US3430928A

US3430928A - Scraping apparatus

Info

Publication number: US3430928A
Application number: US627695A
Authority: US
Inventors: Robert L Smith
Original assignee: Chemetron Corp
Current assignee: SPX Corp
Priority date: 1967-04-03
Filing date: 1967-04-03
Publication date: 1969-03-04
Anticipated expiration: 1986-03-04
Also published as: BR6898061D0

Description

March 4, 1969 R. 1.. SMITH SCRAPING APPARATUS Sheet Filed April 5. 1967 Inventor.

ROBERT LY-SMITH M r h 4, 9 'R. L. SMITH,

SCRAPING APPARATUS Sheet Filed April 5. 1967 Inveniwr ROBERT L.SMETH m Q "I l lllIlllll United States Patent 9 Claims ABSTRACT OF THE DISCLOSURE Heat exchange apparatus having a slotted shaft and a plurality of polygonal scrapers mounted for sliding movement in the slots of the shaft for scraping a wall of a heat exchanger. Said scrapers being movable by centrifugal force, upon rotation of the shaft into scraping contact with the wall.

This invention relates in general to scraped surface heat exchangers and more particularly to a plurality of scraping blades of triangular configuration which are mounted on a shaft rotatably carried within a cylindrical chamber of the heat exchanger. By virtue of the triangular shape, three edges at the vertices thereof are selectively positionable for scraping engagement with the interior wall of the chamber during the rotation of the shaft.

Scraped surface heat exchange apparatus are useful for treatment of materials which are passed through an annular space defined by a jacketed cylinder and a revolving mutator shaft which is journalled for rotation about the axis of the cylinder. Generally the shaft carries blades for scraping the cylindrical heat exchange surface, how ever, prior to this invention, the blades for scraping of a surface had only a single edge for scraping the product from the tube wall. As the blade edge became worn or damaged, a removal and sharpening, or a complete replacement of the blade structure was necessary. Further, the scraper member is often mounted on a number of radially disposed pins which are carried on the rotatable shaft. Such spaced mounting is subjected to relatively strong forces as the sharpened blades are continuously moved in plowing or scraping engagement with the tube wall.

It is an object of the present invention to provide novel scraper apparatus carried by a rotating shaft which apparatus is adapted to effectively scrape the interior wall surface of a tubular heat exchanger associated therewith.

It has been found in treating margarine, shortening, and similar products, that certain hard fats, such as those fats with higher melting point fractions, tend to give erratic results with conventional blade and pin mounting structure On occasion, some small particles or specks of these hard fats are carried along into the final product. This is due to the fact that hard fats may tend to build up on portions of the tube wall while the blade rides over the built up fats. This necessarily results in uneven or erratic blade contact with the wall.

It is a feature of this invention to mount the scraper blade normal to the tube surface for providing improved scraping action.

It is a further feature of this invention that the scraping contact between the wall and the rotating blade is dependent upon centrifugal force which is variable through changes in rotational shaft speed and/or weight of the blade assembly.

An additional feature of this invention is that a polygonal blade configuration is provided which is stronger and which is capable of being repositioned to selectively present at least one of the three scraping edges at the vertices thereof for scraping contact with a tube surface and thus provide for increased blade life.

It is a further feature of this invention to provide staggered positioning of the blade portions for positively mixing materials being treated therein with less tendency for mass rotation of product.

Another object of this invention is to provide a scraping apparatus which is simply attachable to a rotatable shaft and is inexpensively manufactured yet is of rugged, durable construction.

Further objects, as well as features and advantages of this invention will become apparent as the following description of an illustrated embodiment thereof proceeds, given for the purpose of disclosure and taken in conjunction with the accompanying drawings in which like character references designate like parts throughout the several views and Where:

FIGURE 1 is a perspective view of a scraped surface heat exchanger incorporating the principals of the present invention, with portions being broken away to illustrate the invention;

FIGURE 2 is a vertical sectional view taken along the line 22 of FIGURE 1, looking in the direction indicated by the arrows;

FIGURE 3 is a vertical sectional view corresponding generally to FIGURE 2, but illustrating another embodiment of this invention;

FIGURE 4 is a perspective view of another embodiment of a blade comprising this invention;

FIGURE 5 is an exploded elevational view of a rotary seal assembly which may be utilized with the invention;

FIGURE 6 is a partial sectional view illustrating the invention retained on a mutator shaft;

FIGURE 7 is a partial top plan view illustrating a hinge member for connecting a train of blade bars; and

FIGURE 8 is a vertical sectional view taken along the line 8-8 of FIGURE 6, looking in the direction indicated by the arrows.

