US2028745A - Apparatus for bituminous mixing - Google Patents

Description

Jan. 28, 1936. w. M. HENDRICK ET A1. 2,028,745

APPARATUS FOR BITUMINOUS MIXING I Filed April 1, 1935 7 7'0 VHFOI? SUPPLY 5 :g-m arm/1 as aw:

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Patented Jan. 28, 1936 1 2,028,745

UNITED STATES PATENT OFFICE 2,028,745 APPARATUS FOR BITUMINOUS IWIXING Wallace M. Hendrick, Great Neck, and Gustave Loefiler, Jr., Flushing, N. Y.

Application April 1, 1933, Serial No. 663,872 9 Claims. (01. 94-43) This invention relates to bituminous mixing, being dipped into a greater quantity of binding and more specifically to methods and apparatus agent than required for its proper coating, and for mixing bituminous binding material with an thereafter drained. We have found, however, aggregate of pieces of solid matter. While no that the"dip system will accomplish the ulti- 5 limitation thereto isintended, the invention conmately desired object that of coating the aggre- 6 templates particularly the coating with a bitumigate with a uniform quantity of bitumen per unit nous binding agent of an aggregate of crushed piece area-only if various conditions prior to, stone, sand, gravel, slag, sawdust, cork or the during and following the application of the hindlike, as for the construction of tralfic bearing ing agent to the aggregate are properly estabsurfaces, playing areas and the like. Such coatlished and maintained, and our invention is di- 10 ing is at present carried on either by laying the rected to the establishment and maintenance of aggregate in final place and flowing thereon the these conditions.

bituminous binder, by mixing predetermined Accordingly it is a broad object of our invenquantities of the aggregate and binder either aption to provide improved methods and apparatus proximately in final position or in a mixing plant, for coating aggregate with bituminous material. or by dipping the aggregate in a bath of the It is another object of our invention to probinding agent followed by drainage of the aggrevide methods and apparatus for efiecting on aggate. These systems may be respectively desiggregate a bituminous coating improved in uninated as penetration, mix-in-place or plantformity of bitumen quantity per unit aggregate mix, and dip systems; and while our invention piece area, independent of variations in the size 20 is particularly adapted to employment in the last of the aggregate pieces.

mentioned of these systems, certain aspects there- It is a further object to provide improvements of are useful with any of them. particularly adapted to the dip system above- The invention is particularly suited for use with mentioned. binding agents in emulsion formi. e., wherein It is a still further object to provide means and the bitumen particles themselves are held in susmethods for establishing and maintaining suitpension in a liquid vehicle which separates there able conditions of aggregate and binding agent from under suitable conditions (such for example prior to, during and following the application to as exposure to air), leaving the binding agent in the aggregate of the binding agent.

' a hardened state (this separating action being Another object is the provision of an improved 30 commonly termed breaking). It will be underportable bituminous mixing plant. Allied and stood, however, that our invention is not restricted subdivisional objects will more fully appear from to such emulsion binding agents, but contemthe following description and the appended plates also other binding agents in which the claims.

bitumen is contained in a liquid vehicle, such for While the most fundamental aspects of our inexample as cut-back agentsi. e., bitumen parvention transcend the use of particular apparaticles dissolved in a volatile oil. tus, they may be most readily described in con- In the present practice of the penetration and nection with apparatus specifically designed for mix-in-place or plant-mix systems of coating their use, and which is also a part of our inven- 4 abovementioned it is customary to determine the tion. Such apparatus is shown in the accomamount of bitumen proper to be employed in the panying drawing, of which binding agent for a given quantity of aggregate Figure 1 is a view, partly elevation and partly in accordance with the aggregate volume or schematic, of a machine for coating aggregate weight and with the average size of the aggregate with bituminous material, and

