Marine engine

Abstract

In an internal-combustion marine engine positive crank case ventilation is provided by the eductive action of air entering a downdraft carburetor mounted in an enclosed compartment between the cylinders. The eductive effect acts through passages between the compartment and the crank case to ventilate the crank case through the passages, through the enclosed compartment and thence into the carburetor without requiring ventilating tubes extending from the crank case. A centrally feeding manifold is clamped to the cylinder block solely by the cylinder heads which are secured to the block over the edges of the manifold.

Description

BACKGROUND OF THE INVENTION

This invention relates to an improved marine engine and more particularly to an improvement in engines of the type shown in U.S. Pat. No. 3,233,598 Van Ranst.

That patent describes a marine engine in which a cover forms a generally closed compartment between the V-type cylinder banks. An air horn in the compartment delivers air to the side entrance of a carburetor also mounted in the compartment. Air entering the air horn produces an eductive action which ventilates the crank case through passages between the compartment and the crank case.

SUMMARY OF THE INVENTION

In accordance with this invention a downdraft carburetor increases the volumetric efficiency of an internal-combustion engine while providing positive crank case ventilation through a generally closed compartment connected by passages to the crank case. The cover which forms the generally closed compartment has an annular extension surrounding an opening in the cover. A flame arrester is mounted over this opening. An annular passageway is formed between the annular extension and a cover for the flame arrester. Carburetor air passing through this passageway produces an eductive effect which provides the positive crank case ventilation.

In accordance with another aspect of this invention the centrally feeding manifold is clamped to the cylinder block solely by the cylinder heads which are secured in place over the edges of the manifold.

Other objects, features and advantages of the invention will be better understood from the following more detailed description and accompanying claims.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view taken in section of the engine; and

FIG. 2 is a side elevational view in cross section of the engine.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The engine includes a cylinder block 12, cylinder heads 13 and 14 and a crank case 15. Cylinder block 12 has six cylinders 16 arranged in pairs on opposite sides thereof, the cylinders extending upwardly and outwardly to form a V-type engine. The invention is also applicable to 2, 4 and 8 cylinder V-type engines.

A crank case pan 17 extends below the crank case. Crank shaft 18 has piston rods 19 and 20 connected to the throws thereof. Cam shaft 21 is rotatably mounted above the crank shaft. Inlet valves 22 and exhaust valves 23 are connected by links and rocker arms to the cam shaft 21. Exhaust manifolds 24 are integrally formed within cylinder heads 13 and 14. A cover 25 is bolted and secured by the seal 27 to the cylinder heads 13 and 14. The cover forms a central compartment 28 between the cylinder heads.

What has been described thus far is an engine of the type shown in the aforementioned Van Ranst patent and the description of that patent is incorporated herein by reference.

In accordance with this invention a downdraft carburetor 29 is mounted in the compartment. A centrally feeding manifold 30 has branches leading to the inlet valves 22. An entrance in the top of the intake manifold is connected to the downdraft carburetor 29.

The cover 25 has an annular extension 31 which surrounds an opening in the top of the cover 25. A flame arrester 32 is positioned in this opening and a dome-like cover 33 is placed over the flame arrester. The downdraft carburetor feeds fuel and air directly into the manifold 30 which is beneath it. This increases the volumetric efficiency of the engine and results in an increase in the horsepower. A greater volume of air and fuel can be fed into the manifold in this manner.

A plurality of apertures 34 are part of passages between the compartment 28 and the crank case 15. Air which enters the compartment under cover 33 and over extension 31 to the carburetor 29 has an eductive effect. This effect applies a pressure to the crank case to ventilate it through the passages and through the compartment 28. Unburned gases in the crank case are pulled into the carburetor in this manner. This effect is generally referred to as positive crank case ventilation. Note however, that it is accomplished without the need for tubes extending from the crank case as is common in automotive-type engines.

As another important feature of this invention, the manifold 30 is clamped to the cylinder block solely by the cylinder heads 13 and 14. The head 14 is clamped by the cylinder head by bolts 36. The edge portions 37 of the cylinder heads extend over the manifold 30 to hold it in place. Openings in the head align with openings in the manifold. A gasket 38 provides a seal around these openings. We have found that the manifold can be firmly secured in place in this manner and this obviates the need for separately securing the manifold to the engine block thereby facilitating production of the engine.

While a particular embodiment of the invention has been shown and described various modifications are within the true spirit and scope of the invention. The appended claims are intended to cover all such modifications.

Claims

What is claimed is:

1. In an internal-combustion engine of the type including:

a cylinder block,

first and second banks of cylinders is said block, said banks being upwardly and outwardly inclined,

a pair of cylinder heads secured to said block,

a cover extending across and sealed to said cylinder heads and cylinder block, whereby a compartment is formed between said cylinder heads by the cylinder heads, cylinder block, and cover,

a crank case at the lower portion of said cylinder block, and

passage means between said compartment and said crank case, the improvement comprising:

a centrally feeding manifold mounted in said compartment centrally of said cylinders and having an entrance in the top thereof,

a downdraft carburetor mounted on top of said manifold and connected to the entrance of said intake manifold, said downdraft carburetor having a vertical passageway for flow of air through a top opening downwardly into said entrance of said intake manifold, said separately feeding manifold being separate from said cylinder block, said cylinder heads being secured to said cylinder block over said manifold to hold said separate manifold on said cylinder block solely by the clamping of said heads to said block,

an annular extension surrounding an opening on said cover above said carburetor, said annular extension and said carburetor forming an annular passageway, and

a cover for said carburetor positioned above said annular extension to provide an opening between said annular extension and said cover for flow of air inwardly to and downwardly through said carburetor, said flow of air applying by eductive effect a negative pressure to said annular passageway which acts through said passage means to provide positive crank case ventilation.

2. The engine recited in claim 1 further comprising:

a flame arrester positioned in said opening.