US3659568A - Cylinders for air-cooled reciprocable piston internal combustion engines - Google Patents

Abstract

In an air-cooled reciprocable piston engine having at least two adjacent cylinders with parallel longitudinal axes and transverse fins, in which adjacent fin portions of two adjacent cylinders are provided with straight substantially parallel edges defining therebetween a narrow gap while the ends of said straight edges merge by curved portions curved in the direction toward the axis of the pertaining cylinder with the segment-shaped remainder of the pertaining fins, tie rod means being located between adjacent curved portions of respectively pertaining fins of two adjacent cylinders.

Description

United States Patent Howe 451 May 2,1972

[54] CYLINDERS FOR AlR-COOLED RECIPROCABLE PISTON INTERNAL COMBUSTION ENGINES [72] Inventor: Hans-Ulrich Howe,

forst, Germany Klockner-I-IumboIdt-Deutz Aktiengesellschaft, Cologne-Deutz, Germany Dec. 8, 1970 Bensberg-Franken- [73] Assignee:

22 Filed:

v [21] App]. No.: 96,212

[30] Foreign Application Priority Data Dec. 10, 1969 Germany ..P 19 61 803.2

[52] U.S. Cl. ..l23/41.69, 123/59 R, 123/193 CH, 123/ 195 [51] Int. Cl. ..F02f l/06, F02f 1/30 [58] Field of Search ..123/41.69, 193 C, 193 CH, 195 R, 123/59 R, 59 A, 59 B [5 6] References Cited UNITED STATES PATENTS hm MW 2,608,962 9/1952 Kloss et al ..l23/4l.69

YIIIIIIIIIIIIIIIIIII 'I/I/IIIIIIII/IIIIIIIII 2,883,997 4/1959 Langmaier ..l23/193 C FOREIGN PATENTS OR APPLICATIONS 899,161 5/1945 France 123/41 .69

829,703 7/1938 France ..123/41.69

942,058 4/1956 Germany ..123/41.69

871,917 7/1961 Great Britain 123/41 .69

Primary Examiner-Al Lawrence Smith Attorney-Walter Becker ABSTRACT In an air-cooled reciprocable piston engine having at least two adjacent cylinders with parallel longitudinal axes and transverse t'ms, in which adjacent fin portions of two adjacent cylinders are provided with straight substantially parallel edges defining therebetween a narrow gap while the ends of said straight edges merge by curved portions curved in the direction toward the axis of the pertaining cylinder with the segment-shaped remainder of the pertaining fins, tie rod means being located between adjacent curved portions of respectively pertaining fins of two adjacent cylinders.

3 Claims, 3 Drawing Figures Patented May 2, 1972 2 Sheets-Shut 1 FIG] Patented May 2, 1972 2 Sheets-Sheet 2 FIG. 1a

CYLINDERS FOR AIR-COOLED RECIPROCABLE PISTON INTERNAL COMBUSTION ENGINES The present invention relates to an air-cooled multicylinder reciprocable piston engine with cylinders arranged in series and equipped with transverse fins.

With air-cooled reciprocable piston cylinders equipped with transverse fins, it is customary in order to assure a sufficient cooling, to design the cooling ribs of the cylinder, especially adjacent the cylinder head, as high as possible. The preferred circular shape of the fin contour is, in order to obtain a compact construction, somewhat flattened with serially arranged cylinders and, more specifically, in the region where two adjacent cylinders are closest to each other. This means a reduction in the height of the fins in the said region. A further interruption of the circular shape of the fin contour is caused by cutouts or recesses for the passage of the cylinder head connecting screws. These screws have to be arranged as close as possible to the cylinder wall in order to reduce the bending moment in the bottom of the cylinder head between the cylinder head sealing surface and the point of attack of the connecting screws.

The above mentioned various interruptions of the radial circumferential contour of the fins affects the strength of the cylinder and frequently result in deformations, especially bends within the region of the recesses. As a result thereof, a non-uniform support (Tragbild) of the piston is obtained. Therefore, it is the tendency to maintain these deformations in possibly narrow limits by special designs of the cylinders.

According to German Pat. No. 964,820 it is known to counteract the deformation of the cylinder caused by recesses in the fins within the region of the tie rods, by providing slots extending parallel to the cylinder axis between the recesses for the tie rods and in this way to modify the deformations into a possibly uniform polygon so that a more even supporting structure of the piston will be obtained.

It has also been suggested in the thermally and mechanically highly stressed end of the cylinder adjacent the cylinder head not to interrupt the fins and to provide bores in the ribs for passing the connecting screws therethrough. Inasmuch as these bores are difficult to cast, it is preferred to produce said bores mechanically, i.e., by drilling. Such drilling, however, has the drawback that the drill when cutting through each individual rib has to cut twice through the hard outer cast skin with the white solidified marginal zone. This is very hard on the drill and therefore considerably reduces the life of the drill. For this reason, only the upper third, or one-half of the fins is drilled, whereas the lower two-thirds or one-half of the fins have their recesses cast into the fins.

