Agitation system for blowing wool machine

Abstract

A machine for distributing blowing wool from a bag of compressed blowing wool is provided. The machine includes a shredding chamber configured to shred and pick apart the blowing wool. The shredding chamber includes a plurality of shredders and an agitator. The plurality of shredders and the agitator are configured for rotation. The plurality of shredders and the agitator are configured to rotate at different speeds.

Description

TECHNICAL FIELD

This invention relates to loosefil insulation for insulating buildings. More particularly this invention relates to machines for distributing packaged loosefil insulation.

BACKGROUND OF THE INVENTION

In the insulation of buildings, a frequently used insulation product is loosefil insulation. In contrast to the unitary or monolithic structure of insulation batts or blankets, loosefil insulation is a multiplicity of discrete, individual tufts, cubes, flakes or nodules. Loosefil insulation is usually applied to buildings by blowing the insulation into an insulation cavity, such as a wall cavity or an attic of a building. Typically loosefil insulation is made of glass fibers although other mineral fibers, organic fibers, and cellulose fibers can be used.

Loosefil insulation, commonly referred to as blowing wool, is typically compressed in packages for transport from an insulation manufacturing site to a building that is to be insulated. Typically the packages include compressed blowing wool encapsulated in a bag. The bags are made of polypropylene or other suitable material. During the packaging of the blowing wool, it is placed under compression for storage and transportation efficiencies. Typically, the blowing wool is packaged with a compression ratio of at least about 10:1. The distribution of blowing wool into an insulation cavity typically uses a blowing wool distribution machine that feeds the blowing wool pneumatically through a distribution hose. Blowing wool distribution machines typically have a large chute or hopper for containing and feeding the blowing wool after the package is opened and the blowing wool is allowed to expand.

It would be advantageous if blowing wool machines could be improved to make them easier to use.

SUMMARY OF THE INVENTION

The above objects as well as other objects not specifically enumerated are achieved by a machine for distributing blowing wool from a bag of compressed blowing wool. The machine includes a shredding chamber configured to shred and pick apart the blowing wool. The shredding chamber includes a plurality of shredders and an agitator. The plurality of shredders and the agitator are configured for rotation. The plurality of shredders and the agitator are configured to rotate at different speeds.

According to this invention there is also provided a machine for distributing blowing wool from a bag of compressed blowing wool. The machine includes a chute having an inlet end, the inlet end configured to receive the bag of compressed blowing wool. A shredding chamber is associated with the chute and is configured to shred and pick apart the blowing wool. The shredding chamber includes a plurality of shredders, each shredder having a plurality of paddle assemblies mounted for rotation on a shredder shaft in a manner such that paddle assemblies on one shredder shaft correspond to paddle assemblies on an adjacent shredder shaft. The plurality of paddle assemblies on the one shredder shaft each having a major axis and the corresponding paddle assemblies on the adjacent shredder shaft each having a major axis. The plurality of paddle assemblies are arranged such that the major axes of the corresponding paddle assemblies have an indexed arrangement.

According to this invention there is also provided a machine for distributing blowing wool from a bag of compressed blowing wool. The machine includes a chute having an inlet end, the inlet end configured to receive the bag of compressed blowing wool. A shredding chamber is associated with the chute and configured to shred and pick apart the blowing wool. The shredding chamber includes a plurality of shredders configured for rotation. Each shredder includes a plurality of paddle assemblies mounted to a shredder shaft. Each paddle assembly includes a plurality of paddles. The paddles are mounted to form an acute angle relative to a major axis of the shredder shafts.

According to this invention there is also provided a machine for distributing blowing wool from a bag of compressed blowing wool. The machine includes a chute having an inlet end, the inlet end configured to receive the bag of compressed blowing wool. A shredding chamber is positioned downstream from the chute and configured to shred and pick apart the blowing wool. The shredding chamber includes a plurality of shredders configured for rotation. Each shredder includes a plurality of paddle assemblies mounted to a shredder shaft. The paddle assemblies have paddles. The paddles have a hardness within the range of 60 A to 70 A Durometer to better grip the blowing wool and prevent jamming of the blowing wool within the shredder.

