US2534054A - Conveyer - Google Patents

Description

E?. C PARKS Dec.n 12, 1950 Filed June 6 1946 INVENTOR. EALYA C. FAEKES ATToE/EY w@ E K mm A @h C.

4 Sheets-Sheet 3 wm N u fm\ m\ www NT TN INVENToR. RALPH C- PAEKES ATToZ/EY Patented Dec. l2, 195() UNITED STATES PATENT OFFICE coNvEYEn Ralph C. Parkes, Glenslde, Pa.

Application June 6, 1946, Serial No. 674,855

6 Claims. (Cl. 198-129) The object of this invention is to produce an improved drying machine of the type which includes a drying chamber, means for supplying a duid-drying medium, such as heated air, to said chamber, and an endless conveyor for carrying the material to be dried through the drying chamber. Machines of this type are sometimes used not only for drying, but also for curing certain materials by subjecting the material to the desired heat after the drying operation is completed.

Most, if not all, drying operations include a first stage, which is known in the trade as the constant drying rate stage, and a second stage, which is known as the falling drying r-ate stage. During the first stage the rate of evaporation is such that the temperature of the .material remains substantially constant. During the second stage the rate of evaporation progressively decreases and the temperature of the material progressively rises until, when the drying operation is completed, the temperature of the material and the air are substantially constant and substantially equal.

Where it is also desired to cure the material, it is subjected to the constant temperature rei'erred to for a predetermined period of time.`

Obviously, the third or curing stage cannot begin until the end of the second stage because, until the material is fully dry, its temperature will not be constant but will still be rising, while the temperature of the air will still be falling, though at a lesser and lesser rate.

In the interest of maximum elciency in the execution of each of said stages, an optimum ratio should be maintained between the available, usuable heat per unit area and per unit time and the heat requirement per unit area and with reference to the particular part of the machine or the particular stage. For example, during'the l.first stage, a loop of cloth or a pound of loose bulk material having a given moisture content can be eillciently dried by being subjected, during a .given length of time, to the usable heat contained in one cubit vfoot of air heated to a given temperature and distributed over a given unit :area of the drying chamber, it follows that there should be one loop or one pound of material to such unit area. During the second stage the rate of drying progressively decreases and the heat requirement decreases. Therefore, if eiliclency of operation is to be maintained, the available heat must be decreased or the heat requirement must be increased. To decrease the avail- -able heat involves adjustment of volume, speed and temperature of the air and slows down the operation of the machine, thus further impairing the efficiency of the machine. It is, therefore. preferable to increase the heat requirement by progressively increasing the number of loops or the amount of loose material per unit area, or by slowing the rate of movement of the material through the drying chamber, or both, whereby the drying capacity of the machine is increased per unit area, thus increasing the efciency of the machine.

To this end, it has heretofore been proposed Q to use multiple superimposed conveyors which may or may not travel at different rates of speed and with the material to be dried moving progressively from the upper to the lower conveyors. Such an arrangement is only available when loose bulk material is to be handled and is not readily adapted for the handling of web in the form of loops. Furthermore, such an arrangement is expensive to manufacture. install and maintain, and it adversely aiects the eillciency of the air system and necessitates special design or design of material portions of the drying machine. Multiple conveyors have, therefore, been frequently discarded in favor of single apron conveyors.

It is, therefore, a further object of the invention to produce an improved drying machinek in which an optimum ratio is maintained between the heat requirement per unit area and the heat available per unit area without changing the temperature, volume or speed of the air, without the use of multiple conveyors, and without varying the `rate at which the material is fed into or withdrawn from the machine.

A still further object is to produce an improved structure which, when calibrated or adjusted for a given set of conditions, will perform accurately and automatically.

A stil1 further object is to produce an improved structure which will operate satisfactorily, regardless of whether the drying operation comprises constant and falling drying rate stages only, or whether it also includes a third or curing stage.

A still further object is to produce an improved structure which is durable, inexpensive to make and install and which can be installed in a conventional, conveyor-type drying machine with minimum interference with, or alteration of, the structure of the machine itself.

A still further object is to produce an improved machine which is adapted for the drying of web or sheet material or for the drying of loose bulk 3 material such as synthetics. vegetable matter, sludge, etc.

