CA1045625A - Apparatus for mixing molding sand - Google Patents
Apparatus for mixing molding sandInfo
- Publication number
- CA1045625A CA1045625A CA246,213A CA246213A CA1045625A CA 1045625 A CA1045625 A CA 1045625A CA 246213 A CA246213 A CA 246213A CA 1045625 A CA1045625 A CA 1045625A
- Authority
- CA
- Canada
- Prior art keywords
- tub
- sand
- paddles
- shaft
- mixer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Abstract
Continuous Molding Sand Mixer Having Reverse Pitched Blades Abstract of the Disclosure A continuous molding sand mixer comprises an elongated tub having a head end, a tail end, an elongated shaft extending axially within the tub, an entry port at the head end of the tub and a discharge opening at the tail end of the tub. A series of paddles are mounted on the shaft sub-stantially equidistant therefrom and adjacent the tub wall, Power means are provided to rotate the shaft. Most of the paddles are forwardly pitched in one direction to advance sand along the tub from its head end toward its tail end and out said discharge opening when the shaft rotates. Some of said paddles are reversely pitched in the opposite direction and are disposed in the path of sand impelled by the forwardly pitched paddles to restrict sand flow through the tub. This controls sand retention time in the mixer and restricts premature discharge of the sand through the discharge opening.
Description
Pug mills have been previously used for mixing particulate material. An example appears in United States patent 3,677,523 of Nelson Hartley issued July 18, 1972, in which the pug mill treats rebound clay intended to be formed into bricks, pipe, etc. Heretofore, pug mills have not been successfully used to mix and blend green foundry sand.
Summary of the Invention In accordance with the present invention, a pug mill type of mixer is adapted by important changes in its structure to mix and blend green foundry sand. The mixer of the present invention is a continuous sand mixer as distinguished from a batch mixer. It has an elongated shaft extending axially within a tub. The tub has an entry port at its head end and a discharge opening at its tail end. A series of paddles are mounted on the shaft substantially equidistant from and adjacent to the tub wall. Power means are provided for rotating the shaft. Most of the paddles are forwardly pitched in one direction to advance sand along the tub from its head end toward its tail end and out said discharge opening when the shaft rotates. Some of the paddles are reversely pitched in the opposite direction and are disposed in the path of sand impelled by the forwardly pitched paddles to restrict sand flow through the tub. This controls retention time in the mixer and restricts premature discharge of the sand through the discharge opening. The paddles have blade and shank ~' 1(~45625 portions. At least the blade portions are disposed at an oblique angle to the tub axis. The blade portions have a greater circumferential extent than the shank portions. The aggregate circumferential extent of the blade portions almost fills the space around the periphery of the tub. However, there are substantial gaps between the shank portions of the paddles. The blade portions will sweep the bottom of the tub, but some of the sand in the vicinity of the shanks may be missed by the shanks and bypassed. Accordingly, the sand is thoroughly mixed notwithstanding the fact that the sand passes through the tub on a continuous basis.
In preferred embodiments, the paddles have shanks with integrally extending base plates curved to match the surface of the shaft to mechanically lock the paddles to the shaft and by which the pitch of the paddle to the tub axis is maintained.
In some embodiments, the tub wall is lined with a resilient material and the paddles are provided with resilient edges. Said resilient material and said resilient edges coact to inhibit sand encrustation of the wall.
In preferred embodiments, the power means rotates the shaft at such a speed that the sand is slapped and batted to cause it to bounce and fly in the tub and to break up clumps of agglomerated sand.
lQ45~;ZS
Other objects, features and advantages of the present i~vention will appear from the disclosure herein.
Description of the Drawings Fig. 1 is a fragmentary plan view of a mixer incorporating features of the present invention.
Fig. 2 is a cross section taken along the line 2--2 of Fig. 1.
Fig. 3 is a cross section taken along the line 3--3 of Fig. 1.
Fig. 4 is a transverse cross section taken through the tub of the mixer and showing the paddle disposition therein.
Fig. 5 is a fragmentary plan view through the open top of the mixer and sho~ing the paddle disposition.
Fig, 6 is a fragmentary cross section taken along the line 6--6 of Fig. 5.
Fig. 7 is a developed plan view of the paddle shaft and showing the preferred pattern of the mounting holes for the paddles.
