Mixing device and mixing method for liquid quick-acting topdressing
Technical Field
The invention relates to the technical field of liquid quick-acting topdressing production, in particular to a mixing device and a mixing method for liquid quick-acting topdressing.
Background
The quick-acting liquid top dressing fertilizer is a liquid product containing two or more nutrient elements required by crops, and has the characteristics of high production nutrient content, easy compounding, direct absorption by crops, convenient formula fertilization, drip irrigation and spray irrigation fertilization, mechanized fertilization and the like.
However, the existing mixing device for liquid quick-acting topdressing production has some problems in the using process: firstly, under the influence of a stirring structure in the device, the uniform dispersion of raw materials cannot be realized in the mixing process, so that the mixing effect is poor; secondly, under the influence of the raw material body, the problem that the blocky raw materials are easy to coagulate blocky when directly participating in mixing further causes the reduction of the mixing effect, so the existing requirements are not met, and the mixing device and the mixing method for the liquid quick-acting additional fertilizer are provided.
Disclosure of Invention
The invention aims to provide a mixing device and a mixing method for liquid quick-acting top dressing, which aim to solve the problems that the mixing device proposed in the background art is influenced by a self-stirring structure and the mixing effect is poor due to block coagulation generated in the stirring process.
In order to achieve the purpose, the invention provides the following technical scheme: a mixing device for quick-acting liquid topdressing and a mixing method thereof comprise a mixing barrel, wherein a premixing barrel is fixedly arranged at the upper end of the mixing barrel, a liquid mixing cavity and a solid mixing cavity are respectively arranged in the premixing barrel, the liquid mixing cavity and the solid mixing cavity are respectively provided with two parts, the liquid mixing cavity and the solid mixing cavity are symmetrically distributed, a top cover is arranged at the upper end of the premixing barrel, liquid material inlets are arranged at two sides in the top cover and are positioned above the liquid mixing cavity, crushing devices are respectively arranged at the front and the back of the upper end of the top cover, solid material inlets are respectively arranged at two sides of the upper end of the crushing device, a crank is arranged at the upper end of the crushing device, cross-shaped stirring rods are respectively arranged at the bottoms of the liquid mixing cavity and the solid mixing cavity and are in running fit with the premixing barrel, a partition plate is fixedly sealed between the mixing barrel and the premixing barrel, the bottom of mixing drum rotates installs first rotation axis, the inside of first rotation axis is provided with the transmission chamber, the bottom fixed mounting of mixing drum has first motor, and the output shaft of first motor passes through the shaft coupling transmission with first rotation axis and is connected, the lower extreme of mixing drum one side is provided with the discharge gate.
In a further embodiment, a second rotating shaft is fixedly installed at the middle position of the lower end of the partition board, the lower end of the second rotating shaft extends into the transmission cavity, the lower end of the second rotating shaft is rotatably connected with the bottom of the transmission cavity through a bearing, four driving bevel gears are arranged at one end of the first rotating shaft, which is positioned in the transmission cavity, the driving bevel gears are vertically adjacent and are arranged in a reverse direction, stirring rods are arranged on two sides of the first rotating shaft, one end of each stirring rod extends into the transmission cavity, the stirring rods are rotatably connected with the first rotating shaft through bearing sleeves, a driven bevel gear is fixedly installed at one end of each stirring rod, which is positioned in the transmission cavity, the driven bevel gear is meshed with the driving bevel gear, and the driving bevel gear driven by the stirring rod is positioned above the driven bevel gear, the driving bevel gear driven by the stirring rod on the other side is positioned below the driven bevel gear, and complex multidirectional stirring motion is formed on the basis of a simple driving structure, so that the mixing effect of raw materials in the stirring cylinder is further improved.
