SWEETING ADAM KEITH (ZA)
GRACE DARREN LESLIE (ZA)
| US3738583A | 1973-06-12 | |||
| DE3224680A1 | 1984-01-12 | |||
| EP0407013A1 | 1991-01-09 |
| CLAIMS: 1 . A direct drive mixing device, which includes: a mixer frame; a motor assembly positioned in a lower part of the mixer frame, the motor assembly includes a drive motor and a drive shaft, the drive shaft having a lower section which is coupled to the drive motor and an upper section which extends upwardly away from the drive motor; a bowl for holding material to be mixed, the bowl seated inside the mixer frame above the drive motor, the bowl includes an opening through which the upper section of the drive shaft extends; and at least one mixing member located inside the bowl and attached to the upper section of the drive shaft, the at least one mixing member operable to rotate inside the bowl. 2. The direct drive mixing device as claimed in claim 1 , which includes a bearing hub arrangement through which the drive shaft extends from the drive motor towards the bowl, the bearing hub arrangement formed to enclose the drive shaft and to fit between the bowl and the drive motor. 3. The direct drive mixing device as claimed in claim 2, which includes a bearing arrangement seated inside the bearing hub arrangement, the bearing arrangement in the form of at least one bearing positioned around the drive shaft. 4. The direct drive mixing device as claimed in claim 1 , which includes a mechanical seal positioned between the bowl and the motor assembly. 5. The direct drive mixing device as claimed in claim 4, in which the mechanical seal is in the form of a cartridge seal positioned at an opening at the bowl where the drive shaft extends into the bowl, the cartridge seal includes a rotating inner section which is secured to the drive shaft allowing the rotating inner section to rotate simultaneously with the drive shaft and a non-rotating outer section secured in the opening of the bowl. 6. The direct drive mixing device as claimed in claim 5, which includes a seal lubrication system to provide a constant flow of lubricant to the cartridge seal in order to create a thin film of lubricant between a face of the rotating inner section and a face of the non-rotating outer section of the cartridge seal. 7. The direct drive mixing device as claimed in claim 6, in which the seal lubrication system includes a pump and a lubricant storage tank which is positioned inside the mixer frame with a feedline from the lubricant storage tank to the cartridge seal. 8. The direct drive mixing device as claimed in claim 1 , in which drive motor is in the form of a bi-directional torque motor operable to drive the driveshaft in either a clockwise or anticlockwise direction. 9. The direct drive mixing device as claimed in claim 1 , in which the at least one mixing member is in the form a mixing blade which extends from the drive shaft. 10. The direct drive mixing device as claimed in claim 1 , in which the at least one mixing member is in the form of a mixing assembly which includes a circular disk shaped and dimensioned to fit inside a lower portion of the bowl, the cylindrical disk attached to the drive shaft to allow the cylindrical disk to rotate coincidently with the drive shaft. 1 1 . The direct drive mixing device as claimed in claim 10, in which the mixing assembly includes a plurality of mixing and impact blades which extends the cylindrical disk, such that in use the rotation of the drive shaft will induce rotation of the mixing and impact blades. 12. The direct drive mixing device as claimed in claim 1 1 , in which the mixing assembly includes at least one scraping member secured to an underside of the circular disk. 13. The direct drive mixing device as claimed in claim 1 , in which the direct drive mixing device may include an encoder in the form of an incremental angle encoder positioned proximate the drive shaft and connected to the drive motor, the incremental angle encoder operable to switch off the motor if the direction of rotation of the drive shaft changes. 14. The direct drive mixing device as claimed in claim 1 , in which the motor assembly includes cooling means in the form of a water-cooled system which is defined by a jacketed compartment placed around the motor with a pump operable to pump cooled water from a water cooler through the jacketed compartment of the motor thereby cooling the motor. 15. The direct drive mixing device as claimed in claim 1 , in which the mixer frame is in the form of a tilt frame in which the motor assembly and bowl are seated and a stationary support frame to which the tilt frame is connected in a raised position above the ground. 