US 2183636 A
Description (OCR text may contain errors)
Dec. 19, 1939. R. G. BERRY CARBURETOR MECHANISM Filed May 28, 1957 If 'ENTOR. 2055544 6. EASEEY ATTORNEY.
Patented Dec. 19, 1939 UNITED STATES PATENT orrrer:
Application May 28, 1937, Serial No. 145,239
This invention relates to carburetors for internal combustion engines and consists particularly in novel accelerating pump mechanism and throttle retarding means therefor.
Carburetor accelerating pumps, particularly of the type utilizing flexible piston material, are frequently subject to the defect or disadvantage that excessive quantities of air pass the piston during rapid charging strokes thereof, which air may be forced into the mixture conduit so as to improperly dilute the accelerating charge Also, particularly where the piston material has become worn or is otherwise defective, fuel in the pump cylinder may leak past the piston during rapid discharge with the result that the accelerating charge is inadequate.
In addition to the accelerating pump, carburetors for automobile engines are frequently provided with dash pot mechanism for retarding at least a portion of the closing movement of the 2 throttle so as to prevent unpleasantness due to too rapid deceleration. Heretofore the dash pot has not been combined with the accelerating pump, so far as applicant is aware.
An object of the present invention is to provide novel means for substantially reducing or eliminating the accelerating pump defects mentioned above due to leakage of air and liquid fuel past the accelerating pump piston.
3 Another object is to provide means for insuring continued discharge from the accelerating pump after effective rapid discharge movement of the pump piston.
Another object is to provide novel structure for V retarding closing movement of the throttle.
Still another object is to provide accelerating pump and throttle retarding mechanism in a compact, jointly operated unit.
These objects and other more detailed objects hereafter appearing are attained by the structure illustrated in the accompanying drawing in which Figure 1 is a vertical sectional view of a carburetor embodying the invention, and
Figures 2, 3 and 4 are detail sectional views showing operative parts in different positions.
The carburetor shown has a downdraft mixture conduit including air inlet horn l, venturis 2. mixing chamber 3 and outlet portion 4 flanged as at 5 for attachment to the intake manifold (not shown) of an associated internal combustion engine. A choke valve 6 is pivotally mounted in the air horn and throttle valve is carried by shaft 8, near the outlet portion of the carburetor. Adjacent the mixture conduit is a bowl 9 within which fuel is maintained at a substantially constant level by the usual needle valve mechanism (not shown).
Also within the main fuel chamber or bowl 9 is an accelerating pump cylinder Ill and an auxiliary chamber ll having vents Ella and lid to the air space at the top of the fuel bowl which is substantially at atmospheric pressure. Piston H2 in pump cylinder It has leather cylinder-engaging structure I3 and is connected by means of piston rod l4, rock lever l5, and link 15 to a crank l! rigid with throttle valve shaft 8. During closing movement of the throttle valve, piston I2 is moved upwardly drawing fuel from the bowl into the pump cylinder through passages 18 and I0 and past inlet check 20. During opening of the throttle, piston 12 is moved downwardly, oompressing coiled spring 2! and forcing an accelerating charge past outlet check 22 and through noz- Zle 23 into the mixture conduit adjacent venturis 2.
Auxiliary chamber H communicates with the pump cylinder through a passage 24. Slidable within chamber l l is a plunger 25 normally maintained in an intermediate rest position in the chamber by opposing coiled springs and 2?. Chamber ll does not communicate with the fuel bowl except through passage 24, I8, and IS.
The operation of the device is as follows:
Figure 1 shows the throttle valve closed with pump piston !2 in charged position and plunger 25 at rest. Opening of the throttle valve to the position shown in Fig. 2 moves piston l2 downwardly expelling an accelerating charge into the mixture conduit through passage 9 and nozzle 22. A portion of the fuel in the pump chamber will also be directed through passage 24 into the auxiliary chamber I! so as to force plunger 25 upwardly, compressing coiled spring 2i, as shown. The portion of the accelerating charge by-passed into the auxiliary chamber depends on the rapidity of the discharging stroke of piston l2 and the relationship between the resistance in the bypass and the regular discharge passages. These passages are preferably constructed so that when the throttle is opened slowly, very little additional fuel will pass into the auxiliary chamber. In case of rapid pump dischar e, a substantially greater quantity of fuel will be stored in the auxiliary chamber. At the end of the effective accelcrating stroke of piston l2, spring 27 will expand, again moving plunger 25 to the rest position, as shown in Figure 3, this movement of the plunger continuing the discharge through accelerating nozzle 23.
