US3585974A

US3585974A - Valve actuating mechanism

Info

Publication number: US3585974A
Application number: US803164*A
Authority: US
Inventors: Robert L Weber
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-02-28
Filing date: 1969-02-28
Publication date: 1971-06-22
Anticipated expiration: 1988-06-22
Also published as: FR2033124A5; DE1954456A1; AU1238370A

Abstract

The invention contemplates a valve-actuating system wherein purely longitudinal displacement is achieved upon relative rotation of members in coaxial, helically cammed relation. A number of different embodiments are disclosed whereby the desired rotation is effected, and illustrative employments are described for valve actuation derived from various cam structures, including a cam with spring-loaded follower, and a desmodromic cam, as well as block-mounted and overhead camshaft forms thereof.

Description

United States Patent Inventor Robert L. Weber 49 Clapboard Hill Road, New Canaan, Conn. 06840 Appl. No. 803,164

Filed Feb. 28, 1969 Patented June 22, 1971 VALVE ACTUATING MECHANISM 51 Claims, 17 Drawing Figs.

US Cl 123/90.12, 74/110, 251/229, 251/250, 123/90. 14, l23/90.24, 123/90.27, 123/90.28, 123/90.6, l23/90.61

Int. Cl F011 1/04, F011 l/30, F0111/32 Field of Search 123/90, 90.14, 90.24, 90.27, 90.28, 90.6, 90.61; 74/1 10; 251/229, 249, 250

Reierenees Cited UNITED STATES PATENTS 4/1917 Kessler 123/90 1,359,669 1 H1920 Buck 123/90 1,362,500 12/1920 Moeller... 123/90 1,462,160 7/1923 Anthony. 123/90 1,528,193 3/1925 Buck 123/90 1,850,544 3/1932 Gray 123/90 2,071,719 2/1937 Wurtele... 123/90 2,609,803 9/1952 Doughty 123/90 2,609,804 9/1952 Doughty 123/90 Primary Examiner-Al Lawrence Smith Altarney-Sandoe, Hopgood and Calimafde ABSTRACT: The invention contemplates a valve-actuating system wherein purely longitudinal displacement is achieved upon relative rotation of members in coaxial, helically cammed relation. A number of different embodiments are disclosed whereby the desired rotation is effected, and illustra- Live employments are described for valve actuation derived from various cam structures, including a cam with springloaded follower, and a desmodromic cam, as well as blockmounted and overhead camshaft forms thereof.

PATENTEUJUNZEIHYI 3,585 974 sum 1 OF 4 TORNE PATENTEUJUNZZIHYI 134585.974

SHEET 3 OF 4 it; i Amway IN ENTOR @amrz h/am' VALVE ACTUATING MECHANISM This invention relates to an improved motion-translating mechanism having particular utility when embodied in valveactuating mechanism of internal-combustion engines.

The poppet valve used in most of todays internal-combustion engines has survived many attempts to improve upon its simplicity and dependability. There have been numerous innovations in valve mechanisms and in methods of actuating the valve, but because of high cost, inadequate reliability, excessive complexity, or a combination of these factors, few improvements have reached the stage of mass-production, and none of these few has long survived the test of the marketplace.

Despite the apparent triumph of the poppet valve, the valve area still plagues today's high-compression engines, as a major trouble source; in contrast, design considerations for other engine parts, such as pistons, rods, crankshaft, camshaft, cam followers, heads and block have become fairly well understood and stabilized. Advances in metallurgy have made it possible to achieve a high degree of operating reliability, provided reasonable care is given to proper lubrication.

Much of the serious trouble begins in the so-called valve train, i.e. the system of push rods, rocker arms, valve guides, springs, valves, etc. Chiefly, the trouble lies in mechanical wear of the valve stem in its guide, due to an actuating force component which is other than purely axial. Such nonaxial component is attributable to several factors, including angularity" in force transmission from the rocker arm to the valve stem, and deliberate off-axis contact between the valve stem and its actuator (to impart indexed valve rotation for better seating). In operation, the valve-seat bore will depart from concentricity with the valveguide bore, and the valve stem may eventually depart from concentricity with the seat face on the valve member.

After to 10,000 miles, the average production engine has begun to wear significantly in its valve trains, for one of more of the above-noted reasons, because current design cannot help but put some side thrust on the valve stem, for every actuating stroke. Such wear impairs the ability of the valve to seat squarely, and heat-dissipation is adversely affected, with rapid deterioration in performance and accelerated wear of the valve, the valve guide and other engine parts such as pistons, rings and cylinders.

It is, accordingly, an object of the invention to provide an improved valve-train movement which will eliminate or very substantially reduce engine problems of the character indicated.

It is a specific object to provide a valve-train mechanism which is inherently free of side thrust on the valve stem, for a longitudinally reciprocating valve system; stated in other words, it is an object to provide such mechanism in which purely axially oriented reciprocating forces are generated for valve actuation.

Another object is to achieve the foregoing objects with a construction in which a net indexing rotational increment is imparted to the valve for each actuation thereof, thus reducing any tendency to form a localized hot spot" in the area of valve-seat engagement.

Still another object is to provide an improved valve-actuating mechanism which inherently assures full and uniform valve seating for very extended periods of engine operation, as compared with systems in use today.

A further object is to provide an improved valve-actuating mechanism which inherently absorbs, by direct reaction to the engine block or cylinder head, a major fraction of valve-accelerating and decelerating forces, thus reducing wear in cam and follower parts of the valve train.

It is in general an object to achieve the foregoing objects with a basically simple structure, which lends itself to economic mass-production, adjustment, servicing and replacement (if ever necessary), which may use standard valves, which inherently requires relatively low actuating forces, which is equally adaptable to conventional cam-andspring-return and to desmodromic or other cam-actuating techniques, and which involves minimum modification of other parts of the engine.

