US2691278A - Cooling system for lubricating greases - Google Patents

Description

Oct. 12, 1954 A. a. KNIGHT, JR

COOLING SYSTEM FOR LUBRICATING GREASE-S 5 Sheets-Sheet 1 Filed March 23, 1950 lb Z Wdbboma Oct. 12, 1954 A. a. KNIGHT, JR 269L278 COOLING SYSTEM FOR LUBRICATING GREASES Filed March 23, 1950 5 Sheets-Sheet 2 5TEAM .1 FQE 243, i: KETTLE mania -iOQ lob 104 L05 Gilbert b.(nz5t,dn Unvenbor' Oct. 12, 1954 A. a. KNIGHT, JR 269L 3 COOLING SYSTEM FOR LUBRICATING GREASES Filed March 25, 1950 i 5 Sheets$heet 3- i l azz l l 1: 1 1 "250 i 124 "7-1 1.24 12w mm, 3 I I 1 I l l I I l I I 1' i I I i I: 241-" l 1 1 n ,1 .1 g 110 g g m 4 I @244 245-1 4h Y a l I 4 b ,Az %Wcmborne.g

Oct. 12, 1954 A. B. KNIGHT, JR

COOLING SYSTEM FOR LUBRICATING GREASES Filed March 23, 1950 5 Sheets-Sheet 4 204 z o 'ZO'Z 206 H 205 g 2M- ZOO i 212 FIrS .bg zg A 7%,, C Lbborrzeg Oct. 12, 1954 A. B. KNIGHT, JR 2691,278

COOLING SYSTEM FOR LUBRICATING GREASES Filed March 25, 1950 5 Sheets-She'et 5 FIG-Co i 145 {40 z l H; l 149-14'? 150 M25 125 S \fz4 12% FIG Patented Oct. 12, 1954 COOLING SYSTEM FOR LUBRICATING GREASES- Albert B. Knight, Jr., Mount Lebanon, Pittsburgh, Pa., assignor to Standard Oil Development Company, a corporation of Delaware Application March 23, 1950, Serial No. l51,450

The present invention relates to a cooling system for lubricating greases, and the like. The invention comprises a new type of apparatus suitable for the controlled cooling of lubricating greases and related compositions where it is desired to obtain a definite and controlled crystalline structure. The invention also involves process aspects, the control of the flow of a cooling fluid, such as air, over containers of the material to be cooled being an important aspect.

In the prior art, various attempts have been made to adopt more modern methods of preparing lubricating greases than the older conventional pan cooling processes which are still widely used. In recent years, a number of inventions have been patented relating to so-called continuous methods for lubricating grease manufacture. For some types of greases, these continuous methods have proved to be quite satisfactory where the nature of the product permits the type of cooling that can be accomplished in continuous processes. There are, however, certain greases which do not as yet lend themselves well to production by continuous methods. In some cases, the greases must be cooked for substantial periods of time in order to complete the desired chemical reactions or to fully evaporate water and other reaction byproducts which should be removed. In some of them, continuous cooling is not practicable because crystallization must not be allowed to proceed too rapidly because it results in a grease structure which is not suitable for the purposes intended. For these and other reasons, some of the more important types of lubricating greases, such as those of sodium base, are not generally adaptable to the continuous method of manufacture or even to the continuous cooling processes which have recently been adopted for some other types of lubricating greases.

In view of the difiiculties in applying continuous methods to some types of greases, it is still the practice commercially to prepare important classes of greases by the old conventional pan cooling processes. In such processes, as is well understood in the art, the grease ingredients are mixed and cooked in large kettles of appropriate design. After cooking has been completed, the hot grease is drawn, while still in a molten liquid or substantially liquid state, into relatively shallow pans which are allowed 'to set without being disturbed for a substantial period of time. The cooling of the grease in these pans proceeds at a more or less predeter- 6 Claims. (Cl. 62-114) mined rate that is appropriate for the particular crystalline or colloidal structure desired in the final composition.

