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Varied groove depth gives early face separation
Patents
Patents Varied groove depth gives early face separation Title: Face seal with angled grooves and shallow annular groove Patent number: US57021 10 Date: 30th December 1997 Inventor: J Sedy Assignee: Durametallic Corp The separation of the faces in a rotary fluid film face seal can be achieved through a shallow spiral groove in one of the faces, ending in a restriction. As the fluid medium enters the groove it meets the restriction, and the resultant build up of oressure seoarates the faces. Fluid can e;ter the spiral groove in Iwo ways. Firstly, the rotation of one of the faces can pump fluid through the groove, known as hydrodynamic force, and secondly, the pressure of the
Figure 1. Groove configuration
Sealing
Technology
No. 50
sealed liquid can also drive it through, separating the faces by hydrostatic pressure. Start-up of the equipment can be problematic to seal operation. When the seal is stationary there are no hydrodynamic forces. If the hydrostatic forces are not sufficient to counter the pressure which keeps the seal faces in contact, then the subsequent fact lock and resulting friction can destroy the seal. The hydrostatic force can be increased by extending the length of the short, deep grooves, which are necessary to generate hydrodynamic forces at full speed, though this leads to excessive leakage during full speed operation. The face seal described here. offers an optimisation of hydrodynamic and hydrostatic sealing characteristics, without causing increased leakage. The design, shown in Figure-l, is based around a combination of two groove arrangements, one (134), significantly deeper than the other (144). The shallow annular G-oove I144). is oreferablv ’ 0.00002 inch to’0.0600< inch. and the deeper groove [134), is 5 to 10 times deeper, approximately 0.0001 inch to 0.0003 inch. The passages (1521, have the same depth as the deeper groove.
allows smoother start-up.
When the seal is slationary, the high pressure fluid surrounding the outer diameter (128), enters into the deep grooves (134), and the shallow grooves (144). but is then restricted from further inward radial flow by a dam (1511. This pressurised fluid is sufficient to generate enough hydrostatic force to separate the faces. As the seal operates at higher rotational speed, the high pressure fluid in the deep grooves (134). is pumped out over the shallow groove region (1X3), and the areas between the grooves (141), forcing the seal faces apart. During operation of the seal, an equilibrium is established between the fluid inflow through spiral pumping, and fluid outflow through face separation. Face separation is therefore present as long as the seal is operating.
Combined seal keeps dust at bay Title: Unitary oil seal assembly Patent number: US5687972 Date: 18th November 1997 Inventor: G Petrak In oil sealing bpplications it is necessary to prevent the ingress of contamination from the external environment. In many rotary applications, excluding contamination can prove difficult where there is substantial relative motion between a rotating shaft and an outer housing, for example, in a planetary wheel of a vehicle. In many cases the shaft is free to slide axially, relative to the bore or housing and this can create sealing difficulties. The axial movement can break the contact between the component parts of the seal, typically a radial seal and a facial excluder seal, and allow the entry of dust and other abrasive particles. This contamination, embedded within the radial seal lip, can scratch the shaft and enable oil to leak to the outside. In this invention the radial and facial excluder seals are combined in such a way that both seals move axially with the shaft, maintaining contact with each
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Patents Varied groove depth gives early face separation Title: Face seal with angled grooves and shallow annular groove Patent number: US57021 10 Date: 30th December 1997 Inventor: J Sedy Assignee: Durametallic Corp The separation of the faces in a rotary fluid film face seal can be achieved through a shallow spiral groove in one of the faces, ending in a restriction. As the fluid medium enters the groove it meets the restriction, and the resultant build up of oressure seoarates the faces. Fluid can e;ter the spiral groove in Iwo ways. Firstly, the rotation of one of the faces can pump fluid through the groove, known as hydrodynamic force, and secondly, the pressure of the
Figure 1. Groove configuration
Sealing
Technology
No. 50
sealed liquid can also drive it through, separating the faces by hydrostatic pressure. Start-up of the equipment can be problematic to seal operation. When the seal is stationary there are no hydrodynamic forces. If the hydrostatic forces are not sufficient to counter the pressure which keeps the seal faces in contact, then the subsequent fact lock and resulting friction can destroy the seal. The hydrostatic force can be increased by extending the length of the short, deep grooves, which are necessary to generate hydrodynamic forces at full speed, though this leads to excessive leakage during full speed operation. The face seal described here. offers an optimisation of hydrodynamic and hydrostatic sealing characteristics, without causing increased leakage. The design, shown in Figure-l, is based around a combination of two groove arrangements, one (134), significantly deeper than the other (144). The shallow annular G-oove I144). is oreferablv ’ 0.00002 inch to’0.0600< inch. and the deeper groove [134), is 5 to 10 times deeper, approximately 0.0001 inch to 0.0003 inch. The passages (1521, have the same depth as the deeper groove.
allows smoother start-up.
When the seal is slationary, the high pressure fluid surrounding the outer diameter (128), enters into the deep grooves (134), and the shallow grooves (144). but is then restricted from further inward radial flow by a dam (1511. This pressurised fluid is sufficient to generate enough hydrostatic force to separate the faces. As the seal operates at higher rotational speed, the high pressure fluid in the deep grooves (134). is pumped out over the shallow groove region (1X3), and the areas between the grooves (141), forcing the seal faces apart. During operation of the seal, an equilibrium is established between the fluid inflow through spiral pumping, and fluid outflow through face separation. Face separation is therefore present as long as the seal is operating.
Combined seal keeps dust at bay Title: Unitary oil seal assembly Patent number: US5687972 Date: 18th November 1997 Inventor: G Petrak In oil sealing bpplications it is necessary to prevent the ingress of contamination from the external environment. In many rotary applications, excluding contamination can prove difficult where there is substantial relative motion between a rotating shaft and an outer housing, for example, in a planetary wheel of a vehicle. In many cases the shaft is free to slide axially, relative to the bore or housing and this can create sealing difficulties. The axial movement can break the contact between the component parts of the seal, typically a radial seal and a facial excluder seal, and allow the entry of dust and other abrasive particles. This contamination, embedded within the radial seal lip, can scratch the shaft and enable oil to leak to the outside. In this invention the radial and facial excluder seals are combined in such a way that both seals move axially with the shaft, maintaining contact with each
13