Other objects and various further features of novelty and invention will be pointed out or will occur to those skilled in the art from a reading of the following specification in conjunction with the accompanying drawings. In said drawings, which show, for illustrative purposes only, preferred forms of the invention:

FIG. 1 is a simplified fragmentary sectional view of an internal-combustion engine incorporating valve-actuating mechanism of the invention, utilizing a single block-mounted cam and spring-loaded follower to derive valve-actuating displacements;

FIG. 2 is a generally similar but more fragmentary view to illustrate the invention in the context of a desmodromic camand-follower system for deriving valve-actuating displacements;

FIG. 3 is an enlarged fragmentary view, partly broken away and in section, for better illustration of one embodiment of valve-actuating mechanism;

FIG. 4 is a view similar to FIG. 3 to illustrate another embodiment;

FIG. 5 is a longitudinal sectional view, partly broken, to illustrate alternate cam-follower mechanism usable with either ofthe mechanisms of FIGS. 3 and 4;

FIG. 5A is a fragmentary view in elevation, taken from the aspect designated SA-SA in FIG. 5;

FIG. 6 is a fragmentary view similar to FIGS. 3 and 4 to illustrate a modification;

FIG. 7 is a simplified diagram schematically illustrating a further embodiment;

FIGS. 8 and 8A are respectively simplified front and side elevations schematically illustrating a still further embodiment;

FIGS. 9 and 10 are simplified views in elevation, partly broken and in section, and schematically illustrating two further embodiments of the invention;

FIG. II is a view similar to FIG. I to illustrate an overheadcamshaft employment of the invention;

FIG. 12 is a simplified view in perspective to illustrate a modified desmodromic-cam employment of the invention;

FIG. I3 is a simplified fragmentary side view, taken at a section through the camshaft, to illustrate schematically the camand-follower parts of FIG. 12; and

FIGS. 14 and 15 are similar simplified diagrams respectively depicting pressure-fluid operated embodiments of the invention.

Briefly stated, the invention contemplates a valve-actuating system wherein purely longitudinal displacement is achieved upon relative rotation of members in coaxial, helically cammed relation. A number of different embodiments are disclosed whereby the desired rotation is effected, and illustrative employments are described for valve actuation derived from various cam structures, including a cam with springloaded follower, and a desmodromic cam, as well as blockmounted and overhead camshaft forms thereof.

Referring to FIG. 1 of the drawings, the invention is shown in application to a four-cycle intemal-combustion engine comprising a block 10 having a cylinder bore 11 for guided reception of a piston 12. A pin 13 connects piston 12 to a rod 14, the other end of which is carried at a crank 15 of a crankshaft I6, joumaled on a drive axis I7. A head 18 closes the outer end of the cylinder 11 and supports a spark plug 19, as well as gas porting such as the inlet passage 20, and guide means 21 for orientation of a poppet valve 22; valve 22 is shown in open position to permit the downstroke of piston 12 to draw combustible mixture into cylinder 11. A camshaft 23 is joumaled (by means not shown) on an axis fixed in relation to the drive axis I7 and is driven at one-half drive shaft speed by a suitable synchronizing connection, suggested at 24. In the form shown, the face of a cam follower 26 tracks the profile of a cam'27 on camshaft 23. Follower 26 includes an elongated shank which is guided in a fixed bushing 28 and which is resiliently urged by spring loading at 29 to maintain the tracking relationship.

In accordance with the invention, the conventional tappet and rocker-arm relation between cam follower 26 and valve 22 is completely replaced by mechanism whereby cam-follower reciprocation is translated into rotary reciprocation of two members, coaxial with each other and with the stem 30 of valve 22; a helically cammed relation between the two coaxial members imparts straight-line actuation of the valve stem, i.e. free of side or lateral thrust reaction on the valve stem.

in the form of FIG. 1, one of the two relatively rotatable members is basically a sleeve or nut 31, and the other is the valve-stem guide 2!, the latter being shown insertably fitted in a suitable receiving bore in the cylinder head 18 and held by a key pin 32 and a radial shoulder 33 as a fixed part of the cylinder-head assembly. Plural balls 34 ride corresponding helical raceways or grooves in axially overlapping adjacent cylindrical surfaces of members 2ll3l, so that rotary reciprocation of sleeve 31 effects corresponding but purely axial reciprocation of sleeve 3i and of valve stem 3%, carried therewith. Rotary reciprocation is imparted to sleeve 31 by reaction to the thrust of a rack 35, connected by an elongated push rod 36 to follower 26; rack meshes with helical threads 37 on the otherwise cylindrical periphery of sleeve 31. The angle a characterizes the effective inclination of the valve-stem axis with respect to the rack-reciprocation axis as viewed in FIG. ll; this angle and other related factors will be discussed in greater detail below, in connection with F IG. 3. It will be understood that rack 35 and rod 36 may be provided with greater support as necessary, as for example that indicated at boss 36' for rod 36; and boss 36 may serve the added function of a frame reference for the upper end of spring 29 in the event that the teeth of rack 35 are straight or substantially straight, the dashed outlines in FIG. 1 behind the inlet 20 may be taken as schematic suggestion of guide means on the valve body for the nonrotatable guided longitudinal reciprocation of rack 35.

The connection of valve 22 to sleeve 31 is preferably such as to permit relatively free relative rotation of these parts. In the form shown, this is achieved in the context of a light frictional resistance, occasioned by a preloaded spring 38. The reduced tail 39 of valve stem 21 passes freely through a central opening in an end wall 4MB of sleeve 31!, and spring 3% is compressed between wall 40 and a retaining washer or snap ring 41, carried at the end of tail 33; if desired, washers may be provided immediately adjacent the respective faces of wall 40, as shown.

In operation, the valve 22 is open when follower 26 is tracking the low point of cam 27. With ensuing camshaft rotation, follower 26 and rack 35 are displaced upwardly, to lift sleeve 31 and to develop clockwise rotation thereof (as viewed upwardly along the valve-stem axis); it will be understood that such rotation is the reacting result of the described helically cammed relation between members 211- 31. Valve-seating occurs just prior to tracking the high part of cam 27; spring 38 thus resiliently loads the valve-seated relation. Upon tracking the downslope of cam 27, sleeve 3H commences its return stroke before unseating valve 22; by the time valve 22 is unseated, sleeve has already begun to rotate in the opposite (counterclockwise) direction. The cycle is completed when the valve is fully open, as shown.

it will be appreciated that since torsional friction characterizes the otherwise freely rotatable relation between valve 22 and sleeve 3i, there will be a tendency of valve 22 to track the angular oscillation of sleeve 31, but that in the course of a plurality of valve cycles, there is a net unidirectional progression of valve rotation, even though sleeve 31 rotates just as much in each direction of rotary oscillation. The detailed explanation of such net unidirectional rotation (or indexing) of valve 22 is not yet completely understood, but it is believed in part to be attributable to the fact that upstroke displacement of valve 22 is shorter than that of sleeve 31, so that angular acceleration of valve 22 begins more gently on the upstroke as compared with more sudden acceleration at commencement of the valve downstroke. Similarly, angular deceleration of the valve is more gentle at the end of the downstroke than it is at the end of the upstroke. The very substantially larger valveseating area at 42 determines abrupt achievement of zero rotational speed for valve 22 at the end of its upstroke, but this is to be compared with the relatively small torsional forces available to accelerate rotation of valve 22 as it begins its downstroke. The net result is to develop more counterclockwise than clockwise rotation in valve 22, in the long run, so that the valve and its seat may be self-burnishing and assure prolonged accurate seating, with well-distributed heat-dissipation over the entire seat 42, and free of hotspot development.

