Positive displacement pump systems

Description

[0001] This invention relates to positive displacement pump systems and is more particularly concerned with such systems in which deliveries from two positive displacement pump sources are available to be fed to a common supply passage.

[0002] According to this invention there is provided a positive displacement pump system having first and second delivery passages for pumped fluid, a main discharge passage connected to receive a flow from the first delivery passage and to receive through a non-return valve a flow from the second delivery passage, a control orifice disposed in the main discharge passage at a location to receive the combined said flows, and a control valve for apportioning the flow from the second delivery passage between the main discharge passage and overspill porting and controlling the by-passing of a proportion of the flow from the first delivery passage through the overspill porting, said control valve comprising a valve member slidably mounted in a bore in a valve body, one end of which bore is in communication with the main discharge passage at a location upstream of said control orifice, a spring which is disposed in a spring chamber in the valve body and which urges the valve member towards said one end of the bore, said spring chamber communicating with the main discharge passage at a location downstream of the control orifice, said valve member having a first metering land between said one end of the valve bore and the overspill porting, and a second metering land disposed between the spring chamber and the overspill porting, and the valve body having an annular by-pass port variably obstructed by the second land and connected to the second delivery passage at a location upstream of said non-return valve, the by-pass port and the axial end portion of the second land nearer the overspill porting being so shaped in relation to each other that on movement of the valve member against the spring loading, the communication between the by-pass port and the space in the valve bore at the axial side of the second land nearer said one end of the valve bore is initially at least, less than fully annular as the valve member moves against the spring loading.

[0003] According to a preferred feature of the invention, the overspill porting comprises an annular overspill port extending about the valve bore, and the edge of the overspill port nearer the first land and the end of the first land nearer said one end of the valve bore are so shaped in relation to each other that on movement of the valve member against the spring loading, the communication between the by-pass port and said one end of the valve bore is, initially at least, less than fully annular as the valve member moves against the spring loading.

[0004] The progressive increase in the area of communication towards fully annular communication in these constructions may be achieved by providing peripheral notches in the said end face of the first and/or the second land or otherwise making the periphery of such end face non-circular. Alternatively notches may be cut in axial end edge of the port.

[0005] The invention will now be described in more detail with reference by way of example to the accompanying diagrammatic drawings in which:

Figure 1 shows a positive displacement pump system according to the invention in a low-speed condition,

Figures 2 and 3 respectively show the control valve of the system of Figure 1 in medium speed and high speed conditions respectively,

Figure 4 illustrates a modified arrangement of the control valve, and

Figures 5 and 6 are respectively fragmentary sectional end views on the lines 5-5 and 6-6 of Figure 4.

[0006] Referring first to Figure 1 the system comprises a positive displacement pump 10 and in this instance of the well-known roller type and has two inlet ports 12, 13 and two outlet ports 14, 15 from which the pumped fluid flows into first and second delivery passages 16, 17 respectively. The downstream end of delivery passage 16 is in direct communication with the upstream end of a main discharge passage 18. The downstream end of the second delivery passage 17 communicates with the discharge passage 18 through a non-return valve 19. A discharge orifice 20 is provided in the discharge passage 18.

[0007] The control valve 11 comprises a spool valve member 22 slidably mounted in a bore 24 in a body part 26. One end of the bore 24 opens to the main discharge passage 18 upstream of the orifice 20. The other end of the bore forms a chamber 27 housing a spring 28 which urges the valve member into abutment with a wall of the main discharge passage 18. The chamber 27 communicates through a duct 25 with the passage 18 at a location downstream of the orifice 20 so that the pressure drop across the orifice opposes the force of the spring 28.

[0008] The valve member has first and second lands 29, 30 of which, in the position shown in Figure 1, the former is disposed between the main discharge passage and an annular overspill port 31 in the bore 24. Port 31 communicates through a passage 32 with a passage 33 leading to the inlet port 12. Land 30 is axially spaced from land 29 and, in the position shown in Figure 1, obstructs an annular by-pass port 34 which is in communication with the second delivery passage 17 at a location upstream of the non-return valve 19. The lands 29,30 have in the periphery of their end portions nearer the main discharge passage a number of notches 35, 36 respectively opening to the end face.

