Abstract:
A mechanical system has a component to be lubricated that requires greater lubrication at lower speed conditions than would be required at higher speed conditions. A lubricant tower is biased to a position allowing a greater flow of lubrication to the component at lower speed conditions, then moved to a position at higher speed conditions where there is a lesser flow of lubrication.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application relates to a lubricant system for a component that requires more lubricant at lower speed than it may at higher speed. 
         [0002]    Modern mechanical systems are becoming more and more complex. Mechanical transmissions including complex gear drives are included to drive various accessories and components associated with many systems. The intermeshed gears may transmit high torque and rotate at varying speed across the operation of the systems. Lubrication is required for the gears. 
         [0003]    Typically, lubrication supply is tied to a speed of the system. In one example, lubrication is provided for gears to drive accessories associated with a gas turbine engine. The volume of lubricant delivered is proportional to the speed of the engine, and thus as engine speed increases so does the flow of lubrication. For most applications this is desirable. However, there are applications that require higher lubricant flow at lower speed. In such applications, a lubricant system that supplies lubricant in a volume proportional to the speed of the engine would be undesirable. 
         [0004]    One such application would be a starter for a gas turbine engine. The starter must typically overcome the inertia of the engine components at start up and when the engine is at low speed. At these conditions lubricant is most needed by the gears in the starter to in turn drive components of the gas turbine engine. Conversely, at high speed those gears do not require lubrication. 
       SUMMARY OF THE INVENTION 
       [0005]    A mechanical system has a component to be lubricated that requires greater lubrication at lower speed conditions than would be required at higher speed conditions. A lubricant tower is biased to a position allowing a greater flow of lubrication to the component at lower speed conditions, then moved to a position at higher speed conditions where there is a lesser flow of lubrication. A gas turbine engine is also disclosed. 
         [0006]    These and other features of this application may be best understood from the following drawings and specification. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  schematically shows a gas turbine engine. 
           [0008]      FIG. 2  shows a lubricant application point within the  FIG. 1  gas turbine engine. 
           [0009]      FIG. 3A  shows a first embodiment lubricant supply. 
           [0010]      FIG. 3B  shows a second position of the  FIG. 3A  embodiment. 
           [0011]      FIG. 3C  shows an alternative embodiment. 
           [0012]      FIG. 4  shows another embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]      FIG. 1  schematically shows a gas turbine engine  19 . A core engine  20  incorporates a fan, a compressor, a combustor, and a turbine, as known. The turbine drives a shaft  22 . The shaft  22  engages an accessory gear box  24 . The accessory gear box  24  may include a number of accessories which operate to support the operation of the engine  20 . Examples may be a lubricant pump and a fuel pump for the engine. 
         [0014]    One other component within the accessory gear box is a starter shown schematically at  25 . The starter  25  engages the shaft  22  and begins to rotate the shaft  22  at start-up of the gas turbine engine  19 . 
         [0015]    As shown in  FIG. 2 , the starter  25  may incorporate gears  26 . The gears  26  require lubrication, and a lube tower  28  is shown which communicates with a supply of lubricant to supply oil  32  from orifices  30  to the gears  26 . A hole  34  is shown to mount the tower  28  within the accessory gear box  24 . 
         [0016]    As mentioned above, the starter encounters high torque, and has a requirement for higher amounts of lubricant at start up. Once the engine has started, the torque and load on the gears  26  is dramatically reduced. Current lubricant systems, however, supply lubricant at flow rates which are proportional to the speed of the engine, and thus would supply more lubricant to the starter gears  26  at times when it is much less necessary to have the lubricant. 
         [0017]    Other components which may require reduced lubricant flow under such conditions could be a journal bearing in an aircraft such as a military aircraft which sees a relatively low load during steady state altitude operating conditions. Thus, while this application specifically discloses its use for starter gears, it will extend to other components wherein the flow of lubricant is more critical at a lower speed application. 
         [0018]      FIG. 3A  shows a first embodiment tower  28 . A housing  29  provides a valve sleeve for a valve spool  40 . A stop  36  provides a reaction surface for spring  38  against a land  39  on the valve spool  40 . A step  51  prevents spool  40  from being forced out of housing  29 . Lubricant is supplied to an inlet  50 . The valve spool  40  has circumferentially positioned windows  52  which communicate with an orifice  30  and allow lubricant to pass from the inlet  50  through inner bore  100  to at least one window  52  and out the orifice  30  at low speed low pressure conditions. 
         [0019]    The size of the window  52 , and the orifice  30 , may be sized such that a large volume of lubricant flow will occur in the position illustrated in  FIG. 3A  and at low speed conditions. In another embodiment, the position of the stop  36  is adjustable to allow for various spring heights to dial in the proper pressure set point. 
         [0020]      FIG. 3B  shows a higher speed condition. The pressure of the lubricant supplied to the inlet  50  has now increased. This is true because a lube pump is driven by the accessory gear box  24 , and its output is proportional to speed. The lubricant reacts off surfaces  54  and drives the valve spool  40  upwardly against the force of spring  38 . The window  52  no longer communicates with the orifice  30 . Rather, a surface  53  on the spool  40  blocks the orifice  30 . Now, lubricant will no longer be supplied to the gears, and may be directed elsewhere, where there is a greater need for lubrication at high speed conditions. While this embodiment completely blocks flow, this concept extends to arrangements where the flow is simply restricted. 
         [0021]      FIG. 3C  shows an alternative feature. When the valve spool  40  is in the  FIG. 3B  position, rather than simply blocking flow, flow from the window  52  may flow through a port  300  to another use  301 . That is, rather than simply blocking flow, the tower  28  may redirect it to another component. 
         [0022]      FIG. 4  shows an embodiment tower  60  which results in a somewhat smaller axial length due to the repositioning of a spring. In the embodiment  60 , the window  66  is shown aligned with an orifice  130 . The housing or valve sleeve  62  receives the valve spool  64  as in the prior embodiment. A spring stop  68  provides a reaction surface for a spring  70  and a land  72  on the spool  64  provides an opposed reaction surface. The valve spool  64  is held in the illustrated position at which lubricant can be supplied to the orifice  130 . This is a low speed condition. As shown, surfaces such as  76  within the valve spool  64  will see the increased pressure as the speed, and hence the pressure of the lubricant passing into the inlet  150  of this embodiment increases. As this occurs, the spool  64  will be driven upwardly in this figure, and the window  66  will no longer communicate with the orifice  130 . 
         [0023]    Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.