Ordinarily, the conventional cooling pans are relatively shallow in depth although they are of substantial surface area. For example, typical installations may involve the use of several dozen or more cooling pans for cooling the quantity of grease which is cooked in a kettle in a single batch. These pans frequently are filled, for example, to a depth of 2 to 5 inches, a depth of about 4 inches being perhaps a fair general average, in some installations. When large batches of grease which may run, for example, from about 5,000 to 15,000 pounds or more, are to be cooled after cooking is completed, a very large number of pans must be filled and spread around on a floor or other support where they are left for a substantial period of time for cooling. The time required for cooling these pans of grease depends, of course, on ambient temperatures, on the depth of the layers, as well as upon the temperature of the grease when drawn from the kettle and the temperature to which it must be cooled before packaging or other processing. In varioues cases, the cooling time may vary from as little as l or 2 hours or less to as much as 24 hours or more.

In general, the purpose of cooling lubricating greases in relatively shallow pans is to obtain the smooth crystalline or colloidal grease structure which good lubrication demands. When large batches are cooled in the manner described above, there is so much heat involved that when a large number of pans are assembled, for example, spread out on the floor of a grease plant in the neighborhood of the cooking kettle, there is not obtained the desired uniformity in structure. Pans of grease near the edge of a large area cool more rapidly than those in the center of such an area. Moreover, when pans are placed on the floor, as they commonly are, there is no circulation of air under the pans and the bottom portion of the grease cools at a different rate than the top surface. Hence, even in individual pans the cooling is not as uniform as would be desirable.

It is also desirable, although difiicult to accomplish, to cool a grease composition rapidly at first, so as to save in total cooling time, but

it is also desirable that the cooling be carried tain transition stages Where crystal, structure changes rapidly. In some cases, it is desirable that this stage be prolonged or otherwise controlled. This cannot ordinarily be accomplished in conventional cooling pans when they are merely placed on a floor and allowed to set in the ambient atmosphere. Neither is it feasible, in the usual grease making plant, to introduce cooled or heated air at a controlled rate so as to maintain accurate control over cooling conditions.

Hence, a. major object of the present invention is to accomplish the uniform and controlled cooling of greases with a minimum of time consumption. It is also an object of the invention to provide for the efficient and economical handling and storage of a large number of grease cooling pans of conventional type where the kind of grease being manufactured requires cooling in such equipment.

It is a further object of the present invention to provide a more or less universal system which can be varied and adapted to various types of manufacturing operations and to the preparation of various kinds of lubricating greases without major changes in equipment or in methods of handling.

These and other objects will become more fully apparent as this specification proceeds. Accordingly, reference will next be made to the drawings forming apart of this specification in which Figure 1 is a diagrammatic view of the apparatus illustrating also the various steps which are involved in the present invention;

Figure 2 is a vertical elevational view with certain parts omitted of an apparatus made according to the invention;

Figure 3 is a longitudinal sectional view taken substantially on the line 33 of Figure 2, looking in the direction of the arrows;

Figure 4 is a sectional view of an apparatus substantially like that of Figure 2, showing certain modified features;

Figure 5 is a top plan view, with certain parts omitted, of part of the drive mechanism for the conveyors of Figures 2, 3 and 4, this view being taken substantially on the line 55 of Figure 3;

Figure 6 is a detailed view in elevation, with certain parts shown in section and other parts omitted, of a pan carrying tray which forms a part of the present invention;

Figure 7 is a front View in elevation of the tray device of Figure 6, portions of the chain conveyors which carry such tray being shown partly in section.

Referring first to Figure 1, there is shown schematically the outline of a grease making plant embodying the present invention. A cooking kettle I0 is mounted at a suitable height preferably somewhat above the main floor level so that a cooked batch of grease, or the like, may be withdrawn from the bottom thereof by gravity. As shown in Figure 1, this kettle is preferably supported by a second or mezzanine floor or platform, the arrangement being such that raw materials may be fed conveniently into the kettle from a point above the floor last mentioned. Such mezzanine or upper floor is indicated at l2.

