Abstract:
A journal bearing having a working surface for contacting a shaft, and channels provided on the working surface and being configured to collect lubricant and redirect lubricant across the bearing working surface. A method for lubricating a bearing assembly is provided where lubricant is delivered to the working surface of the bearing, the lubricant is collected on the surface and directed to areas of the bearing surface which are in need of lubricant to provide an even coverage of lubrication across a bearing working surface.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to bearings, and more particularly to bearings which have lubricated bearing surfaces. 
     2. Description of the Prior Art 
     A number of conventional bearing assemblies are known which operate with the use of lubricants to prolong the life of the bearing and the apparatus in which the bearings are used, as well as to increase the efficiency of the bearing. Vibrations are encountered as a result of the loads and other forces which are imparted to the bearings and contacting surfaces. Administering lubricants to a bearing surface is challenging because in many instances the bearing surfaces which require the lubrication are in contact with another surface. 
     U.S. Pat. No. 4,568,204, which issued on Feb. 4, 1986 to William S. Chambers and is assigned to Kingsbury, Inc., the assignee of the current invention, and which is incorporated herein by reference, discloses a journal bearing with a leading edge oil distribution groove. The oil distribution grove directs the oil against the working faces of the shoes where it is needed. The journal bearing of the &#39;204 patent provides an improved bearing which conserves oil. 
     In the operation of bearings, there are generally different ways to run the bearings. For example, a bearing can be run flooded, whereby a sufficient quantity of oil is delivered to the bearing to provide as much oil as the bearing needs. However, in some cases, although flooding the bearing with an endless supply of oil may minimize vibrations, it is not efficient. In many bearing applications, it is preferred to run bearings evacuated, and not flooded. This is generally done to conserve power and to enable the bearing to run cooler. 
     While certain bearing vibrations may be considered to be minimal, it is often important to reduce even these vibrations as much as possible. To this effect, some specifications for machinery require that certain tolerances be met, such as, for example, a maximum vibration level. Vibration levels are often additive and take into account the total cumulation of vibration. Any subsynchronous vibration will therefore add to the total level of maximum acceptable vibration. 
     While periodic adjustments can be made to machinery over time in order to temper the undesirable vibrations, it is for the most part time consuming to make the adjustments. Moreover, if the vibrations are allowed to remain before an adjustment is made, the bearing instability caused by the vibrations can eventually ruin a machine, as the bearing surfaces as well as other components may wear excessively against each other. 
     It is known practice to admit lubricant through a hole or passageway to lubricate the surface of a bearing. Where oil is pumped through a hole, the oil is most usually abundant in those areas of the bearing surface immediately near the hole, and least abundant in the areas furthest from the hole. U.S. Pat. No. 4,568,204 provides an improvement in a journal bearing to supply lubricant to those areas of a bearing surface which are in need by providing a distribution groove on the bearing shoe work surface and utilizing o-rings to prevent spillage of oil into areas where it is not needed. 
     It is desirable to reduce the oil flow in a bearing lubrication system without effecting the operation of the bearing assembly. Energy conservation is promoted by reducing the power loss, reducing the amount of oil used and increasing the load carrying capabilities. A further benefit is that when the amount of oil required is reduced, the system may employ a smaller pump and other auxiliary equipment and therefore be more efficient. 
     It is an object of the present invention to provide a bearing assembly which has the benefits of an evacuated bearing assembly, but with the lower initial vibration levels associated with flooded bearing systems. 
     SUMMARY OF THE INVENTION 
     The present invention provides a novel bearing apparatus and method for lubricating the bearing which increases the load carrying capacity, uses less oil, consumes less power, enables the use of smaller auxiliary equipment, and is more efficient to operate than the prior bearing types. 
     The objects of the invention are accomplished by providing a lubricant distribution feature which facilitates coverage of a bearing working face with a lubricant across its surface. The lubricant which is admitted to the bearing surface is redirected from one location on the bearing surface to another location on the same bearing surface. Preferably, a hole or passageway in the bearing components for the admission of the lubricant, such as oil, delivers the oil to the bearing surface. Excess oil is collected from the bearing surface and redirected to those areas of the bearing surface which are in need of oil. Preferably, the redirection of the oil is accomplished to provide an even distribution of lubricant across the bearing surface. The amount of oil therefore is conserved since, what was excess oil in one area of the bearing working face is now captured and supplied to other areas without the need to increase the oil flow rate. Channels in the bearing surface are provided on each lateral edge thereof. The channels are configured to increase the contacting surface of those areas of the bearing working face which would otherwise not received a sufficient amount of oil, unless the oil was supplied in an excessive or flooded condition. 