16. The direct drive mixing device as claimed in claim 15, in which the tilt frame includes cylindrical supporting arms which extend from at least two sides of the frame, the cylindrical supporting arms extending through a bearing assembly located in the stationary support frame and connected to a second motor assembly in the form of a gear motor arrangement operable to tilt the tilt frame relative the stationary support frame. 17. The direct drive mixing device as claimed in claim 1 , which includes a lid assembly comprising a lid support to which a lid is rotatably secured, the lid shaped and dimensioned to match the shape of an open end of the bowl with a plurality of flanges extending parallel from the disk, the flanges shaped to be receivable by corresponding holding latches located around the periphery of the open end of the bowl. 18. The direct drive mixing device as claimed in claim 17, in which the lid assembly includes a vertical movement mechanism which is secured at one to the lid support and the other end to the support frame, the vertical movement mechanism is in the form of at least one actuator which is configured to move the lid support frame in a direction transversely away and towards the open end of the bowl thereby defining an open and closed configuration. 19. The direct drive mixing device as claimed in claim 17, in which the lid assembly includes a rotational movement mechanism in the form of a rotary motor which is housed inside the lid support, the rotary motor connected to the lid via a transfer shaft allowing the rotary motor to rotate the lid in a clockwise or anti-clockwise direction such that the four holding latches can be selectively engaged and disengaged by the four flanges defining a locked condition and unlocked condition respectively. 20. A direct drive mixing device as claimed in claim 1 , substantially as herein described and illustrated. |
FIELD OF THE INVENTION
This invention relates to a mixing device. In particular the invention relates to a direct drive mixing device.
BACKGROUND INFORMATION
A mixing device is a mechanical device that can be used in a wide range of industries. Current mixing devices utilise a drive mechanism to rotate a set of beaters in a bowl containing a heterogeneous mixture of a powdered substance and a fluid with the intent of creating a more homogeneous mixture.
The drive mechanism of current mixing devices is in the form of an indirect drive mechanism which includes either a gear or belt drive mechanism. The drive mechanism further includes a motor which is coupled to a mixing shaft, positioned inside the mixing bowl, through the gear or belt drive mechanism thereby allowing the motor to drive the mixing shaft through the gear or belt drive mechanism.
One disadvantage of these mixing devices which implement a belt drive mechanism is the fact that belt slip or insufficient grip between the motor and the belt may occur which reduces the velocity ratio of the mixing device which results in a decrease in the efficiency of the mixing device.
Another disadvantage of current mixing devices which implement an indirect drive system is that mechanical losses may occur between the motor and the mixing shaft which results in inherent power losses which further reduce the efficiently of the mixing device.
The inventor is aware of the problems in current mixing devices. These problems include inherent power losses and reduced efficiency as a result of the mechanical losses and belt slip due to an indirectly driven mixing shaft. The current invention aims to provide a solution to these problems.
SUMMARY OF THE INVENTION
Broadly according to a first aspect of the invention there is provided a direct drive mixing device, which includes:
a mixer frame;
a motor assembly positioned in a lower part of the mixer frame, the motor assembly includes a drive motor and a drive shaft, the drive shaft having a lower section which is coupled to the drive motor and an upper section which extends upwardly away from the drive motor;
a bowl for holding material to be mixed, the bowl seated inside the mixer frame above the drive motor, the bowl includes an opening through which the upper section of the drive shaft extends into the bowl; and
at least one mixing member located inside the bowl and attached to the upper section of the drive shaft, the at least one mixing member operable to rotate inside the bowl.
The mixing device may include a bearing hub arrangement through which the drive shaft extends. The bearing hub arrangement may be in the form of a closure dimensioned to fit around the drive shaft and to fit between the bowl and the motor assembly.
