Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C17/00—Sliding-contact bearings for exclusively rotary movement
  • F16C17/04—Sliding-contact bearings for exclusively rotary movement for axial load only
  • F16C17/06—Sliding-contact bearings for exclusively rotary movement for axial load only with tiltably-supported segments, e.g. Michell bearings
  • F16C17/065—Sliding-contact bearings for exclusively rotary movement for axial load only with tiltably-supported segments, e.g. Michell bearings the segments being integrally formed with, or rigidly fixed to, a support-element

Definitions

• the velocity at intermediate heights of the fluid thickness decreases at a known rate until the fluid in contact with the station ⁇ ary bearing pad adheres to the bearing pad and is motion- less.
• the bearing pad is deflected at a small angle to the rotating member, the fluid will be drawn into the wedge-shaped opening, and sufficient pressure will be generated in the fluid film to support the load. This fact is utilized in thrust bearings for hydraulic turbines and propeller shafts of ships as well as in the conventional hydrodynamic journal bearing.
• the present invention relates to improvements in hydrodynamic thrust bearings of the type which includes a plurality of discrete bearing pads mounted in a carrier in a circumferentially spaced relation. Gener ⁇ ally, the present invention relates to improvements in pad and carrier design.
• the pad surface bearing pad portion may also be coated with a separate material such as hardened rubber or the surface may have a separate pad insert of a high performance material such as silicon carbide.
• the support portion preferably has a shape which conforms to the shape of the openings in the car ⁇ rier. If this shape is non-cylindrical, the pad will be precisely positioned when it is fit into the carrier.
• a wear surface may be molded onto the pad when the pad support is such that wear is expected during operation, e.g. at start-up.
• the wear surface is prefer ⁇ ably formed from a material having a high PV limit such as CELEDYNETM. If necessary, a layer of surface roughness can be provided on the pad to better secure the wear surface to the pad.
• the edges of the pad may be tapered to improve inlet bending.
• FIG. 1A is a side cross-section of a thrust bearing construction according to the present invention.
• FIG. IB is a partial top view of the bearing construction of FIG.1A.
• FIG. 2 is a perspective view of a sector shaped thrust pad with arrows indicating the side lines for the top side and edge views.
• FIG. 3 is a perspective view of a circular thrust pad.
• FIG. 6F is a cross-section of the carrier of Fig. 6E.
• FIG. 9A is a front view of the bearing pad of Fig. 9.
• FIG. 10B is a front view of another bearing pad according to the present invention.
• FIG. 11 is a front view of another bearing pad according to the present invention.
• Figs. 7-7C illustrate a pad construction according to the present invention.
• a pad includes a sector shaped pad 23 supported on a support post 70.
• the support post 70 has an oval cross-section a radial dimension which is larger than its circumferential dimension.
• Pro ⁇ vision of an elongated post 70 of the type shown in Figs. 7-7C serves several functions. First, when a pad 20 of this type is mounted in a carrier 10 of the type shown in Fig. 6G (discussed below) having complimentary openings 101 for receiving the post 70, the pad 20 is automatic ⁇ ally positioned in the precise location desired. In con- trast, if the pad 20 were formed with a cylindrical sup ⁇ port, it would have to be positioned in some other way.
• an elongated oval post of the type shown in Figs. 7-7C affects the support of the pad portion 23. Specifically, since the support post 70 has a radial dimension greater than its circum ⁇ ferential dimension, the support of the pad 23 is more rigid in the radial direction than in the circumferential dimension. In the bearing pad 20 shown in Figs. 7-7C this effect is compounded since the sector shape of the pad portion 23 has a circumferential dimension greater than its radial dimension. Thus, as a result of both the shape of the pad portion 23 and the configuration of the support post 70, the circumferential ends of the pad por ⁇ tion 23 are relatively unsupported whereas the central region of the pad portion 23 is relatively rigidly sup ⁇ ported.