Fig. 8 is a fragmentary perspective end view of the 2Q mixer with its top open and showing the paddle disposition.
Fig. 9 is a perspective view of a wiper blade.
Fig. 10 is a diagrammatic view showing the disposi-tion of certain paddles having reverse-pitch blades.
~045625 Description of the Preferred Embodiments Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structure. The scope of the invention is defined in the claims appended hereto.
The mixer comprises an elongated tub shell 10 which has its upper edges stiffened by frame members 11. Tub shell 10 is supported from a base (not shown). In a typical embodi-ment, tub 10 is twelve feet long and three feet wide. The tub shell 10 has horizontally spaced vertical side walls 12 extended arcuately downwardly to form a semi-cylincrical trough 13. Substantially on the axis of the trough 13,an ,~ 15 agitator shaft 14 is mounted on end bearing brackets 19.
` The shaft 14 is driven from one end by a motor 15 coupled through pulley 16, belt 17 and pulley wheel 18 to shaft end.
The shaft 14 carries a series of radially projecting paddles 21, the shape, disposition and relationship one to ` 20 another of which constitutes an important feature of the present invention. Each paddle comprises a flat shank 22 from which a base plate or saddle-shaped foot 23 extends transversely as shown in Fig. 6. As best shown in Fig. 4, the base plate or saddle 23 is curved to match the curvature of the shaft 14. The shaft 14 is provided with a pattern of taped holes 24, as shown in Fig. 7, to receive mounting bolts 25 by which the paddles are rigidly mounted on the shaft. The curve of the paddle foot 23 mechanically inter-locks the paddles on the shaft and precludes any twisting of the paddle once it is secured by bolt 25.
Each paddle 21 is provided at its end opposite foot 23 with an enlarged blade portion 26. As best shown in Figs. 4 and 8, when viewed from an end of the shaft 14, the blade portions 26 of eight paddles, each spaced 45 arcuately about the shaft 14,have an aggregate circumferential extent sufficient to almost fill the space around the periphery of the tub. This arrangement enSures full sweeping contact of the blades 26 with the wall 13 of the tub. However, for about three-quarters of the over-all radial extent of the paddles 21, the paddle shanks 22 are reduced in circumferential extent, as viewed in Figs. 4 and 8, by about forty per cent, thus leaving substantial circumferential gaps 27 between adjacent paddles. Accordingly, sand may be partially bypassed through the gaps 27 for better blending action of the sand and additives during operation of the mixer.
In the preferred embodiment, both the shank 22 and blade portion 26 of the paddles 21 are skewed or disposed at an oblique angle to the axis of rotation of the shaft 14.
In the disclosed embodiment, the skew angle is 12. Accord-ingly, rotation of the shaft 14 in the direction of the arrow ~45625 in Fig. 4 will cause the sand in the tub to be moved by the skewed blades26 and shanks 22 in the direction of arrow 31 in Figs. 1 and 5. Some varia~ion in the twelve degree angle is permissible, depending on specific conditions.
Sand and such conventional additives as sea coal, bentonite, water, etc., are added to the tub 10 through an open port 32 near the head end of tub 10 as shown in Fig. 1 and is moved in the direction of arrow 31 along the tub and exits therefrom at the tail end of the tub lO. In one embodi-ment of the invention the tail end of tub 10 has exit doors 33 which are shown in closed position in Figs. 1 and 3 but which may be opened as hereinafter explained.
Downstream from port 32 the top of tub 10 is covered by louvered doors 39 mounted on hinges 40 to frame member 11 and intermediate hinges 30 to each other so that doors 39 can be opened as shown in Fig. 3.
Near the head end wall 34 of the tub lO shaft 14 is desirably provided with a scraper wheel 35 which has inclined blades 36 which scrape sand and other encrustations off of the end wall 34.
In the embodiment having exit doors 33 at the tail end of tub 10, the shaft 14 may be provided with a discharge disk 37 which has pie-shaped openings 38 to control outflow of sand from tub 10 through the doors 33 when they are opened.
The size o~ the openings 38 may be changed for various sand ~456Z5 formulations and conditions. The purpose of the apertured disk 37 is to function as a control gate to restrain flow of sand through the tub 10. Only a limited amount of sand is permitted to flow through the ports 38, thus regulating the retention time of sand in the tub for proper blending and mixing treatment by the paddles, The inside wall of the tub 10 is desirably provided with a rubber, plastic or other tough resilient liner 41.
