US3633664A

US3633664A - Vertically oriented swept surface heat exchanger

Info

Publication number: US3633664A
Application number: US784978A
Authority: US
Inventors: John C Walsh; James A D Orsay
Original assignee: Contherm Corp
Current assignee: Alfa Laval Inc; Contherm Corp
Priority date: 1968-11-08
Filing date: 1968-11-08
Publication date: 1972-01-11
Anticipated expiration: 1989-01-11

Abstract

Many products and other materials may be continuously processed by the vertically oriented swept surface heat exchanger described herein. The vertically oriented cylinder in which the processing takes place has an upper head assembly including a power drive and a lower head assembly containing a bearing in one embodiment and including a pump integral therewith in a second embodiment. A pump is included with the lower head assembly, for the preparation of ice cream or other aerated comestibles. A rotor extends the length of the unit and includes a drive shaft extending through an upper end plate to engage the power drive. This rotor supports wiping blades which sweep the inner surface of the cylinder. The wiping blades may include nozzles along the length thereof and are affixed to the end of blade pins which extend radially from the rotor. When removing or replacing a rotor in the heat exchange cylinder, the rotor is supported and moved vertically by a releasable latch mechanism until a hydraulic elevator integral with the heat exchanger is moved into place.

Description

United States Patent [72] Inventors John C. Walsh Winchester; James A. DOrsay, Newburyport, both of Mass. [21 Appl. No. 784,978 [22] Filed Nov. 8, 1968 [45] Patented Jan. 11, 1972 [73] Assignee Contherm Corporation Newburyport, Mass.

[54] VERTICALLY ORIENTED SWEPT SURFACE HEAT EXCHANGER 5 Claims, 13 Drawing Figs.

[52] US. Cl 165/94, 277/99, 259/108, 62/354, 62/303 [51] Int. Cl F281 7/00 [50] Field ofSearch 165/94, 87, 74', 259/108, 45, 51; 103/126; 62/303, 22 5 354, 353; 277/99 [56] References Cited UNITED STATES PATENTS 2,064,597 12/1936 Engelmann 62/354 X 2,159,463 5/1939 Voorheis 165/94 2,440,397 4/1948 Erickson 62/303 X 3,029,613 4/1962 Lande 62/303 892,424 7/1908 Holden... 165/94 3,020,025 2/1962 OMara 165/87 3,446,318 9/1967 Duckett.... 277/99 X 2,357,640 9/1944 Ebbenbach... 259/108 X 2,619,040 11/1952 Maisch..... 103/126 3,077,840 2/1963 Wood 103/126 3,279,893 l0/l966 Kikorski 259/108 3,354,136 ll/l967 Crawford 165/94 X Primary Examiner Frederick L. Matteson Assistant Examiner-Theophil W. Streule Attorney-Richards, Harris & Hubbard ABSTRACT: Many products and other materials may be continuously processed by the vertically oriented swept surface heat exchanger described herein. The vertically oriented cylinder in which the processing takes place has an upper head assembly including a power drive and a lower head assembly containing a bearing in one embodiment and including a pump integral therewith in a second embodiment. A pump is included with the lower head assembly, for the preparation of ice cream or other aerated comestibles. A rotor extends the length of the unit and includes a drive shaft extending through an upper end plate to engage the power drive. This rotor supports wiping blades which sweep the inner surface of the cylinder. The wiping blades may include nozzles along the length thereof and are affixed to the end of blade pins which extend radially from the rotor. When removing or replacing a rotor in the heat exchange cylinder, the rotor is supported and moved vertically by a releasable latch mechanism until a hydraulic elevator integral with the heat exchanger is moved into place.

PATENIED Juli 1 I972 3.633.664 SHEET 1 0F 5 FIG. 4

I'NVENTORS:

JOHN c. WALSH JAMES A. D'OIRSAY ATTORNEYS PATENTED JAHI 1 I972 &.

SHEET 2 UF 5 vLEW illl JOHN C. WALSH I17 JAMES A. D'ORSAY ATTORNEYS PATENIEU JAM 1 B72 SHEET 3 [IF 5 INVENTORS:

JOHN c. WALSH JAMES A. D'ORSAY FIG. 7

ATTORNEYS FIG.5

Pmmmmnm V $633664 SHEET 4 UFS FIG.8

INVENTORS:

JOHN C. WALSH ATTORNEYS JAMES A. D'ORSAY PATENTED JAN 1 I972 SHEET 5 BF 5 I l l I I l2 "I95 I3! 3 J 2 26 /I34\ Q .L .L -I53 I260 I l68b FIG. 'II

mvemoas;

JOHN C. WALSH JAMES A. D'ORSAY ATTORNEYS VERTICALLY ORIENTED SWEPT SURFACE HEAT EXCHANGlER BACKGROUND OF THE INVENTION This invention relates to heat exchangers, and more particularly to vertical oriented swept surface heat exchangers for online operation.

In the processing of many products, either heating or cooling steps are essential. Presently, there exists a wide variety of types of heat exchangers for processing a variety of products whether it be by a process employing either heating or cooling. The majority of presently available heat exchangers are useful only in batch type processing, such processes being the principal way in which products have been prepared for a number of years. Recently, considerable effort has been directed to replacing the batch type operation with continuous processes in which the product is continuously fed into the system and discharged therefrom in a steady stream. Online heat exchangers (continuous processes) are capable of producing a product of at least equal quality, but at greatly increased production rates and under close control.