The cooking kettle is provided with a suitable draw-off conduit [4 equipped with valve mechanism of appropriate type. This conduit i4 is preferably wrapped or jacketed with a suitable insulating material to prevent the congealing or hardening of lubricating grease therein which might interfere with subsequent operations. In some cases and in the preferred construction, this draw-off conduit may be steam jacketed so that it can be heated to melt any residual products that may remain therein from a previous operation.

Assuming that raw materials have been introduced into the cooking kettle 1G and have been suitably stirred and cooked for the desired period, a batch of the cooked lubricating grease is drawn out through the line 14 into a series of trays or pans 20. These pans may be supported upon suitable racks or open tray members 22, only two of which are shown in Figure l. The tray or rack members 22 are each attached, preferably by pivot means, to a pair of conveyor chains or belt 24, 26. Chains are preferably used, but for some installations belts of suitable weight and material may be employed.

In Figures 1 and '7 each tray is shown carrying two pans 20, but one large pan may replace the two. Appropriate retaining means are provided also to keep the pans in place on the trays as the latter pass through their circuit with the conveyors 24, 26. It will be understood that cooked lubricating greases may be drawn from the kettle at temperatures as high as 400 F. or more. For safety of the operators, the construction is such that any sliding or sloshing is prevented.

The number of trays or racks 22 which can be carried depends upon the length of the conveyors and also upon the spacing between adjacent racks or trays 22. Preferably, the tower structure is of considerable height, equivalent to several stories of a conventional building, so that a, rather large number of trays and cooling pans may be carried continuously. The size of these trays also can be varied to hold one, two, or more pans each.

The parallel conveyors 24 and 25 are carried and driven by suitable drums or sprockets not shown in Figure l but shown in the other figures of drawings to be described hereafter. Both conveyors and the entire series of trays and pans mounted thereon are substantially enclosed by a housing structure 30 which preferably extends around all four vertical sides of the conveyor system. Suitable openings are provided, of course, for introducing the filling nozzle M, which is appropriately joined or otherwise made flexible and also for inserting or withdrawing the empty or filled pans at other convenient points of the conveyor travel. Safety means, forming no part of the invention per se, but including electrically controlled mechanism for starting and stopping the conveyor drive, are provided so that movement of the conveyor can be stopped or started from any opening or control station. These means also prevent starting of the conveyor from one station when a door is open at another station.

It is commonly desirable, for example, to remove the pans of grease after they have passed substantially through one complete circuit of the conveyor system and to blend the cooled grease in a blending kettle with suitable modifiers such as extreme pressure additives, anti-oxidants, other types of greases, and the like. In Figure 1 there is shown a conveyor 35 on the opposite side of, the tower from the cooking kettle where the pans may be withdrawn and taken to a blending kettle 46. For convenience in other operations, the blending kettle, like the cooking kettle, is preferably mounted at a level substantially above the main floor. A roller conveyor, indicated fragmentarily at 4!, Figure 4, may be provided to carry away the pans and empty them into the blending kettle 40. The conveyor 4! may comprise an emptying attachment or movable section for tilting and emptying the trays automatically or semiautomatically. Another conveyor MA, Figure 4, may also be provided a the lowel level.

As shown in Figure 1, the blending kettle 40 may be mounted in the mezzanine or second floor or platform l2 by which it is supported in any appropriate manner. See also Figures 2 and 4. This kettle has an opening 42 at the top into which the pans of cooled or partially cooled grease may be emptied. The kettle may be provided with suitable mixing means and with suitable heating equipment. Ordinarily, one of thekettles, preferably the cooking kettle H3, is fireheated so that temperatures substantially higher than can be obtainable with steam jackets at available plant pressures may be obtained. It is desirable to have the other kettle, preferably the blending kettle 4U, suitably jacketed so that it can be heated with steam at least to moderate cooking temperatures without direct fire-heating. The arrangement is such, also, that cooling water or other fluid can be introduced into the jacket. From the blending kettle 40 a withdrawal line 44 is preferably provided.