According to this invention there is also provided a machine for distributing blowing wool from a bag of compressed blowing wool. The machine includes a chute having an inlet end, the inlet end configured to receive the bag of compressed blowing wool, a shredding chamber is associated with the chute and includes a plurality of shredders configured to shred and pick apart the blowing wool. The shredders are interchangeable.

Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view in elevation of an insulation blowing wool machine.

FIG. 2 is a front view in elevation, partially in cross-section, of the insulation blowing wool machine of FIG. 1.

FIG. 3 is a side view in elevation of the insulation blowing wool machine of FIG. 1.

FIG. 4 is a front view, partially in cross-section, of the lower unit of the insulation blowing wool machine of FIG. 1.

FIG. 5 is a plan view in elevation, of the shredding chamber of the insulation blowing wool machine of FIG. 1.

FIG. 6 is a perspective view of a low speed shredder of the insulation blowing wool machine of FIG. 1.

FIG. 7 is a front view in cross-section of the low speed shredder shaft of FIG. 5, taken along line 7-7.

FIG. 8 is a front view in cross-section of the blade of the low speed shredder of FIG. 5, taken along line 8-8.

FIG. 9 is a front view in elevation of the agitator, side inlet and discharge mechanism of the insulation blowing machine of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

A blowing wool machine 10 for distributing compressed blowing wool is shown in FIGS. 1-3. The blowing wool machine 10 includes a lower unit 12 and a chute 14. The lower unit 12 is connected to the chute 14 by a plurality of fastening mechanisms 15 configured to readily assemble and disassemble the chute 14 to the lower unit 12. As further shown in FIGS. 1-3, the chute 14 has an inlet end 16 and an outlet end 18.

The chute 14 is configured to receive the blowing wool and introduce the blowing wool to the shredding chamber 23 as shown in FIG. 2. Optionally, the chute 14 includes a handle segment 21, as shown in FIG. 3, to facilitate easy movement of the blowing wool machine 10 from one location to another. However, the handle segment 21 is not necessary to the operation of the machine 10.

As further shown in FIGS. 1-3, the chute 14 includes an optional guide assembly 19 mounted at the inlet end 16 of the chute 14. The guide assembly 19 is configured to urge a package of compressed blowing wool against a cutting mechanism 20, as shown in FIGS. 1 and 3, as the package moves into the chute 14.

As shown in FIG. 2, the shredding chamber 23 is mounted at the outlet end 18 of the chute 14. In this embodiment, the shredding chamber 23 includes a plurality of low speed shredders 24a and 24b and an agitator 26. The low speed shredders 24a and 24b shred and pick apart the blowing wool as the blowing wool is discharged from the outlet end 18 of the chute 14 into the lower unit 12. Although the blowing wool machine 10 is shown with a plurality of low speed shredders 24, any type of separator, such as a clump breaker, beater bar or any other mechanism that shreds and picks apart the blowing wool can be used.

As further shown in FIG. 2, the shredding chamber 23 includes an agitator 26 for final shredding of the blowing wool and for preparing the blowing wool for distribution into an airstream. In this embodiment as shown in FIG. 2, the agitator 26 is beneath the low speed shredders 24a and 24b. Alternatively, the agitator 26 can be disposed in any location relative to the low speed shredders 24a and 24b, such as horizontally adjacent to the shredders 24a and 24b, sufficient to receive the blowing wool from the low speed shredders 24a and 24b. In this embodiment, the agitator 26 is a high speed shredder. Alternatively, any type of shredder can be used, such as a low speed shredder, clump breaker, beater bar or any other mechanism that finely shreds the blowing wool and prepares the blowing wool for distribution into an airstream.

In this embodiment, the low speed shredders 24a and 24b rotate at a lower speed than the agitator 26. The low speed shredders 24a and 24b rotate at a speed of about 40-80 rpm and the agitator 26 rotates at a speed of about 300-500 rpm. In another embodiment, the low speed shredders 24a and 24b can rotate at a speed less than or more than 40-80 rpm, provided the speed is sufficient to shred and pick apart the blowing wool. The agitator 26 can rotate at a speed less than or more than 300-500 rpm provided the speed is sufficient to finely shred the blowing wool and prepare the blowing wool for distribution into the airstream 33.

