US2426817A - Cooling system for machine tools - Google Patents

Description

P 1947. cPF. CHARLTON ET AL p 2 ,8

' COOLING SYSTEM FOR MACHINE TOOLS Filed Jan. 19, 1945 Patented'sept. 2, 1947 I UNITED STATES PATENT OFFICE COOLING SYSTEM FOR MACHINE TOOLS Charles F. Charlton and Mark A. Palmer, J12,

' Manchester, Conn;

Application January 19, 1945, Serial No. 573,608

1 Claim. (01. 51 267) This invention relates to a novel and superior cooling system for machine tools, such as grinding machines, milling machines, etc. The grinding or cutting contact of such tools with the Work generates a considerable amount of heat and a circulatin flow of cooling liquid is commonly provided over the tool and work for the purpose of keeping the temperature reduced to a safe maximum. It is desirable that foreign particles shall be separated from the spent liquid before it is again returned to the work and that the liquid shall be maintained below a predetermined maximum temperature.

In machines heretofore employed the spent liquid has been returned to a settling tank where the solids are precipitated and the liquid cooled before the latter is again returned to the work. This system of maintaining the liquid at predetermined temperature has proven inefficient due to the accumulation of solids on the refrigerating plates employed in the tank. Our invention contemplates the elimination of this difiiculty by first separating the solids from the spent liquid by precipitation or otherwise and thereafter bringing the liquid to and maintaining it at the desired temperature by passing it through an enclosed channel including a, refrigerating medium on its way back to the work. The production of such an improved method of circulatin cooling liquid to machine tools and providing such liquid in clean and predetermined temperature condition to the work therein comprises the primary object of the invention.

The work operated on by grinding machines is required to be finished to a small tolerance and unless the work is kept at substantially uniform temperature during the grinding operation its expansion and contraction prevents the maintaining of such tolerance. In apparatus heretofore employed the temperature of the cooling liquid has varied as much as 15 and has been particularly affected by the gathering of sediment to a considerable thickness on the cooling system, thereby forming an insulation rendering the cooling effect very inefficient. We have discovered that by first removing the sediment and solids from the liquid and thereafter passing the clean liquid to the Work through an enclosed channel including a refrigerating unit maintained at predetermined temperature we are able to keep the work at a plus or minus temperature within two degrees. The novel method resulting in this increased efliciency comprises an important object of our invention.

These and other features of the invention will be best understoodand appreciated from the following description of a preferred embodiment thereof selected for purposes of illustration and shown in the accompanying drawing in which the one figure in the drawing is an elevation, partly broken away, of a machine embodying our invention.

In the drawing we have illustrated a grinding machine it including a grinding wheel l2. A liquid coolant is conducted to the wheel and work from a nozzle I in communication with a pipe it, the flow bein controlled by a valve l8. Acoolant reservoir 23 is provided beneath the grinding wheel to receive the spent coolant. It is desirable that foreign particles, particularly including those picked up from the work, should be removed before the coolant is returned to the tool and for this purpose we have illustrated the reservoir as divided into a plurality ofcompartments 22, 23 and 24. The spent coolant flows from the tool into thefirst compartment 22 Where most of the particles settle before the coolant flows over thebaffle 25 into thecompartment 23. Further settling of any remaining particles takes place incompartment 23 before the coolant flows over the baffle 26 into thecompartment 24. The resulting relatively clean coolant is circulated from thecompartment 24 back to the tool.

Efficient operation requires that the temperature of the coolant shall be at or below a predetermined maximum when it reaches the tool and work and the primary object of our invention resides in an improved method for elliciently maintaining such temperature within predetermined limits. To this end we pass the clean coolant from the compartment 2:3 through a refrigerating path on its return to the tool. As illustrated in the drawing, this path includes a plurality of pipes or tubes 28 surrounded by a refrigerating medium of predetermined capacity and temperature within a cylindrical heat exchanger 3B.

Mounted on the reservoir is apump 32 operated by amotor 36 and arranged to pump thecoolant from thecompartment 24 throughpipes 38, 38, V

28 and Hi to the nozzle It. An economizer In is preferably employed in connection with the refrigerating system. A compressor (not illustrated) maintains a suction on theline 42 which passes in the form o f-a coil 44 back to the chamber 39 at 46. The vapor thus drawn from the chamher is compressed to a liquid and returned through apipe 48 to and through acoil 48 within the pipe of coil 4d and from thence through apipe 50 to the bottom of thechamber 30. A thermoworking operations thereon, which consists in static expansion valve is provided at 52 and is conducting spent cooling liquid from the work connected by atube 54 to a controlling expansion to a separating chamber, separating the detritus bulb at 56 whereby automatically to maintain a solids from the liquid in the separating chamber, predetermined temperature within the chamber 5 conducting the separated liquid through a refrig- 30. The passage of the liquidrefrigerant through erating device maintained at a constant and the relatively cooler vapor refrigerant within the definite temperature thereby cooling the sepcoils substantially. cools the reirigerar trliquigi to arated liquid; to;. a predetermined temperature, the requireddegre Orbits return {cathechamber and discharging said; liquid 7 at; said predeter- 30. A refrigerant liquid level is maintained in 10 mined temperature onto the work.

thechamber 30 substantially as indicated at 58;; CHARLES F. CHARLTON. It will be apparent that the coolant is cooled MARK A. PALMER, JR.

with maximum efficiency as it passes-throughthe several pipes 28 on its return from the .com, 7 REFERENCES CITEDPartment 24 t0 the 1 a it Wi l be furthgrrhgl'e 15;, Thejollowing references are of record in the apparent that the cooling system is adaptedto file of this patent:

operate and continue to operate with maximum-- efficiency on the coolant which is substan ially v UNITED STATES PATENTS freed from foreign particles before being cir-' Number Name Date culated through the refrigerating path, 9 ,7 MiSkOlCZY ----r----p 02 Having'thus disclosed our invention what, we 2,132,952 Todd etal. Dec.- 12, 1939 claim as new and desire to secureby Letters e et a Patent oi the United States is: 403,030; Bauer May '7; 1889 A method of producing work-to closetolerances 1,455,187 Brown May 15, 1923 in a machine tool by maintaining a predetermined 25 1,938 ,8'75 1 Stratton Dec. 12,- 1933 constant temperature in the-workpiece during

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