Lubricating tool for feeding a lubricating mixture to a cutter

A lubricating mixture of a lubricant and air is supplied to a cutting location by a lubricating tool with a spring biased piston dividing a cylinder into an air chamber and a lubricant chamber. The air chamber is connectable to a pressurized air source. The lubricant supply chamber is selectively connectable through a control valve to a lubricant source or to an exchangeable lubricant and air mixing attachment also connected to the pressurized air source. The attachment includes three flow restrictors. Two restrictors feed air and lubricant to a mixing area. One restrictor feeds the mixture to an output. Different sets of restrictors with different flow restricting characteristics provide an exact mixture dosage for satisfying any cutter lubricating requirement. It is merely necessary to replace one attachment by another attachment having different flow restricting characteristics.

PRIORITY CLAIM

This application is based on and claims the priority under 35 U.S.C. §119 of German Patent Application 103 41 919.5, filed on Sep. 11, 2003, the entire disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to supplying a lubricating mixture to a cutter of a power tool which is used to perform mechanical machining operations on metals and synthetic materials.

BACKGROUND INFORMATION

Such power tools are mobile, manually guided, pneumatically driven and require a supply of a lubricant to the cutter when the power tools are in operation. Such operations include, for example drilling, reaming, countersinking of bores, and the like. Such power tools comprise a mobile feed advance unit and are widely used in aircraft construction. The lubricant is primarily a mixture of lubricating oil and pressurized air. During operation the lubricating oil-air mixture is fed from a supply container to the cutting location where a cutter, such as a drill bit, a reamer or any other material removing tool engages a workpiece. The oil discharged from a supply container during operation of the tool is replenished when the power tool is not in operation.

German Patent Publication DE 43 39 770 A1 discloses a mobile precision drilling power tool that can be locked in a fixed position at a drilling location of large work pieces. The conventional power tool is constructed for precision drilling operations whereby a liquid lubricant is supplied all the way to the cutting tool edges. The known drilling power tool has a tool spindle carrying a chuck. The spindle is driven to rotate and for an axial feed advance of the spindle. The flow of lubricant passes through the spindle.

Conventional tools of the type described above have certain disadvantages or drawbacks such as an inadequate performance particularly when the lubricant supply system must also feed air to the cutting location. Another drawback is seen in that the dosing adjustment is inadequate so that either too much or too little lubricant is supplied to the cutting location. Moreover, the supply of lubricant takes place in cycles rather than continuously in response to constant process parameters. Further, conventional lubricating devices are constructed with a particular power tool or machine tool in mind and thus require an adaptation when a use for other power tools is intended. Frequently, such adaptation is not possible with regard to certain or even any power tools. Still another drawback of conventional lubricating tools is seen in that different drilling and friction conditions cannot be fully satisfied when a power tool is used in different operating positions such as horizontal and vertical drilling operations. Still another drawback is seen in that the lubricant reaches the cutting location only after a rather long reaction time following the activation of the lubricating tool.

OBJECTS OF THE INVENTION

In view of the foregoing it is the aim of the invention to achieve the following objects singly or in combination:to provide a compact lubricating device for power tools and machine tools, that is capable of feeding an optimal continuous lubricant supply directly to the cutting location and in accordance with any tool specific lubricating requirements;to make sure that the supplied volume or quantity of lubricant is a minimum quantity sufficient for lubricating all cutting edges currently in action;to provide the lubricating device with an exchangeable dosing attachment for precisely dosing the lubricant quantity or volume and any required air volume in response to any particular cutting operation requirements; andto provide a lubricating device for power tools that operates equally efficient in all operating position.

The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification. The attainment of these objects is, however, not a required limitation of the present invention.

SUMMARY OF THE INVENTION

A lubricating tool according to the invention is suitable for supplying a lubricant and air as a lubricating mixture to a cutting location where a cutter engages a workpiece, said lubricating tool comprising a housing enclosing a hollow cylinder, a piston in said hollow cylinder dividing said hollow cylinder into an air pressure chamber and a lubricant supply chamber, a compression spring positioned in said air pressure chamber between said piston and said housing, an exchangeable lubricant and air mixing attachment also referred to as dosing or mixing attachment securable to said housing, a flow control valve connected to said housing, said flow control valve having a first port communicating with said lubricant supply chamber, a second port communicating with said exchangeable lubricant and air mixing attachment and a third port communicating with a lubricant source, said flow control valve further comprising a control input for switching said flow control valve between filling said lubricant supply chamber from said lubricant source and feeding lubricant from said lubricant supply chamber to said exchangeable lubricant and air mixing attachment, said lubricating tool further comprising a pressurized air conduit communicating said air pressure chamber and said exchangeable lubricant and air mixing attachment with a pressurized air source, said lubricating tool further comprising an output connected to said exchangeable lubricant and air mixing attachment for feeding said lubricating mixture to said cutting location.

