US 2888837 A
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Description (OCR text may contain errors)
June 2, 1959 c. s. HELLMANN 2,888,837
ADJUSTABLE CAM MECHANISM Filed Feb. 28, 1957 INVENTOR. (Iv/r1. S. bnLMmv/w A r're R NsYs.
ADJUSTABLE CAM MECHANISM (Iarl S. Hellmann, Cincinnati, Ohio Application February 28, 1957, Serial No. 643,033 8 Claims. (Cl. 74568) This invention has to do with cams, and relates particularly to the provision of a cam structure composed of a plurality of relatively movable parts by means of which the operating surface of the cam may be modified or varied while the cam is in use. Essentially, the invention contemplates a hollow camshaft mounting one or more of the cam structures which are arranged to be adjusted by means of one or more adjustment rods journaled within the hollow camshaft.
The invention is particularly adapted for use as a valve operating mechanism and may be advantageously used in connection with high pressure internal combustion engines and the like to individually or collectively control the dwell of the cams while the engine is in continuous operation, thereby providing a simple and easily operated means for controlling the compression ratio, speed, torque, and horse power output of the engine. It will be understood, of course, that the invention will find utility in other mechanisms incorporating cam actions and, while in the description which follows the invention is described as it applies to the camshaft for an internal combustion engine, it is to be understood that the invention will find utility in devices other than internal combustion engines.
A principal object of my invention is the provision of an adjustable or variable cam which is of simple and inexpensive construction and comprises essentially a pair of coacting cam lobes or segments pivotally connected to a ring or collar fitted on, or forming an integral part of, a hollow camshaft in which actuating mechanism for the lobes is contained.
Another object of my invention is to provide adjusting mechanism for the cam lobes which consists essentially of one or more adjustment rods extending lengthwise within the hollow camshaft, the arrangement of parts being such that relative movement of the lobes may be effected by axial movement of the adjustment rod or rods.
Another object of my invention is the provision of individual cam lobes or segments which may be preformed and matched as required, thereby eliminating the necessity for rejecting an entire camshaft if only one cam member is damaged, poorly machined or forged; and the cam lobes may be individually forged and tempered without expensive and time consuming selective tempering, as would be necessary in the case of a conventional camshaft.
Another object of my invention is the provision of a camshaft construction in which the cam lobes or segments are interchangeable and may be readily repaired or replaced as required without disassembling the entire camshaft.
A further object of the invention is the provision of a camshaft for an internal combustion engine wherein the reciprocating and rotating weights are kept small, thus providing a better acceleration characteristic and lower internal friction, resulting in greater engine economy. Similarly, the weight and balance of the camshaft may be more rigidly controlled with a minimum amount of expense and effort and the entire mechanism requires only at entO simple and inexpensive assembly methods in that relatively few special parts are required and much of the special machining of the cams in a conventional camshaft is eliminated.
Still a further object of the invention is the provision of a simplified direct mechanical control for adjusting the cam lobes which eliminates the necessity for the numerous automatic controls now in general use on high compression engines.
Yet another object of the invention is the provision of a camshaft construction for an internal combustion engine which provides a means for selectively powering each or any combination of cylinders. This makes it possible, for test purpose, to readily access the operation of each of the internal parts of the engine without disassembly. Similarly, as a safety measure, the cam lobes for a particular cylinder of the engine may be adjusted to any value of compression pressure. Thus, should a rod bearing become defective, the load can be taken off the affected cylinder, so that the engine may be safely run until such time as it can be repaired.
The foregoing, together with other objects and advantages of the invention which will appear hereinafter or which will be apparent to the skilled worker in the art, I accomplish by those constructions and arrangements of parts of which I shall now describe certain exemplary embodiments. In order that the invention may be thoroughly understood, reference is made to the accompanying dravw'ngs wherein:
Figure l is a perspective view with parts broken away of a camshaft construction in accordance with the invention.
Figure 2 is a vertical sectional view of the camshaft taken along the line 2-2 of Figure 1.
Figure 3 is an elevational View taken along the line 3-3 of Figure 1 with certain of the parts broken away.
