Internal-combustion engines – Multiple cylinder – Cylinders radiating
Reexamination Certificate
2001-08-24
2003-07-22
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Multiple cylinder
Cylinders radiating
C123S197400
Reexamination Certificate
active
06595167
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to the field of engines and methods of manufacturing engines and more particularly to an engine, and a method of making the engine, that allows for a number of engines of varying horsepower outputs to be manufactured from a relatively small number of basic engine components.
2. Description of the Related Art
Internal combustion engines are known in the art. Various methods of manufacturing such internal combustion engines have been devised and disclosed.
Some have tried to streamline and improve the process of manufacturing internal combustion engines. For example, U.S. Pat. No. 4,622,864 to Fetouh purports to disclose a reciprocating piston engine including a modular power transmission sub-assembly. The invention purports to provide a lightweight and low-cost engine construction.
U.S. Pat. No. 3,941,114 to Seifert purports to disclose a cylinder crankcase for a multi-cylinder internal combustion engine in which the crankcase consists of welded-together cast housing elements that are connected in series in a building-block-like matter.
U.S. Pat. No. 5,456,076 to Zornes discloses an external heat source engine that includes a telescopic crankcase structure. The engine structure may be constructed so that two or more sub-systems are housed in one or more modules according to the specification of the patent. Two or more power modules may then be coupled together and engine power and speed control may be obtained by varying the relative phase angle of the couple.
U.S. Pat. No. 4,676,205 to Kaufman purports to disclose and arrangement for mounting a two-stroke cycle vertical crankshaft internal combustion engine onto a rotary mower deck to accept a four-stroke cycle vertical crankshaft internal combustion engine whereby either type of engine may be adapted to the same mower deck.
U.S. Pat. No. 4,610,228 to Fink et al. purports to disclose a crankcase assembly for an engine to be mounted to and associated with a portable tool such as a chain saw. A plastic crankcase is connected to the cylinder of the engine and an annular insulating member is mounted between the cylinder and the crankcase.
In light of the prior art, the possibility for improvements still remain and are desirable for improving the efficiency and cost of the manufacturing process for engines, and especially smaller horsepower internal combustion engines such as might be used in the lawn care industry. In this industry, for smaller lawn care products, a large percentage of the product cost is due to the cost of the engine itself. For example, as of the date of filing this patent application, it is not uncommon for some walk behind lawn mowers to cost less than $100 even though those walk-behind lawn mowers are provided with an internal combustion engine of five horsepower or more. With cost pressure keeping the retail price of this product low, it is important that improvements in the efficiencies in the manufacture and design of the engine itself be made in order to provide adequate profit to the manufacturer of the lawn mower.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a method of providing a family of engines so that greater manufacturing efficiencies are obtainable is disclosed. The invention provides a modular engine design system for designing a family of engines. The engines in the family of engines provide for a variety of power outputs to be achieved without major redesigning of engine components. Each engine comprises at least one cylinder block defining a cylinder therein, a crankcase having an opening therein communicating with the cylinder, a piston adapted for reciprocal movement in the cylinder, a crankshaft adapted for rotational movement within the crankcase, a connecting rod interconnecting the piston and the crankshaft, and a camshaft for controlling the intake valve and exhaust valve assembly.
In accordance with the invention, the modular engine design system provides a basic engine design capable of generating a first range of power output. For illustrative purposes only, and not by way of limiting the present invention, the basic engine, for example, may be capable of generating about 3.5 to 4.5 horsepower, inclusive. The basic engine design utilizes basic engine components, designated by the letter A, which include: a first cylinder block (A) defining a first cylinder (A) of first predetermined dimensions, a first crankcase (A), a first piston (A), a first crankshaft (A), a first connecting rod (A) of length L
1
, and a first camshaft (A).
In accordance with the invention, the modular engine design system provides a second engine design for providing a second engine capable of generating a second range of power output, greater than the power output of the basic engine. The modular engine design system utilizes a plurality of engine components that are substantially structurally identical to the basic engine components in order to achieve the desired power output range. For ease of illustration, different alphabetic labels will identify engine components that differ structurally from the basic engine components.
The second engine design may, for example, provide an engine capable of generating about 5.0 to 6.5 horsepower. This second engine design would utilize a plurality of the basic engine components. For example, the second engine design might utilized a first cylinder block (A), defining a cylinder (A) having the same predetermined dimensions, a first piston (A), a first crankcase (A), and a first camshaft (A) are basic engine components utilized in the second engine design.
However, in the inventive engine design system, several of the basic components are selectively replaceable with modified components. For instance, in the exemplary second engine design, the first connecting rod (A) is selectively replaced with a second connecting rod (B), having a length L
2
. Likewise, first crankshaft (A) is selectively replaced by second crankshaft (B). In this example, L
2
is less than L
1
. The power output is directly related to the amount of displacement, or piston stroke, of the piston within the cylinder. In a cylinder of predetermined diameter, a longer stroke correlates to a greater cylinder volume, and a shorter stroke correlates to a lesser cylinder volume. A shorter connecting rod allows for a longer stroke within cylinders of the same predetermined dimensions, and hence more power. Therefore, in the modular engine design system of the present invention, changes in the length of the connecting rod, while keeping the cylinder/piston dimensions the same, provide for the changes in power output from the basic engine to the second engine in the family of engine designs.
The modular engine design system utilizes several common engine-building components that are adapted to be used with modified engine components to provide a family of engines of varying power outputs. Therefore, in the modular engine design system, greater manufacturing efficiencies can be achieved.
In accordance with yet another feature of the invention, a third engine design is provided. The third engine design utilizes a third crankshaft (C) adapted to receive two first connecting rods (A, A), each having a length L
1
, which are operatively connected to two first pistons (A, A). This third engine design utilizes two of the first cylinder blocks (A, A), each of which define a first cylinder (A) of first predetermined dimensions. A modified crankcase (B) is provided which has one opening that communicates with one of the cylinders and a second opening that communicates with the second cylinder. A modified camshaft (B) is also provided to operate the valve assemblies associated with each cylinder/piston combination.
In accordance with yet another feature of the invention, a fourth engine having a power output greater than the basic engine is provided through a fourth engine design. Again, a plurality of basic engine components is utilized. For example, the fourth engine design utilizes a fourth crankshaft (D) adapted to re
Argenbright Tony M.
Harris Katrina B.
MTD Products Inc
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