Heat exchangers that have been developed for continuous processes are usually of the swept surface type. This is desirable and sometimes necessary in order to maintain a product having uniform properties, and also to control the characteristics of the product. Basically, a swept surface heat exchanger includes a cylinder with a central rotor assembly mounted therein which mixes the product continuously as it flows through the unit. The product cylinder is generally surrounded by an annular heat exchange space through which a heat exchange medium passes, the product being heated or cooled by contact with the cylinder walls, against which the wiping blades continuously scrape. This basic type of heat exchanger has been used in the preparation of a wide variety of products, including the manufacture ofice cream.

The majority of swept surface heat exchangers have been oriented with the product cylinder axis generally horizontal. There are a number of shortcomings to the horizontally oriented heat exchanger. In all food processing, cleanliness is of prime importance and frequent cleaning is required by federal and state laws. In the cleaning process, the rotors are removed and cleaned separately from the heat exchange cylinder. Often, in removing or inserting a rotor assembly into a horizontally oriented cylinder, the rotor and/or the cylinder are damaged. Primarily, this is because the rotor assembly is relatively heavy, and since some exchangers are 6 to 8 feet long, the rotor becomes extremely difficult to handle.

In accordance with many standard cleaning procedures, a strong solution is used to clean both the product cylinder and the rotor. With the horizontally oriented exchanger, it is virtually impossible to remove all of the solution, even though the product cylinder is flushed thoroughly with water. As a result, the low point of the cylinder will corrode over a period of time, thus requiring replacement. Moreover, with a horizontally oriented heat exchanger, it is sometimes difficult to remove all of the processed food at the end of the run, and some of the product will be wasted.

When manufacturing ice cream in a swept surface heat exchanger, it is a common practice to employ a metering pump to mix the ice cream formula with a proportionate amount of air prior to chilling. The problem of making special pumps to meter an ice cream mix and air has been a major one for manufacture of continuous freezing systems. Because of the high pressures at which these pumps operate and the mixing accuracy required, the pump must be a precise machine with close tolerances.

Such pumps must be cleaned daily with an accepted cleaning procedure set by rule of local and federal health authorities. The procedure commonly employs hot water up to 180 F. and the normal expansion and contraction of the pump material designed to be used at 30 F. renders most pumps available today unusable through both cycles. Where a pump will not operate through both the low and high temperature cycles, it must be disassembled, the gears removed, and many of the metering parts removed and washed separately. The pumps are then reassembled without the gears and the cleaning material pumped through the system from an exterior source. Removal and separate washing is time and labor consuming and again, is a source of damage to the parts. In addition, it is far less sanitary than a clean-in-place procedure. Removing the parts for cleaning also prohibits the automation of the cleaning procedure whereby the process can be put on an automatic cycle.

Many food processors use the same heat exhanger for processing several different kinds or flavors of food products. For example, a heat exchanger for cooking soup may be used for tomato soup oneday and a noodle soup the next. In the manufacture of ice cream, the same heat exchanger may be used one day for manufacturing chocolate ice cream and the next for manufacturing strawberry ice cream. It is important that the blade configuration of this dual usage heat exchanger provide no open edges or holes to catch long fiber materials such as coconut, beef tissue, fruit pieces, noodles, et cetera, that may cause the machine to be disassembled between product changes to eliminate the possibility'of a noodle in tomato soup or a strawberry in chocolate ice cream. Many wiping blades in use today are mounted on supporting pins by means of elongated slots. These slots are prime areas for catching the fibrous materials.

It has been realized for some time, that when handling materials for high viscosity in a swept surface heat exchanger a cavity develops behind the wiping blade as a result of the blade action. This causes a loss of heat exchange surface and consequently an increase in processing costs. It has been common practice, though the reason has not been well understood, to pressurize the heat exchange cylinder through a holdback valve at the cylinder discharge pipe. Such a hold back pressure will tend to reduce the cavitation volume by forcing the material behind the wiping blade. This invariably causes a greater pressure differential across the blade than would normally be developed and increases the torque or horsepower input to the unit. In addition, this increased pressure differential causes accelerated wear to the wiping blades and product cylinder.

An object of the present invention is to provide a vertical swept surface heat exchanger. Another object of this invention is to provide a vertical swept surface heat exchanger that may be easily cleaned in accordance with local and federal procedures. Still another object of this invention is to provide a vertical swept surface heat exchanger wherein cylinder corrosion due to a cleaning solution residue is minimized. A further object of this invention is to provide a vertical swept surface heat exchanger having integral therewith a clean-inplace pump. Yet another object of this invention is to provide a vertical swept surface heat exchanger of a self-draining construction, thereby minimizing product waste. Still another object of this invention is to provide a vertical swept surface heat exchanger that may be easily flushed free of all product residue. An additional object of this invention is to provide a vertical swept surface heat exchanger having a minimum of heat exchange surface loss due to wiper blade cavitation. Still another object of the present invention is to provide a vertical swept surface heat exhanger having a rotor shaft free from bending or deflection from gravitational forces. A still further object of the present invention is to providea self-venting vertical swept surface heat exchanger. Yet another object of this invention is to provide rapid heating or cooling of a vertical swept surface heat exchanger to prevent rotor freezeup.

