US2779291A - Pump control - Google Patents

Description

Jan. 29, 1957 J. R. ALBRIGHT PUMP CONTROL 2 Sheets-Sheet 1 Filed March 23, 1953 peaougr Flu/0 c/eco/r Int/awful? BZIW nd W Jan. 29, 1957 J. R. ALBRIGHT PUMP CONTROL 2 Sheets-Sheet 2 Filed March 23, 1953 I l nper zfor I United States PatentO PUMP CONTROL John R. Albright, Rockford, Ill., assignor to Geo. D. Roper Corporation, Rockford, Ill., a corporation of Illinois Application March 23, 1953, Serial No. 343,957 3 Claims. Cl. 103-45 This invention relates to a control arrangement for positive displacement'pumps, and particularly to a control arrangement for preventing the continuing build up of execessive pressure in the discharge line leading from the pump following the closing of a valve in that line while the pump continues to operate.

It is an object of this invention to provide a novel and improved control arrangement of greater sensitivity for preventing the continuing build up of excess pressure in the outlet line leading from an hydraulic motor-driven pump following the closing of a shutoif valve in that line while the pump continues to operate.

It is also an object of this invention to provide a novel control arrangement for a hydraulic motor-driven pump which minimizes wear on the pump resulting from excessive pressure conditions at the discharge side of the pump.

, Another object of this invention is to provide a novel control arrangement for a hydraulic motor-driven pump which substantially stops the pump in response to excessive pressure at the discharge side of the pump, which may have been caused by closing a valve in the discharge line leading from the pump.

A further object of this invention is to provide a novel control arrangement for a hydraulic motor-driven pump having provision for limiting the torque developed by the motor'to a value insuflicient to continue driving the pump when an excessive pressure condition prevails at the discharge side of the pump.

Other and further objects and advantages of the present invention will be apparent from the following description of two preferred embodiments thereof, which are shown in the accompanying drawings to illustrate the principles and mode of operation of the present invention.

In the drawings:

a Figure 1 is a schematic view, with parts broken away, showing a control for a single hydraulic motor-driven pump, in accordance with the present invention; and

Figure 2 is a schematic view showing a control for two hydraulic motor-driven pumps having different torques, in accordance with the present invention.

Referring to Fig. 1, there is shown a conventional geartype product pump 10 for pumping product fluid, such as gasoline, from a tank 11. An inlet conduit 12 extends between the tank and the product pump. A shutoff valve 13 of conventional design is located in the outlet conduit 14 leading from the product pump to the point of disposal of the product fluid.

- The hydraulic control circuit for the product pump includes an hydraulic motor 15, which drives the product pump through a suitable mechanical coupling, indicated schematically at 16. For driving the hydraulic motor 15 there is provided an arrangement which includes an hydraulic gear pump 17, which on a tank truck would ordinarily be driven from the power take-01f shaft on the truck. Pump 17 draws oil from a sump 18 through the inlet conduit 19, discharging the oil under pressure through a conduit 20 leading to the inlet of the hydraulic motor 15. The oil entering the motor chamber of hydraulic motor 15 under pressure causes the gears of this motor to turn, to thereby drive the product pump 10. The oil is discharged from the hydraulic motor 15 through a conduit 21 back to the sump 18. A manually operated shutoif valve 22 is provided in the inlet conduit 20 to the hydraulic motor. A bypass conduit 23 extends between the conduits 20 and 21 in the hydraulic control circuit and is provided with a relief valve, indicated generally at 24. This relief valve includes a ball 25 normally biased to its closed position by a coil spring 26. The coil spring 26 exerts a force against the ball 25 for maintaining the latter seated in its closed position when the oil pressure in the inlet conduit 20 is at normal operating pressure, such as 600 pounds per square inch. When this pressure rises a predetermined amount, such as 30 pounds per square inch, the increased pressure unseats ball valve 25 against the force of its spring 26 to dump the oil under excess pressure through bypass conduit 23 back through return conduit 21 to the sump 18.