~oreover, the blades 26 are also desirably provided with similar resilient wiper blades 42. The blades 42 have curved edges matching the curvature of the arcuate bottom 13 of the tub to ensure close conformance therebetween. The fact that one or both of the tub wall liner 41 and the blade edge wiper strips 42 are fabricated of resilient material promotes dis-- 15 lodge of encrustations of sand, etc., from the wall and prevents buildup which would overload the motor 15 and other-wise impede and interfere with the mixing process.
The wiper blades 42 are adjustably and removably attached to the paddles 21 between the blade wall 26 of the paddle 21 and a clamping jaw 43 which is releasably attached to the blade wall 26 by bolts 44. Blade 26 has a laterally extending flange 45 and the jaw 43 has a complementary flange 46 which coacts with the flange 45 in holding the parts together.
1~45625 As the wiping blades 42 become worn they may be readjusted in the clamp 43 to ensure close conformance to the wall of the tub and to take up wear. Wiper blades 42 are slotted at 48 to fit around bolts 44 to permit such adjustment.
As best shown in Fig. 7, the shaft 14 is provided with a series of bolt holes 24 which mount the paddles 21 thereon. Fig. 7 is a developed view of the shaft 14, as ; though it were laid out flat. The holes 24 are arranged in groups of eight holes around the shaft 14, thus to produce the paddle arrangement shown in Fig. 4. The eight holes 24 are numbered successively 1--8, inclusive, in Fig. 7. The numbers start over for the next group of eight. Each suc-cessively numbered hole is axially spaced two inches from the ~ preceding numbered hole. The eight holes are arranged in two ', helices, side by side~ Holes, 1, 3, 5 and 7 are in one helix around the shaft and holes 2, 4, 6 and 8 are in the other helix. The holes in each helix are spaced on four-inch centers axially along the shaft. In each helix, successive paddles are arcuately spaced around the periphery of the sh~ft at 90 intervals. The paddles in one helix are offset 45 with respect to the paddles in the other helix. Accordingly, successive paddles in the two helices are arcuately displaced around the periphery of the shaft at 45 intervalsL
In operation, the shaft 14 is typically rotated at about 65 rpm. This is sufficient speed of rotation so that the skewed paddles impact against the sand in the tub to bat ~.~
1''~45625 and throw the sand forwardly in the direction of arrow 31 from one blade to the next at the periphery of the paddles and permit bypassing of some of the sand through the gaps 27 as shown in Fig. 4. The resistance offered bY the apertured disk 37, the weight and inertia of the sand, in combination with the forward thrust of the paddles produces a pressure condition on the sand which results in a superior mixing and blending of the sand with the additives and water. An ideally moldable sand results. Some increase or decrease in rpm is permissible, depending on specific conditionsO
The mixer of the present invention breaks up agglomerated sand clumps by slapping and batting the sand.
The sand is aerated and ventilated, thus removing heat which return sand has picked up in previous molding operations.
The extracted heat escapes through the louvered doors 39 under pressure of the paddles 21 which act as fan blades to blow air through and over the sand. Under the action of the ; ~ paddles, the sand bounces and flies about in the tub, thus resulting in a thoroughblending and mixing of all ingredients.
20 ~ The sand is typically retained in the mixer tub for about one and one-half minutes, after which it is usually completely blended and ready for transport to the molders' ; hoppers.
Discharge doors 33 are mounted on hinges 51 as shown 25 in Figs. 1 and 3. These doors have cut out portions 52 ~ 45625 around the shaft 14. During startup and time periods before the mixer is fully operative, the doors 33 are closed so that no sand can be discharged from the mixer. Doors 33 are operated by fluid cylinders 53 which have corresponding fixed ends pivotally mounted on a central fixed bracket 54 and corresponding free ends pivotally attached to crank brackets 55 secured to the doors 33. After startup, the doors can be opened by swinging them to their broken line positions shown in Fig. 1 and even farther, thus to permit discharge of sand from the mixer.
In another embodiment of the invention, the doors 33 and end disk 37 are omitted. In this embodiment the means to restrict sand flow through the tub to control sand retention time comprises a series of reverse pitch paddles.