particles. This is done in an efiort to base the Figure 2 is a cross-sectional view taken along bitumen quantity on the total aggregate particle the lines 22 of Figure 1, in which certain oparea. Such a method obviously fails, however, tional components also appear. to take into account the widely varying surface Reference being had to Figure 1, there will be areas of aggregate pieces which may be classified seen a hopper l into which the aggregate to v9 as of the same size by conventional standards be coated may be loaded. The sides of the hop- (usually screen tests), and requires continuous per may be made convergent toward the bottom, weighing or other apportioning of aggregate and and here may be provided a regulable gate 31 b'nding agent. In the dip system of coating an whereby the flow of aggregate from the hopper attempt is made more directly to base the bitumen may be controlled. This flow may take place onto quantity on the area of the aggregate, the latter an endless belt conveyor 3, at the sides of which "15 e'scapement through derstood of course that the 2 may be provided conventional skirt-boards 4 and which is driven, preferably at regulable speed, from any suitable source of motive power. The speed may be conveniently adjusted so that the aggregate is carried off at a rate less than that at which it tends to flowthrough the gate. As an example of driving means, and in a schematic manner only, we have shown a motor 5 driving master pulley 6 having sections of a variety of diameters, a multi-section pulley 1 on the conveyor 3, and a belt38 operable selectively over a variety of combinations of sections in pulleys 6 and I and thus providing a regulable speed drive for the conveyor. The function of the apparatus thus far described is to discharge the aggregate in a relatively continuous, regulable flow into the second portion of our apparatus; and it will be understood that there may be substituted for the hopper I and conveyor 3 any other suitable means for providing such a flow into this second portion, hereinafter described.

A very significant factor governing the amount of bitumen coating which will be acquired by each unit area of aggregate particle upon application thereto of the binding agent is the condition of the surface of each particle at the moment of such application in respect of cleanliness, of temperature, and most importantly of surface moisture per unit particle area. According to our invention the aggregate is pre-treated, or preconditioned, in a manner substantially uniform with respect to surface area, preferably immediately prece'eding the application thereto of the binding agent. An embodiment of this pre-conditioning is the immersion of the aggregate pieces in a suitable liquid followed by their drainage for a predetermined time. The second portion of our apparatus is designed for carrying out this and other embodiments of the pre-conditioning process.

This portion may comprise an inclined screw conveyor 8. This has been illustrated as including a trough 9 with closed ends 39, a cover ID, a shaft H, and a single continuous helicoid flight or vane I! carried by the shaft. It will be undesign of this conveyor may be considerably modified, it being intended to illustrate a device whereby the aggregate may be carried upwardly in a continuous or substantially continuous flow. Thus for example a screw conveyor having multiple helicoid flights, or single or multiple sectional flights, or a conveyor of the inclined drag type might be substituted for the one illustrated. Figure 2 illustrates a cross section of the conveyor 8, and therein will be seen apertures36 in the flight or vane l2 near the shaft II to aid in the drainage of liquid 'from the shaft and flight and aggregate being thereby moved. The usual slight separation of the periphery of the flight from the inside of trough 9 further aids this drainage. The shaft I I may be rotated in any suitable manner, preferably at regulable speed; and schematically we have shown a bevel, gear I3 carried by the shaft II and engaging a bevel gear l4 driven by multisection pulley l5, which in turn may be driven as through belt Hi from multi-section pulley 6, as inthe case of conveyor 3.

In the lower corner of the conveyor 8 formed by the trough 9 and the lower end member 39' depth bath, schemay be maintained a constant matically indicated as H, of the pre-conditioning liquid, as by its introduction in regulable flow through pipe 18 and valve l9 and its overflow or outlet valve 20. If desired scribed as super-saturating the degree of drainage provided means for spraying onto the aggregate at there may also be the pre-conditioning liquid a point in the conveyor above the bath H, for

purposes of the better removal of dirt or other foreign material from thesurface of .the aggregate pieces. Thus we have shown a pipe 2| leading a flow of pre-conditioning liquid regulated as by valve 22 to a spray system 23, veniently be internally carried by the cover Ill. The aggregate is discharged into the bottom of conveyor 8 and hence into the bath IT. The shaft II is being continuously rotated and the flight l2 both agitates the aggregate and carries it out of the bath I1 and up the incline formed by the trough 9, in a relatively uniform and continuous flow. During the travel of the aggregate after leaving the bath l1 drainage thereof is of course taking place; and both the relative uniformity of the flow and the agitation of the aggregate during the flow insure quite similar drainage for all the aggregate pieces. This similar drainage of the several pieces, both in the conveyor 8 and in the corresponding element in the third (or actual coating) portion of our apparatus hereinafter described, we conceive to be a very desirable feature. If the spraying system 23 be employed it will be understood that the eftime will-be reduced, but the substantial uniformity of the treatment of the several aggregate pieces will be essentially unimpaired. The actual degree of drainage and hence the surface moisture per unit area of the aggregate as it reaches the discharge tube 24 at the upper extremity of trough 9 may be regulated by adjustment of the speed at which the conveyor operates.