In systems of this general type, the product pump is edsigned to have a high volumetric displacement for each revolution to handle relatively large volumes, such as 20 to gallons per minute, of product fluid at low pressure, such as 20 pounds per square inch. The hydraulic motor 15 is designed to have a relatively low volumetric displacement for each revolution and thus handles lesser volumes of oil at high pressure, such as 600 pounds per square inch.

, When a predetermined volume of product fluid has been delivered from the tank, 11, the operator quite often closes the valve 13 while the product pump continues to operate, which results in a high pressure in the conduit 14 at the discharge side of the product pump 10 as the positive displacement product pump continues to pump the product fluid. To prevent the further buildup of this excess pressure the common practice is to provide a built-in'relief valve in the product pump which recirculates the product fluid back through the product pump, thereby preventing any further increase in the outlet pressure from the pump, without, however, stopping the product pump. This is disadvantageous because of the excessive temperature at which the product fluid at high pressure is recirculated through the product pump, often causing permanent damage to the product pump. Also, since the product fluid is commonly gasoline, delivered from a fuel .tank truck, it is undesirable to relieve the excess pressure at the discharge side of the pump in this manner.

In other instances the product fluid may be highly viscous material, such as tar or candy, which tends to solidify, especially as its temperature lowers. With such product materials, relief valves in the product circuit often prove ineffective because of becoming clogged or caked with the highly viscous product material. This is also true where the product fluid contains considerable sediment which deposits on the parts of the relief valve and impairs its operation.

In the present invention, the function of preventing any further build up of the excess pressure at the discharge side of the product pump is performed in a novel and advantageous manner by the relief valve 24.

Considering the operation of the relief valve 24 for this purpose, it will be understood that the torque required to drive the product pump is proportional to the fluid pressure at the discharge side of the pump. By shutting valve 13 while the product pump 10 continues to pump the product fluid, this outlet pressure at the product pump increases, thereby increasing the torque required to continue driving the product pump. The torque developed by the hydraulic motor 15 for driving the product pump is proportional to the inlet pressure, at conduit 20, of the hydraulic liquid whichdrives the motor. Therefore, for the motor to continue to drive the product pump, the motor torque must increase, which means that the hydraulic liquid pressure in conduit 20 at the inlet side of the motormustincrease. However, beforetthisinlet pressure to the motor can build up to this value, the relief valve 24 opens, dumping thev excess hydraulic liquidpressure from conduit 20; through bypass conduit 23 and thence back to the sump 18, and the motor 15 can no longer deliver the torque requiredto drive the product pump 10 and the product pump substantially stops. The pump may continue to operate very slowly due to the slippage of the product liquid around the gears of the pump. However, this does not result in anyv continuing build up of pressure at the discharge side of the pump.

Conventional relief valves, such asthe relief valve 24, are arrangedto open at a predetermined pressure higher than that for which they are set to remain closed. As an illustrative. example of one practical embodiment, the relief valve 24 may be designed to open fully at a predetermined pressure differential, such as 30 pounds per square inch. Thus, while spring 26 will maintain the ball 25 seated when the normal oil pressure of 600 pounds per square inch prevails in the conduit 20, when this oil pressure rises to 630 pounds per square inch it will unseat ball 25 against the urging of spring 26. It will be noted that this increase in oil pressure required to open the relief valve 24 represents only a percent pressure rise, so that the relief valve 24 is quite sensitive to an increase in pressure in conduit 20 resulting from the closingof valve 13 in the product fluid circuit. Thus, a 5 percent rise in the pressure in conduit 14 will effect opening of the relief valve and stopping of the product pump. In addition, due to the relatively low gallonage rate in the hydraulic control circuit, the relief valve 24 is of relatively small size and cost. However, if a relief valve operating an even smaller pressure differential, say 20 pounds per square inch, were to be installed in the product fluid circuit to relieve excess pressure at the discharge side of the product pump 10, as is conventional, it would not be aseffective as the relief valve located in the hydraulic control circuit, in accordance with the present invention. Since the product pump normally pumps the product fluid at about 20 pounds per square inch, the 20 pound per square inch increase at the discharge side of the product pump required to open the relief valve thereat would represent a 100 percent pressure increase over the normal operating pressure of the product pump, so that such a conventional arrangement would be considerably less sensitive than the arrangement of the present invention. In addition, such a relief valve in the product fluid circuit would recirculate the product fluid through the product pump at high pressure and temperature. While it would prevent any further build up of the pressure at the discharge side of the product pump, it would not serve to stop the product pumpsubstantially to thereby eliminatethis continuing recirculation of product'fluid through the product pump.