[0009] Figure 1 shows the valve in its position in low-speed operation of the pump. The pressure in the main discharge passage is low, and the lands 29 and 30 respectively prevent communication between the discharge passage 18 and the by-pass port 34 respectively and the overspill port 31, so that the whole flow from the second outlet port 15 flows through the non-return valve 19 and joins the flow from the first outlet port 14 in the main discharge passage leading to the point of utilisation. As the pump speed increases, assuming for the moment that the pressure at the downstream side of orifice 20 remains constant, the increase in pressure at the upstream side of the orifice urges the valve member to move against the spring force as shown in Figure 2. As the notches 36 in the end portion of the second land pass the circular edge 34a of the port 34, a flow of fluid through the port to the overspill port 31 occurs which is less than if there were fully annular communication between the port and the bore, so that the flow to the overspill is not greatly affected by ie is less sensitive to, small movements of the valve member on initial opening. An increasing proportion of the flow from the second delivery port 15 is by-passed through the overspill port 34, as the pump speed increases. As the valve member moves rightward the area of communication increases to the position where the plane of the end face passes the edge 34a of the port 34 and communication is then fully annular.

[0010] Up to this point the non-return valve 19 has remained open but at their maximum opening the notches 36 are capable of passing to the overspill port 31 the entire flow from the second delivery passage 17 and when the end face of land 30 moves past the edge 34a, the resulting fall in pressure in the second delivery passage tends to produce a reverse flow through the non-return valve, which causes the valve 19 to close. The next increase in the pump speed causes a sudden and substantial rightward movement of the valve member, which moves notches 35 to a point relative to the edge 31a of overspill port 31 at which the fresh excess of fluid can pass to the overspill port through the notches 35, see Figure 3. This rightward movement of the valve member causes a sharp fall in the pressure in the second delivery passage 17 and a consequent reduction in the power requirement of the pump. Further increases in pump speed move the valve member further rightward permitting increased flow of fluid from the first delivery passage to pass through notches 35 to the overspill port 34.

[0011] Thus, with progressively increasing pump speed, all of the fluid delivered to the second delivery passage is passed at low pressure through the overspill port, and an increasing proportion of the fluid delivered to the first delivery passage is also passed through the overspill port

[0012] In an alternative arrangement illustrated in Figures 4 to 6, the two lands 29, 30 of the valve member have fully planar end faces and notches 37, 38 are instead formed in the axial end faces 31b, 34b of the ports 31, 34 which co-operate with the lands in controlling the opening of the ports. The notches 37, 38 operate in conjunction with the ends of the lands 29, 30 in exactly the same way as the notches 35, 36 operate in conjunction with the edges 31a of the ports in the arrangement of Figure 1.

[0013] The orifice 20 operates to maintain a constant flow to the point of utilisation, and if at any stage of operation, the pressure downstream of the orifice 20 falls, the resulting drop in pressure in chamber 27 causes the valve member to move to increase the amount of fluid passed to the overspill port. Conversely if the pressure downstream of orifice 20 rises, the resulting rise in pressure in chamber 27 causes the valve member to move to reduce the amount of fluid passed to the overspill port.

Claims

1. A positive displacement pump system having first and second delivery passages for pumped fluid, a main discharge passage connected to receive a flow from the first delivery passage and to receive through a non- return valve a flow from the second delivery passage, a control orifice disposed in the main discharge passage at a location to receive the combined said flows, and a control valve for apportioning the flow from the second delivery passage between the main discharge passage and overspill porting and controlling the by-passing of a proportion of the flow from the first delivery passage through the overspill porting, said control valve comprising a valve member slidably mounted in a bore in a valve body, one end of which bore is in communication with the main discharge passage at a location upstream of said control orifice, a spring which is disposed in a spring chamber in the valve body and which urges the valve member towards said one end of the bore, said spring chamber communicating with the main discharge passage at a location downstream of the control orifice, said valve member having a first metering land between said one end of the valve bore and the overspill porting, and a second metering land disposed between the spring chamber and the overspill porting, and the valve body having an annular by-pass port variably obstructed by the second land and connected to the second delivery passage at a location upstream of said non-return valve, the by-pass port and the axial end portion of the second land nearer the overspill porting being so shaped in relation to each other that on movement of the valve member against the spring loading, the communication between the by-pass port and the space in the valve bore at the axial side of the second land nearer said one end of the valve bore is initially at least, less than fully annular as the valve member moves against the spring loading.

