US2426438A - Engine cylinder construction - Google Patents

Description

Aug. 1947- c. 0. DE PEW 2,426,438

ENGINE CYLI NDER CONSTRUCTION Filed March 1, 1944 2' Sheets-Sheet 1 &

IN VEN TOR;

I BY W A 032x25 x2 c. c. DE FEW ENGINE CYLINDER CONSTRUCTION Aug. 26, 1947.

2 Sheets-Sheet 2 Filed March 1, 1944 Patented Aug. 26, 1947 ENGINE CYLINDER CONSTRUCTION Chester 0. DePew, Farmingdale, N, Y., assignor to Fairchild Engine and Airplane Corporation, Farmingdale, N. Y., a corporation of Maryland Application March 1, 1944, Serial No. 524,645 a 2 Claims. (Cl. 123-90) This invention relates to engine cylinder construction and has particular reference to cam mechanism mounting arrangement for the overhead valve type of aeronautical engines, although the inventionis not limited to aeronautical use.

The cooling efficiency of air-cooled aeronautical engines depends largely upon the number and area of heat radiating fins that can be provided at the hottest points in, order to rapidly dissipate the heat of the engine, and this condition is more acute at the cylinder head, not only because that is the hottest part of the cylinder, but also because the necessary values and their'operating mechanism located on the head materially limits the available cooling fin space on the cylinder head. This mechanismin the case of the common poppet type of valve includes the cam shaft, rocker arms and their shafts and the usual flanges or bosses formed on the cylinder head for mounting the mechanism thereto, and these mounting flanges or bosses necessarily occupy pace that would otherwise be available for cooling purposes. Accordingly, an arrangement which reduces or eliminates such space-occupying appurtenances on the-cylinder head, such as cam 'box mounting flanges or bosses and the like, permits additional cooling fins on the cylinder head and thus materially augments the cooling efficiency of the engine. At the same time, the weight of the cylinder may be reduced.

In accordance with thepresent invention, a cam mechanism mounting arrangement is provided for internal combustion engines, which eliminates the usual mounting flanges orbosses and thus makes available relatively large spaces and areas on the cylinder head in which addi- (tional cooling fins may bemounted, thus not only proportionately improving the cooling characteristics of the cylinder head but also reducing the weight of the engine, since the metal required for the flanges or bosses is not used and stresstransmitting rods or traps are not required. Also, the cam box itself may be made materially lighter because the usual cooperating flanges or bosses, bolts or other rigid fastening means are not required thereon, and consequently the stresses developed by differential thermal expansion of dissimilar metals need not be compensated. Additional advantages are simplification of assembly and disassembly, reduced cost of manufacture, and saving of metal.

Th invention utilizes the pressure of the poppet valve springs to secure the cam box and its mechanism fixedly but not rigidly to the row of cylinders on the head of the engine. In the preferred embodiment of the invention, the cam box, preferably made of sheet metal and assembled as a complete unit to contain the usual cam shaft, its bearings, the rocker arms and their shafts, is formed with a sheet or plate bottom shaped to conform to the contour of the cylinder head and adapted to be clamped between the cylinder head surface and one end of the corresponding intake and exhaust valve springs, the other ends of which engage the spring keeper discs on the ends or tips of the valve stems in the usual way. The normal considerable pressure of the valve springs accordingly holds the cam box securely on the cylinder head, and inasmuch as the forces acting within the cam box are equalized,-i. e., the action of the cam tending to lift the cam box away from the cylinder head is equalized by the valve springs, the cam box is not under unusual stress notwithstanding that it is not rigidly secured to the cylinder head. Furthermore, the cam box may expand and contract thermally relatively to the head without creating stresses in itself or imparting them to the cylinder head, and vice versa, since th connection between them is non-rigid and hence permits relative movement due to such thermal expansion and contraction. In view of the reduction of stresses the cam box may be made as light as desirable, consistent with the normal loads to which any cam box is'sub jected in use.

Owing to the elimination of rigid fastening arrangements between the cam box and the cylinder heads, including the mounting flanges or bosses that are usually cast integrally with the outer'surface of the cylinder, the considerable space occupied thereby is released and made available for cooling purposes, so that the number and area of the cooling fins may be greatly increased at the head of the cylinder where cooling is needed and difficult to obtain because of the interference with free air circulationprovided by the valves and parts. Other advantages will be apparent as the description proceeds.

For a more complete understanding of the invention, reference may be had to the accompanying drawings, in which:

Figure 1 is a. vertical section through the valves of a cylinder head of an aeronautical engine constructed in accordance with this invention and illustrating the augmented cooling fin space that is available across the cylinder head;

Fig. 2 is plan view of the cam box, with the cam shaft, rocker shaft, rocker arms, bearing blocks and valves omitted to show the interior arrangement of the cam box; and,

Fig. 3 is a side view of the same.

