US20100320078A1

US20100320078A1 - Electroerosion spindle assembly

Info

Publication number: US20100320078A1
Application number: US12/797,136
Authority: US
Inventors: Renwei Yuan; Garth M. Nelson; Yuanfeng Luo; Roberto Ciappi; Jun Cai; Yimin Zhan; Ugo Cantelli; Massimo Arcioni
Original assignee: Individual
Current assignee: General Electric Co
Priority date: 2009-06-19
Filing date: 2010-06-09
Publication date: 2010-12-23

Abstract

An electroerosion spindle assembly includes a main shaft, a tool electrode having a rear end directly or indirectly attached to the shaft and in alignment with the main shaft in a longitudinal direction, a container surrounding the main shaft, a stationary-to-rotary electrical conduction device mounted on the container for transitting power energy to the tool electrode, and a channel routing a flushing fluid to a front end of the tool electrode. The channel has at least one flushing slot in the container.

Description

BACKGROUND

This Application claims benefit of U.S. Provisional Patent Application No. 61/218,499 titled “ELECTROEROSION SPINDLE ASSEMBLY”, filed Jun. 19, 2009. The disclosure of the Provisional Application is hereby incorporated by reference in its entirety.
The present invention relates in general to electroerosion tools, and more specifically to an electroerosion spindle assembly.
Electro-Chemical Machining (ECM) and Electrodischarge Machining (EDM) methods use electrical current to remove materials from a workpiece. In ECM operation, a conductive flushing fluid is circulated between an electrode and the workpiece for permitting electrochemical dissolution of the workpiece, as well as cooling and flushing a working gap between the electrode and the workpiece. In EDM operation, a nonconductive flushing fluid is provided in a working gap to permit electrical discharge in the working gap for removing material in the workpiece, as well as for cooling and flushing the working gap. The ECDM process is based partly on spark erosion and partly on electro-chemical removal. As used herein, the term “electroerosion machining” should be understood to apply to those electro-machining processes that use electrical current to remove materials from a workpiece and circulate a flushing fluid in the working gap between the electrode and the workpiece, such as ECM, EDM, Electrochemical Discharging Machining (ECDM) and the like.
There is a need in the art for electroerosion tools that perform electroerosion machining, to be more compact.

BRIEF DESCRIPTION

An aspect of the invention resides in an electroerosion spindle assembly. The electroerosion spindle assembly includes a main shaft, a tool electrode having a rear end directly or indirectly attached to the shaft and in alignment with the main shaft in a longitudinal direction, a container surrounding the main shaft, a stationary-to-rotary electrical conduction device mounted on the container for transmitting power energy to the tool electrode, and a channel routing a flushing fluid to a front end of the tool electrode. The channel has at least one flushing slot in the container.

DRAWINGS

These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

FIG. 1 illustrates a perspective view of an exemplary electroerosion spindle assembly of the invention.

FIG. 2 is a front view of the electroerosion spindle assembly of FIG. 1 with a partially cross-sectional view of a stop block showing internal and external flushing slots in the stop block respectively for internal and external flushing fluid flow.

FIG. 3 is simplified cross-sectional view of the electroerosion spindle assembly along line A-A of FIG. 2.

FIG. 4 is a perspective view of a main sleeve of the electroerosion spindle assembly.

FIG. 5 is a perspective view of an electrical brush of the electroerosion spindle assembly.

FIG. 6 is a perspective view of the main sleeve with one electrical brush and a pair of power connectors mounted thereon.

FIG. 7 is a simplified cross-sectional view of the electroerosion spindle assembly along line B-B in FIG. 2 for showing a channel for internal flushing fluid flow.

FIG. 8 is simplified cross-sectional view of the electroerosion spindle assembly along line C-C in FIG. 2 showing a channel for external flushing fluid flow.

FIG. 9 is a perspective view of a nozzle for external flushing fluid flow.

FIG. 10 is a partial and enlarged cross-sectional view of the electroerosion spindle assembly along line A-A of FIG. 2, illustrating structure of an electrode device of the electroerosion spindle assembly.

