US2494534A - Coolant filter system - Google Patents

Description

Jan. 17, 1950 F. J. ARMSTRONG ET AL COOLANT FILTER SYSTEM Filed March 16, 1944 5 Sheets-Sheet l INVENTORS Francis J Armsiron y Hem) 1 Hamlin m'w m w i ATTORNEYS Jan. 17, 1950 F.,J. ARMSTRONG ET AL ,4

COOLAN T FILTER SYSTEM 5 Sheets-Sheet 2 y Henry Hamlin,

ATTOZUVEYJ INVENTORS Jan. 17, 1950 F. J. ARMSTRONG} ET AL COOLANT FILTER SYSTEM 5 She'ets-Sheet 3 Filed March 16, 1944 a zye I] T AF 2 A a /M. mm

F. J. ARMSTRONG ET AL 2,494,534

COOLANT FILTER SYSTEM 5- Sheets-Sheet 4 I M y a INVENTORS J I'CUZCL J' J/lrmszrarzy y Henry I Ham Zz'iz r ATTORNEYS Jan. 17, 1950 Filed March 16, 19 4 1950 F. J. ARMSTRONG ET AL 2,494,534

COOLANT FILTER SYSTEM 5 Sheets-Sheet 5 Filed March 16, 1944 9 Herzr Z'Hamlin 2% Patented Jan. 17, 1950 2,494,534 GOOLAN T FILTER SYSTEM Francis J. Armstrong and Henry F. Hamlin, Syracuse, N. Y., assignors to United States Hofiman Machinery Corporation, New York, N. Y., a corporation of Delaware Application March 16, 1944, Serial No. 526,735

13 Claims.

This invention relates to the purification of fluids and more particularly to the removal of suspended solid materials from coolant which is used in cutting and grinding tools.

An object of this invention is to provide for a continuous and steady flow of a liquid to a machine or group of machines. A further object is to provide an automatic coolant supply system which will make available to cutting or grinding tools coolant liquid at a constant pressure. A further object is to provide a liquid supply of the above character where the supplying of liquid is insured even under emergency or abnormal conditions. A further object is to provide an efiicient system of the above character which will occupy a minimum of space and which may be adapted to meet the many varying conditions which exist where such systems are needed. A still further object is to provide for supplying machine tools with an even stream of coolant which is free to the extent desirable of foreign materials, such as small particles of the metal and of the grinding wheels. These and other objects will be in part obvious and in part pointed out below.

' The invention accordingly consists in the features of construction, combinations of elements, arrangements of parts and in the several steps and relation and order of each of the same to one or more of the others, all as will be illustratively described herein, and the scope of the application of which will be indicated in the following claims.

Inthe drawings:

Figure 1 is a plan view of one embodiment of the invention;

Figure 2 is a side elevation of the embodiment of Figure 1 with parts broken away to show details of construction;

Figure 3 is an enlarged sectional view on the line 3-3 of Figure .2 with the central portion broken away;

Figure 4 is an enlarged elevation of one filter um't;

Figure 5 is an enlarged sectional view showing the manner of attaching the filter springs of the filter unit;

Figure 6 shows another manner of attaching the lower ends of the filter springs;

Figure 7 is a vertical section of the backwash valve;

Figure 8 is a horizontal section of the backwash valve; and

Figure 9 is a schematic wiring diagram of the backwash control system.

As conducive to a clearer understanding of the invention, we will set forth certain of the problems which are met with in connection with an installation where the illustrative embodiment of the invention is used. With cutting and grinding tools it is common practice to supply a coolant in the form of a stream of liquid such as an oilwater emulsion which fiows onto the tool and the work during the working operation. This coolant carries away from the work small particles of metal and, during a grinding operation, small particles of the grinding wheel (referred to as emery). Particularly when the liquid is agitated, these small particles tend to remain suspended and even large particles often settle out very slowly. This is especially true with emulsions where some of the small particles become coated with films of oil. Theseoil-coated particles tend to float on the top of the liquid and combine with surface oil to form foam; the foam does not disappear rapidly but releases the particles slowly so that the coolant remains dirty for a long period of time.

In considering the question of cleaning coolant it is important to understand the varying demands which are placed upon any particular system, and the varying requirements for different systems. When /fine grinding and other finishing operations are being carried on in a shop, the presence of emery or metal particles in the coolant may result in scratching the finished surfaces; thus, it is important to remove even fine particles from the coolant. Under other circumstances, such as when all of the machines in a shop are performing rough cutting operations, it is important that large quantities of coolant be available but it is immaterial whether or not the coolant contains some suspended particles because these will not interfere with the cutting operations and will not damage the work. In this last situation the larger particles of metal must be removed from the coolant but the coolant need not be filtered to the extent necessary to remove the smaller particles. In order to meet these and other situations the commercial system for treating coolant must be adaptable to the particular job at hand so that only the neces'sary filtering is carried on. In considering this problem, it should also be understood that under emergency conditions partly cleaned coolant is preferable to no coolant because the tools will be severely damaged if the coolant supply is completely cut off. For this reason, the system should insure a supply of coolant evenif the coolant is not cleaned to the desired standard.