Referring to the drawings, numeral Hi designates the head end of a cylinder of a multicylinder, air-cooled, inline aeronautical engine, preferably of the inverted type. The cylinder lil comprises the barrel I and the head I2, the latter being provided with the usual exhaust valve |3 leading to the exhaust port I 4, and the intake valve l5 leading from intake port l6. Stems I1 and I8 of exhaust and intake valves l3 and I5, respectively, slide axially in the respective stationary valve guides I9 and 20 suitably secured to the cylinder head |2, as by being imbedded in the cylinder head casing material 52, 53, so as to form a rigid component thereof. Exhaust valve guide I9 is provided at its outer end with the integral flange 2| and intake valve guide 20 is similarly provided with the integral flange 22.

Resting on flanges 2| and 22 is the cam box generally designated 23, preferably formed of sheet metal such as an aluminum alloy or steel, pressed or stamped to shape and comprising the rectangular box 24, having an opening at the top for access to the valves and their operating mechanism, and the cover 25, held in position by suitable removable fastening means such as the cap screws 25. Obviously, either the box 24 or the cover 25, or both, may be cast metal, as desired.

As shown particularly in Fig. 2, the bottom 23 of box 24 is preferably formed of a continuous sheet or plate shaped to conform to the contour of the cylinder head as shown particularly in Fig. 1. In order to thus conform, the bottom 26 is shaped or otherwise provided at spaced interval with pressed bosses 2'! which fit into the recessed slanting portions of the cylinder head at the valves l3 and I5. The lower surface 28 of each boss 21 is flat so as to overlie the corresponding flanges 2| and 22 and is provided with an enlarged opening 29 which loosely receives the projecting extensions IE or 20' of the valve guides H] or 26] at each side. The base. 28 of each boss 27 accordingly rests flatwise on the upper surface of the corresponding flange 2| or 22, which in turn is supported on and by the corresponding cylinder head casing material 52 or 53, as shown in Fig. 1.

In assembling, a valve spring centering washer 39 is placed around the projecting upper end IQ of the exhaust valve guide l9 so that it rests on the inner surface of the base 28 of the boss 27 at the exhaust side of the cam box. A similar valve spring centering washer 3| overlies the inner surface 28 of the corresponding cam box boss 21 after it is place dover the intake valve guide extension 20' on the other side of the engine.

Interposed between the valve centering washer 31] at the exhaust side of the engine and the spring keeper disc 32 on the free end or tip of exhaust valve stem H, are the valve springs 33 which may be two in number, as shown, or more or less. A similar valve spring keeper disc 34 and spring combination 35 are used at the other or intake side of the engine, as shown in Fig. 1.

It will be observed that the valve springs 33, being under compression between keeper disc 32 and spring centering washer 30 at the exhaust side of the engine, force washer 30 against the base 28 of the cam box boss 21 so as to clamp and thus securely hold cam box 24 against the flange 2| on the cylinder head l2. Similarly, intake valve springs 35 clamp the base 28 of the opposite cam box boss 21 between valve centering Washer 3| and flange 22 on the opposite side of the engine. Inasmuch as the cam box 24 is inte gral with, or is formed as a unit with, the bosses 21, the entire cam box 23 is thus held securely but non-rigidily in position against the surfaces of flanges 2| and 22 on the cylinder head |2 by the corresponding valve springs 33 and 35.

Being so held on the cylinder head, the cam box 23 also wholly contains and supports the cam shaft, its bearings, the rocker shafts, their bearings, and the rocker arms. To that end the bottom 26 of the cam box 23 is provided at spaced intervals with lugs 36, two for each set of intake and exhaust rocker shaft supports as shown particularly in Fig. 2. These lugs 35 may be welded or otherwise secured to the interior of the cam box bottom 26, and are provided with counterbored holes 31, accessible through the bottom 25 of the cam box 24 and adapted to receive the stud bolts 38, or the like, whereby the pillow blocks 33 or lower portions of the cam shaft bearings are ecuredto the cam box.

The cap blocks or upper halves 40 of the cam shaft bearings are suitably secured to the pillow blocks 39 by extensions 4| on bolts 38, which are provided with shoulders 42 seated in counterbores in upper bearing or cap blocks 40 and held in place by nuts 43. The cam shaft 44 is accordingly journaled in the bearings formed by blocks 39, 40 and upper bearing or cap block 40 also carries the exhaust and intake valve rocker shafts 45 and 46, respectively. Exhaust valve rocker arms 41 and intake valve rocker arms 48 are journalled on respective rocker shafts 45 and 46 and their rollers 49 engage the corresponding cam lobes 50 of cam-shaft 44 while their opposite ends engage the tips of the corresponding valve stems H and I8 in the usual way.

