US2741078A - Portable grinding tool - Google Patents

Description

April 10, 1956 J. R. TENNEY PORTABLE GRINDING TOOL.

3 Sheets-Sheet 1 Filed June 1, 1955 INVENTOR. JOHN R. TE/VNE), yomzg/ @45 his Attorney.

April 10, 1956 TENNEY 2,741,078

PORTABLE GRINDING TOOL Filed June 1, 1955 3 Sheets-Sheet 5 Tug-K '5- 68 c 68- 5,8 I P IN VEA/ TOR. 53 JOHN R. TEA/NE),

BK yew/10 his Af/omey.

United States Patent PORTABLE GRINDING TooL John R. Tenney, Salt Lake City, Utah, assignor to United States Steel Corporation, a corporation New Application June 1, 1955, Serial No. 512,353

4 Claims. (Cl. 51-244) The present invention relates to grinding tools and more particularly to a portable grinding tool which can be temporarily positioned adjacent a workpiece to be ground and operated from a remote station.

The tool of the invention finds particular adaptation in use for grinding or turning commutators of large motors and generators and in that respect a preferred embodiment of the invention will be described.

During the process of grinding or turning the commutator of a large motor or generator it is necessary to have the grinding stone held firmly and moved back and forth across the face of the commutator as it is rotated. Prior to my invention this operation was accomplished by means of a grinding stone carried by a carriage mounted for reciprocal movement on a lathe bed which was mounted on the brush ring of the motor or generator by means of a jig to extend across the face of the commutator. The carriage was provided with a manually operated traverse feed and a manually operated cross feed. The tool was operated by a workman who turned the traverse feed to move the stone across the face of the commutator, and the cross feed to move the stone inwardly or outwardly as required. Another workman held the collecting nozzle of a vacuum hose adjacent the stone as it reciprocated to pick up copper particles and abrasive dust that was generated during the grinding operation. It was necessary for another workman to be stationed at the machine during the grinding operation to trip 01f the motor in the event of an emergency.

When grinding the commutator of a large motor under power it was necessary for the men performing the operation to wear high tension gloves, and stand on rubber blankets for insulation from the energized motor. Respirators and goggles were also worn as safety precautions by the workmen. The necessity of using all the safety equipment required made the grinding operation extremely awkward and cumbersome. Due to the length of time required to grind or turn the commutator of a large motor or generator it was necessary to use two crews of men alternately to prevent excessive fatigue and resultant safety hazard.

I propose to eliminate the above described disadvantages inherent in commutator grinding by providing an apparatus including a portable grinder lathe automatically operated by means of two motor drives connected by flexible shafts to the traverse drive and cross feed of the lathe. The apparatus I propose also includes common limit switches for the traverse drive and cross feed whereby the traverse direction of travel of the tool carriage is simultaneously indexed to provide automatic feeding of the grinding stone inwardly in the required amount. The electrical circuit of the apparatus is so arranged that the cross feed is also actuated automatically whenever a high spot on the face of the commutator is encountered. The driving motors of the apparatus of the invention are carried in a wheeled cabinet and connected with the traverse drive and cross feed of the lathe of the invention by means of elongated flexible shafts so that the lathe can 2,741,078 Patented Apr. 10, 1956 be installed on a motor or generatorand be operated at a safe distance. This arrangement makes it possible for the operators to work safely without the need of special protective clothing and blankets. The cabinet housing the motors is provided with a control panel fitted with instrument and switches necessary to the operation of the grinding lathe as well as a control switch whereby the motor or generator being ground can be shut down in the event any trouble develops.

It is accordingly an object of my invention to provide a portable grinding lathe which includes an automatically operated grinding tool carriage having powered traverse drive and cross feed, and means whereby the direction of the traverse drive is automatically reversed and the cross feed is automatically indexed at each terminus of the path of travel of the carriage.

It is a further object of my invention to provide a device of a character described in the object stated above including means whereby the cross feed is actuated automatically to move the stone inwardly toward the commutator face when a high spot is encountered thereon.

These and other objects will become more apparent after referring to the following specification and attached drawings, in which:

Figure 1 is a plan view;

Figure 2 is a side elevational view;

Figure 3 is a sectional view taken on the line III-III of Figure 2; and

Figure 4 is a diagrammatic illustration of the electrical system of the invention.

