US 1418668 A
Description (OCR text may contain errors)
G. H. NOBBS.
INTERNAL COMBUSTION ENGINE.
i I APPLICATION FILED NOV-22, 1919. 1,418,668.
m u M N Z m Z d I M Q% E m H XNJEM P .l n v m: N f B 1% G M. M
GEORGE H. N'OIBIBS, OF WATERTQWN', MASSACHUSETTS.
Specification of Letters Pam- Patented June a, 1922 To all whom it may concern Be it known that I, GEORGE H. blows, a citizen of the United States, residing at Watertown in the county of Middlesex and State of l assachusetts, have'invented certain new and useful Improvements in Internal-Combustion Engines, of which the following is a specification.
Thisinvention relates to improvements in internal combustion engines. More particularly it relates to two stroke cycle engines, and, therein, to the deflector on the top of the piston and to means for balancing the eccentricity of the crank pin.
The invention is illustrated as it may be applied to a small engine suitable for use in portable machinery, having been de veloped by me in connection with a small tractor wherein it was desirable to provide the required power with a relatively small weight of engine; but it appears that the in' vention can be applied advantageously to engines otherwise constructed, used for any of a wide variety of purposes, the general effect of applying the improvement to an existing design of engine being to give ease of starting, steadiness and certainty of operation, and a high degree of perfection of combustion, qualities which always have been difficult to attain, and often have been grievously lacking, in small engines hereto- 'ore made, of which engines used in small boats are an example. In addition, it is observed that more power is obtained from a given engine by the use of the invention therewith. The improvements in question comprise making the deflector, which extends as a chord across the top of the piston, extend to the very periphery: of the,
cylinder so that its end faces approximately bear against the cylinder walls, thereby preventing passage of gas between the end ofv the deflector and the cylinder wall; and comprises the making of the necessary balance for the crank pin by cutting a segment away from the balance wheels. The cutting is on the same side of the axis with the crank pin and is symmetrical with respect to an extension of the medial plane of the crank. While the removed portion is not necessarily in the strict form of a segment, it appears to be important that it be in'substantially that form, approaching it sufficiently to constitute a material change of exterior form of the wheels, as distingu1 shed,for example, from the mere eliminat1 0n of an equal amount of material by borrngsa therein. It seems probable that the improved results noted follow from the change in shape of the containing chamber which occurs,
space, into the crank chamber. and adjacent part of the cylinder, and its transferthence into the workln part of the cylinder. As develope by me, it has beenapplied to an by suitable. exf rrso s'rA'r s PATENT OFF E:-
.60 in such a construction as a result of the rotation of the segmental: between the time of intake of charge pression in the appended claims, whatever features of patentable novelty exist in the invention disclosed.
In the accompanying drawings, which illustrate an embodiment of the invention Figure 1 is a side elevation in medial section through the cylinder, piston and shaft of ,a two stroke engine;
Figure 2 is a similar medial section, lookin endwise of the shaft;
igure 3 is a detail of the spective; and 7 Figure 4 is a detail, of one of the fly wheels seen in the same direction as in Fig: ure 2. r Referring to the drawings, 10 indicates piston in pera cylinder having a piston 11, a piston rod 12, and a crank 18 on a shaft 14. The cylinder has an intake port 15, below the piston, admitting .a charge to the crank case;
a passage 16 arranged to co-operatewith an admission port 17 in the piston for letting a charge that has been compressed in the crank case be transferred into the cylinder;
has on the piston a deflector 18, by which the charge admitted to the cylinder is directed upward; and has an exhaust port 19, all of which parts are arranged in any ordinary or suitable way, except for the special crank, fitting and substantially filling the. portion of the crank case where they are,
except such parts of it as are needed clear for motion of the crank and piston, and ex cept that the normal circular shape of the wheels is deformed by the removal of a segment leaving a flat side 22. The space thus left by the removal or absence of met-a1 from the perfect circular form of the flywheels symmetrically located with respect'to the radius which passes through the crank pin, and is sufiicient in size to afford a balance for the weight which is eccentrically disposed in the crank pin and its associated parts. It is, therefore, on that side of the fly wheels which is toward the piston when the piston is at inner dead center,as illus trated in Figure 2. The removal of sufficient material to effect the desired balance is also sufficient to leave an open space of substantial extent within the solid of revolution described by the fly wheels. Said solid of revolution fits the crank case closely, and as the metal of the wheels substantially fills it, and thus ills that portion of the crank case, except as is requisite for move-' ment of the connecting rod, the space for containing the charge is mostlyconcentrated in a body above. /Vhen the piston is at the inner end of stroke, as illustrated, the open space left by the absence of material from the fly wheels is continuous with the main body of charge-holding space enclosed bythe lower portion of the cylinder and the upper portion of the crank case. The in take port 15 is open, while the piston is approaching the said position, and is closed by a check valve, notshown in the draw-- ings, during recession therefrom, as is common practice. During all of this time, the said space contains substantially all of the air and gas which are to constitute the next charge With an engine built in the proportions indicated in the drawing, there is about a third of revolution from where the segment begins to connect with the said main space, to where it ceases, as shown by the interval between initial and final positions of the chordQQ indicated by dash lines 22 and 22'. During this interval, the flat surface 22 is sweeping around, changing its angle through nearly a complete reversal, and at the same time is rapidly shifting the shape of the lower end of the main space; and this occurs at a time when the piston and upper end of the piston rod are rela tively stationary. It is my opinion; that the sweep of the chord past the axis of the piston, with the resulting change of shape of the lower part of this main space, and deflection of gass therein, produces such a fanning and ag ation of gaseous contents reaching up into the upper part of the space in its effects that themixture of air and gas therein is perfected, thus producing in1- provement in the operation of the engine. In particular, the engine on which comparative experiments have been made is observed to get its initial ignition or starting more easily, to deliver greater power, and in general to run more steadily and with more perfect combustion.
