US 3115454 A
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1963 P. J. ROBISCHUNG ET AL 3,115,454
ELECTROLYTIC GRINDING MACHINE Filed Jan. 3, 1961 INVENTORS Philip J. Robischung BY Donald E. Sufron a Q, M... M wag ATTORNEYS United States Patent 3,115,454 ELECTROLYTIC GRINDING MACHINE Phiiip J. Robischung, Kalamazoo, and Donald E. Sutton,
Cornstock Township, Kalamazoo County, Mich, as-
signors to Hammond Machinery Builders, Inc., Kalamazoo, Mich., a corporation of Michigan Filed Jan. 3, 1961, Ser. No. 80,378 2 Claims. (Cl. 204-424) This invention relates to an electro-decomposition, metal-removal machine and it relates particularly to means for supplying an electric potential of constant polarity to the spindle of such a machine wherein said spindle also carries the armature of an induction-type, driving motor.
The present invention was developed in connection with electrolytic grinding machines and, accordingly, both the specific problem involved and the solution for same will be discussed in connection with such machines. However, it will be recognized that the principles of the invention will be applicable to other types of apparatus, especially metal cutting apparatus, and, accordingly, the use of the specific example mentioned will be recognized as illustrative only, not limiting.
In the design of electrolytic grinding machines it has been found desirable to utilize the spindle upon which a grinding wheel is mounted as the support for the armature of the driving motor. This has advantages which are well known in the art. Particularly, these advantages include economy of space, elimination of driving mechanism connecting the motor to such spindle and minimizing the number of running parts which require care and maintenance This type of construction is used for both single end and double end grinding machines, that is, machines having one grinding wheel at one end of the spindle and machines having two grinding wheels mounted at opposite ends of the spindle.
When such a construction is used on an electro-decomposition type of metal-removal machine, it is necessary to apply a potential of constant polarity to the spindle so that the potential is applied to the metal-removal tool, such as a grinding wheel which is electrically conductive except for the abrasive grain, which wheel is used for electrolytic grinding. This arrangement first raises the problem of providing ample protective insulation between the field windings of the motor and the spindle in order to protect the operator from the A.C. potential applied to the field windings, normally 220 or 440 volts, in the event of a breakdown in the field winding insulation.
In addition, there is the problem of providing the proper point and manner of application of the DC. potential to the spindle. Where only a single end grinding machine is used, this presents no great difiiculty inasmuch as the DC potential can be applied to the spindle by conventional slip ring means located at the opposite end of the spindle from the grinding wheel. However, for double ended grinding machines, this technique is not available because the space otherwise occupied by the slip ring must now be utilized for the second grinding wheel. In order to minimize deflection, the grinding wheel should be placed as close as possible to the bearings and, therefore, it is not desirable to place the slip ring between a spindle bearing and the grinding wheel. To place another bearing outwardly of the motor bearings in order to have a bearing support closely adjacent to the wheel is likewise undesirable because it adds to the expense of the machine and increases the overall length.
Accordingly, the objects of the invention include the following:
(1) To provide a spindle support and drive mechanism adaptable for driving an electrical cutting tool, such as a "ice grinding wheel used in electrolytic grinding wherein said spindle carries the armature of the driving motor and wherein means are provided for applying a DC. potential to the spindle at a point between the motor bearings and electrically insulated from the field windings.
(2) To provide a spindle support and driving mechanism, as aforesaid, wherein the end bells supporting the motor bearings are suitably insulated from the central housing supporting the field windings to provide protection of the machine operator in the event of breakdown of the field winding insulation. Such insulation also serves to isolate the A.C. and DC. potentials from each other and particularly prevents the D.C. potential used for the electrolytic operation from leaking to ground through the central housing.
(3) To provide a spindle support and driving mechanism, as aforesaid, in which the spindle bearing adjacent the source of DC. potential is insulated from the end bell by which it is supported to eliminate flow of current through the bearing and consequent etching thereof.
(4) To provide a spindle support and driving mechanism, as aforesaid, including means for applying a DC. potential to the spindle at a point thereon between the field windings of the motor and one of the spindle bearmgs.
(5) To provide a spindle support and driving mechanism, as aforesaid, which is compact and space-saving and which can be manufactured at minimum cost.
(6) To provide a spindle support and driving mechanism, as aforesaid, which will be of maximum simplicity and which will require a minimum of changes from the motor construction previously used for nonelectrolytic apparatus.
(7) To provide a spindle support and driving mechanism, as aforesaid, which can be readily changed from an electrolytic application to a conventional or nonelectrolytic application or vice versa with a minimum number of changes in the parts of the mechanism.
(8) To provide a spindle support and driving mechanism, as aforesaid, which will be effective and capable of long operation with relatively little maintenance.
