FIELD OF THE INVENTION  
       [0001]     This invention generally relates to systems for lubricating cutting tools, and deals more particularly with a lubrication system that can be carried on a portable power tool, such as a drill.  
       BACKGROUND OF THE INVENTION  
       [0002]     Machine tools use a variety of cutting tools such as milling heads and drills to cut and shape parts and workpieces, particularly those formed of metal. Lubricating fluids, also referred to as cutting oils, are often used to lubricate the metal-to-metal contact between the cutting tool and the workpiece, in order to reduce friction and increase cutting rate. Lubricating fluids also reduce the temperature of both the workpiece and the cutting tool during the cutting process. Accordingly, lubricating fluids increase tool life and improve the quality of the machined parts.  
         [0003]     A variety of sophisticated tool lubrication systems have been devised in the past, especially for larger machine tools, such as mills, lathes and drills. Some machining operations, however, require the use of portable, hand held power operated machine tools. For example, in the aircraft industry, small hand-operated drills are used to form fastener holes for rivets or screw, which are used to fasten an outer skin to structural members. In the past, the drill operator would manually apply a small quantity of cutting oil or other lubricating fluid to either a drill bit or an area of the workpiece in which a hole was to be drilled. This manual application of lubricating fluid sometimes resulted in too much or too little oil being applied. In any event, the procedure was time consuming since it required the operator to perform an additional step for each hole that was drilled. Moreover, the procedure was subject to oil spillage, prompting the need for cleanup and maintenance.  
         [0004]     Accordingly, there is a need in the art for a portable tool lubrication system which overcomes the deficiencies of the prior art discussed above. The present invention is directed towards satisfying this need.  
       SUMMARY OF THE INVENTION  
       [0005]     According to one aspect of the invention, a lubrication system for a portable machine tool is provided, comprising a reservoir for holding lubricating fluid, a nozzle for dispensing a pre-selected quantity of lubricating fluid, a pump assembly for drawing the fluid from the reservoir and pumping a pre-selected quantity of the fluid to the nozzle, and a pump control responsive to operation of the machine tool for causing the pump to pump the pre-selected quantity of fluid to the nozzle. The pump preferably comprises a cylinder assembly having a cylinder into which a pre-selected quantity of lubricating fluid is drawn from the reservoir. The piston has a forward stroke in which the pre-selected quantity of lubricating fluid is pumped to the machining operation, and a return stroke in which the next quantity of fluid is drawn from the reservoir. Check valves are provided that prevent backflow of fluid from the pump to the reservoir, and from the machining operation back to the pump. The stroke of the piston is adjustable, thereby allowing precise metering of the size of the fluid shot delivered to the cutting operations. Both the drill and the pump are driven by a source of compressed air.  
         [0006]     According to another aspect of the invention, a cutting tool lubrication system carried on a portable machine tool, comprises a reservoir for holding lubricating fluid, a dispenser for dispensing lubricating fluid to the cutting tool, a pump for drawing fluid from the reservoir and pumping the fluid to the dispenser, and a control responsive to each power of the machine tool to direct the pump to pump a pre-selected quantity of lubricating fluid to the dispenser. The dispenser is connected to the pump by a conduit, and a check valve is provided at the dispenser for preventing lubricating fluid within the conduits from flowing back to the pump.  
         [0007]     According to still another aspect of the invention, a system is provided for dispensing individual shots of a lubricating fluid used in drilling operations performed with a pneumatically powered, portable drill. The system includes a reservoir for holding lubricating fluid, and a pneumatically driven pump for drawing each shot of the lubricating fluid from a reservoir and for pumping the shot to the drilling operation. The system further comprises a controller responsive to each startup of the drill for connecting a source of pressurized air with a pump, the pump being responsive to pressurized air to pump a shot to the dispenser. In the preferred embodiment, the controller includes a user operator operated startup trigger carried on the drill and a flow control valve actuated by the trigger. Actuation of the startup trigger by the user in turn actuates the flow control valve, connecting the pressurized air source to both the drill and the pump. The pump includes a user adjustable pump stroke allowing pre-selection of the quantity of fluid in each shot.  
         [0008]     Various additional objects, features and advantages of the present invention can be more fully appreciated with reference to the detailed description and accompanying drawings that follow. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is block diagram of a portable tool lubrication system forming the preferred embodiment of the present invention.  