M Another feature contributing to these improved results is the arrangement of the deflector. This is best illustrated in Figure .3, where the end portion of the deflector is clearly represented as being a cylindrical surface continuous with and of equal curvature with the cylindrical surface of the piston, which, of course, is approximatelyof the same radius of curvature as is the cylinder wall. The advantage of this feature is that whereas hitherto it has been the practice to make the. deflector asimple ridge upstanding from the top of the piston and not reaching to the cylinder wall, I have discovered that a saving is effected by the construction described. I believe the. reason to be that at the time of transfer of charge into the part of the cylinder above the piston there is in progress a considerable rush of products of combustion out through the exhaust port, and that some of the incoming charge is drawn out with the products of combustion, passing between the ends of the deflector as heretofore constructed and the adjacent walls of the cylinder without being deflected upward into the top part of the cylinder according to the purpose for which the deflector is installed.
This loss is prevented by the construction now disclosed, in which the end of the def flector fits the cylinder wall, and the entire entering charge is projected with momentum upward;
. Details of construction of the engine be greatly varied. In the engine illustrated, the crank pin 13 is made integral with the two parallel crank arms 24: which are set.
into recesses in the two fly wheels 21; and the whole is held together by a single bolt 25 which passes through an axial hole in the crank pin and so clamps together the two fly wheels 21, with the two arms 24; set in their respective recesses 24 so that the fly wheels have to rotate with the arms and therefore with the crank pin. The fly wheels are further held together, by the bushings in the crank case, where the main shaft passes through it. This makes an extremely simple construction, in which the compact ness and security of fastening, and the inexpensiveness of labor and machine costs in manufacture are features of advantage.
I claim as my invention 1- 1. The combination, in an internal combustion engine, of a cylinder and a crank case arranged to receive a mixture of fuel and air, and a balance fly wheel rotatable within the crank case, having its sides and face closely fitting the walls thereof except that said wheel is deformed from circular shape on a part of its face which rotates past the cylinder end between the time of intake and discharge of said mixture.
2. The combination, in an internal combustion engine, of a cylinder and a crank case arranged to receive a mixture of fuel and air; a crank in said case; and a pair of balance wheels, attached to the crank therein on its opposite sides and rotatable therewith; each of said wheels fitting within and approximately filling the case on its side of the crank, except that its face is deformed from circular shape, so as to agitate the said mixture during its rotation.
3. The combination, in an internal combustion engine, of a cylinder and a crank case arranged to receive a mixture of fuel and air; a crank in said case; and a pair of balance wheels attached to the crank therein on its opposite sides and rotatable therewith; the said flywheels approximately filling the space in the case around the crank shaft and beside the crank, and being set with the path of revolution of their faces close to the lower limit of piston travel; there being a weight-balancing and mixture agitating deformity from circular shape on the face of each wheel, on the same side of the axis with the crank.
4. The combination, in an internal combustion engine, of a cylinder and a crank case adapted to receive a mixture of fuel and air, a crank in said case and a flywheel attached thereto with its face closely fitting the circular wall of the case except where the wheel is minus a segment cut ofi' by a chord extending across the side of the wheel outside of its connection with said crank; said cut oil portion of the facebeing so arranged as to pass the cylinder end during the time when the capacity of said end is changing slowly.
5. The combination, in an internal combustion engine, of a crank case, a crank shaft and crank therein, and a pair of fly wheels mounted on said shaft and attached to said crank and approximately filling the space in the crank case around the shaft and crank, except forthe space in which the connecting rod moves; the crank comprising a hollow crank pin and two arms rigid therewith extending perpendicular to the shaft between and recessed in the fly wheels, combined with a bolt passing through both wheels and the hollow of the pins; the crank case being arranged to supplement said bolt in preventing the fly wheels from spreading.
6. The combination, in an internal combustion engine, of a cylinder and crank case constituting a mixing chamber adapted to receive and enclose a preparatory mixture of fuel and air; a crank in said case and a fly wheel attached thereto and nicely fitting within the crank case with its perimeter in close proximity to the open end of the cylinder; said perimeter being circular except that on the side of the axis which is toward the crank pin the circle is broken for a distance approximating the cylinder diameter, whereby the said chamber undergoes continuous change of shape as the noncircular portion of perimeter moves past the open end of the cylinder, while the chamber volume is changing relatively slowly.
Signed at Boston, Massachusetts, this 15th day of November, 1919.
GEORGE H. NOBBS.