US2427064A - Temperature responsive device for use on grinders and method of grinding - Google Patents

Description

p 9, 1947. A. F2 MOUL v 2,4ifi4 TEMPERATURE RESPONSIVE DEVICE FOR USE ON GRINDERS AND METHOD OF GRINDING FiledAug. 8, 1945 2 Sheets-Sheet 1 ATTORNEYS sephg, 1947., U 2,427,064-

TEMPERATURE' RESPONSIVE DEVICE FOR USE ON GRINDERS -AND METHOD OF GRINDING Filed Aug. 8, 1945 2 Sheets-Sheet 2 ATTORN'EYS Patented Sept. 9, 1947 UNITED STATES PATENT ornea TEMPERATURE RESPONSIVE DEVICE FOR USE ON GRINDEBS AND METHOD OF GRINDING Arthur F. Moul, Buffalo, N. Y. Application August 8, 1945, Serial No. 609,520

This invention relates to improvements in grinding surfaces of materials in such a manner as to avoid heating the materials to such an extent as to damage the same.

It is well known that when surfaces of certain materials are ground in such a manner that the temperature of portions of the material .is materially increased, such material may become damaged due to local heating and in the case of steels and other metals, the tempers of the same may be destroyed. The temperatures at which steels of various kinds lose their tempers vary considerably. Furthermore, steels are not always of uniform texture and sometimes the steel may contain hard spots which become excessively heated during grindingw while other parts of the steel became heated to a materially less extent, thus causing internal strains in the molecular structure of the steel, which may result in damage to or fracture of the steel.

One of the objects of this invention is to provide a method of and means for employing temperature responsive means in connection with grinding surfaces or edges of work, whereby damage to the work which is being ground due to excessive temperatures can be avoided. A further object of this invention is to provide a heat responsive device which is arranged to contact the material which is being ground in the immediate vinicity of the portion thereof which is being subjected to the grinding action, and by means of which accurate information as to temperature can be obtained. A further object is to provide a heat responsive device, which is connected with an indicator for indicating the temperature of the portion of the work which is 13 Claims. (01. 51-2) 2 Fig. 3 is. a diagram showing electrical connections employed for modifying the operation of a grinding machine when the work becomes heated beyond the desired extent.

being ground. Another object is to provide a temperature responsive device of this kind which is arranged to modify the operation-of a grinding machine when the work which is being ground attains a temperature in excess of that desired.

a Another object is to provide a mechanism including a. temperature responsive 'device contactin the work in the immediate vicinity of the portion thereof which. is being ground and which is connected with the grinding machine in such a manner as to interrupt the operation of the machine when'the work becomes heated to a point beyond which it is not safe to continue. Other objects and advantages of this invention will appear from the following description and claims. 7

In the accompanying drawing, in which is shown by way of'example one embodiment of this invention:

Fig. 1 is a front view of a grinding machine having a heat responsive device embodying this invention applied thereto.

V Fig. 2 is a fragmentary end view thereof, showing the abrasive wheel in operative relation to the workand showing a heat responsive device embodying this invention applied thereto.

Fig. 4 is a fragmentary enlarged sectional view showing a thermocouple applied to a workpiece.

The machine shown in Figs. 1 and 2 is of the type commonly employed for grinding large knives, such for example as paper cutter knives, metal'shear blades and the like, but it will be understood that .this invention may be applied to any other type of grinding machine. This machine has. a.horizontal bed l0 suitably supported by legs or pedestals II from a floor. On the bed of the machine is mounted a suitable support I! for the work, which in the construction illustrated is mounted to move back and forth lengthwise of the bed ill of the machine. I4 represents the work, which may be a. paper cutting knife or sheet metal shear, or cutter, or any other article to be ground. [5 represents the grinding or abrasive wheel which is mounted to rotate in the fixed guard or housing It. The grinding wheel may be rotated in any suitable or desired manner, and in the construction shown, an electric motor I! is directly connected with the shaft of the grinding wheel. The motor may be mounted on any suitable support (not shown) mounted in fixed relation to the bed of the machine, for example, on the middle pedestal II. I