It is desirable that the system be capable of handling the maximum demand for long periods of time and there should be a reserve supply of coolant. Furthermore, the starting up or shutting down of one machine should not cause a change in the stream of coolant being supplied to the other machines. The stream should be constant and thus should be free of air as this causes spurting and uneven flow at the tool. The illustrative embodiment of the invention meets the requirements above set forth and satisfies the objects discussed.

In the illustrative embodiment of the invention the supply of coolant is held in a horizontal tank which has a partition adjacent one end which forms a chamber for the clean coolant separate from the main body of dirty coolant. At the end of the tank opposite the chamber for the clean coolant the end wall of the tank is inclined, and a slow-moving endlesschain drag arrangement continuously removes sludge from the bottom of the tank and discharges the sludge over the top of the inclined end wall. In the central portion of the tank, adjacent the space for clean coolant, is a bank of filter units through which clean coolant is drawn from the tank and pumped to the chamber for clean coolant at the end of the tank.

Each of these filter units is formed by a large number of vertical, tight-wound coil springs which are under uniform tension to provide even spaces between the adjacent turns of the springs; the coolant flows through these spaces but the dirt or solid particles form a deposit on the outside of the springs. The upper end of each spring is closed by a supporting screw, and the bottom end is open to a header assembly to which the springs are attached. lhe clean coolant is pumped from the bottom ends of the springs through the header assembly. The deposit which collects upon the springs is removed periodically by reversing the flow, i. e.,. by pumping clean coolant back through the header assembly and out through the springs. Air is added to the clean coolant as the coolant flows to the filter units to aid the backwash operation. This reversal of flow of the coolant is initiated in the various filter units successively by a timing arrangement. The frequency of the cleaning operation is increased in the event that the flow of coolant from the various units falls below a predetermined minimum.

In the illustrative embodiment, a coolant filter system includes centrifugal pumps and piping to deliver the clean liquid at a constant pressure to the machines where the cutting and grinding operations are carried on. The dirty coolant from the machines is pumped to the main body of dirty coolant in the filter tank and the system is operated continuously to maintain a reserve supply of clean coolant.

Referring particularly to Figures 1 and 2 of the drawings, an open-topped horizontal tank 2, rectangular in horizontal crosssection, has at the left (Figure 2) an inclined end wall 4. At the right hand end of the tank is a chamber 6 for clean coolant which is separated from the remainder of the tank by a partition 8. Submerged in the dirty coolant at the left of partition 8 are four identical filter units designated Ina, lllb, 10c, and Hid, but referred to collectively as units Ill. Filter units in rest on angle bars 12 (see also Figure 3) which are welded to the respective tank side walls i4 and I6 (Figures 1 and 2). The dirty coolant is pumped to tank 2 in the zone over the inclined end wall 4 through a vertical pipe l8 and two outlets 20. Outlets 20 direct the coolant toward the left against a vertical bafile 22 the upper edge of which is above the normal liquid line 28, and the lower edge of which is attached to an inclined baffle 24, parallel to end wall 4. To the right of outlets 20 is a second vertical baflle 26 the upper edge of which is below the liquid line 28. Baflles 22, 24, and 26 extend between the tank side walls M and IS with the ends of the baffles welded to the side walls. The incoming dirty coolant from outlets 20 is deflected by baffles 22 and 24 toward baffle 26 and the center of the tank. Foam and light particles, such as oil-coated emery, float to the right along the surface while the heavier particles and the main body of the liquid is deflected downwardly. However, the liquid movement caused by the incoming coolant is largely dissipated without causing agitation of the body of the coolant such as would interfere with the removal of suspended solids from the coolant.

The filter units l are operated continuously except that they are shut down intermittently for backwashing; that is, to remove the deposit of solid particles collected on the individual filters, all in a manner to be explained below. The filter units lila and llib at the left are operated as a pair with the clean coolant being pumped from them through a pipe 30 by a centrifugal pump 32, the discharge of which is connected to a pipe 34 extending to the lower part of chamber 6; the pair of filter units I00 and Ind at the right has clean coolant pumped from it through a pipe 36 by a centrifugal pump 38 which discharges into chamber 6 through a pipe 48. Referring to Figure 3 which shows the filter unit Hid, pipe 35 is connected through a normally open shut-off valve 42 to the vertical outlet M of a backwash valve 46.

