US3720288A

US3720288A - Lubrication system for grinding mill or the like

Info

Publication number: US3720288A
Application number: US00170089A
Authority: US
Inventors: D Tschabold
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1971-08-09
Filing date: 1971-08-09
Publication date: 1973-03-13
Anticipated expiration: 1990-03-13

Abstract

In combination with a grinding mill or the like having a trunnion supported by a stationary bearing structure to define a ''''free bearing'''' which permits axial contraction of the grinding mill during the cooling-off period after mill shutdown, a high pressure lubrication system including a high pressure pump for applying hydrostatic pressure to the ''''free bearing'''' during the mill cooling-off period whereby to ''''float'''' the trunnion in the stationary bearing structure, and timing means activated upon shutdown of the grinding mill to automatically provide ''''onoff'''' cycling of the high pressure lubricating pump.

Description

United States Patent [191 Tschabold 1Mal'Cll 13, 1973 1 1 LUBRICATION SYSTEM FOR GRINDING MILL OR THE LIKE [75] Inventor: Donald F. Tschabold, West Allis,

Wis.

[73] Assignee: Allis Chalmers Corporation, M11- 7 waukee,Wis.

[22] Filed: Aug.9, 1971 21 Appl. No.: 170,089

[52] US. Cl ..184/6.4, 241/D1G. 20, 308/122 [51] Int. Cl... ..Fl6n 29/02 [58] Field of Search 84/6.1, 6.3, 6, 6.4; 241/176,

241/285, DIG. 20; 308/122, 73

[56] References Cited UNITED STATES PATENTS 3,374,863 3/1968 Kozlowski et a1. ..l84/6.3 3,231,046 1/1966 Ohrnberger ....184/7 R X 2,934,861 5/1960 Engel 184/64 X FOREIGN PATENTS OR APPLICATIONS 740,590 11/1955 Great Britain ..184/6.3

Primary Examiner-Manuel A. Antonakas Attorney-Robert C. Sullivan et a1.

[ ABSTRACT In combination with a grinding mill or the like having a trunnion supported by a stationary bearing structure to define a free bearing" which permits axial contraction of the grinding mill during the cooling-off period after mill shutdown, a high pressure lubrication system including a high pressure pump for applying hydrostatic pressure to the free bearing during the mill cooling-off period whereby to float the trunnion in the stationary bearing structure, and timing means activated upon shutdown of the grinding mill to automatically provide on-off cycling of the high pressure lubricating pump.

8 Claims, 5 Drawing, Figures PATEHTEDH.\R13IU75 729,2

SHEET 2 n? 3 OLP-l HIGH PRESSURE PUMP MOTOR LOW PRESSURE PUMP MOTOR S LP Pmnnmm 31m 720,288

SHEET 30F 3 c CRAA' R 2A cR-aA' PHQ TO MILL MOTOR STARTING CIRCUIT LUBRICATION SYSTEM FOR GRINDING MILL OR THE LIKE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a lubrication system for rotary drums of the type having bearing journals integral therewith, such as grinding mills having integral trunnions which are supported for rotation by stationary bearings at opposite ends of the grinding mill.

The invention will be described as embodied in a lubricating system for a grinding mill but it will be understood that the invention is applicable to lubrication systems for analogous rotating machinery.

2. Description of the Prior Art Grinding mills are conventionally provided with trunnions extending from opposite ends of the rotary grinding mill drum and adapted to be supported for rotation by stationary bearings. Such trunnions are generally supported by the stationary bearing only beneath the lower surface portion of the rotating trunnion, with the trunnions being open and uncovered on the upper peripheral surface thereof.

The bearing arrangement at one end of the grinding mill structure has generally been known in the art as the held bearing since the rotating journal at the held endincludes peripheral flanges which are closely spaced relative to the opposite axial ends of the stationary bearing thereby permitting only a very small axial movement of the rotatable journal or trunnion relative to the stationary bearing structure at the held bearing. The bearing structure at the opposite end of the grinding mill is known as the free bearing" since the peripheral flanges on the rotatable journal member are spaced from the corresponding axial ends of the stationary bearing by a greater distance than in the case of the held bearing. Thus, the free bearing will permit free axial contraction of the mill during the mill off" period when the mill is cooling to ambient temperature after shutdown.

During the operation of a grinding mill, the mill heats up due to the frictional forces inside the mill produced by the grinding operation. Heat is also generated at the trunnion and stationary bearing structure. As a result of this heat the grinding mill expands in length while in operation and contracts in length during the cooling-off period after shutdown.

It has been well known in the prior art to apply high pressure lubrication which may be of the order of magnitude of 1500-2500 pounds per square inch, for exam ple, beneath the surface of the journal or trunnion, particularly at the free" bearing end of the grinding mill, whereby to apply hydrostatic lubrication beneath the trunnion of the mill at shutdown. This high pressure hydrostatic lubrication floats the trunnion in the bearing to permit free axial contraction of the mill as the mill cools down after shutdown, preventing metalto-metal contact between the trunnion and the stationary bearing which would cause scoring of the metal bearing surfaces if the high pressure lubricant were absent.

It has been known in the prior art to provide a control arrangement which automatically turns on the high pressure lubricating system to apply the hydrostatic lubrication at the free" bearing as just described upon mill shutdown. However, such control systems of the prior art depended upon a manual shutoff operation by the operator, and the high pressure lubrication system would continue to operate until manually shut off by the operator. Sometimes, the operator would fail to shut off the high pressure lubricant pump in accordance with operating instructions with the result that the high pressure lubricating pump would run for an excessively long time after the mill had cooled down after shutdown.