In accordance with a specific embodiment of this invention,

a heat exchange cylinder is vertically oriented with the rotor' supported from above and held in place during assembly and removal thereof by a convenient hoist mechanism. The vertically oriented cylinder is supported by mountings which also serve as the inlet and outlet for a cooling or heating medium. Such a mounting assembly permits the entire heat exchanger to be quickly and easily removed and replaced by a standby" or loaner" unit during repair. An elevator mechanism simplifies the raising or lowering of the rotor into or out of the cylinder. Whenassembled in the heat exchange cylinder, the rotor is positioned by 'upper and lower end plates and driven from an external power source. A series of blade pins extend radially from the rotor and support wiping blades covering substantially the length of the product cylinder in a manner to insure a sweeping action of the inner surface of the cylinder. Upper and lower seals in retaining rings are spring loaded to rotate with the rotor and seal the openings for the rotor shaft in the upper and lower end plates.

In another embodiment of the invention, a vertically oriented heat exchange cylinder has a rotor supported therein by upper and lower end plates. A metering pump constructed integral with the lower end plates includes meshed gears having hard facing wearing surfaces mating with heard facing wearing surfaces of the pump housing. The rotor moves between two positions; it initially assumes a venting position when the product cylinder is being filled to provide a vent to the atmosphere for air or other fluids. After the cylinder has been completely filled, pressure exerted on the rotor produces a force to lift the rotor and close the vent and seal the cylinder during operation thereof.

A more complete understanding of the invention and its advantages will be apparent from the specification and claims and from the accompanying drawings illustrative of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a vertically mounted swept surface heat exchanger in accordance with the present invention;

FIG. 2 is a sectional view of FIG. 1 illustrating in detail the heat exchanger mountings, a rotor elevator, and a fast heat spiral tube;

FIG. 3 illustrates in detail a spring-loaded shaft seal for the heat exchanger of FIG. 1;

FIG. 4 is a cross section illustrating a coupling between a power source and the heat exchanger rotor assembly;

FIG. 5 is a plan view of wiping blade for minimizing heating surface loss;

FIG. 6 is a cross section of the blade of FIG. 5 in an operating relationship with the product cylinder;

FIG. 7 is a cross section of a wiping blade supported on a blade pin;

FIG. 8 is a cross section of an alternate embodiment of a heat exchanger in accordance with this invention including a metering pump integral with the lower end plate;

FIG. 9 is a bottom view of the heat exchanger of FIG. 8;

FIG. 10 is a plan view of the metering pump of FIG. 8 removed from the lower end plate;

FIG. 11 is a cross section illustrating a releasable latch mechanism for holding the rotor of the unit of FIG. 8 during assembly and removal thereof into the product cylinder;

FIG. 12 is a cross section of the drive coupling illustrating the releasable latch mechanism taken along the line 12-12 of FIG. 11; and

FIG. 13 is a cross section showing a venting-sealing mechanism for the unit of FIG. 8.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the drawings, there is shown a heat exchanger constructed in accordance with the principles of the present invention mounted on suitable supporting structure 10 which may be a wall in a processing plant, a panel, a portable stand, or other supporting means. Preferably, the supporting structure 10 is provided with an upper fitting l2 and a lower fitting 14 both rigidly secured to the supporting structure. Each of the

fittings

12 and 14 is preferably a hollow tube having a flange of a well-known design such as

flanges

16 and 18 shown for the upper and

lower fittings

12 and 14, respectively.

Such flanges

16 and 18 are easily connectable to a mating flange and are held in an assembled condition by means of a clamping assembly. Thus, the upper flange 16 is held assembled to a mating flange 20 by means of a clamping assembly 22 while the lower flange 18 is secured to its respective flange 24 by a clamping assembly 26. Depending upon the nature of the product being processed, these supporting tittingsserve a dual purpose, as will be more fully described hereinafter.

The

flanges

20 and 24 are secured to the ends of

tubular conduits

28 and 30, respectively, which are in turn affixed to the outer jacket 32 of the heat exchanger. The outer jacket 32 serves as a supporting structure for the next exchanger and also as an enclosure for the operative components. Preferably, the outer jacket 32 is a stainless steel cylinder, thus giving the heat exchanger an attractive appearance and assuring compliance with the sanitary standards in the food and diary industry.

As illustrated in FIG. 2, mounted within the outer jacket 32 is an outer cylinder 34 and an inner cylinder 36 positioned concentrically with the outer cylinder. An annular space 38 is therefore formed between the outer cylinder 34 and the inner cylinder 36 within which space a continuous tubing 40 may be helically wound from the upper to the lower end thereof. This tubing 40 engages the outer surface of the inner cylinder 36 and the inner surface of the outer cylinder 34 and thus provides a helical flow path within the annular space 38 through which a heat exchange medium may flow. The tubing 40 may be connected to a source of gas or fluid by means of the connections 40a and 40b. Should an emergency condition arise when the annular space 38 is filled with a cooling medium, the hot gas or fluid will be introduced into the tubing 40 to raise the temperature of the heat exchange medium so that the inner surface of the cylinder 36 may be brought to approximately the temperature of the product. If the product is being heated, a fluid may be passed through the tubing 40 to reduce the temperature of the heat exchange surface to approximately that of the product. This eliminates the'possibility of the rotor assembly freezing to the inner cylinder 36 and maintains the unit ready for resumption of normal operation. The tubing 40 is particularly intended for a heat exchange system wherein care must be taken to prevent the annular space 38 from being contaminated by oil as from a compressor.

The heat exchange medium is introduced into the annular space 38 through a conduit 41 coupling the outer cylinder 34 to the conduit 30, and is discharged therefrom through a conduit 42 between the outer cylinder and the conduit 28. The conduits 41 and 42, as illustrated at the upper conduit 42, comprise a first pipe section 43 connected to the outer cylinder 34 and a second pipe section 45 secured to a conduit 48 which is held in place by a lock nut 51 and a retaining ring 47. The pipe secton 45 includes grooves at the mating end with the pipe section 43 for O-ring seals 49 which complete the interconnection of the annular space 38 to a system for supplying a heat exchange medium.