         [0010]      FIG. 2  is a top view of the portable tool lubrication system, the cover of the enclosure having been removed to reveal components within interior of the enclosure.  
         [0011]      FIG. 3  is bottom view of the system shown in  FIG. 2 .  
         [0012]      FIG. 4  is a side elevation view showing details of the piston and cylinder assembly which forms the pump. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0013]     Referring first to  FIG. 1 , a portable lubrication system generally indicated within the broken line  44  is intended to be used with a portable machine tool, such as a drill  42 . As will be later discussed, the portable lubrication system  44  may be mounted directly on the drill, or on fixtures upon which the drill is mounted to facilitate alignment and/or automation of the drilling operation. In any event, the lubrication system  44  is intended to be carried on or with the drill  42 , and thus is fully portable. Portable machine tools such as the drill  42  are typically powered by compressed air. Accordingly, there is a compressed air supply  10  which is connected through a control valve  40  to drill  42 . Typically, the control valve  40  will be mounted on, or may form an integral part of the drill  42 . In any event, the valve  40  is controlled by a trigger or other mechanical switch on the drill  42  which the user actuates in order to start up the drill  42 . When the drill trigger is depressed, a mechanical connection indicated at  46  to the valve  40  results in the valve  40  opening, thereby providing compressed air to the drill  42  which drives the latter.  
         [0014]     The portable lubrication system  44  broadly comprises a pump  12 , oil reservoir  14 , dispensing nozzle  20  and a pair of check valves  16 ,  18 . The pump  12  preferably comprises a piston and cylinder assembly including a cylinder  64  having a two-way piston  24  disposed therein which divides the cylinder into two chambers  22 ,  26 . The pump  12  may be powered by a variety of power sources, but in the illustrated embodiment, it is powered by compressed air derived from the air supply  10 . More particularly, chamber  22  in the cylinder  64  is coupled by line  28  to the control valve  40 . Thus, it can be appreciated that when the drill  42  is initially turned on, control valve  40  allows compressed air to flow simultaneously to the drill and the pump  12 .  
         [0015]     The oil reservoir  14  stores a quantity of suitable cutting oil or lubricating oil which is periodically replenished by the user. Reservoir  14  is connected by a hydraulic line  52  to a one way check valve  16  which controls the flow of oil between reservoir  14  and cylinder chamber  26 . During a retraction stroke of piston  24 , a partial vacuum is drawn in chamber  26 , thus opening check valve  16  and drawing oil from the reservoir  14  into the chamber  26 , filling the latter with a precisely metered quantity of oil, which is a function of the stroke of the piston  24 . A later discussed flow adjustment  32  is provided for the pump  12  which allows the user to adjust the exact quantity of oil drawn from the reservoir  14  into the chambers  26 . The flow adjustment  32  may comprise any of a variety of well known devices which adjust the back or draw stroke of the piston  24 .  
         [0016]     As compressed air is delivered through line  28  into chamber  22 , the piston  24  moves forwardly in a pumping stroke, forcing fluid in the chamber  26  to flow through check valve  18 , then to a dispensing nozzle  20  which is typically located near the site on the workpiece or part where the hole is to be drilled. The nozzle  20  dispense the pre-measured “shot” of oil onto the drill bit or onto the workpiece, depending on the user&#39;s preference.  
         [0017]     With a shot of oil having been dispensed, when the drilling operation is complete and the user releases the drill trigger, compressed air is removed from chamber  22  and a spring or other biasing mechanism (not shown) within the pump  12  causes the piston to move through its return stroke, toward the left as seen in  FIG. 1 . During the return stroke, any oil present within hydraulic line  30  is prevented from being drawn into the chamber  26  due to the presence of check valve  18 . However, check valve  16  opens during the retraction stroke, allowing oil from the reservoir  14  to flow into the cylinder chamber  26 , thus readying pump  12  to deliver the next shot of oil to nozzle  20  when the operator restarts the drill  42 .  
         [0018]     It can be seen from the arrangement shown in  FIG. 1  that precisely controlled, pre-selected quantities of oil are delivered to the cutting operation each time the operator starts the drill  42 . These shots of lubricating oil are delivered to the cutting operation automatically, without the need for the operator to manually perform any lubricating operations.  