It will be obvious that the effect of our immersion and/or spraying of the aggregate in and/ or with pre-conditioning liquid may be deaggregate surface with such liquid, andthat a function of the subsequent drainage is the reduction of this excessive surface moisture.

When emulsion binding agents are employed water may very satisfactorily be employed as the pre-conditioning liquid. With cut-back" binding agents a satisfactory pre-conditioning liquid may be an oil or other liquid such as is employed as the vehicle of the binding agent itself. In other words in either case the pre-condltioning liquid may satisfactorily be similar to the vehicle of the binding agent. As a particularly desirable of a typical aggregate, such as may mention one which prothe aggregate pieces as discharged through tube 24, but without the presence of free liquid or drippings. obvious that we use the term surface moisture", and its special case of surface saturation, as denoting the degree of presence on the aggregate surface of the pre-ccnditioning liquid, whether or not this be water.

The discharge through tube-24 may take place into the third portlongof our apparatus. This may conveniently comprise another conveyor similar to a form available for conveyor 8, and

we have therefore shown a screw conveyor 8 with portions 9, 39', I0, ll, l2, l3, and M respectively analagous to the correspondingly numbered portions of conveyor 8. A multi-section pulley l5 and a belt I6 may for example supply motive power at regulable speed to the conveyor B. In the angular bottom thereof may be maintained a constant depth bath, schematically indicated as H, of

which may con the binding agent, as by the.

veyor 8, however, it is desirable to adjust the inflow, as by valve l9, so that the normal level of the path l1 may be maintained without appreciable outflow through valve Such overflow as may occur maybe salvaged in receptacle 25. A spraying system 23' similar to the system 23 on conveyor 8 may be provided in conveyor 8' if desired, as an optional substitute for or addition to the inlet pipe l8.

- The pre-conditioned aggregate being discharged into the bath I1 of binding agent and the shaft ll of conveyor 8 being continuously rotated, the flight I 2' both agitates the aggregate and carries it upwardly out of the bath as in the case of conveyor 8. Further as in that case substantial uniformity of drainage of the several aggregate pieces is obtained. The adjustment of the speed of operation of conveyor 8' will determine the condition of the coating on the aggregate as discharged through outlet 26 located at the upper extremity of the trough 9. The speed may therefore be established according to the condition of the coating desired for the work being performed-e. g., in the case of emulsion binding agents the adjustment of speed of conveyor 8' will determine the degreeto which breaking of the coating on the discharged aggregate has proceeded.

While the speeds of operation of the individual portions of our apparatus have been severally discussed, certain limitations on relative speeds between them should not be exceeded. Thus in the case of either of the screw conveyors 8 and below the absolute clogging limit, may tend to impair the uniformity of drainage in that conveyor. After determination of the speed of conveyor 8' as above outlined the speed of conveyor 8 may be adjusted in the light of this limitation; if too great a degree of drainage occur in conveyor 8 by reason of an enforcedly slow speed, the spray system 23 may be called on to reduce the effective drainage time. Upon adjustment of the speed of conveyor 8 the inflow thereto is readily regulated to an appropriate rate by adjustment of speed of belt conveyor 3, and finally the hopper gate 31 may be adjusted to a sufficiently open position to insure the desired flow onto the last mentioned conveyor.

The discharge of coated aggregate through the outlet 26 may if desired take place merely-into convenient receptacles. We have illustrated our entire apparatus, however, as a unit mounted on platform 50 which in turn is mounted on wheels 5|. The entire assemblage while in operation may therefore be moved along a surface which it is desired to cover with the coated aggregate, such as schematically indicated road surface 21. The discharge from outlet 26 may then take place directly onto this surface and be levelled by spreaders, such as 28 which are shown carried by the platform 50 and therefore moved integrally with the rest of the apparatus.