The grease composition from the blending kettle ordinarily requires no further processing, unless homogenizing is desired, and may be fed directly into containers 5!! such as appropriate drums, cans, or the like. These containers may be passed along on a suitable conveyor 52 which is standard procedure in the prior art and need not be further described herein.

Alternatively, where it is not necessary to blend the grease after cooling, as in the production of block greases which are merely cut into slabs or blocks of appropriate size after cooling is substantially completed, the grease may be carried down to the main floor and. the pans removed through a suitable conveyor or other handling means 60.

Obviously, the operation of the whole system could be reversed, greases being preparedin the steam jacketed kettle 40, withdrawn into pans 20 on trays 22 for cooling.

As mentioned above, the entire assembly is preferably substantially surrounded by a housing 30 which is provided for the purpose of confining the cooling air or other cooling gases to a definite channel around the pans of hot grease. This housing or enclosure 38 is shown broken away in Figure 1 in order that the other elements might be pictured more clearly. In actual practice, however, it extends substantially from the top to the very bottom of the entire main conveyor system. Suitable air inlets may be provided at or near the bottom of the main vertical conveyor if incidental'openings are inadequate and appropriate air impelling means also are provided. The latter are usually needed not only to circulate cooling air around the grease pans but also to draw off vapors which are released as the pans are filled with hot grease. The natural draft of the hot vapors and heated air around the grease pans affords some circulation per se but supplementary draft means usually are needed.

For impelling the flow of cooling air and drawing off the vapors, it is generally preferred to use an exhaust fan of appropriate capacity in the ventilator mounted on top of a housing structure 12 which surrounds the operating mechanism for the upper end of the main or vertical conveyor. Obviously, when the exhaust fan is operated, a stream of air is drawn upwardly along the path of the conveyor and around the trays and grease pans, resulting in the cooling of the grease. The removal of the fumes in itself is no small improvement in a practical sense since the older pan cooling processes passed much of the vapors into the plant from the steaming freshly drawn pans.

Inasmuch as the incoming air as drawn by the fan mechanism is at its coolest when it contacts the lowermost grease pans on the rising side of the elevator, the coolest air contacts the hottest grease pans. As the air rises in its path, being impelled at a higher velocity than the movement of the conveyor, it overtakes other trays and pans but the temperature-difference between the air and the grease in the pan contacted thereby becomes progressively smaller. Hence, the air is heated as it rises and the grease is cooled as it rises but the cooling rate as the pans of grease approach the top of the tower becomes substantially reduced. On the other hand, as the pans begin to descend down the other side of the conveyor system they meet progressively with cooler and cooler air, the temperature differential being progressively increased. By suitable timing, or by suitable Variation in relative conveyor speed and air velocity, the critical transition stage of cooling may be placed where the air is of appropriate temperature to give the correct cooling rate. Moreover, since each pan goes through exactly the same cycle, all pans are cooled exactly alike. This improves uniformity over the prior art conventional pan cooling arrangements. The temperature and/or humidity of the air which is drawn into the tower may be controlled if desired.

A further feature of the present invention resides in the particular construction of the pan supporting trays by means of which the cooling air has ready access to the bottoms of the grease pans. Hence, the grease in a given pan can be cooled more rapidly and more uniformly in this system than in prior art systems where the bottom of the pan was usually relatively insulated in effect by being placed directly upon a flat solid surface of low heat conductance such as a floor.

The foregoing description covers the general apparatus and its method of operation. Referring now to Figure 2, there is shown in somewhat greater detail a tower structure mu consisting of appropriate structural members not shown in detail but 0f adequate strength and appropriate design to support the conveyor system, the power operating equipment above the conveyor system and the exhaust ventilator mechanism above the power house. The power house 12 is of conventional design as is also the ventilator system 10.