Fig. 10 diagrammatically illustrates such reverse-pitch paddles at the discharge end of the shaft 14 in hole positions 1, 3, 5, 7. The paddles at positions 2, 4, 6 and 8 have the standard forward pitch. Moreover, along the remaining length of the shaft 14, every eighth paddle is desirably given a reverse pitch. For example, each paddle in the No. 1 hole position is given a reverse pitch. This arrangement prevents sand from being discharged too quickly from the tub. Most of the paddles impel the sand toward the discharge end of the mixer, but the reverse-pitch paddles act in reverse to slow and control the rate of flow. The primary resistance is at the 1¢1 456Z5 exit end of the tub, but the distribution of reverse-pitch paddles along a shaft throughout its length also restricts flow through the tub to control sand retention timeD
The precise number and arrangement of the reverse-pitch paddles is subject to some variation as variations inthe size of the mixer and the nature and character of the sand processed therein will influence the number and disposition of the reverse-pitch paddles. The aforedescribed arrangement is exemplary of mixers twelve feet long and three feet in diameter processing green foundry sand.
For many installations the embodiment utilizing reverse-pitch paddles is preferred over the embodiment utilizing the apertured disk 37 and doors 33, inasmuch as the reverse-pitch paddle arrangement is simplified and there are fewer parts subject to becoming clogged by encrusted sand.
Summary of the Invention In accordance with the present invention, a pug mill type of mixer is adapted by important changes in its structure to mix and blend green foundry sand. The mixer of the present invention is a continuous sand mixer as distinguished from a batch mixer. It has an elongated shaft extending axially within a tub. The tub has an entry port at its head end and a discharge opening at its tail end. A series of paddles are mounted on the shaft substantially equidistant from and adjacent to the tub wall. Power means are provided for rotating the shaft. Most of the paddles are forwardly pitched in one direction to advance sand along the tub from its head end toward its tail end and out said discharge opening when the shaft rotates. Some of the paddles are reversely pitched in the opposite direction and are disposed in the path of sand impelled by the forwardly pitched paddles to restrict sand flow through the tub. This controls retention time in the mixer and restricts premature discharge of the sand through the discharge opening. The paddles have blade and shank ~' 1(~45625 portions. At least the blade portions are disposed at an oblique angle to the tub axis. The blade portions have a greater circumferential extent than the shank portions. The aggregate circumferential extent of the blade portions almost fills the space around the periphery of the tub. However, there are substantial gaps between the shank portions of the paddles. The blade portions will sweep the bottom of the tub, but some of the sand in the vicinity of the shanks may be missed by the shanks and bypassed. Accordingly, the sand is thoroughly mixed notwithstanding the fact that the sand passes through the tub on a continuous basis.
In preferred embodiments, the paddles have shanks with integrally extending base plates curved to match the surface of the shaft to mechanically lock the paddles to the shaft and by which the pitch of the paddle to the tub axis is maintained.
In some embodiments, the tub wall is lined with a resilient material and the paddles are provided with resilient edges. Said resilient material and said resilient edges coact to inhibit sand encrustation of the wall.
In preferred embodiments, the power means rotates the shaft at such a speed that the sand is slapped and batted to cause it to bounce and fly in the tub and to break up clumps of agglomerated sand.
lQ45~;ZS
Other objects, features and advantages of the present i~vention will appear from the disclosure herein.
Description of the Drawings Fig. 1 is a fragmentary plan view of a mixer incorporating features of the present invention.
Fig. 2 is a cross section taken along the line 2--2 of Fig. 1.
Fig. 3 is a cross section taken along the line 3--3 of Fig. 1.
Fig. 4 is a transverse cross section taken through the tub of the mixer and showing the paddle disposition therein.
Fig. 5 is a fragmentary plan view through the open top of the mixer and sho~ing the paddle disposition.
Fig, 6 is a fragmentary cross section taken along the line 6--6 of Fig. 5.
Fig. 7 is a developed plan view of the paddle shaft and showing the preferred pattern of the mounting holes for the paddles.
Fig. 8 is a fragmentary perspective end view of the 2Q mixer with its top open and showing the paddle disposition.
Fig. 9 is a perspective view of a wiper blade.