Referring now to the several figures and first to FIG- URE 1, a heat exchange apparatus embodying the invention is illustrated generally at 11 being supported on a frame 13. The heat exchange apparatus comprises an elongated heat transfer tube or cylindrical chamber 15 which is attached at its ends to a pair of ring-like members 17 and 18. These members also support a second tube 19, which is somewhat larger than the tube 15 and is concentrically disposed with respect thereto and which together with said tube 15 defines an annular jacket space 21 for containing the heat transfer medium, such as water, brine, ammonia or steam. The tube 19 is surrounded by insulation 23 which is enclosed within a cylindrical outer shell 25.

Conduit elements

27 and 29 provide means for inlet and outlet of the heat transfer medium of the annular jacket space 21.

A pair of

end plates

31 and 33 are attached to the ring like members 17, 18 at either end of the heat exchange apparatus. The

end plates

31 and 33 are mounted in conventional manner so as to be in sealed relationship with the heat transfer tube 15. The end plate 31 is provided with bearing means indicated at 35 and the plate 33 is provided with similar bearing means. A mutator shaft 37 extends through and is journalled in said bearing means. Thus the mutator shaft 37 is mounted for rotation within the cylindrical chamber 15 and together with the chamber defines a generally annular space 39. A product inlet 38 through the plate 31 and a product outlet 40 through the plate 33 provide ingress and egress means respectively, for the material moving through the annular space 39. As is the usual practice in apparatus of this kind, suitable means for rotating the shaft 37, such as by a motor 41, is provided.

As shown in FIGURE 2 an enlarged central portion of the shaft 37 has supported thereon a plurality of scraper blades 43. The blades 43 are slidingly disposed in slots formed generally longitudinally of the shaft. Each blade is arranged to extend outwardly beyond the surface of the central portion of the shaft and to scrapingly contact the inner surface of the cylindrical chamber 15. By suitable dimensioning the slot 45, the blades 43 are movable from a retracted position wherein the blades are spaced from the cylinder wall to their extended positions wherein they contact the inside surface of the cylindrical chamber.

A knife-like edge for scraping the surface of the tube free of the material undergoing heat transfer is provided by at least one of the vertices 47 of the triangularly shaped scraper blades 43. By configuring the scraper blades in the form of an equilateral triangle, the three vertices can be simply rotated and repositioned for scraping contact with the tube 15. This offers the advantage of increased blade life. Other geometric shapes would lend themselves to this invention, for example, hexagonal shaped blades.

The direction of the rotation of the shaft 37 is indicated by the arrow 49 and thus the vertices 47 of the blades 43 are continuously moving in the direction of the arrow as the shaft rotates. Upon rotation of the shaft, centrifugal force and the resistance of the material being processed cause the blades 43 to move outwardly of the slot 45 along a chordal segment 51 of the slot from their retracted position to their scraping positions. Thus, the vertices are continuously in contact with the inside surface of the heat transfer tube 15. In the embodiment illustrated in FIG- URE 2 the altitude of each blade intersects the chamber 15 at an acute angle so as to scrape the materials from the surface thereof. The supporting contact between the base of the blade and chordal segment 51 provides a strong support for the blade and aids in preventing the blade from tipping out of its respective slot.

The scraper blades 43 (FIGURE 4) are formed of spaced scraping sections 53 which are integrally connected by relieved portions 55 therebetween. While four blades 43 are shown arranged about the shaft 37, it is contemplated that the other numbers of blades such as two oppositely disposed blades, would provide the advantages of this invention. The blades 43 may be composed of any suitable materials, such as steel or a suitable plastic material, such as polytetrafluoroethylene, which is sold commercially under the name Teflon.

