Here is a brief introduction to Rexroth gear pumps, to help you get to know them

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The Rexroth gear pump is a rotary pump that transports liquids or increases their pressure by utilizing the changes and movements in the working volume formed between the pump cylinder and the meshing gears. It consists of two gears, a pump body, and front and rear covers, creating two enclosed spaces. As the gears rotate, the volume of the space on the side where the gears are separated decreases and then increases, creating a vacuum that draws in the liquid. Meanwhile, the volume of the space on the side where the gears are in contact decreases, forcing the liquid into the pipeline. The intake chamber and the discharge chamber are separated by the meshing line of two gears. The pressure at the outlet of a gear pump depends entirely on the magnitude of the resistance at the pump outlet. The concept of a gear pump is quite simple: its most basic form consists of two gears of the same size that mesh with each other as they rotate inside a tightly fitting casing. The interior of this casing has an “8” shape, and the two gears are placed within it, with their outer diameters and sides fitting tightly against the casing. The material coming from the extruder enters between the two gears at the inlet and fills this space; as the gears rotate, it moves along the housing, and is finally discharged when the two gears mesh. In terms of terminology, a gear pump is also known as a positive-displacement device; it functions like a piston inside a cylinder, and as one tooth enters the fluid space occupied by another tooth, the liquid is mechanically forced out. Since liquid is incompressible, the liquid and the tooth cannot occupy the same space at the same time; as a result, the liquid is displaced. Due to the continuous meshing of the teeth, this phenomenon occurs continuously, thereby providing a steady discharge volume at the pump’s outlet; the amount discharged is the same with each rotation of the pump. As the drive shaft rotates continuously, the pump also continuously dispenses fluid. The flow rate of the pump is directly related to its rotational speed. In fact, there is a small amount of fluid loss within the pump, which prevents the pump’s operating efficiency from reaching 100%. This fluid is used to lubricate the bearings and the gears, and it is also impossible for the pump components to fit together without any gaps; as a result, it is not possible to have 100% of the fluid discharged from the outlet. Therefore, some amount of fluid loss is inevitable. However, the pump can still operate well, achieving an efficiency of 93% to 98% for most extruded materials. For fluids whose viscosity or density varies during the process, this pump is not greatly affected. If there is a damper, such as a filter or a restrictor placed on the outlet side, the pump will force the fluid to pass through them. If this damper changes during operation, that is, if the filter becomes dirty or clogged, or if the back pressure of the restrictor increases, the pump will still maintain a constant flow rate until it reaches the mechanical limit of the weakest component in the system (usually a torque limiter is installed). The speed at which a pump can operate is actually limited, and this limitation depends mainly on the process fluid. If oil is being transported, the pump can rotate at high speeds; however, when the fluid is a highly viscous polymer melt, this limitation is significantly reduced. It is very important to force high-viscosity fluids into the two-tooth space on the suction side; if this space is not filled completely, the pump will not be able to deliver a precise flow rate. Therefore, the PV value (pressure × flow rate) is another limiting factor, and it represents a process variable. Due to these limitations, gear pump manufacturers will offer a range of products, namely different specifications and displacements (the volume discharged per rotation). These pumps will be matched to specific application processes to optimize system performance and cost. The gear of the PEP-II pump is integrated with the shaft, and a full-hardening process is employed to achieve a longer service life. “The D-type bearing incorporates a forced lubrication mechanism that allows the polymer to pass over the surface of the bearing and return to the inlet side of the pump, thereby ensuring effective lubrication of the rotating shaft. This property reduces the likelihood of polymer retention and degradation. The precisely machined pump body ensures a precise fit between the \"D\"-type bearing and the gear shaft, preventing the gear shaft from becoming eccentric and thus avoiding gear wear. The Parkool sealing structure, together with the PTFE lip seal, forms a water-cooled seal. This type of seal does not actually make contact with the surface of the shaft; its sealing principle relies on cooling the polymer to a semi-molten state to achieve self-sealing. Rheoseal sealing can also be used; it features counter-rotating helical grooves on the inner surface of the shaft seal, which allow the polymer to be forced back toward the inlet under reverse pressure. For ease of installation, the manufacturer has designed an annular bolt mounting surface to facilitate flange mounting in conjunction with other equipment, which makes the production of cylindrical flanges easier. The PEP-II gear pump is equipped with heating elements that match the pump’s specifications and are available as an option for users, ensuring rapid heating and heat control. Unlike the heating method inside the pump, damage to these components is limited to one plate only, and it has no impact on the entire pump.