An electric spindle with built-in ultrasonic automatic tool changer and its assembly method

Abstract

The present invention provides a built-in ultrasonic automatic tool-changing electric spindle, comprising a housing; a shaft core located in the housing; a conductor located at the center of the shaft core; a tool handle, a pull claw, a pull rod, a disc spring, and a pull rod connecting rod connected in sequence in the shaft core, wherein the tool handle, the pull claw, the pull rod, and the pull rod connecting rod are centrally provided with an inner hole for the conductor to pass through, and the disc spring is set on the pull rod via a disc spring locking nut; a transducer located in the tool handle and electrically connected to the conductor; a cutting ring, which is set on the outer periphery of the shaft core via a cutting pin; and a slip ring rotor, which is in electrical contact with the conductor and is set at the end of the shaft core. The structure of the conductor being located in the center of the shaft core overcomes the centrifugal force generated on the conductor by the high-speed rotation of the shaft core in conventional technologies, and adopts an encapsulation process to encapsulate the connecting signal line between the slip ring and the transducer receiver in the pull rod, thereby solving the problems of damage to the centrifugal force, insulation, and signal instability; not only can fast automatic tool change be achieved, but also the stability of the transmitted signal can be ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of machine tool spindles, and particularly relates to a built-in ultrasonic automatic tool-changing electric spindle and an assembly method thereof. Background Art

[0002] Currently, ultrasonic spindles on the market are generally in the form of ER chucks. The connection line between the signal receiver and the slip ring is not fixed in an ideal way. The high-speed rotation is greatly affected by the centrifugal force, causing a short circuit or unstable signal, which in turn causes damage to the workpiece or out-of-tolerance scrapping. Summary of the Invention

[0003] To address the shortcomings of the prior art, the present invention provides a built-in ultrasonic automatic tool change electric spindle and its assembly method. In the prior art, because the guide connecting the rear-end slip ring rotor to the transducer inside the front-end automatic tool changer handle is partially located outside the shaft core, at high speeds, the centrifugal force on the wire is very large, and the wire is easily damaged by the centrifugal force. Furthermore, due to multiple tool changes, the guide may also become entangled or broken, affecting signal transmission in the short term and potentially causing irreparable damage in the long term. To address this problem, the present invention provides a solution in which the wire is located on the center axis as the live wire and the housing as the neutral wire.

[0004] As a first aspect of the present invention, there is provided a built-in ultrasonic automatic tool-changing electric spindle, comprising a housing;

[0005] a shaft core located within the housing;

[0006] The conductor is located at the center of the shaft core;

[0007] The shaft core is sequentially connected with a tool handle, a pull claw, a pull rod, a disc spring, and a pull rod connecting rod. The tool handle, the pull claw, the pull rod, and the pull rod connecting rod are centrally provided with an inner hole for the wire to pass through, and the disc spring is provided on the pull rod.

[0008] a transducer, located in the shank and electrically connected to the wire;

[0009] A beating ring is arranged on the outer periphery of the shaft core through a beating pin;

[0010] The slip ring rotor is in electrical contact with the conductor and is located at the end of the shaft core.

[0011] This structure connects all the components between the slip ring rotor and the pull claw, namely the pull rod, disc spring, disc spring locking nut, pull rod connecting rod, knife pin and knife ring in series by passing the wire through the inner holes of each component. The wire is insulated from the above components and is located in the center of the shaft to avoid being affected by centrifugal force.

[0012] Preferably, the motor is arranged between the shaft core and the housing as a power supply mechanism.

[0013] Preferably, a cylinder is provided at the end of the spindle core, the cylinder body of the cylinder being fixed to the housing. The piston provided inside, under the action of hydraulic oil, pushes the cutting ring to move the pull rod, and cooperates with the disc spring to realize the removal and installation of the tool. In this structure, the cylinder is built into the electric spindle, saving space and cost.

[0014] Preferably, the adjusting gasket is arranged between the pulling claw and the pulling rod.

