US2689552A - Reed valve for internal-combustion engines - Google Patents

Description

P 1954 E. c. KIEKHAEFER 2,589,552

REED VALVE FOR INTERNAL-COMBUSTION ENGINES Filed Sept. 11. 1950 y flornen" Patented Sept. 21 1954 REED VALVE FOR INTERNAL-COMBUSTION ENGINES Elmer C. Kiekhaefer, Cedarburg, Wis. Application September 11, 1950, Serial No. 184,243

3 Claims. (01. 123--73) This invention relates to reed valves for crankcase induction for two-cycle engines and partic- I ularly to improved operating characteristics of such valves.

The invention provides a leaf-spring supported reed valve which is also more easily controlled for specific performances over a wider range of operating speeds.

The principal object of the invention is to provide a reed valve which is less subject to breakage and failure.

A further object is to provide a reed valve which will open readily and sufficiently at low speeds for dependable operation at reduced throttle and which at high speeds will close without an appreciable time lag at the end of the induction cycle so as to avoid pressure losses.

Another object is to eliminate operating variations due to different conditions of lubrication.

These and other objects and advantages will be more fully set forth in the following description of a preferred embodiment of the invention as illustrated in the accompanying drawmg:

In the drawing:

Figure 1 is a cross-sectional View of a twocycle, alternate firing, two cylinder engine with an induction manifold and reed valve unit embodying the invention hereinafter described;

Fig. 2 is a detail plan View of the reed valve unit employed in the engine shown in Fig. 1;

Fig. 3 is a sectional View taken on line 3--3 of Fig. 2 showing the upper valve closed and the lower valve fully open;

Fig. 4 is a sectional view taken on line 4-4 of Fig. 1 showing the manifold passages and ports controlled by the lower reeds; and

Fig. 5 is a view similar to Fig. 3 approximately illustrating the reed valve partly opened.

The engine I shown in the drawing includes the crankshaft 2 and crankcase 3. The cylinder block 4 of the engine is provided with the cy1- inder bores 5 and 6 which open into the respective separate crank chambers i and 8 of the crankcase.

The pistons 9 are carried in cylinder bores 5 and B and connected by-the rods I0 to corresponding cranks of the crankshaft. In engine I shown, the pistons reciprocate in opposite directions providing alternate power strokes with each 180 of rotation of the crankshaft.

The carburetor II is secured to and carried by crankcase 3 and communicates through opening l2 with the passages l3 in the valve block 14 dividing crankcase 3 into the chambers l and B. Passages l3 extend from opening 12 between chambers l and 8 and communicate with the latter through the ports IS in valve block M.

In the operation of the engine the mixture of fuel and air is drawn into each of chambers 'i and B with the Lip-stroke of the corresponding piston 9. The mixture enters through passages !3 and passes into the chamber through the respective ports l5. In the down-stroke of the piston the respective ports I5 are closed, as will be described, and the fuel mixture is compressed within the chamber.

A passage l 5 within cylinder block 4 communicates with each of chambers l and 8 and opens into the respective cylinder bore through the ports ll. Ports I l of each cylinder are uncovered by the respective piston at the end of the down-stroke to admit the compressed fuel mixture from the chamber below the piston to the cylinder bore above the piston through passage l6 and ports [1.

The exhaust ports [8 are disposed opposite ports I? and are opened by the piston to allow discharge of the exhaust gases and displacement of the remaining exhaust gases by the fuel mixture entering through ports [1.

The valve block [4 comprises complementary semi-cylindrical sections which are assembled on the center bearing of crankshaft 2.

The reeds H] are secured to the upper and. lower faces of block Hi and extend over the ports to close the latter. Each reed comprises a thin piece of spring steel which is absolutely straight or flat. one end, and the unsecured end is normally seated on the face of the block around the respective port to effectively close the port. A rocker 20 is secured to block M over the fixed end of each reed and projects over the reed in a predetermined arc.

In the operation of the engine as described, a reduced pressure obtains within a chamber 5 or 1 with each up-stroke of the respective piston. The atmospheric pressure within passages i3 being greater, the difference in pressures acting on opposite sides of the reed causes the unsecured end of the reed to be unseated from block I4 opening the port to the admission of fuel mixture to the chamber. The reed in being unseated opens the port and is flexed throughout its free length and to the extent allowed by rocker 20. Each rocker 20 comprises a rigid metal member which is curved to limit the flexing of the reed so that the flexing is evenly distributed throughout.

Each reed is secured at only The block [4 with passages l3 and reed controlled ports 15 as just described comprise an induction system for alternate firing two-cycle engines as described and claimed in the copending application of the present inventor, Serial Number 11'7,325, filed September 23, 1949, now Patent No. 2,612,882 granted October '7, 1952, for Crankcase Induction for Two-Cycle Engine. Four ports 15 open from passages 13 into each chamber 1 and 3, and the reeds l9 and rockers 20 of each adjacent pair of ports [5 are secured by a single bolt 2| and located by two pins 22 projecting from the face of the block.