An upper end hub 44 is suitably affixed to the upper end of the outer jacket 32, and similarly a lower end hub 46 is affixed to the lower end of the outer jacket by a weld or fasteners such as bolts (not shown). The upper end hub 44 has an inwardly and downwardly extending annular section 50 and a radially outwardly extending shoulder 52. The outer cylinder 34 fits around the annular section 50 and rests against the shoulder 52. Similarly, the lower end hub 46 has an annular secton 54 and a radially outwardly extending shoulder 56, upon which rests the end of the outer cylinder 34. Suitable O-ring seals 58 and 60 are provided between the ends of the outer cylinder 34 and section 50. The upper end hub 44 is interiorly threaded to threadedly receive the end of the inner cylinder 36. The lower end hub 46 is welded to the inner cylinder 36 and the outer cylinder 34. Thus, there is formed between the upper end hub 44 and the lower end hub 46 and between the outer cylinder 34 and the inner cylinder 36 a sealed annular chamber.

Rotatably mounted within the inner cylinder 36 is a rotor assembly indicated generally by the reference numeral 70. The assembly 70 comprises basically a central rotor 71 to which there is afiixed a plurality of radially extending blade pins 73. Each row of the radially extending blade pins 73 supports a wiper blade 72 which engages the inner surface of the cylinder 36. As the assembly 70 revolves, the blades 72 continuously scrape the inner surface of the cylinder 36 free of any product that adheres thereto.

The upper and lower shaft extension of the assembly 70 rotate in

suitable bushings

76 and 78. A suitable power source drives the assembly 70 through a coupling 79 (illustrated in FIG. 4). The upper end of the rotor 71 is splined at 71a to mate with a similar spline section of the coupling 79.

Bearings

151 and 153 provide a rotatable support for the coupling 79 in a bearing hub 95. Preferably, the assembly 70 is driven by a hydraulic motor 84 (FIG. 1), that is operatively connected thereto and mounted at the upper end of the heat exchanger as illustrated. The hydraulic motor 84 is affixed to and mounted upon the upper head assembly 86 which has an end plate 88 joined to the upper end hub 44 and held assembled thereto by a clamp 90. As best illustrated in FIG. 2, a seal 92 is positioned between the upper surface of the inner cylinder 36 and the inner surface of the end plate 88. The remainder of he upper head assembly 86 consists of a plurality of spacer pins 93 welded to the end plate 88 and rigidly affixed to the bearing hub 95. At the upper end of the bearing hub 95 there is secured a mounting plate 94 for the hydraulic motor 84. If a different drive is used instead of the hydraulic motor 84, the plate 94 may be used to support an adapter for a sheave (not shown) or the like.

AT the lower end of the heat exchanger there is provided a lower head assembly 96 which resembles in some respects the upper head assembly 86. The lower head assembly 96 includes an end plate 98 joined to the lower hub 46 and held assembled thereto by a clamp 100. A seal 101 is positioned between the lower surface of the inner cylinder 36 and the inner surface of the end plate 98. The remainder of the lower head assembly 96 consists of a plurality of spacer pins 118 welded to the end plate 98 and affixed to an upper bearing retainer 116. The lower bearing 1 17 for the assembly 70 is mounted in the upper bearing retainer 116 and a bearing cap 114.

Although the power source of the rotor assembly 70 has been illustrated and described as positioned at the upper end of the heat exchanger, it should be noted that the upper and lower head assemblies may be interchanged. Thus, the power source may be attached to the lower end of the heat exchanger. Where high torques will be produced, a power source may be mounted at both the upper and lower ends of the heat exchanger to drive the rotor assembly 70 from both ends.

Suitable sealing means are provided for the shaft extensions of the assembly 70 where they pass through the

bushings

76 and 78. Referring to FIG. 3, there is shown a sealing mechanism including a seal retainer 121 having an inside diameter 121a slightly larger than the shaft 71 and forced into a position against the bushing 76 by means of a spring 123. Spring 123 is held in place by one of the blade pins 73. An ring seal 125 in the retainer 121 deforms to engage in a sealing manner the shaft 71 and the lower surface of the bushing 76. The surface 121k of the retainer 121 is beveled at approximately l0 F. from the vertical to insure a good sealing relationship between the O-ring seal 125 and the shaft 71. As illustrated in FIG. 2, a similar sealing mechanism is provided for the rotor 71 where it passes through the bushing 78. A seal retainer 127 holds an O-ring 129 in engagement with the shaft 71 and the bushings 78. A spring 131 engages one of the lower blade pins 73 and deforms the O-ring 129 into a sealing engagement with the shaft 71 and the bushing 78,

As discussed previously, heat exchangers for food processing must be cleaned periodically to comply with federal and state laws. With the horizontally oriented swept surface heat exchanger, the procedures for removing the rotor assembly for cleaning often resulted in cylinder damage. In accordance with the present invention, to remove the rotor assembly 70 the clamp 100 is released and the lower head assembly 96 is lowered from the unit by an elevator, generally indicated by the reference numeral 137.

