US2495241A

US2495241A - Mixing apparatus

Info

Publication number: US2495241A
Application number: US625791A
Authority: US
Inventors: Eaby Le Roy
Original assignee: Armstrong Cork Co
Current assignee: Armstrong World Industries Inc
Priority date: 1945-10-31
Filing date: 1945-10-31
Publication date: 1950-01-24
Anticipated expiration: 1967-01-24

Description

Jan. 24, 195@ 7 LE F-QOY EABY 2,495,241

MIXING APPARATUS Filed Oct. 51, 1945 8 ShGtS-Sheet 1 v Fl.

lNVENTOR L G Foyfaby LE YROY EABY Jan. 24, 1950 MIXING APPARATUS 8 Sheets-Sheet 2 Filed Oct. 51, 1945 Rqyfaby Jan. 24, 1950 LE ROY EABY MIXING APPARATUS 8 Sheets-Sheet 3 Filed Oct. 51, 1945 A W M 0 5 WM Jan, 24, 1950 LE ROY EABY 2,495,241

MIXING APPARATUS Filed 001:. 31, 1945 8 Shee'ts-Sheet 5 Jan. 24,, 1950 Filed Oct. 31. 1945 LE ROY EABY MIXING APPARATUS 8 Sheets-Sheet 6 INVENTOR Jan. 24, 1950 Filed oct. 51, 1945 .XI LET LE ROY EABY MIXING APPARATUS 8 Sheets-Sheet 7 INVENTOR Lefiayfaby A M! MM- Jan. 24, 1950 LE ROY EABY 2,495,241

MIXING APPARATUS Z ay Patented Jan. 24, 1950 iiil'ifED STATES 22 Claims.

This invention relates .to apparatus for mixing plastic materials and, in particular, to mixing apparatus adapted to handle relatively heavy, :highly viscous mixes involving the application of a substantial amount .of power and developing high pressure in the mix.

Mixing apparatus of various types has long been known. .No ,mi-xer now available, however, has proved entirely satisfactory vfor handling certain classes of materials which are notoriously diiiicult to mix. Machines for handling asphalt- .tiie mixes, for examplahave usually been adapted from machines originally designed for other materials and the inherent limitations thereof have prevented the prooessingof asphalt-tile mix with the speed and efiiciency desired.

The apparatus used heretofore for heavy viscous mixes, such as that for making asphalt tile, have been subject to excessively high maintenance casts in regular operation and have re vquired periodic reconstruction. The resultof the operation of known machines, furthermore, has not been as good as desired from the-standpoint of uniformity of .dispersion of the various componentsof the mix, leaving out of consideration any question of efiiciency or the time required. In certain mixing operations, moreover, different types of mixing ,action are desired at different stages of the processing. In the case of asphalttile mix, for example, the components of the base mix must first be uniformly interspersed. When this has been accomplished the mottle color is added and the mixing is continued until the mottle color is irregularly distributed, but the mixing must be stopped before the mottle color becomes uniformly blended with the base mix.

Otherwise, the contrasting effect afforded by the mettle color would be lost. In other words, the base mix requires intensive mixing or mulling while the dispersion of the mottle color is best attained by a kneading action. Known mixers produce either a kneading action almost entirely or else amulling or intensive mixing without any substantial amount of kneading.

I have invented a novel mixing ap aratus T which overcomes the abovedefects of previously known mixers and is characterized by further novel features and advantages which willbe explained during the followingdetailed description of the invention. In a preferred embodiment, the

.i.'.e.. so that they o n i each other throu hout a portion of theircircumference. The chamber is preferably defined by spaced semi-cylindrical body casings and opposed reciprocable closures in the form of rams movable into and out of bridging position relative to the body casings. $paced side members define the ends of the ,mix- ,ing' chamber, the body casings extending between the side members and being secured thereto. .Shaftsdisposed coaxially with the cylindrical compartments are provided with stirrers or mixing blades of novel oonstructionadapted toeffect a mulling or intensive mixing as well as a kneading action.

The axesof the compartments and the stirrer shafts lie in a plane inclined to the horizontal and the rams reciprocate in guide boxes along a path normal to said plane. The upper ram has abreaker block extending into the space between the paths of the outermost portions of the stirrers. A charging opening leading into the chamber is uncovered on retraction of the upper ram. The contents of the mixing chamber fall freely therefrom on retraction of the upper ram through an opening in the guide box of the latter. Access openings are provided at several points to facilitate cleaning of the interior of the chamber which must be done' very thoroughly when changing colors. The lower body casing is also hingedly mounted on an upper spacer, further ,iacilitating the cleaning.