• the deflected orientation of the bearing pad permits lubricant to pass the radially inner edge RIE and enter the wedge region as a result of cen- trifugal forces and significantly inhibits the loss of fluid past the radially outer edge ROE which otherwise occurs as a result of the centrifugal forces acting on the fluid. While it is possible to optimize the design in this regard for any particular application, a general rule of thumb is that the geometric center of the support posts SC should be offset from the geometric center of the pad PC by about 10 percent.
• the support post 70 which supports the pad portion 23 is quite rigid. Indeed, this pad by itself would not permit movement of the pad portion 23 with six degrees of free ⁇ dom.
• the present inventor has found that movement with six degrees of freedom is not always necessary to achieve adequate results.
• the individual pads need only tilt or pivot about an axis parallel to the rotor.
• a known rocker pivot pad has nearly zero rotational pivot stiffness.
• Such bearings are known to provide adequate performance, but they are more expensive and difficult to tailor to individual applications.
• a pad having limited flexibility such as that shown in Figs. 7 and 7C is acceptable.
• the pad shape can be modified along the lines discussed above to achieve the disclosed results.
• the pad construction shown in Figs. 7-7C has limited flexibility. In many cases, this flexibility, though limited, is sufficient to achieve hydrodynamic operation. In other instances, the carrier 10 in which the pad 20 is mounted can be provided with flexibility to allow increased deflection if this is called for. In some cases, however, the relatively rigid support structure is adequate in all cases except during start up. In these instances, the present invention allows for the possible provision of a wear surface so as to avoid damage to the pad during start-up as shown in the embodiment of Fig. 7C. The objective of such a wear surface is to allow the pad to withstand wear caused during start-up. Even with a relatively rigid support structure of the type shown in Figs.
• the preferred embodiment of the present invention comprises the use of a CELEDYNETM resin molded around the pad as shown at 25 in Fig. 7C.
• the pad shown in Figs. 8-8C is symmetrical. Thus, its position within a bore 101 in a carrier 20 does not affect its performance. Hence, there is no need for means for precisely positioning the pad within the bore.
• This surface can be achieved by casting the part as a relatively rough surface. In the case of machined part, however, it is preferable to provide a layer of surface roughness 24 prior to molding the resin onto the pad.
• a layer of surface roughness 24 prior to molding the resin onto the pad.
• small pieces of bronze can be melted onto the pad surface to form a rough surface.
• the preferred method is to flame spray the pad with an aluminum/bronze (10% aluminum/90% bronze)alloy. By doing this, a relatively porus/rough surface can be achieved. This surface, during molding, allows the resin to flow into the surface craters and to lock into place.
• the pads are then heated slightly before they are inserted into the mold cavity, allowed to continue to heat in the mold, and then resin is injected onto the pad.
• the parts may then be annealed if desired. Tests have shown that the bonded surface shows good to excel- lent flow of material into the coating and adequate bond strength.
• Fig. 8B shows a pad 20 having a surface rough ⁇ ening layer 24 provided thereon. Again, this surface roughened layer 24 is preferably formed by flame spraying an aluminum/bronze alloy onto the pad surface.
• the support post 71 shown in Figs. 8 and 8A supports pad portion 23 at the geomet ⁇ ric center of the pad portion 23.
• the advantage of such an arrangement is that the pad is symmetrical. This simplifies manufacture and assembly somewhat. In other instances, however, it is preferable to have the support post offset with respect to the pad portion 23.
• Figs. 9- 10B depict bearing pads in which the support post 71 is offset to achieve the desired results.
• the support post 71 has a support center SC which is radially offset from the center PC of the pad portion 23 by an amount indicated as RO.
• the support is symmetrical about the circumferential center line CCL which is defined as a radial line passing through the center of the pad portion 23 and the axis of the carrier 10 (not shown) .
• the radial center line indicated as RCL in Fig. 9 is defined as the circle center on the axis of the carrier and passing through the pad center PC.