Referring to FIG. 2, there is shown, partly in section, a hydraulic cylinder that provides the power for an elevator to raise and lower the assembly 70. The hydraulic cylinder is indicated generally by the reference numeral 138 and can be of any suitable double action type. This cylinder contains a piston 139 having suitable O-

ring seals

141 and 143. A piston rod connects the the piston 139 and extends from the lower end of the cylinder 138 to the exterior of the outer jacket 32. A lift beam 144 is bolted to the piston rod 140. Beam 144 is also affixed to the lower head assembly 96 by a shoulder bolt 112 threaded into the bearing cap 114. Thus, the elevator 137 and the lower head assembly 96 are normally a single unit, but may be separated by removing the clamp 119. With the clamp 100 released, a suitable control (not shown) admits hydraulic fluid to the cylinder 138 above the piston 139 and also controls the amount of fluid discharged from the cylinder 138 through a fitting 147. In this manner, the rotor assembly 70 and the lower head assembly 96 may be lowered from the unit in a controlled manner, thus preventing damage to the inner cylinder 36. To hoist the rotor and lower head assemblies back into the cylinder 36, hydraulic fluid is pumped into the cylinder 138 through the fitting 147 and discharged from the cylinder through a fitting 145.

Thus, the elevator 137 is powered in both the upward and downward motions, preferably by an oil-gear pump permanently connected to the fittings and 147. By use of an oil-gear pump, the rotor and lower head assemblies may only be lowered by starting the pump and powering the elevator 137 downward. Removal of the clamp 100 will not drop the rotor assembly unless the elevator 137 is powered downward. THus, the elevator 137 provides a safe and simple means of slowly lowering and raising the rotor assembly.

As a wiping blade shears material from the inner wall of the heat exchanger handling a high viscosity material, it produces a cavitation behind the blade. This cavitation volume results in a loss of effective heat exchanger surface. Also, a major pressure differential exists between the leading face of the blade and the back side of the blade. This pressure difference represents torque at the rotor shaft and torque represents horsepower. To reduce this pressure difference and eliminate the cavitation volume, a series of nozzles are formed in the blade along the length thereof as illustrated in FIG. 5. As illustrated, the blade 72 includes a series of nozzle 150 in the shape of an elongated slot with a lip 150a bent in the direction of blade travel, as illustrated by the cross section of FIG. 6. By means of the angle of the lip 150a, the pressure drop across the blade can be reasonably adjusted to insure producing the force necessary to hold the blade against the surface of the inner cylinder 36. As the material is scraped from the inner surface of cylinder 36, a portion thereof passes through the nozzles 150, thereby filling in the area behind the blade. Reductions of input horsepower up to as much as 50 percent have been realized with the blade described. By eliminating the cavitation volume, chilling capacity is improved and blade wear reduced by optimizing the blade pressure on the heat exchange cylinder.

In some applications, it is often desired to change the products used in a particular heat exchanger, preferably with a minimum of time and material lost. Thus, it becomes important that the blade configuration and its mountings are such that no open edges or holes exist to hold long fiber materials such as coconut, beef tissue, fruit pieces, etc. Referring to FIG. 7, there is shown a cross secton of a blade pin 73 supporting a blade 72. As best seen in FIG. 5, the mounting holes 152 in the blade are of a generally rectangular configuration. To assemble a blade 72 on a row of radially extending blade pins 73, the blade is placed in the position illustrated in dotted outline in FIG. 7 and rotated counterclockwise into the position shown. Two

tabs

154 and 156 are secured to the trailing edge of the blade 72 and serve to prevent the blade from camming off the pin 73 after the rotor assembly 70 has been inserted into the inner cylinder 36. As best seen in FIG. 7, when the blade 72 is in its normal scraping position, a space exists between the tab 154 and the inner surface of the heat exchanger.

In another embodiment of the present invention, as illustrated in FIG. 8, a product pump 160 is provided integral with the lower end plate 98. As is the usual practice, like numbers will be used for the embodiment shown in FIG. 8 for parts previously described. Heat exchangers of the type illustrated in FIG. 8 may be used for the continuous production of ice cream or similar aerated or frozen desserts. The product pump 160 meters ice cream mix and air and is provided with a product inlet 162 and an air inlet 164 as shown in FIG. 9. The pump 160 mixes air and an ice cream solution, usually in approximately equal parts, and discharges the mixture through a passageway 166 aligned with a pipe 177 extending substantially the length of a rotor 168. The pipe 170 terminates at its upper end in a curved portion 172 that allows the product to discharge into the space between the rotor 168 and the inside surface of the inner cylinder 36. Thus, the ice cream solution and air mix will be pumped up the center of the rotor through the pipe 170 and be discharged into the upper section of the product chamber formed in the inside of the cylinder 36. This mixture will flow downwardly through the cylinder and be discharged through a pipe 175 at the lower end plate 174.

Basically, the heat exchanger of FIG. 8 is a identical to that of FIGS. 1 and 2. In a manner similar to that described with reference to FIG. 2, the rotor 168 includes radially extending blade pins 73 for supporting wiper blades 72. The wiper blades 72 are preferably of the type described with reference to FIGS. 5-7. A heat exchange medium is introduced into the annular space 38 between the inner cylinder 36 and the outer cylinder 34 through a conduit 41. The heat exchange fluid exists from this annular space through a conduit 42. An upper end hub 44 threadedly engages the upper end of the cylinder 36 and a lower end hub 46 is attached to the lower end. To add rigidity to the inner cylinder 36 and provide a surface at the ends of the inner cylinder for a seal, end rings 59 and 61 are fitted to the upper and lower ends of the cylinder 36, respectively. The upper head assembly 86, only a portion of which has been illustrated in FIG. 8, is identical to that illustrated and described with respect to FIGS. 1 and 2. The lower head assembly includes the product pump 160.