     It is another object of the present invention to accomplish the above objects where the bearing is a journal bearing having a plurality of shoes positioned around a ring, and where the lubricant is redirected over the working face of the shoes to reduce the amount of oil required. 
     It is another object of the present invention to provide a shoe for use with bearings, and in particular with journal type bearings, which has the novel feature of redirecting the oil from one area of the shoe working face to another area which is in need of lubricant. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a journal bearing shown ,with the improved lubrication features according to the present invention, positioned on a rotating shaft. 
     FIG. 2 is a front view in elevation of the journal bearing shown in FIG.  1 . 
     FIG. 3 is a view taken as indicated by the lines and arrows  3 — 3  which appear in FIG.  1 . 
     FIG. 4 is a view in section taken as indicated by the lines and arrows  4 — 4  of FIG.  1 . 
     FIG. 5 is an enlarged view of an oil feed tube as shown in FIG.  1 . 
     FIG. 6 is a graph which plots the vibration levels (in mMil/DIV) against shaft speed in revolutions per minute (rpm) to show broadband, subsynchronous vibrations associated with a Kingsbury LEG journal bearing run in an evacuated steady state condition at 10,000 rpm. 
     FIG. 7 is a graph which plots the vibration levels (in mMil/DIV) against shaft speed in revolutions per minute (rpm) to show broadband, subsynchronous vibrations associated with a Kingsbury LEG journal bearing run in a flooded steady state condition at 10,000 rpm. 
     FIG. 8 is a graph which plots the vibration levels (in mMil/DIV) against shaft speed in revolutions per minute (rpm) to show broadband, subsynchronous vibrations associated with a Kingsbury LEG journal bearing run in a flooded steady state condition at 10,000 rpm, but run with a lower flow rate than the LEG bearing associated with FIG.  7 . 
     FIG. 9 is a graph which plots the vibration levels (in mMil/DIV) against shaft speed in revolutions per minute (rpm) to show broadband, subsynchronous vibrations associated with a journal bearing constructed according to the present invention and run in a steady state evacuated condition at 10,000 rpm. 
    
    
     As used herein, the term LEG is a trademark of Kingsbury, Inc., Philadelphia, used in connection with hydrodynamic bearings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning to the drawings, there is shown a journal bearing  110  constructed in accordance with a preferred embodiment of the present invention. The journal bearing  110  carries the radial load of a shaft  112  mounted for rotation therein in a direction indicated by arrow  114 . The journal bearing  110  has five shoe assemblies  116  which are retained and positioned with an annular aligning ring  118 . The ring  118 , for example, can be provided in two split half sections which are secured together by means of joint screws  120 , as shown in FIG.  2 . 
     Referring to FIG. 1, the shoe assemblies  116  are retained within a circular inner rim  122  of the aligning ring  118  in circumferentially equally spaced relation. Each shoe assembly  116  comprises an arcuate shoe  124  provided with a bearing liner  125  on its inner surface, a shoe support  126  received in a recess hole centrally located in the outer surface of shoe  124 , and a shoe support shim  128  located at the bottom of the recess hole containing the associated shoe support  126 , the shims  128  being used for adjusting the position of the shoes  124  to allow for preloading of the bearing  110  as is conventional in the art. The bearing liner  125  provides a radially inwardly working face  130  of each shoe assembly  125  which face  130  is provided with the oil distributing means in accordance with the invention as will be described in detail hereafter with particular reference to FIG.  3 . 
     The shoe support  126  of each shoe assembly  116  is arranged to contact an insert  132  retained in aligning ring  118  in alignment with an associated shoe support  126 . Each shoe support  126  and insert  132  have cooperating spherical surfaces to allow the shoe assemblies  116  to pivot freely in any direction to conform to the surface of the shaft  112  as it rotates. The shoe assemblies  116  are preferably retained axially by a pair of shoe retaining plates  134  and  136  which have an annular configuration and are made of split halves. Each of the shoe retaining plates  134  and  136  is secured to a side of aligning ring  118  by means of the plurality of circumferentially spaced screws  138  in the manner shown in FIG.  1 . Each of the shoes  124  is retained in position relative to the side plates  134  and  136  by means of a pair of shoe stop pins  140  and  142 , respectively, which engage the shoe  124  from each side thereof as shown in FIG.  4  and at a central location as is shown in FIG. 1. A pin  143  is provided in aligning ring  118  for locating bearing  110  in its housing. 