When plunger 25 is at rest, the fuel in the bowl and the plunger are both exposed to atmospheric pressure. Assuming inlet passages I8 and I9 and passage 24 are of comparable sizes, during charging of the pump, fuel will be drawn more readily into the pump cylinder through the inlet passages than through passage 24. A somewhat similar effect, in this respect, may be obtained by making passage 24 smaller than passage 19. Thus if the charging movement of the piston is slow, the usual intake passages will be adequate to keep the pump chamber filled and very little, if any, fuel will be drawn from the auxiliary chamber through passage Zd. However, if the throttle is closed rapidly, as when it is released to be closed by the usual throttle return spring (not shown), a portion of the pump charge will be supplied from the auxiliary chamber, thus reducing the pressure beneath plunger 25 and causing the same to move downwardly under the influence of coiled spring 21. Immediately at the termination of the charging stroke of piston i2, plunger 25 is returned to its rest position by spring 26 drawing a new charge into the aum'liary chamber through passages 24,
I9, and I3 and past the inlet check valve.
Atmospheric pressure above plunger 25 functions to force the same downwardly when the pressure therebeneath is reduced during rapid charging strokes of the pump piston. The resistance of spring 26 to such movement of the plunger increases and also the expansiveforce of spring 2'! increases as the plunger is depressed and this, in turn, progressively reduces the supply of fuel charge to the pump cylinder from the auxiliary chamber. Thus comparatively little resistance will be offered to movement of the pumping piston during the first part of the rapid charging stroke thereof but this resistance becomes substantial during the last part of such movement. This is due to the fact that charging fuel is supplied to the pump cylinder substantially less freely When plunger 25 has been depressed permitting substantial reduction of, the pressure beneath the pump piston so that during the last part of the charging stroke, the pump functions as a dash pot.
The expansible feature of chamber H substantially reduces the likelihood of fuel leaking past the pump leather during the discharging movement of the piston. Obviously, the accelerating system, including the auxiliary chamber, must be calibrated to provide the proper accelerating charge. Due to the provision of the expansible auxiliary chamber, the pump discharge Will be substantially more uniform than where no such chamber is provided and the efiiciency of the pump leather alone is relied upon to maintain uniformity of the charge. The resiliently contractible feature of the auxiliary chamber functions efiectively to provide for more uniform charging of the pump cylinder during closing of the throttle and also to retard the last portion of the closing movement of the throttle when spring 26 has been substantially compressed.
Various features of the carburetor and accelerating pump system are well known in the art and, in themselves, do not constitute the present invention. Also various features of the invention may be used exclusively of others such for instance, as the contractible and expansible auxiliary chamber features. The exclusive use of all such modifications as come within the scope of the appended claims is contemplated.
1. In a carburetor, a main fuel chamber, an accelerating pump comprising a cylinder having a restricted communication with said chamber and a piston therein, a restricted outlet nozzle for said pump, an auxiliary cylinder communieating with said pump cylinder, a plunger in said auxiliary cylinder, and opposing springs normally maintaining said plunger in an intermediate rest position in said auxiliary cylinder, said plunger and auxiliary cylinder forming a resilientlyexpansible chamber for receiving a part of the normal pump discharge and for producing a delayed discharge therefrom and also forming a contractible chamber for supplying fuel to said pump cylinder during rapid charging movement of said piston.
2. In a carburetor, a throttle, a main fuel reservoir, an accelerating pump including a cylinder and apiston therein exposed to atmosphere and connected to said throttle valve, said cylinder having a restricted inlet communication with said main fuel reservoir, and an auxiliary chamber freely communicating with said pump and having a movable wall normally urged toward and resiliently maintained in a predetermined rest position whenever said piston is at rest regardless of the position thereof, said auxiliary chamber having substantial capacity when said movable wall is in said predetermined rest position whereby said auxiliary chamber may supply part of the charge to said pump when said inlet communication is inadequate to fully supply fuel thereto during rapid charging of the pump.
3. In a carburetor, a main fuel. reservoir, an accelerating pump, including a cylinder and a throttle operated piston, a conduit connecting the pump to said reservoir adequate to charge the pump at a normal rate, a compensating chamber comprising a fuel well, a partition member therein, means normally and resiliently urging the partition into an intermediate position in said well, the space on one side of said partition freely communicating with the pump cylinder whereby abnormally rapid charging movement of the piston is partially satisfied by flow from said Well.
RUSSELL G. BERRY.