Title:
FEED AND PROPORTIONING PUMP
United States Patent 3765802
Abstract:
A feed and proportioning pump is provided for delivering two different liquids in a given proportion by flow volume, and in particular to a pump for delivering fuel and oil to mixture-lubricated combustion engines, having two interconnected displacement members executing their suction strokes and their feed strokes simultaneously and arranged in special working chambers communicating with a suction and a delivery line by way of reciprocally acting check valves.
Inventors:
Leitermann, Wulf (Wecka1sulm, DT)
Maurhoff, Gerhard (Wecka1sulm, DT)
Application Number:
02/161529
Publication Date:
10/16/1973
Assignee:
Audi NSU Auto Union Aktiengesellschaft (Neckarsulm, DT)
Other Classes:
417/503, 417/521
International Classes:
F01L23/00; F02M1/00; F04B7/00; F04B9/12; F04B43/00; F04B43/073; (IPC1-7): F04B43/06; F04B45/04
Field of Search:
91/47,51 417
Primary Examiner:
Freeh, Wiliam L.
Assistant Examiner:
Winburn, John T.
Claims:
What is claimed is
1. A feed and proportioning pump for delivering two different liquids in a given proportion by flow volume and in particular delivering fuel and oil to a mixture-lubricated combustion engine, having two interconnected displacement members executing their suction strokes simultaneously and their delivery strokes simultaneously and arranged in individual pumping chambers each communicating with a separate suction line and a common delivery line by way of opposing acting check valves, one of said displacement members being a diaphragm and forming a portion of one of said pumping chambers, a motor chamber on the opposite side of said first diaphragm, a second diaphragm connected to the first mentioned diaphragm and dividing the motor chamber into two spaces capable of being connected to a common source of pressure or suction, said two diaphragms having different effective areas, a bistable valve capable of being actuated by the second diaphragm at the end of each stroke of the displacement members, one of the spaces being between the diaphragms and being continuously connected to the source of pressure or suction during operation of the pump, said bistable valve establishing communication of the other space to the source of pressure or suction at the end of one stroke of the displacement members and interrupting such communication and establishing communication of that space with the atmosphere at the end of the counterstroke.
2. A pump according to claim 1 wherein the chamber space between the two diaphragms is in communication with the atmosphere by way of a negative pressure valve.
3. A pump according to claim 1 wherein the chamber space between the two diaphragms is in communication with the source of suction by way of a throttling means.
4. A feed and proportioning pump for delivering two particular liquids in a given proportion by flow volume and in particular delivering fuel and oil to a mixture-lubricated combustion engine, having two interconnected displacement members executing their suction strokes simultaneously and their delivery strokes simultaneously and arranged in individual pumping chambers each communicating with a separate suction line and a common delivery line by way of opposing acting check valves, one of said displacement members being a diaphragm and forming a portion of one of said pumping chambers, a motor chamber on the opposite side of said first diaphragm, a second diaphragm connected to the first mentioned diaphragm and dividing the motor chamber into two spaces capable of being connected to a common source of pressure or suction, one of the spaces being between the diaphragms and being continuously connected to the source of pressure or suction during operation of the pump, said two diaphragms having different effective areas, a U-shaped snap spring attached to the second diaphragm, a bistable valve capable of being actuated by the spring at the end of each stroke of the displacement members, a cam mounted on the bistable valve, the spring having bends directed toward each other near its ends to cooperate with the cam mounted on the bistable valve to move the valve between two positions, said bistable valve establishing communication of the other of said spaces to the source of pressure or suction at the end of one stroke of the displacement members and interrupting such communication and establishing communication of that space with the atmosphere at the end of the counterstroke.
Description:
BACKGROUND OF THE INVENTION opposite
It has previously been proposed for feed and proportioning pumps that one stroke of two displacement members be effected by spring action and the counterstroke by a controlled transmission medium. A control member, actuable by the displacement members, was provided to turn on the supply of transmission medium at the end of the full stroke (effected by spring action) and shut it off at the end of the full counterstroke (effected by the medium). In the practical embodiment of that feed and proportioning pump, the negative pressure in the intake duct of the engine served as the transmission medium. It has now been found that the running of the pump is delayed at starting by the fact that the negative pressure must first overcome the force of the spring, and this requires a certain amount of time for the negative pressure to build up. An analogous situation obtains also if compressed air used as the transmission medium.
SUMMARY OF THE INVENTION
The object of the invention is to improve the feed and proportioning pump of the type specified in such manner as to ensure qucik starting of the pump.
This problem is solved, according to the invention, in that the pump is provided with a chamber having a movable partition dividing the chamber into two parts capable of being connected to a common source of pressure or suction. The partition is, in turn, connected with the displacement members. A bistable valve capable of being actuated by the partition at the end of each complete stroke of the displacement members is also provided for establishing communication of one of the parts of the chamber with the source of pressure or suction at the end of one stroke of the displacement members and interrupting it at the end of the counterstroke.
The pump, according to the invention, will start immediately as soon as pressure or suction prevails in one or both chambers, since to start the pump no spring action need be overcome that would otherwise require a certain pressure or suction build-up.
The movable partition is preferably in the form of a diaphragm. In addition, one of the displacement members may also be advantageously formed by a diaphragm, bounding the working chamber for one of the liquids to be handled on one side and the chamber in which the movable partition is arranged on the other side. Inasmuch as the diaphragm acts as a displacement member, it is required to have a smaller effective area than the diaphragm acting as a partition, in order to get the necessary area differential to bring about the stroke through the suction prevailing in the part of the chamber in question.