In accordance with the present invention, the secondary reed-like spring 23 is disposed over each reed l9 intermediate the reed and the corresponding rocker 20. Each spring 23 is secured and located at its fixed end by the bolt 21 and pin 22 securing the corresponding rocker and reed. The body and free end of spring 23 extends over the reed and is normally fiat to aid in seating the reed on block I4 as described above. Preferably, spring 23 should be approximately as wide as reed l9 and at least as wide as the rocker.

The length of spring 23 is determined by the size and location of the port closed by the reed. Spring 23 is disposed to support a certain part of the reed in relation to the port while leaving the unsecured end of the reed free to flex independently of the spring. The unsupported free end of the reed is thus responsive to pressure within passages l3 substantially independently of spring 23 to a limited extent as illustrated in Fig. 5.

Under idling conditions carburetor H is throttled to limit the amount of air admitted and with the longer induction period of the engine, reeds l9 are not opened to the same extent as in high speed operation. idling requires that the cylinders receive a uniform fuel charge with each cycle.

According to the invention each reed i9 and port i5 functions as a dual reed valve. At low speeds requiring precisely limited admission of the fuel mixture to the chamber the free unsupported end of the reed operates to open and close the port or a part thereof. At high speeds requiring maximum admission of the fuel mixture to the chamber the entire length of the reed operates agains the spring to open fully the port to the fuel mixture. The spring 23 is subject to flexing similar to that of the reed and operates to return and reseat the reed as described.

According further to the invention, the reed and spring should have different natural frequencies of vibration.

Reeds adapted for high speed operation have a natural frequency of vibration which is responsive to some particular speed or frequency of operation of the reed. Such vibration has a tendency to weaken the reed so that breakage results through fatigue of the metal. In addition, it has been observed that with such vibration in the reed, the reed in reseating on the block strikes the block at the tip or free end. When this condition becomes sufficiently severe or the tip is downward coincident with the closing or reseating of the reed, the tip end will break across or will split lengthwise.

Spring 23 serves to dampen such vibration at natural frequencies whenever it occurs in the reed and by reason of the shorter length is not subject to a corresponding vibration at any similar frequency.

The operation of the reeds in response to pres- However, dependable sure pulsations is relatively unaffected by any excessive lubrication of the reeds. For uniform operation the oil film between the reed and valve block must be easily broken at low speeds otherwise the reed will tend to stick to the block. Spring 23 causes the tip of the reed to lift from the block first in opening the port and the oil film is then broken and the reed is free of the film.

Various embodiments of the invention may be employed within the scope of the following claims.

I claim:

1. A reed valve for engines and the like comprising a valve block having a gas supply passage and a port for said passage, a reed secured at one end thereof to said block and extending over said port, the unsecured end of said reed being normally flat and seated on said block circumferentially of said port to close the latter, a springsecured to said block over the secured end of said reed and supporting a part of said reed in the seated position, said reed being adapted to be unseated and open said entire port in response to a given gas pressure within said passage against the support of said spring and to reseat and reclose said port with the support of said spring, the unsupported part of said recs including the unsecured end thereof being adapted. to partially open said port substantially independently of said supporting spring in response to port and limiting the opening of th latter and the movement of said reed and spring to full open position.

2. In a high speed internal combustion engine employing the crankcase for induction and precompression of the fuel mixture, a portion of said crankcase comprising a valve block having a fuel supply passage opening into said crankcase through a port in said block, a flexible reed secured at one end thereof within said crankcase to said block and extending over said port, the unsecured end of said reed being no mally fiat and seated on said block circumferentially of said port and closing the latter, the unsecured end of said reed being adapted to be unseated and open said entire port in response to a given differential of gas pressure within said passage and said crankcase, said reed being of an elasticity whereby said reed is capable of reclosing said port successively at high frequencies in response to pulsating pressure conditions within said crankcase, a fiat spring secured. to said block over the secured end of said reed supporting a part of said reed in the seated position and damping said supported part of said reed in the open position against vibration, the unsupported part of the unsecured end of said reed being adapted to be unseated to partially open said port substantially independently of said supporting spring in response to less than said given gas pressure differential, and a fixed, rigid arm secured to said block and extending over said port limiting said reed and spring and the opening of said port.

3. A reed valve for engines and the like 0031- prising a valve block having a passage and. a port for said passage, a flexible reed secured at one end thereof to said block and extending over said port, the body and unsecured end of reed being normally fiat and seated on said block circumferentially of said port to close the latter and adapted to be unseated by a given pressure of the gas within said passage to open said port to i the gas, a fiat spring secured to said block over the secured end of said reed and supporting the References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 939,549 Reineking Nov. 9, 1909 1,022,157 Scott Apr. 2, 1912 Number 7 Number Name Date Decrow Mar. 7, 1922 Setz Feb. 21, 1922 Little May 13, 1924 Thege .1. June 5, 1928 Cullen et a1. May 7, 1935 Dugelay Dec. 22, 1936 Krenzke Mar. 26, 1946 Smith Jan. 18, 1949 FOREIGN PATENTS Country Date Great Britain 1915 Australia Oct. 3, 1946

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