US2857146A - Secondary throttle control for multi-stage carburetor - Google Patents

Description

Oct. 21, 1958 H. A. CARLSON SECONDARY THROTTLE CONTROL FOR MULTI-STAGE CARBURETOR Filed March 1, 1956 2 Sheets-Sheet 1 INVENTOR. HAROLD A. CARLSON ATTORNEY.

SECONDARY THROTTLE CONTROL FOR MULTI-STAGE CARBURETOR Filed March 1, 1956 Oct. 21, 1958 H. A. CARLSON 2 Sheets-Sheet 2 INVENTOR. HAROLD A. CARLSON ATTO RNEY United States Patent SECONDARY THROTTLE CONTROL FOR MULTI-STAGE CARBURETOR Harold A. Carlson, Brentwood, Mo., assignor, by mesne assignments, to ACF Industries, Incorporated, New York, N. Y., a corporation of New Jersey This invention relates to multi-stage, multi-barrel carburetors and, more particularly, to a novel mechanism for automatically controlling the throttle or throttles in the secondary stage or stages of such a carburetor system.

This invention is applicable to a multi-stage system such as shown by the patent to Braun 2,434,192 of January 6, 1948, and has for its purpose the elimination of the manually controlled set of throttles shown in the secondary stages, so as to achieve arnore compact design.

According to this invention, each secondary stage is controlled exclusively by a single throttle which is, in turn, provided with an automatic control responsive to engine demand, but limited in its degree of operation by the manual control of each primary stage. Each secondary throttle is eccentrically mounted in each secondary mixture conduit so as to tend to be opened to various degrees by the forces of suction or velocity created by the pumping action of the engine throughout a wide range of engine speeds. Connected with each secondary throttle is a suction motor orv the like acting to close the unbalanced throttle or throttles within a range of manifold pressures corresponding to part-throttle operation of the engine. This motor also controls the release of a latch for positively holding each secondary throttle closed so as to eliminate the tendency toward intermittent secondary operation and the consequent engine surging.

The manual control for the primary stage has the usual throttle return spring and includes a linkage between the primary'and secondary throttles which can limit the degree of opening of the secondary throttles to correspond with the degree of opening of the primary throttle. In addition, the manual control has an override to release the latch and partially open the secondary throttles as the primary throttles are moved to wide-open position, regardless of the action of the automatic choke. On closing of the primary throttles, the decrease in manifold pressure (increase in suction) causes the motor to close the secondary throttles, so as to relieve the throttle return spring of the additional force necessary to overcome the action of suction on the unbalanced secondary throttles.

With this system of control, the need for a second manually controlled throttle in each secondary stage, as

taught by Braun, is eliminated, and carburetor height can be reduced a corresponding amount.

In motor vehicles having an automatic transmission, it is often the case that extreme primary throttle opening exerts a control function on the transmission to cause a down-shift for maximum acceleration in the lower range of vehicle speeds. Under these conditions, the manual override can be used to give suficient secondary operation for maximum engine torque, whereas the automatic control', under these circumstances, might not give satisfactory throttle response for this purpose.

Other objects and advantages of the invention will become more apparent from the following description taken in connection with the accompanying drawings, in which:

2,857,146 Patented Oct. 21, 1958 Fig. 1 is a side view of a carburetor showing the relation of the parts when both primary and secondary throttles are closed.

Fig. 2 is a view similar to Fig. 1, illustrating the position of the parts of the throttle control system when the primary throttles are opened.

Fig. 3 is a side elevation of the opposite side of the carburetor shown in Fig. 1 with the automatic choke closed and the secondary stage throttles locked.

Fig. 4 is a view similar to Fig. 3, showing the secondary throttles unlocked.

Fig. 1 represents a conventional type of four-barrel carburetor equipped with an automatic choke. Since the novel features reside in the throttle control mechanism only, a detailed description of the carburetor construction will be omitted insofar as possible. In this View is shown a carburetor C having a throttle body 1, a float bowl section 2, and an air horn section 3 mounting the usual automatic choke control mechanism 4. Within the primary mixture conduits 5 is a choke valve 6 and a pair of primary throttles 7, one of which is shown. The secondary barrels 8, one of which is shown, mount a pair of unbalanced throttles 9 eccentrically mounted with respect to a common'throttle shaft 10. The primary barrels 5 and secondary barrels 8 contain the usual main fuel nozzles and, in addition, idle ports adjacent the edge of the primary and secondary throttles arranged as shown in phantom lines in Figs. 1 and 2.