In a further embodiment, the inside of the smashing device is rotatably provided with a smashing rotating shaft, the diameter of the smashing rotating shaft is gradually increased from top to bottom, the outside of the smashing rotating shaft is fixedly provided with five spiral extrusion blades, the distance between the spiral extrusion blades is gradually reduced from top to bottom, the outer ring of each spiral extrusion blade is attached to the inner wall of the smashing device, the lower end of the inside of the smashing device is provided with a first smashing plate, the first smashing plate is in rotating fit with the smashing device, a connecting plate is arranged at the middle position of the inside of the first smashing plate, the lower end of the smashing rotating shaft is rotatably connected with the connecting plate through a bearing, the outside of the connecting plate is fixedly provided with a first metal smashing net, the lower end of the smashing device is fixedly provided with a second smashing plate, a bottom plate is fixedly arranged at the middle position of the inside of the second smashing plate, the outside of bottom plate is provided with the second metal and smashes the net, and the mesh number of second metal is smashed the net and is greater than first metal and smashes the net, receives the effect of rotational friction power and extrusion force, further smashes the raw materials for powdered, is favorable to dissolving fast, avoids taking place the cubic to condense.
In a further embodiment, the fixed water ring that is provided with in inside upper end of a section of thick bamboo in advance, the inboard of water ring all seals and is fixed with the shower nozzle, and the shower nozzle is provided with four, and the shower nozzle is located the inside of liquid mixing chamber and solid mixing chamber respectively, the contained angle that is less than ninety degrees between the place plane of shower nozzle and the water ring place plane is forty-five degrees, the intermediate position department of shower nozzle is provided with the solenoid valve, the one end of water ring is provided with the inlet tube, and the inlet tube extends to the outside of a section of thick bamboo in advance, through this kind of mode, can be independent realize single or a plurality of solid, the preliminary mixing of liquid raw materials is handled, is in the optimum when guaranteeing the raw materials unified mixture.
In further embodiment, the below of liquid mixing chamber and solid mixing chamber all is provided with fixed box, and fixed box and a premix section of thick bamboo pass through the bolt fastening, the inside fixed mounting of fixed box has the second motor, the output shaft fixed mounting of second motor has the rotary disk, the both sides of rotary disk upper end are all fixed and are provided with magnet, and magnet and cross puddler looks adaptation, and magnetism is inhaled formula stirring structure occupation space and is little, and the mixing effect is good.
In a further embodiment, the liquid mixing chamber and the solid mixing chamber are both fixed with the mixing cylinder in a sealing manner through a connecting pipe, an electromagnetic valve is fixedly mounted at the middle position of the connecting pipe, and heating devices are fixedly mounted on the inner walls of the liquid mixing chamber and the solid mixing chamber respectively to heat the raw materials in the liquid mixing chamber and the solid mixing chamber to proper temperatures.
In further embodiment, the externally mounted of mixing drum has vibrations agitating unit, and vibrations agitating unit passes through the bolt fastening with the mixing drum, vibrations agitating unit's inside is equipped with six groups and is the ultrasonic wave oscillators that annular evenly distributed, and every group ultrasonic wave oscillator is provided with threely, ultrasonic wave amplitude transformer is all installed to ultrasonic wave oscillator's one end, ultrasonic wave amplitude transformer's one end is provided with the syringe needle, and the syringe needle extends to the inside of mixing drum, and in the syringe needle transmitted the ultrasonic wave to raw materials liquid, and the hydrone in the in-process liquid takes place violent motion, forms the stirring to raw materials in the mixing drum fast, and the cooperation puddler improves mixing efficiency under the prerequisite of guaranteeing mixed effect.
