Title:
NONPULSATING FLUID-FLOW PUMP
United States Patent 3809507
Abstract:
A pump incorporating consecutive pairs intercommunicating through channels. One element of the first pair is fixed while the other element of said pair is movable and rigidly connected with one of the elements of the next pair, the other element of which is also movable. The number of such pairs may be more than two. All the movable elements of the pairs of kinematically linked with a shaped cam which sets said elements in motion. The pump is provided with a changeover device for communicating the metering volumes of said pairs.
US Patent References:
FLUID ENGINE
Cross - July 1970 - 3704080
Pump or motor
Rusdell - January 1927 - 1615140
Pump for liquids or hydraulic motor
Rusdell - July 1928 - 1676114
FLUID ENGINE
Cross - July 1970 - 3704080
Pump or motor
Rusdell - January 1927 - 1615140
Pump for liquids or hydraulic motor
Rusdell - July 1928 - 1676114
Application Number:
05/230751
Publication Date:
05/07/1974
Filing Date:
03/01/1972
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
417/259
International Classes:
F04B7/06; F04B9/02; F04B11/00; F04B43/08; F04B7/00; F04B43/00
Field of Search:
417/259,260,262,265,487,488,215
Primary Examiner:
Freeh, William L.
Assistant Examiner:
Gluck, Richard E.
Attorney, Agent or Firm:
Waters, Eric H.
Claims:
1. A nonpulsating fluid-flow pump comprising: first and second consecutive piston-cylinder pairs having metering volumes connected to each other; a liquid inlet channel communicating with at least one of said pairs; channel means communicating the metering volumes of said pairs; one of said pair having a fixed element and a first movable element, said first movable element rigidly connected to one of the elements of the other piston-cylinder pair; said other pair having a second movable element movable relative to said first movable element and adapted to effect a change in the metering volume of said other pair; means communicating the metering volume of said second pair with the metering volume of the first pair, said means forming a channel means selecting device; a flexible pipe communicating the metering volume of said second pair with said inlet channel; profiled cam means kinematically linked with the movable elements of said first and second pairs for moving said elements in a predetermined operative pattern; and a liquid outlet channel connected with the first
2. A pump according to claim 1, comprising rod means interconnecting said profiled cam means with each of said movable elements, rocker means having a free end supporting a roller movable over the cam profile surface, said rod means being articulated to said rocker means, said rocker means being provided with a common support, said support being adjustable along said
3. A pump according to claim 1, said cam profile surface being asymmetrical so as to have a turning angle corresponding to the discharge stroke of the movable elements of said pairs larger than a turning angle corresponding
4. A pump according to claim 1, comprising a pump casing and two pairs of said piston-cylinders, said channel means selecting device being installed on the pump casing so as to ensure parallel hydraulic communication between the metering volumes of said pairs, one of said metering volumes
5. A pump according to claim 1, comprising flexible elements in the form of bellows effecting the operative function of said piston-cylinder pairs.
2. A pump according to claim 1, comprising rod means interconnecting said profiled cam means with each of said movable elements, rocker means having a free end supporting a roller movable over the cam profile surface, said rod means being articulated to said rocker means, said rocker means being provided with a common support, said support being adjustable along said
3. A pump according to claim 1, said cam profile surface being asymmetrical so as to have a turning angle corresponding to the discharge stroke of the movable elements of said pairs larger than a turning angle corresponding
4. A pump according to claim 1, comprising a pump casing and two pairs of said piston-cylinders, said channel means selecting device being installed on the pump casing so as to ensure parallel hydraulic communication between the metering volumes of said pairs, one of said metering volumes
5. A pump according to claim 1, comprising flexible elements in the form of bellows effecting the operative function of said piston-cylinder pairs.
Description:
The present invention relates to fluid-flow pumps with variable metering volumes and more particularly it relates to the nonpulsating fluid-flow pumps.
The present invention can be used most successfully for the supply of small amounts of fluid in the laboratory and pilot plants of chemical research laboratories though it is equally useful in analytical instruments for the delivery of carrier liquids and various reagents as well as for other purposes requiring nonpulsating accurate metering of liquids with stepless delivery control.
Known in the art are the plants for nonpulsating metering of liquids consisting of two metering plunger pumps, distributing cams which actuate the pump plungers, being themselves driven by an electric motor via a stepless speed variator or a step-by-step gearbox.
The profiles of the distributing cams are such that at any given moment of time one of the pump plungers moving at a constant speed forces the liquid from the pump cylinder into the discharge header. As this plunger reaches the end of the discharge stroke, the second plunger instantaneously starts moving while the first one performs a suction stroke.
Each pump in the pumping plant incorporates two valves, suction and discharge ones, or a device for positive switching-over of channels.
The disadvantages of these plants include a large number of valves which impairs considerably the reliability of the plant. Besides, the transient process during switching over of valves results in a momentary reduction or stopping of liquid delivery.