2. A pump system as claimed in claim 1, wherein the overspill porting comprises an annular overspill port extending about the valve bore, and the edge of the overspill port nearer the first land and the end of the first land nearer said one end of the valve bore are so shaped in relation to each other that on movement of the valve member against the spring loading, the communication between the by-pass port and said one end of the valve bore is, initially at least, less than fully annular as the valve member moves against the spring loading.

3. A pump system as claimed in claim 2, wherein the peripheries of the said end faces of the first and second lands are non-circular.

4. A pump system as claimed in claim 3, wherein peripheral notches are formed in the said end face of the first and/or second land.

5. A pump system as claimed in claim 2, wherein the notches are formed in the axial end expel of the overspill part and the by-pass part which co-operate with the respective lands.

Ansprüche

1. Verdrängerpumpe-Anlage mit einem ersten und zweiten Ablaufkanal für gepumpte Flüssigkeit, einem Hauptabflußkanal, der zur Aufnahme einer Durchflußmenge von dem ersten Ablaufkanal und zur Aufnahme einer Durchflußmenge von dem zweiten Ablaufkanal über ein Rückschlagventil angeschlossen ist, einer Regulierungsausflußöffnung, die in dem Hauptabflußkanal an einer Stelle zur Aufnahme der vereinten Durchflußmengen angeordnet ist, und einem Regelventil zum Dosieren der Durchflußmenge von dem zweiten Ablaufkanal zwischen dem Hauptabflußkanal und Überlaufkanal und zum Regulieren des Umleitens eines Teiles der Durchflußmenge von dem ersten Ablaufkanal durch den Überlaufkanal, wobei das Regelventil ein Ventilelement umfaßt, das verschiebbar in einer Bohrung in einem Ventilkörper befestigt ist, wobei ein Ende der Bohrung mit dem Hauptabflußkanal an einer Stelle stromaufwärts der Regulierungsausflußöffnung verbunden ist, sowie mit einer Feder, die in einer Federkammer in dem Ventilkörper angeordnet ist und das Ventilelemente zu dem einen Ende der Bohrung vorspannt, wobei die Federkammer mit dem Hauptabflußkanal an einer Stelle stromabwärts der Regulierungsausflußöffnung in Verbindung steht, welches Ventilelement einen ersten Steuerkolben zwischen dem einen Ende der Ventilbohrung und dem Überlaufkanal aufweist sowie einen zweiten Steuerkolben, die zwischen der Federkammer und dem Überlaufkanal angeordnet ist, und der Ventilkörper eine ringförmige Umgehungsöffnung aufweist, die veränderbar durch den zweiten Steuerkolben verschlossen wird und mit dem zweiten Ablaufkanal an einer Stelle stromaufwärts des Rückschlagventils in Verbindung steht, wobei die Umgehungsöffnung und der axiale Endteil des zweiten Steuerkolbens, der dem Überlaufkanal näher liegt, in bezug zueinander so geformt sind, daß bei Bewegung des Ventilelements entgegen der Federbelastung die Verbindung zwischen der Umgehungsöffnung und dem Raum in der Ventilbohrung an der axialen Seite des zweiten Steuerkolbens, die dem einen Ende der Ventilbohrung näher liegt, zumindest anfangs weniger als vollständig ringförmig ist, wenn sich das Ventilelement entgegen der Federbelastung bewegt.

2. Pumpenanlage nach Anspruch 1, wobei der Überlaufkanal eine ringförmige Überlauföffnung umfaßt, die um die Ventilbohrung verläuft, und der Rand der Überlauföffnung, der dem ersten Steuerkolben näher liegt, und das Ende des ersten Steuerkolbens, das dem Ende der Ventilbohrung näher liegt, in bezug zueinander so geformt sind, daß bei Bewegung des Ventilelements entgegen der Federbelastung die Verbindung zwischen der Umgehungsöffnung und dem einen Ende der Ventilbohrung zumindest anfangs weniger als vollständig ringförmig ist, wenn sich das Ventilelement entgegen der Federbelastung bewegt.