The bearing hub may further include a bearing arrangement, seated inside the closure, which in use maintains the alignment of the drive shaft. The bearing arrangement may include at least one bearing in the form of a deep groove ball bearing, needle roller bearing, tapered roller bearing, or the like. In a preferred embodiment of the invention, the bearing arrangement may include two spherical roller bearings positioned proximate one another around the drive shaft.
The mixing device may further include a seal which is positioned between the bowl and the motor assembly. The seal may be in the form of a mechanical seal, more specific the seal may be in the form of a single or double cartridge seal. The seal may be configured to be positioned around the drive shaft at the opening of the bowl in order to seal the opening between the drive shaft and the bowl opening. The cartridge seal may include a rotating inner section which is secured to the drive shaft allowing the rotating inner section to rotate coincidently with the drive shaft and a non-rotating outer section secured in the opening of the bowl.
The mixing device may further include a seal lubrication system. The seal lubrication system may provide a constant flow of a lubricant to the seal in order to create a thin film of the lubricant between a face of the rotating inner section and a face of the non-rotating outer section of the cartridge seal. Advantageously, this thin film of lubricant may allow the cartridge seal to remain lubricated and prevent a run dry between the two faces during operation thereby prolonging the operational life of the seal. Further, the seal lubrication system may have an increased internal pressure relative to the pressure inside the missing bowl to prevent any ingress of material and/or fluid into the seal.
The lubrication system may include a pump which is positioned at close proximity to the mixer or inside the mixer frame with a feedline to the cartridge seal. The pump may be operable to pump the lubricant from a storage tank towards the cartridge seal.
In one embodiment of the invention, the drive motor may be in the form of an electric motor, more specifically the drive motor may be in the form of a torque motor. The torque motor may be bi-directional and operable to run either in a clockwise or anticlockwise direction.
In one embodiment of the invention the at least one mixing member may be in the form of a mixing blade which extends from the drive shaft. In another embodiment the mixing device may include a plurality of mixing blades.
In a preferred embodiment of the invention the at least one mixing member may be in the form of a mixing assembly which includes a circular disk-shaped and dimensioned to fit inside a lower portion of the bowl. The cylindrical disk may be attached to the drive shaft by means of shrink fitting, welding or the like. In a preferred embodiment of the invention, the cylindrical disk may include an integral bush into which an upper end of the drive shaft is receivable. The drive shaft may be secured to the bush of the cylindrical disk with a key which fits in an indentation in both the drive shaft and the bush. More specifically the key may fit in a keyway located in the bush and in a keyseat in the shaft to allow the disk to rotate coincidently with the shaft.
The mixing assembly may further include a plurality of mixing and impact blades which extends transversely from an upper face of the cylindrical disk. In use the rotation of the drive shaft will induce rotation of the mixing and impact blades.
The mixing assembly may also include scraping members which are placed on an underside of the circular disk. The scraping members may be in the form of a rib structure which in use, discharges any contaminated material entering the seal assembly.
The direct drive mixing device may include an encoder. The encoder may be in the form of an incremental angle encoder positioned proximate the drive shaft. The encoder may be operable to measure the direction of rotation of the drive shaft. The encoder may be connected to the drive motor and in use operable to switch off the motor if the direction of rotation of the drive shaft changes.
The motor assembly may further include cooling means. In one embodiment of the invention, the cooling means may be in the form of a water-cooled system. The motor assembly may include an outer jacketed compartment which is placed around the motor. The water-cooled system may include a pump which in use pumps cooled water from a water cooler or a heat exchanger through the jacketed compartment of the motor thereby cooling the motor.
The mixer frame of the direct drive mixing device may be in the form of a first and second frame, the first frame may be in the form of a tilt frame in which the motor assembly and bowl are seated. The second frame may be in the form of a stationary support frame secured to the tilt frame. In one embodiment of the invention, the stationary support frame may support the tilt frame in an elevated position above the ground. In such an embodiment the tilt frame may include cylindrical supporting arms extending from at least two sides of the frame, the cylindrical supporting arms extending through a bearing assembly located in the stationary support frame and connected to a second motor assembly in the form of a motor arrangement operable to rotate the cylindrical supporting arms in order to tilt the tilt frame relative the stationary support frame.