Reference numeral 2 designates a conventional motor having a commutator 4 and a brush holder ring 6. The apparatus of my invention is mounted on the brush holder ring 6 by means of a jig 8 and bolts 10 and includes a lathe bed 12 having tool carriage l4 slidable thereon. The lathe bed 12 is mounted across the face of the commutator 4 extending from its one side to the other. The tool carriage is moved across the face of the commutator by means of a conventional screw shaft traverse drive 16 and carries grinding stones 18 supported on a cross feed- Ztv which includes a sliding cross bed 27 and a screw shaft 21 driven by a splined shaft 22 and gear 24 splined thereto. The traverse drive shaft 16 is connected with the gear head drive 26 of a reversible motor 28 by means of a flexible shaft 30. Splined shaft 22 is connected with the gear head drive 32 of a motor 34 by means of a flexible shaft 35. Motors 28 and-34 are mounted in a cabinet 36 which is located in the vicinity of the equipment being processed but spaced a sufiicient distance therefrom to allow operation of the device of the invention at a safe distance from the equipment. The cabinet is provided with wheels 38 so that it can be easily moved to difierent locations where work is to be performed. Cabinet 36 is also provided with an inclined control panel 49 having conventional meters and control switches 42 thereon. The control panel 4!) is also equipped with a control switch 44 which is connected into the control circuit (not shown) of motor 2 so that rotation of the motor commutator can be started or stopped from the control panel.

Limit switches 56 and 48 are mounted on the lathe bed 12 at opposite ends of the path of travel of the carriage 14. Limit switches 46 and 48 are adapted to be tripped by the carriage 14 as it reaches each end of its path of travel to reverse the motor 28 and thereby reverse its direction of travel. Each time one of the limit switches is tripped motor 34 is energized, through means to be described hereinafter, to rotate shaft 22 and feed stones 18 inwardly closer to the commutator ready for the next trip across its face. At any time during the traverse motion'of the carriage 14 across the commutator that the torque requirement on motor 28 increases due to a high spot on the commutator face, this extra torque requirement'on motor 28 actuates an electrical sensing ci-rcui-t,--to

be described, which causes motor 34 to increase the pressure of stones 18 against the commutator to grind oflthe highspot. 7U V lThe nozzle d of a -flexible vacuum hose 52 is carried by the toolcarriage 14 adjacent the grinding stone 18 for the purpose of picking up particles of metal anddust generated during the grinding operation.

'In operation, the lathe bed 12 is fastened against the commutator 4 which is to be ground and secured in position by means of a jig 8 clampedto the brush holder ring dby volts 10, as best shown in Figure'3. The cabinet 36 iswheeled into position and the flexible shafts and are installed connecting motor '28 and shaft 16, and

motor 3-l-andshaftl22, respectively. Motor 28 is actuated by closing a push button switch 42a on panel 46 to energize a relay '54'having normally open contacts 54a and I 54b whereupon contacts'54a and 54b are closed completing a circuit to a contactor 56 causing its normally open contacts 56a and 56b to close.

The limit switch also closes the normally open contact 5 3a completing a circuit to a relay 68 causing its normally open contacts 69a and 60b to close whereupon a contactor 62 having normally open contacts 62a and 62b is energized causing its contacts to close. Closing of contacts 62a and 62b causes current to flow from supply line 58 to the. bottom of the armature of motor 28 thereby reversing its direction and causing carriage 14 to move toward limit switch 46. closes its own hold circuit through normally closed back contact %Z of limit switch 46.

When limit switch 46 is tripped by carriage 14, it opens contact 5-65, de-energizing relay 6i) and, in turn, contactor 52, stopping motor 23. The limit switch also closes normally open contacts 46:1,re-energi2ing relay 54. The lat- V ter completes its own holding or sealing circuit and energizes contactor 56 to start motor 28 in the same manner as described above when push button 42a'is closed.

A push button 42b is provided on panel 40 in a circuit parallel with limit switch 43 for starting motor 28 in the direction whereby carriage 14 will be moved toward limit switch 46.

Each time motor 28 is started or reversed or a high spot on the surface of commutator 4 is encountered by stones 18, a surge of current passes to motor 28. This surge of current causes a voltage impulse across the secondary winding of a current transformer 64, which, in turn, causes V V Closingof contacts 56a and 56b causes current to flow from power line 58' The relay 60, at contact 69a,

4 a signal 'to be *fed into a --magnetic amplifier 66 which then supplies. current enough to actuate a relay 68 having a normally open contact68c. The closing of contact 68c shunts a resistance 70 whereupon sufficient voltage.

is applied to motor 34 from power line 58' to energize it for a predetermined time. Energization of 'motor 34 causes cross feed 20 to move the grinding stones 18 closer to the commutator surface. 7

A master switch 72 is provided in the power lines 58 and 53. This switch is kept open when-the equipment in pcration.

While one embodiment ofmy invention has been shown and described, it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

I claim:

i. A lathe comprising a tool for machining a workpiece, a reciprocating tool carriage for supporting the tool, a first motor for reciprocating said tool carriage, a second motor for feeding said tool'intothe workpiece, apair of limit switches one at each end of the path of-travel of said carriage, means operable by said limit switches for reversing the direction of rotation of said first motor, and nieans operable by a surge in current to said first motor for causing said second motor to feedfsaid tool towardcarriage mounted on said bed for movement along said.

workpiece, a grinding tool mounted on'said carriage, a first motor for reciprocating said carriage, a second motor for feeding said tool into the workpiece, a pair of limit switches one at each end of the path of travel of said carriage, means operable by said limit switches for reversing the direction of rotation of'said first motor, and means No references cited.

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