Backwash valve 46 is connected through pipes 50 and 52 to two pipes 54 which form the connections to the opposite ends of the filter unit [0. The details of construction of this filter unit are covered in a copending application, Serial No. 526,736, filed March 16, 1944, of Francis J. Armstrong, one of the inventors in the present application, and only those details which are 50 pertinent to the present invention will be discussed here. At the end of each of pipes 54 is a transverse header 58 (see also Figure 4) having a horizontal portion 60 and six downwardly extending connecting nipples 62. Each nipple 62 65 cooperates with the corresponding nipple of the other header to provide the connection to one of the six individual filter assemblies, one of which is shown in Figure 3 and is formed by a U-shaped pipe assembly and a row of vertical 60 springs 80. Accordingly, each nipple 62 is connected through a coupling 64 to a vertical pipe 66, the lower end of which is connected through a coupling 68 to the end of a horizontal pipe 10. Clamped to the center of each pipe is a 65 vertical brace pipe ll which is parallel to pipes 66. Near the top of pipes 66 and H is a horizontal channel plate 78 which has downwardly extending sides (Figure 4) 19. The pipes extend through holes in this plate and the plate is adjustably 70 supported from the pipes by brackets 12 clamped to the pipes. Each bracket 12 is clamped to its pipe by a clamping bolt 14 and (Figure 3) in turn supports an adjusting stud 16 which is received in a vertical hole in the bracket; each of studs 75 16 is threaded in an adjusting block 11 which is welded to the channel plate 18 and through which the pipe passes. Adjusting blocks I1 are in three groups positioned respectively at the two ends and center of the channel plate with the blocks in each group fitting together in side-by-side relationship as shown in Figure 4; this strengthens the channel plate and provides rigid bracing for the pipes. A rigid frame is formed by pipes 54, the two headers 58, channel plate 18, and the six -U-shaped pipe assemblies each formed by a pair of vertical pipes 66 and a horizontal pipe l; this rigid frame is braced by pipes H and is supported by the couplings 68 which rest upon the angle bars 12 at the two sides of the tank.

Channel plate 18 supports the upper ends of six rows of the filter springs 88, the lower ends of the springs of each row being attached to one of pipes 10. The springs attached to each pipe are equally spaced along the pipe except at the center at pipe H. Springs 88 are connected to plate 18 and pipes 18 in the manner shown in Figure 5, there being threaded into the top end of each spring a stud 8i the thread of which has a pitch slightly greater than the natural pitch of the coil spring; thus, the stud is automatically locked into the end of the spring. The head of the stud rests upon the upper surface of plate 18 with the result that a firm support is provided for the upper end of the spring.

The lower end of each spring 88 extends through a nipple 82 and is flared outwardly as shown at the bottom of Figure 5. Nipple 82 is threaded into a hole in pipe 10 with its lower end providing a seat for the flared end of the spring. Springs 80 are close-wound springs of uniform size and other characteristics and during use the springs are all held under slight tension so that there is a small gap of predetermined thickness between each turn of the spring and the next adjacent turn. Thus, the spring forms a helical slit or gap extending between stud 8! and nipple 82, the length of the gap being approximately equal to the length of the wire in the spring. The uniform length of the springs permits ready assembly and easy replacement, the assembly being merely the sticking of the upper end of the spring through the hole in plate 78, the turning of stud 8| into the end -of the spring, and the turning of nipple 82 into the threaded hole in pipe Hi. When the filter unit is initially assembled, nipples 82 are turned into their holes a predetermined amount so that with the springs of equal length the gaps are equal in all of the springs. Thereafter "the gaps in all of the springs are changed simultaneously by turning studs 15 and thus moving plate 18 vertically.

The embodiment of Figure 6 differs from that of Figure in that each of springs I88 is attached to its pipe by soldering it to a nipple I82 threaded in the pipe. During assembly, the spring is suspended freely from its supporting stud 8| and its lower end extends freely into nipple I82; the spring is then soldered to the nipple. Thereafter the channel plate I8 is ad-' justed to obtain the desired filter gap in all of the springs in the same manner that the gap is adjusted in the other illustrative embodiment.

During use, suction is maintained in pipe 18 so that the coolant flows through this gap into the center of the spring and thence downwardly to pipe 10. The diameter of the spring is relatively small but is large enough to permit the coolant to flow freely. The wire from which the spring is made is of sufilcient strength to holdthe weight of the spring without appreciably extending the spring; thus the gap is uniform throughout the length of the spring. Thetension on the springs is such that the gaps prevent the passing of undesirable substances with the coolant and these substances form a deposit upon the outside of the spring. As indicated above, each filter unit is backwashed intermittently to remove this deposit. The backwash operation is carried on at such a time and .at a frequency as to suit the demands of the particular installation. Generally, it may be said that the filter unit is backwashed at the time that the flow of clean coolant from the unit is reduced below a practical minimum. For any particular conditions of operation, all of the springs in a filter unit tend to become clogged at the same time. However, the premature clogging of one or several springs of a unit or the clogging of'a part of one spring does not interfere with the operation of the remainder of the filter unit.

The backwash operation is performed by supplying clean coolant and slugs of air under pressure to the inside of springs and thus causing an agitated reverse fiow through the filter gaps. Under some circumstances, clean coolant alone may be used for backwashing but it has been found that the combined action of the clean coolant and slugs of air removes the deposited substances effectively in a minimum of time. Referring again to Figure 3, the clean coolant and air is supplied to pipes 10 through pipes 66, holders 58, pipes 54, and pipes 52 and 50. Pipe 50 receives the clean coolant and air through the backwash valve 46 from coupling 83 and pipe 84, which is connected to a pipe I22 (Figure 2) which is connected to thepipe I54 supplying coolant to the machine tools as will be explained below.