The work support l2 includes a lower part l9 which is slidably mounted on the bed ill of the machine, and on which a work upporting table 20 is mounted. The table is adjustable to various angular relations with reference to the plane of the grinding surface of the grinding wheel t5; which, as shown, is of the cup type of which the radial edge only is used for grinding. The work supporting table 20 may be adjusted by any suitable mechanism, not shown in detail, and including a hand wheel 2| by means of which the table may be moved from the horizontal position shown in Figs. 1 and 2 to any desired angular position. Consequently, if a beveled edge is to be ground on the work, the angular adjustment of the table 20 determines'the angle of the bevel. The table 20 is also movable toward and from the grinding wheel in a direction transverse of the longitudinal movement of the work support l2,

and means may be provided as is customary in machines of this type, for advancing the table automatically toward the grinding wheel. Since,

however, this invention is not concerned with any particular type of grinding machine, these detailed parts of the machine are not shown or described. It is also possible to construct the machine with a stationary work support and with a grinding wheel which reciprocates lengthwise of the work and the improvements herein described may be applied to such type of grinding machine or to any other type.

In accordance with this invention, a temperature responsive member of any desired type is applied in contact with the work in such a manner that any change in temperature of that part of the work which is subjected to grinding, will immediately affect the heat responsive unit. Any type of heat responsive unit may be employed, which responds quickly to any changes in temperature, and in the particular construction shown, there is shown by way of example a thermocouple, which includes two wires or rods 25 and 26 of diii'erent metals or alloys and welded or otherwise secured together at their ends, as shown at 21.- These connected ends of the two wires or rods are caused to bear against the work. The bearing of the heat responsive device against the work may be accomplished in any suitable or desired manner. For example, a series of these thermocouples may be placed at spaced intervals lengthwise of the work and may remain in fixed relation to the work, or one or more heat responsive devices may be arranged to slide lengthwise of the work in contact therewith in such a manner that the thermocouple or other heat responsive device will bear against the work a near as possible to the portion thereof which is engaged by the grinding wheel. For example in Figs. 1 and 2, the heat responsive device is mounted in a suitable holder or casing 29 made of insulating material, and which is mounted in turn on an adjustable bracket 30 suitably secured to the guard l6 of the grinding wheel. In the case-of dry grinding, it is merely necessary that this holder support the thermocouple or other heat responsive device. If water or other cooling medium is supplied to the work, this guard or holder may be made of rubber or other material to keep the moisture out of contact with the heat responsive device. Also the holder 29 may have the end thereof contacting the work about the heat responsive device and wipe away any abra sive particles or liquid on the work o a to save the thermocouple from excessive abrasion or from contact with the cooling liquid. The two wires or rods of the thermocouple are connected by suitable electrical conductors 3| and" for car- .rying the thermo-electric current generated by the thermocouple. In the construction shown in Figs. 1 and 2, an edge of the work II is ground, which is approximately at a right angle to the opposite faces of the work, and thermocouple is shown in contact with one of the flat faces of 4 ample, inFig. 2, the temperature responsive device may engage the lower surface of the work i M, or the edge which is being ground, adjacent to the abrasive wheel.

If a thermocouple is used, the thermocouple will generate a thermo-electric current which is approximately proportional to the temperature to which the end of the thermocouple i exposed. This current is supplied to an instrument of any suitable or well known type which will indicate the amount of the electric current generated by -the thermocouple. In the particular construction illustrated, the two conductors 3| and 32 leading from the thermocouple pas to a measuring instrument 35 of this type. Fig. 3, which has a needle or pointer 36 which is movable in proportion to the amount of electricity developed in the thermocouple. The needle 36 maybe used merely to indicate the amount of thermo-electric current generated in connection with suitable graduations 3], Fig. 3, upon a dial or card which may be calibrated to read directly the temperature of the part of the work contacted by the thermocouple.