This excessive length of operation of the high pressure lubricant pump without shutdown thereof would frequently result in mechanical failure of the pump. In addition to the continuous operation of the pump as a cause of pump failure, a contributing factor to the pump failure may be the fact that the high pressure lubricant being pumped may contain certain small size contaminants which it is impractical from a cost or commercial standpoint to attempt to filter out but which ultimately may cause damage to the high pressure pump, particularly when the high pressure pump is operated for excessive lengths of time. In accordance with the present invention, the contaminant problem may still exist but is reduced in seriousness due to the fact that the time element of the duty cycle of the high pressure pump after mill shut-down has been greatly reduced to provide an acceptable pump life.

It has also been known in the prior art to instruct the operators of such grinding mills or the like after shutdown of the mill to periodically turn on the high pressure lubricating system at the free bearing for short periods during the mill shutdown while the mill is cooling off. However, experience has proven that such instructions are frequently not adhered to by operating personnel.

STATEMENT OF THE INVENTION Accordingly, it is an object of the present invention to provide an automatic lubricating system for grinding mills or the like in which a cycling on-off operation of the high pressure lubrication system is initiated automatically upon shutdown of the grinding mill or the like whereby to insure a continuous and adequate supply of high pressure lubricant to the free bearing structure of the grinding mill during the cooling-off period after mill shutdown during which the 'mill is contracting in length.

It is another object of the invention to provide a lubrication system for the free bearing of a grinding mill or the like during the cooling-off period after shut down of the mill, which is more efficient than prior art lubrication systems for this purpose, and which insures a minimum of wear on the high pressure lubricating pump to thereby increase the life of the high pressure lubricating pump.

In achievement of these objectives, there is provided in accordance with an embodiment of this invention the combination with a grinding mill or the like having a trunnion supported by a stationary bearing structure to define a free bearing which permits axial contraction of the grinding mill during the cooling-off period after mill shutdown, a high pressure lubrication system including a high pressure pump for applying hydrostatic pressure to the free bearing" during the mill cooling-off period whereby to float the trunnion in the stationary bearing structure, and timing means activated upon shutdown of the grinding mill to automatically provide on-of cycling of the high pressure lubricating pump.

Further objects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view in axial elevation of a grinding mill showing the held bearing at one end and the free bearing at the other end thereof;

FIG. 2 is a flow diagram of the low pressure and of the high pressure lubricating systems for the trunnion bearing at one end of the grinding mill, combined with a view in vertical section along the line II-II of FIG. 1;

FIG. 3 is a schematic diagram of the electrical control circuitry for the low pressure and high pressure lubricating systems of FIG. 2;

FIG. 4 is a schematic circuit diagram of the electrical interlock arrangement between the lubrication control system of FIG. 3 and the motor starting circuit of the grinding mill being lubricated; and

FIG. 5 is a schematic diagram showing the electrical warning circuit controlled by the control circuitry of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings and more particularly to FIG. 1, there is shown a rotary grinding mill generally indicated at comprising a rotary drum 12, a feed trunnion 14 at one end of the mill and a discharge trunnion 16 at the opposite end of the grinding mill. Mill 10 is rotatably driven by suitable drive means, not shown. The trunnions 14 and 16 are supported for rotation by stationary bearing

structures

18 and 20, respectively. It will be noted that the inlet or feed trunnion 14 is provided with a pair of axially spaced peripheral flanges 22 and 24 which are respectively contiguous the opposite axial ends of the stationary bearing structure 18. The clearance between each of the respective peripheral flanges 22 and 24 with respect to the facing surface of the corresponding end wall of the stationary bearing structure 18 is very small and is of such value as to substantially prevent any axial movement of trunnion 14 relative to stationary bearing structure 18. Thus, the trunnion or journal 14 and the associated stationary bearing 18 referred to in the art as the held bearing.

On the other hand, the

peripheral flanges

26 and 28 of discharge trunnion 16 are spaced from the corresponding end faces of the stationary bearing structure by an axial distance such as to permit some degree of axial movement such as 0.4-1.0 inch, for example, of trunnion 16 relative to the stationary bearing structure 20 during the axial contraction of the mill in the cooling-off period after shutdown. Hence, the trunnion or journal 16 and the associated stationary bearing structure 20 are referred to in the art as the free bearing.

It will be noted (see FIG. 2) that the respective trunnions 14 and 16 are supported beneath only a part of the peripheral extent of the under surface of the respective trunnions 14 and 16, such as 120, with the major portion of the peripheral surface including the upper peripheral surface of the respective trunnion members being uncovered and open.

A separate low pressure lubricating system and a separate high pressure lubricating system including separate low pressure and high pressure pumps and separate electrical control circuits therefor are provided for the bearing structures at each end of the grinding mill. In general, the lubricating systems at the two ends of the mill are essentially duplicates of each other, insofar as piping, pumps, and high pressure and low pressure flow circuits are concerned. The system at the free bearing 16-20 differs from the system at the held bearing 14-18 principally in that the on-off cycling system and cycling control circuit used for the high pressure lubrication system at the free bearing after mill shutdown is not employed at the held" bearing 14-18. Instead, at the held bearing the low pressure and high pressure lubrication pump systems are operated at shutdown of the mill for a predetermined length of time, such as 15 minutes, and then shut off permanently until the mill is being prepared for restarting.

The low pressure and high pressure lubrication systems at the free" bearing 1620 will be described, it being understood that much of this descriptive matter also applies to the low pressure and high pressure lubrication systems at the held bearing structure 14-18 as qualified by the discussion in the preceding paragraph.