The details of the backwash valve 48 are best shown in Figures '7 and 8, there being, as shown in Figure 8, the following connections: at the right of the figure the downward connection 44 to the clean coolant suction, at the upper portion of the figure the connection 48 to the filter unit, and at the bottom of the figure a connection 85 to the supply of coolant and air for backwashing. Connection 48 is open to the central valve chamber in which is positioned a double-faced valve 88. The valve chamber is connected at the right through an opening 86 to connection 44 and at the left through an opening 98 to connection 85. The double-faced valve 88 is normally held in the full line position against seat 90 where it closes opening '84; thus, the filter unit is connected through connection 48, opening 86, connection 44, valve 42 (see Figure 3) to pipe 36 and thus to the clean coolant suction. However, when backwashing is taking place, valve 88 (Figures 7 and8) is in the broken line position against seat 92 where it covers opening 86 so that the supply of air and clean coolant from connection 85 flows through opening 94 and connection 48 to the filter unit.

Valve 88 is supported by a valve .rod 98 which is snugly received in a sleeve 91. The pressure on the left-hand face of valve 88 which results from the high pressure from connection 85 and the suction from connection 44 tends to move valve 88 from the full line position to the broken 7 line position. However, the valve is normally held in the full line position by a piston connected to the left-hand end of rod 96 and 5 positioned in a cylinder 98. Accordingly, the

left end'wall of the cylinder is open to atmospheric pressure through a pipe HI, and high pressure coolant is supplied (see Figure 7) to the right-hand end of the cylinder through a well I02 at the bottom of the cylinder. Well I02 is.connected through a threaded nipple I04 to a pipe I06 (see also Figures 3 and 8) through which the coolant is supplied and discharged.

Referring to Figure 3, pipe I06 is connected through a T-coupling I08 to a drain pipe H2 at the right, and to a fluid supply pipe I III which extends upwardly. Drain pipe II2 has a normally closed solenoid valve II4 which is opened by the energization of a solenoid IIB. Pipe H is connected through a T-coupling I I8 to an auxiliary drain pipe II5 having a normally closed valve In. The upper end of pipe H0 is connected through a needle valve II9 to a pipe I20 which is connectedto a pipe I22 (Figure 2) which in turn is connected to pipe I54 which is the supply of high pressure clean coolant, and the needle valve is partially open to permit the flow of a small stream of coolant into pipe H0 (Figure 3). Under normal circumstances, valves H4 and H1 are closed and the small stream of coolant from needle valve H0 fiows through pipe I06 where it builds up pressure in cylinder 98 and moves piston I00 (see Figures 7 and 8) to the left. After piston I00 and valve 88 reach the full-line position the pressure in cylinder 98 builds up and reaches substantially the pressure in the supply pipe I20; and valve 88 is held tightly against seat 90.

Subsequently, when it is desirable to initiate the backwash operation, solenoid H6 (Figure 3) is energized with the result that valve H4 is opened and coolant is drained from pipes I06 and H0 faster than the coolant is supplied through needle valve H9. This results in the draining of coolant from cylinder 98 and (Figures '7 and 8). piston I00 and valve 88 are moved to their broken line positions by the difference in pressures on the opposite sides of the valve. As a result, the backwash operation is started and it continues until solenoid H6 is deenergized thereby closing valve II4. Coolant which seeps past piston I00 in cylinder 98 is discharged through pipe I2I into tank 2. Any sediment which tends to collect in cylinder 98 is discharged through well I02 along with the coolant.

When the backwash operation is started the high pressure clean coolant flows from pipe I0 (Figure 5) into the lower ends of the springs 80. The pressure on the inside of each spring tends to extend the spring upwardly and thus raise the head of stud BI away from the upper surface of plate I8. This increases the width of the gap. in the spring so that the spring is fiexed; the movement assists the coolant and air in dislodging the deposit on the spring. The air causes the coolant to surge and this gives an added action. The efiect is very pronounced when the springs are badly clogged by the deposit so that a high pressure is built up within the springs.

The pipe connections for the system are shown best in Figures 1 and 2. The supply of clean coolant for backwashing is carried by pipe 84 which is connected at the right to a pipe I22. Near the top of the right-hand filter unit I0d (see Figure 2) is an air connection I23 through which air is supplied to pipe 84 through a pipe I24; a check valve I26 permits flow to the right only. Referring to Figure l, at the right of air connection I23 is a check valve I28 which permits liquid to flow to the left but which prevents the liquid with air added to it from flowing to the right. Check valve I26 in pipe I24 performs a similar function by permitting air to flow into pipe 84 and preventing the reverse flow. Liquid and air aresupplied at substantially the same pressure and it has been found that a substantial amount of air is carried with the liquid to the filter units. As indicated above, the deposit which is released from the springs falls to the bottom of tank 2. In this embodiment the filter units are backwashed individually under the control of an electric timer all in a manner to be more fully explained below. The deposit which is dislodged from one filter unit during backwashing should not be drawn onto the springs of another filter unit. Accordingly, mounted between each filter unit and the next filter unit is a bafiie I30 which causes the dislodged deposit to settle to the bottom of the tank. At the end of the backwash operation the filter unit remains idle for a short period of time thus permitting the dislodged deposit to settle.