Referring again to FIG. 2, a discharge mechanism 28 is positioned adjacent to the agitator 26 and is configured to distribute the finely shredded blowing wool into the airstream. In this embodiment, the shredded blowing wool is driven through the discharge mechanism 28 and through a machine outlet 32 by an airstream provided by a blower 36 mounted in the lower unit 12. The airstream is indicated by an arrow 33 as shown in FIG. 3. In another embodiment, the airstream 33 can be provided by another method, such as by a vacuum, sufficient to provide an airstream 33 driven through the discharge mechanism 28. In this embodiment, the blower 36 provides the airstream 33 to the discharge mechanism 28 through a duct 38, shown in phantom in FIG. 2 from the blower 36 to the rotary valve 28. Alternatively, the airstream 33 can be provided to the discharge mechanism 28 by another structure, such as a hose or pipe, sufficient to provide the discharge mechanism 28 with the airstream 33.

The shredders 24a and 24b, agitator 26, discharge mechanism 28 and the blower 36 are mounted for rotation. They can be driven by any suitable means, such as by a motor 34, or any other means sufficient to drive rotary equipment. Alternatively, each of the shredders 24a and 24b, agitator 26, discharge mechanism 28 and blower 36 can be provided with its own motor.

In operation, the chute 14 guides the blowing wool to the shredding chamber 23. The shredding chamber 23 includes the low speed shredders 24a and 24b which shred and pick apart the blowing wool. The shredded blowing wool drops from the low speed shredders 24a and 24b into the agitator 26. The agitator 26 prepares the blowing wool for distribution into the airstream 33 by further shredding the blowing wool. The finely shredded blowing wool exits the agitator 26 and enters the discharge mechanism 28 for distribution into the airstream 33 caused by the blower 36. The airstream 33, with the shredded blowing wool, exits the machine 10 at the machine outlet 32 and flows through the distribution hose 46, as shown in FIG. 3, toward the insulation cavity, not shown.

As previously discussed and as shown in FIG. 4, the discharge mechanism 28 is configured to distribute the finely shredded blowing wool into the airstream 33. In this embodiment, the discharge mechanism 28 is a rotary valve. Alternatively, the discharge mechanism 28 can be any other mechanism including staging hoppers, metering devices, or rotary feeders, sufficient to distribute the shredded blowing wool into the airstream 33.

In this embodiment as further shown in FIG. 4, the low speed shredders 24a and 24b rotate in a counter-clockwise direction r1 and the agitator 26 rotates in a counter-clockwise direction r2. Rotating the low speed shredders 24a and 24b and the agitator 26 in the same counter-clockwise direction allows the low speed shredders 24a and 24b and the agitator 26 to shred and pick apart the blowing wool while substantially preventing an accumulation of unshredded or partially shredded blowing wool in the shredding chamber 23. In another embodiment, the low speed shredders 24a and 24b and the agitator 26 each could rotate in a clock-wise direction or the low speed shredders 24a and 24b and the agitator 26 could rotate in different directions provided the relative rotational directions allow finely shredded blowing wool to be fed into the discharge mechanism 28 while preventing a substantial accumulation of unshredded or partially shredded blowing wool in the shredding chamber 23.

In this embodiment as shown FIG. 4, the shredding chamber 23 includes a plurality of guide shells 120, 122 and 124. The upper left guide shell 120 is positioned partially around the low speed shredder 24a and extends to form an arc of approximately 90°. The upper left guide shell 120 has an upper left guide shell inner surface 121. The upper left guide shell 120 is configured to allow the low speed shredder 24a to seal against the upper left guide shell surface 121 and thereby direct the blowing wool in a downstream direction as the low speed shredder 24a rotates.

In a similar manner as the upper left guide shell 120, the upper right guide shell 122 is positioned partially around the low speed shredder 24b and extends to form an arc of approximately 90°. The upper right guide shell 122 has an upper right guide shell inner surface 123. The upper right guide shell 122 is configured to allow the low speed shredder 24b to seal against the upper right guide shell inner surface 123 and thereby direct the blowing wool in a downstream direction as the low speed shredder 24b rotates.

In a manner similar to the upper guide shells 120 and 122, the lower guide shell 124 is positioned partially around the agitator 26 and extends to form an approximate semi-circle. The lower guide shell 124 has a lower guide shell inner surface 125. The lower guide shell 124 is configured to allow the agitator 26 to seal against the lower guide shell inner surface 125 and thereby direct the blowing wool in a downstream direction as the agitator 26 rotates.