In another embodiment of the invention, the mixing device may include at least one actuator in the form of a pneumatic or hydraulic cylinder. The pneumatic or hydraulic actuator may be located proximate the supporting frame and connected to the tilt frame. The actuator may be able to tilt the tilt frame about the horizontal axis.
The mixing device may furthermore include a second encoder which in use tracks the rotational movement of the tilt frame about the horizontal axis. In another embodiment of the invention, the mixing device may include at least one limit switch connected to the actuator/second motor assembly and operable to limit the rotation of the tilt frame by switching the actuator/second motor assembly off.
The mixing device may include a lid assembly which in use is operable to cover an open end of the bowl. The lid assembly may include a lid support to which the lid is rotationally secured. The lid may include a plurality of flanges which extends parallel from the disk, the flanges shaped to be receivable by corresponding holding latches located around the periphery of the open end of the bowl. In use, the holding latches may be able to lock the lid in a closed position thereby allowing the mixing bowl to be pressurised, forcing an increase of air into the mixture.
The lid assembly may further include a vertical movement mechanism and a rotational movement mechanism. The vertical movement mechanism secured to the supporting frame and the lid support and configured to move the lid in a direction transversely away and towards the open end of the bowl. In one embodiment the vertical movement mechanism may be in the form of at least one actuator in the form of a pneumatic or hydraulic cylinder which. The rotational movement mechanism may be in the form of a rotary motor which is housed inside the lid frame and connected to the lid thereby allowing the rotational movement mechanism to rotate the lid in a clockwise or anti-clockwise direction. In one embodiment the lid may include a central shaft extending upward from the lid, the central shaft connected to the rotational movement mechanism. In use, the rotation of the lid by the rotational movement mechanism allows the four holding latches to be selectively engaged and disengaged by the four flanges defining a closed condition and open condition respectively.
The invention is now described, by way of non-limiting example, with reference to the accompanying drawings:
FIGURES
In the figures:
Figure 1 shows a cross sectional view of a direct drive mixing device without a supporting frame;
Figure 2 shows a detailed section view of the direct drive mixing device as seen in Figure 1 ;
Figure 3 shows a cross sectional view of a motor assembly and a mixing assembly of the direct drive mixing device as seen in Figure 1 ;
Figure 4 shows a three-dimensional view from the front of the direct drive mixing device; and
Figure 5 shows a three-dimensional view from the rear of the direct drive mixing device as seen in Figure 4.
In the drawings, like reference numerals denote like parts of the invention unless otherwise indicated.
EMBODIMENT OF THE INVENTION
In Figure 1 reference numeral (10) refers to a direct drive mixing device. The direct drive mixing device (10) is housed inside a tilt frame (12) which is defined by a structural outer shell (12.1 ) and inner supporting beams (12.2) constructed from tubular members. The outer shell (12.1 ) of the tilt frame (12) includes supporting arms
(12.1.1 ) which extends from opposed sides of the tilt frame (12) allowing the tilt frame to be supported as seen in Figure 4 and 5.
The direct drive mixing device further includes a motor assembly (16) which is contained in a lower part of the tilt frame (12) and supported on either side by the inner motor supporting beams (12.2.1 ). The direct drive mixing device (10) also includes a bowl (18), seated inside the tilt frame (12) and supported by the inner bowl supporting beams (12.2.2) above the motor assembly (16). The mixing device (10) includes a mixing assembly (20) which is located inside the bowl (18) and is use, the motor assembly capable of driving the mixing assembly (20) in order to create a homogeneous mixture of a heterogenous mixture of a powdered substance and fluid placed inside the bowl (18).