The mixing method of the mixing device for the quick-acting liquid additional fertilizer comprises the following steps:
the method comprises the following steps that firstly, liquid raw materials and solid raw materials are separately processed, the liquid raw materials enter a liquid mixing cavity through a liquid material inlet, the liquid raw materials are diluted by adding water through opening a spray head, a heating device is started to reach the optimal reaction temperature, and then the whole stirring is completed by utilizing a magnetic type stirring mechanism;
secondly, the solid raw material enters a smashing device through a solid material inlet, a crank is rotated to enable a smashing rotating shaft with a spiral extrusion blade arranged inside the smashing device to rotate, the solid raw material is continuously extruded to the lower part, and smashing treatment of the solid raw material is realized under the matching of a first smashing plate and a second smashing plate;
step three, as with the step one, adding water to dilute the crushed solid raw materials, heating to a proper reaction temperature, and then stirring;
opening the connecting pipe, enabling the pretreated raw materials to enter a mixing cylinder at the same time, starting a first motor, and fully mixing the raw materials by utilizing a multidirectional rotating stirring structure;
step five, in the rotating process of the stirring rod, starting the ultrasonic vibrator, transmitting ultrasonic waves into the raw material liquid by the needle head, and rapidly stirring the raw materials in the mixing cylinder by water molecules in the liquid in the process;
and step six, discharging the raw materials through a discharge hole after the final stirring is finished.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention is characterized in that a multidirectional stirring structure is arranged in the mixing drum, a first rotating shaft is driven to rotate by a first motor, the upper end of a second rotating shaft is fixed with a baffle plate, the lower end of the second rotating shaft is in rotating fit with a transmission cavity in the first rotating shaft through a bearing, so that the second rotating shaft is kept static in the rotating process of the first rotating shaft, a driven bevel gear of a stirring rod positioned at one end in the transmission cavity revolves around a driving bevel gear on the first rotating shaft, the stirring rod is engaged with the bevel gear under the rotating fit of a bearing sleeve, the stirring rod rotates around the first rotating shaft while revolving around the first rotating shaft to form different stirring directions, the stirring effect is effectively improved, in addition, the driving bevel gears which are vertically adjacent are arranged in a reverse direction, and the driving bevel gear driven by the stirring rod on one side is positioned above the driven bevel gear, the driving bevel gear driven by the stirring rod on the other side is positioned below the driven bevel gear, so that the driving bevel gear and the driven bevel gear are opposite to each other in the rotating direction, and complex multidirectional stirring motion is formed on a simple driving structure, so that the mixing effect of raw materials in the stirring cylinder is further improved.
2. The invention is provided with the premixing cylinder, liquid raw materials and solid raw materials are pretreated separately, the liquid raw materials enter the liquid mixing cavity through the liquid material inlet, the solid raw materials enter the solid mixing cavity through the fragmenting device, because the upper end of the inner wall of the premixing cylinder is provided with the water ring, and the spray heads on the water ring are provided with the independent electromagnetic valves, water can be reasonably and independently added according to the entering amount of the raw materials, meanwhile, each premixing cavity is provided with the independent heating device, the proper reaction temperature can be ensured to be kept when the raw materials are pretreated, in addition, by starting the second motor, the output shaft of the second motor drives the rotating disc with the magnet arranged at the upper end to rotate at high speed, the magnetic attraction exists between the magnets and the cross-shaped stirring rods at the bottoms of the liquid mixing cavity and the solid mixing cavity, and the rotation of the magnets leads the cross-shaped stirring rods to rotate in the mixing cavity, the stirring of the raw materials in the device is realized, and by adopting the mode, the premixing treatment of single or multiple solid and liquid raw materials can be independently realized, and the raw materials are in the optimal state when uniformly mixed.
3. The invention is characterized in that a smashing device is arranged above a solid mixing cavity, the smashing device and a mixing cylinder are fixed through a clamping groove, so the smashing device can be flexibly assembled and disassembled, before premixing granular raw materials, the granular raw materials are poured into the smashing device through a solid material inlet, a shaking handle is rotated to drive an inner smashing rotating shaft to rotate, as the diameter of the smashing rotating shaft is gradually increased from top to bottom, and simultaneously the distance between spiral extrusion blades outside the smashing rotating shaft is gradually reduced from top to bottom, the raw materials continuously move downwards along with the continuous rotation of the spiral extrusion blades, the space is gradually reduced in the moving process to form the extrusion on the raw materials, large-block raw materials can be preferentially extruded into small blocks, when the raw materials move to a first metal smashing net, the small-block particles are divided into a plurality of smaller particles by a metal net under the action of extrusion force and fall to the upper end of a second metal smashing net, keep relative rotation between first metal fragmentation net and the second metal fragmentation net, the metal mesh number on the second metal fragmentation net is bigger moreover, consequently receives the effect of rotational friction power and extrusion force, further smashes the raw materials into powdered, is favorable to dissolving fast, avoids taking place the cubic to condense.
4. According to the invention, the vibration stirring device is arranged outside the mixing cylinder, six groups of ultrasonic vibrators distributed in an annular shape are arranged inside the vibration stirring device, the ultrasonic vibrators can generate ultrasonic waves after being electrified, the ultrasonic waves are transmitted to the needle head under the amplification of the ultrasonic amplitude transformer, then the ultrasonic waves are transmitted to the raw material liquid through the needle head, water molecules in the liquid generate violent movement in the process, the raw material in the mixing cylinder is quickly stirred, and the mixing efficiency is improved under the premise of ensuring the mixing effect by matching with the stirring rod.