In the form shown, precise adjustment of the timed seating of valve 22 is available through adjustment of the effective length of rod 36, between follower 26 and rack 35. For this purpose, rack 35 is shown threadedly engaged to one end of rod 36, with a lock nut 35' to hold the position. The other end of rod 36 is similarly threadedly engaged to follower 26 and is locked by nut means 43.

The arrangement of FIG. 2 is generally similar to FIG. 1, except that positive cam actuation develops both the upstroke and the downstroke of the follower 45. Follower 45 is shown with parallel forks 46-46 piloting on the camshaft 457 which carries a flat cam plate having a cam groove 48. A cam-follower roll 49 on follower 45 tracks the radially inner wall of grove 48 to generate upstroke movement, and it tracks the radially outer wall of groove 48 to generate downstroke movement. The other end of follower 45 is provided with a rack 50 (suitably guided by means not shown) to drive a valve-actuating sleeve 51 in the manner discussed in FIG. 1, except that since rack 50 is in front of sleeve 51 (as distinguished from FIG. 1, where rack 35 is behind sleeve 31), the helical outer rack-drive threads on sleeve 51 are shown with the opposite direction of helical advance; by the same token, the direction of helically cammed engagement between valve-stem guide 52 and sleeve 511 is the opposite of'that shown between members 21-31 in FIG. II. The net result of recycled cammed actuation of the valve 53 of FIG. 2 is the same as in FIG. ll, except that positive actuation of both strokes in FIG. 2 assures greater fidelity of valve programming under high-speed conditions, and the net rotation for incremental indexing of the valve about its axis will, of course, be the opposite of that in FIG. R.

FIG. 3 is an enlarged sectional view to illustrate an adjustable feature embodied in the valve-actuating mechanism within the coaxial structure of the sleeve 55 and valve-stem guide member 56. FiG. 3 also serves to illustrate the relation of angles involved in rack-pinion engagement and in the helically cammed engagement, respectively.

An adjustable feature within sleeve 55 employs an auxiliary sleeve 55' threaded in a counterbore at the open or tail end of the sleeve 55. Auxiliary sleeve 55' is shown with a reduced aperture in an end-closure wall 57, and the reduced tail 58 of the stem 59 for valve 60 extends through this aperture. As washer 6i seats against the shoulder defining the reduced end 58, and a spring washer 62 retains the assembly with resilient loading which, it will be recalled, is used to assure seating. Preferably, angularly registering cutouts or slots (not shown) in members 6li57, are provided to permit breathing or venting air that must be displaced during reciprocating of the valve actuator. Adjustment of the threaded advance of auxiliary sleeve 55' within the primary sleeve 55 will be seen to develop precise control of valve-stem location, so that valve 6t) may seat with the desired slight resilient loading via spring 62. Once the adjusted position is determined, a lock nut 65 is set against sleeve 55 to secure the adjustment.

FIG. 3 serves the additional purpose of illustrating presently preferred angular relationships in my valve-actuating mechanism, for the case of ball coupling between members 55 56. The angle a will be recognized as the angle between the reciprocating rack 66 and the valve-stem axis, and the rack teeth have tangential engagement with the helical threads on the outer surface of sleeve 55; the angle a is thus the complement of the angle of helical advance for these threads. The angle (1 preferably exceeds the angle B, which is the angle of advance for the helix which determines cammed action between the inner and outer members, namely the grooved part 67 of the valve-stem guide 56 and the bore of sleeve 55. Preferably, the latter engagement utilizes plural equally angularly spaced like helical grooves or raceways 68, and plural balls are received in each of these raceways. The plural balls will be understood to support the relatively rotatable members throughout the course of the actuating stroke and to assure concentricity of positioning and of the actuating thrusts.

FIG. 4 illustrates a modification wherein the rack-actuating axis 70 will be understood to be in a plane above the plane of the paper and therefore on the side of the sleeve 71 opposite to that displayed for the rack 66 and sleeve 55 in FIG. 3. The helical raceway progression within sleeve 71 is therefore shown in the opposite direction to that displayed in FIG. 3. In the modification of FIG. 4, a thin retaining sleeve 72 is positioned in the annular space between valve-stem guide 73 and the sleeve 71. This retainer is apertured at predetermined angular and axial spacings so as to retain spaced balls in the various raceways, and thus to assure an economy of balls as well as independent action of all balls in the various and respective race relationships. These results are achieved without sacrifice of the coaxial relationships discussed above whereby no offaxis thrust component is introduced in the actuation of the valve 74.

In a specific illustrative embodiment of the FIG. 4 arrange ment, as applied to a small-horsepower Briggs and Stratton engine having a l-inch diameter intake valve and a Va-inch diameter exhaust valve, each having a lift of 0.165 inch, the actuating rack travel is 0.220 inch, the angle a is about 41 42 and the angle ,3 is about 29.

FIG. 5 illustrates a modified rack structure wherein the rack member 75 is cylindrical and is formed with like circumferential grooves, contoured as rack teeth over the entire rack length. As shown, the rack 75 is a sleeve carried in the upper end of rod 76 forming part of the cam-follower structure. Rod 76 includes a circumferential shoulder 77 defining a stop for location of a coil spring 78, preloading the rack sleeve 75 against adjustable lock nuts 79 at the threaded upper end of rod 76. Preferably, the assembly of rack 75 and rod 76 is preassembled to a suitably bossed portion 80 of the cylinder head. The lower end of rod 76 may thus be guided by and project through boss 8%, and a pin 81 retains spring-preloading means 82 within the cylinder-head structure. The cam follower itself is shown merely as a rod 83 suitably guided in the engine block 34 to ride its particular actuating cam 85, and it will be understood that upon assembly of the cylinder head to the block, the follower rod structures 7683 will align, as shown, preferably with slight compressionaily loaded relief (at 86) of the shoulder 77 from the cylinder head. Rotation of cam 85 lifts the rod structure against the loading of spring means 82 and drives rack 75 through the further resilient loading 78. Rack 75 will be understood to engage a valve-stem-actuating sleeve 87 which is threaded in accordance with principles already discussed, and the spring means 78 will be available for slight further compression once the valve has attained its fully seated position. Spring means 78 will thus be understood to obviate the need for particular spring preloading within the concentric valve-actuating structure, as at 38 in FIG. 1.

