented.
From the foregoing description, it Will be evidentthat the present invention has provided 'a novel means for preventing relative rotation between tappets :to the end that friction and wear of the rollers on the cam surfaces is minimized. Further, the prevention of relative rotation is achieved without requiring any modification or expen sive machining operations :on the engine block, push rods, or other components with the exception of the provision of the diametrically opposite openings in the upper end of the roller tappets.
While only one specific configuration for the curved strip has been shown and described, it 'Will be evident that minor variations may be effected in its construction without departing from the scope and spirit of this invention.
What is claimed is:
1. A constraining device for preventing rotation of roller tapp'ets with respect to cam surfaces engaging said roller tappets comprising: a curved strip of resilient material adapted to he arched between the upper portions of said roller tappets with opposite ends of said strip coupled to said upper portions for pivoting movement about trans verse parallel axes, whereby vertical movement of said tappets can take place and rotation of said tappets is constrained by said strip.
2. A constraining device according to claim 1, in which said opposite ends of said strip terminate in pairs of legs having tip portions coupled to diametrically opposite points on said roller tappets such that push rods extending from said roller tappets pass respectively between said legs free of engagement With said strip.
3. A constraining device according to claim 2, in which said strip is of uniform width less than the diameter of said roller tappets and greater than the diameter of said push rods.
4. In an internal combustion engine including a cam shaft having cam surtaces, a plurality of roller tappets riding on said cam surfaces operating push rods, and an engine block having bores receiving and guiding vertical movement of said roller tappets, constraining devices for preventing rotation of said roller tappets in said bores during vertical movements of said roller tappets, each of said constraining devices comprising: a single integral curved strip of resilient material having elongated slots extending inwardly from opposite ends and terminating short of the mid-point of said strip to define pairs of legs at each end of said strip, each leg terminating in a laterally outwardly directed pin, said roller tappets having open upper cylindrical ends from which said push rods extend, each cylindrical end including diametrically opposite transverse openings adapted to receive oppositely directed pins in a loose fit from one of said pairs of logs, the next adjacent roller tappet receiving the pins of the other pair of said pairs of legs in a loose fit so that said curved strip is arched between two adjacent roller tappets, the push rods associated therewith passing upwardly through said slots in said curved strip, successive adjacent pairs of roller tappets being similarly provided with integral curved strips so that each curved strip constrains two roller tappets from rotational movement within their bores.
5. A constraining device according to claim 4, in which the diameter of said push rods is such as to prevent narrowing of said slots by urging said legs together sufiieiently to free said pins from said transverse openings, whereby the curved strip is locked to the pair of roller tappets with which it is associated after said push rods are received in said tappets.
6. A constraining device according to claim 5, in which said single integral curved strip of resilent materal comprises spring steel formed by a stamping operation.
References Cited in the file of this patent UNITED STATES PATENTS Boland Apr. 28, 1981 Trapp Feb. 8, 1938 Huber Mar. 12, 1940 Iskenderian Aug. 12, 1958 FOREIGN PATENTS Germany Sept. 16, 1922