As thus far described, thi invention is very useful in connection with the grinding of materials. It is generally well known to what temperature a material, such for example as a steel or an alloy, may be raised, without becoming damaged, but heretofore no means have been dey vised for determining when a temperature is reached beyond which it is not safe to continue the grinding. These excessive local temperatures may in the case of certain materials cause unequal expansion of diflerent parts of the work, and thus cause failure due to cracking or checking of the work. In the case of steels or other metals which are tempered, an excessive heating of the work the work in immediate proximity to the edge which is being ground. If a beveled edge is ground on the work, it is preferable to have the temperature responsive element contact the edge portion on the face opposite tc'that which is being ground and as near as possible to the thin portion of the beveled edge, since this part of the edge becomes heated most rapidly to nearly the same temperature as the surface which is subjected to the abrasive action. It is, however, also possible to have the thermocouple contact and move along the surface which is being ground, and this may be accomplished by mounting a thermocouple at, either side of the grinding wheel, or in the case of cupped grinding wheel, within the cupped portion so as to be as near as possibl to the part of the work which is being ground. However, it is not intended to limit this invention to the particular position to which the heat responsive element is mounted, since any position of the same where it is readily responsive to changes in temperature of the portion of the work which is being ground may be selected. For exmay result in loss or impairing of the temper of the metal. It also frequently happens that steels or other metals have spots or areas therein of varying'size which may be of slightly diil'erent composition or physical structure and which during grinding become more heated than adjacent parts of the metal. Without any indication as to the temperatures of the work which is being ground, a considerable percentage of the work which is ground is damaged. Furthermore, because of the possibility of damaging work by excessive temperatures, there is a decided tendency on the part of the operators of grinding mav chines to grind the work very slowly to avoid such temperatures, and this results in unnecessary ineiliclency and loss of time in grinding. By means of this invention, as thus far described, the ternperature of the article can be accurately determined by merely observing the needle or hand II with reference to its scale 31. If ,at any time during grinding, the needle 38 indicates high :temperatures approaching the danger point, steps may be taken to reduce this temperature, either by supplying more cooling liquid if a liquid is being used, by slowing the rotation of a grindwheel, or by decreasing the rate of feed of the work to the stone, or by stopping the machine long enough to let the work cool oil. By means of the temperature indicator, it is also possible to increase the efliciency of the grinding operation, in the event that the indicator shows the temperatures to be so low that an increase in the rate of grinding could be safely adopted.

- The improved =method of grinding here described, therefore, not only saves work from dam-' conducting a grinding operation at higher temperatures which, nevertheless, are not high enough todamage the work, thus reducing the time required for the grinding operation It is also readily possible to use the device described for the purpose of modifying grinding operations in case dangerously high temperatures are indicated. For this purpose, the pointeror needle 38 of the meter 35 may be connected to a suitable source of power and provided with an beground at different temperatures, I

In order to make the contact positive and reliable, the contact member 40 may be in theform of a magnet and a small piece of magnetic material M may be'secured on the needle 36. The needle is connected with a, conductor 83 which in turn connects with a source of current supply,

ondiflerentsteels' or 'other materials which'may and the contact A is connected with a conductor M which is connected to one terminal of a relay 45 controlling a switch 45 which is normally held lrrcircuit closing position by means of a spring 41, but which is moved into open position when currentissupplied to the relay 45. "The other terminal of the relay 45 is connected by a conductor 48 to the other side of the supply line, a branch 68a. of conductor 48 being connected to the movable switch member 45.

The switch 55 isurged by the spring dlinto contact with a terminal 49 connected to a 'conductor 50 which passes to a holding coil of a control switch 52 in the circuit of the motor I1. The motor control switch 52 is normally held in open circuit position by means of a spring 53, but may be moved into and held in closed position by means of the holding coil 5! when the switch 46 is closed. The movable member of the switch 52 n is connected to one'terminal of the motor 11 by conductor 55, the other terminal of the motor beingfconnected by a conductor 55 to the line or source of powers The stationary contact with which the motor control switch 521engages when in circuit closing position is connected by means vof a conductor5l to the other side of the line.