FIG. 5A illustrates a preferred offset relation, to the extent identified A, between the axis of follower rod 83 and the centerline of the cam $5. This offset is such that an asymmetrical part of the end face of follower 83 is always unsupported by contact with the cam 85. In operation, this necessarily means a predominant torsional friction or drag to impart slight incremental rotation of the follower rod 83 for each cycle of the cam. Such rotation achieves a desired uniform burnishing of the cam follower end face and at the same time transmits a measure of consistent incremental rotation to the rod 76 on which the rack 75 is mounted. Thus, wear of the rack teeth is never localized at any one angular position but is rather welldistributed about the full periphery of tooth engagement with the sleeve 87.

FIG. 6 illustrates a modification in which the sleeve 90, which is driven by a rack on the axis 91, is itself engaged to the valve stem guide member 92 by means of elongated splines, as at 93. Splines 93 mate with corresponding grooves as at 94 in the bore of sleeve 90. With proper lubrication, a film of oil thus spreads torsional reaction leads over a very extensive area, thus avoiding stress concentrations in any part of the valve-actuating cycle and contributing to long life, with an assured concentric thrust development at all times. The structure is simplified by omission of the antifriction elements, and the angles a and [3 may approach equality, as suggested in the drawing.

FIGS. 7 to 9 illustrate several different alternative organizations for developing the desired valve-actuating thrusts. In FIG. 7, the externally threaded sleeve 95 for actuating the valve 96 is driven by meshing teeth 97 of a sector 98 journaled for pivotal action at 99 and deriving oscillating torques from follower arm 100 integrally formed with the sector 98. Sector teeth 97 may be straight, parallel to the pivot 99, and mesh tangentially with the external threads on sleeve 95. Cam 101 on an overhead cam shaft 102 drives arm 100 against a suitable loading spring 103.

In the arrangement of FIGS. 8 and 8A, an elongated pinion 105 meshes with the helically threaded exterior of the sleeve 106 for actuating valve 107, and it will be understood that suitable means (not shown) may be employed to translate cam actuation into driven rotary reciprocation of the pinion 105. The teeth of pinion 105 are shown straight and they mesh tangentially with the external tooth formations on sleeve 106. The angle or already identified thus becomes the angle between the pinion axis and a radial plane normal to the valvestem axis.

In the arrangement of FIG. 9, the helically threaded sleeve 110 is driven by a toothed belt 111 which serves the function of the rack of the various forms discussed above. The belt 111 has tooth formations meshing with the helix of sleeve 110 throughout the full circumferential extent of helical wrap or overlay shown in the drawing. This leaves generally tangentially projecting opposite ends of the belt 111. One of these ends may be spring-tensioned with reference to a frame part and the other end may be drawn in accordance with a camderived profile, but in the form shown the belt 111 is continu ous, being laid over suitable pulleys or pinions 112-113, one or both of which may be driven in accordance with the rotary reciprocating motion necessary to achieve the desired cycle of valve actuation. In the form shown, the phantom outline shown at 114 suggests completion of the continuous belt 111 on the back side of sleeve 110 and in clearance relation therewith.

FIG. 10 illustrates a further embodiment of the invention in which twin overhead cam shafts 1l5--116 are provided with complementary cams 1171 18 for desmodromic actuation of a shuttled follower 119; cam shafts 1l5116 are synchronously driven at the same speed, as suggested by the meshed 1:! gear train G,G,G,,. Follower 119 may be a rod with circumferentially grooved rack-tooth formations 120 in mesh with the helical threads on the outside of a valve-stem actuating sleeve 121, for operating the valve 122 in accordance with principles already discussed. The virtue of the system of FIG. 10 is that not only is all valve actuation achieved by mechanisms carried by the cylinder head, but the actuation is positive in both stroke directions so that end play or mechanical hysteresis can be reduced to a minimum, thus assuring enhanced efficiency at high speeds of operation.

FIG. Ill is anenlarged sectional view to illustrate another overhead-camshaft actuating system of the invention. The

drawing illustrates application to both the intake valve I25 and the exhaust valve I26 sewing the same cylinder 127 of an engine which may be of the familiar V variety. A single overhead camshaft 126 is suitably journaled in the cylinder head and it carries, in suitably spaced pairs, an intake actuating cam I29 and an exhaust actuating cam 130. A timing belt 123 is shown connecting the camshaft 128 for 2:1 synchronized drive from the main camshaft; belt 123 may also serve a similar overhead camshaft for valves in the other bank 124 of the V arrangement of cylinders.

The follower mechanism for both cams l29130 may be generally similar, and therefore detailed discussion of the exhaust-valve-actuating follower 131 will suffice. Follower I31 is shown to be generally cylindrical and guided within an elongated bore in a boss or other formation 132 in the cylinderhead casting. Follower 131 may be cupped, with a relatively thick closure wall to serve as a cam follower proper, and with a hollowed bore toreceive and locate a preloading spring 133. A threaded plug 134 at the outer end of the guide bore for the cam follower provides frame reference for the preloading adjustment. The guide structure R32 will be understood to be locally cut away, as at a window opening designated 1135 for the case of the intake-valve-actuating structure. Through the window 135, the threaded periphery of the sleeve I36 may have meshing access to the circumferential rack-tooth formations H37 on the follower I38 which tracks cam 1129 By virtue of the similarity of actuating mechanisms for valves I25-1l26, similar access and meshing relationship will be understood to apply for the sleeve R39 and the rack-tooth formations M0.

In the arrangement of FIG. ii, the preloading spring ME for the exhaust-valve actuating structure will be seen to supply the desired resilient loading of the valve-seated position, and auxiliary sleeve 142 within the main sleeve I39 affords adjustment of this seated relationship. Similar adjustment and preloading are of course available for the intake-valve actuating mechanism, and it will be noted that access for either or both of these adjustments is very simply achieved by removing the hollow bolt structure 1453 which surrounds the spark plug M4 and which retains a shroud or closure pan I45, against sealing gaskets, over the entire assembly.