The tower I00 is supported on an appropriate foundation Hi2 which may be placed at a level somewhat below that of the main floor I04. A second fioor I2, as in Figure 1, is suitably sup-. ported by appropriate walls or other structural member I06 with supplementary footings or foundation elements I08 where these are needed. As previously described, a fire-heated kettle I 0 and a steam kettle 40 may be mounted in the second or mezzanine floor I2 so that their contents may conveniently be withdrawn at or above the first or main floor level.

The tower I00 may project beyond the third floor or the roof, as the case may be, of the factory building or other plant structure depending upon the height and type of the building in which 7. it is installed. In Figure 2 there is indicated a roof structure I I which is suitably supported on wall or column elements II 2 which in turn are suitably supported on the upper or mezzanine floor or on other and generally equivalent appropriate sup-porting structure.

The tower proper is completely surrounded, except for appropriate openings hereafter described, by a relatively airtight wall structure I30. This corresponds to the enclosure 30 of Figure 1.

Inside the tower there is provided an upper horizontal shaft I'I4 which carries a series of sprockets HE. A horizontal shaft or a group of stub shafts, whichever may be preferred, is mounted at the bottom of the conveyor and indicated generally at H8. On this there are provided suitable idler sprockets I I9.

Referring now to Figure 3, it will be seen that a pair of conveyor chains I24 and I26 are arranged in parallel relation to pass around the upper sprockets H6 and the lower sprockets II 9. It has been found advantageous under some circumstances to mount duplicate units in a single tower and therefore a second pair of conveyors I24A and IZSA are shown in Figure 3. The number of units in one tower can be varied, of course, to suit specific plant requirements. These additional conveyors, where used, pass around upper sprockets IIBA and around lower sprockets II9A in the same manner as the conveyors first described. Since their manner of operation, however, is exactly the same, the description will be confined, in general, to the single pair of conveyors I24 and I25.

Between the conveyors I24 and I26 there are pivotally mounted, each in a suspended position, a series of tray members which are shown in Fig ures 6 and 7. Thus, in Figure 7 the chain conveyors I24 and I26 are shown in one modification in some detail. At spaced intervals a few links apart, for example, about every 6 or 8 links in one typical installation, the number and distance depending, of course, upon the chain structure and other requirements, the conventional link pin I25 is replaced with a shaft I M which extends the full distance between the parallel conveyor chains I24, I25. This shaft I4I supports an anti-friction bearing I42 at each end, these being shown in detail in the upper left hand and right hand parts of Figure 7.

Each of the tray members 22 comprises an end bracket I40 of generally triangular shape which has at its upper apex a boss member I43 which surrounds the bearing I42. Each end member also comprises a flange I44 which stiffens the end member and also rests upon and reenforces the boss I43. The end member comprises a web portion I45 and a reenforcing rib I 46' extending between the web member I45 and the boss I 43. At its lower edge, the web member I45 is secured to an angle bar I41 and each of the angle bars I4! is provided with a series of bearing apertures I48 to receive the reduced end or spindle portions 39 of series of rollers I50.

The two end members are connected not only by the shaft Mi but also by a connecting member II which extends from one web I45 to the other.

An angle bar I52 is also provided across each lower edge of the assembly, serving further to connect the end members and unite the whole tray assembly. The members I41 and I52 are attached to the webbed and flanged end pieces I49, etc. by appropriate fastening means such as bolts or rivets, or the parts may be welded together. Preferably, however, the assembly is made so that the rollers I59 can be removed or replaced conveniently should that be necessary.

Each of the sloping flange elements I44 of end members I46 is also provided with an upstanding ear portion I55 which supports a transverse tube or shaft member I 56 for limited rotary movement. On each end this shaft member has a plate I51 afiixed and the plate is so shaped that it has two stop surfaces I58 and I59 adapted to abut against the foot of the ear member shown at I60. Intermediate their ends at a point approximately at the middle of each of the pan positions, each of the shafts I55 carries two latch members IBI. Where a single pan is carried, of course only one member IBI need be provided, although two or more may be used. Each latch member has a stop element I62 directed substantially vertically downward and a sloping lifting plate IE3 is afiixed to the end of the latch bar ISI and the stop member I52 by appropriate means such as riveting or welding.