Aoomplete understanding of the invention may be had from the following detailed description in which additional novel features will be pointed out by reference to the accompanying drawings illustrating a preferred embodiment. Certain of the features disclosed herein, however, are the sole invention of Wendell W. Jones and are also disclosed and claimed in his copending application, Serial .No. 625,827, filed October 31, 1948 for Mixing apparatus.

In the drawings,

Figure 1 is an elevation of the apparatus;

Figure 2 is a side elevation taken from the left in Figure -l with parts in section;

spectively to Figures 4 and 5, showing sections 3 taken on line V'I-VI of Figure '7 and line VII--VII of Figure 3;

Figure 8 is a partial section taken through the chamber on the plane of line VIII-VIII of Figure 2 which contains the axes of the stirrer shafts;

Figure 9 is a side elevation of one of the stirrers;

Figure 10 is an end elevation thereof taken from the right of Figure 9; and

Figures 11 through are transverse sections taken through the stirrer along the planes designated by section lines correspondingly numbered in Roman numerals on Fig. 9.

Referrin now in detail to the drawings, the apparatus of my invention includes spaced parallel side members l8 and .II having feet I2 adapted to be bolted to a suitable foundation. Seats [3 are formed on the side plates for re- .ceiving and supporting thereon bearing pedestals l4 and I5. I Stirrer shafts l6 and I! are journaled in outboard roller bearings l8 and I9, respectively,

carried by the-pedestals l4 and i5. The shafts l6 and I1 are parallel and lie in a plane making an angle of about with the horizontal. The

The mixing chamber 22 is defined by spaced upper and lower semi-cylindrical body casings 23 and'24extending between the side members l0 and II and bolted thereto through flanges 25.

The remainder of the wall of the mixing chamber is constituted by an upper ram 28 and a lower ram 21, both of which are normally positioned as shown in solid lines in Figure 3 but are retractible to the positions shown in chain lines. The ram 26 is rectangular in section, as shown in Figure 4, and reciprocates in a guide box defined by a spacer 28 and a cooperating spacer extension 23a integral with the upper body casing 23. The spacer 2B and extension 23a are bolted to the side members In and H through marginalflanges. A charging spout 29 is formed at the lower end of the extension 23a.

The

body casings

23 and 24 have pipe coils 38 and 3| cast therein for the circulation of a heating or cooling medium. The coils terminate at terminal bosses-32, 33 and 34 which are tapped for the connection of supply and return pipes, hoses or the like. The terminal bosses on the casing 24 have locations slightly different from those on the casing 23 and are designated by the same reference numeral with the suifix a. By using two separate pipe coils for each casing, each coil extending around only half the circumference of the casing, it is possible to use pipe smaller than would otherwise be necessary to take care of steam condensation. It is desirable to keep the pipe size as small as possible to avoid weakenin the casings.

The upper ram 2B has a breaker block 260. on the inner end thereof projecting into the space between the paths of the tips of the wings of the stirrers 28 and2l to improve the mixing action thereof. These wings, to be further described later, force masses of the mix against the block 26a to divide them.

The ram 26 is reciprocated in its guide box by a hydraulic piston and cylinder 35. The inner end of the cylinder is secured to a plate 36 mounted on spaced bridging channels 31 extending between the side members l0 and I l and secured thereto by angle brackets 38. A piston rod 39 extends from the cylinder and is threaded into a central boss 40 on the upper side of the ram. A pipe coil 4| is cast in the ram and inlet and outlet connections therefor are provided by

pipes

42 and 43 threaded into the ram and slidable through holes in one of two plates 44 extending between the channels 3! on opposite sides of the cylinder 35. Terminal fittings 42a and 43a afford connections for flexible conduits such as hose.

The ram 26 has stop keys 45 which travel in slots 45a (see Figure 5) in the side members It! and H. The slots terminate at a point such as to arrest the inward movement of the ram in the position shown in solid lines in Figure 3. Shims 46 are secured to the inner ends of the lugs whereby the exact stopping point of the ram may be adjusted.

The lower body casing 24 is secured to a hinge bracket 47 by screws 41a extending through cooperating seating surfaces 48 and 49 on the plate and bracket. The bracket swings on a horizontal shaft 58 which passes through bearings 5i secured to the spacer 28 near the upper end thereof. When the bolts passing through the flange 25 of the casing 24 have been removed, the casing and bracket may be swung to the position shown in chain lines in Figure 3 by a fluid pressure cylinder-and-piston 52. The cylinder is trunnioned at 53 to the bracket and the piston rod is pivoted at 54 to the spacer 28.