FIG. R2 is a schematic illustration of another desmodromic cam-actuating system, representing an alternative drive for the sleeve 150 of actuating mechanism for a valve ESE. In FIG. l2, a single follower rod E52 is provided at its outer end with a rack portion 153 and at its inner end with two like cam-follower rolls l53l5d mounted at diametrically opposite sides of the camshaft H55 and on opposite faces of the'follower rod I52. In the vicinity of cam-following engagement, rod I52 is cut out at 156 to define spaced elongated parallel piloting walls for guided location on the periphery of the camshaft 155; each follower rod 152 is located axially between an upstroke cam i157 and a downstroke cam I58 which are respectively in constant contact with the follower rolls I53154L Preferably, the camshaft is characterized by an elongated cylindrical bore 159 having radially ported connection, as at 160, in the regions between pairs of cams l57--ll58. Such passages provide a means of freely circulating lubricant to assure smooth desmodromic cam action. To assure ready assembly of the follower rod 152 to its camshaft, a parting line 16h suggests that rod 1152 is formed of two like abutting elongated halves, secured together by screws at suitably spaced locations 362-162' in the vicinity of cam-follower contact.

FIGS. M and 115 are very schematic illustrations of pressure-fluid operated systems for concentric valve-actuating mechanism operating an externally threaded sleeve 165 for valve 166. In FIG. M, a double-acting hydraulic or pneumatic cylinder 167 with head and tail port connections 168-169 imparts reciprocating displacement to a rack arm on actuating axis 170. The rack arm may be merely an end formation of a piston rod 171 and may be understood to be in mesh with the helix formations on sleeve 165. Cyclically reversing fluid pressures are delivered to the ports 168-169 by suitable means merely suggested by heavy dashed lines 172-ll73; such means will be understood to include actuating followers which track the respective upstroke and downstroke cams l74-175 constituting the pair required for operation of valve 166. Cams 174-175 are mounted on a camshaft 176 common to all valve-actuating cams.

In FIG. 15, the double-acting pressure-operated rack actuator of FIG. 14 will be recognized but its operation is governed by an electrical control system involving limit switches 177- I78 which track the respective profiles of cams 174-475 to determine alternating excitation of reversing solenoids l79 use. Solenoids 179-180 are supplied by source 181 to determine distribution (at valve 182) of pressurized fluid in line 169 or in line I68, as the case may be, for valve-closure and for valve-opening strokes at 166. The solenoid-operated distribution valve 382 may be of well-known commercially available construction and is therefore not shown in detail. The fluid system is shown to rely upon a supply pump E83 and a pressure-fluid return system including a sump 184. Because the fluid system of FIG. 15 has the inherent capacity to achieve very rapid valve-actuating displacements, I indicate the desirability of providing dashpot action, suggested at 185, to cushion the actuating motions. A manual adjustment at 186 provides selection of the bleed to determine dashpot action.

The description of FIGS. M and 15 as having fluid components will be understood to involve a generic use of the expression. In other words, the principles of FIG. 14 and 15 are applicable whatever the relative compressibility of the fluid involved. Thus, these systems may employ pressurized relatively incompressible liquids such as oils, or they may employ pressurized more compressible fluids such as air. Pneumatic valve operation is thus expressly contemplated by the disclosure.

It is considered important to the invention that the essence of rack-and-pinion contact, in the various forms disclosed, involves primarily point contact at any single instant of time, regardless of position in the reciprocating cycle. Point contact necessarily follows from a tangential rack-tooth engagement at the helical pinion teeth, assuming involute or nonslip profile design for the meshing teeth.

From a wear standpoint, it is a matter of relative insignificance that rack reciprocation is accompanied by axial displacement of the helically threaded sleeve (pinion), since point-contact is always at the essence of the engagement. Point contact applies for the straight-rack (as in FIG. 2) forms and for the rack-of-revolution forms (as in FIG. 5).

it will be seen that l have described improved valve-actuating mechanism inherently capable of avoiding problems of conventional mechanisms and making for engine constructions having substantially extended life expectancy and materially improved operating efficiency, particularly at high operating speeds. Specifically, my invention points the way to elimination of the valve train as a major problem of engine life and operation. Valve actuation becomes virtually frictionless, and there can be no off-axis development of valve-actuating thrusts. Servicing access and initial installation are facilitated by using the key technique (32) to position and retain a valveactuating preassembly; valve-seating preload being a matter of simple adjustment, readily accessible at the cylinder head, as

in FIG. 11 for the ends of the valve stems (at M2), or as in FIG. 5 for the end of the cam-follower rods (at 79).

My construction enables simplification of parts and the use of lighter-weight components, as compared to present systems. Lower forces are needed for valve actuation, so that friction (where it exists) necessarily involves less wear. The unitized nature of each valve actuator permits greater flexibility to the designer as to valve positioning, and the variety of alternate means to effect actuating-sleeve oscillation further enhances the flexibility of application to specific problems. Obvious advantages of increased thermal efficiency, including avoidance of hotspots, flow from the purely axial nature of all valve-actuating thrusts. From the designers viewpoint, my invention offers the considerable advantage of eliminating all angularity effects which must be accounted for in rocker-arm designs; the designer can thus rely on the completely linear relation between force transmission and displacement, from cam to valve. Valve reaction to the cam profile can be more instantaneous, there being no need for hysteresis-producing gaps or clearances in the valve train. The light weight and lower inertia of components and lesser spring forces of my invention mean substantial reduction of spring surge and other elasticity effects in the valve train; these factors are virtually completely eliminated in desmodromic versions.

Although the invention has been described in detail for the forms shown, it will be understood that modifications may be made within the scope of the invention as defined by the claims.

What 1 claim is:

1. Valve mechanism, comprising a valve body having a seat and a valve member and stem guided by said body for axial reciprocation between open and closed relation with said seat, a first sleeve member carried by said body and having a guide bore for said stem, a second sleeve member having a part in helically cammed axial overlap with said first sleeve member and with a part connected to said stem, and actuating means including reciprocating rack-and-pinion means for rotary reciprocation of said second sleeve member, whereby rack reciprocation imparts axial reciprocation to said valve member with respect to said seat.

2. Valve mechanism according to claim 1, in which the pinion of said rack-and-pinion means is carried by said second sleeve member.

3. Valve mechanism according to claim 1, in which the pinion of said rack-and-pinion means is an external formation of said second sleeve member.