As best seen in FIG. 2, the low pressure lubricant is supplied to the journal or trunnion 16 by a conduit 36 which extends to an outlet 38 vertically positioned above trunnion 16. During the operation of the grinding mill, the low pressure lubricant passes outwardly through discharge outlet 38 and falls onto the upper surface of the rotating trunnion 16, the lubricant then flowing down the surface of the rotating trunnion '16 and into a scoop or wedge 40 contiguous the rotating surface of trunnion 16, from whence the low pressure lubricating oil is drawn by the rotating trunnion into the interface between the rotating trunnion l6 and the upper or facing surface of the stationary bearing member 20.

The high pressure lubricant passes through a conduit 42 which is connected to a lateral passage 44 in the stationary bearing structure 20. The lateral passage 44 communicates with a vertical passage 46 which terminates at an opening 48 through which the high pressure lubricant is admitted at the interface between trunnion member 16 and the stationary bearing structure 20. The low pressure oil and the high pressure oil both are returned from a common sump 49 by conduit 50 to the inlet of the low pressure pump as will be explained more fully.

The return conduit 50 from the oil sump is connected through a heater 61 to the inlet of low pressure pump 52, which is driven by low pressure pump motor M-2. Pump 52 delivers low pressure oil to conduit 54. The output conduit 54 from low pressure pump 52 is connected to a filter 57. The oil flow in conduit 54 of the low pressure system continues past a junction 58 and through a spring biased resistance check valve 60 and thence through a flow switch indicated at FLP. After passing through flow switch FLP, the low pressure oil flows through conduit 36 which delivers the low pressure oil to the upper surface of trunnion 16. Low pressure pump 52 may typically deliver oil at a pressure such as 50 pounds per square inch at the pump outlet.

An inputconduit 62 to high pressure pump 64 is connected to the low pressure line 54 at junction 58, so that some of the lubricant from the low pressure system will pass through the line 62 to the inlet end of high pressure pump 64. High pressure pump 64 is driven by an electric motor M-l. The function of the resistance check valve 60, to which reference was previously made, is to provide a sufficient back pressure in the

conduits

54 and 62 to ensure that oil from the low pressure system is available at all times to the high pressure lubrication system is and when high pressure pump 64 is started up as will be explained hereinafter. When high pressure pump 64 is operating, the oil is directed from pump 64 at a pressure which may be of the order of magnitude of 1500 to 2500 pounds per square inch, for example. The oil passes from pump 64 through the output line 42 in series with check valve 66 which prevents reverse flow of oil into high pressure pump 64. A dual pressure switch, generally indicated at 68, is connected to high pressure line 42 downstream of check valve 66. Dual pressure switch 68 includes a switch indicated at LHP, which closes a normally open electrical contact when the pressure of the lubricant in the high pressure system reaches a predetermined minimum value (see the electrical schematic diagram of FIG. 3); dual pressure switch 68 also includes a switch designated at HHP which operates a normally closed electrical contact to open position when the pressure in the high pressure conduit 42 rises above a predetermined maximum value (see schematic electrical diagram of FIG. 3). Pressure relief valve 70 is also connected to the high pressure line 42.and a pressure gauge 72 is connected to the high pressure line 42. As previously explained, conduit 42 delivers the high pressure lubricant to the interface between the trunnion 16 and the stationary bearing 20.

DESCRIPTION OF ELECTRICAL CIRCUITRY AND OPERATION THEREOF Referring now to FIG. 3, it will be seen that the high pressure lubrication pump motor M-1 and the low pressure pump motor M2 are connected to electrical power through a circuit breaker CB. The three power lines L1, L2 and L-3 are connected to high pressure pump motor Ml each respectively through a normally open contact M-IA, controlled by starting relay coil MlR. Similarly, each of the power lines L-l, L-2 and L-3 is connected to the low pressure pump motor M-2 in series with a normally open contact MZA. Overload protective devices OLP-1 and OLP2 are connected in the input power connections to the respective motors M1 and M-2. In addition, an overload protective device OL-1 protects relay coil MlR and an overload protective device OL-2 protects relay coil MZR from excessive control circuit current. Sealing-in contact M-2RA is controlled by starter relay coil M2R. Heater 61 is connected to the electrical power lines L1, L2 and L-3 in series with normally open contacts M3A which are controlled by relay coil M3R. The control circuitry is connected across control power lines 101-402 which derive electrical power through a protective device or fuse FU from the secondary side of a step-down transformer generally indicated at 100. Starting Up Operation of Lubrication System Assume that the grinding mill or the like is shut down and that is desired to start up the: grinding mill. Before starting the grinding mill up it is necessary that the lubrication system be started in operation. Hence, the first step is to manually momentarily close low oil pressure starter button S-LP to initiate operation of the low pressure lubricating system. It will be noted that closure of low pressure system start button S-LP energizes relay coil M-2R which is connected across the

control power lines

101 and 102 in series with pushbutton contact 78A of the pump system stop pushbutton 78 and in series with the overload contact OL-2. Both the contacts 78A and OL-2 are closed at the time of startup of the low pressure system, and hence a circuit is completed to energize relay coil M2R when pushbutton switch S-LP is momentarily closed. The energization of relay coil M-2R closes normally open contact MZRA, which is a sealing-in contact for relay coil M2R. Hence relay coil M-2R remains energized after the momentarily closed pushbutton S-LP is released to open position.

Energization of relay coil MZR also closes the normally open contacts M2A in the three input power lines to low pressure pump motor M2 so that the low pressure pump motor M2 begins operation to cause low pressure pump 52 to pump low pressure oil through the low pressure lubrication circuit. Energization of relay coil M2R also closes normally open contact M-2RB in the circuit of relay coil M-lR which controls the high pressure pump motor as will be explained hereinafter. Thus, the closure of contact M2RB sets up the circuit of relay coil MlR to permit energization of relay coil M-1R when the start pushbutton S-HP for the high pressure pumpcircuit is closed.