In this embodiment, the upper guide shell inner surfaces 121 and 123, and the lower guide shell inner surface 125 are made of high density polyethylene (hdpe) configured to provide a lightweight, low friction guide for the blowing wool. Alternatively, the upper guide shell inner surfaces 121 and 123, and the lower guide shell inner surface 125 can be made of other materials, such as aluminum, sufficient to provide a sealing surface that allows the low speed shredders 24a, 24b or the agitator 26 to direct the blowing wool downstream.

In this embodiment, the upper guide shells 120 and 122 are curved and extend to form an arc of approximately 90°. In another embodiment, the upper guide shells 120 and 122 may be curved and extend to form an arc which is more or less than 90°, such that the upper guide shells 120 and 122 are sufficient to allow the low speed shredders 24a and 24b to seal against the upper guide shell surfaces 121 and 123, thereby directing the blowing wool in a downstream direction as the low speed shredders 24a and 24b rotate. Similarly in this embodiment, the lower guide shell 124 is curved and extends to form an approximate semi-circle. In another embodiment, the lower guide shell 124 may be curved and extend to form an arc which is more or less than a semi-circle, such that the lower guide shell 124 is sufficient to allow the agitator 26 to seal against the lower guide shell surface 125, thereby directing the blowing wool in a downstream direction as the agitator 26 rotates.

As previously discussed and as shown in FIG. 2, the shredding chamber 23 includes a plurality of low speed shredders 24a and 24b and an agitator 26. As shown in FIG. 5, the low speed shredders 24a and 24b include adjacent, parallel shredder shafts 130a and 130b, respectively. The shredder shafts 130a and 130b are configured to rotate within the shredding chamber 23 and are fitted with a plurality of paddle assemblies 134. In this embodiment, the shredder shafts 130a and 130b are made of steel, although the shredder shafts 130a and 130b can be made of other materials, including aluminum or plastic, sufficient to rotate within the shredding chamber 23 and to be fitted with paddle assemblies 134. In this embodiment as shown in FIG. 5, the low speed shredders 24a and 24b each have four paddle assemblies 134 extending perpendicular from the shredder shafts 130a and 130b. In another embodiment, the low speed shredder shafts 130a and 130b each can have more than four paddle assemblies 134 or any number of paddle assemblies 134 sufficient to shred and pick apart the blowing wool.

As further shown in FIG. 5, low speed shredder shaft 130a has a first paddle assembly 134a and adjacent low speed shredder shaft 130b has a second paddle assembly 134b. The first paddle assembly 134a has a major axis a extending along the length of the first paddle assembly 134a. Similarly, the second paddle assembly 134b has a major axis b extending along the length of the second paddle assembly 134b. In this embodiment, the major axis a of the first paddle assembly 134a is substantially perpendicular to the major axis b of the second paddle assembly 134b. The first paddle assembly 134a and the second paddle assembly 134b correspond to each other since they rotate in the same vertical plane. Similarly, the remaining paddle assemblies 134 disposed on the low speed shredder shaft 130a have major axis that are substantially perpendicularly positioned relative to the major axis of their corresponding paddle assemblies 134 disposed on the low speed shredder shaft 130b. The perpendicular alignment of the corresponding paddle assemblies 134a and 134b allows the low speed shredders 24a and 24b to effectively shred and pick apart the blowing wool and prevent heavy clumps of blowing wool from moving past the shredders 24a and 24b into the agitator 26 thereby preventing an accumulation of blowing wool. It can be seen that paddle assembly 134a on low speed shredder shaft 130a and its corresponding paddle assembly 134b on the adjacent low speed shredder shaft 130b have an indexed arrangement such that they do not interfere with each other and provide better shredding as they rotate.