         [0019]     The portable lubrication system  44  can be implemented in a variety of physical embodiments, one of which is shown in  FIGS. 2 and 3 . A generally rectangular housing  34  contains a chamber defining the reservoir  14 . The pump  12  as well as the check valve  16  along with related, connecting fluid passageways are formed within the housing  34  which may comprise, for example solid metal in which the passageways and components are formed and mounted. The housing  34  is provided with a cover  36  which is secured to one face of the housing  34  by means of screws (not shown) passing through screw holes  38 . A removable screw  44  and cover  36  allow user access to the reservoir  14 , permitting the user to refill the reservoir  14  when necessary. Flow adjustment  32  comprises a screw nut in the illustrated example, which adjusts the stroke of piston  24 . The pump  12  contained in housing  34  is connected to the control valve  40  by means of a pneumatic line  28 . The dispensing nozzle  20  forms part of an assembly including the check valve  18  and is connected to the housing  34  by means of a lubricating oil delivery line  30 .  
         [0020]     As previously indicated, the particular portable lubrication system  44  shown in  FIGS. 2 and 3  can be mounted on or near the drill  42  so as to be carried along with the latter as the operator moves to different locations. The delivery line  30  is preferably made of flexible material allowing the nozzle  20  to be moved around the workpiece, as necessary. It should be noted here that delivery line  30  remains filled with fluid at all times, since even when piston  24  retracts to draw oil from reservoir  14 , oil within delivery line  30  cannot be drawn back into the cylinder chamber  26  due to check valve  18  moving to its closed position.  
         [0021]     The lubricating system  44  prevents the operator from applying too little or too much oil in any given drilling operation since only a single shot is delivered when the operator starts up the drill  42 . Moreover, since the piston  24  automatically retracts to refill chamber  26  with oil when the operator turns off the drill  42 , the operator need not remember to recharge or take any other action for preparing the lubrication system  44  for the next drilling operation.  
         [0022]     The details of one suitable pump  12  are shown in  FIG. 4 . The cylinder  64  comprises a body having chambers  22  and  26  formed therein, as well as an air inlet port  58 , an oil inlet port  56  and an oil outlet port  54 . The air inlet port  58  is connected to pneumatic line  28 , while oil inlet port  58  is connected to check valve  16  via line  52 , and oil outlet port  54  is connected to check valve  18  by line  30 . An  0 -ring or similar seal  50  forms a fluid tight seal between the piston head  24  and the interior walls of the cylinder  64 . A central shaft  48  connected to the piston  24  extends through one end of the cylinder  64  and has an outer threaded end provided with an adjustment nut  62 . A compression spring  60  is captured between the body of the cylinder  64  and the nut  62 , thus biasing the piston  24  to retract (toward the left as viewed in  FIG. 4 ) The longitudinal position of the spring  60  on shaft  48  is therefore adjustable by nut  62 . The position of spring  60  along the shaft  48  determines the length of the retraction stroke of piston  24 , which in turn determines the volume of oil that is drawn into the chamber  26  from the reservoir  14 .  
         [0023]     The pressure of the compressed air entering air chamber  22  which is exerted on the piston  24  is always greater than the return force of the spring  60 , thus permitting the compressed air to overcome the spring force when the drill  42  is switched on, and drive the piston  24  forward to deliver a shot of oil out through port  54 . When the drill  42  is switched off, the air pressure in chamber  22  falls to a level below the force exerted by the spring  60 , resulting in the spring  60  forcing the piston  24  to move through a return stroke. During this return stroke, oil is drawn into the chamber  26  through the inlet port  56 , thus readying the system  44  for the next drill cycle.  
         [0024]     Although this invention has been described with respect to certain exemplary embodiments, it is to be understood that the specific embodiments are for purposes of illustration and not limitation, as other variations will occur to those of skill in the art.
A cutting tool lubrication system, suitable for use with portable, hand-held machine tools, automatically delivers single, pre-measured shots of oil to the cutting tool each time the operator powers up the machine tool. The lubrication system is carried on or with the tool and is operated by the same power source that drives the machine tool, such as compressed air. The lubrication system includes a lubricating fluid reservoir, a fluid pump, and a series of check valves for controlling the flow of fluid between the reservoir, the pump and a nozzle from which the fluid is dispensed.