Drawings
FIG. 1 is an overall perspective view of the present invention;
FIG. 2 is a schematic view of the overall internal structure of the present invention;
FIG. 3 is an enlarged view of a portion of the area A of FIG. 2 according to the present invention;
FIG. 4 is a perspective view of the interior of the premix barrel of the present invention;
FIG. 5 is a top view of the interior of the premix barrel of the present invention;
FIG. 6 is an enlarged view of a portion of the area B of FIG. 2 in accordance with the present invention;
FIG. 7 is a perspective view of a reducing plate of the present invention;
fig. 8 is a partial enlarged view of the area C in fig. 2 according to the present invention.
In the figure: 1. a mixing drum; 2. a premix barrel; 3. a top cover; 4. a fragmenting device; 5. a liquid material inlet; 6. a solid material inlet; 7. a crank; 8. a discharge port; 9. a water inlet pipe; 10. vibrating the stirring device; 11. crushing the rotating shaft; 12. a screw extrusion blade; 13. a water ring; 14. a spray head; 15. a liquid mixing chamber; 16. a solids mixing chamber; 17. a heating device; 18. a partition plate; 19. a connecting pipe; 20. a first rotating shaft; 21. a transmission cavity; 22. a second rotation shaft; 23. a stirring rod; 24. a first motor; 25. an ultrasonic vibrator; 26. an ultrasonic horn; 27. a needle head; 28. a driving bevel gear; 29. a bearing housing; 30. a cross-shaped stirring rod; 31. a fixing box; 32. a second motor; 33. rotating the disc; 34. a magnet; 35. a first reducing plate; 36. a second reducing plate; 37. a connecting plate; 38. a first metal screen; 39. a base plate; 40. a second metal screen; 41. a driven bevel gear.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.
Referring to fig. 1-8, an embodiment of the present invention: a mixing device for liquid quick-acting topdressing and a mixing method thereof comprise a mixing barrel 1, a premixing barrel 2 is fixedly arranged at the upper end of the mixing barrel 1, a liquid mixing cavity 15 and a solid mixing cavity 16 are respectively arranged in the premixing barrel 2, the liquid mixing cavity 15 and the solid mixing cavity 16 are respectively provided with two cavities, the liquid mixing cavity 15 and the solid mixing cavity 16 are symmetrically distributed, the liquid mixing cavity 15 and the solid mixing cavity 16 are independently arranged and can respectively realize the treatment of solid and liquid raw materials, a top cover 3 is arranged at the upper end of the premixing barrel 2, the top cover 3 is of a movable installation type structure, liquid material inlets 5 are arranged at two sides in the top cover 3, the liquid material inlets 5 are positioned above the liquid mixing cavity 15, a smashing device 4 is respectively arranged at the front and the back of the upper end of the top cover 3, the smashing device 4 is of a movable installation type structure and can be detached when not used, so that four conventional premixing cavities are formed below the top cover, both sides of the upper end of the smashing device 4 are provided with solid material inlets 6, a crank 7 is installed at the upper end of the smashing device 4, the bottoms of the liquid mixing cavity 15 and the solid mixing cavity 16 are provided with cross-shaped stirring rods 30, the cross-shaped stirring rods 30 are made of metal materials, the cross-shaped stirring rods 30 are in running fit with the premixing barrel 2, a partition plate 18 is fixed between the mixing barrel 1 and the premixing barrel 2 in a sealing mode, the partition plate 18 is used for installing a driving element of a magnetic stirring mechanism in a space where the mixing barrel 1 and the premixing barrel 2 are separated, a first rotating shaft 20 is installed at the bottom of the mixing barrel 1 in a rotating mode, a transmission cavity 21 is arranged inside the first rotating shaft 20, a first motor 24 is fixedly installed at the bottom of the mixing barrel 1, an output shaft of the first motor 24 is in transmission connection with the first rotating shaft 20 through a coupler, and a discharge port 8 is arranged at the lower end of one side of the mixing barrel 1.