The throttles 7 mounted on throttle shaft 11 are adapted to be opened manually through a lever 12 indicated in Fig. 3, and closed by throttle return spring 16. The lever 12, in turn, operates a push rod 13 and an arm 14 on countershaft 15 connected with the metering Valves and/or the accelerating pump of the carburetor.

Returning to Fig. 1, primary throttle shaft 11 carries a. fixed arm 17 connected by a link 18 with a figure 8 shaped lever member 19 fixed on secondary throttle shaft 10. Slot 22 in lever member 19 receives the connecting rod 18.

The upper lobe of the lever 19 is slotted as at 24 to receive one end of the link 25 connecting with a suction motor 26. Within the motor is a spring 27 biased between the end of the casing and a diaphragm 28 operating plunger 29. A suitable vent 30 allows atmospheric pressure to act on one side of the diaphragm 28, and passage 31 connects the opposite side to the mixture conduit 8 posterior of the secondary throttle 9.

The vent 30 is controlled by a spring-pressed check valve 54 which has a metered bleed port 55 which will restrict the exhaust flow from the chamber to the right of the diaphragm 28. Inflow of air is unrestricted be cause valve 54 opens.

The side of the carburetor carries a pivoted latch 33 having a dog 34 cooperating with a shoulder 35 on the figure 8 lever 19. The tapered end 36 of latch 33 is positioned to be engaged by the end of the plunger 29 to release the latch 33 from shoulder 35.

As shown in Fig. 3, the opposite end of the secondary throttle shaft 10 carries a weighted lever 40 for resisting the opening movement of the secondary throttles 9. On the lever 40 is a dog 41 engaged by a latch bar 42. Shaft 43 rotatably mounts a weighted lever 44 having a fast idle cam 45 engaged by the idle adjusting screw 46 on the lever 12. The shaft 43 also carries a lever 48 connected to the automatic choke valve 6 by a link 49. A lug 50 on lever 48 abuts one side of the weighted lever 44. Opposite lug 50, but on lever 44, is an inturned lug 51 engaging underneath the pivoted latch 42.

the action of the secondary throttle until the automatic choke is fully open. The specific type of lock-out shown is merely another form for accomplishing the same purpose already disclosed in the patent to Carlson et al. 2,715,522 of August 16, 1955. During operation of the automatic choke, the choke valve 6 is positioned to restrict the flow of air through the primary mixture conduits 5. For example, in the position shown in Fig. 3,

when the choke valve is fully closed, lever 48 is rotated counter-clockwise by link 49, and this motion is transmitted to weighted lever 44 by the lug 50 so as to move the fast idle cam 45 into engagement with the idle adjusting screw 46. At the same time, the counter-clockwise movement of the lever 44 engages lug 51 with latch 42, lifting the latch so that it Will engage behind the lug 41 on lever 40 to hold the secondary throttles 9 closed.

Latch 42 can be disengaged from lug 41, freeing the secondary throttles by opening movement of the choke valve 6, which allows the weighted lever 44 to rotate clockwise and lower the latch 42. The same result can be accomplished for unloading by full opening movestarts and warm-up conditions, engine operation will be on the primary stages only, unless the primary throttle is fully depressed for unloading or for maximum acceleration. In the latter case, the excessively rich mixture from the primary stages, due to high engine speed, will compensate for the leaner mixture from the secondary 1 stages so as to provide a suitable total mixture to operate the engine.

During hot starts, when the choke valve is fully opened, both latches 33 and 42 will be released because, in the absence, of choke operation, latch 42 is in its lowered position, and the absence of manifold suction causes the motor 26 to release, the latch 33. When the engine is cranked with both latches 33 and 42 released, weighted lever 40 will retain the secondary stages closed until the engine starts, especially if the primary throttles are opened to proper position tov start. Of course, after it starts, sufiicient suction will immediately build up to operate the suction motor 26 and pull the secondaries closed, so, that the latch 33 drops into engagement with the shoulder 35.