As shown best in Figure 1, at the left of the group of filter units is a spray unit I32 which has four spray heads each directing a fan-shaped spray of clean fiuid to the left against the surface of the coolant. Between filter units I0b and We is a similar spray unit I34 which also directs fan-shaped sprays to the left along the surface of the coolant. These sprays of coolant tend to stop surface movement toward the filter units so that floating substances are kept away from the top of the filter units. Furthermore, these sprays V tend to destroy foam and to submerge floating solids.

The coolant supply for the spray units I32 and I34 is received through a pipe I36 which is connected by a coupling I38 to two branch pipes I40 and H, the other ends of which are connected through a supply pipe I42 to pipe I22. Pipe I40 extends over the top of centrifugal pump 38 and, as shown in Figure 2, is connected to the top of the outlet of the pump through a vertical pipe I44. Similarly, pipe I4I extends over the top of pump 32 and is connected to the pump through a vertical pipe I46. The flow of coolant through pipes I40 and I4I to the sprays is sulficient to carry away constantly any air which .tends to collect in the centrifugal pumps and the centrifugal pumps are constantly primed by the high pressure coolant in these pipes; thus, the centrifugal pumps provide a steady and unfailing suction upon their respective filter units.

As indicated above, the clean coolant is delivered to chamber 6 and this chamber holds the reserve supply of clean coolant. Excess coolant flows over the top of partition 8 into the main body of coolant so that the top of partition 8 acts as a wier to maintain a constant liquid head in chamber 6 so that the pressure is constant at the bottom of the chamber. Air in the coolant tends to come out in chamber 6 so that there is always air-free clean coolant at the bottom of the chamber. As shown best in Figure 2, this coolant is drawn from chamber 6 through a pipe I48 by a centrifugal pump I50 and delivered under pressure to a vertical pipe I52. The constant pressure at the bottom of chamber 6 insures a constant outlet pressure from pump I50. Centrifugal pumps 32, 38, and I50 will handle any coolant which is passed by the filter units I0, and

even when small particles remain in the coolant the pumps are not damaged and do not suffer from excessive wear. a

Pipe I52 is connected at itstop toa horizontal pipe I54 which, as shown in Figure 1, passes to the side or the tank, where it connects to pipe 122., referred to above, and also to pipe I56. which extends. to the machine tools. At the side of pump I50 (see Figure 1) is a drain pipe I58 having. a normally closed valve I69 which is opened to drain coolant from the system.

Under some circumstances, it may be necessary to close down all of the filter units at once or the filter units might become inoperative due, for example, to clogging without the operator becoming aware of the situation. However, it is important to maintain a supply of coolant to certain machine tools as they would be severely damaged if they were operated without coolant.

Accordingly, partition, 8 has a, normally-closed one-way valve I62 midway between the top and bottom of the partition which opens automatically when desirable to permit coolant to flow into chamber 6 from the main body of coolant. This valve extends at an angle upwardly to the right from partition 6 into chamber 6 and it has a valve flap I64 hinged at its upper edge and weighted to hold the flap down. The valve is open at the left to the main supply of coolant and the bottom wall of the valve slants at such an angle that any particles which fall uponthe bottom wall are deflected to the left and thence fall to the bottomof tank 2.

During normalconditions, with the liquid level in chamber I5 above or equal to the liquid level in. the main tank, the weighted flap is held down by the action, of gravity and the added action of any favorablepressure difference. However, if the liquid level in chamber 6 falls to the level of valve I62, the liquid pressure at the left of the valve overcomes the force of gravity holding flap I64 down and the flap is raised permitting liquid from the main body to flow through the valve into chamber 6; thus, chamber 6 will besupplied with coolant even though the filter system is. not operating. It should be noted that the position of valve I62. is such that partially clean coolant flows into chamber 6 through the valve; that is, valve I62 is above the bottom of the tank where the sludge formed by large particles and the deposit from the filter units tend to settle. Furthermore, the valve is below the top of the liquid where the lighter particles tend to float and the valve is at the opposite end of the tank from the supply of dirty coolant. I

The. sludge which collects on the bottom of the tank is removed by an endless chain assembly formed by two endless chains (Figure 1.) I65 and a number of spaced scrapers or flights I68 which are in the form of channel members each attached at its edgeto the endless chains; Each. chain extends (Figure 2) around a sprocket wheel at the right-hand end of tank 2, along the bottom of the tank to a sprocket wheel I12, up the slanting end wall of the tank to a sprocket wheel I14, and thence to the right over a sprocket wheel I16 and down into the tank to sprocket wheel I10. Welded to each side wall of the tank is an angle bar I I8 upon which the ends of flights I68 slide as they move beneath the filter units; the angle bars guide and support the flights and the adjacent portions of chains I66 and the flights and chains moving toward sprocket wheels I70 do not disturb the sludge on the bottom of the tank. Each pair of the sprocket wheels is mounted on a shaft (see Figure 1) which is supported at the two sides of the tank. Sprocket wheels H4 have a shaft I 84 which isdriven at one end through a belt 186 by a, motor I88; as shown in Figure 2, the tension, of belt I86 is adjusted by an idler pulley I90. The flights I86 are moved slowly across the bottom of tank 2 and up end wall 4. At the, top, of the end wall the sludge carried by each flight. is discharged over the top of the end wall and into an adjustable chute I522 from which it falls to a refuse can I94.