There have been attempts to reduce the number of valves to two and to cancel the effect of the transient processes on their operation by the use of devices (pumps) for non-pulsating delivery of liquid comprising two or more pistons accommodated in cylinders connected in series and communicating through channels closed by a special device where at least one of the pistons always moves uniformly in the direction of fluid-flow and its channel is closed (see, for example, Pat. No. 42-7211 Cl. 63 B13, Japan).
In this device the pistons are located in one common cylinder or in separate cylinders arranged horizontally, one above the other, and communicating through channels. Each piston accommodates a valve actuated by the rods, one at each side of the piston. Another version of the invention disclosed in the above-mentioned patent has valves located on the piston ends and each piston has one rod for connecting it with the drive.
However, this device possesses a number of disadvantages.
One of these lies in a large number of rubbing seals. Thus, each piston has three seals, one on the piston and one on each of the L.H. and R.H. rods. Therefore, in case of three pistons there are nine seals including three inner seals and six seals ensuring pressure tightness of the pump. Such a number of seals which are less reliable than the valve devices is unacceptable.
Actually, this arrangement cannot be used to make a pump for low rates of fluid flow because the valves located inside the pistons limit the reduction of the piston diameters.
Besides, it is different to actuate the pistons since they are practicably inaccessible.
The arrangement of the valves on the piston ends with a view to reducing their diameters and, consequently, the rate of fluid flow as well as the provision of one rod for each piston results in a considerable pulsation of the delivered liquid since it is forced out of the cylinder by the rod. In case of small piston diameters required for low pump capacities, the diameter of the rod becomes so considerable with respect to the piston diameter that the given design becomes totally unacceptable because of heavy pulsation.
It is an object of the present invention to improve the design of pustons and cylinders of the pump.
Another object of the invention is to provide a pump providing convenient connection of drive to pistons without using seals.
Still another object of the present invention is to provide a pump which gives an opportunity to make pistons of extremely small diameters for provision low efficiency of the pump.
This and other objects object is accomplished by providing a nonpulsating fluid-flow pump comprising two or more pistons accommodated in cylinders connected in series and communicating through closing channels wherein at least one of the pistons always moves uniformly in the direction of the fluid flow and its channel is closed in which, according to the invention, the pistons and the cylinders constitute consecutive pairs connected in such a way that one element of the first pair is fixed while the other element of this pair is movable and connected rigidly with one of the elements of the next pair whose other element is also movable so that all the elements of these pairs are moved by a shaped cam with which they are kinematically linked while the metering volume of the closing pair is communicated periodically by a changeover device with the volume of the preceding pair or with the pump suction channel through a flexible pipe.
Such a design gives a possibility of dispensing with the rods located inside the metering volumes, reducing the number of rubbing seals which ensure the tightness of the pump to two or canceling them altogether and providing free access for connecting a drive to the moving elements of the pairs. The consecutive connection of the movable elements ensures an uninterrupted flow of fluid towards the discharge channel, the working strokes of said elements being overlapped.
For smooth control of the pump capacity it is practicable that the shaped cam should be connected with each movable element by means of an articulated rod and a rocker whose free end carries a roller rolling around the cam, all the rockers being provided with a common support installed with a provision for moving along the rockers for changing the ratio of their arms.
To ensure overlapping of the working strokes of the movable elements, the cam profile must be made asymmetrical so that its turning angle corresponding to the discharge stroke of the movable elements would be larger than the turning angle corresponding to the return stroke of said elements.
The design of the pump is substantially simplified if, in case of two working pairs, the channel changeover device is installed on the pump casing in such a way as to ensure parallel hydraulic communication between the metering volumes of said pairs, one of these volumes being in constant communication with the discharge channel of the pump.
This allows the channels in the pistons to be dispensed with which, in turn, enables the pistons to be made of extremely small diameters to ensure low capacities of the pump.
Besides, this improves access to the changeover device and allows it to be made without valves.
The pump design is also simplified if the channel changeover device in the pump consisting of two pairs is of the valveless type, installed on one of the movable elements and is actuated by the movement of said element relative to the fixed element.
It is practicable that in the two-pair pump one of the movable elements of the closing pair should be installed with a provision for turning around its own axis and be provided on the generating surface with a flat which, on turning of the element, would communicate the metering volume of the closing pair alternately with the pump suction channel or with the metering volume of the preceding pair. This simplifies the design of the valveless pump at the same time retaining the continuity of fluid delivery.
In order to cancel completely the rubbing seals, it is practicable that the working pairs (piston-cylinder) should be made in the form of flexible elements such as bellows or membranes. Such a design ensures complete tightness of the pump which becomes particularly important if it is intended to handle toxic and extremely aggressive liquids.