By reason of the construction just described, a grease pan can be slid onto the tray without interference by the latch member which merely lifts up under the force of the pan, but when the pan is pushed fully onto the tray the latch member I82 will prevent its lateral displacement off the tray until the latch is lifted. As a pan is slid toward the tray, from the right of Figure 6, for example, its edge will strike the sloping under surface of the lifter I63 which will rise freely and the pan can be pushed on to the tray, riding freely on the rollers I58. When pushed fully on to the tray, the pan will contact the stop member I62 on the opposite side of the tray and the raised latch will then drop to the position shown in Figure 6 to prevent return movement. It will be noted that pans may be placed on or removed from any tray from either front or back.

The stop surfaces I58, I59 and IE0 limit rotation of the latch arms IGI in either direction so that the latches are always in position for operation. If desired, the connecting bar or tube I56 may be made hollow (and in two aligned sections) and supported upon a rod or equivalent structure obvious to those skilled in the art so that either half can be rotated without affecting the other. It is sometimes desirable, as indi cated above, to make the tray sufiiciently large to accommodate two or even more grease pans simultaneously. This depends, of course, upon the size of pans. Where large pans are used, it may be preferable to carry only one pan p'er tray. In the case where two pans are carried, it may be desirable to have independent latches so that one pan remains latched on the tray while the other is being removed. However, the construction and arrangement of the trays preferably is such that there is no particular reason for latching one tray while the other is removed. The trays are guided in their travel so that they cannot tilt. Guide means I'Iil, in the form of vertical rails which hold the trays against lateral movement are provided along the conveyor for preventing the tilting of the trays due to' unbalanced forces such as an eccentrically disposed pan of grease. See especially Figure 6 which shows these rails fragmentarily'. They are omitted from the smaller scale figures but their construction is believed to be obvious. They extend along the path of travel beside tray members 22 to prevent tilting particularly at loading and unloading stations and preferably they extend along the entire path of travel.

Referring now to Figure 5, there is shown an appropriate drive mechanism for operating the main vertical conveyor system. The drive consists appropriately of a motor 200 with an appropriate brake mechanism 202, the motor being supported on a suitable base 204. The brake mechanism is designed to lock the conveyor against inadvertent movement due to gravity or otherwise when the motor is stopped. It is preferably of an automatic or self-setting type. The motor 200 drives a gear reducing mechanism 206 through its shaft 208 and a coupling member 2 I 0. The gear reducing mechanism comprises a heavy pinion 2 I 2 which drives a main gear 2 I lmounted on the shaft II4 previously referred to.

The large gear 2I4 is keyed to the shaft H4 along with the sprockets H6 and the whole assembly of sprockets, gear and shaft is appropriately supported in suitable bearing elements 220.

Referring now to Figure 4, there is shown a modification wherein other parts are substantially unchanged but a center partition is provided to confine the cooling air to the ascending or descending column of the conveyor without giving it access necessarily to both. This is accomplished by providing the partition member 230 which substantially separates the ascending elements from the descending elements. Figure 4 shows further modifications wherein an opening 232 is provided in the housing near the top thereof. With this arrangement, air may be introduced near the top of the conveyor or grease may be removed at that point. Such an operation is not usual but might be desirable in some arrangements.

Both the apparatus of Figure 2 and that of Figure 4 are preferably provided with openings and closures on both sides at the second fioor level and also at the first or main fioor level. These are indicated at 2M, 242, 243, and 244 in both figures. In usual operation, all of these would be closed except where pans are being filled or being unloaded, or the like. For safety of operation, as suggested above, suitable controls are provided to stop the conveyor when more than one of the closures MI, 242, 243, 244 or 232 is open. A full control system for stopping and starting the main conveyor from any station usually and preferably is combined with the safety means, as previously suggested.