With the parts in the abovementioned condition, operation of the engine will be on the primary stages only until the primary throttles are opened far enough to reduce the manifold pressure to below six inches of mercury suction. When this occurs, spring 27 expands and releases the latch 33, so that the secondary throttles can come into operation. The advantage of using the latch in combination with the suction motor 26 is that the secondary throttles will be, maintained securely closed regardless of the closing force applied by the suction motor 26. It will be realized that, as manifold suction decreases, the force exerted by the suction motor 26 also decreases, and, where unbalanced throttles are used alone, the force of suction acting thereon can overcome the closing force applied by motor 26 to produce an opening sufiicient to partially open the secondaries and allow air leakage at the transition point from primary to secondary operation. The use of the latch prevents this partial opening of the secondaries and surging of the engine, since, by using the latch, the secondaries are either locked out of operation or functioning strongly. There is no intermediate stage where they become a source of air leakage.

The suction motor 26 is constructed to respond to any suction greater than approximately sixinches of mercury to compress the spring 27 and pull the secondary throttles closed. Conversely, at values of suction less than six inches of mercury, the spring 27 will expand toward its full extent, at a slow rate permitted by the bleed 5S, moving the plunger 29 to the right. The relation between the plunger 29 and the latch 33 is such as to lift the latch on movement of the plunger 29 to the right as illustrated in Fig. 2. The release of the latch 33 permits the secondary throttles to come into operation, since the weighted lever 40 imposes less resistance to opening than the suction motor. The degree of opening will correspond to the position of the primary throttles, due to the interconnecting link 18. The degree of resistance offered by the weights 40 to secondary throttle opening is sufficient to require a manifold suction in the range of one to one-andone-half inches of mercury, so that the initial velocity flow through the secondaries will cause full operation.

From the above description, it will be readily recognized that this throttle control mechanism includes a mechanical connection between the primary and the secondary throttles which can close the secondary thottles on closing action of the primary throttles when the engine is stopped, or open the secondary throttles a certain small amount on full opening movement of the primary throttles. This amount can be regulated by adjusting the length of the link 18. In elfect, the primary throttle, therefore, forms a limiting means for the range of operating positions of the secondary throttles.

The movement of the secondary throttles within this range or ranges established by the primary throttles is in turn controlled by two opposing forces. One of these control forces is applied by the suction motor 26, which acts in a closing direction on the secondary throttles 9. The other of these forces is the effect of suction acting directly on the secondary throttles 9 opposed by the weighted lever 40.

It is possible with this system to mechanically open the secondary throttles by opening the primary throttles widev open, and this action is independent of the degree of suction acting directly on the secondary throttles when unlatched.

For example, suppose that the lowest engine speed at wide-open throttle, with a particular transmission, is in the range from 2000 to 3000 engine R. P. M., and maximum engine torque is desired in this range. Under test conditions, engine speed may be held constant within this range with the primary throttles wide open. The secondary throttles may then be manually adjusted to determine their open position for maximum torque output, and link 18 adjusted for mechanical operation of the secondary throttles to this open position. This insures the throttle setting for best performance regardless of suction, which, at this speed, may not be suflicient to open the throttles against the resistance of weight 40.

Conversely, if suction acts to open the secondary throttles too far at this speed, the link 18 may be adjusted to limit the open position of the secondary throttles to a range which will produce maximum engine torque.

With this mechanism, maximum opening of the secondary throttles is positively controlled by the amount of opening of the primaries by link 18 engaging the right end of slot 22, so that a precise speed control may be maintained when the secondary valves are operated by suction.

In the range of secondary operation permitted by the mechanical hook-up between the throttles, secondary throttle position may be regulated so that opening will not take place until added carburetor capacity is necessary, while, at the same time, the same mechanism will eliminate the operation of the secondaries when not needed. In addition, the degree of secondary throttle opening, when needed, will depend upon the action of suction and velocity upon the secondary valves themselves, so that engine performance is benefited by a variable carburetor capacity within the range of velocity and pressure drop necessary to produce satisfactory operation of the carburetor.