Energization of relay coil M2R also results in the energization of relay coil M3R which controls heater 61, since, as seen in FIG. 3, a circuit is completed through sealing-in contact MZRA and thermostat contact TT which is closed when the oil is at a temperature requiring heating. Thus, relay coil M3R is energized to close normally open contacts M3A in the electrical supply circuit of heater 61 to thereby energize heater 6] to heat the oil to a desired temperature. When the oil reaches a predetermined temperature, the thermostat contact TT opens to deenergize relay coil M3R and thereby open contacts M-3A in the electrical input circuit of heater 61.

When the oil flow in the low pressure lubrication circuit reaches a predetermined minimum flow value, flow switch FLP closes and thereby energizes relay coil CR-3. Energization of relay coil CR-3 closes contact CR-3A in the circuit of the mill motor starter (FIG. 4). It will be noted that the circuit of the mill motor starter is connected in series with normally open contacts CR1A, CR-ZA, and CR-3A, which are associated with the control circuit of the free bearing and also in series with corresponding normally open contacts CR-1A', CR-2A', and CR-3A, which are associated with the control circuit for the held bearing at the opposite end of the grinding mill or the like. Before the mill motor can be started, all of the normally open contacts just enumerated must be closed. The proper minimum low pressure oil flow condition at the free" mill bearing will close the contact CR3A as just described.

Energization of relay coil CR3 by closure of low pressure oil flow contact FLP also causes opening of normally closed contact CR-3B to deenergize warning signal light 80 (FIG. 5). When warning signal light 80 is extinguished, it indicates to the operator that the low pressure oil flow condition is satisfactory or normal.

Before starting up the grinding mill, the low pressure lubrication system is always started up first as just described and is permitted to run for a predetermined time for oil heat-up at the discretion of the operator, such as 2 hours, for example, before starting up the high pressure lubrication system, and before starting up the mill.

Before mill start-up, it is necessary to pump up or float the trunnion in the stationary bearing structure, so that when the mill does start to rotate, the trunnion will already be floating" and there will be sufficient lubricant between the bearing surfaces to prevent any damage to the bearing. If only the low pressure lubrication system were employed at mill start-up, there would be sufficient time lag in the hydrodynamic feed of the lubricant between the bearing surfaces produced by rotation of the trunnion to possibly permit damage to the bearing surfaces. By using the high pressure lubrication system prior to mill start-up and for a short period (such as 5 to minutes) after mill start-up, a supply of lubricant is assured between the rotating trunnion and the stationary bearing without depending on the hydrodynamic lubricating action produced by rotation of the trunnion.

To start the operation of the high pressure lubrication pump system, which is usually done shortly before startup of the grinding mill, the high pressure start pushbutton S-HP is closed to momentarily close contact 84A. Momentary closure of contact 84A completes the energization circuit of relay coil M-lR to cause the closing of the contacts M1A in the energization circuit of high pressure pump motor M-l. The energization circuit of relay coil M-1R also includes contact 78B of pump system stop switch 78, contact 86A of high pressure pump system stop switch 86, contact TR2 of timing relay TR, normally open contact M-ZRB, and normally closed overload contact OL-l. Since all of the contacts just mentioned are closed at the moment that high pressure pump start pushbutton contact 84A is momentarily moved to closed position, relay coil M-IR is energized as just described and seals itselfin through contact M-IRA to complete a scalingin or holding circuit for relay coil M-IR. The sealing-in or holding circuit for relay coil M-IR also includes normally closed contact CR4A, controlled by relay CR-4. Contact CR-4A is in its normally closed position when the high pressure lubrication start button is moved to closed position before mill start-up since, as will be explained hereinafter, relay CR-4 can only be energized to open normally closed contact CR-4A by the closing of the mill stop pushbutton.

Since high pressure pump motor M-l is now operating due to the energization of relay coil M-lR and is driving high pressure pump 64 to pump high pressure oil through the high pressure lubrication circuit,

although the mill has not yet been started up in operation, the dual pressure switch 68 will be activated by the high pressure lubricant condition in high pressure line 42 to cause contact LHP indicating normal high pressure condition in the high pressure lubricant line to close. Also assuming that an excessive high pressure condition does not exist in high pressure line 42, the normally closed contact HHP will remain closed. Relay coil CR-l will be energized by the closure of pressure switch LHP and relay coil CR-Z will remain energized by the normally closed condition of pressure switch contact HHP. Energization of relay coil CR-l closes the normally open contact CR1A in the circuit of the mill motor starter; and similarly, the energization of relay coil CR-2 closes the normally open contact CR-ZA in the circuit ofthe mill motor starter (See FIG. 4). As previously explained, contact CR-3A controlled by relay CR-3 of the low pressure control circuit is already closed, and hence all three of the normally opened contacts CR-lA and CR-2A and CR-3A are now closed. Assuming that the corresponding contacts CR-lA, and CR-ZA', and CR-3A' at the bearing of the opposite end of the mill and which are respectively responsive to corresponding conditions as those which actuate contacts CR-lA, CR-2A, and CR3A, are similarly closed at this time, the mill motor can be energized by closure of a pushbutton switch in the mill motor starter circuit, as would be obvious to one skilled in the art, to start up the grinding mill motor (not shown).

From the foregoing it can be seen that an interlock circuit is provided which prevents starting up of the mill motor unless the relay CR-3, which is responsive to normal lubricant flow conditions in the low pressure lubricant flow circuit is energized, and also unless the relays CR] and CR-2, which are responsive to proper pressure conditions in the high pressure lubricant system, are energized. Furthermore, proper lubricant flow and pressure conditions must be in effect at both mill bearings before the mill motor starting circuit can be energized.