Fig. 10 is a diagrammatic view showing the disposi-tion of certain paddles having reverse-pitch blades.
~045625 Description of the Preferred Embodiments Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structure. The scope of the invention is defined in the claims appended hereto.
The mixer comprises an elongated tub shell 10 which has its upper edges stiffened by frame members 11. Tub shell 10 is supported from a base (not shown). In a typical embodi-ment, tub 10 is twelve feet long and three feet wide. The tub shell 10 has horizontally spaced vertical side walls 12 extended arcuately downwardly to form a semi-cylincrical trough 13. Substantially on the axis of the trough 13,an ,~ 15 agitator shaft 14 is mounted on end bearing brackets 19.
` The shaft 14 is driven from one end by a motor 15 coupled through pulley 16, belt 17 and pulley wheel 18 to shaft end.
The shaft 14 carries a series of radially projecting paddles 21, the shape, disposition and relationship one to ` 20 another of which constitutes an important feature of the present invention. Each paddle comprises a flat shank 22 from which a base plate or saddle-shaped foot 23 extends transversely as shown in Fig. 6. As best shown in Fig. 4, the base plate or saddle 23 is curved to match the curvature of the shaft 14. The shaft 14 is provided with a pattern of taped holes 24, as shown in Fig. 7, to receive mounting bolts 25 by which the paddles are rigidly mounted on the shaft. The curve of the paddle foot 23 mechanically inter-locks the paddles on the shaft and precludes any twisting of the paddle once it is secured by bolt 25.
Each paddle 21 is provided at its end opposite foot 23 with an enlarged blade portion 26. As best shown in Figs. 4 and 8, when viewed from an end of the shaft 14, the blade portions 26 of eight paddles, each spaced 45 arcuately about the shaft 14,have an aggregate circumferential extent sufficient to almost fill the space around the periphery of the tub. This arrangement enSures full sweeping contact of the blades 26 with the wall 13 of the tub. However, for about three-quarters of the over-all radial extent of the paddles 21, the paddle shanks 22 are reduced in circumferential extent, as viewed in Figs. 4 and 8, by about forty per cent, thus leaving substantial circumferential gaps 27 between adjacent paddles. Accordingly, sand may be partially bypassed through the gaps 27 for better blending action of the sand and additives during operation of the mixer.
In the preferred embodiment, both the shank 22 and blade portion 26 of the paddles 21 are skewed or disposed at an oblique angle to the axis of rotation of the shaft 14.
In the disclosed embodiment, the skew angle is 12. Accord-ingly, rotation of the shaft 14 in the direction of the arrow ~45625 in Fig. 4 will cause the sand in the tub to be moved by the skewed blades26 and shanks 22 in the direction of arrow 31 in Figs. 1 and 5. Some varia~ion in the twelve degree angle is permissible, depending on specific conditions.
Sand and such conventional additives as sea coal, bentonite, water, etc., are added to the tub 10 through an open port 32 near the head end of tub 10 as shown in Fig. 1 and is moved in the direction of arrow 31 along the tub and exits therefrom at the tail end of the tub lO. In one embodi-ment of the invention the tail end of tub 10 has exit doors 33 which are shown in closed position in Figs. 1 and 3 but which may be opened as hereinafter explained.
Downstream from port 32 the top of tub 10 is covered by louvered doors 39 mounted on hinges 40 to frame member 11 and intermediate hinges 30 to each other so that doors 39 can be opened as shown in Fig. 3.
Near the head end wall 34 of the tub lO shaft 14 is desirably provided with a scraper wheel 35 which has inclined blades 36 which scrape sand and other encrustations off of the end wall 34.
In the embodiment having exit doors 33 at the tail end of tub 10, the shaft 14 may be provided with a discharge disk 37 which has pie-shaped openings 38 to control outflow of sand from tub 10 through the doors 33 when they are opened.
The size o~ the openings 38 may be changed for various sand ~456Z5 formulations and conditions. The purpose of the apertured disk 37 is to function as a control gate to restrain flow of sand through the tub 10. Only a limited amount of sand is permitted to flow through the ports 38, thus regulating the retention time of sand in the tub for proper blending and mixing treatment by the paddles, The inside wall of the tub 10 is desirably provided with a rubber, plastic or other tough resilient liner 41.