3. Pumpenanlage nach Anspruch 2, wobei der Umfang der Endflächen des ersten und zweiten Steuerkolbens nicht kreisförmig ist.

4. Pumpenanlage nach Anspruch 3, wobei in der Endfläche des ersten und/oder zweiten Steuerkolbens Kerben entlang des Umfanges ausgebildet sind.

5. Pumpenanlage nach Anspruch 2, wobei die Kerben in dem axialen Endausgang des Überlaufteils und des Umgehungsteils ausgebildet sind, die mit den entsprechenden Steuerkolben zusammenwirken.

Revendications

1. Système de pompe à déplacement positif ayant un premier et un deuxième passage de refoulement pour le fluide pompé, un passage de refoulement principal couplé pour recevoir un écoulement du premier passage de refoulement et pour recevoir, par l'intermédiaire d'une vanne antiretour, un écoulement du deuxième passage de refoulement, un orifice de commande disposé dans le passage de refoulement principal à un emplacement lui permettant de recevoir lesdits écoulements combinés, et une vanne de réglage pour doser l'écoulement du deuxième passage de refoulement entre le passage de refoulement principal et l'orifice de débordement et pour commander la dérivation d'une partie de l'écoulement du premier passage de refoulement à travers l'orifice de débordement, ladite vanne de réglage comprenant un élément de la vanne monté de façon coulissante à l'intérieur d'un alésage dans le corps de la vanne, une extrémité dudit alésage étant en communication avec le passage de refoulement principal à un endroit en amont dudit orifice de commande, un ressort qui est disposé à l'intérieur d'une chambre à ressort dans le corps de la vanne et qui pousse l'extrémité de la vanne vers ladite extrémité de l'alésage, ladite chambre à ressort communiquant avec le passage de refoulement principal à un endroit en aval de l'orifice de commande, ledit élément de la vanne possédant un premier cordon de mesurage entre ladite extrémité de l'alésage de la vanne et l'orifice de débordement et un deuxième cordon de mesurage disposé entre la chambre à ressort et l'orifice de débordement, et le corps de la vanne possédant un orifice by-pass annulaire obturé de façon variable par le deuxième cordon et relié au deuxième passage de refoulement à un endroit en amont de ladite vanne antiretour, l'orifice by-pass et l'extrémité axiale du deuxième cordon plus proche de l'orifice de débordement possédant l'un par rapport à l'autre une forme telle que, lors d'un déplacement de l'élément de la vanne contre la charge sur le ressort, la communication entre l'orifice by-pass et l'espace à l'intérieur de l'alésage de la vanne du côté axial du deuxième cordon plus proche de ladite extrémité de l'alésage de la vanne est, du moins initialement, moins complètement annulaire à mesure que l'élément de la vanne se déplace contre la charge sur le ressort.

2. Système de pompe selon la revendication 1, caractérisé en ce que l'orifice de débordement comprend un orifice de débordement annulaire qui s'étend autour de l'alésage de la vanne, et le bord de l'orifice de débordement plus proche du premier cordon et l'extrémité du premier cordon plus proche de ladite extrémité de l'alésage de la vanne possédant l'un par rapport à l'autre une forme telle que, lors d'un déplacement de l'élément de la vanne contre la charge sur le ressort, la communication entre l'orifice by-pass et ladite extrémité de l'alésage de la vanne est, du moins initialement, moins complètement annulaire à mesure que l'élément de la vanne se déplace contre la charge sur le ressort.

3. Système de pompe selon la revendication 2, caractérisé en ce que les périphéries desdites faces extrêmes du premier et deuxième cordon sont non circulaires.

4. Système de pompe selon la revendication 3, caractérisé en ce que des trous de coulée périphériques sont façonnés dans ladite face extrême du premier et/ou deuxième cordon.

5. Système de pompe selon la revendication 2, caractérisé en ce que des trous de coulée sont façonnés dans l'extrémité axiale et chassent la partie débordement et la partie by-pass qui coopèrent avec les cordons respectifs.

Drawing