Energization of relay coils CR-] and CR2 will also cause the opening of the normally closed contacts CR-IB and CR-2B, respectively, in the energization circuit of warning signal lights 81 and 83, respectively, thereby indicating that the pressure conditions in the high pressure lubrication circuit are normal. It will also be noted in FIG. 5 that a normally open contact M2RC which is operated to closed position by energization of relay coil M-ZR of the low pressure pump motor circuit, is connected in series with the parallelconnected contacts CR-lB, CR2B, and CR-3B in the energization circuit of warning

lights

80, 81, 83. Thus, warning

lights

80, 81, 83 cannot be lighted at all unless low pressure pump M-2 is in operation.

With the high pressure and low pressure lubrication systems in operation as just described, and with the interlock contacts CR-lA, CR-ZA, CR-3A, etc. of FIG. 4 closed, the mill may now be started up by the following procedure: close the mill motor Start pushbutton which closes appropriate relay means (not shown) to energize the mill drive motor which will remain in operation until the mill motor Stop pushbutton is closed to cause interruption of the energization circuit of the mill motor. The mill motor Start pushbutton includes normally closed momentary contact MST1 in the circuit of relay coil CR4 and normally open momentary contact MST-2 in the circuit of timing relay TR as auxiliary contacts operated by the closure of the mill motor Start switch or pushbutton.

Movement of the mill motor start switch to closed position will momentarily open normally closed contact MST-l to deenergize relay operating coil CR4 if coil CR4 is not already deenergized at this time.

Deenergization of operating coil DR4 will open seal-in contact CR4B to maintain relay coil CR4 deenergized after momentary contact MST-1 recloses. Deenergization of relay coil CR4 will also close nor mally closed contact CR4A in the sealing-in circuit of relay MlR which controls the operation of high pressure lubrication pump motor Ml.

Closure of the mill motor start switch will also momentarily close normally open contact MST-2, which is one of the auxiliary contacts of the mill start switch, to energize timing relay TR. Timing relay TR operates two contacts; namely, a normally open contact TR-l in the sealing-in circuit of timing relay TR and a normally closed timed contact TR-2 in the energization circuit of relay coil MlR which controls the operation of high pressure lubrication pump motor M-l.

When timing relay TR is energized by the closure of contact MST-2, timing relay TR seals itself in through the series connection of normally open contact M-1R2 which is closed at this time since control relay MlR is energized at this moment, and also through normally open sealing in contact TR-l which has been moved to closed position by the energization of timing relay TR. Timing relay TR is so constructed that after a predetermined energizationinterval such as 15 minutes, for example, it will open timed contact TR-2 momentarily. This momentary opening of timed contact TR-2 will deenergize relay coil MlR and cause a dropping out of the sealing-in contact M-lRA which is operated by relay MlR. Even through timed contact TR-2 is reclosed a short interval after its opening by the deenergization of timing relay TR, reclosure of contact TR-2 will not reenergize the circuit of relay coil MlR which controls the high pressure lubrication pump since the sealing-in contact M-lRA will still be open, and there will thus be no energization circuit completed for relay coil MlR.

Timing relay TR may be of the type manufactured by Paragon Electric Company, Inc., 1600 Twelfth Street, Two Rivers, Wisconsin 54241, under the designation of Model 500-132-0, and described in 500 Series-Bulletin 426:5-70" of Paragon Electric Company, Inc. Paragon Electric Company, Inc., is a subsidiary of AME Incorporated, 261 Madison Avenue, New York, New York 10016.

As a result of the deenergization of relay coil MlR at the end of the period such as minutes timed by the timing relay TR, the high pressure lubrication pump motor M] will cease operation and the mill which is now in operation will continue operating but only with the low pressure lubrication pump motor M-2 in operation.

The deenergization of the relay MlR will also result in the opening of contact MlR-2 in the sealing-in circuit of the timing relay TR, thereby resulting in the deenergization of timing relay TR. Deenergization of timing relay TR will also result in the opening of the sealing-in contact TRl, restoring that contact to its normally open position. When relay TR becomes deenergized, he timing contact TR-2 in the circuit of relay coil MlR reverts to its normally closed position.

DESCRIPTION OF THE OPERATION OF THE CONTROL SYSTEM UPON SHUTDOWN OF THE GRINDING MILL Assume that it is desired to shut down the grinding mill. The mill motor stop pushbutton (not shown except for contacts in lubrication control circuits) is pushed causing the rotating mill drum 10 to come to a stop and also causing a momentary closing of the normally open auxiliary contacts MSP-l and MSP-2 which are carried by the mill motor stop pushbutton. Momentary contact MSP-l is in the circuit of relay coil CR4, and momentary contact MlSP-Z is in the circuit of relay coil M-2R which controls the operation of the low pressure lubrication pump motor M-2.

Momentary closure of mill stop pushbutton contact MSP-1 will energize relay coil CR4 which will close sealing-in contact CR4B to seal-in relay coil CR4 in a circuit which also includes high pressure lubrication pump motor stop pushbutton contact 86B and normally closed momentary contact MST-l of the mill motor start pushbutton, both of which are closed at this moment. Closure of auxiliary contact MSP-Z by the closure of the mill motor stop switch will energize relay coil M-ZR to thereby energize the low pressure lubrication pump motor M2 if that motor is not already energized at the time the mill motor stop switch is actuated to closed position. Relay coil M-ZR, when energized, will close the following contacts: (1) Normally open contact M2RA in the sealing-in circuit of relay M2R; (2) Normally open contact M-2RB in the circuit of relay MlR; and (3) Normally open contact MZRC in the circuit of the warning signal lights (FIG. 5).

Energization of control relay coil CR4 by the momentary closure of the mill motor stop switch auxiliary contact MSP-l as previously described will result in the opening of the normally closed contact CR4A in the sealing-in circuit of relay coil MlR which controls high pressure lubrication pump motor M-l, with the result that as long as relay coil CIR-4 is energized, the energization path of relay coil MlR from control power lines 101 to 102 must include contact Sl-l associated with timer TM-l.

