Hydraulic displacement pump having two stroke length

A pump having a short stroke pumping mode and a long stroke pumping modes, the pump comprising:

• first and second cylinders, wherein the first cylinder comprises a first piston driven by hydraulic fluid and the second cylinder comprises a second piston driven by hydraulic fluid;
• a hydraulic pump that supplies hydraulic fluid to the first and second cylinders;
• a diverter valve located between the pump and the first and second cylinders having a first and second position, wherein the first position allows a full flow of hydraulic fluid to the first and second cylinders and the second position allows a lesser flow of hydraulic fluid to the first and second cylinders than the first position;
• and
• a short stroke valve located near the middle of the second cylinder, wherein the short stroke valve is made operational when the diverter valve is in the second position and prevents the pistons from being driven a full length of the cylinders.

A method of operating a dual cylinder displacement pump having both a long stroke mode and a short stroke mode in the short stroke mode, the method comprising:

• providing a flow of hydraulic fluid to a first and second pumping cylinder to actuate them;
• restricting the flow of hydraulic fluid to the first and second pumping cylinder so that about half the full amount of fluid is supplied to the pumping cylinders;
• sensing a position of a piston in the first pumping cylinder at a short stroke position;
• and
• switching the flow of hydraulic fluid from one pumping cylinder to the other pumping cylinder when the piston reaches the short stroke position to allow the pistons to pump at a short stroke mode.

A pump having a short stroke mode and a long stroke mode, the pump comprising:

• first and second material cylinders;
• first and second hydraulic drive cylinders axially aligned with and connected to the material cylinders;
• first and second piston rods comprising hydraulic pistons located in the hydraulic drive cylinders wherein the hydraulic pistons are driven by hydraulic fluid supplied to the hydraulic cylinders;
• and
• a hydraulic valve system for selectively operating the hydraulic pistons in a long stroke mode and a short stroke mode, the hydraulic valve system comprising a diverter valve and a short stroke valve on the first hydraulic cylinder, wherein the short stroke valve senses when the hydraulic piston reaches a short stroke position and the diverter valve diverts about half a flow of hydraulic fluid to the hydraulic drive cylinders so that a shorter stroke is made by the hydraulic piston in the hydraulic drive cylinder.

A pump having a short stroke mode and a long stroke mode, the pump comprising:

• first and second material cylinders;
• first and second hydraulic drive cylinders connected to the material cylinders;
• and a hydraulic valve system comprising:
• a material output valve which connects one material cylinder to an outlet and the other material cylinder to a material hopper. wherein the material output valve changes position so that as material exits one material cylinder at the outlet, material can enter the other material cylinder at the material hopper;
• a pump supplying the hydraulic drive cylinders with the hydraulic fluid;
• a diverter valve located between the pump and the hydraulic drive cylinders for diverting an amount of hydraulic fluid supplied to the hydraulic drive cylinders;
• a reciprocating cylinder valve between the pump and the first and second hydraulic drive cylinders which alternately drives the first and second material cylinders by supplying hydralilic fluid to one of the hydraulic cylinders and allowing fluid to exit from the other of the hydraulic cylinders;
• a short stroke valve located on one hydraulic drive cylinder that signals the material output valve and the reciprocating cylinder valve to change position when the material cylinder reaches a short stroke position;
• and
• a switch having a first position for selecting a long stroke mode and a second position for selecting a short stroke mode, wherein the second position activates the diverter valve and the short stroke valve, so that an amount of fluid supplied to the hydraulic drive cylinders in the short stroke mode is about half an amount of hydraulic fluid supplied to the hydraulic drive cylinders in the long stroke mode.