Figure 4 is an elevational view similar to Figure 3 illustrating an alternative position of the cam lobes.
Figure 5 is a fragmentary perspective view of one form of an adjustment rod for use with the camshaft construction of Figure 1.
Figure 6 is a perspective view of one of the cam lobes.
Figures 7 and 8 are fragmentary perspective views of alternative forms of adjustment rods for the cam lobes.
Figure 9 is a diagrammatic elevational view of an alternative form of lobe construction and activation.
Figure 10 is a sectional view through the camshaft illustrating yet another form of adjustment rods for the cam lobes.
Referring first to Figures 1 and 2 of the drawings, I have therein illustrated a camshaft construction in accordance with my invention. From the outset it will be understood that the camshaft may be of any desired length and my mount any desired number of cams arranged to sequentially or otherwise actuate the tappets or other mechanism adapted to be contacted by the cams. The camshaft 1 is provided with a longitudinal bore 2 which extends throughout the entire length of the camshaft or at least is coextensive with the cams mounted thereon. As illustrated in dotted lines, the camshaft may be journaled in a suitable set of bearings 3 and driven in any suitable manner, as by means of a drive gear 4 secured to one end of the shaft.
The camshaft is provided with one or more collars or rings 5 each having a groove or channel 6 therein. The collars 5 may be formed as an integral part of the camshaft 1, in which event the center portion at least of the groove or channel 6 will open inwardly into the bore 2; or the collars may be formed separately and press fitted or otherwise secured on the camshaft, in which event the camshaft will be provided with elongated slots adapted to coincide with the channels 6.
Each of the rings or collars 5 mounts a complementary pair of cam segments or lobes 7 and 3. As best seen in Figure 6, each of the lobes comprises a body 9 having a cam operating surface 10, a lateral projection 11 with an opening 12 extending therethrough, and a downwardly projecting nose 13. It is to be understood that the configuration of the cam lobes, particularly the contour of the cam operating surfaces 10, does not constitute a limitation on my invention in that the configuration of the lobes will be dependent upon the range or lift and dwell desired and may be widely varied.
The pairs of cam lobes 7 and 8 are received in the channels 6 and pivotally mounted to the collars 5 by means of pivot pins 14 which extend through the openings 12 in the lobes and are received in mating openings in the collars. As already indicated, the cam lobes are arranged in complementary pairs with their body portions juxtaposed in side-by-side relation and the nose portions 13 projecting inwardly into the bore of the camshaft. The cam lobes are thus mounted for pivotal movement and, as will be explained more fully hereinafter, the pivotal movement of the lobes as they expand, i.e. move outwardly, will result in a modification of the cam face which is made up of the surfaces of the coacting lobes 7 and 8.
The cam lobes are adapted to be actuated by means of an actuating rod 15 which is slidably received in the bore 2 of the camshaft. The cross-sectional dimensions of the actuating rod will be such that the rod will contact the nose portions 13 of the cam lobes, and, as the actuating rod is moved longitudinally, the nose portions will follow the surface of the rod which will be inclined or otherwise configured to cause the cam lobes to pivot inwardly or outwardly, as the case may be. In this connection, it may be pointed out that the cam lobes are arranged to afford a constant contact between the nose portion of each lobe and the actuating rod. In most instances the tappets or other operating parts contacted by cam lobes will provide the force necessary to maintain the constant contact between the nose portions of the lobes and the actuating rod. However, if desired or required, and as best seen in Figures 3 and 4, the lobes may be biased inwardly by means of compression springs 16 seated in sockets 17 and bearing against the undersurfaees 18 of the lobes. It will be understood that the springs will be so chosen that their compressive force will be suflicient to maintain the lobes in firm contact with the actuating rod at all times and to prevent the lobes from loosening or separating from the actuating bar when the camshaft is rotated.