Energization of relay coil CR4 will also close normally open contact CR-4C in the circuit of solenoid S-l associated with timer TM-l. Energization of solenoid S-l begins the timing operation of timer TM1. Solenoid 8-1 is also in series with normally closed contact L2-2 which is operated by timer TM-2. Energization of solenoid 8-1 will instantaneously close normally open contact Sl-l which completes a circuit from control power line 101 to control power line 102 through closed contacts TR-Z, M-ZRB, relay coil Ml-R and normally closed overload contact OL-1 to thereby energize relay coil MlR which will close contacts MlA in the energization circuit of the high pressure lubrication pump motor Ml to thereby start up and cause operation of the high pressure pump motor Ml. Starting up of the high pressure pump motor M-l will drive high pressure lubrication pump 64 to supply high ressure lubricant in hydrostatic lubricating relation to the free trunnion 16 to thereby float" the free trunnion while the mill is shut down, permitting the mill to contract as it cools off without metal-to-metal contact between the trunnion and the stationary bearing which supports the trunnion.

The control circuit of FIG. 3 includes timers TM-l and TM-2. Timer TM-Z includes as components thereof a timing motor T-l, a solenoid S-l, and contacts S11 and Ll-l. Timer Tm-2 includes as components thereof a timing motor T-2, a solenoid S2,

and contacts L2-2 and L4-2.

At the end of a predetermined time after the energization of solenoid S-l, such as two minutes, timer TM-l will momentarily close contact Ll-l to energize solenoid S-2 of timer TM-2 to begin the timing action of timer TM-2. Immediately upon the energization of solenoid S2 of timer TM-2, the solenoid S2 of timer TM-2 will 1) seal itself in by closure of sealing-in contact L4-2; and (2) will open normally closed contact 1.2-2 in the circuit of solenoid S-l of timer TM-l. Opening of contact L2-2 will deenergize solenoid S-1 and permit contact Sl-l in the circuit of relay coil M-lR to open, thereby deenergizing relay coil M-lR and causing high pressure lubrication pump motor M-l to stop running.

At the end of a predetermined time such as 30 minutes following the shutdown of high pressure lubrication pump motor M-l, timer TM-2 operates to (1) cause contact L2-2 in the circuit of solenoid 5-1 of timer TM-l to revert to its normally closed position to thereby reenergize solenoid S-l; and (2) to reopen sealing-in contact L4-2 to thereby deenergize solenoid S-2 of timer TM-2.

With solenoid S-l reenergized at the end of the predetermined time such as 30 minutes, contact Sl-l recloses and completes the circuit through relay coil M-lR to again energize high pressure lubrication pump motor M1 for the predetermined on" period such as 2 minutes, at the end of which on" period, timer TM l will again momentarily close contact Ll-l, in the circuit of solenoid S-2 will result in the reopening of contact L2-2 in the circuit of solenoid Sl to again result in the opening of the contact Sl-l to again deenergize solenoid M-lR which again results in the shutting down of high pressure pump motor M-l.

The ON-OFF" cycling of the high pressure pump at the free bearing during the cooling-off period after shutdown will provide a sufficiently thick film of oil during the on" period of the high pressure lubrication pump (such as 2 minutes) to provide a sufficient lubrication film at the interface between the trunnion l6 and the stationary bearing during the off period of the pump, for example, 30 minutes. The oil film at the interface is gradually squeezed out by the weight of the trunnion, but is replenished during the next on period of the high pressure lubrication pump before being diminished below a safe value. The relative lengths of the on and off times of the cycling operation can be so adjusted as to ensure that there is always a sufficient film of oil at the interface of the trunnion and the stationary bearing during the cooling off period of the grinding mill after shut-down.

Timers 'lM-l and TM-2 are commercially available and are manufactured by Paragon Electric Company, lnc., i600 Twelfth Street, Two Rivers, Wisconsin 54241, U.S.A., a subsidiary of AMF Incorporated, 261 Madison Avenue, New York, New York 10016. Timer TM1 is MOdel No. 500 and timer TM-2 is Model No. 50l, as described in Paragon Electric'Company Bulletin No. 42625-70, and in Paragon Electric Company Catalog No. 497212-70, Page 10.

The ON-OFF cycle of the high pressure lubrication pump motor M-l as controlled by timers TM] and TM-2, with a predetermined on time of motor M-l such as 2 minutes, and a predetermined of time of motor M-l such as 30 minutes, will continue indefinitely unless interrupted in one of the following ways:

1. By momentarily pushing high pressure lubricating pump stop pushbutton 86,

pushbutton contacts

86A and 86B are momentarily opened. The momentary opening of pushbutton contact 868 of pushbutton 86 deenergizes the circuit of relay coil CR4, opening up sealing-in contact CR4B of relay coil CR4, and also opening contact CR 4C in the circuit of solenoid S-l. Since solenoid S] is thus deenergized, contact Sl-l remains open and cannot be cycled alternately to closed and to open position by the action of timers TM-l and TM-2, as previously explained to energize relay coil M-lR and hence energize high pressure pump motor M-l. The momentary opening of contact 86A of high pressure pump stop pushbutton 86 also opens the circuit of relay coil M-lR to also cause a dropping out of sealing-in contact M-lRA. Thus, even though normally closed contact CR-4A recloses with the deenergization of relay CR4, the uncycled energization path of relay M-lR is open due to the opening of sealing-in contact M-lRA. Hence, both the uncycled path and the cycled path of energization of relay coil M-lR have been opened, resulting in deenergization of high pressure lubrication pump motor M-l.