It will ordinarily not be necessary to swing the casing 24 outwardly for routine inspection and maintenance. An opening is provided in the spacer 28 near the lower end for this purpose. This opening is normally closed by a cover plate 55 hinged to the spacer 28 at 5511.. The hinged mounting of the casing 24 is particularly advantageous for the purpose of thoroughly cleaning the interior of the apparatus when a change of color of the base mix is contemplated.

The guide box for the lower ram 2'! is defined by upper and lower spacers 56 and 5! extending between the side members l8 and I I, the spacers having flanges whereby they are bolted to the side members. The lower ram, like the upper, is rectangular, and has a filler block 58 on the inner end thereof. It also has a pipe coil cast therein provided with supply and return connections similar to those described for the ram 26. The ram 21 is actuated by a cylinder-andpiston 59 mounted in the same manner as cylinder 35. The lower ram also has guide and stop keys 68 on opposite sides thereof as shown in Figure 7. These lugs travel in slots 6! in the side members in and II. Shims 62 are positioned in the slots for the same purpose as the shims 46 of the upper ram. Openings 62a in the side members (see Figure 7) give access to shims 62.

It will be observed that the structure of the two rams is similar in respect to the guide keys except that the lugs of the lower ram serve to guide the latter and maintain it properly aligned in its guide box, in addition to limiting upward movement thereof. Thus the ram is maintained in proper relation to the

body casings

23, 24 and spacers 56 and 5'! even though it is out of engagement with all of them during a certain portion of its travel from normal position to retracted position.

The

rams

26 and 21 have peripheral sealing grooves 261) and 21b adjacent their inner ends.

Passages

23b and 230 in the body casing 23, communicate with said grooves permitting a fluid sealing medium such as grease to be delivered and into the bore 78 from a fitting 32.

arcane- 1 5 thereto when the rams have been moved inwardly to the positions shown in solid lines in Figure '3. The grease may be delivered by any convenient dispensing system usually including a pump, adrive therefor and suitable connections between the pump and the inlet passages.

The spacers 5G and El terminate short of the semi-cylindrical bod-

y casings

23 and 24. This provides a discharge opening -63 on the lower side and an access or inspection opening M on the upper side of the mixer. 'It will be apparent that,'because of the inclined position of the plane containing the axes of the shafts, the contents of the chamber 22 will fall practically straight down through the opening "B3 when the ram '21 is retracted to the chain-line position.

The breaker block 26a is secured to the ram 26 by longitudinal screws as and transverse screws 65a, Fig. 3, passing through an outwardly extending flange 66 on each side of the block. The filler block "53 is similarly secured to the ram '21.. Semi cylin'drical liners 6'! are'secured to the body casings 23 and 2 by screws 68 passing through outwardl extending flanges 69 (see Figure 8). The breaker and filler blocks and liners 6"! preferably have an abrasion-resistant surface "formed thereon.

The side members It and "i I are provided with removable end covers 1'0 and l! overlying the ends-of the chamber '22 and corresponding thereto in shape. The covers are secured to the side members by stud "bolts 72 and are providedonthe interior with removable liner plates 13 secured by screws "M '(see Figure 8). The removable end covers make possible the removal of the shafts and replacement of the stirrers without disturbing the side members or the body-casingsof the mixer. Stuffing boxes 75 are formed in the covers it and T! for closing the clearance between them and the shafts l6 and ll, each stuffing 'box being provided with "a gland 16.

Each of the shafts l6 and I! has an axial bore '18 extending thereinto from the end opposite the driving end. A pipe 19 extends through a stuffing box 89] secured to the end'of each shaft. A return pipe Bl extends through the pipe 19 Suitable connections (not shown) extend from the fittings 82 to a source of heating or cooling fluid. The fittings and pipes -19 and 81 remain stationary, 'of course, while the shafts and their stufiing boxesBll revolve.

The stirrers 29 and -2l are keyed to the shafts l6 and H and the latter are preferably driven at slightly different speeds in opposite directions (as indicated by the arrows in Figure 3) byj a suitable motor through a conventional pinion stand. Either the upper or lower shaft may be driven at the higher speed, preferably the lower one. As shown in Figures 9 through 20, each stirrer 20 comprises a body 83 having a bore 84 therethrough to admit the supporting shaft. Solid,

massive wings

85 and 86 elongated axially, extend generally radially in opposite directions from the body portion 83. The wings areof unequalaxial length andterminatein planes normal 'to the stirrer axis, the inner ends of "the -two wings lying substantially in a common plane.