~oreover, the blades 26 are also desirably provided with similar resilient wiper blades 42. The blades 42 have curved edges matching the curvature of the arcuate bottom 13 of the tub to ensure close conformance therebetween. The fact that one or both of the tub wall liner 41 and the blade edge wiper strips 42 are fabricated of resilient material promotes dis-- 15 lodge of encrustations of sand, etc., from the wall and prevents buildup which would overload the motor 15 and other-wise impede and interfere with the mixing process.
The wiper blades 42 are adjustably and removably attached to the paddles 21 between the blade wall 26 of the paddle 21 and a clamping jaw 43 which is releasably attached to the blade wall 26 by bolts 44. Blade 26 has a laterally extending flange 45 and the jaw 43 has a complementary flange 46 which coacts with the flange 45 in holding the parts together.
1~45625 As the wiping blades 42 become worn they may be readjusted in the clamp 43 to ensure close conformance to the wall of the tub and to take up wear. Wiper blades 42 are slotted at 48 to fit around bolts 44 to permit such adjustment.
As best shown in Fig. 7, the shaft 14 is provided with a series of bolt holes 24 which mount the paddles 21 thereon. Fig. 7 is a developed view of the shaft 14, as ; though it were laid out flat. The holes 24 are arranged in groups of eight holes around the shaft 14, thus to produce the paddle arrangement shown in Fig. 4. The eight holes 24 are numbered successively 1--8, inclusive, in Fig. 7. The numbers start over for the next group of eight. Each suc-cessively numbered hole is axially spaced two inches from the ~ preceding numbered hole. The eight holes are arranged in two ', helices, side by side~ Holes, 1, 3, 5 and 7 are in one helix around the shaft and holes 2, 4, 6 and 8 are in the other helix. The holes in each helix are spaced on four-inch centers axially along the shaft. In each helix, successive paddles are arcuately spaced around the periphery of the sh~ft at 90 intervals. The paddles in one helix are offset 45 with respect to the paddles in the other helix. Accordingly, successive paddles in the two helices are arcuately displaced around the periphery of the shaft at 45 intervalsL
In operation, the shaft 14 is typically rotated at about 65 rpm. This is sufficient speed of rotation so that the skewed paddles impact against the sand in the tub to bat ~.~
1''~45625 and throw the sand forwardly in the direction of arrow 31 from one blade to the next at the periphery of the paddles and permit bypassing of some of the sand through the gaps 27 as shown in Fig. 4. The resistance offered bY the apertured disk 37, the weight and inertia of the sand, in combination with the forward thrust of the paddles produces a pressure condition on the sand which results in a superior mixing and blending of the sand with the additives and water. An ideally moldable sand results. Some increase or decrease in rpm is permissible, depending on specific conditionsO
The mixer of the present invention breaks up agglomerated sand clumps by slapping and batting the sand.
The sand is aerated and ventilated, thus removing heat which return sand has picked up in previous molding operations.
The extracted heat escapes through the louvered doors 39 under pressure of the paddles 21 which act as fan blades to blow air through and over the sand. Under the action of the ; ~ paddles, the sand bounces and flies about in the tub, thus resulting in a thoroughblending and mixing of all ingredients.
20 ~ The sand is typically retained in the mixer tub for about one and one-half minutes, after which it is usually completely blended and ready for transport to the molders' ; hoppers.
Discharge doors 33 are mounted on hinges 51 as shown 25 in Figs. 1 and 3. These doors have cut out portions 52 ~ 45625 around the shaft 14. During startup and time periods before the mixer is fully operative, the doors 33 are closed so that no sand can be discharged from the mixer. Doors 33 are operated by fluid cylinders 53 which have corresponding fixed ends pivotally mounted on a central fixed bracket 54 and corresponding free ends pivotally attached to crank brackets 55 secured to the doors 33. After startup, the doors can be opened by swinging them to their broken line positions shown in Fig. 1 and even farther, thus to permit discharge of sand from the mixer.
In another embodiment of the invention, the doors 33 and end disk 37 are omitted. In this embodiment the means to restrict sand flow through the tub to control sand retention time comprises a series of reverse pitch paddles.