For making the invention more apparent it will now be described in detail by way of examples with reference to the accompanying drawings (in which:
FIG. 1 is a kinematic diagram of the pump according to the invention;
FIG. 1a is a fragmentary view, on an enlarged scale of the cam portion of FIG. 1 in the direction of arrow W;
FIG. 2 shows two piston-cylinder pairs used in the pump illustrated in FIG. 1, sectionalized, with the diagram of motions of the movable elements of these pairs;
FIG. 3 is a section through another version of the piston-cylinder pairs with a valveless changeover device;
FIG. 4 is a section through another version of the changeover device;
FIG. 5 is a section through two piston-cylinder pairs with a different arrangement of the valveless changeover device and the diagrams of motion of the movable elements and of the changeover device;
FIG. 6 is a section through another version of the piston-cylinder pairs showing diagrammatically the motions of the movable elements of said pairs;
FIG. 7 shows a version of the piston-cylinder pairs in the form of bellows;
FIG. 8 shows a version of the piston-cylinder pairs in the form of membranes.
GENERAL DESIGN OF THE PUMP ACCORDING TO THE INVENTION.
The pump comprises two consecutively-connected piston-cylinder pairs 1 and 2 (FIG. 1) and a shaped cam 3 actuating the movable elements of said pairs.
The pair 1 has an outlet channel 4 while the pair 2 has an inlet channel shown by arrow 5.
DETAILED DESCRIPTION OF THE PUMP UNIT.
The pair 1 is constituted by a fixed element 6 (FIG. 2) and a movable element 7, the element 6 serving as a cylinder and the element 7, as a piston. The pair 2 likewise consists of a movable cylinder 8 rigidly connected to a piston 7, and a movable piston 9. The metering volume 10 of the pair 1 communicates with the metering volume 11 of the pair 2 through a channel 12 accommodating a valve 13.
The piston 9 has a channel 14 accommodating a valve 15.
The number of piston-cylinder pairs may be more than two. In this case the piston 9 is connected with the movable element of the next pair just like the piston 7 is connected with the cylinder 8.
In this type of connection the metering volume 11 of the closing pair communicates with the inlet channel 5 (FIG. 1) through a flexible pipe 16.
The cam 3 is connected with the movable elements of the pairs 1 and 2 by rockers 17 and 18, one end of which carries rollers 19 and 20 contacting the profile of the cam 3 at points spaced at 180°as shown in an enlarged scale in FIG. 1a is viewed in the direction of arrow W in FIG. 1. The other ends of the rockers 17 and 18 are articulated to the corresponding rods 21 and 22. The rod 21 is connected to the body of the valve 13 while the rod 22, to that of the valve 15.
The rods 21 and 22 are provided with springs 23 and 24 intended to pull the rockers 17 and 18 to the initial positions after they have been turned by the cam 3.
The rockers 17 and 18 have a common support 25 installed with a provision for moving along the rockers for changing the ratio of their arms.
The cam 3 has an asymmetrical profile so that the cam turning angle corresponding to the discharge stroke of the movable elements 7, 8, and 9 (FIG. 2) is larger than the turning angle corresponding to the return stroke of these elements. The curve I of the cam profile shown in this figure has a sector A--B corresponding to the the discharge stroke and a sector B--C corresponding to the return stroke of said elements.
The mtering volume 11 (FIG. 3) communicates with the metering volume 10 through the flexible pipe 16, the channel changeover device 26 and the outlet channel 4 which provides for the hydraulic communication of the metering volumes 10 and 11 in parallel with the outlet channel 4.
The device 26 is fixed immovably on the pump casing and comprises a movable changeover switch 27 and channels, one of which communicates with the inlet channel 5, the other one with the pump 16 and the third one, with the outlet channel 4.
Shown in FIG. 4 is another version of the channel changeover device 26 incorporating two valves 28 and 29; the valve 28 closes the channel 30 when the volume 11 increases while the valve 29 closes the inlet channel 5 when the liquid is discharged from the volume 11. The volume 10 is in constant communication with the outlet channel 4.
To simplify the design of the pump and promote the reliability of the channel changeover device the latter is made valveless (see FIG. 5) and installed on the interconnected elements 7 and 8 so that the device is shifted by the movement of these elements relative to the immovable element 6. The changeover device comprises a changeover switch 31 which communicates the volume 11 with the volume 10 through the channel 32 or the volume 11 with the inlet channel 5 through the channel 33 and the flexible pipe 16. The upper diagram I in this figure shows the profile curve of the cam 3 similar to that shown in FIG. 2 while the lower diagram II shows the position of the switch 31.
In order to use the movable element of the pairs additionally in the capacity of a channel switch, the movable element 34 (FIG. 6) of the closing pair which functions as a piston is installed with a provision for turning around its own axis. The element 34 is turned by any known method. For example, the element 34 may be connected to an electric indexing motor by means of a suitable shaft or gearing arrangement having one portion or element thereof connected to the element 34 and a cooperative element coupled to an output shaft of the motor. The generating line of this element has a bevelled flat 35 which, on turning of the element, communicates the metering volume 11 with the channel 5 or with the volume 10 through the channel 36.