Furthermore, when the machine is used for drying cloth, it is necessary that the optimum ratio between the heat requirement and the usable heat be maintained not only to obtain maximum efficiency, but, also, so as to obtain a satisfactory product. For example, if the heat available per unit area is less than the heat requirement of the material per said unit area, one portion of the material, such as the end of the loop against which the heated air iirst impinges, will dry faster than the other portions thereof. The unbalance of the moisture content causes the moisture to creep from the relatively wet to the relatively dry portions. This alters the pigment distribution and produces non-uniform coloration which is known in the trade as shading. The same non-uniformity of drying is objectionable when the material is to be not only dried but is to be cured also, because curing involves subjecting the material, throughout all of its parts, to a uniform constant temperature. Therefore, if the surface portions of the material dry before the center portions thereof, the temperature of the material will still be rising instead cf constant and the surface portions will A' begin to cure before the center portions are fully dried. Non-uniform curing is not only ineilicient but may also damage the product.

It is, therefore, a still further object of the invention to produce an improved drying machine structure by means of which the material is so subjected to a constant usable heat that the material is dried substantially uniformly throughout all portions thereof and throughout the drying chamber so as to prevent shading, or nonuniform drying or non-uniform curing.

A still further object of the invention is to increase the capacity of the machine without increasing the dimensions thereof, without increasing the temperature, volume or speed of the air, and without increasing the rate at which the material is fed into or withdrawn from the machine.

These and other objects are attained by my invention as set forth in the following specification and as illustrated in the accompanying drawings in which:

Fig. 1 is a diagrammatic, side elevational view of a drying machine embodying my invention, 1'

said machine being adapted for drying cloth or other sheet material.

Fig. 2 is an enlarged fragmentary elevational viewV of an endless conveyor which forms part of the drying machine and which embodies my invention.

Fig. 3 is an enlarged fragmentary view, partly in section and partly in elevation, taken on line I-2 of Fig. 1.

Fig. 4 is a fragmentary view looking in the direction of line 4 4 of Fig. 3.

Fig. 5 is a view similar to Fig. l, but illustrating the application of the invention to a machine adapted for drying sludge or other loose material.

Fig. 6 is a view, partly in elevation and partly in section, showing details of construction of the embodiment shown in Fig. 5.

Fig. 'I is an enlarged fragmentary view, partly in section and partly in elevation, taken on line 1-1 of Fig. 6.

Fig. 8 is a diagrammatic side elevational view of a track embodying my invention and on which the conveyors of Figs. l and 5 travel.

Fig. 9 is a fragmentary top plan view of another embodiment of the invention.

Fig. 10 is a section on line ill-I0 of Fig. 9.

Fig. 1l is a section on line ii-il of Figs. 9 and 10.

Fig. 12 is a section on line i2-I2 of Fig. 10.

In Figs. l and 5, there is shown a drying machine structure which includes a framework and insulated walls defining a drying chamber i0 for receiving the material to be dried. Below the drying chamber are heating coils Il, and adjacent the drying chamber are blowers I2 for drawing air from the drying chamber into contact with the heating coils and delivering the air back to the drying chamber. As shown, the air is delivered to the top of the drying chamber so that it travels downwardly through the material to be dried. The structure of the drying machine itself, the location, nature and arrangement of the heating coils, the blowers, etc., may be conventional and will, therefore, be neither shown nor described in detail. It is suiiicient to point out that, in carrying out my invention, neither the action of the blowers, the heat of the coils, nor the velocity of the air flow through the chamber need be adjusted or in any way interferred with. In other words, my invention will operate satisfactorily if all of the factors mentioned are kept constant, although it is to be understood that there is nothing in my invention which precludes the adjustment of the heat of the coils, the speed of the blowers, or the velocity of the air flow, if so desired.

The machine shown in Fig. 1 is adapted for drying a web I1, which is festooned in loops il on poles 20 (Fig. 2). In this machine, a suitable mechanism A is provided at the feed end of the machine for feeding the wet web onto the poles, and a suitable mechanism B is provided at the delivery end of the machine for withdrawing the dried web which is then wound on a take-up roll 2i. The mechanisms A and B include suitably connected driven and driving friction rolls and a source of power, but since such mechanisms are old in this and other arts, they are neither shown nor described in detail.