The overall length of the stirrer, as shown in Figure 8, is but slightl less than the'axiallength of the chamber 22. The wings 85 and86 have a helical twist in the same direction longitudinally of the :blade, but the pitch of the twist of the wings is not the same. The angle of the :twist,

furthermore, is not constant but increases ;prow.

i6 "gress'ively from the outer end of :each wing toward the inner end thereof as shown in Figures l1 through 20. This improves the kneading action of theistirrers.

The two :stirrers are oppositely disposed on their supporting shafts, as shown in Figure 8. The corresponding wings of the two stirrers thus do not overlap each other. The leading surfaces 8-! and '88 of the Wings are convex and the convexity decreases from the outer ends of the stirrer toward the common plane between the two wings, at least for a portion of the axial length of the wings. The decreasing convexity of the leading surfaces of the wings is clearly shown in Figures 1Z1 through 20. As there :illustrat'ed, the convexity of the leading surface of wing '85 decreases from the plane on which the section of Figure '11 is taken, to that .on which the section of Figure 12 is taken and so on through Figure 16. correspondingly, the convexity of the leading surface of the wing '86 decreases between the plane on which the section of Figure .20 is taken and that on which the section of Figure 19 is taken and so on through Figures '18 and 157.

The minimum convexityof the longer wing is greater than that of the shorter wing. 'In other words, the maximum radius :of the leading surface of wing B5 is greater than that of the lead- .ing surf ace of the wing :86.

The extreme outer tips of the wings are substantially -flat throughout their length, as :shown at 189 =and190, .having a radius of curvature but slightly less than that of the casings 23 and .24. An intensive mixing or mulling action thus takes place between the .wing tips and the inner surface of the mixing chamber .22. The other portionsof the stirrer wings exert akneadingaction, working the contents of the chamber 22 back and forth between the upper slower .cyllindrical compartments thereof .as well as :axially thereof by reason of the helical twist of the wings.

The trailing "surfaces P94! and "9.2 of the wings "are substantially radial at least in their outer portions :and slope gradually therefrom to the body portion of the stirrer. This provides sharp corners 513 which afford immediate release for the material :being :mulled Lbetwteen the tips -89 and :90 :and the surrounding walls of the :chamher or the breaker block 26a.

it 'will be :appa-ren't from the foregoing that the invention provides .armixing apparatus 10f high efficiency compared to machines Eknown preyiously, from the standpoint of the power consumed, the :size of the charge, the time required 'for the mixing of the charge and the .degree of intimacy of dispersion obtained. "The apparatus is :thus particularly suited for processing mixes used in the manufacture :of asphalt the but .is also capable =o'if handling other .mixes such as those from which linoleum is made. The apparatus is characterized by easy and speedy :charging and discharging. Ready access to all parts of the apparatus is afforded :f'or inspection and cleaning. The apparatusrequires'but -little malntenance even though .the mixes it is intended :to handle are -quite abrasive. The wearing surfaces, :such :as the breaker and flller blocks, the liners K61, 13 are renewable, as well 'as the stirrer #blades themselves.

I'By disposing Zthe stirrer .shafts in a lane :at approximately 45 .to the horizontal, :the contents lot the mixing-chamber may :bedischarged in a istraightidroplthrough the opening 3 into a non- "veyor pr Ea receptacle resting on the :same floor amaze;

as the mixer itself. The lower ram serves to deflect the falling charge rearwardly. The breaker block 26, being on the upper ram, is entirely out of the way of the material being dischar ed. The filler block 58 on the lower ram occupies a space which tends to remain void in the operation of the mixer but does not interfere with the free discharge of the mixed material. The mixing action is not affected by arranging the breaker block on the upper ram because of the high pressure developed in the material during mixing as a result of the confinement of the charge in a space of fixed volume.

The upper ram carrying the breaker block against which the maximum mixing pressure is exerted is yieldably held in position by the pressure of the fluid in the cylinder 35. Should abnormal pressure be exerted against the breaker block, the ram 26 will yield sufiiciently against the pressure in the cylinder 35 to afford relief.

The retraction of the upper ram'preparatory to charging the mix into the chamber 22 affords extra space for accommodating the latter and the forward movement of the ram to its normal position after completion of the charging pushes the charge into the chamber. If desired, the bottom ram may also be retracted part way to provide increased space for the accommodation of the charge. For example, the ram 22 may be retracted to a position in which the block 58 closes the opening between the

casings

23 and 24 to provide additional capacity for the reception of the ingredients to be mixed. The ram should not be retracted below this position until the mix is to be discharged from the machine.

The hydraulic cylinder 59 may be provided with suitable controls for limiting retraction of the ram.