FIG. 11 is a perspective view of an electroerosion tool, the electroerosion tool including the spindle assembly of FIG. 1 adapted to a general CNC machine.

DETAILED DESCRIPTION

An exemplary electroerosion spindle assembly 1 is shown in FIGS. 1, 2 and 3. The electroerosion spindle assembly 1 typically includes a main shaft 10 (FIG. 3) that is rotatable around its longitudinal axis thereof, a main sleeve 13 surrounding a rear portion of the main shaft 10, an electrode device 11 connected with the main shaft 10 for performing electroerosion machining, a stationary-to-rotary electrical conduction device for transmitting electrical current from a power source (not shown) to the electrode device 11, and a flushing fluid transmission system for transmitting a flushing fluid to the electrode device 11 during electroerosion machining. The flushing fluid transmission system has at least one flushing slot in the main sleeve 13 which will be discussed in greater detail later.
FIG. 3 is a simplified cross-sectional view of the electroerosion spindle assembly 1 along line A-A of FIG. 2, wherein detailed structure of the electrode device 11 is omitted and discussed in greater detail later. Referring to FIGS. 1-3, the stationary-to-rotary electrical conduction device comprises at least one power connector 12 mounted on the main sleeve 13, for introducing electrical current from the power source to the main sleeve 13, at least one electrical brush 14 contained in the main sleeve 13 and electrically connecting with the main sleeve 13, and an annular shaft sleeve 15 tightly fitted with an outer surface of the main shaft 10 and rotating together with the main shaft 10. The at least one electrical brush 14 contacts with an outer surface of the shaft sleeve 15 for transmitting power to the main shaft 10 and then to the electrode device 11. A plurality of conductive wires 16 are provided between the main sleeve 13 and the electrical brushes 14 for ensuring a reliable electrical connection therebetween.
Each electrical brush 14 is secured in the main sleeve 13 by a cover 18. The cover 18 may be secured with the main sleeve 13 by plurality of bolts (not labeled). A plurality of coils 17 are retained between the cover 18 and the electrical brush 14 for flexibly biasing the electrical brush 14 toward the shaft sleeve 15. In one embodiment, each electrical brush 14 is provided with one corresponding cover 18, and thus the cover 18 does not add to the overall dimension of the main sleeve 13. In other embodiments, only one cover 18 surrounds an outer periphery of the main sleeve 13 for bearing against the coils 17 and retaining the electrical brushes 14 in the main sleeve 13.
In certain embodiments, the electroerosion spindle assembly 1 includes an adaptable extender 100 for the main shaft 10. One end of the extender 100 is secured with a front end of the main shaft 10, and the other end of the extender 100 is secured with a rear end of the electrode device 11. Preferably, the extender 100 is detachably engaged with the main shaft 10 and the electrode device 11, for example, by screwing, and thus the length of the spindle assembly 1 can be changed by adapting different extenders 100 of different lengths. The electrical current is then transmitted from the main shaft 10, through the extender 100, to the electrode device 11. Bearings 19 are retained in a bearing container 131 of the main sleeve 13 for supporting the main shaft 10 to be in alignment to the longitudinal axis during rotating.
The power source can be, for example, a pulsed direct current with an open voltage range from about 30 volts to about 70 volts, and an average current range from about 100 amperes to about 3000 amperes, with the positive potential connected to the workpiece and negative potential connected to the electrode device 11. In alternate embodiments, the polarity is reversed with the positive potential connected to the electrode device 11 and negative potential connected to the workpiece.
Referring to FIG. 4, the main sleeve 13 is in a form of an annular sleeve, and includes a rear brush container 130 with a relatively larger diameter and a front bearing container 131 with a relatively smaller diameter. The brush container 130 includes four cavities 132 evenly distributed in a circumferential direction for containing the electrical brushes 14 therein, and a plurality of holes 133 adjacent each cavity 132 for securing the conductive wires 16 (as shown in FIG. 6). The brush container 130 defines a first internal flushing opening 134 and a first external flushing opening 135 extending therethrough. The first internal and external flushing openings 134, 135 are arranged between two adjacent cavities 132 and will be discussed in greater detail below.