In order to improve the movement of the materials in the chamber, the blades 43 are arranged in a staggered pattern about the surface of the shaft 37. That is, the l blades 43 are disposed 90 apart with the individual scraping sections 53 thereof disposed so as to overlap the scraping sections of the adjacent rows. In this way, the full inside surface of the tube 15 is scraped even though the relieved portions are provided between adjacent scraping section 53 of a particular blade 43. By such a staggered arrangement, an improved mixing action is provided as the shaft rotates since each scraping section acts somewhat like a plow, forcing materials ahead of it. However, the material tends to resist the action of the blade and to split around the sides of the blades with portions of the material passing on either side thereof to be subsequently moved ahead by a scraping section 53 of a following blade. By this continual splitting of the mass of moving mate rial, positive mixing is provided with reduced tendency for mass rotation of the product. By reversing the direction of rotation of the shaft 37, it can be seen that the blades will rock from their normal scraping position and move away from their normal scraping contact with the surface of the tube 15 to provide for easy cleaning of the blades. The blades are repositionable to selectively move an unused edge of the blade into scraping contact with the tube surface. It is also possible to turn the blades end for end and remount them in their respective slots 45 to position still another edge portion of the vertices 47 for scraping,

that is the portion which was formally the trailing edge thereof and which was not subject to wear.

As hereinbefore discussed, the triangular blade structure has the advantage that the major surface of the base is supported by the chordal segment 51 of the shaft while it is free to move outwardly from centrifugal force and product resistance. By simply reorienting the triangular blades and their respective slots, the blades may be positioned so that the face of each blade presents a reverse incline for contacting the product and thus minimizes product drag and excessive power consumption. In an embodiment wherein the blades are removably disposed within the slots themselves (FIGURE 2), the slots are generally V-shaped and extend generally longitudinally along the entire body of the shaft 37 but the blades may also be mounted in spaced slot segments each of which has a cooperative individual blade disposed therein.

Centrifugal force and the resistance of the material undergoing processing causes the extended vertices of the blade to be forced relatively outwardly into continuous contact with the wall of the tube 15 so as to continuously scrape the material being processed off the tube wall. Thus, with the passage of each blade, the heat exchange surface is swept clean of the static film and replaced by additional portions of the material undergoing processing. This treatment provides for highly efficient heat transfer with respect to the material. As pointed out before, the blades when mounted in a staggered arrangement further provide a kneading action so that the material or product within the annular space 39 undergoes not only heat transfer or a change in temperature but is also thoroughly mixed during its passage through the apparatus.

The blades are simply held from longitudinal movement along the shaft by means of retainers 57 at each end thereof. The retainers include flange segments 58 which overlap portions of the blades and limit their axial movement. The blades structure of this invention permits repositioning or replacement thereof without the time consuming operation of removing the shaft. The change can 'be accomplished by removing one end only such as end plate 31 and the retainer 57. Then, the change of blade can be simply accomplished by longitudinally drawing the blade 43 from the slot in which it is seated, repositioning the blade and reinserting the same or a new blade in its place.

To prevent the product from leaking from the heat exchanger and to hold the retainer in position as the mutator rotates, seal means (FIGURE 5) are provided at each end of the shaft. A pair of wavy washers 52, 54 force the retainer 57 into contact with the enlarged portion of the shaft. A seal backing ring 56 engages washer 54 on one side thereof and engages an O-ring 60 on its other side. A seal body 62 overlaps the ring 60 and backing ring 56 and sealingly seats the ring 60 about the shaft 37. A head insert 65 is retained by the end plate 31 and has O-rings 64 and 67 on either side thereof for preventing leakage of product from the heat exchanger during treatment.

To enhance and/or alter the scraping action of the blade, the centrifugal force on the blade may be varied through changing the rotational speed of the shaft and/ or the weight of the blade assembly. The blade itself may be weighted for example by using a heavier material therefor or the relieved portions 55 may be formed of a weighted material.

In a modified arrangement for supporting the scraper blades (FIGURE 3), each blade 43' is carried in a generally dovetailed slot 59 provided in one surface of a mounting bar 61. Each bar 61 is mounted in a generally U-shaped slot 63 formed longitudinally of the enlarged central portion of the mutator shaft 37'. The bars 61 are each slidingly positioned in their respective slots to move the triangular blocks relatively radially of the axis of the shaft 37' from their retracted positions to their extended positions upon rotation of the shaft. In order to improve the scraping action of the blades, the bars may be weighted so as to increase the centrifugal forces acting thereon. The bars 61 are retained against longitudinal and axial movement with respect to the shaft 37 by the retainer 57. The flange segment 58' extends over a hinge member 69 which extends from one end of each bar 61. A bifurcated hinge member 71 is formed at the other end of each bar. A pin 73 passes through aligned holes formed in the hinge members 69, 71 to join adjacent bars together in the form of a train.

The blade is mounted so that the altitude thereof is normal to the cylinder wall. In this way the blade presents a reverse incline for the face contacting the product thereby minimizing product drag and excessive power consumption. The numerous advantages and arrangements of the scraper blades hereinbefore described apply equally to the embodiment wherein, the blades are registered with and positioned in the generally dovetailed slots 59 of the bars 61.