Other objects and purposes of the invention will be apparent to persons acquainted with devices of this general type upon reading the following specification and inspecting the accompanying drawings.
FIGURE 1 is an end, elevational view of the spindle and motor unit embodying the invention.
FIGURE 2 is a sectional view taken on the line IIH of FIGURE 1.
General Description The invention comprises placing a brush and slip ring assembly within a suitable extension of one of the end bells of the motor housing between the bearing carried by said end bell and the field windings. An insulating ring is placed between each end bell and an adjacent end of the cylinder defining the central part of the motor housing within which the field windings of the motor are mounted. Thus, a breakdown in the insulation of said field windings will not apply the field winding potential onto the end bells or the grinding wheel spindle. When the motor is to be used with a conventional grinder, it is necessary only to change the end bell carrying the brush and slip ring assembly and replace same with a conventional end bell. In such case, the insulation between the end bells and the central casing may be removed or retained as desired.
Detailed Description Referring now to the drawings, there is shown a motor housing comprising a pair of end bells 2 and 3 and a central cylindrical casing 4 located between said end bells and secured thereto. Rings 5 and 10 of electrical insulating material insulate the end bells 2 and 3 from the casing 4. A plurality of field windings 6 for the usual introduction type or squirrel-cage motor are mounted on and within the casing 4. In use, the casing 4 will ordinarily be grounded for protection of the operator. The rings 5 and serve to insulate the A.C. potential on the field windings from the DC). potential applied on the end bells 2 and 3 as hereinafter described, and serve to insulate said end bells from the ground connection provided by the casing 4.
The end bell 2 includes a section 7 which is substantially cylindrical and preferably of the same outside diameter as that of the cylindrical casing 4. Said portion 7 is connected by a radially arranged wall 8 to a further cylindrical section 9 within which are mounted suitable bearings, here the ball bearing units 11 and 12. Sealing means 13 of any convenient type, here shown as being of the interfitting flange and groove type, are provided at the outboard end of the section 9 to prevent entry of grinding fluid and/ or grinding dust into the above mentioned bearings.
The end hell 3 comprises a generally cylindrical section 14 generally similar to the section 7 of the end bell 2 but being of somewhat greater axial length. Further, the section .14 has three radially extending tubular openings 16, 16a and 16b therein (FIGURE 1). Said end bell 3 also has a radial wall 17 connecting the cylindrical section 14 with a further cylindrical section 18 of reduced diameter. Bearing means 19, here a ball bearing assembly, is supported within section 18. An insulating sleeve 21 surrounds the bearing means 19 and insulates same from the end bell 3. This prevents flow of current (bypassing the hereinafter-menti-oned brush and slip ring assembly) through the bearing means which might otherwise cause etching of the bearing balls and/ or the races and thereby destroy the bearing. This is a serious problem for the bearing located adjacent the slip ring and brush assemblies, hereinafter described, but it is not a problem for the bearing units ill and 12 in the end hell 2, in view of the insulation between end bell 2 and easing 4. Therefore, it is not necessary to use an insulating sleeve around these latter bearings.
A further sealing assembly 24 of any convenient type, here shown as being of the interfitting flange and groove type, is provided outwardly of the section 18 to prevent entry of grinding fluid and/or grinding dust into the bearing 19.
A rotor 25 is disposed within the field windings 6 in the manner customary for induction motors so that energization of said field windings will eflect rotation of said rotor. The rotor 25 has a spindle 26 secured thereto and extending therethrough and beyond both axial ends thereof. One end portion of the spindle 26 extends through and is supported by the bearings 11 and 12 while the other end portion extends through and is supported by the bearing 19. Grinding wheels 27 and 28 are mounted on the respective axial ends of the spindle 26. The spindle 26 and rotor 25 serve as the armature of the motor which includes the field windings 6. Thus, energization of the field windings will rotate the spindle 26 and thereby rotate the grinding wheels 27 and 28.
An electrically conductive slip ring 31 is secured to the spindle 26- and is located within the section 14 between the bearing 19 and the adjacent end of field winding 6. Brush units 32, 32a and 32b are disposed in the radial openings 16, 16a and 16b, respectively. Since the brush units are substantially identical, only unit 32, which is disposed in opening 16, will be described in detail herein. It will be understood that this description applies also to the other brush units. Brush unit 32 includes a brush 33 slidable within opening 16 and having an arcuate inner edge slidably engageable with the periphery of slip ring 31. A conductor 34 is secured to the brush 33 and extends outwardly through a central opening in the plug 36. A spring 37 surrounds the conductor 34 and bears at its inner end against the outer edge of brush 33 to continuously urge same against the slip ring 31. The outer end of spring 37 bears against a shoulder within the plug 36.
