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| | | Polar Crank | | |
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| | | | | piston to the full forward position at the end of the discharge stroke. As the crank continues to rotate, the angle of the crank causes the connecting rod to pull the crosshead and piston until it reaches the full rearward position at which point the connecting rod has reached the bottom of the rotation cycle. Regardless of the stroke length setting, the top of the rotation cycle always forces the crosshead and the piston to the full forward position at the end of each discharge stroke. This assures complete scavenging of the liquid end during each stroke cycle. The angle of the polar crank can be adjusted in infinite increments | | between zero and maximum stroke for extremely accurate controlled volume pump settings. The Milroyal polar crank drive features: • Maximum capacity ranges between 0.033 GPH (l25mL/hr.) and 2510 GPH depending on frame size, stroking speed, and plunger diameter • Discharge pressures up to 7500 psi • Up to 8 pumps multiplexed and driven by one motor | | |
| | | T. onsidere | | e unique polar crank drive the heart of the Milroyal ries metering pump. It is | | |
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| | | considered the most advanced and reliable variable stroke length drive available in high pressure/high flow industrial duty metering pumps manufacturer. In the polar crank drive, a high speed worm gear reduces the RPM supplied by the motor, and provides the lower RPM to a rotating crank. A connecting rod with spherical bearings on each end links the crank to the crosshead and piston assembly. The worm gear and crank assembly pivots in an arc about the worm shaft center to change stroke length. The piston stroke length is determined by the angle of the assembly. For example, when the pump is at zero stroke, the worm/crank assembly is in a vertical position. (Figure 1) The crank then rotates in a vertical plane and one end of the connecting rod revolves with it. The crosshead and the piston remain stationary because no reciprocating action is produced. When the pump is adjusted full stroke (or maximum capacity), the rotating crank is moved to its maximum angle from the vertical axis. (Figure 2) At the top of the rotation cycle the connecting rod is pushed forward, moving the crosshead and | | |
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| | | Lubricating Oil Relief Valve | | |
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| | | Worm Shaft | | |
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| | | Figure 1 Zero Stroke | | |
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| | | Worm Gear Rotating Crank Lubricating Oil This illustration demonstrating the polar crank at full and zero strokes | | |
| | | Figure 2 \ Suction Full Stroke | | |
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| | | Pressurized Lubrication System | | |
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| | | To achieve a high thrust capacity and extend component life, the Milroyal B and C polar crank drives feature a pressurized lubrication sys- | | tem. This positive oil pressure lubrication ensures long bearing life and permits the Milroyal pump to operate at very high suction and discharge pressures. As the cross-head moves | | crosshead. During the suction (rearward) stroke the lubricant is trapped. It is then forced through the cross-head, into the crosshead connecting rod bearing, through the hollow connecting rod, and finally to the crank connecting rod bearing. By forcing the oil through this path, every moving part is lubricated during every complete cycle of the pump. To reduce the wear of moving parts and extend oil life, a magnetic strainer cleans the oil before it enters the pressurized system. | | |
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| | | Lubricating Oil Relief Valve | | |
| | | Piston | | |
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| | | Worm Shaft | | forward during
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| | | the discharge stroke, oil from the reservoir is drawn up through a ball check into a cavity in the | | |
| | | Worm Gear | | |
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| | | Magnetic Strainer Connect | | |
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