In this case the preceding pair is constituted by a fixed element 37 functioning as a piston and provided with an outlet channel 4 and a movable element 38 functioning as a common cylinder and provided with a blind partition 39. Shown in this figure is the above-described curve I of the cam profile.
To exclude the rubbing seals used for making the pump pressure tight, the piston-cylinder pairs in the pump are made in the form of flexible elements, e.g. bellows 40 (FIG. 7) or membranes 41 (FIG. 8).
OPERATION OF PUMP
The required capacity of the pump (FIG. 1) is obtained by adjusting the position of the common support 25 by means of, say, a micrometer screw (the micrometer screw and the pump capacity scale are not shown in the figures and not described herein). After starting the drive motor (not shown in FIG. 1) connected with the cam 3, the motion determined by the cam profile is transmitted by the rollers 19 and 20, rockers 17 and 18 and rods 21 and 22 to the movable elements of the pairs 1 and 2. The springs 23 and 24 press the rollers 19 and 20 constantly against the profile of the cam 3 so that all the movable elements repeat precisely the motions set by the outline of this profile. On a change in the volumes of the pairs 1 and 2 the liquid is drawn into the channel 5 and discharged through the outlet channel 4. The movable elements 7 and 8 (FIG. 2) are interconnected and, therefore, move together while the element 9 repeats the same motions but with a 180° shift. The roller 19 moves over the profile of the cam 3 corresponding to the sector A--A 1 of the curve I (from 0° to 90°) (FIG. 2) while the elements 7, 8 move uniformly upward. The valve 13 is closed. The volume 10 is uniformly contracted, ensuring the discharge of the liquid through the channel 4. Meanwhile, the roller 20 (FIG. 1) moves over the profile of the cam 3 corresponding to the sector A II -B of the curve I (180°-270°) (FIG. 2) while the element 9 moves upward at uniform speed.
As the roller 20 reaches the maximum point B of the curve I it stops and starts moving downward owing to its interaction with the cam profile corresponding to the sector B-C (270°-360°) of this curve which will move the piston 9 down and increase the volume 11. The valve 15 will open and the liquid will be sucked in through the inlet channel 5. The roller 19 will continue rolling along the profile of the cam 3 corresponding to the sector A-B of the curve I which means that the elements 7-8 will continue moving upward, the valve 13 will close and the volume 10 will contract uniformly, supplying the liquid through the channel 4. As soon as the roller 20 comes to the point C on the curve I of the cam profile it will resume its uniform movement upward due to its interaction with the profile of the cam 3 corresponding to the sector A--A 1 (0°-90°) of this curve while the roller 19 will continue its movement over the profile of the cam 3 corresponding to the sector A II -B (180°-270°), forcing the liquid out of the volume 10. Meanwhile, the volume 11 remains unchanged due to the upward movement of the elements 7-8 and 9 at a uniform speed. The valve 15 will close under its own weight.
After the roller 19 reaches point B on the curve 1 of the profile it will stop and, interacting with the cam profile corresponding to the sector B-C (270°-360°) of the curve I, will return the elements 7-8 down; the valve 13 will open and the liquid will flow from the volume 11 into the volume 10. Meanwhile, the roller 20 will continue its uniform upward movement interacting with the cam profile corresponding to the sector A 1 -A 2 (90°-180°) of the curve I. In this case the total volume will keep reducing at the former constant speed with the valve 15 closed, ensuring the same delivery of the liquid through the channel 4, the redistribution of the liquid between the volumes 10 and 11 caused by the movement of the elements 7 and 8 exerting no influence on the total volume.
This ensures overlapping of the channel changeover devices (valves), thus eliminating the influence of the transient processes on the uniformity of liquid delivery and increasing the reliability of said changeover devices.
The device shown in FIG. 3 functions similarly to the one described above but in this case the device 26 (FIG. 3) is mounted on the fixed casing of the pump which simplifies the design of the pistons and enables the changeover device to be made without valves. In this case, when the piston 9 moves down and the piston 7 moves up jointly with the cylinder 8, the changeover switch 27 should be in the left position (in the drawing), communicating the volume 11 with the inlet channel 5. The liquid will be uniformly forced out through the outlet channel 4.
When the piston 9 moves upward and the piston 7 and cylinder 8 move jointly down, the changeover switch 27 should be in the right position (in the drawing), communicating the volume 11 with the outlet channel 4.
The liquid forced by the piston 9 from the common volume 10 and 11 flows through the channel 4 upward while the liquid forced out of the volume 11 owing to the downward movement of the cylinder 8 enters the volume 10 which becomes larger due to the joint motion of the piston 7 with the cylinder 8. The volume 10 functions as an accumulator maintaining a uniform rate of liquid flow through the channel 4 at the moments when the volume 11 is disconnected. The movable element 27 is switched over by any suitable actuating device or solenoid (not shown) at the moments when the volume 11 remains unchanged which occurs when all the movable elements 7, 8 and 9 move uniformly upward.