The conductors 34 and 34a of the brush units 32 and 32a are connected to a terminal post 41. The negative side of a source of DC. potential is connectible to the post 41 while the positive side thereof is connectible to the workpieces as is conventional in electrolytic grinding procedures. Thus, the brush units 32 and 320 are intended to supply electrical potential for the spindle 26 and thereby to the grinding wheels 27 and 28.
The conductor 34b of the brush unit 32b is connected to a terminal post 42. A conductor (not shown) may connect the post 42 to the electric current control unit (not shown) which controls the amperage flowing through the spindle so that the proper amperage will flow through the spindle, all in accordance with conventional electrolytic grinding practice.
In use, A.C. potential applied to the field windings 6 will eifect rotation of the spindle 26 and thereby rotation of the grinding wheels 27 and 28. Electrical energy supplied to post 41 will travel through conductors 34 and 34a, thence through brushes 33 and 33a, the slip ring 31 and the spindle 26 to the grinding wheels 27 and 28. The insulating rings 5 and '10 isolate the end bells 2 and 3 from the casing 4 so that the A.C. potential applied to windings 6 will be isolated trom the D0 which is applied to the end bells and further, prevents the A.C. potential applied to the field windings, which is usually 220 or 440 v. A.C., from being applied to the end bells if the insulation of the field windings should fail. While the end bells will carry DC. potential applied through the brushes 33 and 33a, this is of a low voltage and cannot harm the operator if he should touch said end bells. The insulating sleeve 21 will prevent the DC. potential on end bell 3 from passing through the bearing 19.
If it should become desirable to convert the motor to use as a non-electrolytic grinder the same can easily be done by replacing the end bell 3 with another end bell corresponding to end hell 2 or its equivalent.
While a particular, preferred embodiment of the invention has been described in detail, the invention contemplates changes or modifications thereof which lie within the scope of the appended claims.
What is claimed is:
1. Apparatus for removing metal by an electrolytic process, the combination comprising:
an electric motor including an intermediate housing section having a stator mounted therein;
a rotor mounted within said stator;
a solid spindle connected to said rotor and extending beyond the ends thereof and beyond the ends of said intermediate housing section;
a first housing end section having a bearing mounted therein, first insulation means between said first housing end section and said intermediate housing section, said first end section being fixed to but electrically insulated from said intermediate section, said spindle being rotatably supported adjacent one end thereof by said bearing and extending through and beyond said first end section;
a second housing end section having a second bearing mounted therein, second insulation means between said second housing end section and said intermediate housing section, third insulation means between said second housing end section and said second bearing, said second end section being fixed to but electrically insulated from said intermediate section, said spindle being rotatably supported adjacent its other end by said second bearing and extending through and beyond said second end section;
an electrically conductive slip ring within said second end section and secured to said spindle between said second bearing and the adjacent end of said stator,
said slip ring being electrically connected to said spindle but being free of electrical connection to the windings of said motor;
a brush mounted in said second end section and means urging same into sliding contact with said slip ring;
a source of DC. potential and means connecting one terminal of same to said brush, the other terminal thereof being adapted for connection to the work pieces to be ground, said second bearing being insulated from flow of electrical energy therethrough by said third insulation means; and
means for securing electrolytic grinding wheels to the respective ends of said spindle with at least one grinding wheel on said spindle.
2. An apparatus for removing metal by an electrolytic grinding process, the combination comprising:
an electric motor casing and a pair of end bells secured to the opposite ends of said casing;
electrically nonconductive means disposed at the opposite ends of said casing and electrically insulating said casing from said end bells;
a stator and a rotor mounted within said casing, said rotor having an electrically conductive spindle connected thereto, said spindle extending through said end bells;
bearings within said end bells adjacent to the outer ends thereof and rotatably supporting said splindle adjacent the ends thereof whereby deflection and vibration of said spindle are minimized;
one of said end bells having a hollow, axially elongated section adjacent to one end of said casing and located between said casing and the bearing in said one end bell;
an electrically conductive slip ring mounted on said spindle and located within said hollow section of said one end bell and axially inwardly of said bearing therein;
said hollow section having an openin therethrough and a brush mounted Within said opening and slidably engaging said slip ring whereby said brush means can supply electrical potential to said slip ring and thereby to said spindle;
a sleeve of insulating material surrounding said bearing in said one end bell and electrically insulating said bearing from said one end bell whereby flow of electrical energy through said bearing is prevented; and
means for securing an electrolytic grinding wheel on each end of said spindle respectively and closely adjacent said bearings, whereby radial deflection of said grinding wheel is minimized, at least one grinding wheel being mounted on said spindle.
References tli ed in the file of this patent UNITED STATES PATENTS 2,514,693 Chapman July 11, 1950 2,526,423 Rudorff Oct. 17, 1950 2,798,846 Comstock July 9, 1957 2,946,731 Falls July 29, 1960