The use of this control system eliminates the necessity for two throttle valves, one mechanically operated and one suction operated, in each Secondary, as heretofore thought necessary.

Only one embodiment of the invention has been disclosed and described, but it is obvious that modifications will appear to those skilled in the art which come within the terms of the appended claims.

I claim:

1. In a multi-stage, multi-barrel carburetor having the combination of primary and secondary mixture conduits, a manually controlled primarythrottle valve in said primary mixture conduit, a secondary throttle valve in said secondary mixture conduit, and control mechanism for said secondary throttle valve comprising a mechanism connected between said throttle valves variably limiting the range of permissible movement of said secondary throttle valve in accordance with open positions of said primary throttle valve, and a control coacting with said mechanism for regulating the position of said secondary throttle valve within said range, including suction means for applying increasing closing forces to said secondary valve responsive to an increase in manifold suction.

2. In a multi-stage, multi-barrel carburetor, the combination of primary and secondary mixture conduits, a manually controlled primary throttle valve in said primary mixture conduit, a secondary throttle valve in said secondary mixture conduit, and control mechanism for said secondary throttle valve comprising a mechanical linkage connection between said throttle valves for positively closing said secondary throttle valve responsive to closing of said primary valve and for variably limiting the range of permissible movement of said secondary throttle valve in accordance with open positions of said primary throttle valve, latch means for holding said secondary throttle valve in closed position at low engine speeds and loads, and a control device for regulating the position of said secondary throttle valve within said range including means to release said latch, and suction means to apply increasing forces to close said secondary valves responsive to increases in manifold suction.

3. In a multi-stage, multi-barrel carburetor, the combination of primary and secondary mixture conduits, a manually controlled primary throttle valve in said primary mixture conduit, an unbalanced secondary throttle valve in said secondary mixture conduit, and a control mechanism for said secondary throttle valve comprising a mechanical linkage between said throttle valve variably limiting the range of permissible movement of said secondary throttle valve in accordance with open positions of said primary throttle valve, and a control device for regulating the position of said secondary throttle valve within said range including a suction motor operated by an increase in manifold suction to close said secondary throttle valve, resilient means opposing the action of said suction motor, a lost motion connection between said suction motor and said secondary throttle, means for yieldingly resisting opening movement of said secondary throttle valve, and a latch member to hold said secondary throttle in closed position, said resilient means being operative to release said latch.

4. In a multi-stage, multi-barrel carburetor, the combination of primary and secondary mixture conduits, a manually controlled primary throttle valve mounted on a throttle shaft in said primary mixture conduit, a secondary throttle valve mounted eccentrically with respect to a throttle shaft journaled in said secondary mixture conduit, and control mechanism for said secondary throttle valve comprising a figure 8 cam on said secondary throttle shaft having a pair of opposite slotted lobes, a mechanical linkage secured to said primary throttle shaft and received by one of said lobes for variably limiting the range of permissible movement of said secondary throttle valve in accordance with open positions of said primary throttle valve, a suction motor having a linkage connection with the other of said lobes, a diaphragm in said suction motor exposed on one side to atmospheric pressure, and on the other side to suction posterior of the throttles, resilient means for opposing the action of suction of said diaphragm, means for yieldably resisting the action of suction on said secondary throttle valve, a latch engaging said figure 8 cam in the closed posi tion of said secondary throttle valve, and means for controlling the rate of operation of said resilient means when suction acting on said diaphragm decreases.

5. In a multi-stage, multi-barrel carburetor having the combination of primary and secondary mixture conduits, a manually controlled primary throttle valve in said primary mixture conduit, an unbalanced secondary throttle valve in said secondary mixture conduit, and control mechanism for said secondary throttle valve comprising a mechanism connected between said throttle valves variably limiting the range of permissible movement of said secondary throttle valve in accordance with open positions of said primary throttle valve, and a control coacting with said mechanism for regulating the position of said secondary throttle valve within said range, including suction means for applying increasing closing forces to said secondary valve responsive to an increase in manifold suction.