4. Valve mechanism according to claim 1, in which said rack-and-pinion means is so positioned that raclr-and-pinion action takes place within the axial extent of helically cammed engagement between said sleeves.

5. Valve mechanism according to claim 1, in which said rack-and-pinion means is so positioned that the rack-andpinion reaction vector is offset from the valve-reciprocation axis and is oriented in substantially the direction of the nearest tangent to the locus of helically cammed engagement between said sleeves.

6. Valve mechanism according to claim 3, in which said valve and stem are free to rotate in the connection thereof to said second sleeve member.

7. Valve mechanism according to claim 1, in which the connection between said stem and said second sleeve member includes longitudinally adjustable means, whereby, for a given rack stroke, adjustment may be made for the degree of valve seat engagement at the valve-closed position. I

8. Valve mechanism according to claim 1, in which said helically cammed overlap includes a threaded engagement between said sleeve members.

9. Valve mechanism according to claim 1, in which said helically cammed overlap includes plural antifriction elements riding matched inner and outer helical race grooves in the region of axial overlap of said sleeve members.

10. Valve mechanism according to claim 1, in which said actuating means includes a driven rotary cam, and cam-follower means including the rack of said rack-and-pinion means.

11. Valve mechanism according to claim 10, in which said follower means includes a follower element with an adjustably securable connection to said rack, whereby adjustment at said connection provides adjustment of the degree of valve-seat engagement at the valve-closed position.

12. Valve mechanism according to claim 10, in which said body includes guide means for the nonrotatable guided longitudinal reciprocation of said rack.

13. Valve mechanism according to claim 10, in which said body includes guide means for the rotatable guided longitudinal reciprocation of said rack, the teeth of said rack being a formation of revolution about the axis of rack reciprocation.

14. Valve mechanism according to claim 13, in which said body includes means for the rotatable guided reciprocation of the element of said cam-follower means which rides said cam,

and in which the net contact region between said cam and said follower-element is offset from the guide axis for said element.

15. Valve mechanism according to claim 10, in which said cam is of the desmodromic variety.

16. Valve support and actuating mechanism for the poppet valve of an internal-combustion engine, comprising an elongated guide bushing adapted to be secured to an engine, said bushing having a bore for the rotatable longitudinally reciprocated guidance of the stem of a poppet valve, a sleeve axially overlapping part of said bushing, the overlapping portions of said sleeve and bushing having helically cammed engagement, said sleeve including connection means for the removable connection of the tail of a poppet-valve stem thereto, said sleeve having external pinion-tooth formations for actuated engagement by mating driver teeth external to the valve axis.

17. Mechanism according to claim 16, in which the said pinion-tooth formations are helically pitched in the direction opposite to the pitch of said helically cammed engagement.

1%. Mechanism according to claim 16, in which the helical lead of said pinion-tooth formations is substantially equal in magnitude but opposite in direction to that of said helically cammed engagement.

19. Mechanism according to claim 16, in which said bushing includes at one end a first elongated generally cylindrical adapter-mount portion for reception in a mounting bore of an engine frame, a radial shoulder intermediate the helically cammed and adapter-mount portions of said bushing for limiting the insertion-mounting of said bushing in the engine frame, and locating and locking means off the axis of said bushing and serving to retain the axial and angular position of the bushing when inserted in the engine frame.

20. Mechanism according to claim 16, in which the helical lead of said pinion-tooth formations exceeds the magnitude and is opposite in direction to that of said helically cammed engagement.

21. Mechanism according to claim 20, in which the helical lead of said pinion-tooth formations is in the range of substantially 35 to 45.

22. Mechanism according to claim 20, in which the helical lead of said pinion-tooth formations is substantially 41 to 42.

23. Mechanism according to claim 20, in which the helical lead of said cammed engagement is in the range of substantially 25 to 35.

24. Mechanism according to claim 20, in which the helical lead of said cammed engagement is substantially 29.

25. in combination, an internal-combustion engine including a cam shaft and having a cylinder and inlet and exhaust ports communicating with said cylinder, inlet and exhaust poppet valves having guided support in said engine for opening and closing said ports, and valve-actuating mechanism driven by said cam shaft for actuating said valves and for the random angular indexing of said valves with each actuating cycle thereof; said mechanism comprising, for each valve, reciprocating cam-follower means tracking a part of said cam shaft and a connection from said cam-follower means to its valve, said connection including two overlapping sleeves in helically cammed engagement, one of said sleeves being referenced to the engine frame and the other of said sleeves including means independent of said helically cammed engagement and responding to cam-follower reciprocation to rotationally reciprocate said other sleeve, the valve stem being freely rotatably connected to said other sleeve.

26. In combination, an internal-combustion engine including a cam shaft and having a cylinder and inlet and exhaust ports communicating with said cylinder, inlet and exhaust poppet valves having guided support in said engine for opening and closing said ports, and valve-actuating mechanism driven by said cam shaft for actuating said valves and for the random angular indexing of said valves with each actuating cycle thereof; said mechanism comprising, for each valve, reciprocating carnefollower means tracking a part of said cam shaft and a connection from said camfollower means to its valve, said connection including means referenced to the engine frame and responding to cam-follower reciprocation to impart to its valve a reciprocating cycle that is both angular and axial; said connection including a helical-track ball bearing on the axis of valve actuation, said bearing comprising inner and outer elements having matched helical ball races in their overlapping adjacent surfaces, balls in said races, one of said elements being fixed to the engine frame, the other of said elements having a rotary-reciprocating driven connection to said cam-follower means, the valve-stem connection being made to said other element, with the valve freely rotatable.

27. The combination of claim 26, in which said ball bearing includes retainer means retaining adjacent balls in spaced relation in the ball complement of each race.

23. The combination of claim 27, in which a single retainer serves balls of all races.

29. in combination, an internal-combustion engine including a cam shaft and having a cylinder and inlet and exhaust ports communicating with said cylinder, inlet and exhaust poppet valves having guided support in said engine for opening and closing said ports, and valve-actuating mechanism driven by said cam shaft for actuating said valves and for the random angular indexing of said valves with each actuating cycle thereof; said mechanism comprising, for each valve, reciprocating cam-follower means tracking a part of said cam shaft and a connection from said cam-follower means to its valve, said connection including means referenced to the engine frame and responding to cam-follower reciprocation to impart to its valve a reciprocating cycle that is both angular and axial; said connection including matched inner and outer helically splined elements with the helix axis on the axis of valve actuation, one of said elements being fixed to the engine frame, the other of said elements having a rotary-reciprocating driven connection to said cam-follower means, the valvestem connection being made to said other element, with the valve freely rotatable.