• the pad portion 23 is supported such that the radi ⁇ ally innermost edge RIE is supported for downward deflec ⁇ tion under loading so as to increase bending to allow centrifugal entrance of oil.
• the radially outermost edge ROE of the pad portion 23 is rigidly sup- ported so that it forms a fluid dam to prevent centrifu ⁇ gal leakage of oil.
• the point of attachment of the support post 71 to the pad portion 23 is normally shifted about 10 percent toward the outer diameter to increase bending.
• the pad portion 23 is also provided with a continuous taper 23t to increase inlet bending as dis ⁇ cussed above.
• the support post has a support center SC which is offset from the center PC of the pad portion 23 circumferen ⁇ tially by a circumferential offset amount indicated as CO in Fig. 10 and radially by an amount indicated as RO in Fig. 10.
• the radial offset serves essentially the same function as the radial offset in the bidirectional bear ⁇ ing shown in Figs. 9-9A and described above.
• the circum ⁇ ferential offset CO is provided to improve inlet bending by making the leading edge less rigidly supported.
• the pad portion 23 also includes a continuous taper 23t to improve inlet bending.
• the embodiment of Figs. 10-lOB includes a locator post 102 to allow the pad 20 to be precisely positioned within the carrier 10.
• Fig. 10B shows a slight modification to the bearing pad of Figs. 10 and 10A.
• the pad 20 is provided with a wear surface 25.
• the wear surface is preferably provided by molding a CELEDYNETM resin onto the pad portion 23.
• the support post 71 is also significantly thinner, and hence, more flexible than the support posts 71 shown in Figs. 10 and 10A.
• support posts described herein can have thin, thick or moderate diam- eters depending on viscosity, load, speed, envelope and general operating requirements.
• the operat ⁇ ing requirements can be modelled using finite element analysis to determine the optimum dimensions for any particular application.
• Fig. 11 shows another pad 20 according to the present invention.
• the pad 20 includes a pad portion 23, a support portion 72 and a base 73.
• the base 73 is designed to be mounted in a bore 101 in one of the carrier constructions 10 disclosed herein.
• the base 73 is formed with a thread 40 as discussed above in connection with Figs. 11A and 11B, for example.
• the support 72 of the pad in this case is formed with a con ⁇ tinuously curved surface which is thinnest at the central portion of the support 72 and flares out toward both the pad portion 23 and the base 73.
• this complex shape is roughly equivalent to the shape of the hole in a doughnut or, more technically, the shape enclosed within a torus or annulus which is a double- curved surface generated by revolving a circle about a straight line axis which does not contain the center of the circle.
• the purpose of the complex shape of the support portion 72 is to increase flexibility of the center region of the support post 72 and relieving stress from the end regions at which the post 72 joins the pad portion 23 and the base 73. These regions might other ⁇ wise be subject to stress concentrations.
• the pad 20 has a tendency to tilt more easily about the center of the support portion 72 to improve deflection.
• the support portion 72 may be coax ⁇ ial with the pad portion 23, to simplify manufacture and assembly. Alternatively, the support portion may be off- set either radially or both radially and circumferen ⁇ tially to achieve the aforementioned functional advan ⁇ tages.
• Figs. 12A-12B disclose another bearing pad according to the present invention.
• This bearing pad construction is similar to that shown in Fig. 11 and described above.
• the bearing pad 20 includes a pad portion 23, a base portion 73 and a sup ⁇ port portion 72.
• the support portion 72 again flares in a continuous curve toward both the pad portion 23 and the base 73.
• the center region of the support portion 72 is somewhat elongated such that the shape of the support 72 cannot, strictly speaking, be described as the shape defined as the void left in the center region of a torus.
• the support por ⁇ tion 72 achieves the same effects of providing maximum flexibility in the center region of the support 72 and relieving stress and reducing flexibility at those por- tions of the support 72 nearest the pad portion 23 and the base 73.
