US2291048A - Carburetor - Google Patents

Description

July 28, 1942.

J. LICHTENSTEIN CARBURETOR 2 Sheets-Sheet 1 Filed June 29, 1939 INLET F052 D MUTWRTING FLUID /2 A J OUTLET FOR MOTIVRTING FLU] INV EN TOR.

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LICHTENSTEI N 2,291,048 I CARBURETOR Filed June 29, 19.39 2 Sheets-Sheet 2 I NV EN TOR. c/OHHN 1 ICHTENTE/N.

a ATTORNEY;

Patented July 28, 1942 Johan LichtensteimLevallois-Perret, France. as-

signoito Societe 'Generale des Carburateurs Zenith, Geneva, Switzerland, a corporation of Switzerland Application June 29, 1939, Serial No.

In France July 5, 1938 4 Claims. (01. 261-39) This invention relates to an improvement in automatic altitude correctors for internal combustion engines in which a manometric capsule controls, by means, of a servomotor, a member which regulates the richness of the combustible mixture delivered to the engine.

It is known that these manometric capsules are relatively fragile and delicate, also that it is difllcult to obtain a series of capsules having identical mechanical characteristics, that is to say, producing the same elongation for a given a variation in the pressure to which they are sub- J'ected.

An object of the invention is to decrease the fatigue experienced by the manometric capsule of an automatic altitude corrector of the kind referred to, and also to decrease the risk of rupture of said capsule. A further object is to make it possible to produce'a plurality of altimetric correctors which will operate alike in spite of differences in the mechanical characteristics of the individual capsules mounted therein. 7

According to the invention the capsule of the corrector is connectedto the pilot member 'of a servomotor and is biased by a spring. The pressure exerted by the spring upon said capsuleis controlled by the motor member of the servomotor, which also actuates the member controlling the mixture richness. The servomotor remains at rest for any-given value of the pressure acting upon the capsule, but if that pressure varies and reaches a new value the capsule elongates or contracts correspondingly, thereby displacing the pilot member or the servomotor. The motor member of the servomotor is thereby put into movement, and by such movement modifies the pressure exerted by the spring upon the capsule and correspondingly changes the length of the capsule in such direction as to restore the capsule to its initial length and the attached pilot member to its neutral position. Operation of the servomotor, and hence further movement of the motor member, is thereby arrested.

Because of the arrangement just described,'the

capsule is always brought back to its initial length irrespective of the. pressure to which it is subjected. It therefore is subjected only to such slight variations in length as are necessary to the starting of the servomotor. In the devices of the prior art, wherein the capsule elongates hardening and rupture of the capsule. This disadvantage is avoided by the control structure herein disclosed.

Furthermore, the degree of deformation of a capsule which is freely dilated or contracted by means of pressure variations to which it is subiected, depends upon the elasticity of the capsule,

which. characteristic is-very diiiicult to obtain in These.

uniform degree in a series of capsules. variations in elasticity between individual capsules in the known altitude correctors result in difierent operating characteristics in altitude correctors of the same series. This difliculty is avoided by the arrangement disclosed herein, in which the capsule remains at substantially the samelength, thereby eliminating the influence oi! the elastic characteristics of the capsule upon the operation of the device.

The description which follows, taken in connection with the appended drawings, given as an example, will explain the manner in which the invention may be practiced.

Figure 1 is'a vertical elevation, partly in section, of a carburetor embodying the invention, the parts of the altitude control being in the positions which they would assume at ground level.

Figure 2 is a vertical section of the altitude control unit with the parts inthe positions which they would assume at altitude.

Figure 3 is a partial sectional view of an alternative arrangement for controlling the mixture richness and is adapted to be controlled by the altitude control unit represented in Figures 1 and 2. v

The invention is shown in Figure 1 as applied to a carburetor of any known design, having an induction passage A, controlled by a throttle B and having a fuel nozzle 0 discharging into a venturi D. The air entrance E to the induction passage may be controlled by a choke valve F.

The altitude correctorrepresented in Figures 1 and 2'has a capsule i located within a casing and contracts due to the variations in pressure p to whichit is subjected, the capsule experiences relatively great variations in length each time it is subjected to material pressure variations, and

eventually these repeated length variations cause 2. The stem 3 of the capsule is threaded into the end wall of the casing, so as to permit the initial adjustment to be made, after which the stem may be locked in position by known means.