The embodiment of Fig. 5 is adapted for drying sludge or other loose material 22 and includes a hopper 2l for feeding the material to be dried onto trays 24 and a receptacle 25 for receiving the dried material. 'I'he trays are preferably provided with perforations 24m.

In both embodiments, the machine includes propelling means for moving the material to be dried through the drying chamber. As will be seen from a comparison of Figs. 1 and 5, the propelling means may be changed, according to the particular material to be dried in the machine, withoutdeparting from the scope of the inven- In both embodiments, the propelling means includes sprocket chains 21 which travel endlessly over idle sprocket wheels 28 and are driven by driving sprocket wheels 29, which are operatively connected to a source of power (not shown). 'Ihe sprocket chains 21 are formed of rigid elongated links 3|, one end of each link being connected to a spacer roller 32 and the other end thereof being connected to a supportingd roller 33, as will be clearly seen from Figs. 2 an 6.

In the embodiment of Fig. 1, the'supporting rollers 33 are mounted at the ends of the poles 20, as shown in Fig. 3, and in the embodiment 'l5 of Fig. 5, the supporting rollers 33 are provided with brackets 3l which support the trays 23, as shown in Figs. 6 and 7. f

In both embodiments, the endless conveyors travel over tracks which are best illustrated in Pig. 8. As shown, the tracks include horizontal end portions which are at the feed end of the drying chamber and extend thereintol a predetermined distance, intermediate sloping portions 36, also extending a predetermined distance inside the drying chamber and connected to the horizontal portions 35 by means of ramps 31, and end horizontal portions 39 extending from the sloping portions 36 to the delivery end of the machine. Above the ramps 31 and the track portions 36 and 39 are horizontal guide plates Il.

It will be noted that the plates l0 are parallel with the end horizontal track portions 33 so as to define therewith spaces having uniform height, but that the intermediate sloping track portions 36 coact with the corresponding portions of the plates to formspaces which flare or increase in height from the ramps 31 to the inner end of the horizontal track portions 39. It will also be noted that the driving sprocket wheels 23 are located near the junction of the track portions 36 and 36 so that, as the sprocket wheels 23 turn, they pull the sprocket chain links over the horizontal track portions 35 and push the chain links down the ramps 31, along the sloping track portions 36 and along the horizontal track portions 39 toward the delivery end of the machine. l

Because, to the left of the sprocket wheels 23, the chain links 3| are pulled, they move on the tracks 36 in extended, or horizontalend-to-end relation, as shown at the left-hand portion of Fig. 8. But, because, to the right of the sprocket wheels 29, the chain links are pushed down the ramps 31, and the links are, alternately, either substantially parallel, or at an angle, to the ramps 31, the chain progressively collapses after the fashion of a pentograph, with the alternate spacing rollers 32 riding on the sloping tracks 36 and the alternate supporting rollers 33 moving against the under side of the plates 40. Also, as the chain moves over the track portions 36, the links 3| progressively approach vertical position, as shown in the middle portion of Fig. 8. The extent to which the links 3| may approach the vertical is limited by the distance of the upper guide plates 4|) from the corresponding tracks 36 therebelow, it being understood that this distance should be a little less than the total distance be tween the bottoms of roller 32 and the tops of the rollers 30, as viewed in Fig. 2. The collapsing action of the chain begins at the end ofthe tracks 36 adjacent the ramps 31 and continues progressively until the rollers begin to ride on the tracks 39. During their travel over the horizontal tracks 39, the links 3| will maintain a fixed or constant relationship until they emerge at the delivery end of the machine. Y

In practice, the length of the tracks 36 inside the drying chamber is made just enough to permit satisfactory and eillclent surface drying consistent with the rate of movement of the conveyor on these tracks, the length of the sloping tracks 36 is such as to allow the material to be piled up or hunched up to the desired extent, and the straight portions 39 of the tracks occupy the rest of the length of the drying chamber sowas to aiord ample time for interior drying of the material and so as to increase the drying capacity of the machine by increasing the amount of material that may be housed within the dryamm ing chamber at any one time or during any given period of time.

