Distal end honing device

Details Distal end honing device Distal end honing device

2001-04-05

2003-07-01

Rose, Robert A. (Department: 3723)

Abrading

Abrading process

Hollow work

C451S504000, C451S051000

Reexamination Certificate

active

06585571

ABSTRACT:

TECHNICAL FIELD
This invention relates generally to honing devices and methods for machining of work pieces, and more particularly to a fluid-activated honing device for finishing work pieces wherein the effective machining diameter of the honing device is adjustable in response to fluid pressure.
BACKGROUND OF THE INVENTION
It is common practice in the machine tool industry to use honing devices for finishing the walls (e.g., removing about 0.001 to 0.005 inches of material) of a previously provided bore hole or similar interior surfaces of a workpiece. Honing operations generally correct inaccuracies in straightness and roundness in bore holes, can provide a generally uniform plateau surface in bore holes, can remove burrs or finish surfaces knurled, or can also provide a desired cross-hatch angle in the finish of the interior machined areas of a workpiece.
In the past, honing devices have generally been constructed with a plurality of symmetrically arranged work engaging assemblies having abrasives (e.g., rigid stones), which are mounted in slots on a device body for movement radially outwardly. Mechanical activation assemblies, such as springs, pusher rods, rack and pinion arrangements, tapers or cam devices, urge the work engaging assemblies, and advance the abrasives to a working position for engagement with a work surface. Also, these assemblies can assist in retracting the work surfaces from the working positions so that the honing device can be more easily removed from the interior of a workpiece. The nature of these assemblies for advancing the abrasives requires frictional engagement between the activation assembly and work engaging assembly, and thus, mechanical friction is generated at the interface. Over time, mechanical friction being continuously and repeatedly generated at this interface alters the inter-workings of these mechanical assemblies due to use (e.g., wear and tear), and thus, compromises the accuracy of the device. Chips from the workpiece can also become lodged in the slots where the work engaging assemblies move radially outwardly from the device, and can even become lodged between the interface of the activation assembly and the work engaging assembly while the work engaging assemblies are radially moved outwardly to their working position, thereby interfering with the operations of the device. Such interference with the operations of the device can inhibit uniform radial expansion of the abrasive, which can also compromise and diminish the honing accuracy, and can cause excessive wear and tear on portions of the abrasive as a result of the work load being unevenly distributed. Moreover, the work engaging assemblies can even become fixed in the working position making removal of the honing device from the workpiece more difficult.
Some prior honing devices, such as illustrated U.S. Pat. No. 2,284,134 to Conner, mount a plurality of stone disposed in slots in an abrading head such that a balanced pressure urges the stones to move radially into a working position. Pistons or other fluid-activated means are used to move the stones outwardly. Since the device contemplates that the stones move away from the slots, recently cut chips can become lodged where the stones are moved radially from the abrading head to their working positions, and thus, can interfere with the operations of the device.
Another prior honing device, such as illustrated in U.S. Pat. No. 5,800,252 to Hyatt, mounts an essentially uninterrupted honing sleeve on a device mandrel. Pressurized fluid applied to the interior surface of the honing member deforms (e.g., activates) the honing sleeve in an axisemetric configuration. Since the honing sleeve is uninterrupted, the greatest range of deformation occurs adjacent the center portion of the device, making honing the inner most portion of a blind hole more difficult.
Other prior honing devices have used a sleeve-shaped configuration with one or more grooves or openings extending through the sleeve. The grooves or openings serve several important and necessary functions in the operation of these honing devices. First, they can provide a key way for guiding the mechanical activation assemblies, as discussed above, so that the activation assembly remains properly aligned as it advances in the desired direction. Secondly, the slots, in conjunction with a key on a device mandrel, can provide a key and groove arrangement for preventing rotation of the sleeve relative to the device mandrel during use.
Other previously available honing devices use suitable fluid pressure as the activation assembly for expanding flaps provided in an outer surface of a cylinder. For example, in U.S. Pat. No. 3,362,113 to Feather, a piece of emery cloth or other flexible abrasive material is wrapped around and secured to a cylinder, and, as the fluid pressure increases in a rubber tube disposed in the cylinder, the fluid pressure expands the flaps, thus, increasing the force between the abrasive surface and the inside surface of a bore hole. If fluid pressure is not properly controlled and rises above a critical level, the very nature of these assemblies allows for continued expansion of the sleeve as the workpiece is worked. Since the ability to control radial expansion of the device is hampered, device accuracy is compromised, and predicting or controlling the radial expansion corresponding to fluid pressure can be difficult and cumbersome.
Another honing device, for example as seen in U.S. Pat. No. 5,085,014 to Sandhoff, has honing rings mounted along the axial surface of a device body in annular grooves, and includes an abrasive layer on the outer periphery. An inner bore is provided within the device body that is adapted to supply coolant from a source to the interior surface of the honing rings for moving the rings into engagement with the bore surface. However, the rings do not uniformly expand in the radial direction. Instead, the rings expand as though uncoiling, whereby certain portions often expand further in the radial direction than other portions, such as those portions where the rings are secured to the device body. The resulting, non-uniform expansion of the device wears much more on certain areas of the abrasive (i.e., where radial expansion is greater) than on other areas. As devices are repeatedly used, accuracy and reliability of the honing device is compromised and the abrasives must often be replaced prematurely.
In almost all machine device operations, including honing, the friction between the device and workpiece generates tremendous amounts of heat energy, which can reach temperatures of 2000° F. (1100° C.) and above. If left uncontrolled, such heat could severely damage (e.g., cracking or fracturing) the device, thus reducing its device life, making machine device operations more dangerous and expensive, and reducing the quality and precision of the workmanship. In addition, heat generated friction can discolor the workpiece, and can damage or remove temper or heat treatments. It is commonly known in the industry that coolant can be introduced to the machining area, such as by spraying, to reduce friction between the device and workpiece by maintaining a thin film of coolant fluid between the cutting device and the workpiece, and to help remove heat energy generated in machine device operations.
Although coolant fluid can be supplied to the honing area, it is often difficult to insure that such fluid actually makes its way to the interstices between the device and all of the workpiece surfaces being machined. Additionally, fluid tends to evaporate quickly due to the high temperatures involved in honing operations. Thus, larger volumes of coolant fluid must generally be continuously supplied to the honing area for the honing device to operate effectively. This need to keep a thin continuous film of coolant fluid between the honing device and wall of the bore hole becomes even more problematic in operations where coolant fluids cannot be introduced in close proximity to the honing areas while the honing device is engaged with the interi

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