In another version of the device 26 shown in FIG. 4 the pump operates similarly to that shown in FIG. 3.
As the volume 11 becomes larger, the valve 29 opens and connects said volume 11 with the inlet channel 5 for sucking in the liquid. When the volume 11 is unchanging, the valve 29 closes while during a contraction of said volume 11 the liquid will open the valve 28 and flow through the channel 30, partly through the outlet channel 4 and partly into the increasing volume 10.
If a valveless changeover device 26 is installed on the movable element 8 (FIG. 5) which simplifies the design of said device and its drive, the changeover switch 31 which may be a solenoid-actuated slide switch or the like, communicates the contracting volume 11 with the volume 10 through the channel 32 or with the inlet channel 5 through the flexible pipe 16 and channel 33.
As shown by the curves I and II in FIG. 5, the movable elements 7, 8 and 9 move similarly to those shown in FIG. 2. The movement of the switch 31 to the left corresponds to the sector 0°-90° of the curve II while its movement to the right corresponds to the sector 180°-270° of the same curve which ensures uniform nonpulsating delivery of liquid.
The nonpulsating valveless pump shown in FIG. 6 can be used most successfully as a simple and reliable source of uniform liquid flow in various hydraulic systems and in other installations where the handled fluid can ensure lubrication of the matching pairs 37-38 and 38-34.
The operating principle of the pumps shown in FIGS. 7 and 8 does not differ from that of the pump illustrated in FIGS 1 and 2.
An advantage of these designs lies in a complete absence of rubbing seals, in reliable pressure tightness and a considerable simplification of the pump design.
The pumps incorporating flexible elements may have various changeover devices, for example such as shown in FIGS. 3, 4 and 5 which widens considerably the applications of the pump.
The present invention can be used most successfully for the supply of small amounts of fluid in the laboratory and pilot plants of chemical research laboratories though it is equally useful in analytical instruments for the delivery of carrier liquids and various reagents as well as for other purposes requiring nonpulsating accurate metering of liquids with stepless delivery control.
Known in the art are the plants for nonpulsating metering of liquids consisting of two metering plunger pumps, distributing cams which actuate the pump plungers, being themselves driven by an electric motor via a stepless speed variator or a step-by-step gearbox.
The profiles of the distributing cams are such that at any given moment of time one of the pump plungers moving at a constant speed forces the liquid from the pump cylinder into the discharge header. As this plunger reaches the end of the discharge stroke, the second plunger instantaneously starts moving while the first one performs a suction stroke.
Each pump in the pumping plant incorporates two valves, suction and discharge ones, or a device for positive switching-over of channels.
The disadvantages of these plants include a large number of valves which impairs considerably the reliability of the plant. Besides, the transient process during switching over of valves results in a momentary reduction or stopping of liquid delivery.
There have been attempts to reduce the number of valves to two and to cancel the effect of the transient processes on their operation by the use of devices (pumps) for non-pulsating delivery of liquid comprising two or more pistons accommodated in cylinders connected in series and communicating through channels closed by a special device where at least one of the pistons always moves uniformly in the direction of fluid-flow and its channel is closed (see, for example, Pat. No. 42-7211 Cl. 63 B13, Japan).
In this device the pistons are located in one common cylinder or in separate cylinders arranged horizontally, one above the other, and communicating through channels. Each piston accommodates a valve actuated by the rods, one at each side of the piston. Another version of the invention disclosed in the above-mentioned patent has valves located on the piston ends and each piston has one rod for connecting it with the drive.
However, this device possesses a number of disadvantages.
One of these lies in a large number of rubbing seals. Thus, each piston has three seals, one on the piston and one on each of the L.H. and R.H. rods. Therefore, in case of three pistons there are nine seals including three inner seals and six seals ensuring pressure tightness of the pump. Such a number of seals which are less reliable than the valve devices is unacceptable.
Actually, this arrangement cannot be used to make a pump for low rates of fluid flow because the valves located inside the pistons limit the reduction of the piston diameters.
Besides, it is different to actuate the pistons since they are practicably inaccessible.
The arrangement of the valves on the piston ends with a view to reducing their diameters and, consequently, the rate of fluid flow as well as the provision of one rod for each piston results in a considerable pulsation of the delivered liquid since it is forced out of the cylinder by the rod. In case of small piston diameters required for low pump capacities, the diameter of the rod becomes so considerable with respect to the piston diameter that the given design becomes totally unacceptable because of heavy pulsation.
It is an object of the present invention to improve the design of pustons and cylinders of the pump.
Another object of the invention is to provide a pump providing convenient connection of drive to pistons without using seals.
Still another object of the present invention is to provide a pump which gives an opportunity to make pistons of extremely small diameters for provision low efficiency of the pump.