The upper ram 26 has a long skirt which permits the provision of an opening in the spacer 28 to give access to the interior of the chamber from above. This opening also permits the charging of large masses of material which cannot be fed through the spout 29. The opening 64 also permits access to the chamber from below for cleaning and inspection. 1

As previously mentioned, the removable end covers 10 permit the entire assembly of stirrers and supporting shafts to be withdrawn from the mixer after the shafts have been uncoupled from the drive mechanism, without completely dismantling the apparatus as is necessary in the case of mixers known heretofore.

The pipe coils cast in the body plates and rams permit the temperature of the mix to be controlled as desired during various stages of the mixing operation.

The removable wearing surfaces on the rams and semi-cylindrical body casings are secured through integral attaching flanges. This avoids the weakening of the blocks and liners which would result from holes extending directly through their exposed surfaces. The liners for the semi-cylindrical casings may be ground on the exterior for close contact with the plates themselves to assure good heat-transfer characteristics as well as adequate support. Creeping or wrinkling of the liners is prevented by making them in sections for the various portions of the chamber wall and with a substantial thickness. The liners, furthermore, may be removed without dismantling the entire machine. To remove the liner of the casing 24, it is only necessary to open the same with the hydraulic ram 52, and for removing the liner in the casing 23, it is only necessary to remove the attaching means which secure the casing to the side members. The breaker block 26a, being independent of the other liner members, may be replaced oftener than the latter since it is subject to the most wear.

The stirrer blades are of such construction as to produce a combined mulling and kneading action. This is of particular importance in processing asphalt-tile mixes. The intensive mixing or mulling which occurs between the tips of the stirrer wings and the walls of the chamber and breaker block. is highly effective in producing uniform dispersion of the components of the base mix.

.The kneading caused by the overlapping of cross currents produced by the helical twist and the unequal axial lengths of the wings is effective to produce the desired distribution of the mottle colorquickly so that it does not become blended in the base mix. This practice gives a characteristic graining distinguished from that obtained in the practice of adding the mottle color at the mixing mill after the base components have been mixed in a conventional mixer. The kneading takes place as the charge is thrown back and forth by the wings of the stir'rer as a result of the break or discontinuity between the wings at their adjacent ends. This also causes a shearing action which is desirable in the case of linoleum mixes for breaking up the lumps therein and, aided by the speed differential between the blades, prevents the setting up of a consistent repetitive motion of the miX. The massive character of the stirrer wings stiffens the supporting shafts and limits their deflection to values such that they may satisfactorily be journaled in roller bearings. The mulling action of the tips of the blade wings is such that the desired amount of heat is generated in most cases by friction in the mix, but the coils 30 and 3! permit the supply of additional heat from an external source, if desired, as well as the removal of excess heat when necessary.

Although I have illustrated and described herein but a preferred embodiment of my invention, it will be understood that changes in the construction and arrangement of parts disclosed may be made without deviating from the spirit of the invention or the scope of the appended claims.

I claim:

1. A mixer blade comprising a body portion having a pair of axially elongated, substantially oppositely extendin generally radial wings, each presenting a leading working surface which is convex for the greater portion, at least, of its axial length and has a helical twist longitudinally of the blade, the convexity of the portion of said working surface of each wing adjacent the leading edge thereof decreasing progressively for a portion, at least, of the axial length of each wing from the outer end thereof toward the inner end thereof where it adjoins the other wing.

2. A mixer blade comprising a body portion having a pair of axially elongated, substantially oppositely extending, generally radial wings of unequal length, each presenting a leading working surface which is convex for the greater portion, at least, of its axial length and has a helical twist longitudinally of the blade, the convexity of the portion of said working surface of each wing adjacent the leading edge thereof descreasing progressively for a portion, at least, of the axial length of each wing from the outer end thereof toward the inner end thereof where it adjoins the other wing.

3.- The apparatus defined by claim v1 charac- 9 terized by the extreme tips of said wings having a substantially flat portion extending circumferentially on a radius smaller than that of said compartment, and extending substantially the full length of the wings.

4. The apparatus defined by claim 2 characterized by the maximum radius of curvature of the longer wing being greater than that of the shorter wins.

5. A mixer blade comprising a body portion having a pair of axially elongated, substantially oppositely extending, generally radial wings, each wing presenting a leading working surface which is convex for the greater portion, at least, of its axial length and has a helical twist longitudinally of the blade, the angle of said twist increasing for a portion, at least, of the axial length of each wing from the outer end thereof toward the inner end thereof where it adjoins the other wing.