Advantages of the invention are seen particularly in its compact, so to speak miniaturized, construction that incorporates a dosing and mixing device in the form of the exchangeable lubricant and air mixing attachment that produces an oil pressurized air lubricating mixture for cutting tools. The lubricant that can be handled by the present lubricating tool preferably has a low to medium viscosity within the range of 10 to about 50 mm2/sec. Another advantage is seen in that the oil and pressurized air mixture can be dispensed with a linear or uniform oil feed advance rate, for example a linearly diminishing feed advance rate for optimizing the lubricant consumption and avoiding waste of lubricant. According to the invention such lubricant consumption depends not only on the type of lubricant used, but also on the exchangeable dosing and mixing attachment and on the flow resistance of the supply conduit between the present lubricating tool and the cutting location of a power tool. Another advantage is the possibility of exchanging the dosing and mixing attachment so that for example a constant dose of lubricant adapted to the requirements of any particular power tool cutter combination is supplied to the cutting location by a system of fixed flow control valves or flow restriction throttles also referred to as flow restrictors. More specifically, the mixing ratio of lubricating oil and pressurized air can be adapted to the particular known lubricating requirements by selecting the proper dosing attachment for any cutter.

A group of fixed flow restrictors is constructed as an insert for or an attachment to the lubricating tool housing, whereby different attachments will provide different dosing quantities or dosing ratios. Thus, the oil volume and the pressurized air volume are individually controlled independently of one another. Each different attachment has the same ports in the same positions for communicating with air and oil supply ports and channels in the lubricating tool housing. Yet another advantage of the lubricating tool according to the invention is seen in that a supply chamber for lubricant such as oil and air can be integrated into the lubricating tool which is thus self-sufficient and suitable for mobile use. Moreover, due to the position of the compression spring in the air supply chamber the force of this spring is effective on the piston in the cylinder housing, whereby the lubricant can be effectively supplied in any operating position of the lubricating tool because the spring force and the air pressure combine their action on the piston in the lubricating tool housing.

DETAILED DESCRIPTION OF A PREFERRED EXAMPLE EMBODIMENT AND OF THE BEST MODE OF THE INVENTION

FIG. 1shows a conduit circuit with arrows indicating flow directions of the present lubricating tool LT. A supply tank1encloses a lubricant supply source1A and a separate pressurized air source1B. The lubricant source1A may hold lubricating oil at a pressure P equal to or in excess of 2.5 bar. The lubricating tool LT is connected to the lubricant supply source1A through a lubricant conduit7, preferably connectable to the source1A by a quick coupler QC and preferably through a check valve RSV1to prevent spilling and backflow. The tool LT is further connectable to the pressurized air source1B through a control valve V1, through a check valve RSV2and through a flow restrictor FD connected in series in a pressurized air supply conduit5. Pressure sensors P0and P1are preferably connected to the pressurized air conduit5upstream and downstream of the flow restrictor FD respectively. The restrictor FD limits the volume of pressurized air supplied to the lubricating tool LT, particularly to an exchangeable lubricant and air mixing attachment or insert9which also forms a dosing device to be described in more detail below.

The tool LT comprises a housing10enclosing a cylinder divided by a piston3into a first pressurized air chamber3A and a second lubricant supply chamber3B. A piston biasing compression spring2is arranged in the pressurized air chamber3A which has an inlet port4connected to the pressurized air conduit5downstream of the restrictor FD. Thus, the force or pressure exerted on the piston3is the sum of the force exerted by the compression spring2and the force or pressure provided by the pressurized air in the conduit5.