Operation The material I1 is festooned in loops I3 on the moving poles 20,*just before they enter the drying chamber. Because the sprocket wheels 26 pull the sprocket chains along the straight tracks 36, the links 3| move in'a horizontal, endto-end relation, and the poles 2li are spaced apart a distance equal to the length of two of these links. The sprocket wheels 29 and the ramps 31 are placed within the drying chamber at a predetermined distance from the feed end thereof. so that the loops will travel in their maximum spaced condition for a predetermined length of time or through a predetermined distance.

This period of time (or this distance) is such as to permit the material in question to pass through the rst, or constant drying rate, stage with the loops at their maximum distance apart.

By this means, each loop is subjected to the drying action of heated air, the volume, velocity and heat content of which are such as to effect rapid and substantially uniform evaporation of moisture from the surface of the loop, thus making for increased productivity and preventing shad- As the first, or constant rate, surface drying stage comes to a close, thepoles approach and begin to travel on the sloping tracks 36, where the loops are progressively bunched together, thus placing two or more loops in the path of the stream of air previously directed against one loop. By this means, the number of loops per unit area is increased without the necessity of altering any of the other factors, including the temperature and velocity of the air, all of which can remain constant. The increase in the number of loops per unit area balances the heat requirement of the partly dried loops against the available heat, so as to maintain an optimum ratio between the constant available heat of the air and the gradually decreasing heat requirement of the material.

Also, since during the falling rate drying stage,I it takes longer to evaporate the interior moisture oi the material, the bunching up of the loops forces the hot air to penetrate the material and slows the lineal progress of the material through the drying chamber without, however, slowing down the rate at which the material is fed into or withdrawn from the machine.

When the loops clear the sloping tracks 36, they enter and travel over the horizontal tracks 39 for a predetermined distance during which the relation of the loops to each other remains constant. This stage is useful for curing, where such a step is desired, or for removal of all residual moisture, or both.

From the foregoing it will be seen that the dominant feature of the invention resides in first moving the poles or trays in spaced-apart condition, and then bunching the poles or trays together without changing the rate of movement ofthe material into or out of the machine and without altering the speed of the conveyor. By

this arrangement, the travel of the material 13 its over-all dimensions or the heat input.

' The operation o! the embodiment of Fig. 5 is identical with that of Fig. 1, except that the hopper 23 feeds the material 22 in relatively thin layers and the material travels in this condition as long as the rollers 33 carrying the trays 24 ride on the tracks 35. However, as the rollers 33 move onto the tracks 36 and 39, the trays 24 begin to overlap each other and the material begins to pile up in a relatively thicker layer, as shown at the right hand oi Fig. 8.

If desired, an agitator 50. which is only diagrammatically shown in Fig. 6, may be used for stirring the loose bulk material l22, especially, but not exclusively, during the third or curing stage.

When loose bulk material, such as particles ot sodium silicate, or alfalfa leaves, etc., is being dried, great shrinkage takes place which greatly reduces the bulk or volume. Therefore, if such material were to remain spread out relatively thinly as is necessary at the beginning, or the ilrst, constant rate drying stage, there will be considerable waste of capacity. Therefore, the overlapping Of the trays, as shown in Fig. 6, not only serves to adjust the heat requirement of the material to the available heat content of the air, but it also increases the capacity, and hence the productivity of the machine.

In Figs. 9 to 12, I show another embodiment by means of which the essential feature of my invention, namely, the bunching up of the loops or trays, as the case may be, can be carried out. In this construction, the spacer rollers 32 are omitted and the chain 21 is carried by the reduced end portions of the poles. The ends of the poles are provided with rollers 52 which ride on continuous straight tracks 53. As the chains are pulled by the sprocket wheels 29, the links 3| thereof are extended in end-to-end relation, as shown at the left-hand side of Figs. 9 and 10. As Ythe chains are pushed, as shown to the right of the sprocket wheels, the unsupported pivotal connections 5l of the chain links drop, and the links are collapsed into a l formation. As the chains progress to the right, the V formation gets tighter and tighter until, after a given distance, the rollers 52 and the corresponding poles will be closely spaced.