     A lubricant, such as oil, may be supplied to the working face  130  of each shoe assembly  116  by any conventional manner, such as sprays, spray bars, or drill holes that direct oil toward the shaft  112  between the shoes  16 , or other methods that would deliver oil to the shaft  112  at the leading edge of the shoes  16 . In the preferred embodiment of the invention illustrated herein, an oil distributing groove  150  is formed near the leading edge  151  of working face  130  of each shoe assembly  116  and has a configuration and location as is best shown in FIG.  3 . The oil distributing groove  150  is located near the leading edge  151  of working face  130  and extends thereacross between the lateral edges  152  and  153  of the shoe working face  130 . 
     In the preferred embodiment of the invention illustrated herein, an oil supply hole  160  is associated with each shoe assembly  116 . The oil supply hole  160  is provided, as shown in FIG. 1, to extend radially through the aligning ring  118  at a location aligned with the center of the oil distribution groove  150 . Preferably, the outer end of each oil supply hole  160  communicates with a circumferentially extending oil inlet groove  162  (FIG. 5) which cooperates with the housing for journal bearing  110  to define an oil inlet conduit extending circumferentially around the exterior of aligning ring  118  for use in delivering oil supply thereto into the outer end of each oil supply hole  160 . 
     Oil is delivered to the oil distributing groove  150  by any conventional means. For example, as shown in FIG. 5, each shoe assembly  116  may be provided with an oil feed tube assembly  163  providing a radially extending passage  164  extending radially between the associated oil supply hole  160  and an opening formed by a socket  167  communicating with the center of oil distributing groove  150 , as shown in FIG.  1 . Each oil feed tube assembly  163  has ball-shaped portions  166  and  168  formed at the ends thereof and received in sockets  167  and  169  formed in shoe  124  and aligning ring  118 , respectively. Ball-shaped portions  166  and  168  are preferably provided with O-rings  170  and  172 , respectively, constructed and arranged to contact the walls of sockets  167  and  169  in sealing engagement so that each oil feed tube assembly  163  is sealed against oil leakage. A shoulder  175  is formed in the opening of socket  167  for retaining portion  166  of the tube assembly  163  in engagement with shoe  124 , and similarly, a shoulder  177  is formed at the opening to socket  169  for retaining the other end  168  of oil feed tube assembly  163  in engagement with aligning ring  118 . 
     Oil feed tube assembly  163  performs a dual function. Besides supplying oil from the oil supply hole  160  to the oil distribution groove  150  and preventing oil leakage from the tube assembly  163  because of the O-rings  170  and  172 , the oil feed tube assembly  163  also assists in retaining the shoe  124  in position on the aligning ring  118 . Also assisting in retaining the shoes  124  in ring  118  are the retainer pins  140  and  142  which extend from the shoe  124  into the retaining plates  134  and  136  as described above (FIG.  4 ). 
     Each of the retaining plates  134  and  136  is provided with four vertically extending discharge holes  184  and  186 , (FIG.  4 ), respectively for suitable draining of oil to a suitable oil collector for recirculation to the oil system, as is conventional in the art. 
     Means for directing lubricant (e.g., oil) from a first location on the shoe working face  130  to a second location on the shoe working face  130  is shown in FIG.  3  and comprises channel means for holding lubricant therein and redirecting the lubricant to areas of the shoe working face  130  to facilitate coverage of the working face  130  with lubricant. The lubricant, such as oil, is delivered to the working face  130  through the oil supply hole  160 , and through the passage  164  through which the oil emerges on the working face  130  of a shoe assembly  116 . The oil supplied to the working face  130  collects in the distribution groove  150  and is drawn across the working face  130  when the shaft  112  is rotated. The channel means is shown preferably comprising a pair of channels  190 ,  191  which are formed in the working face  130  of the shoe assembly  116 . The channels  190 ,  191  are provided to capture excess lubricant and direct lubricant from one location on the working face  130  to another location on the working face  130  where it is needed. The configuration of the channels  190 ,  191  facilitates an even coverage of lubricant across the working face  130  so that it is not necessary to flood the bearing  110  in order to achieve effective lubrication. The channels  190 ,  191  are shown each having an elongated first portion  192 ,  193 , respectively, which is provided along side a respective lateral edge  152 ,  153  of the working face  130 . The channels  190 ,  191  are also shown with a second portion  194 ,  195 , respectively, which is connected for communication with a respective first channel portion  192 ,  193 . The second portions  194 ,  195  are angled to extend across the working face  130 , such that on an x-y axis, the channel portion has an x and y component. The angular portions  194 ,  195  of each channel directs the lubricant away from its respective lateral edge  152 ,  153  and toward the center of the working face  130 . 