The reason for this safety mechanism is to provide flexibility of control but also to give protection for any operator or attendant who may be inspecting, repairing or conducting some other operation at any open station. The conveyor cannot be started by an operator at another station until one or the other has completed his work and closed the opening whereby control of the conveyor is turned over to the other operator. The specific means, such as electrical wiring systems, may be varied and they form. no part of the present invention, but the control and safety feature, as a general adjunct, is of practical importance in the operation and structure of the invention.

What is claimed is:

1. In apparatus of the character described, the combination which comprises a tall tower, a pair of parallel endless conveyors mounted in said tower and extending substantially through the full height thereof, said tower comprising wall structure substantially enclosing said conveyor throughout its full length and having access doors on opposite sides near the bottom thereof, a series of open tray members pivotally attached to and suspended between said conveyors for supporting paths of material to be cooled, cooperating guide means on said tray members and said wall structure for maintaining said tray members in substantially horizontal position during ascent and descent in said tower and means for impelling a stream of cooling air upwardly from the lower to the upper portion of said tower around and past each of said trays and each of said pans to cool said material substantially uniformly and at a control ed rate, said enclosed tower substantially confining the stream of air to travel along the conveyor path, a pan loading station near the bottom of the tower on one side and a pan unloading station near the tower bottom on the opposite side.

2. In apparatus of the character described, the combination of a tall enclosed tower, a pair of parallel endless conveyors extending substantially from top to bottom of said tower, a series of tray members pivotally suspended between said conveyors, cooperating guide means on said tray members and inside said tower for preventing tilting of said tray members during their travel past loading stations, a loading station on each of two opposed sides of said tower near the bottom thereof, releasable latch means on each tray member for holding shallow pans in position on said tray members, and air impelling means for passing and confining a stream of air along the path of said conveyor along at least the ascending run thereof.

3. Combination according to claim 1 wherein the air impelling means comprises a ventilator fan at the top of the tower for drawing air upwardly through said tower.

4. Combination according to claim 2 wherein each tray member has front and back latch members to permit loading of pans from either side.

5. The process which comprises pouring molten lubricating grease, at a temperature in excess of 300 E, into one of a series of shallow pans, ad-

vancing said pan a short distance, filling the next pan, repeating this operation while a long series of pans are filled, continuously passing a stream of cooling gas through a conduit substantially enclosing said series of pans, so that said gas stream first contacts the pan poured most recently and containing the hottest grease, said gas stream thereafter contacting cooler and cooler pans in its passage while its own temperature increases so that the gas at its warmest point is passed around and over the pan farthest advanced in the series, and thereafter reversing the direction of advance of said pans so that each pan encounters successively a cooler and cooler portion of said gas stream, whereby the cooling rate first becomes progressively slower and later becomes progressively faster so that crystallization of the grease is uniformly controlled.

6. In apparatus of the character described, the combination which comprises a tall tower, a pair of parallel endless conveyors mounted in said tower and extending substantially through the full height thereof, said tower comprising wall structure substantially enclosing said conveyor throughout its full length and having access doors on opposite sides near the bottom thereof, a series of open tray members pivotally attached to and suspended between said conveyors for supporting pans of material to be cooled, cooperating guide means on said tray members and said wall structure for maintaining said tray members in substantially horizontal position during ascent and descent in said tower, a series of spaced rollers on each of said tray members, said rollers forming the pan supporting bottom of said tray members to facilitate loading and unloading said pans and to afiord access of cooling air to the bottom of said pans, and means for impelling a stream of cooling air around and past each of said trays and each of said pans to cool said material substantially uniformly and at a controlled rate, said enclosed tower substantially confining the stream of air to travel along the conveyor path.

References Cited in the file of this patent UNITED STATES PATENTS Number Number Number Name Date Kind Dec. 3, 1912 Spring June 10, 1913 Gill Aug. 3, 1920 Allsop et al. Apr. 12, 1921 Harris Apr. 24, 1928 Baker May 12, 1931 Cross Oct. 23, 1945 Patterson Feb. 3, 1948 Houlton Sept. 27, 1949 FOREIGN PATENTS Country Date Great Britain July 3 1902

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