[0015] Preferably, the slip ring rotor is provided with a first insulating member fixed to the shaft core, and the inner end of the slip ring rotor is in electrical contact with the copper wire; a second insulating member is provided on the shell, the first insulating member and the second insulating member are coaxial, a carbon brush is provided at the inner end of the second insulating member, which is in electrical contact with the slip ring rotor in the first insulating member, and the outer end is connected to the external wire; a third insulating member for accommodating a fixing screw is provided on the second insulating member, and the fixing screw connects the second insulating member and the shell.

[0016] Preferably, in order to achieve insulation of the wire path, a first insulating layer is provided between the wire and the knife handle, a second insulating layer is provided between the wire and the pull claw, and a third insulating layer is provided between the wire and the pull rod and the pull rod connecting rod.

[0017] Preferably, the first insulating layer, the second insulating layer and the third insulating layer are all made of insulating material epoxy resin, and are insulated and fixed by potting.

[0018] In order to achieve normal assembly, a symmetrical U-shaped notch is set on the shaft core. At the U-shaped notch, the pull rod connecting rod is inserted into the shaft core, and the shaft core is covered with a cutting ring. Through holes for the cutting pin to pass through are set on the cutting ring and the pull rod connecting rod. The cutting pin passes through the cutting ring and the pull rod connecting rod to limit both.

[0019] Preferably, the tool handle is provided with an internal spring device, comprising a rivet, a cavity defined within the rivet, and a rivet internal spring and a contact block disposed within the rivet cavity. The contact block is located at the end of the rivet, and the rivet internal spring is located within the rivet cavity within the contact block, exerting an outward thrust on the contact block, thereby ensuring contact between the end face of the rivet and the front face of the claw when the tool handle is released during tool change. During tool change, the guide can connect to an ultrasonic transducer within the tool handle, thereby realizing an automatic tool change ultrasonic electric spindle. The contact block is provided with a limiting notch, which is limited in position by a limiting bolt disposed on the side wall of the rivet.

[0020] As a second aspect of the present invention, there is provided a method for assembling a built-in ultrasonic automatic tool-changing electric spindle, the steps of which are as follows:

[0021] Step 1: First install the disc spring on the pull rod, lock the disc spring with the locking nut, and then install it into the inner hole of the shaft core, adjust it to the allowable range of tension and broaching amount, and then install the pull rod connecting rod into the shaft core, and then put the cutting ring on the U-shaped notch on the shaft core, install the cutting pin through the cutting ring and the shaft core, and the radial hole of the pull rod connecting rod, and fix it with a pin and a screw to ensure the coaxiality of the inner hole of the cutting ring and the outer circle of the shaft core, as the first component;

[0022] Step 2: Remove the first component assembled in step 1 from the shaft core, pass the wire through the inner hole of the first component, and extend a portion of both ends to form a pre-assembled whole;

[0023] Step 3: Fill the liquid insulating material into the central inner hole of the pre-assembled integral body, and form an insulating potting after solidification. The front end of the potting integral body is connected to the pulling claw, and the rear end is connected to the slip ring rotor.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) The present invention provides a structure in which the conductor is located at the center of the shaft core, overcoming the centrifugal force generated by the high-speed rotation of the shaft core on the conductor in conventional technology. A potting process is used to pot the connecting signal line between the slip ring and the transducer receiver in the pull rod, solving the problems of damage caused by centrifugal force, insulation and signal instability. It can not only realize fast and automatic tool change, but also ensure the stability of the transmitted signal.

[0026] 2) The present invention provides a U-shaped notch at the end of the shaft core, which solves the assembly problem caused by the central structure of the wire and has the characteristics of rapid replacement and convenient maintenance.

[0027] 3) The oil cylinder provided by the present invention is a built-in electric spindle, which saves space and cost, and can also make full preparations for subsequent installation on a robot arm. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0029] Figure 1 This is a schematic diagram of the overall structure of a built-in ultrasonic automatic tool-changing electric spindle provided in Example 1 of the present invention;

[0030] Figure 2 Schematic diagram of the shaft core structure;

[0031] Figure 3 This is a schematic diagram of the knife ring structure;

[0032] Figure 4 This is a schematic diagram of the spring device structure in the handle.