Referring to FIG. 5, the exemplary electrical brush 14 is a carbon brush made from graphite and includes a lower concave surface for matching with a convex outer surface of the shaft sleeve 15, an upper surface of the electrical brush 14 defining a plurality of apertures 141 for retaining and bearing against the coils 17 (as shown in FIG. 3), and a plurality of small securing holes 140 for securing the conductive wires 16.
Referring to FIG. 6, each power connector 12 is mounted on the brush container 130 and between two adjacent cavities 132 for introducing the electrical current from the power source to the main sleeve 13. The electrical brushes 14 are mounted in the corresponding cavities 132 respectively. Each conductive wire 16 has one end connected to a corresponding securing hole 140 of the electrical brush 14 and the other end connected to a corresponding securing hole 133 of the main sleeve 13. Bolts (not shown) can be used for securing opposite ends of the conductive wires 16 in the securing holes 140, 133.
In one exemplary embodiment, the power source provides a current of 2000 amperes. In this example, a plurality of power connectors 12, for example four connectors, are provided for introducing the electrical current and each power connector 12 bears 500 amperes. A plurality of electrical brushes 14, for example four brushes, are mounted on the main sleeve 13 for transmitting electrical signals from the main sleeve 13 to the shaft sleeve 15.
Referring to FIGS. 1 and 2, the electroerosion spindle assembly 1 includes a stop block 20 mounted on the main sleeve 13 and over the first internal and external opening 134, 135. The stop block 20 includes a flushing inlet block 200 that is in the form of a cube. The flushing inlet block 200 defines an L-shaped first internal flushing slot 911 and an L-shaped first external flushing slot 921 therein. The first internal and external L- shaped flushing slots 911, 921 respectively include an internal flush inlet 201 and an external flushing inlet 202 in opposite sides of the flushing inlet block 200, and extend through a bottom surface of the flushing inlet block 200.
FIG. 7 is a cross-sectional view of the electroerosion spindle assembly 1 along line B-B of FIG. 2, showing a channel for internal flushing fluid flow. Referring to FIGS. 4 and 7, the main sleeve 13 defines a second internal flushing slot 912 between two adjacent cavities 132. The second internal flushing slot 912 is substantially in the longitudinal. The first and second internal flushing slots 911 and 912 communicate with each other through the first internal opening 134. The main sleeve 13 further includes an annular groove 913 in an inner surface thereof and communicating with a front-end portion of the second internal flushing slot 912. A pair of seal rings 21 are mounted adjacent to opposites sides of the annular groove 913. The main shaft 10 has a tubular front portion having an inner hollow portion 914, and at least one hole 915 communicating with both the inner hollow portion 914 and the annular groove 913. The extender 100 and the electrode device 11 are tubular and respectively have inner hollow portions 916 and 917 (shown in FIG. 10).
As shown in the dash lines in FIG. 7, an internal flushing fluid flows into the internal flushing inlet 201, through the first internal flushing slot 911 in the stop block 20 and the second internal flushing slot 912 in the main sleeve 13, then flows into the inner hollow portions 914, 916 of the main shaft 10 and the extender 100, and then through the internal hollow portion 917 of the electrode device 11.
In certain embodiments, more than one second internal flushing slot 912 can be defined in the spare spaces of the main sleeve 13, and thus may transmit larger amount of internal flushing fluid, if necessary.
FIG. 8 is a cross-sectional view of the electroerosion spindle assembly 1 along line C-C of FIG. 2, showing a channel for external flushing fluid flow. Referring to FIGS. 4 and 8, the main sleeve 13 defines a second external flushing slot 922 between two adjacent cavities 132. The second external flushing slot 922 is substantially in the longitudinal direction. The second external flushing slot 922 communicates with the first external flushing slot 921 through the first external opening 135.
Referring to FIGS. 1, 2 and 8, the spindle assembly 1 includes an external flushing connector 22 attached to the front end of the main sleeve 13 and surrounds a front portion of the main shaft 10. The external flushing connector 22 may be secured to the main sleeve 13 by some bolts (not labeled). An annular third external flushing slot 923 is defined between the external flushing connector 22 and the main sleeve 13.