This and other objects object is accomplished by providing a nonpulsating fluid-flow pump comprising two or more pistons accommodated in cylinders connected in series and communicating through closing channels wherein at least one of the pistons always moves uniformly in the direction of the fluid flow and its channel is closed in which, according to the invention, the pistons and the cylinders constitute consecutive pairs connected in such a way that one element of the first pair is fixed while the other element of this pair is movable and connected rigidly with one of the elements of the next pair whose other element is also movable so that all the elements of these pairs are moved by a shaped cam with which they are kinematically linked while the metering volume of the closing pair is communicated periodically by a changeover device with the volume of the preceding pair or with the pump suction channel through a flexible pipe.
Such a design gives a possibility of dispensing with the rods located inside the metering volumes, reducing the number of rubbing seals which ensure the tightness of the pump to two or canceling them altogether and providing free access for connecting a drive to the moving elements of the pairs. The consecutive connection of the movable elements ensures an uninterrupted flow of fluid towards the discharge channel, the working strokes of said elements being overlapped.
For smooth control of the pump capacity it is practicable that the shaped cam should be connected with each movable element by means of an articulated rod and a rocker whose free end carries a roller rolling around the cam, all the rockers being provided with a common support installed with a provision for moving along the rockers for changing the ratio of their arms.
To ensure overlapping of the working strokes of the movable elements, the cam profile must be made asymmetrical so that its turning angle corresponding to the discharge stroke of the movable elements would be larger than the turning angle corresponding to the return stroke of said elements.
The design of the pump is substantially simplified if, in case of two working pairs, the channel changeover device is installed on the pump casing in such a way as to ensure parallel hydraulic communication between the metering volumes of said pairs, one of these volumes being in constant communication with the discharge channel of the pump.
This allows the channels in the pistons to be dispensed with which, in turn, enables the pistons to be made of extremely small diameters to ensure low capacities of the pump.
Besides, this improves access to the changeover device and allows it to be made without valves.
The pump design is also simplified if the channel changeover device in the pump consisting of two pairs is of the valveless type, installed on one of the movable elements and is actuated by the movement of said element relative to the fixed element.
It is practicable that in the two-pair pump one of the movable elements of the closing pair should be installed with a provision for turning around its own axis and be provided on the generating surface with a flat which, on turning of the element, would communicate the metering volume of the closing pair alternately with the pump suction channel or with the metering volume of the preceding pair. This simplifies the design of the valveless pump at the same time retaining the continuity of fluid delivery.
In order to cancel completely the rubbing seals, it is practicable that the working pairs (piston-cylinder) should be made in the form of flexible elements such as bellows or membranes. Such a design ensures complete tightness of the pump which becomes particularly important if it is intended to handle toxic and extremely aggressive liquids.
For making the invention more apparent it will now be described in detail by way of examples with reference to the accompanying drawings (in which:
FIG. 1 is a kinematic diagram of the pump according to the invention;
FIG. 1a is a fragmentary view, on an enlarged scale of the cam portion of FIG. 1 in the direction of arrow W;
FIG. 2 shows two piston-cylinder pairs used in the pump illustrated in FIG. 1, sectionalized, with the diagram of motions of the movable elements of these pairs;
FIG. 3 is a section through another version of the piston-cylinder pairs with a valveless changeover device;
FIG. 4 is a section through another version of the changeover device;
FIG. 5 is a section through two piston-cylinder pairs with a different arrangement of the valveless changeover device and the diagrams of motion of the movable elements and of the changeover device;
FIG. 6 is a section through another version of the piston-cylinder pairs showing diagrammatically the motions of the movable elements of said pairs;
FIG. 7 shows a version of the piston-cylinder pairs in the form of bellows;
FIG. 8 shows a version of the piston-cylinder pairs in the form of membranes.
GENERAL DESIGN OF THE PUMP ACCORDING TO THE INVENTION.
The pump comprises two consecutively-connected piston-cylinder pairs 1 and 2 (FIG. 1) and a shaped cam 3 actuating the movable elements of said pairs.
The pair 1 has an outlet channel 4 while the pair 2 has an inlet channel shown by arrow 5.
DETAILED DESCRIPTION OF THE PUMP UNIT.
The pair 1 is constituted by a fixed element 6 (FIG. 2) and a movable element 7, the element 6 serving as a cylinder and the element 7, as a piston. The pair 2 likewise consists of a movable cylinder 8 rigidly connected to a piston 7, and a movable piston 9. The metering volume 10 of the pair 1 communicates with the metering volume 11 of the pair 2 through a channel 12 accommodating a valve 13.
The piston 9 has a channel 14 accommodating a valve 15.
The number of piston-cylinder pairs may be more than two. In this case the piston 9 is connected with the movable element of the next pair just like the piston 7 is connected with the cylinder 8.