[0033] 1-shaft core, 2-tool handle, 3-pull claw, 4-adjusting gasket, 5-pull rod, 6-motor, 7-housing, 8-disc spring, 9-disc spring locking nut, 10-pull rod connecting rod, 11-knife pin, 12-knife ring, 13-oil cylinder, 14-piston, 15-slip ring rotor, 16-transducer, 17-copper wire, 18-U-shaped notch, 19-first insulating member, 20-second insulating member, 21-third insulating member, 22-first insulating layer, 23-second insulating layer, 24-third insulating layer;

[0034] 201-spring device in the handle;

[0035] 2011-pull nail, 2012-handle inner spring, 2013-contact block, 2014-limiting notch;

[0036] 301-Pull claw petal. DETAILED DESCRIPTION

[0037] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0038] The technical solution of the present invention is not limited to the specific implementation methods listed below, but also includes any reasonable combination of the specific implementation methods.

[0039] Example 1: A built-in ultrasonic automatic tool change electric spindle

[0040] like Figure 1 As shown, it includes a shaft core 1, a tool handle 2, a pull claw 3, an adjusting gasket 4, a pull rod 5, a motor 6, a housing 7, a disc spring 8, a disc spring locking nut 9, a pull rod connecting rod 10, a knife pin 11, a knife ring 12, an oil cylinder 13, a piston 14, a slip ring rotor 15, a transducer 16 and a copper wire 17. The position of the inner hole of the axis of the electric spindle must be guaranteed to be through. In order to solve the influence of factors such as centrifugal force on the wire, the first major feature of the patent of this invention is to connect all the components between the slip ring rotor 15 and the pull claw 3 (pull rod 5, disc spring 8, disc spring locking nut 9, pull rod connecting rod 10, knife pin 11, knife ring 12) in series with a copper wire 17 passing through the inner holes of each component, and the gap is filled with insulating material epoxy resin as the potting material, and no relative displacement can occur after connection.

[0041] The copper conductor is the 3mm copper wire with yellow planed surface on the main shaft busbar.

[0042] Specifically, the motor 6 is disposed outside the shaft core 1 and is located within the housing 7. The oil cylinder 13 and piston 14 are located at one end of the slip ring rotor 15, and the transducer 16 is located at the other end. The tool handle 2, pull claw 3, adjustment washer 4, pull rod 5, disc spring 8, and pull rod connecting rod 10 are sequentially disposed between the transducer 16 and the slip ring rotor 15 and within the shaft core 1. The disc spring 8 is disposed between the pull rod 5 and the pull rod connecting rod 10 via the disc spring locking nut 9.

[0043] The adjusting gasket 4 is arranged between the pulling claw 3 and the pulling rod 5. Because the disc spring needs to be installed in advance to seal the pulling rod, the knife ring, the pulling rod connecting rod and other parts, the adjusting gasket 4 can be adjusted when the pulling force, the pulling amount and the loosening amount need to be finely adjusted. In addition, the connection depth between the external thread on the pulling claw and the internal thread of the pulling rod can also be adjusted using the adjusting gasket 4.

[0044] A cutting ring 12 is provided on one end of the shaft core 1 outside the slip ring rotor 15 , and the cutting ring 12 is fixed by a cutting pin 11 .

[0045] Part of the copper wire 17 is located in the transducer 16 and the tool handle 2, and the other part is located in the inner hole of the central axis between the pull claw 3, the pull rod, and the pull rod connecting rod, and is finally electrically connected to the slip ring rotor 15. The structure provided by the present invention achieves the effect of the copper wire 17 being linearly connected by the transducer 16 and the slip ring rotor 15.

[0046] As a typical embodiment, the handle 2 is provided with a spring device 201 inside the handle, because there is a 5.5mm gap between the end face of the rivet and the front face of the claw when the handle is tightened. Figure 4 As shown, the inner spring device of the tool handle includes a pull nail 2011, and a cavity is set in the pull nail 2011, which is not only used to pass the copper wire 17, but also used to accommodate the tool handle inner spring 2012 and the contact block 2013 set inside the pull nail 2011. The contact block 2013 is located at the end of the pull nail 2011, and is provided with a limiting notch 2014. It is limited by a limiting bolt 2015 set on the side wall of the pull nail 2011. The tool handle inner spring 2012 is located in the cavity of the pull nail on the inner side of the contact block 2013, and applies an outward thrust to the contact block 2013, so that the end face of the pull nail 2011 and the front end face of the pull claw are in contact when the tool is changed and the tool handle is released. When changing the tool, the guide can be connected to the ultrasonic transducer in the tool handle, thereby realizing automatic tool changing of the ultrasonic electric spindle.