As previously discussed and as shown in FIG. 6, the low speed shredders 24a and 24b include shredder shafts 130a and 130b and a plurality of paddle assemblies 134. As best shown in FIG. 7, the shredder shafts 130a and 130b are hollow rods having a plurality of flat faces 132 and alternate tangs 133 extending substantially along the length of the shredder shafts 130a and 130b. Referring again to FIG. 6, each paddle assembly 134 includes a blade 136 and two paddles 138. In this embodiment as shown in FIG. 8, the blade 136 is a flat member with a hole 140 and two mounting arms 142. The paddles 138 are fastened to the mounting arms 142 by rivets 144 as shown in FIG. 6. Alternatively, the paddles 138 can be fastened to the mounting arms 142 by other fastening methods including adhesive, clips, clamps, or by other fastening methods sufficient to attach the paddles 138 to the mounting arms 142. The blades 136 include T-shaped projections 146 positioned within the hole 140. In this embodiment as shown in FIG. 8, each paddle assembly 134 includes a blade 136 having two mounting arms 142 suitable for attaching the paddles 138. In another embodiment, each paddle assembly 134 can include more or less than two mounting arms 142, each having a paddle 138 attached to the mounting arm 142, such that the paddle assemblies 134 effectively shred and pick apart the blowing wool.

The blades 136 and the paddles 138 are mounted to the shredder shafts 130a and 130b by sliding the T-shaped projections 146 of the blades 136 onto the flat faces 132 of the shredder shafts 130a and 130b. The paddle assemblies 134, made up of the blades 136 and the paddles 138 and positioned on the shredder shafts 130a and 130b, have a major axis c which is substantially perpendicular to the shredder shafts 130a and 130b as shown in FIG. 5. Once the blades 136 and the paddles are positioned in the desired location along the shredder shafts 130a and 130b, the mounting arms 142 of the blades 136 are twisted, such that the T-shaped projections 146 of the blades 136 deform within the alternate tangs 133 of the shredder shafts 130a and 130b thereby locking the blades 136 and the paddles 138 in position.

As further shown in FIG. 5, the twisted blades 136 and paddles 138 form an axis f. The axis f forms an acute angle e relative to a major axis of the shredder shaft 130b. In this embodiment, acute angle e is approximately 40°-50°. By having acute angle e at approximately 40°-50°, the blades 136 and paddles 138 efficiently shred and pick apart the blowing wool. While in this embodiment, the acute angle e is approximately 40°-50°, in another embodiment, the acute angle e may be more than 40°-50° or less than 40°-50° provided that the paddle assemblies 134 can efficiently shred and pick apart the blowing wool.

As previously discussed and as shown in FIG. 5, the low speed shredders 24a and 24b include paddle assemblies 134, each paddle assembly having a plurality of paddles 138. In this embodiment, the paddles 138 are made of rubber and have a hardness rating of 60 A to 70 A Durometer. A hardness rating of between 60 A to 70 A allows the paddles 138 to effectively grip the blowing wool for shredding while preventing jamming of the blowing wool in the shredders 24a and 24b. Optionally, the paddles 138 can have a hardness greater than 70 A or less than 60 A. In another embodiment, the paddles 138 can be made of other materials, such as aluminum or plastic, sufficient to effectively grip the blowing wool for shredding while preventing jamming of blowing wool in the shredders 24a and 24b.

As further shown in FIG. 5, the low speed shredders 24a and 24b include a plurality of paddle assemblies 134 mounted to shredder shafts 130a and 130b. The plurality of paddle assemblies 134 are mounted on each shredder shaft 130a and 130b such that adjacent paddle assemblies 134 on the same shredder shaft 130a or 130b are offset from each other by an angle t as best shown in FIG. 2. Offsetting the paddle assemblies 134, from each other, on the shredder shafts 130a and 130b allows the paddle assemblies 134 to effectively grip the blowing wool for shredding while preventing jamming of the blowing wool in the shredders 24a and 24b. In this embodiment as shown in FIG. 2, the adjacent paddle assemblies 134 are offset by an angle t of approximately 60°. In another embodiment, the angle of offset can be any angle, such as an angle t within the range of from about 45° to about 90°, sufficient to effectively grip the blowing wool for shredding while preventing jamming of the blowing wool in the shredders 24a and 24b.

As discussed above and shown in FIG. 5, the low speed shredders 24a and 24b include a plurality of paddle assemblies 134 mounted to shredder shafts 130a and 130b. In this embodiment, the shredder shafts 130a and 130b are substantially physically identical. Similarly, the paddle assemblies 134 mounted to the shredder shafts 130a and 130b are substantially physically identical and mounted to the respective shredder shafts 130a and 130b in the same manner. The shredders 24a and 24b are assembled to be identical for ease of replacement and also to be interchangeable. The term “interchangeable”, as used herein, is defined to mean that shredder 24a can be replaced with shredder 24b and vice versa. It is to be understood that the shredder shafts 130a and 130b can be different. Similarly, in another embodiment, the shredders 24a and 24b can be different.