The actuating rod may be formed in a number of different ways. As seen in Figure 5, the rod may be of polygonal cross-section so as to have a plurality of faces 19 against which the nose portions 13 of the cam lobes will hear. The number of faces or sides does not constitute a limitation on the invention and may be varied depending upon the number of cams to be actuated. For example, the rod may be square, hexagonal, octagonal or otherwise depending upon the number and positioning of the cams. In a preferred embodiment of the invention, the actuating rod is provided with longitudinally inclined ramps 20, which, as best seen in Figure 2, are positioned to underlie the cam lobes and provide a bearing surface for the nose portions of the lobes. The nose portions may be conveniently ground or otherwise conformed to the inclination of the ramps, thereby assuring positive line contact (metal to metal contact) between the nose portions of the cams and the ramps. It will be apparent from Figure 2 that as the actuating rod 15 is moved in the direction of the arrow A, the nose portions of the cams will follow the upwardly inclined ramps, thereby effecting an outward movement of the lobes from the position of Figure 3 to the position of Figure 4. When the. avil ating 4 rod is moved in the opposite direction, the lobes will be moved inwardly under the influence of the valve tappets and/or the springs 16. Movement of the actuating rod may be by hand or the rod may be connected to a suitable fluid, mechanical or electrical actuator.
As seen in Figure 7, the actuating rod may have its sides or faces helically disposed, as at 21, in which event the nose portions of the lobes will follow the path of the helical faces as the actuating rod is moved longitudinally within the bore of the camshaft. Alternatively, the actuating rod may take the shape shown in Figure 8 wherein it is composed of a plurality of tapered sections 22 against which the nose portions of the lobes will bear. The rod will be composed of as many tapered sections as are required and, depending upon the positioning of the cams, one or more pairs of lobes may be actuated by each section.
If desired, a plurality of actuating rods may be substituted for the single rod hereinbefore described, thereby permitting individual adjustment of the cams. Thus, as seen in Figure 10, the actuating rod may be composed of a plurality of tapered bars 23 arranged about a core 24, the arrangement of the bars being such that they may be individually moved relative to each other in the direction of their length. With this arrangement, each of the bars will control the movement of a different pair of lobes. It will be understood, of course, that each of the bars will be provided with means to effect the desired movement of the lobes. For example, the bars each may be provided with one or more ramps, such as the ramps 20, or they may be helically disposed so as to operate on the principle of the actuating rod of Figure 7.
As seen in Figures 1 and 2, lubricating holes 25 are provided in the camshaft so that all of the parts may be properly lubricated. Since the cam shaft is normally operated within a bath of oil, the oil may readily pass through the openings and flow along the longitudinal bore.
Figure 9 illustrates a modified embodiment of the invention wherein the cam lobe 26 is adapted to be actuated by means of a spreading member 27 lying between the actuating rod 15 and the cam lobe. It will be understood that the cam lobe 26 will be pivoted, as at 28, to a collar on the camshaft. The cam lobe has a cam surface 29 which will provide the entire contacting surface. The lobe may be configured as desired so as to vary the lift and dwell of the valve or the like contacted thereby. In additon, it may be observed that the spreading member 27 could be formed as an integral part of the lobe 26, in which event the spreader member would correspond essentially to the nose portions 13 described in conjunction with the embodiment of Figures 1 through 4.
In accordance with the foregoing description, it will be apparent that the size, shape, height and dwell of the cams may be readily controlled and adjusted while the camshaft is in operation. As applied to an internal combustion engine, the adjustment of the cams permits control of the compression ratio, speed, torque, and horse power output of the engine, the cam lobes being readily adjustable from the retracted position of Figure 3 to the expanded position of Figure 4. Yet the construction of the parts is simple and sturdy, and the parts may be readily replaced. The individual cam lobes may be preformed and matched as required, and the individual lobes can be individually hardened or otherwise treated as may be required for any particular usage. Where a separate actuating bar is provided for each cam, individual adjustment is provided Which, in the case of an internal com bustion engine, permits the cylinders to be selectively powered, and should any cylinder become inoperative during the operation of the engine, the cam for the valve of the inoperative cylinder may be adjusted so as to relieve the strain on the camshaft, crankshaft, piston assembly and bearings.
Modifications may be made in the invention without departing from the spirit of it. For example, the actuating rod may be provided with projecting ramps, ie inclined portions projecting outwardly from the surfaces of the bar, as opposed to the recessed ramps of Figure 5; or the actuating rod may take the form of a rack gear, the coacting pinions being formed as parts of the cam lobes. Other modifications will undoubtedly occur to the skilled worker in the art upon reading these specifications, and consequently the invention is not intended to be limited excepting in the manner expressed in the claims which follow.