[0047] A first insulating member 19 is provided outside the slip ring rotor 15, and the inner end is in electrical contact with the copper wire; the first insulating member 19 is fixed to the shaft core by screws; a second insulating member 20 is provided on the shell 7, and the first insulating member 19 and the second insulating member 20 are coaxial, and a spring structure similar to the spring device in the knife handle is provided inside the second insulating member 20, and a carbon brush is provided at the inner end, which is in electrical contact with the slip ring rotor 15 in the first insulating member 19, and the outer end is connected to the external wire; a third insulating member 21 for accommodating a fixing screw is provided on the second insulating member 20, and the fixing screw connects the second insulating member and the shell 1.

[0048] The present invention uses the copper wire inside the shaft core and the slip ring rotor as the live wire, and the transducer housing and the shell 1 as the neutral wire, and the two are insulated.

[0049] In order to achieve insulation of the copper wire 17 path, a first insulating layer 22 is set between the copper wire 17 and the knife handle 2, a second insulating layer 23 is set between the copper wire 17 and the pull claw 3, and a third insulating layer 24 is set between the copper wire 17 and the pull rod 5 and the pull rod connecting rod 10. The first insulating layer 22, the second insulating layer 23 and the third insulating layer 24 are all insulating materials epoxy resin, and are fixed by potting insulation (green planed line in the figure). The pull rod and the connecting wire are formed into one body, thereby ensuring that the connecting wire is not affected by centrifugal force. Because the components connected in series by the potted connecting wire (yellow copper wire) include the pull rod connecting rod 10 inside the shaft core, the knife ring 12 outside the shaft core, and the knife pin 11 that passes through the shaft core, the overall potting must first connect and fix these accessories of different dimensions.

[0050] Since some of the components connected in series are inside the shaft core 1, some are outside the shaft core 1, and some pass through the shaft core 1, it is almost impossible to complete normal assembly. The second major feature of the present invention is to solve this difficulty caused by the first feature. The shaft core 1 is milled from the middle starting from the position where the cutting ring 12 is installed to the end part, so that the potting assembly connected in series can be placed inside the shaft core 1.

[0051] As an implementation scheme, Figures 2-3 As shown, a symmetrical U-shaped notch 18 is milled into the shaft core 1 to facilitate assembly. A tie rod 10 is inserted into the shaft core 1 at the U-shaped notch 18. A cutting ring 12 is placed over the shaft core 1. Both the cutting ring 12 and the tie rod 10 have through-holes for a cutting pin 11 to pass through. The cutting pin 11 penetrates both the cutting ring 12 and the tie rod 10 to limit the position of both.

[0052] like Figure 1As shown, the oil cylinder 13 is arranged at the end of the shaft core, the cylinder body of the oil cylinder 13 is fixed on the housing 7, and a boss is set at the contact position between the piston 14 arranged inside and the knife ring. Under the action of hydraulic oil, the knife ring 12 is pushed to drive the pull rod connecting rod 10 to move, so that the claw petal 301 of the claw 3 is loosened to loosen the tool and complete the disassembly of the tool; when the tool is installed, the tool is placed in the claw 3, the disc spring 8 pushes the piston 14 to reset, and the claw petal 301 clamps the tool to complete the installation of the tool.

[0053] In this structure, the oil cylinder is built into the electric spindle, which saves space and cost, and also makes full preparation for subsequent installation on the robot arm.