6, A mixer comprising a substantially closed mixing chamber consisting of two parallel substantially cylindrical compartments opening into each other at their adjacent sides, spaced casings comprising the sides of said compartments, a movable closure adapted to be moved into registry with the spaced casings to complete one side of said compartments, a breaker block attached to said closure and projecting downwardly into and between the compartments, a stirrer blade journaled axially in each of said compartments and adapted to operate in such manner that the leading surfaces of each blade rotate toward the breaker block, said breaker block forming the adjacent portions of the upper sides of said compartments and serving to divide masses of material carried upwardly against it by said blades, said compartments being provided with a discharge opening opposite said breaker block, and a movable closure for said opening.

'7. A mixer comprising a substantially closed mixing chamber including two parallel substantially cylindrical compartments opening into each other along their adjacent sides, said compartments having axes substantially parallel and horizontal and lying in a single plane inclined to the horizontal, spaced casings comprising the sides of said compartments, a movable closure adapted to be moved into registry with the edges of said spaced casings to complete one side of said compartments, and means for advancing and retracting said closure in a direction normal to said single plane.

8. A mixer comprising a substantially closed mixing chamber including two parallel substantially cylindrical compartments opening into each other along thev adjacent sides thereof and having substantially parallel horizontal axes lying, in a single plane inclined to the horizontal, a breaker block in the upper portion of said chamber and partially between said compartments, a mixing blade axially disposed in each of said compartments and adapted to operate in such manner that the leading surfaces of each blade rotate toward the breaker block thereby serving to divide masses of material carried against it by said blades, and a movable closure for said compartments adapted to be advanced and retracted in a direction normal to said single plane.

9. A mixer comprising a substantially closed mixing chamber consisting of two parallel substantially cylindrical, compartments opening into each other at their adjacent sides and having axes substantially parallel and horizontal and lying in a single plane inclined to the horizontal, a breaker block projecting. downwardly into and between the compartments, a. stirrer blade. journaled axially in each of said compartments and adapted tooperate in such manner that, the, working surfaces of each blade rotate toward the breaker block, said breaker block forming the adjacent portions of the upper sides of said. compartments and serving to divide masses of material carried upwardly against it by said blades, said compartments being provided with a discharge opening, and a movable closure for said opening.

10. A mixer comprising a substantially closed mixing chamber including twoparallel substantially cylindrical compartments opening into each other at their adjacent sides, the axes of said compartments being substantially parallel and horizontal and lying in a single plane inclined to the horizontal, a breaker block projecting downwardly into and between the compartments, a stirrer blade journaled, axially in each of said compartments and adapted to operate in such manner that the working surfaces thereof lead as the blade rotates. toward the breaker block, said breaker block forming the adjacent portions of the upper sides of said compartments and serving to divide masses of material carried upwardly against it, by said blades, said compartments being provided with a discharge opening opposite said breaker block, and a; movable closure for said discharge opening forming the adjacent portions of the lower sides of said compartments.

11. A mixer comprising a substantially closed mixing chamber including two parallel substantially cylindrical compartments opening into each other at their adjacent sides, spaced casings forming the outside of said compartments, guide members extending upwardly adjacent the upper sides of said compartments, a ram which slidably engages said guide members, a breaker block attached to the lower portion of said ram, means for advancing and retracting said ram and adapted to yieldably maintain said ram in advance posi-. tion in such manner that the breaker block projects downwardly into and between the compartments and constitutes a closure continuation of the inner upper surfaces thereof, a stirrer blade journaled axially in each of said compartments and adapted to operate in such manner that the working surfaces thereof lead as the blade rotates toward the breaker block, said compartments being provided with a discharge opening, and a movable closure for said opening.

12-. A mixer comprising a substantially closed mixing chamber including two parallel substantially cylindrical compartments opening into each other along their adjacent sides, spaced casings formingthe outsides of said compartments, movable closures substantially forming the remainder of the upper and lower sides of said compartments, a breaker block aflixed to the upper movable closure, blades positioned coaxially in said compartments and adapted to operate in such manner that their respective working surfaces lead during rotation toward said breaker block and. hinged means adapted to swing one of said spaced casings away from its related compartment to afford access to or discharge from said chamber.