It has furthermore been suggested to keep the deformation of the cylinder within small limits by making the walls of the cylinder of different thickness, and more specifically by dimensioning those walls thicker which contain the recesses for the passage of the screws, while those wall areas of the cylinder which are located between two screws are thinner than the first mentioned walls.

It is, therefore, an object of the present invention, so to design the fin equipped cylinder that deformations of the cylinder within the recesses provided in the fins will practically be avoided.

This object and other objects and advantages of the invention will appear more clearly from the following specification, in connection with the accompanying drawing, in which:

FIG. 1 diagrammatically illustrates a view of a cylinder pertaining to a reciprocable piston engine.

FIG. 1a is a section along along the line lala of FIG. 2.

FIG. 2 is a top view of the cylinder shown in FIG. 1 while illustrating in dot-dash lines the contour of an adjacent cylinder.

An air-cooled multi-cylinder reciprocable piston engine with cylinders arranged in series and equipped with fins is, according to the present invention, characterized in that each two adjacent cylinders including the pertaining cylinder heads are, by means of a tie rod common thereto and located between said cylinders or by means of a plurality of tie rods,

connected to the crank housing, and is furthermore characterized in that the cooling fins, especially those of the working cylinders have within the region of the tie rod or tie rods approximately semicircular recesses of only slight depth, the line of confinement of which extends continually.

In view of this design, the original fin contour is practically retained so that no' material deformation of the cylinder will occur as a result of the forces exerted by the connecting screw, and furthermore a uniform cooling will be assured.

In view of the location of the tie rods at the end of the separating gap between two adjacent cylinders,'not only will the recess in the fins and thereby the local weakening of the cylinder be only slight, but it will also be assured in an advantageous manner that the cooling air flow is devided and deviated to the cylinder walls. It is a well known fact that otherwise, in view of the separating gap between two adjacent cylinders, a portion of the cooling air is lost without doing any useful work.

According to a further feature of the invention, the recess in said ribsor fins in the region of the tie rods are precast so that a very economical manufacture will be obtained.

Referring now to the drawing in detail, FIG. 1 shows a cylinder 1 with transverse fins, comprising the fin-equipped section 2 and the lower shank portion 3 which is free from fins. FIG. 2 shows the circular sealing surface 4 of cylinder 1 for engagement with a corresponding sealing surface of the cylinder head. The circular shape of the fin contour 5 shows flat portions 6 at two sections located opposite to each other, in order to reduce the distance between two adjacent working cylinders and to thereby obtain a compact structure. Recesses 8 defined by a flat are having a radius r are provided in the fin contour for the tie rods 7. These recesses 8 gradually merge through rounded portions 9 with the contour 5 of the fins.

It is, of course, to be understood that the present invention is, by no means, limited to the particular showing in the drawing, but also comprises any modifications within the scope of the appended claims.

What I claim is:

1. In an aircooled reciprocable piston engine with crank case: two cylinders having their longitudinal axes arranged parallel to each other and respectively being provided with transverse fins extending around the respective cylinder, those parts of at least some of said fins which respectively pertain to said two cylinders and are located adjacent to and opposite each other having substantially straight edge portions extending at a substantially right angle with regard to the plane passing through the said parallel axes of said two cylinders, said straight edge portions defining with each other a relatively narrow gap, each end of each straight edge portion of each fin merging with a relatively large rounded portion of the same fin through a relatively short curved portion curved inwardly toward the interior of the pertaining cylinder, and tie rod means common to and arranged between two adjacent ones of said inwardly curved portions for tieing said cylinders to their cylinder heads and the crank case pertaining thereto.

2. An arrangement according to claim 1, in which said relatively short curved portions within the region of said tie rod means are pre-cast.

3. An arrangement according to claim 1, in which the depth of said relatively short curved portion is rather slight with regard to its width.

Claims (3)

1. In an air-cooled reciprocable piston engine with crank case: two cylinders having their longitudinal axes arranged parallel to each other and respectively being provided with transverse fins extending around the respective cylinder, those parts of at least somE of said fins which respectively pertain to said two cylinders and are located adjacent to and opposite each other having substantially straight edge portions extending at a substantially right angle with regard to the plane passing through the said parallel axes of said two cylinders, said straight edge portions defining with each other a relatively narrow gap, each end of each straight edge portion of each fin merging with a relatively large rounded portion of the same fin through a relatively short curved portion curved inwardly toward the interior of the pertaining cylinder, and tie rod means common to and arranged between two adjacent ones of said inwardly curved portions for tieing said cylinders to their cylinder heads and the crank case pertaining thereto.

2. An arrangement according to claim 1, in which said relatively short curved portions within the region of said tie rod means are pre-cast.

3. An arrangement according to claim 1, in which the depth of said relatively short curved portion is rather slight with regard to its width.

Images