[0054] As a typical embodiment, the handle 2 is provided with a spring device 201 inside the handle, because there is a 5.5mm gap between the end face of the rivet and the front face of the claw when the handle is tightened. Figure 4 As shown, the inner spring device of the tool handle includes a pull nail 2011, and a cavity is set in the pull nail 2011, which is not only used to pass the copper wire 17, but also used to accommodate the tool handle inner spring 2012 and the contact block 2013 set inside the pull nail 2011. The contact block 2013 is located at the end of the pull nail 2011, and is provided with a limiting notch 2014. It is limited by a limiting bolt 2015 set on the side wall of the pull nail 2011. The tool handle inner spring 2012 is located in the cavity of the pull nail on the inner side of the contact block 2013, and applies an outward thrust to the contact block 2013, so that the end face of the pull nail 2011 and the front end face of the pull claw are in contact when the tool is changed and the tool handle is released. When changing the tool, the guide can be connected to the ultrasonic transducer in the tool handle, thereby realizing automatic tool changing of the ultrasonic electric spindle.

[0055] The patent of the present invention has a built-in ultrasonic automatic tool changing electric spindle. The slip ring rotor 15 is installed at the rear end of the shaft core. With the help of the inner hole straight mouth and the rear end screw hole at the rear end of the shaft core, the rotor of the slip ring can be designed to be thinner and the installation is more stable, thereby reducing the linear speed of the slip ring, and more fully realizing the high speed life of the slip ring and stable transmission signal. The speed can reach 70,000 rpm. The slip ring stator and rotor are electrically conductive through carbon brushes. Carbon brushes are consumables. The slip ring stator is installed at the rear end, which is easy to disassemble and has a positioning straight mouth. The repeated installation positioning accuracy is high, and it has the characteristics of quick replacement, easy maintenance, and high stability.

[0056] Example 2: Assembly method of an electric spindle with a built-in ultrasonic automatic tool changer

[0057] First install the disc spring on the pull rod, lock the disc spring with the locking nut, and then install it into the inner hole of the shaft core, use a dynamometer to measure the broaching force, broaching amount, loosening amount and other data, and adjust the number of disc springs and the teaming method to achieve the allowable range of tension and broaching amount, and then connect the pull rod connecting rod together through threads and straight mouths, fix it with a top screw, and install it into the shaft core, and then put the cutting ring on the shaft core, install the cutting pin through the cutting ring and the shaft core, and the radial hole of the pull rod connecting rod, and fix it with a pin and a top screw, so as to ensure the coaxiality of the inner hole of the cutting ring and the outer circle of the shaft core, and then connect the pull rod, disc spring, and disc spring locking nut. The whole assembly consisting of the nut, tie rod connecting rod, knife pin and knife ring is taken out from the shaft core. The hard copper wire is passed through the central inner hole of the whole assembly consisting of the tie rod and tie rod connecting rod, with both ends protruding a few millimeters as a pre-assembled whole. The liquid insulating material is then filled into the central inner hole of the pre-assembled whole. After solidification, the insulation potting is achieved. The front end of the potted whole is connected to the pull claw and the rear end is connected to the slip ring rotor. These accessories rotate relatively statically with the shaft core. The last end is connected to the carbon brush. The carbon brush rotates relative to the shaft core and is relatively static with the shell. The carbon brush part is a spring structure. Because the relative rotation of the carbon brush will cause friction. Friction will cause wear, so the spring structure can ensure that the carbon brush and the slip ring rotor are always in contact and energized. The other end of the carbon brush is connected to the No. 1 port of the aviation plug, and the No. 2 port of the aviation plug is connected to the shell connection line.