13. A mixer comprising a substantially closed mixing chamber, said chamber having two parallel substantially cylindrical compartments open! ing into each other along their adjacent sides and having their axes substantially parallel and hori zontal and lying in a single plane inclined to the horizontal, a retractable ram adjacent the upper sides of said compartments and adapted to operate in a direction perpendicular to said single plane, a breaker block carried on the lower end of said ram and adapted when the ram is in advanced position to constitute the upper closure for said compartments, said breaker block projecting downwardly into and between said compartments, a movable closure substantially across the chamber from said breaker block and adapted to constitute the lower closure for said compartments, said breaker block and said movable closure having, when in closed position, inner surfaces continuous with the remainder of the inner surfaces of said compartments, means affording access to the interior of said ram and breaker block assembly, a stirrer blade coaxially positioned in each compartmentland adapted to rotate so that its working surfaces lead as it moves toward said breaker block, means for retracting said ram and breaker block to permit charging material into said compartments for mixing, and means for opening said movable closure to discharge the contents of said compartments. 7

14. A mixer comprising a substantially closed mixing chamber, said chamber having two parallel substantially cylindrical compartments opening into each other along their adjacent sides and having their axes substantially parallel and horizontal and lying in a single plane inclined to the horizontal, a retractable ram adjacent the upper sides of said compartments and adapted to operate in a direction perpendicular to said single plane, a breaker block carried on the lower end of said ram and adapted when the ram is in advanced position to constitute the upper closure for said compartments, said breaker block projecting downwardly into and between said compartments, a movable closure substantially across the chamber from said breaker block and adapted to constitute the lower closure for said compart ments, said breaker block and said movable 010- i closure to discharge the contents of said compartments.

15. A mixer comprising a substantially closed mixing chamber including opposed substantially semi-cylindrical casings, side'members disposed at the ends of said casings, closures for the openings between the said casings and side members and adapted to define thereby a pair of parallel substantially cylindrical compartments opening into each other along the adjacent sides thereof, said compartments having their axes in substantially horizontal spaced parallel relation, said side members having openings in alinement with the axes of said compartments, covers removably secured to said side members overlyin said openings, a stirrer blade on a shaft positioned coaxially in each compartment, and bearings to support said shafts, said bearings being spaced outwardly of and apart from the side members whereby said stirrer blades may be removed axially through the openings in said side members after removal of said covers secured thereto.

7 16. A mixer comprising a substantially closed mixing chamber including opposed substantially semi-cylindrical casings, side members disposed at the ends of said casings. closures for the upper and lower openings between said casings and the side members, said closures adapted to define thereby a pair of parallel substantially cylindrical compartments opening into each other along one side and having their axes in substantially horizontal spaced parallel relation, said side members having openings in alinement with the axes of said compartments, covers removably secured to said side members overlying said openings, a shaft positioned coaxially in each compartment and extending through said covers, a mixing blade on each shaft, a seal surrounding each shaft in the area of thepassage of the shaft through the'said covers and adapted to be attached to the said covers for sealing the clearance between said shafts and said covers, bearings for the support of each shaft spaced outwardly of and apart from said side members whereby said stirrer blades may be removed axially through one of the openings in said side members after removal of the cover secured thereto. 7

v 1'7. A mixer comprising a substantially closed mixing chamber including opposed substantially semi-cylindrical casings, side members disposed at the ends of said casings, upper and lower closure members disposed between said casings and said side members to complete the said chamber, stirrer blades disposed in said chamber coaxially with the axes of said casings, a shaft supporting each stirrer blade, journaling means for said shafts spaced outwardly of and apart from said side members, said side members having openings through which said'stirrer blades may be removed axially, removable covers for said openings and surrounding said shafts, and removable wearing surfaces in said chamber and on said covers.