Applicants device provides a highly useful apparatus for continuously processing materials moving through a hollow cylindrical chamber. The triangular blade system provides at least three available wearing edges which may be selectively brought into scraping contact with the wall of the cylinder. The blades move outwardly into scraping contact with the wall upon rotation of the shaft on which they are carried. Additional weight may be added to the blade to improve the contact between the blade and the wall.

Thus, it will be appreciated that all of the recited objects, advantages and features of the present invention have been demonstrated as obtainable in a highly practical mechanism and one that is not only simple and positive in operation, but also inexpensive to manufacture. It will be further understood that although the invention has been described with respect to certain specific embodiments thereof, it is to be understood that the invention is not limited thereto, since various modifications of said invention will suggest themseves from the aforesaid description and are intended to be incompassed within its scope of the appended claims wherein there is claimed:

1. A scraper apparatus for moving materials within a cylindrical chamber comprising: a shaft having a plurality of generally longitudinally disposed slots mounted for rotation within the chamber each slot having a segment positioned chordally of the shaft and a plurality of polygonal blade elements removably disposed Within the slots, each of said blade elements having sides and vertices at the intersection of adjacent ones of the sides and having at least one of the vertices thereof extending outwardly of the shaft to an extended position wherein the extending vertex portion of the blade is in scraping contact with the cylinder wall and a slide opposite the extending vertex portion supportingly contacts the chordal segment of the slot upon revolution of the shaft.

2. The scraper apparatus as claimed in claim 1, whereing each of the blades is triangular in cross section and the side opposite of the blade is movable with respect to the chordal segment of the slot in which it is disposed between the extended position and a retracted position wherein the blades are spaced from the cylinder wall.

3. A scraper apparatus for moving materials within a cylindrical chamber comprising: a shaft having a plurality of generally longitudinally disposed slots mounted for rotation within the chamber and a plurality of polygonal blade elements removably disposed within the slots, each of said blade elements having at least one of the vertices thereof extending outwardly of the shaft to an extended position wherein the extending vertex portion of the blade is in scraping contact with the cylinder wall upon revolution of the shaft; each of the blades is triangular in cross section and is movable with respect to the slot in which it is disposed between the extended position and a retracted position whereby the blades are spaced from the cylinder wall; and each of the slots are generally V-shaped with one side thereof presenting a chordal surface supporting a base surface of the blade disposed therein and along which the blade slidingly moves from the retracted position to the extended position.

4. The scraper apparatus as claimed in claim 3 wherein each of the blades is weighted to freely move the blades from their respective retracted positions to their respective extended position by centrifugal force upon revolution of the shaft.

5. The scraper apparatus as claimed in claim 3 wherein each of the blades comprises at least two spaced scraping sections and a relieved portion extends between adjacent ones of said spaced scraping sections.

6. The scraper apparatus as claimed in claim 5 wherein each relieved portion is weighted so as to freely move the blades from their retracted positions to their extended position by centrifugal force upon revolution of the shaft.

7. A scraper apparatus for moving materials within a hollow, cylindrical chamber comprising: a shaft having a plurality of generally longitudinally disposed slots mounted for rotation within the chamber and a plurality of polygonal blade elements removably disposed within the slots, each of said blade elements having at least one of the vertices thereof extending outwardly of the shaft to an extended position wherein the outermost vertex portion of the blade is in scraping contact with the cylinder wall upon revolution of the shaft, each of the blades being triangular and movable with respect to the slot in which it is disposed between the extended position and a retracted position wherein the blades in the latter position are spaced from the cylinder wall, and a weighted bar mounted in each slot and positioned to move the polygonal blade disposed in the corresponding slot from its retracted position to its extended position by centrifugal force upon revolution of the shaft.

8. The scraper apparatus as claimed in claim 7 wherein each bar is provided with a generally dovetailed slot for receiving one of the blades therein.

9. The scraper apparatus as claimed in claim 8 wherein each of the blades comprises a plurality of longitudinally spaced apart scraper sections and an integral relieved portion extends between adjacent ones of said scraper sections.

References Cited UNITED STATES PATENTS 2,589,350 3/1952 E-dmunds 259-9 X 3,250,311 5/1966 Thier 15246.5

ROBERT W. JENKINS, Primary Examiner.

US. Cl. X.R.