Our invention non-limitatively contemplates substantial constancy of the humidity of the atmosphere from which the aggregate is discharged into the binding agent, whereby the uniformity stancy of the humidity of the atmosphere in which the coated aggregate drains, whereby the uniformity of degree of breaking or hardening of the coating is improved. Looking toward the maintenance of this constant humidity in these two cases we have provided the conveyors 8 and 8' with covers l0 and i0 respectively, so that each conveyor then tends to be established by the evaporation (from bath I7 01- l'l' as the case may be and from the draining aggregate) taking place in the particular temperature prevailing within the conveyor.

pipe 34 and valve 35 leading into each of the conveyors 8 and 8' by which uniformly moist vapor may be introduced in regulable flow.

It is to be noted that if a constant, relatively high humidity be maintained in the conveyor 8 the degree of breaking or hardening of the coating of the aggregate as discharged will be relatively slight, which is a usually satisfactory condition; at the same time breaking or hardening of the binding agent which may tend to adhere to the interior parts of the conveyor will be minimized, aiding in the drainage of the binding agent from these parts and reducing the frequency with which cleaning thereof will be required. Asto conveyor 8, the maintenance of such a humidity will of course decrease the efiective drying of the aggregate during drainage.

Optional elements of our invention are the control of the temperature of the aggregate as introduced in the bath of binding agent, whereby the aggregate is still more uniformly pre-conditioned; the control of the temperature of the coating bath, whereby its viscosity is most uniformly maintained; and the control of the temperature of the aggregate while draining after the bathywhereby the most uniform degree of breaking" or hardening of its coating before final use is obtained. It may be noted that with a pre-conditioning liquid supply of constant temperature the first of these controls is inherently at least partially effected. ternative means of effecting these controls, however, we have shown in the cross-sectional Figure 2 a member 29 surrounding and in spaced relation to the trough 9 and forming a jacket 30 thereabout. top of the incline, may be introduced steam or other constant temperature fluid (air'or water of controlled temperature for example) as through pipe 3| and valve 32. Outlet valve 33, preferably located at the bottom of the incline, may carry off condensation and excess.

Such a jacket and fluid supply may be employed with either or both the conveyors 8 and/or 8. The employment thereof with conveyor 8 not only will serve to control the temperature of the aggregate as introduced into the coating bath, but will also make more flexible the control of surface moisture per un t area of the aggregate at this point. It will be understood that such temperature control with the conveyor 8', in the case either of emulsion or cut-back binding agents, will increase not only the uniformity of binding agent viscosity but also the uniformity of condition of the coating on the aggregate as discharged through outlet 26.

As further and/or al- Into this jacket, preferably near the l the same from said super-saturating Preferably in either'of these cases a moderate temperature is maintained by the control.

While we have indicated the functions of the various-controls contemplated by our invention and have suggested desirable adjustments thereof for use in particular cases, the wide variations in nature of aggregate, in types and characteristics of binding agents and in nature and thickness of coatings desired for particular purposes, make it necessary that the contrcis be adjusted in the light of all these circumstances as they may exist in a particular ease. It will be understood, however, that-upon determination of any desirable adjustments of drainage times (e. g., conveyor speeds), humidii-ies, temperatures, etc., for a particular coating, tins coating may be duplicated at any time by a duplication of those adjustments. Thus these various factors may be predetermined and particular coatings repeatedly duplicated, without the necessity of making allowances for outside temperatures and other atmospheric conditions as they may exist at the time of coating, and as they may have existed for a spaee of time prior thereto (with consequent effect on the surface characteristics of unconditioned aggregate).

While we have described and. illustrated our invention in terms of specific embodiments thereof, we do not intend any limitation thereby, but rather indicate by the following claims the intended scope of our invention.

We claim:-

1. In combination in a 'macnine for coating aggregate with a liquid vehicle bituminous binding agent: means for imparting a uniform surface moisture to the aggregate comprising aggregate surface super-saturating means, conveyor means for draining the aggregate while conveying means, and aggregate agitating means included in said draining means; and means for applying the binding agent to the surface of the aggregate, said draining means being connected directly with said applying means for the discharge thereinto of surface moist aggregate.