     In the preferred embodiment of the invention illustrated herein, the oil flow through the journal bearing  110  is described below. The oil is supplied to the groove  162  (FIG. 5) on the exterior of aligning ring  118  and flows radially inwardly through the oil supply holes  160  to the passage  164  of the associated oil feed tube assembly  163 . The oil then flows from passage  164  into the center of oil distributing groove  150  and outwardly across the groove  150 . As shaft  112  rotates past the leading edge  151  of each working surface  130 , it draws oil from the oil distributing groove  150  along working surface  130  toward its trailing edge  154 . As the oil is drawn from the groove  150 , it tends to disburse across the working face  130 . The oil flow is forced from the center of the working surface  130  to each lateral edge  152 ,  153  thereof. Channels  190 ,  191  capture oil moving toward the lateral edges  152 ,  153  of the shoe working face  130  for redistribution on the shoe working face  130 . The oil moves along channels  190 ,  191  to fill each channel  190 ,  191 , rather than exiting off of the working face  130 , which conserves the oil and redirects it from one location to another on the working face  130 . Each channel  190 ,  191  preferably has a respective first portion  192 ,  193 , and a second portion  194 ,  195 . The first portion  192 ,  193  of each channel  190 ,  191  is preferably provided to accumulate oil at each respective lateral edge  152 ,  153 . The second portion  194 ,  195  of each channel is shown angled in relation to its corresponding, respective first channel portion  192 ,  193  to facilitate the distribution of oil across the working face  130  of the shoe  116 . Oil is collected and stored in the channels  190 ,  191 , and, as the shaft  112  is rotated, is drawn from the channels  190 ,  191  as needed. 
     The configuration of the channels  190 ,  191  facilitates an even coverage of lubricant across the bearing working face  130  so that it is not necessary to flood the bearing  110  in order to achieve effective lubrication. 
     Referring to FIGS. 6-9, the improved results obtained with a journal bearing constructed according to the present invention are shown in comparison with other bearings. FIG. 6 shows a plot of the vibration levels (in mMil/DIV) against shaft speed in revolutions per minute (rpm) where the broadband, subsynchronous vibrations associated with a Kingsbury LEG journal bearing run in an evacuated condition are observed. The graph in FIG. 6 shows vibrations for the bearing operating at a steady state condition at 10,000 rpm. In FIG. 7, where the Kingsbury LEG journal bearing was run flooded at 10,000 rpm, the vibration occurring at the subsynchronous frequency range in the first half of the speed range is relatively flat compared with that of FIG.  6 . FIG. 8 shows a graph corresponding to a Kingsbury LEG journal bearing run at 10,000 rpm in a flooded condition, but with a lower oil flow rate than the LEG bearing associated with FIG. 7, the flow rate being 3 gallons per minute (gpm) for the FIG. 8 run and 6 gpm for the bearing of FIG.  7 . The results of the vibration in FIG. 8 are somewhat between those observed for the bearing conditions in FIGS. 6 and 7. 
     The results shown on the graph in FIG. 9 appear to compare with the results shown in FIG. 7, for the flooded bearing where there is a decrease in the vibrations at the subsynchronous frequency range, particularly at the first half of the speed range (x-axis). However, the FIG. 9 results correspond to a journal bearing according to the present invention, where the bearing was run evacuated and with a flow rate of 3 gpm, which is half the flow rate of the flooded run for the bearing corresponding to FIG. 7. A comparison of the plots of FIGS. 6-9 demonstrates the improved results achieved with the present invention. In accordance with the invention, the benefits of obtaining the low vibrations at a subsynchronous range associated with a flooded bearing system are obtained with an evacuated bearing which, up to now, have not been seen. 
     It will be understood that while shown and described with the journal bearing referred to above, the present invention has application to other bearings, such as those which have a bearing surface which is to be kept lubricated, including bearings through which lubrication is admitted through a hole communicating with the bearing surface, and bearing shoes. These and other advantages of the present invention will be understood from a reading of the background of the invention, the summary of the invention, the brief description of the drawings, the detailed description of the preferred embodiments, and the appended claims.