If the pump according to the invention is employed as a mixture pump to deliver fuel and oil to the carburetor of a combustion engine, the actuation may occur where at high suctions and low flow volume a comparatively high liquid pressure will be built up, which may cause the float housing to overflow because of failure of the float needle valve to close tightly. To avoid this, the part of the chamber between the two membranes may be connected with the atmosphere by way of a negative pressure valve. This will limit the suction in that part of the chamber, and hence the delivery pressure, to a certain valve. In this instance, in order to avoid excessive loss of suction, it has proven expedient to connect the part of the chamber between the two diaphragms to the source of suction by way of a throttling means.
The other part of the chamber is alternately connected by the bistable valve to the source of suction and to the atmosphere at the end of each full stroke. The bistable position of the valve is produced by a U-shaped snap spring fixed to the diaphragm forming the partition. This spring has bends directed towards each other near its ends to cooperate with the cam attached to the valve. This spring brings the valve to a first position at which communication is established between part of the chamber with the atmosphere; and it shuts off communication with the source of suction at the end of a stroke, holding it in that position until the end of the next stroke, and then it brings the valve into the other position.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the invention will be described below by way of example with reference to the drawings.
FIG. 1 shows a sectional view FIG. a fuel-oil proportioning pump according to the invention, with the valve in one position; and
FIG. 2 repeats a portion of Fig. 1 with the valve in the other position.
In the drawing, a multipartite pump housing 1 has two working chambers 2 and 3. Chamber 2 is bounded by a disphragm 4 connected with a piston 5 displaceable in chamber 3. A fuel supply line 6 closed by a check valve 7 opens into chamber 2. A feed line 8 closed by a second check valve 10 extends from chamber 2 and opens into a mixing chamber 9. An oil line 11 closed by a spring-loaded shut-off valve 12 extends into chamber 3. The feed line 13 of chamber 3 opens into the mixing chamber 9 and is closed by the same check valve 10 as the feed line 8 of chamber 2. Extending from the mixing chamber 9 is a mixture line 14 leading to the float chamber of the carburetor.
The diaphragm 4 cooperates in defining a motor chamber 15 opposite chamber 2. A diaphragm 16 divides motor chamber 15 into two parts 17 and 18 and is advantageously connected with diaphragm 4 and piston 5. Diaphragm 16 has a greater effective area than diaphragm 4.
A suction line 19 communicating with the intake of the combustion engine or with a negative pressure reservoir opens by way of a branch 20 into chamber part 18 and by way of another branch 21 into chamber part 17. Part 17 is capable of being connected to the atmosphere as well as by means of a line 22. Lines 21 and 22 are capable of being shut off alternately by a valve 23 actuated by diaphragm 16 at the end of each of its strokes. For this purpose, a U-shaped snap spring 24 is attached to diaphragm 16, having bends 25 directed towards each other near its ends to cooperate with a cam 26 mounted on valve 23. Cam 26 forms the end stop for valve 23 in one direction, while the end stop in the other direction is formed by a shoulder 27. As shown, cam 26 is in the form of a disc whose periphery is beveled on both sides. Valve 23 has two constrictions 23a and 23b which alternately open line 21 or line 22, as shown in FIGS. 1 and 2.
A passage 28 extends from chamber part 17 and opens into a chamber 29 bounded by a disphragm 30 connected with the shut-off valve 12.
The mode of operation of the pump shown is as follows:
In the position depicted by FIG. 1, diaphragm 4 and piston 5 are at the end of their delivery stroke, which has been effected by the suction in chamber part 18. Part 17, which during this delivery stroke has been in communication with the atmosphere by way of line 22 (see FIG. 2,) is now connected to the negative pressure line 19 by the shift of valve 23. The negative pressure pulls diaphragm 16 downwardly and with it diaphragm 4 and piston 5. Simultaneously, spring 24 is spread by cam 26. Fuel now flows through line 6 and the opened check valve 7 into chamber 2. At the same time, the suction in chamber 29 opens the shut-off valve 12 so that oil can reach chamber 3 by way of line 11. At the end of the down stroke, the bends 25 snap over cam 26, abruptly shifting valve 23 into its other extreme position in which the shoulder 27 is in contact with the housing (FIG. 2). This shuts off passage 21 and opens passage 22, so that the negative pressure now acting in chamber part 18 can move diaphragm 16 upwardly and with it diaphragm 4 and piston 5. At the same time, the shut-off valve 12 is closed by spring action.
The delivery stroke of diaphragm 4 and piston 5 now takes place, and the liquid previously drawn into chambers 2 and 3 is supplied through the opened check valve 10 into mixing chamber 9 and thence through mixture line 14 to the carburetor. If the float needle of the carburetor has shut off the feed line, diaphragm 4 and piston 5 will stop in an intermediate position until the float needle has opened the feed line again, whereupon the delivery stroke will be completed by the suction in chamber part 18. Only at the end of the delivery stroke will valve 23 be forced back by snap spring 24 into the position shown in FIG. 1, thereby shutting off the vent line 22 and opening the negative pressure line 21, so that a complete suction stroke can be executed once more.
In order to avoid the occurrence of too high a delivery pressure, which the float meter cannot withstand and which would flood the float housing, chamber part 18 is conveniently connected to the atmosphere by way of a negative pressure valve 31. This valve 31 limits the maximum suction in chamber part 18 to a certain valve. To avoid excessive loss of suction at high negative pressures, a throttling means 32 is provided in branch line 20.
Thus, the several aforenoted objects and advantages are most effectively attained. Although a single somewhat preferred embodiment has been disclosed and described herein, it should be understood that this invention is in no sense limited thereby and its scope is to be determined by that of the appended claims.