30. in combination, an internal-combustion engine including a cam shaft and having a cylinder and inlet and exhaust ports communicating with said cylinder, inlet and exhaust poppet valves having guided support in said engine for opening and closing said ports, and valve-actuating mechanism driven by said cam shaft, said valve-actuating mechanism including cam-follower means for each valve and tracking a part of said cam shaft, preloaded spring means independent of the valve closing forces and acting between the engine frame and said cam-follower means for assuring earn-tracking, and means including a helically cammed sleeve referenced to the engine frame and connected to its valve, said sleeve having a rotary reciprocating driven connection to said cam-follower means.

31. The combination of claim 30 in which the direction of preload of said spring means biases said cam-follower means in the valve-opening direction.

32. in combination, an internal-combustion engine comprising spaced parallel cam shafts in synchronized relation, complementary desmodromic cams on said cam shafts, a reciprocating follower tracking a pair of complementary cams on said cam shafts, a valve having an elongated stem, valvestem guide means, a rotatable sleeve connected to said valve stem and in helically cammed engagement with said valvestem guide means on an axis concentric with the axis of valvestem guidance, and means connecting said sleeve to said follower to impart to said sleeve cyclical oscillations about the sleeve axis in accordance with reciprocations of said follower.

33. in combination, an internal-combustion engine comprising a cam shaft having a pair of desmodromic cams, a reciprocating follower tracking both said cams, a valve having an elongated stem, valve-stem guide means, a rotatable sleeve connected to said valve stem and in helically cammed engagement with said valve-stem guide means on an axis concentric with the axis of valve-stem guidance, and means connecting said sleeve to said follower to impart to said sleeve cyclical oscillations about the sleeve axis in accordance with reciprocations of said follower.

3%. As an article of manufacture, a unitary valve-stem guide and longitudinal actuator, comprising an elongated guide member having at one end means for secure removable attachment to an engine frame and including at the other end a generally cylindrical projection, elongated valve-stem guide means extending through said member in concentric relation with said projection, and a sleeve carried concentrically about said projection and having a helically cammed rotary and longitudinal displacement relation to said projection.

35. The article of claim 34, in which said sleeve has external helical threads of helix-advance direction opposed to that of said cammed relation.

36. The article of claim 34, in which the end of said sleeve projects axially beyond said projection and includes means for the selective attachment of a valve stem.

37. The article of claim 36, in which said sleeve comprises a first sleeve part in helically cammed relation to said projection and a second sleeve part in threaded longitudinally adjustable relation to said first sleeve part and at the axially projecting end thereof, said selective attachment means being on said second sleeve part.

38. The article of claim 34, in which plural splines establish the said helically cammed engagement.

39. The article of claim 34, in which plural balls in plural corresponding helical races in said projection and within said sleeve establish the said helically cammed engagement.

40. in combination, an internal-combustion engine including a cylinder head and comprising a cam shaft with a pair of cams and joumaled for rotation in said head, intake and exhaust port and valve structure in said head on opposite sides of said cam shaft, an intake-valve actuator including a rotary sleeve connected to its valve on a valve-actuating axis, an exhaust-valve actuator including a rotary sleeve connected to its valve on a valve-actuating axis, said axes being inclined toward each other on opposite sides of said cam shaft, each sleeve being externally helically threaded, and rack followers meshing with said respective sleeve threads and tracking said cams in opposite directions but substantially in a plane common to the axis of cam shaft rotation.

41. Valve mechanism, comprising a valve body having a seat and a valve member and stem guided by said body for axial reciprocation between open and closed relation with said seat, a first sleeve member carried by said body and having a guide bore for said stem, a second sleeve member having a part in helically cammed axial overlap with said first sleeve member and having a part connected to said stem, and actuating means including reciprocating driving means connected for rotary reciprocation of said second sleeve, whereby rotary reciprocation imparted to said second sleeve member imparts axial reciprocation to said valve member with respect to said seat.

42. Valve mechanism according to claim 41, in which said actuating means includes a cam-and-follower mechanism determining the reciprocation imparted to said second sleeve member.

43. Valve mechanism according to claim 42, in which said actuating means includes fluid-pressure operated means between said cam-and-follower mechanism and said second sleeve member.

44. Valve mechanism according to claim 41, in which said actuating means includes fluid-pressure operated means determining the reciprocation imparted to said second sleeve member, and recycling program means including pressurefluid reversing valve means in controlling relation with said fluid-pressure operated means.

45. Valve mechanism according to claim 42, in which said actuating means includes a belt in positive direct-driving relation with said second sleeve member.

46. Valve mechanism according to claim 42, in which said second sleeve member has a toothed periphery, and in which said actuating means includes means having a reciprocating geared engagement to said toothed periphery.

47. Valve mechanism according to claim 46, in which said last-defined means includes a pinion gear.

48. Valve mechanism according to claim 46, in which said last-defined means includes a sector gear and in which an arm effectively integral with said gear is part of said cam-and-follower means.

49. Valve mechanism comprising a body element having an elongated guide bore, a valve element including a stem supported in said bore and slidably guided thereby for longitudinal and rotary motion, and valve-actuating mechanism referenced to said element and including a linear-reciprocating to rotary-reciprocating coupling wherein a rotaryreciprocating output element is guided for rotary-reciprocation on and axial reciprocation along the axis of said guide bore, said mechanism including a linear-reciprocating input element reciprocable on an axis angularly offset from the guide-bore axis, said angular offset being in the range intermediate a direction parallel to and a direction normal to the guide-bore whereby thrusts imparted to said output element and occasioned by reciprocation of said input element are necessarily characterized by a combination of axial and rotary-reciprocating thrust components, and an axially retaining interconnection between said output element and said valve stem.

50. The mechanism according to claim 49, in which said interconnection is characterized by freedom for relative rotation of said valve element and of said output element.

51. The mechanism according to claim 49, in which said valve-actuating mechanism includes between said input and output elements an interconnection member freely rotatable on the linear-reciprocation axis of said input member.

Claims

4. Valve mechanism according to claim 1, in which said rack-and-pinion means is so positioned that rack-and-pinion action takes place within the axial extent of helically cammed engagement between said sleeves.