It will be obvious from the foregoing that when the needle 36 of the thermo-elect'ric current meter or sensitive relay 35 is in engagement with the contact 40, through the relay 45', the relay switch 48 will be opened, thus interrupting the supply of current to the holding coil 5| of the motor switch 52, and thus permitting the motor switch to be moved into open position to stop the operation of the motor. It is, however, very advisable not to stop the operation of the motor, at any time except when the grinding Wheel is out of engagement with the. work, since otherwise a scoring of .the work results. For this purpose, it is preferable to apply 'limit switches-to the circuit shown in Fig. 3, which limit switches are in parallel arrangement with the relayoperated switch 48, so that the motor will not be stopped unless both the relay switch 46 and one or the other of the limit switches is in open circuit position. These limit switches, which are arranged at the opposite ends of the travel of the grinding wheel or the rk, depending upon the type of grinding machine which is used, each include a movable switch member 60 and a sta- .tionary contactmember 5|, the movable switch member being located in the path of movement of the'grinding wheel or the work. The two stationary switch members Bl are connected by a conductor 62 and the movable switch members 60- are connected to'conductors Hand 64, the

conductor 63 being connected to the conductor '58 and the conductor 56 being connected with the-branch conductor 48a which is connected to the relay operated switch member Mi. 'The two limit switches are, consequently, connected in series with each other and inparallel with the relay switch 46. Consequently, if the relay actuated switch 46 is moved into open'position because of high temperatureof the work, the grinding operation will not be stopped until either limit switch 60 is movedinto open position, which gagement with the work.

- Theco'nnections disclosed in Fig. 3 are merely illustrative of one type of actuating means for will occur when th grinding wheel is out of enusing the heat responsive device for interrupting the grinding operation. It will be obvious, however, that other ways of utilizing the heat responsive device may be employed.

By means of the apparatus described, a machine 'may be set up for a grinding operation and started, and will require no further attention unless the machine is stopped, so that one operator can attend a considerable number of machines without danger of damaging the work. If the needle 36 indicates a relatively low temperature, the grinding operation may be speeded up. Since the temperature responsive device or the thermocouple cannot be placed in contact with the actualsurface which is being ground,

but only in proximity to'such surface, or on a surface immediately after the grinding wheel has moved away from it, suitableallowan'de must be made for the readings indicated by'the needle 35 of the meter, since these readings ,willbe some what lower than the actual temperatures at the 'partlon which the grinding wheel is acting.

While this invention is shown in the drawings as applied to a machine for'grinding edges of work, yet it' will "be obvious that thisinvention is equally applicable to'any other typeof machine for grinding metalsand non-metallic'materials,

and forgrinding any surfaces thereof;

I claim as my invention: f ,1. A methodof grinding work by, means'of a grinding wheel, which includes applying a heat ,responsiv'e device \tol the work adiacehtiofthe portion thereoffwhich is being ground, and modiv fying the grinding of thework when saidheat at'which the work can be ground without dar'nresponsive device encounterstemperatures appreaching closely to the -maximum temperature aging the same., 1

2. Amethod of grinding work by means of an abrasivewheel on, a machine in' which said wheel and the work move relatively to each other, comprising holding .a heat responsive device in moving contact with. the work at portions thereof immediately adjacent to the portion which is acted upon. by the .wheel, and modifying the grinding action when said heat responsive device encounters a temperatureof apart of'th work a which approaches. the temperature at which the work maybe damaged by heat.

3. A method of grinding work by means of a grinding wheel, which includes applying a heat responsive device to the work adjacent to the portion thereof which is being ground, and stopping the grinding of the work when the temperature indicated by said heat responsive device encounters a temperature above which the work may be damaged.

4. A method of grinding work by means of an abrasive wheel, which includes applying a temperature responsive indicating device to the work adjacent to the portion thereofwhich is being ground, and regulating the grinding of the work in accordance with the temperatures indicated by said device, by increasing the rate of grinding when the temperatures indicated are materially below the maximum safe grinding temperatures, and decreasing the rate of grinding when the temperatures indicated approach closely to the maximum safe grinding temperatures.