Where a product pump is included as part of the lower head assembly, the lower end plate 174 becomes an integral part of the pump. A pump housing 176 mounts directly to the end plate 174 and is held in place by means of a nut 178 threaded onto a hold down pin 180. The hold down pin 180 also serves as a bearing for a gear 182. The pump illustrated in FIGS. 8 and 10 includes a second gear 184 rotating with a shaft 186 which extends through a mounting hub 188 into the end plate 174. A suitable power source, such as an orbit motor 192, is attached to the hub 188 and provides driving energy for the gear pump.

Typically, pumps for mixing an ice cream mix and air operate at pressures from 50 lbs. to 150 lbs. per square inch. These pumps have a capacity of from 200 gals. to 600 gals. per hour. At 200 gals. per hour, assuming a ratio of 50 percent air and 50 percent ice cream mix, the pump handles about I00 gals. of air per hour or l3 cubic feet per hour. For a pump to handle such a small volume of air at high pressures within a reasonable accuracy, for example plus or minus 3 percent, requires precise machining with reasonably close tolerances to prevent air leakage.

As explained previously, such pumps must be cleaned daily with an accepted cleaning procedure set by rule of local and federal health authorities. The cleaning procedure commonly approved uses water at 180 F. Considering that a pump must accurately deliver small volumes of air at approximately 30-40 F. during operation, the normal expansion and contraction of the pump material at the cleaning cycle temperature becomes important if the pump is cleaned in place. Also, the lubrication of hot water is very low and most materials are damaged by the lack of lubrication during the cleaning cycle in a clean-in-place procedure.

The material recommended by any sanitary codes for swept surface heat exchangers is an 18-8 stainless steel or equivalent. Unfortunately, 18-8 stainless steel is one of the poorest bearing materials existing. In accordance with the present invention, hard facing wearing

surfaces

190 and 191 are provided in the mating surfaces of the gears and pump housing, respectively. The hard facing wearing surfaces 190 of the

gears

182 and 184 may be of a super hard stainless steel which is ground and lapped to extend about 0.001 percent above the tooth area of the gears, thus eliminating contact between the gear surface and the mating pump body surface. The mating surface of both the pump housing 176 and the lower end plate 174 may also be a case hardened super hard stainless steel, ground and lapped to run and match with the hardened inserts of the gear ratio. As illustrated in FIG. 10, the hard facing wearing surfaces 190 of the

gears

182 and 184 are in an area surrounding their respective shafts.

To eliminate the problem of binding between the gears and pump housing during a clean-in-place procedure, the nut 178 is backed off a fraction of a turn to permit the pump housing 176 to be displaced from mating contact with the lower end plate 174. An annular groove formed in the pump housing 176 includes an O-ring seal 194 that maintains a seal during the cleaning operation, thereby permitting cleaning the pump 160 in place.

As discussed previously, heat exchangers for food processing must be cleaned periodically to comply with federal and state laws. With the embodiment shown in FIG. 8, to remove the rotor assembly 168, the clamp is released and the pump and lower end plate 174 removed from the unit. A releasable latch mechanism holds the rotor assembly in place until and elevator, generally indicated by the reference numeral 137, can be brought intoplace. The elevator 137 is. similar in many respects to that described with reference to FIG. 2. Instead of the lift beam 144 being permanently affixed to the heat exchanger, it is free to be rotated out of the way when the pump 160 and end plate 174 are assembled to the inner cylinder 36.

During the time that the rotor 168 is in place within the cylinder 36 and the lower end plate 174 has been removed, the rotor assembly is held in place by a releasable latch mechanism as illustrated in FIG. 11. The upper end of the rotor 168 is splined as at 16817 to mate with a similar spline section of the coupling 179,

Bearings

151 and 153 provide a rotatable support for the coupling 179 in the bearing hub 195. The releasable latch mechanism itself consists of a spline latch 124 secured to the upper end of the rotor 168 by means of a shoulder screw I22 threaded into the rotor. The latch 124 is free to rotate about the shoulder screw 122 and has a spline configuration similar to that of the section 168b. Splines on the latch 124 are loaded by a spring (not shown) into a position such that they are aligned with the splines of the coupling 179, as illustrated in FIG. 12. Thus, with the latch 124 in its normally biased position, the splines thereof will engage the individual splines of the coupling 179 and hold the rotor assembly 168 in place in the inner cylinder 36.

A latch pin 126 having a camming surface 126a extends through an opening in the coupling 179 in the area of the latch 124. A spring 128 loads the latch pin 126 such that the camming surface 126a does not engage the latch 124. A spring 130 encircles the coupling 179 in a groove therein and holds the pin 126 in place.

To operate the latch mechanism and release the rotor assembly 168 for removal thereof from the inner cylinder 36, air pressure is applied to the bearing hub by means of a fitting 132 to pressurize a chamber 134 formed by the

bearings

151 and 153. As the pressure in the chamber 134 increases, a force is developed on the pin 126 which forces the camming surface 126a against a spline of the latch 124. The latch 124 rotates by an amount such that the latch splines line up the splines of the rotor 168. The rotor assembly 168 may now be removed from the inner cylinder 36.

To couple the rotor 168 with the coupling 179, the latch 124 is made to engage the spline section of the coupling and the rotor assembly 168 given a fractional turn to align the splines 168b with the splines of the coupling 179. The rotor assembly 168 is raised in place and when the lower edge of the latch 124 passes the upper edge of the spline section of the coupling 179, the latch 124 rotates into the position shown in FIG. 12, that is, the rotor holding position.