As previously discussed and as shown in FIGS. 4 and 9, the shredded blowing wool exits the low speed shredders 24a and 24b and drops into the agitator 26 for final shredding. In this embodiment as best shown in FIG. 9, the agitator 26 rotates in a counter-clockwise direction r2 and forces the finely shredded blowing wool in direction d toward a side inlet 92 of the discharge mechanism 28 for distribution into the airstream 33. A baffle 110 is positioned between the agitator 26 and the side inlet 92 of the discharge mechanism 28. The baffle 110 can be molded into the lower guide shell 124, or can be mounted to the lower unit 12 by any fastening method, including, screws, clamps, clips or any fastening method sufficient to mount the baffle 110 to the lower unit 12.

The baffle 110 is configured to partially obstruct the side inlet 92 of the discharge mechanism 28. By partially obstructing the side inlet 92 of the discharge mechanism 28, the baffle 110 allows finely shredded blowing wool to enter the side inlet 92 of the discharge mechanism 28 and directs heavy clumps of blowing wool upward past the side inlet 92 of the discharge mechanism 28 to the low speed shredders 24a and 24b for recycling and further shredding.

In this embodiment, the baffle 110 has a triangular cross-sectional shape. Alternatively, the baffle 110 can have any cross-sectional shape sufficient to allow finely shredded blowing wool to enter the side inlet 92 of the discharge mechanism 28 and to direct heavy clumps of blowing wool past the side inlet 92 of the discharge mechanism 28 to the low speed shredders 24a and 324b for recycling.

As further shown in FIG. 9, the baffle 110 has a height h which extends to partially obstruct the side inlet 92 of the discharge mechanism 28. In this embodiment, the height h of the baffle 110 extends approximately 20% of the length l of the side inlet 92. Alternatively, the height h of the baffle 110 can extend to any height sufficient to allow finely shredded blowing wool to enter the side inlet 92 of the discharge mechanism 28 and to direct heavy clumps of blowing wool past the side inlet 92 of the discharge mechanism 28 to the low speed shredders 24a and 24b for recycling.

The principle and mode of operation of this blowing wool machine have been described in its preferred embodiments. However, it should be noted that the blowing wool machine may be practiced otherwise than as specifically illustrated and described without departing from its scope.

Claims

1. A machine comprising: a chute having an inlet end, the inlet end configured to receive a bag of compressed blowing wool;a shredding chamber associated with the chute, the shredding chamber including a plurality of shredders configured to receive the blowing wool exiting the chute and further configured to shred and pick apart the blowing wool and an agitator, the agitator positioned to receive the shredded and picked apart blowing wool from the shredders and further configured to prepare the blowing wool for distribution into an airstream, the plurality of shredders and the agitator configured for rotation, each of the shredders having a plurality of paddle assemblies connected to a shaft; anda discharge mechanism mounted to receive the shredded and picked apart blowing wool from the agitator and further configured to distribute the blowing wool into an airstream;wherein in operation, the rotational speed of the agitator is higher than the rotational speed of the shredders.

2. The machine of claim 1, wherein the plurality of shredders are configured to rotate at the same speed.

3. The machine of claim 1, wherein the plurality of shredders and the agitator are configured to rotate in the same direction.

4. The machine of claim 3, wherein the plurality of shredders and the agitator are configured to rotate in a counter-clockwise direction.

5. The machine of claim 1, wherein the shredders and the agitator are mounted on rotatable shafts, and wherein the shredder shafts and the agitator shafts are generally parallel to each other.

6. The machine of claim 5, wherein the shredder shafts are substantially physically identical to each other so as to be interchangeable.

7. The machine of claim 5, wherein the shredder shafts are offset from each other in a vertical direction.

8. The machine of claim 1, wherein the shredders rotate at a speed in a range of from about 40 rpm to about 80 rpm.

9. The machine of claim 1, wherein the agitator rotates at a speed in a range of from about 300 rpm to about 500 rpm.