Ii it is desired to control the extent to which the poles (or trays) may be bunched, the links may be provided with holes 56 through which pins I1 may be inserted to serve as a stop or limit, as will be seen from Figs. 9 and l2. If a pin 51 is inserted in the hole nearest the pivotal connection of two adjacent links, the rollers will be considerably spaced apart, as shown in Fig. 10. If the pin is placed in the intermediate hole or in the hole nearest the rollers, the rollers can be hunched up together more closely. Obviously,

` other means of effecting this adjustment can be devised.

If desired, a top rail 58 can be used to guide and form a bearing for the rollers 52, as best shown in Figs. 10 and 11.

It will be seen that, in both embodiments of the conveyor, means is provided for propelling the poles or trays carrying the material in amplyspaced relationship during the rst or constant rate, surface drying stage, so as to balance the heat requirement against the available heat, for progressively bunching the poles or trays to maintain the balance between the decreasing heat requirement and the constant available heat and to maintain .the poles or trays in a constant-relation during a third stage, which could 8 be used for curing or for still further carrying on the drying operation.

From the foregoing it will be seen that I have devised an improved drying machine which, in eilect, and by means of an integrated and coacting structure, serves the purposes of two drying chambers, one for surface, or constant rate drying stage, and one for interior, or falling rate drying stage, and that transition from one stage to the other takes place automatically and gradually and in a single drying chamber.

It will also be seen that, while the rate at which the material is fed into, and withdrawn from, the machine, remains nxed at the most desirable or most efficient speed, the travel of the material through the drying chamber is considerably slowed down through a major portion oi the length of the machine. As above pointed out, this bunching of the material forces the air to penetrate the material and increases the capacity of the machine by permitting a greater number of poles or trays to be placed in a given space.

Above all, it will be noted that all of the foregoing objects are attained by the extremely simple and inexpensive means disclosed, namely, the provision oi a sprocket chain formed of rigid links, the provision of tracks on which rollers which carry the chains travel, and the provision and location of a sprocket wheel which pulls the chain over a portion of the tracks so as to space the poles or trays and which pushes the chain onto another portion of the tracks whereby the chain is collapsed to bring the poles or trays carried by said chain progressively closer without varying the rate at which the conveyor is fed into or enters into or emerges from the machine. It will also be noted that the track structure disclosed can be readily incorporated in any standard existing drying machine of the type shown, with very little, if any, alteration of the design or structure of such machine.

Finally, it is also pointed out that addition of the tracks and the rollers is relatively inexpensive, and that by adjusting the rate at which and the extent to which the poles or trays are bunched together, the operating characteristics of the machine may be varied without otherwise altering the structure thereof.

What I claim is:

1. In combination, a track including a rst rail extending horizontally, a second rail, sloping downwardly in a direction away from the adjacent end of said iirst rail, a ramp connecting the adjacent ends of said rst and second rails, a conveyor including spaced rollers adapted to ride on said track, links pivotally connected at their ends to said rollers, and propelling means disposed adjacent the junction of' said rst and second rails and arranged for pulling said conveyor over said rst rail whereby said links are extended horizontally, in end-to-end relation, and said rollers are spaced apart the length of one of said links, said propelling means being also arranged for pushing said conveyor down said ramp and over said second rail whereby the axes of said links progressively approach a line normal to the horizontal, whereby alternate rollers ride on said second rail in progressively closer relationship.

2. The structure recited in claim 1 together with a guide member disposed above said second rail, said guide member extending horizontally and being so spaced from said second rail that other alternate rollers ride against the under side oi' said guide member in progressively closer rela.

tionship, the maximum distance ci' any portion oi said guide member from any corresponding portion of said second rail being less than the total length of one link and the diameter of one of said rollers.

3. The structure recited in claim 1 in which said links are elongated and rigid and in which said propelling means is operated at a constant speed.