A transitional tube 23 is screwed in an inner surface of the external flushing connector 22 and a fourth external flushing slot 924 is defined between the transitional tube 23 and the extender 100 (or the main shaft 10). The third external flushing slot 923 communicates with both the second external flushing slot 922 and the fourth external flushing connector 924.
In certain embodiments, especially for a long main shaft 10 or a long extender 100, an external flushing tube 24 may be used for transmission of the external flushing fluid to the electrode device 11. The external flushing tube 24 is detachably secured to an inner surface of the transitional tube 23 and thus the fourth external flushing slot 924 is defined between the external flushing tube 24 and the extender 100 (or the main shaft 10).
In certain embodiment, as shown in FIGS. 9 and 10, a nozzle 25 is detachably secured on a front end of the external flushing tube 24 or the transitional tube 23 for controlling the external flushing fluid flow. As shown in FIG. 9, the exemplary nozzle 25 includes several slots 250 in the inner surface thereof. The inner surface of the nozzle 25 engages with outer surface of the extender 100, and thus the flushing fluid can only flow through the slots 250.
A second channel for external flushing may be provided for a larger amount of external flushing in high speed electroerosion machining The second channel for external flushing has an additional longitudinal slot in the main sleeve 13 and between two adjacent cavities 132. The additional longitudinal slot has a second external flushing inlet 204 in the brush container 130, as shown in FIGS. 1 and 8. The additional longitudinal slot communicates with the annular groove 923, thus the external flushing fluid flows into the second external flushing inlet 204, then flows through the additional longitudinal slot, and then flows into the annular groove 923.
Referring to FIGS. 1 and 10, the electrode device 11 includes a tubular electrode 110 with a conductive material such as graphite or brass, and a bushing 111 having a front collet 112 secured with the electrode 110 and a rear end 113 detachably attached to the front end of the extender 100, for example by screwing. The bushing 111 can be connected to the electrode 110 by ways of, for example, heat shrink. An insulating protector 114 is provided for surrounding the juncture of the electrode 110 and the bushing 111 for protection purpose. The electroerosion spindle assembly 1 is an adaptable assembly that allows quick changes of the electrode 110 without the need to realign or disassembly the assembly. Different electrode devices 11 of different length can be obtained by adapting different bushings 111 and electrodes 110 of different lengths. Different electrode devices 11 with electrodes 110 of different radiuses can also be obtained by adapting different bushings 111 and electrodes 110 of different radiuses, as if the rear ends 113 are common for engaging with the front end of the extender 100.
Referring to FIG. 11, an exemplary application of the electroerosion spindle assembly 1 to be adapted to a general Computerized Numeral Control (CNC) machine 3 is illustrated. The CNC machine 3 has a stationary flange 30 supporting a rotatable spindle 31. The rotatable spindle 31 normally holds a mechanical milling tool (not shown) as know in the art. The electroerosion spindle assembly 1 includes a tool holder 4 detachably secured with the rotatable spindle 31. The main shaft 10 is electrically insulated from the rotatable spindle 31 by an insulator 5 between the main shaft 10 and the tool holder 4. The stop block 20 may further include an insulative securing rod 203 secured to the stationary flange 30 for retaining the main sleeve 13 and the electrical brush 14 as stationary during rotation of the main shaft 10.
The general CNC machine 3 is often equipped with flushing fluid flow device for cooling cutters and for flushing away etched particles. As shown in FIG. 11, an internal flushing conduit 32 connects the internal flushing inlet 201 and one flushing output on the CNC machine 3, a first and second external flushing conduits 33 respectively connect the first and second external flushing inlets 202, 203 with two flushing outputs of the CNC machine 3. Flushing fluid from the CNC machine 3 flows through the conduits 32, 33 to the electrode 110 through the internal and external flushing channel discussed above. In other embodiments, supplementary flushing fluid supply may be used for providing flushing fluid for providing internal and external flushing fluid.
In another embodiment, the spindle assembly 1 can be an integral part of an electroerosion tool (not shown). In still another embodiment, the spindle assembly 1 is adaptively mounted to a rotating tool spindle of an electroerosion tool for performing electroerosion machining, and thus enable quick replacement of the spindle assembly 1.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Claims