In this type of connection the metering volume 11 of the closing pair communicates with the inlet channel 5 (FIG. 1) through a flexible pipe 16.
The cam 3 is connected with the movable elements of the pairs 1 and 2 by rockers 17 and 18, one end of which carries rollers 19 and 20 contacting the profile of the cam 3 at points spaced at 180°as shown in an enlarged scale in FIG. 1a is viewed in the direction of arrow W in FIG. 1. The other ends of the rockers 17 and 18 are articulated to the corresponding rods 21 and 22. The rod 21 is connected to the body of the valve 13 while the rod 22, to that of the valve 15.
The rods 21 and 22 are provided with springs 23 and 24 intended to pull the rockers 17 and 18 to the initial positions after they have been turned by the cam 3.
The rockers 17 and 18 have a common support 25 installed with a provision for moving along the rockers for changing the ratio of their arms.
The cam 3 has an asymmetrical profile so that the cam turning angle corresponding to the discharge stroke of the movable elements 7, 8, and 9 (FIG. 2) is larger than the turning angle corresponding to the return stroke of these elements. The curve I of the cam profile shown in this figure has a sector A--B corresponding to the the discharge stroke and a sector B--C corresponding to the return stroke of said elements.
The mtering volume 11 (FIG. 3) communicates with the metering volume 10 through the flexible pipe 16, the channel changeover device 26 and the outlet channel 4 which provides for the hydraulic communication of the metering volumes 10 and 11 in parallel with the outlet channel 4.
The device 26 is fixed immovably on the pump casing and comprises a movable changeover switch 27 and channels, one of which communicates with the inlet channel 5, the other one with the pump 16 and the third one, with the outlet channel 4.
Shown in FIG. 4 is another version of the channel changeover device 26 incorporating two valves 28 and 29; the valve 28 closes the channel 30 when the volume 11 increases while the valve 29 closes the inlet channel 5 when the liquid is discharged from the volume 11. The volume 10 is in constant communication with the outlet channel 4.
To simplify the design of the pump and promote the reliability of the channel changeover device the latter is made valveless (see FIG. 5) and installed on the interconnected elements 7 and 8 so that the device is shifted by the movement of these elements relative to the immovable element 6. The changeover device comprises a changeover switch 31 which communicates the volume 11 with the volume 10 through the channel 32 or the volume 11 with the inlet channel 5 through the channel 33 and the flexible pipe 16. The upper diagram I in this figure shows the profile curve of the cam 3 similar to that shown in FIG. 2 while the lower diagram II shows the position of the switch 31.
In order to use the movable element of the pairs additionally in the capacity of a channel switch, the movable element 34 (FIG. 6) of the closing pair which functions as a piston is installed with a provision for turning around its own axis. The element 34 is turned by any known method. For example, the element 34 may be connected to an electric indexing motor by means of a suitable shaft or gearing arrangement having one portion or element thereof connected to the element 34 and a cooperative element coupled to an output shaft of the motor. The generating line of this element has a bevelled flat 35 which, on turning of the element, communicates the metering volume 11 with the channel 5 or with the volume 10 through the channel 36.
In this case the preceding pair is constituted by a fixed element 37 functioning as a piston and provided with an outlet channel 4 and a movable element 38 functioning as a common cylinder and provided with a blind partition 39. Shown in this figure is the above-described curve I of the cam profile.
To exclude the rubbing seals used for making the pump pressure tight, the piston-cylinder pairs in the pump are made in the form of flexible elements, e.g. bellows 40 (FIG. 7) or membranes 41 (FIG. 8).
OPERATION OF PUMP
The required capacity of the pump (FIG. 1) is obtained by adjusting the position of the common support 25 by means of, say, a micrometer screw (the micrometer screw and the pump capacity scale are not shown in the figures and not described herein). After starting the drive motor (not shown in FIG. 1) connected with the cam 3, the motion determined by the cam profile is transmitted by the rollers 19 and 20, rockers 17 and 18 and rods 21 and 22 to the movable elements of the pairs 1 and 2. The springs 23 and 24 press the rollers 19 and 20 constantly against the profile of the cam 3 so that all the movable elements repeat precisely the motions set by the outline of this profile. On a change in the volumes of the pairs 1 and 2 the liquid is drawn into the channel 5 and discharged through the outlet channel 4. The movable elements 7 and 8 (FIG. 2) are interconnected and, therefore, move together while the element 9 repeats the same motions but with a 180° shift. The roller 19 moves over the profile of the cam 3 corresponding to the sector A--A 1 of the curve I (from 0° to 90°) (FIG. 2) while the elements 7, 8 move uniformly upward. The valve 13 is closed. The volume 10 is uniformly contracted, ensuring the discharge of the liquid through the channel 4. Meanwhile, the roller 20 (FIG. 1) moves over the profile of the cam 3 corresponding to the sector A II -B of the curve I (180°-270°) (FIG. 2) while the element 9 moves upward at uniform speed.