As indicated above, .the backwash operation is started and stopped automatically by an electric timer I95, the functioning of which will be explained in connection with Figure 9. Timer I has its. motor I91 connected at one side to. a line I99 and, at. the other side to a line 200. Line 200 is. connected to a lin 204. through a manual switch 202 which is normally in the right-hand position as shown and lines I99 and 204 are connected through, a, normally closed switch 206 to a source of power. Timer I95 has an armature Z08 which-is also connected to. line 200 and which engages four contacts 2I9, in series so as. to energize each of these contacts for a predetermined period at stated intervals. Each of the contacts 2 I0 is connected to one side of one of the solenoids IIIiof valves. H4. and the other side of each of these solenoids is connected to. line. I 99. Thus the solenoid are energized at spacedintervals each for a predetermined time and as pointed out above the backwashv operation for each of the filter units is carried on. during the time that its solenoid H6 is energized. It is thus seen that for example at stated periods, the timer backwashes. the filter unit I0a, and when this operation is completed filter units Itlh, I00 and I001 are backwashed in succession. The timer may be adjusted with. respect to. the timerfrequency and duration of the backwash operations.

Under some circumstances, it is desirable to backwash a' filter unit only when the flow rate. of the coolantthrough, the, unit i substantially reduced. To obtain this result switch 202 is. turned manually from the normal position where the. timer controls thebackwash operation to a secondary position at the left where the backwashing is under the control of the flow rate of the coolant. As indicated above, pumps 32 and 38 are of the centrifugal type, and the suction maintained by them is increased when the flow is restricted by an excessive deposit. This characteristie of the centrifugal pump is utilized to initiate the backwash operation on the units in accordance with the reduction in the flow rate of the coolant. This is accomplished by providing at the left-hand end of each of pipes 30 and 36, a pressure gauge I96 (see Figure 2) which is providedwith a gauge switch ZIZ which closes when the gauge indicates a predetermined pressure in the pipe. The closing of each gauge switch initiates a backwash. cycle for the two filter units connected to that particular gauge so that each backwash cycle is initiated by one of the gauges I96. However, the backwashing is carried on for a predetermined time in the same manner as when the timer is controllin the entire operation.

The initiation of the backwashv cycles upon the closure of auge switches 2I2 is accomplished by means of relays 2I6 (Figure 9). There are two of these relay switches 2I6 which are identical, the right-hand one of which controls the back-v washing of filter units I00 and I001, and the lefthand one of which controls the backwashing of filter units I Illa and lb. The operation or the right-hand relay 2I6 will be described in detail, with the understanding that the left-hand relay is constructed and operates in an identical manis raised immediately so that contacts 2|! and l 2H8 are connected to line 2M, and this energizes solenoids H6 and initiates the backwash operation, as described above, and the backwash opeiation continues as long as armature 2I5 is raised. The lifting of armature 215 opens switch 2 i i so that winding 2 I3 is deenergized. However, the relay has a dash pot 2I9 mechanically connected to armature 2 l 5 which holds the armature up for a predetermined time after winding 2l3 is deenergized. This dash pot gives the relay a delayed opening characteristic whereby solenoids H6 are held energized for a predetermined time after the relay is deenergized. This period of time is the time required for completion of the backwash operation, and at the endlof this time the armature drops slowly and the filter units are returned to their normal filtering operation. During the backwash operations, the centrifugal pumps 32, 38, and E50 continue to operate.

In practice, it is desirable to maintain a reserve l supply of clean coolant at all times; thus, the system is able to handle unpredicted emergency demands. The continued operation of the filtering process during periods when there is very little or no demand for clean coolant raises the standard of purity of the main body of coolant to a point that the main body of coolant is substantially free of foreign particles. In this way, when an excessive load is placed on the system, the filter units continue to operate efficientlyi because they do .not become clogged and the excessive load is carried without bringing the standards of purity of the coolant below the desired value.

As many possible embodiments may be made of the mechanical features of the above invention and as the art herein described might be varied in various parts, all without departing from the scope of the invention, it is to be understood that all matter hereinabove set forth,'or shown in the accompanying drawings, is to be interpreted as illustrative and not in a limiting sense.

We claim: V

1. In a system for removing substances from liquid, the combination of, an elongated horizontal tank containing the liquid and having an outwardly slanting end wall at one end thereof, means forming an end chamber for clean liquid at the end of the tank opposite said slanting end wall, an endless chain assembly mounted to move longitudinally of said tank and having spaced means which are moved successively from the end of the tank opposite said slanting end wall along the bottom of the tank and up along said slanting end wall thereby to discharge sludge from the tank, a plurality of filter units positioned within said tank below the normal liquid level in the tank whereby the filter units are immersed in liquid, said filter units being adapted to have liquid withdrawn therethrough, pump means connected to draw liquid from said filter units and to discharge the liquid in said end chambenand means to deliver liquid to the end of the tank opposite said end chamber beneath the normal liquid level and substantially in the direction of said slanting end wall.