The casing 2, containing the capsule i, com= municates with atmosphere through 'a port 2@, but it may instead be connected to any other suitable pressure to eflect the altitude correction.

The servomotor illustrated in the drawings is of the oil pressure actuated type in which the pilot member is a plunger 4 sliding in a cylindrical.

sleeve 5. while the motor member comprises a it of piston 6 is connectedv through a link II with a lever l8, pivoted at I! to the body of the corrector. Lever I8 is provided at its outer end with a roller 22 which engages a cam surface 23 on a lever 20, which is pivoted at 2i. Surface 23, as shown, is straight but it may be of curved form in order to obtain any desired relation between the movement of piston 6 and the movement of lever 20. The other end 24 of lever 20 operates the spring i through the cup member 25.

Piston 6, which is the motor member, or driven member, of the servomotor, is connected by any suitable means to the member regulating the mixture'richness, which may. be of any desired typ In Figure 1, the member regulating the mixture richness has been represented as a needle 21 controlling theeffective cross-section of a calibrated orifice 28 which meters the fuel delivered to the mixture passage of the carburetor through a duct 2!. The stem III of the needle 21 is slid-' ably mounted in a guide 3i formed in the cover of the float chamber 32, in the bottomof which is the calibrated fuel orifice 28. Stem ll is connected to a floating lever 23, one end of which is pivoted to a connecting link 34, which is intum connected to the piston 6 through connecting Plunger 4 thereby moves towards the left and groom I of plunger 4 eflects communication between the cylinder 1 and the oil inlet l2 which communicates with a source of oil under pres- 5 sure. The oil under pressure pushes piston 8 downwardly, against the force of spring i4, and' pivots lever ill about its axis ii. Roller 22, mounted at the end of the lever II in engagement with surface 23, tates lever 2| in a clockwise in direction. End 24 of lever 2| thereby compresses spring II, and, under the effect of this compression, plunger 4 moves towards the right, compressing capsule i. The movement of piston I ceases when, under the pressure of the spring ll,

- 5 the pilot member 4 of the servomctor has been brought to its original pomtion, in which the central part II of the plunger closes the port Ii and cuts oil! the flow of oil under pressure to cylinthe force exerted by spring Ii balances the force link l1 and rod IS. The other end of lever 32 is joined to a bell crank lever 35 which is operated by the pilot means of a rod or cable 38. Needle 21 is thus coniointly operable by hand as well as by the automatic altitude corrector.

of the capsule i created by the decrease in the atmospheric pressure applied to said capsule. The lengthof the capsule therefore remains substantially unchanged. 1

Conversely, if the altitude decreases, capsule l contracts inresponse to'the increase in atmospheric pressure acting on it and plunger 4 moves toward the right, thereby eifecting communication between the port II and the discharge outlet by means of groove 8; Piston 6 moves upwardly in response to the force of the spring i4,

and the movements of the piston are transmitted tolever 20, the end 24 of which moves to the left and thus decreases the compression of spring ll.

The movement of the piston ceases when thepilot In Figure 3, the member regulating the richness of the mixture consists in a profiled valve 31 which regulates the depression transmitted to the float chamber 38 of the carburetor. Valve 31 regulates the effective cross-section of the calibrated orifice 3O throughwhich the space 42, situated above the fuel level in fioatchamber 3|, communicates with a chamber 4|, to which is 'transmitted, through duct 4!, the depression obtaining in the mixture passage of thecarburetor. Space 42 also communicates, through a callbrated orifice 43 and a duct 44, with atmosphere or with the air intake of the carburetor. Valve 3] is carried by a stem 4! which is operated man- .ually and by the automatic altitude control, in

the same way as stem III of the mechanism shown in Figure 1. v

The operation of the mechanism is as follows: On the ground, the various members ofthe automaticaltitude control occupy the pomtionsv represented in. Figure 1.'.The pilot member of member of the servomotor (plunger 4) hasreturned to the neutral position, at which time the capsule I has recovered its original length.