As the roller 20 reaches the maximum point B of the curve I it stops and starts moving downward owing to its interaction with the cam profile corresponding to the sector B-C (270°-360°) of this curve which will move the piston 9 down and increase the volume 11. The valve 15 will open and the liquid will be sucked in through the inlet channel 5. The roller 19 will continue rolling along the profile of the cam 3 corresponding to the sector A-B of the curve I which means that the elements 7-8 will continue moving upward, the valve 13 will close and the volume 10 will contract uniformly, supplying the liquid through the channel 4. As soon as the roller 20 comes to the point C on the curve I of the cam profile it will resume its uniform movement upward due to its interaction with the profile of the cam 3 corresponding to the sector A--A 1 (0°-90°) of this curve while the roller 19 will continue its movement over the profile of the cam 3 corresponding to the sector A II -B (180°-270°), forcing the liquid out of the volume 10. Meanwhile, the volume 11 remains unchanged due to the upward movement of the elements 7-8 and 9 at a uniform speed. The valve 15 will close under its own weight.
After the roller 19 reaches point B on the curve 1 of the profile it will stop and, interacting with the cam profile corresponding to the sector B-C (270°-360°) of the curve I, will return the elements 7-8 down; the valve 13 will open and the liquid will flow from the volume 11 into the volume 10. Meanwhile, the roller 20 will continue its uniform upward movement interacting with the cam profile corresponding to the sector A 1 -A 2 (90°-180°) of the curve I. In this case the total volume will keep reducing at the former constant speed with the valve 15 closed, ensuring the same delivery of the liquid through the channel 4, the redistribution of the liquid between the volumes 10 and 11 caused by the movement of the elements 7 and 8 exerting no influence on the total volume.
This ensures overlapping of the channel changeover devices (valves), thus eliminating the influence of the transient processes on the uniformity of liquid delivery and increasing the reliability of said changeover devices.
The device shown in FIG. 3 functions similarly to the one described above but in this case the device 26 (FIG. 3) is mounted on the fixed casing of the pump which simplifies the design of the pistons and enables the changeover device to be made without valves. In this case, when the piston 9 moves down and the piston 7 moves up jointly with the cylinder 8, the changeover switch 27 should be in the left position (in the drawing), communicating the volume 11 with the inlet channel 5. The liquid will be uniformly forced out through the outlet channel 4.
When the piston 9 moves upward and the piston 7 and cylinder 8 move jointly down, the changeover switch 27 should be in the right position (in the drawing), communicating the volume 11 with the outlet channel 4.
The liquid forced by the piston 9 from the common volume 10 and 11 flows through the channel 4 upward while the liquid forced out of the volume 11 owing to the downward movement of the cylinder 8 enters the volume 10 which becomes larger due to the joint motion of the piston 7 with the cylinder 8. The volume 10 functions as an accumulator maintaining a uniform rate of liquid flow through the channel 4 at the moments when the volume 11 is disconnected. The movable element 27 is switched over by any suitable actuating device or solenoid (not shown) at the moments when the volume 11 remains unchanged which occurs when all the movable elements 7, 8 and 9 move uniformly upward.
In another version of the device 26 shown in FIG. 4 the pump operates similarly to that shown in FIG. 3.
As the volume 11 becomes larger, the valve 29 opens and connects said volume 11 with the inlet channel 5 for sucking in the liquid. When the volume 11 is unchanging, the valve 29 closes while during a contraction of said volume 11 the liquid will open the valve 28 and flow through the channel 30, partly through the outlet channel 4 and partly into the increasing volume 10.
If a valveless changeover device 26 is installed on the movable element 8 (FIG. 5) which simplifies the design of said device and its drive, the changeover switch 31 which may be a solenoid-actuated slide switch or the like, communicates the contracting volume 11 with the volume 10 through the channel 32 or with the inlet channel 5 through the flexible pipe 16 and channel 33.
As shown by the curves I and II in FIG. 5, the movable elements 7, 8 and 9 move similarly to those shown in FIG. 2. The movement of the switch 31 to the left corresponds to the sector 0°-90° of the curve II while its movement to the right corresponds to the sector 180°-270° of the same curve which ensures uniform nonpulsating delivery of liquid.
The nonpulsating valveless pump shown in FIG. 6 can be used most successfully as a simple and reliable source of uniform liquid flow in various hydraulic systems and in other installations where the handled fluid can ensure lubrication of the matching pairs 37-38 and 38-34.
The operating principle of the pumps shown in FIGS. 7 and 8 does not differ from that of the pump illustrated in FIGS 1 and 2.
An advantage of these designs lies in a complete absence of rubbing seals, in reliable pressure tightness and a considerable simplification of the pump design.
The pumps incorporating flexible elements may have various changeover devices, for example such as shown in FIGS. 3, 4 and 5 which widens considerably the applications of the pump.