5. Valve mechanism according to claim 1, in which said rack-and-pinion means is so positioned that the rack-and-pinion reaction vector is offset from the valve-reciprocation axis and is oriented in substantially the direction of the nearest tangent to the locus of helically cammed engagement between said sleeves.

6. Valve mechanism according to claim 1, in which said valve and stem are free to rotate in the connection thereof to said second sleeve member.

7. Valve mechanism according to claim 1, in which the connection between said stem and said second sleeve member includes longitudinally adjustable means, whereby, for a given rack stroke, adjustment may be made for the degree of valve-seat engagement at the valve-closed position.

14. Valve mechanism according to claim 13, in which said body includes means for the rotatable guided reciprocation of the element of said cam-follower means which rides said cam, and in which the net contact region between said cam and said follower-element is offset from the guide axis for said element.

18. Mechanism according to claim 16, in which the helical lead of said pinion-tooth formations is substantially equal in magnitude but opposite in direction to that of said helically cammed engagement.

21. Mechanism according to claim 20, in which the helical lead of said pinion-tooth formations is in the range of substantially 35* to 45*.

22. Mechanism according to claim 20, in which the helical lead of said pinion-tooth formations is substantially 41* to 42*.

23. Mechanism according to claim 20, in which the helical lead of said cammed engagement is in the range of substantially 25* to 35*.

24. Mechanism according to claim 20, in which the helical lead of said cammed engagement is substantially 29*.

26. In combination, an internal-combustion engine including a cam shaft and having a cylinder and inlet and exhaust ports communicating with said cylinder, inlet and exhaust poppet valves having guided support in said engine for opening and closing said ports, and valve-actuating mechanism driven by said cam shaft for actuating said valves and for the random angular indexing of said valves with each actuating cycle thereof; said mechanism comprising, for each valve, reciprocating cam-follower means tracking a part of said cam shaft and a connection from said cam-follower means to its valve, said connection including means referenced to the engine frame and responding to cam-follower reciprocation to impart to its valve a reciprocating cycle that is both angular and axial; said connection including a helical-track ball bearing on the axis of valve actuation, said bearing comprising inner and outer elements having matched helical ball races in their overlapping adjacent surfaces, balls in said races, one of said elements being fixed to the engine frame, the other of said elements having a rotary-reciproCating driven connection to said cam-follower means, the valve-stem connection being made to said other element, with the valve freely rotatable.

28. The combination of claim 27, in which a single retainer serves balls of all races.

29. In combination, an internal-combustion engine including a cam shaft and having a cylinder and inlet and exhaust ports communicating with said cylinder, inlet and exhaust poppet valves having guided support in said engine for opening and closing said ports, and valve-actuating mechanism driven by said cam shaft for actuating said valves and for the random angular indexing of said valves with each actuating cycle thereof; said mechanism comprising, for each valve, reciprocating cam-follower means tracking a part of said cam shaft and a connection from said cam-follower means to its valve, said connection including means referenced to the engine frame and responding to cam-follower reciprocation to impart to its valve a reciprocating cycle that is both angular and axial; said connection including matched inner and outer helically splined elements with the helix axis on the axis of valve actuation, one of said elements being fixed to the engine frame, the other of said elements having a rotary-reciprocating driven connection to said cam-follower means, the valve-stem connection being made to said other element, with the valve freely rotatable.

30. In combination, an internal-combustion engine including a cam shaft and having a cylinder and inlet and exhaust ports communicating with said cylinder, inlet and exhaust poppet valves having guided support in said engine for opening and closing said ports, and valve-actuating mechanism driven by said cam shaft, said valve-actuating mechanism including cam-follower means for each valve and tracking a part of said cam shaft, preloaded spring means independent of the valve closing forces and acting between the engine frame and said cam-follower means for assuring cam-tracking, and means including a helically cammed sleeve referenced to the engine frame and connected to its valve, said sleeve having a rotary reciprocating driven connection to said cam-follower means.

32. In combination, an internal-combustion engine comprising spaced parallel cam shafts in synchronized relation, complementary desmodromic cams on said cam shafts, a reciprocating follower tracking a pair of complementary cams on said cam shafts, a valve having an elongated stem, valve-stem guide means, a rotatable sleeve connected to said valve stem and in helically cammed engagement with said valve-stem guide means on an axis concentric with the axis of valve-stem guidance, and means connecting said sleeve to said follower to impart to said sleeve cyclical oscillations about the sleeve axis in accordance with reciprocations of said follower.

34. As an article of manufacture, a unitary valve-stem guide and longitudinal actuator, comprising an elongated guide member having at one end means for secure removable attachment to an engine frame and including at the other end a generally cylindrical projection, elongated valve-stem guide means extending through said member in concentric relation with said projection, and a sleeve carried concentrically about said projection and having a helically cammed rotary and longitudinal displacement relation to said projection.

40. In combination, an internal-combustion engine including a cylinder head and comprising a cam shaft with a pair of cams and journaled for rotation in said head, intake and exhaust port and valve structure in said head on opposite sides of said cam shaft, an intake-valve actuator including a rotary sleeve connected to its valve on a valve-actuating axis, an exhaust-valve actuator including a rotary sleeve connected to its valve on a valve-actuating axis, said axes being inclined toward each other on opposite sides of said cam shaft, each sleeve being externally helically threaded, and rack followers meshing with said respective sleeve threads and tracking said cams in opposite directions but substantially in a plane common to the axis of cam shaft rotation.

44. Valve mechanism according to claim 41, in which said actuating means includes fluid-pressure operated means determining the reciprocation imparted to said second sleeve member, and recycling program means including pressure-fluid reversing valve means in controlling relation with said fluid-pressure operated means.

49. Valve mechanism comprisinG a body element having an elongated guide bore, a valve element including a stem supported in said bore and slidably guided thereby for longitudinal and rotary motion, and valve-actuating mechanism referenced to said element and including a linear-reciprocating to rotary-reciprocating coupling wherein a rotary-reciprocating output element is guided for rotary-reciprocation on and axial reciprocation along the axis of said guide bore, said mechanism including a linear-reciprocating input element reciprocable on an axis angularly offset from the guide-bore axis, said angular offset being in the range intermediate a direction parallel to and a direction normal to the guide-bore whereby thrusts imparted to said output element and occasioned by reciprocation of said input element are necessarily characterized by a combination of axial and rotary-reciprocating thrust components, and an axially retaining interconnection between said output element and said valve stem.