18. A mixer comprising a substantially closed mixing chamber, said chamber having two parallel substantially cylindrical compartments opening into each other along their adjacent sides and having their axes substantially parallel and horizontal and lying in a single plane inclined to the horizontal, substantially semi-cylindrical casings in spaced relationship forming the sides of said compartments, side members disposed at the ends of said compartments and having openings therein in registry with said compartments, a retractable ram adjacent the upper sides of said compartments and adapted to operate in a direction perpendicular to said single plane, a breaker block carried on the lower end of the said ram and adapted when the ram is in advanced position to constitute the upper closure for said compartments between said casings and said side members, said breaker block projecting downwardly into and between said compartments, a movable closure substantially across the chamber from said breaker block and adapted to constitute the lower closure for said compartments between said casings and said side members, said breaker block and said movable closure having, when in closed position, inner surfaces continuous with the remainder of the inner surfaces of said casings to form the inner surfaces of said compartments, a stirrer blade coaxially positioned in each compartment and adapted to rotate so that its working surfaces lead as it moves toward said breaker block, a supporting shaft for each stirrer blade, removable covers for said openings in said side members through which said shafts extend, journaling means for said shafts independent of and spaced away from said side members and covers, means for swinging one of said casings a limited distance'from ening into each other along their adjacent sides and having their axes substantially parallel and horizontal and lying'in a single plane inclined to the horizontal, substantially semi-cylindrical casings in spaced relationship forming the sides of said compartments, side members disposed at the ends of said compartments and having openings therein in registry with said compartments, a retractable ram adjacent the upper sides of said compartments and adapted to operate in a direction perpendicular to said single plane, a breaker block carried on the lower end of the said ram and adapted when the ram is in advanced position to constitute the upper closure for said compartments between said casings and said side members, said breaker block projecting downwardly into and between said compartments, a movable closure substantially across the chamber from said breaker block and adapted to constitute the lower closure for said compartments, between said casings and said side members, said breaker block and said movable closure having, when in closed position, inner surfaces continuone with the remainder of the inner surfaces of said casings to form the inner surfaces of said compartments, adjustable means for limiting the 2 travel of the said breaker block and movable closure upon closure to insure registry of the inner surfaces thereof with the inner surfaces of said compartments, a stirrer blade coaxially positioned in each compartment and adapted to rotate so that its working surfaces lead as it moves toward said breaker block, a supporting shaft for each stirrer blade, removable covers for said openings in said side members through which said shafts extend, journaling means for said shafts independent of and spaced away from said side members and covers, means for swinging one of said casings a limited distance from said compartments to open said compartments,

means for retracting said ram and breaker block 3/ to permit charging material into said compartments for mixing, and means for opening said movable closure to discharge the contents of said compartments.

20. A mixer comprising a substantially closed mixing chamber having two parallel substantially cylindrical compartments opening into each other along their adjacent sides, a breaker block positioned in the upper portion of said chamber and partially between said compartments, said compartments being provided with a discharge opening opposite said breaker block, a movable closure for said opening, and a mixing blade positioned axially in each of said compartments and adapted to operate in such manner that a working surface of each blade leads during the rotation of such blade toward the breaker block, said working surface being convex for the greater portion, at least, of its axial length and having 14 a helical twist longitudinally of the blade, the convexity of the portion of said working surface of each wing adjacent the leading edge thereof decreasing progressively for a portion, at least, of the axial length of eachwing from the outer end thereof toward the inner end thereof where it adjoins the other wing.

21. A mixer comprising a substantially closed mixing chamber having two parallel substantially cylindrical compartments opening into each other along their adjacent sides, a breaker block positioned in the upper portion of said chamber between said compartments, said compartments being provided with a discharge opening opposite said breaker block, a movable closure for said opening, and a mixing blade positioned axially in each of said compartments and adapted to operate in such manner that a working surface of each blade leads during the rotation of such blade toward the breaker block, said working surface being convex for the greater portion, at least, of its axial length and having a helical twist longitudinally of the blade, the convexity of the portion of said working surface of each wing adjacent the leading edge thereof decreasing progressively and the angle of twist of each wing increasing, such decrease in convexity and increase in angle of twist extending for a portion, at least, of the axial length of each wing from the outer end thereof toward the inner end thereof where it adjoins the other wing.

22. A mixing blade comprising a body portion having a pair of axially elongated, substantially oppositely extending, generally radial wings. each wing presenting a leading working surface which is convex for the greater portion, at least, of its axial length and has a helical twist longitudinally of the blade, the convexity of the portion of said working surface of each wing adjacent the leading edge thereof decreasing progressively and the angle of twist of each wing increasing progressively, such decrease in convexity and increase in angle of twist extending for a portion, at least, of the axial length of each wing from the outer end thereof toward the inner end thereof where it adjoins the other wing.

LE ROY EABY.

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

UNITED STATES PATENTS Number Name Date 1,260,684 Kempter Mar. 26, 1918 1,355,885 Bowen et al Oct. 19, 1920 1,623,159 Bowen et al Apr. 5, 1927 1,703,211 Schmierer Feb. 26, 1929 1,775,721 Hopkins Sept. 16, 1930 1,977,052 Garbutt Oct. 16, 1934 2,027,185 Loomis Jan. 7, 1936 2,215,976 Robinson 4. Sept. 24, 1940 2,351,706 Robinson June 20, 1944 FOREIGN PATENTS Number Country Date 253,058 Great Britain June 10, 1926 552,515 Great Britain Apr. 12, 1943 Certificate of Correction Patent No. 2,495,241 January 24, 1950 LE ROY EABY It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 20, for the word casts read costs; column 2, line 23, for upper reed lower; line 39, for October 31, 1948 read October 31, 1.945; column 8, line 70, for descreasing read decreasing;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 9th day of May, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Paten'ta.