The variations in the atmospheric pressure or any other pressure which may be transmitted to capsule I to obtain an altitude correction) are exclusively compensated for by variations in the length of and the force exerted by spring ll, hence the elastic characteristics of capsule I do not play any part in the functioning of the apparatus. Also,'the deformations to which the capinitial length by the functioning of the servo'consule is-subiected are reduced to the small amounts necessary for the starting of the servomotorfthat is to say; for uncovering port ii, the capsule being brought immediately back to its trol. The capsule is thus but little deformed during variations in altitude, and its fatigue and the risks of rupture are correspondingly decreased.

when the apparatus has risen from the ground 00 level to a predetermined altitude, the movement the servomomcupia .the neutral positioninwhich the in part II of the plunger 4 closes port ll. Under these conditions, the. motor member (piston t) of the servomotor is at rest. If the hand control connected tolever'fl by cable ll (I'igura 1 and 3) occupiu the position "normal richness," the needle 2I.(Figure 1) or valve 21 (Figure 3) occupies such a position that the mixture delivered by the carburetor is of proper richness for operation onth'e ground.

If the apparatus leaves the ground to go up in altitude, the atmospheric pressure acting on capsule i decreases, and the capsule elongates.

' of. the motor member (piston I) of the servo motor has been transmitted by means of rod l0. connecting rods i1 and 34, and lever-.33, to the stem II and needle ll (Figure l), or tostem 4' andlvalve 31 (Figure 3). The profile of needle 21 or valve 3! is such that at each altitude the composition of the mixture is correct when the hand controlis maintained in the position "normal richness." v v For any given altitude, the pilot may modify the richness of the mixture by operating lever I! by means 'of the control ,cable a.

Piguresland2disclose,asanexample,a servo motor using oilunderpreuure as a motive iiuid, but it is clear that, as'far as the invention is concerned, a servo motor of any type may be used. For example, one might utilize a pressure fluid other than oil, such as air from the outlet oi a supercharger delivering air to the engine. An electric servo motor may also be used in which, for example, the motor member of the servo motor is actuated by an electric motor through an endless screw, and the pilot member consists of a switch or commutator placed in the circuit of the electric motor. The invention may be readily applied to an altitude corrector having a servo motor of this. kind. The capsule is in such case joined to the switch or commutator which replaces plunger d of the mechanism represented in Figures 1 and 2. The motor member of the servo motor is driven by the endless screw and is connected to the device regulating the richness of the mixture (needle 21, Figure 1, or profiled valve 87, Figure 3) and operates a lever such as lever 2i? represented in Figures 1 and 2, which operates the spring biasing the capsule. The operation is then entirely similar to that of the apparatus described above, and it is unnecessary to describe it further, since the nature of the servo motor in itself is not an essential element of the invention.

I claim: I

1. A mixture control for a charge forming device including a sealed capsule responsive to the difi'erence in pressures acting on the inside and outside of said capsule, an element for varying the mixture richness, and a servomotor for actuating said element comprising a motor control member in alignment with said capsule and secured thereto to be directly actuated thereby, a driven member operatively connected to said element, a spring biasing said capsule, a separate 'spring biasing said driven member, and means connecting the driven member and the first named spring for varying the pressure of said first named spring upon movement of the driven member, said connecting means comprising a pair of pivoted levers having a cam and follower connection therebetween.

2. In' a servo motor for a carburetor altitude control having an element for controlling the mixture richness, a valve for controlling a motivating fluid, a movable wall adapted to be actuated by the fluid, means operatively connecting the movable wall and the element, a barometric capsule directly connected to the valve in abutting relation-therewith for directly actuating the valve, aspring yieldingly resisting movement of said valve in one direction, means interconnecting said movable wall and the spring to vary the resisting force of the spring, and a second spring biasing the movable wall.

3. A charge forming device having an induction passage, a fuel chamber, a fuel conduit connecting said chamber with the induction passage, and an altitude control unit comprising a servomotor having a pilot member and a motor membar, a barometric capsule operably connected to said pilot member and biased by a spring, a sec- ,ond spring biasing said motor member, means sion of said spring upon movement 01' the motor member.

4. In a fluid operated servomotor for a carburetor mixture control, a valve for controlling the flow of motivating fluid, a movable wall sub- J OHAN LICHTEN STEIN.

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