The lubricant supply chamber3B communicates through a channel6and a port6A in the housing10and through the flow control valve V2with the lubricant supply conduit7or with the exchangeable attachment9. For this purpose the flow control valve V2has three ports P1, P2, P3. A first port P1is connected to the housing port6A when the valve V2is secured to the housing10. The lubricant supply chamber3B receives lubricant through channel6and port6A when the valve ports P1and P3communicate with each other as shown inFIG. 1. The second valve port P2communicates with the exchangeable lubricant and air mixing attachment9through a channel8and a port8A. When the tool LT is operated for lubricating, the valve ports P1and P2communicate with each other and lubricant is supplied from the chamber3B to the restrictor R1.

The check valve RSV2prevents a backflow of pressurized air into the air source1B, just as the check valve RSV1prevents a backflow of lubricant into the lubricant source1A. Thus, an uncontrolled outflow of lubricant from the lubricant supply chamber3B and an outflow of air from the conduit5are prevented when that chamber3B is completely filled with lubricant such as oil and the tool is not used actively for lubricating and is decoupled by the quick coupler QC from the lubricant source1A.

Referring toFIGS. 2,2A,2B and2C in conjunction, the exchangeable lubricant and air mixing attachment9of the invention is connectable to or insertible into a socket10C in the housing10. The attachment9comprises three flow restrictors or throttles R1, R2and R3as seen inFIG. 2C. The throttle R1is connected through a conduit or channel8and port8A of the tool housing10to the port P2of the flow control valve V2for supplying lubricant to a mixing area MA. The restrictor R2is connected to the pressurized air conduit5and supplies pressurized air to the mixing area MA. The restrictor R3receives a lubricating mixture from the mixing area MA and feeds the lubricating mixture, preferably through a controllable restrictor DV, to an output9A for feeding lubricating mixture to a cutting location where a cutter engages a workpiece not shown. Preferably a pressure sensor and indicator P2is connected to the output9A.

The throttling or flow restrictors R1, R2and R3are preferably fixed restrictors having a predetermined flow restricting characteristic. According to the invention, exchanging a set of restrictors R1, R2, R3having a predetermined flow restricting characteristic by any set of a plurality of restrictor sets having different flow restricting characteristics, makes it possible to supply a lubricating mixture that is tailored to an exact mixing ratio, to the output9A in compliance with any cutting tool lubricating requirements. The output9A is preferably connected to or communicating with a cooling channel or channels of the cutter in a power tool or machine tool or mobile portable cutting tool not shown.

FIG. 2shows a view of the housing10including conduits or flow channels machined in the housing10and leading to respective ports. The housing10has a first housing section10A and a second housing section10B connected to the first housing section10A by screws in screw holes SH. The second housing section10B is provided with a mounting such as a socket10C for the exchangeable insertion or attachment of a restrictor set9shown inFIG. 2C. The housing10further comprises a port6A leading to the port P1of the valve V2when the valve V2is secured to a sidewall10D of the second housing section10B for example by screws15.

Referring toFIG. 2A, showing an exploded view of the housing10and its components, the first and second housing sections10A,10B are provided with screw holes SH for interconnecting the two housing sections10A and10B. The inlet port4of the air chamber3A is connected to the pressurized air supply conduit5. The housing port6A communicates with valve port P1of the flow control valve V2. A housing port7A communicates with valve port P3. A housing port8A communicates with the valve port P2of the valve V2. As mentioned, using different exchangeable lubricant and air mixing attachments or inserts9with different restrictors R1, R2, R3different dosing ratios are achieved. Further, each restrictor R1, R2, R3may have the same restricting characteristic or different restricting characteristics to achieve the desired lubricant and air mixing volumes and/or mixing ratios and dosing quantities.

In operation in response to a trigger signal at the control input5A the flow control valve V2switches from the filling flow passage shown inFIG. 1for the lubricant such as oil to a discharge flow passage from the chamber3B to the restrictor R1through the valve V2, whereby the valve ports P1and P2communicate with each other. If the tool LT is switched off, the chamber3B is connected through the ports P1and P3of the valve V2to the supply conduit7and thus to the lubricant supply source1A whereby the lubricant is automatically replenished in the chamber3B for the next lubricating operation. The control input5A of the valve V2is preferably connected to the pressurized air conduit5, whereby the valve V2can be switched from the one position to the other position and vice versa by a pneumatic trigger signal. However, other valve trigger signals are possible, for example a mechanical or electrical switch over is possible. As shown inFIG. 1, the ports P1and P3of the valve V2are interconnected, whereby the lubricant is automatically supplied into the chamber3B.