Further, a second rotating shaft 22 is fixedly installed at the middle position of the lower end of the partition 18, the lower end of the second rotating shaft 22 extends into the transmission cavity 21, the lower end of the second rotating shaft 22 is rotatably connected with the bottom of the transmission cavity 21 through a bearing, four driving bevel gears 28 are arranged at one end of the first rotating shaft 20 located inside the transmission cavity 21, the driving bevel gears 28 vertically adjacent to each other are oppositely arranged, stirring rods 23 are arranged on both sides of the first rotating shaft 20, one end of each stirring rod 23 extends into the transmission cavity 21, the stirring rods 23 are rotatably connected with the first rotating shaft 20 through bearing sleeves 29, a driven bevel gear 41 is fixedly installed at one end of each stirring rod 23 located inside the transmission cavity 21, the driven bevel gear 41 is connected with the driving bevel gear 28 in a meshing manner, the driving bevel gear 28 driven by the stirring rod 23 on one side is located above the driven bevel gear 41, the driving bevel gear 28 driven by the stirring rod 23 on the other side is located below the driven bevel gear 41, the first rotating shaft 20 is driven to rotate by the first motor 24, the second rotating shaft 22 is kept stationary during the rotation of the first rotating shaft 20 because the upper end of the second rotating shaft 22 is fixed with the partition plate 18 and the lower end thereof is in rotational fit with the transmission cavity 21 in the first rotating shaft 20 through a bearing, at this time, the driven bevel gear 41 located at one end inside the transmission cavity 21 of the stirring rod 23 revolves around the driving bevel gear 28 on the first rotating shaft 20, and the stirring rod 23 is engaged with the bevel gear under the rotational fit with the bearing sleeve 29, and the stirring rod 23 rotates around the first rotating shaft 20 while revolving around itself, so as to form different stirring directions, thereby effectively improving the stirring effect.
Further, a smashing rotating shaft 11 is rotatably installed inside the smashing device 4, the diameter of the smashing rotating shaft 11 is gradually increased from top to bottom, spiral extrusion blades 12 are fixedly arranged outside the smashing rotating shaft 11, five spiral extrusion blades 12 are arranged, the distance between every two spiral extrusion blades 12 is gradually reduced from top to bottom, the outer ring of each spiral extrusion blade 12 is attached to the inner wall of the smashing device 4, a first smashing plate 35 is arranged at the lower end inside the smashing device 4, the first smashing plate 35 is in rotating fit with the smashing device 4, a connecting plate 37 is arranged at the middle position inside the first smashing plate 35, the lower end of the smashing rotating shaft 11 is rotatably connected with the connecting plate 37 through a bearing, a first metal smashing net 38 is fixedly arranged outside the connecting plate 37, a second smashing plate 36 is fixedly arranged at the lower end of the smashing device 4, a bottom plate 39 is fixedly arranged at the middle position inside the second smashing plate 36, the second metal crushing net 40 is arranged outside the bottom plate 39, the mesh number of the second metal crushing net 40 is larger than that of the first metal crushing net 38, before premixing the granular raw materials, the granular raw materials are poured into the crushing device 4 through the solid material inlet 6, the handle 7 is rotated to drive the crushing rotating shaft 11 inside to rotate, the diameter of the crushing rotating shaft 11 is gradually increased from top to bottom, meanwhile, the distance between the spiral extrusion blades 12 outside the crushing rotating shaft 11 is gradually reduced from top to bottom, the raw materials continuously move downwards along with the continuous rotation of the spiral extrusion blades 12, the space is gradually reduced in the moving process to form extrusion on the raw materials, the massive raw materials can be preferentially extruded into small blocks, when the raw materials move to the first metal crushing net 38, the small blocks are divided into a plurality of smaller particles by the metal nets under the action of extrusion force, and the small particles fall to the upper end of the second metal crushing net 40, the first wire mesh crusher 38 and the second wire mesh crusher 40 are rotated relative to each other, and the wire mesh number of the second wire mesh crusher 40 is larger, so that the raw material is crushed into powder by the rotational friction force and the pressing force.