4. In combination, a track including a iirst rail extending horizontally, a second rail sloping downwardly in a direction away from the adjacent end of `said nrst rail, a ramp connecting the adjacent ends of said first and second rails, a third rail extending horizontally from the freev l end of said second rail as a continuation of said second rail, and a horizontally-extending guide member disposed above said second and third rails, said guide member defining with said second rail a space which iares progressively from said ramp toward said third rail, and said guide member dening with said third rail, a space of constant height, a conveyor including rollers adapted to ride on said track, links pivotally connected at their ends to said rollers, and propelling means adjacent the junction of said iirst and second rails and arranged iorpulling said conveyor over said first rail whereby said links are extended horizontally in end-to-end relation and the axes of said rollers are spaced apart the length of one of-said links, said propelling means being also arranged for pushing said conveyor down said ramp and over Said second and third rails, whereby, when said conveyor is moving over said second rail, said links progressively approach a position normal to the horizontal and alternate rollers ride on said second rail in progressively closer relationship, said links andsaid rollers remaining in a constant position while said conveyor is moving over said third rail.

5. I'he combinationl with a conveyor adapted to be propelled through a drying chamber and including spaced rollers and links pivotally connected at their ends to said rollers, of means for causing said conveyor to mover through different portions of said drying chamber at diierent rates of speed without varying the rate of speed at which said conveyor enters or leaves said dryillf,r chamber, said means including a iirst horizontal rail extending through a ilrst portion of said drying chamber, a ramp leading downwardly from an end oi' said ilrst rail, a second rail extending through a second portion of said drying chamber and sloping downwardly from the lower end of said ramp, a horizontal guide member above said second rail, constant speed propelling means for actuating said conveyor, said propelling means being located intermediate said nrst and second rails and arranged to pull saidl conveyor Aover said nrst rail with all of said rollers 60 Number riding on said ilrst rail and with said links extended horizontally and in end-to-end relation, said propelling means being also arranged to push said conveyor down said ramp, onto, and

over said second rail with alternate rollers riding e5 moves further along said second rail, whereby 7 0 any given point on said conveyor will move at a higher lineal rate of speed and a given portion of the conveyor will occupy more lineal space while the conveyor is moving over said firstl rail and traversing said first portion of said drying chamber than said point and said portion will, when said conveyor is moving over said second rail and traversing said second portion of said drying chamber.

6. The combination with a conveyor adapted to nbe propelled through a drying chamber and including spaced rollers and links pivotally connected at their ends to said rollers, of means for causing said conveyor to move through different portions o! said drying chamber at different rates of speed without varying the rate of speed at which said conveyor enters or leaves said drying chamber, said means including a iirst horizontal rail extending through a iirst portion of said drying chamber, a ramp leading downwardly from an end oi' said rst rail, a second rail extending through a second portion of said drying chamber and sloping downwardly from the lower end of said ramp, a third horizontal rail disposed in end-to-end relation to said second rail and extending from the lower end oi' said second rail through a third portion of said drying chamber, a horizontal guide member above Isaid second and third rails, constant speed propelling means for actuating said conveyor, said propelling means being located intermediate said iirst and second rails and arranged to pull said conveyor over said first rail with all of said rollers riding on said iirst rail and with said links extended horizontally and in end-to-end relation, said propelling means being also arranged to push said conveyor down said "ramp, onto, and over said second and third rails, with alternate rollers riding on said second and third rails and other alternate rollers moving against the under side oi said guide member, and with said links forming progressively larger angles with the horizontal as the conveyor moves further along said second rail, whereby any given -point on said conveyor will move at a higher lineal rate of speed and a given portion of the conveyor will occupy more lineal space while the conveyor is moving over said first rail and traversing said ilrst portion of said drying chamber than said point and said portion will, when said conveyor is moving over said second rail and traversing said second portion of said drying chamber.

RALPH C. PARKES.

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

UNITED STATES PATENTS Name Date 1,023,443 Seeburger Apr. 16, 19'12 1,518,580 Harris Dec. 9, 1924 1,557,368 Kershaw Oct. 13, 1925 1,557,422 Colbert Oct. 13, 1925 1,626,492 Youngson Apr. 26, 1927 1,769,546 Ritchey July 1, 1930 1,856,498 Miller May 3, 1932 2,174,241 Grotzinger Sept. 26, 1939 2,487,354 McNamara et al. Nov. 8, 1949

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