2., Apparatus as described in claim 1 wherein said means forming said end chamber has a weighted valve substantially above the bottom of said tank and below the normal liquid levels in the end chamber and tank which valve is adapted to be opened by the differential of liquid pressure on the two sides of the valve when the liquid level in said end chamber falls a predetermined amount below the level in the tank.

3. In a system as described in claim 1 wherein the liquid being filtered is coolant and which includes, pump means to pump clean coolant from 1 said end chamber and valve means connected between the pump means and the filter units whereby the filtered coolant normally flows from said filter units and which valve means is oper-' ated to stop the normal flow and to direct the clean coolant from said pump means to said filter unit.

4. In a system for supplying clean coolant of the emulsion type to a bank of machine tools, the combination of, an elongated settling tank for the dirty coolant positioned horizontally and having a slanting end wall, partition means at the end of said tank opposite said slanting end wall and dividing off the end of said tank as an end chamber for clean coolant, said partition means having a wier at its top edge above the normal level of dirty coolant in said tank whereby excess clean coolant flows from said end chamber over said wier to the dirty coolant, a plurality of filter units positioned between said partition means and the central portion of said tank below the normal liquid level in the tank and with a free space beneath the filter units into which dirt may settle from the coolant, said filter units each being formed by a plurality of vertical coil springs having predetermined gaps between the adjacent turns and means to direct a flow of coolant from the bottom of each spring whereby clean coolant fiows through the gaps in the springs and the dirt is collected about the springs, means to pump the clean coolant from the filter units to said end chamber, means to reverse the flow of coolant in the various filter units whereby the dirt collected about the springs is released and falls to the bottom of the tank, a dirt-removing mechanism formed by a pair of endless chains mounted longitudinally of the tank and having spaced scraping means mounted as flights upon the chains'so that as the chains are moved the flights are successively moved along the bottom of the tank from the end adjacent said partition means to said slanting end wall and thence up along said slanting end wall to discharge the dirt collected, and means to withdraw clean coolant from said end chamber. r 5. Apparatus as described in claim 4 which includes, means to supply clean coolant to perform the reverse flow operation, and means to add air to the clean coolant at substantially the same pressure as the clean coolant, whereby slugs of air and coolant are delivered to the springs.

6. In a system for supplying clean coolant to machine tools, the combination of, a horizontally elongated tank for the dirty coolant with the body of dirty coolant occupying a relatively large and horizontally disposed space, partition means adjacent one wall of said tank and forming a chamber for clean coolant which has at the top a wier discharging excess clean coolant from saidchamber into the body of dirty coolant, a plurality of filter units mounted adjacent said part1- tion means below the normal liquid level in the 'tank and with each filter unit formed by a plurality of coiled springs, means to add dirty coolant to the tank in a zone remote from said filter units, bafiie means to direct the incoming dirty coolant in a downward direction toward the central portion of the tank and to direct the floating matter along the surface of the dirty coolant toward the central portion of "the tank, pump means to pump the clean coolant under pressure, spray means connected to the last-named means and directing a spray of the clean coolant against the surface of the dirty coolant in a surface zone separating the surface of the dirty coolant above said filter units from the remaining surface of the dirty 'coolant with the spray being directed so as to cause a surface movement away from the area above the filter units, said spray being effective to destroy foam and to sink other fioating substances, rake means to remove dirt collected on the bottom of said tank without materially interfering with the filtering and settling opera tions, and means to reverse the flow of coolant in each of said filter units whereby the dirt collected is released so that it may settle to the bottom of the tank.

7. Apparatus as described in claim 6 which includes, centrifugal pump means positioned above said chamber and connected to withdraw clean coolant from the filter units, pipe means connected to said spray means to supply the clean coolant thereto, said pipe means extending across the top of said centrifugal pump means and being connected thereto whereby air which tends to collect in said centrifugal pump means is carried away to said spray means.

8. Apparatus as described in claim 6 wherein the clean coolant is delivered to said end chamber below the normal liquid level in the end chamber and which apparatus includes, a centrifugal pump connected to the bottom of said end chamber to withdraw clean coolant therefrom, whereby air in the clean coolant escapes and air-free coolant is withdrawn by said centrifugal pump.