1. An electroerosion spindle assembly includes:

a rotatable shaft;

a tool electrode having a rear end directly or indirectly attached to the shaft and a front end for performing electroerosion machining, the tool electrode being in alignment with the shaft in a longitudinal direction,

a sleeve surrounding the shaft;

a stationary-to-rotary electrical conduction device for transmitting power energy to the tool electrode, the stationary-to-rotary electrical conduction device being mounted on the sleeve; and

a channel routing a flushing fluid to the front end of the tool electrode, the channel having at least one flushing slot in the sleeve.

2. The electroerosion spindle assembly according to claim 1, wherein the sleeve defines at least one cavity for receiving the stationary-to-rotary electrical conduction device therein.

3. The electroerosion spindle assembly according to claim 2, wherein the at least one flushing slot of the channel is defined adjacent to the at least one cavity.

4. The electroerosion spindle assembly according to claim 3, wherein the flushing slot and the cavity are substantially parallel in the longitudinal direction.

5. The electroerosion spindle assembly according to claim 2, wherein the stationary-to-rotary electrical conduction device includes at least one electrical brush electrically connecting with an outer surface of the shaft.

6. The electroerosion spindle assembly according to claim 5, wherein the stationary-to-rotary electrical conduction device includes at least one carbon brush electrically connecting with the outer surface of the shaft.

7. The electroerosion spindle assembly according to claim 6 further comprising at least one coil biasing the carbon brush toward the shaft.

8. The electroerosion spindle assembly according to claim 7, wherein the at least one carbon brush includes at least opening for securing one end of the coil, and wherein a cover is secured to the sleeve and secures the other end of the at least one coil.

9. The electroerosion spindle assembly according to claim 6 further comprising a sleeve tightly surrounding the outer surface of the shaft, the electrical brush contacting with the sleeve.

10. The electroerosion spindle assembly according to claim 1 further comprising a holder at a distal rear end thereof for adapting the spindle assembly to a general CNC machine.

11. The electroerosion spindle assembly according to claim 10 further comprising an insulator for insulating the holder from the shaft.

12. The electroerosion spindle assembly according to claim 1 further comprising a stop block, the stop block including a securing rod for securing the electroerosion spindle assembly to a general CNC machine.

13. The electroerosion spindle assembly according to claim 12, wherein the stop block is secured to the sleeve, and wherein the stop block includes one inlet for the channel.

14. The electroerosion spindle assembly according to claim 1, wherein the channel includes an internal flushing channel and an external flushing channel.

15. The electroerosion spindle assembly according to claim 14, wherein the internal and external flushing channels respectively include flushing slots in the sleeve.

16. The electroerosion spindle assembly according to claim 14, wherein the flushing slots of the internal and external flushing channels are generally parallel in the longitudinal direction.

17. The electroerosion spindle assembly according to claim 1, wherein the shaft and the tool electrode are both tubular with interior hollow portions, the hollow portions of the communicating with the slot of the channel, so as to transmitting flushing fluid to the front end of the electrode through the slot and the hollow portions of the tubular shaft and the tool electrode.

18. The electroerosion spindle assembly according to claim 1 further including a flushing tube surrounding the shaft and defining a circular flushing channel therebetween, a flushing fluid flowing through the circular flushing channel for providing external flushing of the tool electrode.

19. The electroerosion spindle assembly according to claim 18 further including a nozzle at a front portion of the flushing tube.

20. The electroerosion spindle asssembly according to claim 1 further including a bushing, the bushing including a rear end detachably secured to the shaft and front end detachably secured with the tool electrode.