In Fig. 2 there is shown a product pump control in accordance with the present invention for two different product pumps which pump different product fluids. For example, it may be desired to pump two different fuelshaving different viscosities from a tank truck and for this purpose separate pumps for these, fuels are provided, The separate product pumps wand 31 are di iveli alternately from the, reversible hydraulic motor 32 through overrunning clutches 34 and 35 acting between the motor shafts 36, 37 and the pump drive shafts 38, 39, respectively, as described in greater detail in the copending application of Webster R. Batten and Donald Hadden, Serial No. 344,019, filed March 23, 1953, assigned to the same assignee, as the present application. The first product pump is tl is drivenby the hydraulic motor 32 in one direction of .themotor drive to draw product fluid from he. ul tt ns uit 0 nd. Pu a t hr the ssh se conduit 41, a shutoff valve 42 being provided in this dis charge conduit. In this direction of the motor drive the overrunning clutch disconnects the hydraulic motor 32 from driving relation with the second product pump 31, so that this pump does not operate at this time. In the reverse direction of the motor drive the second product pump draws its product fluid from inlet conduit 43 and pumps it through discharge conduit 44, a shutoff valve 45 being provided in this discharge conduit. In this reverse direction of the motor drive the overrunning clutch disconnects the hydraulic motor from driving relation with the first product pump 30, so that this pump does notoperatethen.

For driving the hydraulic motor 32 there is provided an hydraulic pump 47 which draws liquid from the sump 46 and discharges it through a conduit 48 leading to a conventional four-way control valve 49, which is described in detail in the above-mentioned Batten and-.Hadden application. From the control valve 49 the hydraulic liquid may be passed selectively to either of the conduits 50 and51, which lead to opposite sides of the hydraulic motor 32, and back from the motor through the other of these conduits 50, 51 to the return conduit 52 leading back to thesump 46.

Where the productpumps 30 and 31 pump fuels of different viscosities, the torques required to drive these product pumps are different. Therefore, separate relief valve arrangements are provided for each of these product pumps. For this purpose there are provided in the system shown in Fig. 2 a bypass conduit 53 extending from the conduit 50 back to the return conduit 52 and another bypass conduit 54 extending from the conduit 51 back to the return conduit 52. Separate relief valves 55 and-56 are providedzin the respective bypass conduits 53 and 54. When control valve 49 is set to pass hydraulic fluid under pressure from hydraulic pump 47 through conduit 50 to the hydraulic motor 32, the hydraulic motor drives product pump 30 and relief valve 55 serves as a relief valve for this product pump in the same manner asdescribed in connection with the Fig. 1 system. Thus, when shutoff valve 42 at the discharge side of product pump 30 is closed, relief valve 55 opens and causes this product pump to be stopped substantially. The relief valve 55 is arranged to remain closed when the pressure in conduit 50 is no greater than the operating pressure required to drive product pump 30 normally, and to open; when this pressure rises a predetermined amount abovethis normal value.

In likemanner, when control valve 49 is set-to pass hydraulic fluid under pressure from hydraulic pump 47 through conduit 51 to the hydraulic motor 32, thehydraulic motor is driven in the reverse direction and drives the-other product pump 31. At this time the relief valve 56 servesas a relief valve for this product pump, causing this p o u pump o top n e p ns t s i s f he shutoff valve 45. The ,relief valve 56 is arranged to remain closed when the pressure in conduit 51 is no greater than the operating pressure required to drive the product pump 31 in normal fashion, and to open when this pressure in conduit 51 rises a predetermined amount above normal.

While in the foregoing description and the accompanyingdrawings there have been disclosed two specific embodimentsof the present invention, it is to be understood that various modifications, omissions and refinementsmay be adopted-which depart from the described forms of the invention, without departing from the spirit and scope of the present invention.