Fig. 10 diagrammatically illustrates such reverse-pitch paddles at the discharge end of the shaft 14 in hole positions 1, 3, 5, 7. The paddles at positions 2, 4, 6 and 8 have the standard forward pitch. Moreover, along the remaining length of the shaft 14, every eighth paddle is desirably given a reverse pitch. For example, each paddle in the No. 1 hole position is given a reverse pitch. This arrangement prevents sand from being discharged too quickly from the tub. Most of the paddles impel the sand toward the discharge end of the mixer, but the reverse-pitch paddles act in reverse to slow and control the rate of flow. The primary resistance is at the 1¢1 456Z5 exit end of the tub, but the distribution of reverse-pitch paddles along a shaft throughout its length also restricts flow through the tub to control sand retention timeD
The precise number and arrangement of the reverse-pitch paddles is subject to some variation as variations inthe size of the mixer and the nature and character of the sand processed therein will influence the number and disposition of the reverse-pitch paddles. The aforedescribed arrangement is exemplary of mixers twelve feet long and three feet in diameter processing green foundry sand.
For many installations the embodiment utilizing reverse-pitch paddles is preferred over the embodiment utilizing the apertured disk 37 and doors 33, inasmuch as the reverse-pitch paddle arrangement is simplified and there are fewer parts subject to becoming clogged by encrusted sand.
Claims (6)
1. A continuous molding sand mixer comprising an elongated tub having a head end and a tail end, an elongated shaft extending axially within the tub, an entry port at the head end of the tub and a discharge opening at the tail end of the tub, a series of paddles mounted on the shaft substan-tially equidistant therefrom and adjacent the tub wall, power means for rotating the shaft, most of said paddies being for-wardly pitched in one direction to advance sand unidirectionally along the tub from its head end toward its tail end and out said discharge opening when the shaft rotates, some of said paddles being reversely pitched in the opposite direction and disposed in the path of sand impelled by the forwardly pitched paddles to restrict sand flow through the tub, thus to control sand retention time in the mixer and restrict premature dis-charge thereof through said discharge opening, said paddles having blade and shank portions, at least said blade portions being disposed at an oblique angle to the tub axis to advance sand along the tub when the shaft rotates, the blade portions of the paddles having a greater circumferential extent than the shank portions, the aggregate circumferential extent of said blade portions at least almost filling the space around the periphery of the tub when viewed in end elevation, there being substantial gaps between said shank portions of the paddles when viewed in end elevation, whereby the blade portions will substantially completely sweep the bottom of the tub, but some of the sand in the vicinity of the shanks may be missed by the shanks and be bypassed.
2. The mixer of claim 1 in which said reverse pitch paddles are primarily at the tail end of the tub.
3. The mixer of claim 2 in which some of said reverse pitch paddles are distributed along said tub.
4. The mixer of claim 1 in which the paddles have shanks with integrally extending base plates curved to match the surface of the shaft to mechanically lock the paddles to the shaft and by which the pitch of the paddle to the tub axis is maintained.
5. The mixer of claim 1 in which said tub wall is lined with a resilient material and said paddles are provided with resilient edges, said resilient material and said resilient edges coacting to inhibit sand encrustation of said wall.
6. The mixer of claim 1 in which said power means rotates the shaft at such a speed that the sand is slapped and batted to cause it to bounce and fly in the tub and to break up clumps of agglomerated sand.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA246,213A CA1045625A (en) | 1976-02-20 | 1976-02-20 | Apparatus for mixing molding sand |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA246,213A CA1045625A (en) | 1976-02-20 | 1976-02-20 | Apparatus for mixing molding sand |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1045625A true CA1045625A (en) | 1979-01-02 |
Family
ID=4105278
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA246,213A Expired CA1045625A (en) | 1976-02-20 | 1976-02-20 | Apparatus for mixing molding sand |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1045625A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4655701A (en) * | 1986-02-19 | 1987-04-07 | Fuji Paudal Kabushiki Kaisha | Granulating apparatus |
| US4660987A (en) * | 1986-02-12 | 1987-04-28 | Tci, Inc. | Blender rotor improvements |
-
1976
- 1976-02-20 CA CA246,213A patent/CA1045625A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4660987A (en) * | 1986-02-12 | 1987-04-28 | Tci, Inc. | Blender rotor improvements |
| US4655701A (en) * | 1986-02-19 | 1987-04-07 | Fuji Paudal Kabushiki Kaisha | Granulating apparatus |
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