The motor assembly (16) includes a drive motor (16.1 ), in the form of a torque motor, and a drive shaft (16.2) having a lower section which is directly coupled to the torque motor (16.1 ) and a upper section which extends vertically upward away from the torque motor (16.1 ) through an opening and into the mixing bowl (18).
The motor assembly also includes a water-cooled system which includes a jacketed compartment (22), which encloses the torque motor (16.1 ), and a pump
(23). In use, the pump (23) will dispense cool water from a container (25) into the jacketed compartment (22) thereby cooling the torque motor (16.1 ).
The direct drive mixing device furthermore includes a bearing hub
(24) through which the drive shaft (16.2) extends. The bearing hub (24) is in the form of an enclosure which is placed around the drive shaft (16.2) between the torque motor
(16.1 ) and the bowl (18). The bearing hub (24) includes two spherical bearings (26) which are placed, adjacent to one another, around the drive shaft (16.2) in order to maintain the alignment of the drive shaft (16.2).
The direct drive mixing device (10) includes an incremental angle encoder (28) located inside the bearing hub (24) proximate the drive shaft (16.2). The incremental angle encoder (28) is connected to the torque motor (16.1 ). In use, the encoder (28) is operable to measure the direction of the rotation of the drive shaft (16.2) and to switch off the torque motor (16.1 ) when a change in the direction of rotation is detected.
The bowl (18) of the direct drive mixing device is in the form of a mixing bowl which is seated inside the tilt frame (12) such that a base plate (18.1 ) of the mixing bowl (18) faces the bearing hub (24). The base plate (18.1 ) of the mixing bowl (18) includes an opening (32) which is dimensioned to receive the upper section of the drive shaft (16.2), the drive shaft extends from the torque motor (16.1 ) into the mixing bowl (18).
As best shown in Figure 2, the bearing hub (24) furthermore includes a seal (34) which is placed around the drive shaft (16.2) at the opening (32) in the mixing bowl’s base plate (18.1 ). The seal (34) is in the form of a cartridge seal which in use, is operable to seal the opening (32) in the base plate (18.1 ) around the drive shaft (16.2).
The cartridge seal (34) includes a rotatable inner section (34.1 ) which is connected to the drive shaft (16.2), and a non-rotating outer section (34.2) which abuts the base plate at the opening (32) and a seal member (not shown) between the inner and outer section. The rotatable inner section (34.1 ) of the seal is secured to the drive shaft (16.2) allowing the rotatable inner section (34.1 ) to rotate coincidently with the drive shaft (16.2) and the non-rotating outer section (34.2) to remain stationary in the opening (32) of the base plate (18.1 ).
In Figure 3 a cross-sectional view of the motor assembly (16) and the mixing assembly (20) of the direct drive mixing device (10) is shown. The direct drive mixing device (10) includes a seal lubrication system (36) which consist of a pump (36.1 ) which is positioned inside the tilt frame (12) with outlet ports (36.2) located proximate the cartridge seal (34), the pump (36.1 ) able to provide a constant flow of lubricant from a storage tank (36.3) to the outlet ports (36.2) to create a thin film of lubricant between a face of the rotating inner section (34.1 ) and a face of the non- rotating outer section (34.2). Advantageously, the thin film of lubrication allows the cartridge seal (34) to remain lubricated without relying on fluid from the mixture inside the bowl.
The mixing assembly (20) of the direct drive mixing device (10) also includes a circular disk (50) which include scraping members (52) in the form of L shaped supports (52), with a flange (52.1 ) of the L shape support extending pass the cylindrical disk (50). In use, the scraping members (52) are operable to discharge any contaminated material from passing through the opening (32) and entering the cartridge seal (34).