I claim:

1. In combination, a pair of product pumpscommunicating with separate sources of product fluids for pumping the same, a reversible hydraulic motor coupled to aid; rq u t: umps.= o riv n h me ternat ly epend: ns p hed rec n f hem t i e. a 99 939? hydraulic liquid an. r u i pumpmmun atina ith said source of hydraulic liquid to pump liquid therefrom, conduits communicating with opposite sides of said hydraulic motor, means for selectively passing hydraulic liquid from said pump through either of said conduits to the motor to drive the motor selectively in either direction and for returning liquid through the other of said conduits back to said source of hydraulic liquid, a first bypass conduit communicating between one of said conduits and said source of hydraulic liquid, at first relief valve in said first bypass conduit operative to open in response to excess liquid pressure in said one conduit to relieve said excess liquid pressure back to said source of hydraulic liquid, a second bypass conduit communicating between the other of said conduits and said source of hydraulic liquid, and a second relief valve in said second bypass conduit operative to open in response to excess liquid pressure in said other conduit to relieve said excess liquid pressure back to said source of hydraulic liquid.

2. A pumping system comprising a product circuit, a rotary positive displacement product pump in said circuit for pumping a relatively large volume of product liquid therethrough at low operating pressures, a product pump control apparatus comprising a rotary positive displacement hydraulic motor having a displacement for each revolution which is low ascompared to the displacement for each revolution of said motor, a shaft drivingly connecting said motor to said pump for operating the latter until operating pressure on the motor reaches a preselected relatively high value as compared to the operating pressure of said pump, an hydraulic circuit for supplying fluid under pressure to said motor, said hydraulic circuit including a source of hydraulic fluid, an hydraulic pump connected to said source of hydraulic fluid for withdrawing fluid therefrom, a first conduit connecting said hydraulic pump to said motor for passing fluid under pressure to said motor, a second conduit connecting said motor to said source of hydraulic fluid for returning the fluid from the motor to said source, a pressure relief valve connected to said first and second conduits arranged to begin to open and by-pass fluid when the pressure differential between said first and second conduits reaches said preselected operating pressure for the motor and to open completely and bypass the entire flow from said hydraulic motor when the pressure differential between said first and second conduits reaches a value higher than said preselected operating pressure.

3. A pumping system comprising a product circuit, a rotary positive displacement product pump in said circuit for pumping a relatively large volume of product liquid therethrough at low operating pressure, a product pump control apparatus comprising a rotary positive displacement hydraulic motor, a shaft drivingly connecting said motor to said pump, an hydraulic circuit for supplying fluid under pressure to said motor, said hydraulic circuit including a source of hydraulic fluid, an hydraulic pump connected to said source of fluid for withdrawing fluid therefrom, a first conduit connected to said pump and to said motor for passing fluid under pressure to said motor, a second conduit connecting said motor to said source of fluid for returning the fluid from the motor to the source, a pressure relief valve connected to said first and second conduits operative to begin to open and by-pass fluid therebetween when the pressure differential between said first and second conduits reaches a preselected relatively high value and to open completely and by-pass the entire flow from the hydraulic motor in response to further predetermined use in said pressure differential, said motor having a displacement for each revolution which is low as compared to the displacement for each revolution of the product pump whereby the relief valve begins to open when the operating pressure of the product pump reaches a value proportionately lower than said preselected pressure supplied to said motor and said relief valve completely opens to stop operation of said motor in response to a further pressure use in the product circuit which is proportionately lower than said predetermined use in the hydraulic circuit.

References Cited in the file of this patent UNITED STATES PATENTS 1,044,444 Englesson Nov. 12, 1912 1,141,015 Silvestri May 25, 1915 1,285,819 Smith Nov. 26, 1918 1,976,040 Scott Oct. 9, 1934 2,149,600 Guinard Mar. 7, 1939 2,280,392 Herman et al Apr. 21, 1942 2,411,602 Tweedale Nov. 26, 1946 2,621,608 McIntyre Dec. 16, 1952

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