Further, the fixed water ring 13 that is provided with in the inside upper end of a premix section of thick bamboo 2, the inboard of water ring 13 is all sealed and is fixed with shower nozzle 14, shower nozzle 14 is provided with four, and shower nozzle 14 is located the inside of liquid mixing chamber 15 and solid mixing chamber 16 respectively, the contained angle that is less than ninety degrees between the place plane of shower nozzle 14 and the water ring 13 place plane is forty-five degrees, the intermediate position department of shower nozzle 14 is provided with the solenoid valve, the one end of water ring 13 is provided with inlet tube 9, and inlet tube 9 extends to the outside of a premix section of thick bamboo 2, shower nozzle 14 on the water ring 13 has all set up independent solenoid valve, consequently, can be according to the entering volume of raw materials, reasonable and independent adding water.
Further, the liquid mixing chamber 15 and the solid mixing chamber 16 are all provided with the fixed box 31 below, and the fixed box 31 passes through the bolt fastening with premixing section of thick bamboo 2, the inside fixed mounting of fixed box 31 has the second motor 32, the output shaft fixed mounting of second motor 32 has rotary disk 33, the both sides of rotary disk 33 upper end are all fixed and are provided with magnet 34, and magnet 34 and cross puddler 30 looks adaptation, the output shaft of second motor 32 drives the rotary disk 33 that the magnet 34 is equipped with to the upper end and carries out high-speed rotation, there is magnetic attraction between cross puddler 30 and the magnet 34 of liquid mixing chamber 15 and solid mixing chamber 16 bottom, along with the rotation of magnet 34, make cross puddler 30 rotate in the mixing chamber, realize the stirring to inside raw materials.
Further, the liquid mixing chamber 15 and the solid mixing chamber 16 are both fixed with the mixing cylinder 1 in a sealing manner through a connecting pipe 19, an electromagnetic valve is fixedly mounted at the middle position of the connecting pipe 19, and heating devices 17 are fixedly mounted on the inner walls of the liquid mixing chamber 15 and the solid mixing chamber 16.
Further, the externally mounted of mixing drum 1 has vibrations agitating unit 10, and vibrations agitating unit 10 passes through the bolt fastening with mixing drum 1, the inside of vibrations agitating unit 10 is equipped with six sets of ultrasonic vibrator 25 that are annular evenly distributed, and every ultrasonic vibrator 25 of group is provided with threely, ultrasonic horn 26 is all installed to ultrasonic vibrator 25's one end, ultrasonic horn 26's one end is provided with syringe needle 27, and syringe needle 27 extends to the inside of mixing drum 1, can produce the ultrasonic wave after ultrasonic vibrator 25 circular telegram, the ultrasonic wave transmits to the syringe needle under ultrasonic horn 26's the amplification, again by syringe needle 27 with ultrasonic wave transmission to raw materials liquid in, the hydrone in-process liquid takes place violent motion, form the stirring to raw materials in the mixing drum fast.
The mixing method of the mixing device for the quick-acting liquid additional fertilizer is characterized in that: the method comprises the following steps:
step one, liquid raw materials and solid raw materials are separately processed, the liquid raw materials enter a liquid mixing cavity 15 through a liquid material inlet 5, the liquid raw materials are diluted by adding water through opening a spray head 14, a heating device 17 is started to reach the optimal reaction temperature, and then the whole stirring is completed by utilizing a magnetic type stirring mechanism;
secondly, the solid raw material enters the smashing device 4 through the solid material inlet 6, the crank 7 is rotated to enable the smashing rotating shaft 11 provided with the spiral extrusion blades 12 in the smashing device 4 to rotate, the solid raw material is continuously extruded to the lower part, and the smashing treatment of the solid raw material is realized under the matching of the first smashing plate 35 and the second smashing plate 36;
step three, as with the step one, adding water to dilute the crushed solid raw materials, heating to a proper reaction temperature, and then stirring;
step four, opening the connecting pipe 19, enabling the pretreated raw materials to enter the mixing cylinder 1 at the same time, starting the first motor 24, and fully mixing the raw materials by utilizing a multidirectional rotating stirring structure;
step five, in the rotating process of the stirring rod 23, the ultrasonic vibrator 25 is started, the needle 27 transmits ultrasonic waves to the raw material liquid, and water molecules in the liquid violently move in the process to quickly stir the raw materials in the mixing cylinder 1;
and step six, discharging the raw materials through a discharge port 8 after the final stirring is finished.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.