Operation and assembly of the cam box of this invention will be readily understood from the foregoing description, it being evident that the entire cam box 23 with the valve operating mechanism carried and supported thereby and therein, is held securely but non-rigidly in position on the cylinder head |2 by reason of the cam box fbosses 21 being clamped against the flanges 2| and 22 of valve stem guides l9 and 20, respectively, by corresponding valve springs 33 and 35, without any other fastening means being required,

The elimination of the usual fastening means, such as bolts or studs, with the corresponding bosses or flanges on the cylinder heads, makes available for cooling purposes the entire space 5| between the casings 52 and 53 of the port I4 and I6 and valve stem guides l9 and 20, those casings preferably being formed of aluminum or other good heat-conducting material. The availability of this large space 5| for cooling purposes not only enables the circulation of greater volumes of air between the ports l4 and I6 than heretofore, but also enables a considerable increase in number and area of cooling fins within the space.

Inasmuch as the space between the valves is one of the hottest parts of the engine, the additional cooling facility provided by this invention permits the heat to be dissipated more rapidly and thus affords more eflicient cooling of the cylinder head. Also, particularly in inline aircooled engines, the normal flow ofv air being at right angles to the crankshaft and in the common plane of the exhaust and intake valves, it is in tercepted by the ports l4 and I6 and the corresponding valves I9 and 20, so that the air must be diverted to flow through the space'5|, which is normally difficult to accomplish effectively because of limited space. Accordingly, any increase in the number and area of the fins 54 within the space I, such as is provided by the present invention, also greatly simplifies and augments the c00ling of that area between the valve ports which is ordinarily difficult to cool.

It will be observed that inasmuch as the connection between the cam box 23 and the cylinder head 12 is one of abutting and frictional contact without involving positive fastening means, the connection is non-rigid, although secure. The non-rigidity, however, has the advantage of affording relative movement between the cam box and the cylinder head due to differential thermal expansion and contraction, such movement being permitted by the oversize holes 29, so that no strains are transmitted from one to the other, nor need this differential expansion be compensated for or especially accommodated.

Although the invention has been described in connection with an air-cooled inline type of engine, for aeronautical engines, the invention is not limited to such use and is applicable to any engine having the poppet type of valve, whose valve springs may be utilized to secure the cam box to the cylinder in accordance with this invention, and furthermore, the invention is not limited to the details of construction illustrated and described herein but is susceptible of changes in form and detail within the scope of the appended claims.

I claim:

1. In n internal combustion engine having valve stems projecting from its cylinder heads and spring means for closing said valves mounted on said valve stems and having their outer ends engaging spring retainers at the outer ends of said valve stems; the combination of a sheet metal box having sides, ends, bottom and top, said bottom being adapted to engage said cylinder heads and having spaced-apart pairs of openings for receiving said valve stems, reinforcing elements secured to the bottom of, and within said box and extending between and terminating closely adjacent to said pairs of openings, cam shaft bearings and rocker arm supports mounted on and supported solely by said reinforcing elements, said box being retained in engagement with said cylinder head solely by engagement of the inner ends of said spring means with the bottom of said box adjacent to said openings.

2. In an internal combustion engine having valve stems projecting from its cylinder heads and spring means for closing said valves mounted on said valve stems and having their outer ends engaging spring retainers on the outer ends of said valve stems; the combination of a sheet metal box having sides, ends, bottom and a detachable transversely-curved top secured at its edges to the sides and ends of said box by detachable fastening means, said bottom being adapted to engage said cylinder heads and having spaced-apart pairs of openings for receiving said valve stems, reinforcing elements secured to the bottom of, and within said box and extending between and terminating closely adjacent to said pairs of openings, cam shaft bearings and rocker arm supports mounted on and supported solely by said reinforcing elements, said box being retained in engagement with said cylinder head solely by engagement of the inner ends of said spring means with the bottom of said box adjacent to said openings.

CHESTER C. DEPEW.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,721,341 Halford July 16, 1929 1,741,678 Brewer Dec. 31, 1929 1,866,281 Woolson July 5, 1932 2,024,334 Caminez Dec. 17, 1935 1,332,294 Holmes Mar. 2, 1920 1,415,167 Fuchs May 9, 1922 1,848,008 Griffith 'Mar. 1, 1932 FOREIGN PATENTS Number Country Date 170,436 Great Britain 1921 463,493 Germany July 30, 1928

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