A vertically oriented swept surface heat exchanger of the type shown in FIG. 8 may be completely filled with the ice cream and air mix by venting the inner cylinder 36 at the shaft extension of the rotor 168. The shaft extension 168a includes a groove 204 which is below the inner surface of the bushing 76 during venting of the inner cylinder 36, as illustrated in FIG. 8, and raised to a position within the bushing after the cylinder has been filled, as illustrated in FIG. 13. A suitable sealing mechanism is provided for the shaft extension 168a of the type similar to that illustrated in FIG. 2. Referring to FIG. 13, there is shown a sealing mechanism for the shaft extension 168a including a seal retainer 216 having an inside diameter slightly larger than the shaft extension 1680, and a sidewall 216a tapering at an angle of approximately l F. with the vertical. A spring 208 exerts a force on the retainer 206, when the shaft 168 is in its raised position, to deform an O-ring seal 210 against the bushing 76. When the shaft 168 is in a venting position, the O-ring 210 disengages the bushing 76 and air or a cleaning fluid will pass around the O-ring through the groove 204 and out ofthe cylinder 36 by means ofa vent pipe 212.

An important feature of the sealing mechanism described is that as a better seal is required, because of higher internal pressures, a tighter seal will be produced. The taper of the sidewall 216a exerts more force on the O-ring seal 210 as the internal pressure of the inner cylinder 36 increases on the retainer 216, thereby forcing the O-ring seal in tighter engagement with the shaft extension 168a and the bushing 76.

With the venting system illustrated in FIG. 13, some clearance must be provided between the shaft extension 168a and the bushing 76 for proper venting through the pipe 212. This necessitates a sealing mechanism for the shaft extension 1680 at the upper surface of the bushing 76. A sealing mechanism similar to that previously described is provided. A seal retainer 214 holds an O-ring seal 206 in engagement with the shaft extension 168a and the bushing 76. A spring 218 engages the coupling 179 and deforms the O-ring seal 206 into a sealing engagement with the shaft extension 168a and the bushing 76.

At the lower end of the rotor 168 there is provided a rotor guide 196 which engages a rotor hub 198. The rotor hub 198 is an integral part of the lower end plate 174 and contains the passage 166. An O-ring seal 200 forms a seal between the rotor hub 198 and the rotor guide 196.

At the start of the pumping the ice cream and air mix into the inner chamber 36, the rotor 168 will be positioned as shown in FIG. 8. The pressure of the inner cylinder will be maintained at the atmospheric level as a result of the annular passage between the shaft extension 168a and the bearing hub 76. Consequently, little if any back pressure will be developed within the pipe 170 as the cylinder fills with the ice cream and air mix. As the inner cylinder 36 fills to a point such that the outlet of pie 170 is blocked, a back pressure will be developed in a chamber 202 formed between the rotor guide 196 and the rotor hub 198. This back pressure creates an upward force which tends to raise the rotor 168. As the inner cylinder 36 continues to fill, thick back pressure increases until the O-ring seal 205 on the shaft extension 168 is forced against the bushing 76, thereby sealing the inner chamber 36. The rotor 168 will remain in this raised position and the inner chamber 36 will be sealed throughout the operation of the heat exchange unit.

While several embodiments of the invention, together with modifications thereof, have been described in detail herein and shown in the accompanying drawings, it will be evident that various further modifications are possible without departing from the scope of the invention.

What is claimed is:

1. A vertical swept surface heat exchanger having an inner cylinder provided with removable upper and lower head assemblies and enclosed by an outer cylinder which form an annular chamber therewith for passage of a heat exchange medium, comprising:

a rotor, including radially extending blade pins, positioned within the jacketed inner cylinder by the upper and lower head assemblies and having a drive shaft extending through a bushing in the upper head assembly, said rotor being removable form the inner cylinder by moving the drive shaft axially downward from within the bushing in the upper head assembly.

drive means mounted to the upper head assembly and engaging said drive shaft for imparting rotary motion to said rotor,

wiping blades extending substantially the length of said inner cylinder supported on the blade pins of said rotor in a manner to insure the sweeping action of the inner surface of the cylinder during rotation of said rotor, and

sealing means at the upper and lower ends of said rotor within said inner jacketed cylinder, said upper sealing means being carried by the drive shaft for biased engagement with the inner surface of the upper head assembly only when said rotor is positioned within the inner cylinder.

2. A vertical swept surface heat exchanger having an inner cylinder provided with removable upper and lower head assemblies and enclosed by an outer cylinder which forms an annular chamber therewith for passage of a heat exchange medium, as set forth in claim 1, which also includes:

elevator means mounted adjacent the outer cylinder and including a lift beam for engaging the lower head assembly for raising, lowering and positioning said rotor, wiping blades and sealing means for assembly thereof within said cylinder.

3. A vertical swept surface heat exchanger having an inner Cylinder provided with removable upper and lower head assemblies and enclosed by an outer cylinder which forms an annular chamber therewith for passage of a heat exchange medium as set forth in claim 1, which also includes:

means at the upper and lower portion of the annular chamber for mounting the jacketed cylinder in a vertical position, said means including passageways for providing an inlet and outlet to said chamber for a heat exchange medium.

4. A vertical swept surface heat exchanger having an inner cylinder provided with removable upper and lower head assemblies and enclosed by an outer cylinder which forms an annular chamber therewith for passage of a heat exchange medium, comprising:

a rotor, including radially extending blade pins, positioned within the jacketed inner cylinder by the upper and lower head assemblies and having a drive shaft extending through bushings in the upper and lower head assemblies, said rotor being removable from the inner cylinder by moving the drive shaft axially from within one of the two bushings,

sealing means at the upper and lower ends of said rotor within said inner jacketed cylinder, said sealing means being carried by the drive shaft for biased engagement with the respective inner surfaces of the upper and lower head assemblies when the drive shaft is fully extended through the upper and lower bushings.