Having thus described the invention in certain exemplary embodiments, what is desired to be protected and claimed by Letters Patent is:
1. An adjustable cam construction comprising a hollow camshaft having a plurality of collars mounted thereon in spaced apart relation, a recess in each of said collars of a size to receive a pair of cam lobes, said recesses opening inwardly into the hollow interior of said camshaft, a complementary pair of cam lobes received in each of said recesses and pivotally secured to said collars, said lobes each having a body, a cam surface, and a nose portion, said nose portions projecting downwardly through said recesses, and an actuating rod slidably received Within said hollow cam shaft, said rod having a separate surface thereof in contact with the nose portions of each pair of said cam lobes, the said separate surfaces each comprising an inclined ramp extending longitudinally of said rod, whereby axial movement of the rod will effect a pivotal movement of said pairs of lobes.
2. An adjustable cam construction comprising a hollow camshaft having a plurality of collars mounted thereon in spaced apart relation, a recess in each of said collars of a size to receive a pair of cam lobes, said recesses opening inwardly into the hollow interior of said cam shaft, a complimentary pair of cam lobes received in each of said recesses and pivotally secured to said collars, said lobes each having a body, a cam surface, and a nose portion, said nose portions projecting downwardly through said recesses, and an actuating rod slidably received within said hollow camshaft, said rod having a separate surface thereof in contact with the nose portions of each pair of said cam lobes, the said rod being composed of a plurality of relatively movable sections each of which defines one of said separate surfaces, the said surfaces of the sections each being inclined, whereby axial movement of said sections will efiect a pivotal movement of the said pair of lobes in contact therewith.
3. An adjustable cam construction comprising a hollow camshaft having a plurality of collars thereon lying in spaced apart relation, a recess in each of said collars of a size to receive a pair of cam lobes, said recesses opening .6 inwardly into the hollow interior of said cam shaft, a complementary pair of cam lobes received in each of said recesses, said cam lobes being pivotally secured to said collars, said lobes each having a body, a cam surface projecting outwardly beyond the collar, and a nose portion projecting downwardly through the recess in the collar to which said lobe is pivotally secured, and an actuating rod slidably received within said hollow cam shaft, said actuating rod being composed of a plurality of relatively movable sections each of which is contacted by a different pair of said cam lobes, whereby said pairs of lobes may be independently actuated.
4. The device claimed in claim 3 wherein said sections comprise a plurality of tapered bars arranged about a core, said bars being individually movable relative to each other in the direction of their length.
5. An adjustable cam assembly comprising an annular ring defining a cam surface, an elongated slot extending circumferentially of said ring so as to interrupt a segment of said cam surface, a pair of complementary cam lobes received in said slot and pivotally connected to said ring, said cam lobes each comprising a body portion having a cam surface projecting outwardly from said slot in prolongation of the cam surface defined by said ring, said cam lobes coacting to form a continuous cam surface extending between the ends of said recess, each of said cam lobes having an actuating portion projecting inwardly through said slot for contact by an actuating means, said lobes being pivotally movable relative to each other to vary the contour of the cam surface which they jointly define.
6. The cam mechanism claimed in claim 5 wherein said annular ring is formed as an integral part of a hollow camshaft, and wherein the actuating means for said lobes is slidably received within said hollow camshaft.
7. The cam structure claimed in claim 5 wherein said annular ring is a separate member adapted to be slidably received by and secured to a hollow cam shaft.
8. The structure claimed in claim 5 wherein a plurality of said cam structures are mounted on a hollow shaft, wherein said elongated slots are in communication with the hollow interior of said camshaft, wherein the actuating means contacted by said cam lobes comprises an actuating rod slidable axially within said hollow camshaft, wherein said actuating rod has a plurality of surfaces each adapted to be contacted by a different set of said cam lobes.
References Cited in the file of this patent UNITED STATES PATENTS 733,220 Krebs July 7, 1903 1,757,046 Horine May 6, 1930