6. In a multi-stage, multi-barrel carburetor having the combination of primary and secondary mixture conduits, a manually controlled primary throttle valve in said primary mixture conduit, an unbalanced secondary throttle valve in said secondary mixture conduit, and control mechanism for said secondary throttle valve comprising a mechanism connected between said throttle valves variably limiting the range of permissible movement of said secondary throttle valve in accordance with open positions of said primary throttle valve, a control coacting with said mechanism for regulating the position of said secondary throttle valve within said range, including suction means for applying increasing closing forces to said secondary valve responsive to an increase in manifold suction, and resilient means yieldably resisting movement of said suction means in closing said secondary valve.

7. In a multi-stage, multi-barrel carburetor having the combination of primary and secondary mixture conduits, a manually controlled primary throttle valve in said primary mixture conduit, an unbalanced secondarythrottle valve in said secondary mixture conduit, and control mechanism for said secondary throttle valve comprising a mechanism connected between said throttle valves variably limiting the range of permissible movement of said secondary throttle valve in accordance with open positions of said primary throttle valve, a control coacting with said mechanism for regulating the position of said secondary throttle valve within said range, including suction means for applying increasing closing forces to said secondary valve responsive to an increase in manifold suction, and resilient means yieldably resisting movement of said suction means in closing said secondary valve, a latch resisting movement of said secondary valve from its closed position, said latch being released by means actuated by said resilient means.

8. In a multi-stage carburetor, primary and secondary mixing conduits, a manually operable primary throttle valve in said primary conduit, an unbalanced secondary throttle valve in said secondary conduit, two latches engaging said secondary valve in its closed position, one means responsive to a decrease in manifold suction for releasing one of said latches, and means responsive to full opening movement of said primary valve for releasing the other of said latches for unloading, said one means being responsive to an increase in manifold suction for urging said secondary valve toward its closed position.

9. In a multi-stage carburetor, primary and secondary mixing conduits, a manually operable primary throttle valve in said primary conduit, an unbalanced secondary throttle valve in said secondary conduit, two latches engaging said secondary valve in its closed position, one means responsive to a decrease in manifold suction for releasing one of said latches, and means responsive to full opening movement ofsaid primary valve for releasing the other of said latchesfor unloading,sa'id one means being responsive to an increase in manifold suction for urging said secondary valve toward its closed position, means providing a lost-motion connection between said primary and secondary valves limiting movements of the latter.

10. In a multi-stage carburetonprimary and secondary mixing conduits, a manually operable primary throttle valve in said primary conduit, an unbalanced secondary throttle valve in said secondary conduit, two latches engaging said secondary valve in its closed position, one means responsive to a decrease in manifold suction for releasing one ofsaid latches, means responsive to full opening movement of said primary valve for releasing the other of said latches for unloading, said one means being responsive to an increase in manifold suction for urging said secondary valve toward its closed position, means providing a lost-motion connection between said primary and secondary valves limiting movements of the latter, and means providing another lost-motion connection between the secondary valve and said suction motor.

11. In a multi-stage carburetor, primary and secondary conduits, a primary throttle valve in said primary conduit, an unbalanced secondary throttle valve in said secondary conduit, a suction motor means operative respon- 8 sive to :an increase inumanifold suction to urge said secondary valveztowardyits closed position, and a lostmotion connection variably positioned responsive to movementsaoft said primary valve for limiting movements ofi-said suction motorxmeans.

'12; In a two-stagencarburetor system, primary and secondary mixture conduits, :amanual throttle in said primary conduit and an automatic throttle in said secondaryzcon'duit, said secondary throttle being unbalanced so as 'tobe: urgedsropenlbyrdifferential pressures applied thereto during operationpawne-way mechanism between saidthrottles foriclosing said secondary throttle when said primarylthrottle'ris closed and for limiting opening of'said secondarythrottle inaccordance-with the position of said; primaryithrottle, a-latch for cooperating with said secondarythrottle when closed to restrain opening there- 0f, and means'responsiveto 'a'predetermined drop in intake manifold suctionbelow normal idling suction to releasesaid latch.

' References Citdin-thefileof this patent -;UNI'FED STATES PATENTS 2,293,842 Mallory Aug. 25, 1942 2,420,925 Wirth 'May 20, 1947 2,609,187 Scott Sept. 2, 1952 2,752,133 Egerer June 26, 1956

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