5. A vertical swept surface heat exchanger having an inner cylinder provided with removable upper and lower head assemblies and enclosed by an outer cylinder which forms an annular chamber therewith for passage of a heat exchange medium, comprising:

wi l

a rotor removably positioned within the inner jacketed cylinder by the upper and lower head assemblies and having a drive shaft extending through bushings in the upper and lower head assemblies, said rotor including blade pins extending radially therefrom,

sealing means mounted to the upper and lower ends of said rotor within said inner jacketed cylinder, said sealing means including a seal retainer ring having a flanged outer edge and a tapered inner surface, a helical spring surrounding the drive shaft having one end fixed to said rotor to bias the seal retainer toward the bushing and an O-ring surrounding the drive shaft between the seal retainer and the bushing, whereby insertion of the drive shaft into the upper and lower bushings presses the seal retainer and O-ring against the bushing and drive shaft junction to form a seal and removal of the drive shaft from the bushing releases the pressure on the O-ring to break the seal,

drive means mounted to the upper head assembly and engaging said drive shaft for imparting rotary motion to said rotor, and

wiping blades extending substantially the length of said inner cylinder supported on the blade pins of said rotor in a manner to insure the sweeping action of the inner surface of the cylinder during rotation of said rotor.

Claims

1. A vertical swept surface heat exchanger having an inner cylinder provided with removable upper and lower head assemblies and enclosed by an outer cylinder which form an annular chamber therewith for passage of a heat exchange medium, comprising: a rotor, including radially extending blade pins, positioned within the jacketed inner cylinder by the upper and lower head assemblies and having a drive shaft extending through a bushing in the upper head assembly, said rotor being removable form the inner cylinder by moving the drive shaft axially downward from within the bushing in the upper head assembly. drive means mounted to the upper head assembly and engaging said drive shaft for imparting rotary motion to said rotor, wiping blades extending substantially the length of said inner cylinder supported on the blade pins of said rotor in a manner to insure the sweeping action of the inner surface of the cylinder during rotation of said rotor, and sealing means at the upper and lower ends of said rotor within said inner jacketed cylinder, said upper sealing means being carried by the drive shaft for biased engagement with the inner surface of the upper head assembly only when said rotor is positioned within the inner cylinder.

2. A vertical swept surface heat exchanger having an inner cylinder provided with removable upper and lower head assemblies and enclosed by an outer cylinder which forms an annular chamber therewith for passage of a heat exchange medium, as set forth in claim 1, which also includes: elevator means mounted adjacent the outer cylinder and including a lift beam for engaging the lower head assembly for raising, lowering and positioning said rotor, wiping blades and sealing means for assembly thereof within said cylinder.

3. A vertical swept surface heat exchanger having an inner cylinder provided with removable upper and lower head assemblies and enclosed by an outer cylinder which forms an annular chamber therewith for passage of a heat exchange medium as set forth in claim 1, which also includes: means at the upper and lower portion of the annular chamber for mounting the jacketed cylinder in a vertical position, said means including passageways for providing an inlet and outlet to said chamber for a heat exchange medium.

4. A vertical swept surface heat exchanger having an inner cylinder provided with removable upper and lower head assemblies and enclosed by an outer cylinder which forms an annular chamber therewith for passage of a heat exchange medium, comprising: a rotor, including radially extending blade pins, positioned within the jacketed inner cylinder by the upper and lower head assemblies and having a drive shaft extending through bushings in the upper and lower head assemblies, said rotor being removable from the inner cylinder by moving the drive shaft axially from within one of the two bushings, drive means mounted to the upper head assembly and engaging said drive shaft for imparting rotary motion to said rotor, wiping blades extending substantially the length of said inner cylinder supported on the blade pins of said rotor in a manner to insure the sweeping action of the inner surface of the cylinder during rotation of said rotor, and sealing means at the upper and lower ends of said rotor within said inner jacketed cylinder, said sealing means being carried by the drive shaft for biased engagement with the respective inner surfaces of the upper and lower head assemblies when the drive shaft is fully extended through the upper and lower bushings.

5. A vertical swept surface heat exchanger having an inner cylinder provided with removable upper and lower head assemblies and enclosed by an outer cylinder which forms an annular chamber therewith for passage of a heat exchange medium, comprising: a rotor removably positioned within the inner jacketed cylinder by the upper and lower head assemblies and having a drive shaft extending through bushings in the upper and lower head assemblies, said rotor including blade pins extending radially therefrom, sealing means mounted to the upper and lower ends of said rotor within said inner jacketed cylinder, said sealing means including a seal retainer ring having a flanged outer edge and a tapered inner surface, a helical spring surrounding the drive shaft having one end fixed to said rotor to bias the seal retainer toward the bushing and an O-ring surrounding the drive shaft between the seal retainer and the bushing, whereby insertion of the drive shaft into the upper and lower bushings presses the seal retainer and O-ring against the bushing and drive shaft junction to form a seal and removal of the drive shaft from the bushing releases the pressure on the O-ring to break the seal, drive means mounted to the upper head assembly and engaging said drive shaft for imparting rotary motion to said rotor, and wiping blades extending substantially the length of said inner cylinder supported on the blade pins of said rotor in a manner to insure the sweeping action of the inner surface of the cylinder during rotation of said rotor.