5. A method of grinding work by means of an abrasive wheel on a machine in whichsaid wheel and the work move relatively to each other, comprising holding a heat responsive device in moving contact with the work at portions thereof immediately adjacent to the portion which is acted upon by the wheel, and stopping said machine when said heat responsive device encounters a temperature above which further grinding may damage the work.

6. A device for use in connection with the grinding of work by an abrasive wheel, which includes a temperature responsive member arranged to contact the work in such close proximity to the portion thereof which is being ground as to be subjected to changes in temperature of said portion of the work, means connected with said member and having a part which is moved by variations in the-temperature of the portion of the work contacted by said member, and means actuated by said part for stopping said abrasive wheel when said temperature responsive mem-- ber encounters a temperature above which further grinding may damage the work.

'7. A device for use in connection with the grinding of work on a machine by an abrasive wheel, which includes a temperature responsive member arranged to contact the work in such close proximity to the portion thereof which is being ground as to be subjected to changes in temperature of said portion of the work, and means connected with said member for modifying the operation of said machine when said member encounters a temperature above which further grinding may damage the work. 1

8. A device for use in connection with the grinding of work on a machine by an abrasive wheel, which includes a temperature responsive member arranged to contact the work in such close proximity to the portion thereof which is being ground as to be subjected to changes in temperature of said portion of the work, and means connected with said member for stopping the operation of said machine when the portion of the work contacted by said member reaches a temperature above which further grinding may damage the work.

9. A device for use in connection with the grinding of work by an abrasive wheel on a machine providing relative reciprocatory motion between said wheel and the work and in which said wheel moves out of contact with the work at the end of each reciprocation, said device including a temperature responsive member arranged to engage the work in such close proximity to the portion thereof which is being ground asto be subjected to changes in temperature of said portion of the work, a part which is moved by variations in the temperature of the work contacted by said member, and means for interrupting the operation of said machine when said part encounters a temperature above which further grinding may damage the work and when said abrasive wheel is out of engagement with the work.

10. A device for use in connection with the grinding of work by an abrasive wheel on a machine providing relative reciprocatory motion between said wheel and the work and in which said wheel moves out of engagement with the work at the end of each reciprocation, said device including a thermocouple contacting the work adjacent to the portion thereof which is being ground, a switch for controlling the operation or said machine and controlled by said thermocouple for opening said switch when said thermocouple encounters a temperature above which further grinding of the work may damage the same, and a limit switch on said machine connected in parallel with said first mentioned switch for stopping the operation of said machine when said abrasive wheel passes out of engagement with the work, for stopping said machine when both of 'said switches are open. Y

11. A device for use in preventing overheating of work during grinding of the same by an abrasive wheel, which includes a thermocouple, means for maintaining said thermocouple in sliding cpntact with the work in such close proximity to the portion of the work which is acted on by said abrasive wheel that said thermocouple will be subjected to changes in temperature of said portion of the work, and electric means connected with said thermocouple for indicating the temperature of the portion of the work contacted by said thermocouple.

12. A device for controlling the grinding or work by an abrasive wheel to-prevent overheating of the work, including a thermocouple, means for maintaining said thermocouple in sliding contact with work which is being ground in such close proximity to the portion of the work acted upon by said abrasive wheel that said thermocouple will be subjected to changes in temperature of said portion of the work, and electrical connections actuated by said thermocouple for interrupting the grinding operation when said thermocouple encounters. a temperature above which further grinding may damage the work.

13. A device in accordance with claim 12 and including a casing enclosing said thermocouple and slidable in contact with the work for keeping abrasive particles and cooling liquid out oi. contact with the thermocouple.

" ARTHUR F. MOUL.

I REFERENCES crrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,102,518 Johnson Dec. 14, 193'! 2,267,391 Astrowski Dec. 23, 1941 2,255,094 Aeppli Sept. 9, 1941 1,370,381 Tarbox Mar. 1, 1925 FOREIGN PATENTS Number Country Date 542,573 Germany Jan. 26, 1932

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