[0058] To prevent contamination of the shaft core during the potting process, a shaft core mold can also be used. Before potting, the pre-assembled body is placed in the shaft core mold, and then liquid insulation material is filled into the central inner hole of the pre-assembled body. After solidification, the insulation potting is completed and the potted body is removed from the shaft core mold and installed in the shaft core.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A built-in ultrasonic automatic tool changing electric spindle, characterized in that: including a housing; a shaft core located within the housing; Copper conductor, located at the center of the shaft core; The shaft core is sequentially connected with a tool handle, a pull claw, a pull rod, a disc spring, and a pull rod connecting rod. The tool handle, the pull claw, the pull rod, and the pull rod connecting rod are centrally provided with an inner hole for the copper wire to pass through, and the disc spring is provided on the pull rod. All components between the slip ring rotor and the claw, including the pull rod, disc spring, disc spring lock nut, pull rod connecting rod, knife pin, and knife ring, are connected in series with copper wires passing through the inner holes of each component. The gap is filled with insulating epoxy resin as the potting material. No relative displacement can occur after connection. The transducer is located in the handle and is electrically connected to the copper wire; A beating ring is arranged on the outer periphery of the shaft core through a beating pin; The slip ring rotor is in electrical contact with the copper conductor and is located at the end of the shaft core; The slip ring rotor is provided with a first insulating member fixed to the shaft core, and the inner end of the slip ring rotor is in electrical contact with the copper wire; a second insulating member is provided on the housing, and the first and second insulating members are coaxial. A carbon brush is provided on the inner end of the second insulating member, which is in electrical contact with the slip ring rotor in the first insulating member, and the outer end is connected to the external copper wire; a third insulating member is provided on the second insulating member for accommodating a fixing screw, and the fixing screw connects the second insulating member and the housing; A symmetrical U-shaped notch is provided on the shaft core. At the U-shaped notch, the pull rod connecting rod is inserted into the shaft core. The shaft core is covered with a knife ring. Through holes for the knife pin to pass through are provided on the knife ring and the pull rod connecting rod. The knife pin passes through the knife ring and the pull rod connecting rod to limit the two. The knife handle is provided with an inner spring device, which includes a pull nail, a cavity is provided in the pull nail, and a knife handle inner spring and a contact block are provided inside the pull nail cavity. The contact block is located at the end of the pull nail, and the knife handle inner spring is located in the cavity of the pull nail inside the contact block, applying an outward thrust to the contact block.

2. The built-in ultrasonic automatic tool-changing electric spindle according to claim 1, characterized in that: The motor is arranged between the shaft core and the housing and serves as a power supply mechanism.

3. The built-in ultrasonic automatic tool-changing electric spindle according to claim 1, characterized in that: An oil cylinder is arranged at the end of the shaft core, the cylinder body of the oil cylinder is fixed on the shell, and the piston arranged inside pushes the cutting ring to drive the pull rod to move under the action of hydraulic oil.

4. The built-in ultrasonic automatic tool-changing electric spindle according to claim 1, characterized in that: The adjusting gasket is arranged between the pulling claw and the pulling rod.

5. The built-in ultrasonic automatic tool-changing electric spindle according to claim 1, characterized in that: A first insulating layer is provided between the copper wire and the knife handle, a second insulating layer is provided between the copper wire and the pulling claw, and a third insulating layer is provided between the copper wire and the pulling rod and the pulling rod connecting rod.

6. The built-in ultrasonic automatic tool-changing electric spindle according to claim 5, characterized in that: The first insulating layer, the second insulating layer and the third insulating layer are all made of insulating material epoxy resin and are insulated and fixed by potting.

7. The built-in ultrasonic automatic tool-changing electric spindle according to claim 1, characterized in that: The contact block is provided with a limiting notch and is limited by a limiting bolt provided on the side wall of the rivet.

8. The method for assembling a built-in ultrasonic automatic tool-changing electric spindle according to any one of claims 1 to 7, characterized in that: The steps are: Step 1: First install the disc spring on the pull rod, lock the disc spring locking nut, and then install it into the inner hole of the shaft core, adjust it to the allowable range of tension and broaching amount, and then install the pull rod connecting rod into the shaft core, and then put the cutting ring on the U-shaped notch on the shaft core, install the cutting pin through the cutting ring and the shaft core, and the radial hole of the pull rod connecting rod, and fix it with a pin and a screw to ensure the coaxiality of the inner hole of the cutting ring and the outer circle of the shaft core, as the first component; Step 2: Remove the first component assembled in step 1 from the shaft core, pass the copper wire through the inner hole of the first component, and extend a portion of both ends to form a pre-assembled whole; Step 3: Fill the liquid insulating material into the central inner hole of the pre-assembled integral body, and form an insulating potting after solidification. The front end of the potting integral body is connected to the pulling claw, and the rear end is connected to the slip ring rotor.

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