• the pad portion 23 is provided with a continu ⁇ ous annular taper 23t at the lower edge thereof. As noted earlier, the provision of such a taper improves inlet bending.
• the base 73 includes a locator projec ⁇ tion 102 for precisely positioning the pad 20 with the bores 101 of a carrier.
• a locator projec ⁇ tion 102 for precisely positioning the pad 20 with the bores 101 of a carrier.
• a locator post is especially useful when the post center is offset from the pad center.
• the bearing pad 20 may be provided with a wear surface 25.
• the wear surface 25 is preferably formed by molding CELEDYNETM to the pad portion 23 as shown in Fig. 12B.
• a surface roughening layer 24 may be provided on the surface of the pad por ⁇ tion 23 prior to molding of the resin or other material onto the pad portion 23.
• the pres- ent invention is the disclosure of easily machinable pad shapes.
• the circular pad shapes of the type disclosed in Figs. 8-12B can be readily formed from cylindrical bar stock using a lathe.
• Pad shapes which can be formed using a lathe provide a significant advan- tage over known constructions in which complex machining or casting must be performed both in terms of production cost and the cost and complexity of manufacturing proto ⁇ types.
• the pad would have to be lathed on more than axis to form such configurations.
• bearing pads which are formed separately from the carrier. Such constructions make it possible to use standard carriers 10 to achieve a wide variety of results using a relatively limited number of pads.
• base portions of a number of the pads shown herein are described as simple cylindrical bases which can be mounted in the bores, it should be understood that the base can be threaded, press fit, adhered with an adhesive or the like to the carrier.
• FIGS. 6A, 6B, 6C, 6D, 6E, 6F and 6G illustrate another aspect of the present invention whereby the bear- ing pads 20 can be precisely located within the carrier 10.
• the carrier 10 is provided with locating pins 102 non-symmetrically disposed within the bores 101 provided for receiving the bearing pads 20.
• the locator pin 102 can be received in one of the non- symmetrically disposed openings in a bearing pad support structure (or a similar opening provided somewhere else in the bearing pad) , to precisely position the bearing pad within the bore in the carrier 10.
• An alternative construction is illustrated in FIGS. 6C and 6D.
• locating protrusions 102 extending from the wall of the bore 101 and used instead of separate locat ⁇ ing pins.
• the locating protrusion can be received in a complementary notch formed in the dog leg or tertiary support portion of any of the bearing pads of the present invention.
• Figs. 6E-6F illustrate a similar construction in which locator holes 103 are formed in each of the bores 101.
• the locator holes 103 are adapted to receive the locator pins 102 formed on bearing pads such as, for example, those shown in Figs. 9A and 10A. Since bearing pads formed with a locator pin 102 can only be positioned within the bore 101 such that the locator pin 102 is received in the locator hole 103, the pads must be pre ⁇ cisely positioned if they are to be received in the open ⁇ ings 101.
• One advantage of the construction shown in Figs. 6E-6F is that the carrier 10 will receive pads which do not have a locator pin 102 just as it will receive pins that do have a locator pin 102.

Landscapes

• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Sliding-Contact Bearings (AREA)
• Support Of The Bearing (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=25488773

Family Applications (1)

Country Status (10)

Families Citing this family (6)

Citations (2)

Family Cites Families (3)

• 1993
  • 1993-09-16 CA CA002122258A patent/CA2122258A1/fr not_active Abandoned
  • 1993-09-16 BR BR9305637A patent/BR9305637A/pt not_active Application Discontinuation
  • 1993-09-16 WO PCT/US1993/008781 patent/WO1994007043A1/fr not_active Application Discontinuation
  • 1993-09-16 AU AU49268/93A patent/AU4926893A/en not_active Abandoned
  • 1993-09-16 EP EP93921643A patent/EP0617763A4/fr not_active Withdrawn
  • 1993-09-16 JP JP6508324A patent/JPH07501391A/ja active Pending
  • 1993-09-20 IL IL107045A patent/IL107045A0/xx unknown
  • 1993-09-22 MX MX9305838A patent/MX9305838A/es unknown
  • 1993-09-22 CN CN93117833.9A patent/CN1085295A/zh active Pending
• 1994
  • 1994-05-18 NO NO941846A patent/NO941846D0/no unknown

Patent Citations (2)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events