9. In a filter system wherein fluid is filtered by drawing it through a filter unit which is immersed in a body of the unfiltered fluid with the result that the substances being filtered from the fluid form a deposit on the filter unit and wherein a supply of clean fluid is pumped into i the filter unit to discharge said deposit, fluid control means connected to the filter unit to control the drawing of fluid from the filter unit and the reverse flow of the fluid comprising: a doubleacting valve having a valve element and a central valve chamber which has an opening connected to the filter unit and in which chamber the valve element is positioned, and wherein said valve chamber has at one side a supply opening through which it is connected to a supply of clean fluid under pressure and has on the side opposite a fluid discharge opening through which the clean fluid from the filter unit is pumped, said supply and discharge openings each having a valve seat against which said valve element may be positioned to close the opening; and motive means to move said valve element between the two positions against said seats of said supply and discharge openings, said motive means comprising, a piston rod, a piston-cylinder unit having a cylinder and a piston positioned therein, said piston being rigidly connected by said piston rod to said valve element, and a fluid supply means through which fluid is supplied to said cylinder at one side of said piston with sufficient pressure to move said piston to one extreme position with the valve element closing of clean coolant. I

10. Apparatus as described in claim 9 which includes a needle valve connected in the inlet from said fluid supply means to said cylinder whereby the fluid is supplied to'said cylinder at a slow rate, and fluid discharge means to release the fluid from said cylinder at a more rapid rate than the fluid is supplied through said needle valve whereby the fluid pressure within said cylinder is released and the fluid pressure of the coolant at said openings and within said chamber moves said valve element against the valve seat of the opening through which the coolant is pumped.

11. In a filter system, thecombination of,v an elongated horizontal tank having a vertical side wall,a plurality of'filter units adjacent. one end of said tank and positioned in parallel relationship transversely of said tank below the normal liquidlevel in the tank, a connecting pipe assembly connected to said filter units including parallel pipes extending over the top of said side wall, means to deliver the liquid to be filtered beneath the surface of the liquid at the end of the tank opposite said filter units, means to withdraw the filtered liquid from said filter units thereby to form a deposit on each of said filter units, means constituting a supply of fluid to be delivered to said filter units whereby the flow through the filter units is reversed and the deposit is released, and means to control the flow to and from said filter units comprising a valve assembly associated with each of said filter units including a fluid control system and solenoid means to regulate said fluid control system.

12. In a filter system, the combination of, an elongated horizontal tank, means to deliver the liquid to be filtered to said tank at one end thereof, a plurality of filter units at the opposite end of said tank below the liquid level in the tank, means forming a chamber for filtered liquid adjacent said filter units and having a wier at its top through which excess filtered liquid flows from said chamber into the body of unfiltered liquid, means to withdraw filtered liquid from said filter units and to deliver said filtered liquid to said chamber, a weighted valve connecting the body of filtered liquid in said tank to said chamber at a point above the bottom of said tank and below the normal liquid level in the tank, pump means to pump clean coolant from said chamber and thence in a reverse direction through said filter units whereby materials filtered from the liquid the opening to the supply are released from the filter units, and baflle means between two adjacent filter units to deflect the released materials from one filter unit away from the other filter unit.

13. In a filter system, the combination of, an elongated horizontal tank constituting a container for a body of unfiltered liquid, means to deliver the unfiltered liquid to said tank at one end thereof whereby the large suspended particles may settle by gravity, means to project an intense I spray of liquid against the surface of the body of the unfiltered liquid whereby foam is destroyed and floating substances are immersed and caused to sink, a plurality of filter units positioned in the body of unfiltered liquid at the end thereof opposite the zone where the unfiltered liquid is delivered to the tank, means to withdraw filtered liquid from said filter units to store a substantial quantity of the filtered liquid, means to backwash the filter units individually by reversing the fiow of liquid therethrough, and means to scrape the particles collected at the bottom of the body of liquid from the end of the tank opposite the end at which the filter units are positioned.

FRANCIS J. ARMSTRONG.

Number Number HENRY F. HAMLIN. 5

REFERENCES CITED The following references are of record in the file of this patent: 10

UNITED STATES PATENTS 7 Number Name Date 630,958 Wilson Aug. 15, 1899 654,592 Barr July 31, 1900 1,187,772 Ohm June 20, 1916 15 1,518,642 Emmet Dec. 9, 1924 r 1,530,077 Haynes Mar. 17, 1925 1,591,229 Oliver et al July 6, 1926 1,603,625 Mitchell Oct. 19, 1926 1,642,673 Genter Sept. 20, 1927 Name Date Oliver Oct. 11, 1927 Vernay Mar. 13, 1928 Sweetland Aug. 13, 1929 Cruickshank Nov. 12, 1929 Heibig Oct. 14, 1930 Marsh Sept. 19, 1933 Currie Nov. 20, 1934 Chesny May 19, 1936 Boosey May 25, 1937 Hirshstein Dec. 20, 1938 Malanowski Nov. 10, 1942 Olson May 7, 1946 FOREIGN PATENTS Country Date France Sept. 8, 1924 France June 5, 1927 Australia of 1926 Certificate of Correction Patent No. 2,494,534 January 17, 1950 FRANCIS J. ARMSTRONG ET AL.

It is hereby certified that errors appear in the prmted specification of the above numbered patent requiring correction as follows:

Column 5, line 51, for pipe 10 read pipe 70; column 6, line 34, for holders 58 read headers 58; column 14, line 49, for the word filtered read unfiltered;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 20th day of June, A. D. 1950.

THOMAS F. MURPHY,

Assistant Oommz'ssz'oner of Patents.

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