The mixing assembly (20) furthermore includes a securing cap (54) which abuts the drive shaft (16.2) on the upper section which extends into the mixing bowl, the securing cap (54) having a circular indentation (54.1 ) on an underside which is shaped to receive an annular tube (56). The mixing assembly also includes a rod (58) with a threaded portion on one end (58.1 ) and an increased diameter head (58.2) on an opposed end. In use, the mixing assembly (20) is secured to the drive shaft (16.2) through placing the rod (58) through the annular tube (56) with the threaded portion (58.1 ) of the rod secured into a threaded hole (16.3) in the drive shaft. Thereafter, the increased diameter head of the rod (58.2) will push down on the annular tube (56), such that the securing cap (54) keeps the L shaped support (52) and cylindrical disk (50) in place.
The mixing assembly (20) furthermore includes mixing and impact blades (60) which extend perpendicular from the cylindrical disk (50). In this embodiment, the mixing and impact blades (60) are based on a ribbon mixing auger design.
In Figure 4 and 5 the tilt frame (12) of the direct drive mixing device (10) is shown as supported by a support frame (14) located on opposed sides of the tilt frame (12). The support frame (14) allowing the tilt frame (12) to be suspended in an elevated position above the ground thereby in use allowing the tilt frame (12) to be rotated above a horizontal axis. The support frame (14) having circular apertures (not shown) through which the support arms (12.1 .1 ) of the tilt frame (12) is receivable in order to support the tilt frame (12). In Figure 4 and 5 a lid assembly (38) of the direct drive mixing device is shown. The lid assembly (38) includes four holding latches (40) located around an open end of the mixing bowl (18.3). The lid assembly further includes a lid (42) which is shaped and dimensioned to match the open end of the mixing bowl (18.3), with four flanges extending parallel from the disk, the flanges (42.1 ) shaped to be receivable by the holding latches (40). In use, the holding latches (40) are able to lock the lid (42) in a closed position thereby allowing the mixing bowl (18) to be pressurised, forcing an increase of air into the mixture.
The lid assembly (38) also includes a vertical movement mechanism (44) which is secured at one end to a lid support (41 ) and the other end to the support frame (14). The vertical movement mechanism (44) is in the form of at least one actuator which is configured to move the lid support (41 ) in a direction (48) transversely away and towards the open end (18.3) of the mixing bowl (18) thereby defining an open and closed configuration.
The lid assembly (38) furthermore includes a rotational movement mechanism (46) in the form of a rotary motor which is housed inside the lid support (41 ). The rotary motor connected to the lid via a transfer shaft (not shown) allowing the rotary motor to rotate the lid (42) in a clockwise or anti-clockwise direction about a rotation axis (50) which allows the four holding latches (40) to be selectively engaged and disengaged by the four flanges (42.1 ) defining a locked condition and unlocked condition respectively.
The lid support (41 ) is in the form of a frame constructed of a plurality of square tubes and shaped and dimensioned to allow the vertical movement mechanism (44) to move the lid (42) and the rotational movement mechanism (46) to be housed therein.
In Figure 5 reference numeral (62) refers to a tilt motor arrangement which includes a tilt motor (62) and a gear configuration (62.1 ). The tilt motor (62) is positioned on one side of the supporting frame (14) and is connected to the tilt frame (12) through the gear configuration (62.1 ). More specifically the gear configuration (62.1 ) is connected to a shaft (not shown) which extends from the tilt frame. In use, the tilt motor rotates the shaft (not shown) via the gear configuration (62.1 ) which allows the tilt frame (12) to be rotated. In use, the tilt motor (62) is operable to rotate the tilt frame (12), with the mixing bowl seated (18) inside the tilt frame (12), about the horizontal axis in order to unload the material in the mixing bowl (12).
The tilt motor arrangement further includes a second encoder (not shown) which is placed proximate the tilt frame (12). In use, the second encoder tracks the rotational position of the tilt frame (12) and is capable of switching the tilt motor (62) off if the frame reaches a predefined rotational limit.
The inventor believes that the invention provides a direct mixing device that is capable of reducing the mechanical losses and thereby increasing the efficiency of the mixing device as well as reducing the mixing time of each mixing operation.