It will be noted that there are two pump stop pushbuttons, namely pump stop pushbutton 78, which includes

contacts

78A and 78B, and pump stop pushbutton 86, which includes

contacts

86A and 86B. Actuation of pump stop pushbutton 78 to open contacts 78A and 788 causes both the high pressure pump motor M-1 and low pressure pump motor M-2 to stop. Actuation of pump stop pushbutton 86 to open contacts 86A and 868 causes only high pressure pump motor M--] to stop.

2. The ON-OFF cycling of high pressure lubrication pump motor M-l can also be terminated by pushing the mill motor start pushbutton to momentarily open normally closed auxiliary contact MST-l carried by the mill motor start pushbutton. Opening of contact MST-1 will deenergize relay coil CR-4 and open normally open contact CR-4C in the circuit of solenoid 5-1 of timer TM-l. Deenergization of solenoid S-l by the opening of contact CR-4C will cause cycling contact 51-1 in the energization circuit of relay coil M-lR to remain open, thereby preventing ON-OFF cycling as previously described. Also normally closed contact CR4A in the circuit of relay coil 'M-IR will close, permitting sealing-in of coil M-lR when it is energized. However, closure of the mill motor start pushbutton will initiate the energization of timing relay TR, as explained earlier in the specification, due to the momentary closing of contact MST-2 carried by the mill motor start pushbutton, and timing relay TR will cause high pressure pump motor M-l, if already in operation such that normally open contact M-IRZ is closed, to operate on an uncycled basis for a predetermined time such as minutes, after which it will interrupt the energization circuit of pump motor M-l. If the high pressure pump motor M-l is not operating with concurrent closure of contact M-lR2 in the circuit of timing relay TR when the mill motor start pushbutton is closed, the mill will not start because the pressure switch interlock contacts CRlA and CR-2A are not closed in the energization circuit of the mill drive motor.

The following is a recapitulation of the various relays in the lubrication control circuit at the free" bearing 1620 and of the contacts which they control:

1. Relay coil M-1R controls the following contacts:

a. Normally open contacts M1A in the circuit of high pressure pump motor M-l. Contacts M-1A are operated to closed position by the energization of relay coil M-1R and move to open position when relay coil M-lR is deenergized.

b. Normally open contacts M-lRA and M-1R2 are respectively moved to closed position by the energization of relay coil M-lR and move to open position when relay coil M1R is deenergized.

2. Relay Coil M-ZR controls the following contacts:

a. Normally open contacts M-2A of the low pressure pump motor M2 are operated to closed position by the energization of relay coil M-2R and move to open position when relay coil M-2R is deenergized.

b. Normally open contacts M-ZRA, M-2RB and M-2RC are respectively moved to closed position by the energization of relay coil M-ZR and respec tively move to open position upon the deenergization of relay coil M-2R.

3. Relay coil M3R controls normally open contacts M-3A in the circuit of heater 61. When relay coil M-3R is energized, contacts M-3A move to closed position, and when relay coil M-3R is deenergized, contacts M-3A move to open position.

4. Relay coil CR-l controls normally open contact CRlA (FIG. 4) and normally closed contact CR-lB (FIG. 5).

When relay coil CR-1 is energized, contact CR-lA closes and contact CR-IB opens, when relay coil CR-l is deenergized, contact CR-1A opens and contact CR- 1B closes.

5. Relay coil CR-2 controls normally open contact CRZA (FIG. 4) and normally closed contact CR2B (FIG. 5). When relay coil CR-2 is energized, contact CR-2A closes, and contact CR2B opens when relay coil CR-2 is deenergized, contact CR-ZA opens and contact CR2B closes.

6. Relay coil CR3 controls normally open contact CR3A (FIG. 4) and normally closed contact CR3B (FIG. 5). When relay coil CR3 is energized, contact CR3A closes and contact CR3B opens; when relay coil CR3 is deenergized, contact CR3A opens and contact CR3B closes.

7. Relay coil CR4 controls normally closed contact CR4A, and normally open contacts CR4B and CR4C. When relay coil (TR-4 is energized, normally closed contact CR-4A opens and normally open contacts CR-4B and CR-4C close; when relay coil CR-4 is deenergized, normally closed contact CR4A closes and normally open contacts CR-4B and CR-4C open.

From the foregoing detailed description of the present invention, it has been shown how the objects of the invention have been obtained in a preferred manner. However, modifications and equivalents of the disclosed concepts such as readily occur to those skilled in the art are intended to be included within the scope of this invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1; In combination, a rotary grinding mill mounted for rotation, means for rotating said :mill, a trunnion forming part of and rotatable with said grinding mill, stationary bearing means supporting said trunnion for rotation, a lubrication system including a high pressure pump, fluid conduit means connecting the output of said high pressure pump to the interface between said trunnion and said stationary bearing means for applying high pressure lubricant between said trunnion and said bearing means upon mill shutdown whereby to float said trunnion in said bearing means, an electric drive motor in driving relation to said high pressure pump, electrical control circuitry for said lubrication system, and control means forming a part of said electrical control circuitry and being actuated upon shutdown of said grinding mill to cause a cyclic ON-OFF operation of said electric drive motor and thus of said high pressure pump whereby to cyclically pump high pressure lubricant to the interface between said trunnion and said stationary bearing means, said control means including means for controlling said energization of the electric drive motor for said high pressure pump, said means for controlling said energization of said electric drive motor being connected to electric power prior to start-up of the grinding mill and for a predetermined time after start-up of the grinding mill in a normal circuit path, said control means comprising means actuated upon shutdown of the grinding mill for interrupting said normal circuit path and for connecting said means for controlling the energization of said electric drive motor to electrical power through an alternative circuit path and comprising timing means for cyclically and repetitively closing and then interrupting said alternative circuit path whereby to cause said cyclic ON-OFF operation of said high pressure pump.