2. In combination in a machine for coating aggregate with a liquid vehicle bituminous binding agent: means for imparting a uniform surface moisture to the aggregate comprising aggregate surface super-saturating means, conveyor means for draining the aggregate while conveying the same from said super-saturating means, and aggregate agitating means included in said draining means; means for applying the binding agent to the surface of the aggregate, said draining means being connected directly with said applying means for the discharge thereinto of surface moist aggregate; and conveyor means for draining the aggregate while conveying the same from said applying means.

3. In combination in a machine for coating aggregate with a bituminous binding agent in emulsion form: means for imparting a uniform surface moisture to the aggregate comprising means for super-saturating the aggregate surface with water, conveyor means for draining the aggregate while conveying the same from said super-saturating means, and aggregate agitating means included insaid draining means; means for applying the binding agent to the surface of the aggregate; and aggregate discharging means leading directly into said applying means from a point in said draining means at which the aggregate is surface moist but devoid of free liquid and drippings.

4. In combination in a machine for coating aggregate with a emulsion form: means for imparting a uniform surface moisture to the aggregate comprising means for super-saturating the aggregate surface with water, conveyor means for draining the aggregate while conveying the same from said super-saturating means, and aggregate agitating means included in said draining means; means for applying the binding agent to the surface of the aggregate; eonveyor means for draining the aggregate while conveying the same from said applying means; and aggregate dischargingmeans leading directly into said applying means from a point said first-mentioned draining means at which the aggregate is surface moist but devoid of free liquid and drippings.

5. In combination in a machine for coating aggregate with a liquid vehicle bituminous bind= ing agent: means for imparting a uniform sur= I to the aggregate comprising an face nioisture inclined screw conveyor adapted to mc-ve aggre gate upwardly while agitating and draining the same and arranged to receive an infiew of aggregate at its lower extremity, and means included in a lower portion of said conveyor for super-saturating the aggregate surface; means for applying the binding agent to the surface of the aggregate; and discharging means leading directly from the upper extremity of said conveyor into said applying means for the discharge thereinto of surface moist aggregate.

6. In combination in a. machine for coating aggregate with a liquid vehicle bituminous binding agent: two inclined adapted to move aggregate upwardly while agitating and draining the same, means included bituminous binding agent in screw conveyors each in a lower portion of a first of said conveyors for super-saturating the aggregate surface, means included in a lower portion of the second said conveyor for applying the binding agent to the aggregate surface, means for introducing'aggregate into the lower extremity of said first conveyor, and aggregate discharging means leading directly into the lower extremity of said sec-end conveyor from an upper portion of said first eonveyer whereat the aggregate remains surface moist.

'7. A bituminous mixing plant comprising two inciined screw conveyors; means for maintaining a bath of a pre-conditioning liquid in the lower portion of a first of said conveyors; means for maintaining a bath of liquid vehicle bituminous binding agent in the lower portion ef the second of said conveyors; means fer introducing aggregate into the lower portion of said first conveyor; an outlet'for conducting aggregate from the upper portion of said first to the lower portion of said second conveyor; an c-utlet for discharging aggregate from the upper portion of said second conveyor; and nights forming parts of said conveyors respectively and adapted to move aggregate in each upwardly out of the respective said bath to the respective said outlet, while agitating the aggregate and permitting the drainage thereof.

8. A bituminous mixing plant according to claim '7 including a carriage supporting said conveyors and adapted to be moved along a surface to be covered with coated aggregate; and spreaders secured to said carriage and adapted to level an aggregate discharged by said discharging means.

9. In a machine for coating aggregate with a bituminous binding agent in emulsion farm: a

substantially enclosed inclined screw conveyor gate from an upper portion of said conveyor, adapted to move aggregate upwardly while agiand means for introducing moist vapor into said 6 veyor for applying the binding agent to the ag- WALLACE M. HENDRICK. gregate surface, means for discharging aggre- GUSTAVE LOEFFLER, JR.

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