2. The combination defined in claim 1 in which said lubrication system includes a low pressure pump for applying low pressure lubrication to said trunnion and to said bearing means.

3. The combination defined in claim 2 including conduit means connecting the output of said low pressure pump to the input of said high pressure pump whereby said high pressure pump derives its supply of lubricant from said low pressure pump, and means forming part of said electrical control circuitry for causing said low pressure pump to be in operation whenever said high pressure pump is in operation.

4. The combination defined in claim 1 in which said electrical control circuitry includes additional control means actuatable to stop the cyclic ON -OFF operation of said high pressure pump.

5. A lubrication system for a rotary grinding mill of the type having a trunnion forming a part of and rotatable with said grinding mill and a stationary bearing means supporting said trunnion for rotation, said lubrication system including a high pressure pump, fluid conduit means adapted to connect the output of said high pressure pump to the interface between said trunnion and said stationary bearing means for applying high pressure lubricant between said trunnion and said bearing means upon mill shutdown whereby to float said trunnion in said bearing means, an electric drive motor in driving relation to said high pressure pump, electrical control circuitry for said lubrication system, and control means forming a part of said electrical control circuitry and adapted to be actuated upon shutdown of said grinding mill to cause a cyclic ON-OFF operation of said electric drive motor and thus of said high pressure pump whereby to cause said high pressure pump to cyclically pump high pressure lubricant to the interface between said trunnion and said stationary bearing means, said control means including means for controlling the energization of said electric drive motor for said high pressure pump, said means for controlling the energization of said electric drive motor being adapted to be connected to electric power prior to start-up of the grinding mill and for a predetermined time after start-up of the grinding mill in a normal circuit path, said control means comprising means adapted to be actuated upon shutdown of the grinding mill for interrupting said normal circuit path and for connecting said means for controlling the energization of said electric drive motor to electrical power through an alternative circuit path and comprising timing means for cyclically and repetitively closing and then interrupting said alternative circuit path whereby to cause said cyclic ON-OFF operation of said high pressure pump.

6. A lubrication system as defined in claim 5 which includes a low pressure pump adapted to apply low pressure lubrication to said trunnion and to said bearing means.

7. A lubrication system as defined in claim 6 including conduit means connecting the output of said low pressure pump to the input of said high pressure pump whereby said high pressure pump derives its supply of lubricant from said low pressure pump, and means forming part of said electrical control circuitry for causing said low pressure pump to be in operation whenever said high pressure pump is in operation.

8. A lubrication system as defined in claim 5 in which said electrical control circuitry includes additional control means actuatable to stop the cyclic ON-OFF operation of said high pressure pump.

Claims

1. In combination, a rotary grinding mill mounted for rotation, means for rotating said mill, a trunnion forming part of and rotatable with said grinding mill, stationary bearing means supporting said trunnion for rotation, a lubrication system including a high pressure pump, fluid conduit means connecting the output of said high pressure pump to the interface between said trunnion and said stationary bearing means for applying high pressure lubricant between said trunnion and said bearing means upon mill shutdown whereby to ''''float'''' said trunnion in said bearing means, an electric drive motor in driving relation to said high pressure pump, electrical control circuitry for said lubrication system, and control means forming a part of said electrical control circuitry and being actuated upon shutdown of said grinding mill to cause a cyclic ON-OFF operation of said electric drive motor and thus of said high pressure pump whereby to cyclically pump high pressure lubRicant to the interface between said trunnion and said stationary bearing means, said control means including means for controlling said energization of the electric drive motor for said high pressure pump, said means for controlling the energization of said electric drive motor being connected to electric power prior to start-up of the grinding mill and for a predetermined time after start-up of the grinding mill in a normal circuit path, said control means comprising means actuated upon shutdown of the grinding mill for interrupting said normal circuit path and for connecting said means for controlling the energization of said electric drive motor to electrical power through an alternative circuit path and comprising timing means for cyclically and repetitively closing and then interrupting said alternative circuit path whereby to cause said cyclic ON-OFF operation of said high pressure pump.

4. The combination defined in claim 1 in which said electrical control circuitry includes additional control means actuatable to stop the cyclic ON-OFF operation of said high pressure pump.

5. A lubrication system for a rotary grinding mill of the type having a trunnion forming a part of and rotatable with said grinding mill and a stationary bearing means supporting said trunnion for rotation, said lubrication system including a high pressure pump, fluid conduit means adapted to connect the output of said high pressure pump to the interface between said trunnion and said stationary bearing means for applying high pressure lubricant between said trunnion and said bearing means upon mill shutdown whereby to ''''float'''' said trunnion in said bearing means, an electric drive motor in driving relation to said high pressure pump, electrical control circuitry for said lubrication system, and control means forming a part of said electrical control circuitry and adapted to be actuated upon shutdown of said grinding mill to cause a cyclic ON-OFF operation of said electric drive motor and thus of said high pressure pump whereby to cause said high pressure pump to cyclically pump high pressure lubricant to the interface between said trunnion and said stationary bearing means, said control means including means for controlling the energization of said electric drive motor for said high pressure pump, said means for controlling the energization of said electric drive motor being adapted to be connected to electric power prior to start-up of the grinding mill and for a predetermined time after start-up of the grinding mill in a normal circuit path, said control means comprising means adapted to be actuated upon shutdown of the grinding mill for interrupting said normal circuit path and for connecting said means for controlling the energization of said electric drive motor to electrical power through an alternative circuit path and comprising timing means for cyclically and repetitively closing and then interrupting said alternative circuit path whereby to cause said cyclic ON-OFF operation of said high pressure pump.