Ball mill for treating used casting sand
United States Patent 3862719
A ball mill for treating and washing used casting sand has a drum that includes an interior and exterior wall. The space between these interior and exterior walls form an intermediate chamber. Disposed along the exterior wall is a screen through which passes the treated sand. The drum may be positioned on an inclination with repect to the horizontal and has contained within its interior a plurality of mill balls. Feeding means are placed at, and comprise one end of the drum. The feeding means are placed so as to be concentric about the central longitudinal axis of the drum. Means are placed within the intermediate chamber to subdivide it into compartments. A continuously operating discharge means is disposed at, and comprises the other end of the drum so that the metallic residue of the casting sand migrates towards the discharge means and exits thereat as the drum revolves.
US Patent References:
/1242423.html
Cover - October 1917 - 1242423
Ball mill with risers on liners to throw balls and oversize material towards feed end of mill and to progress smaller balls and fine material towards discharge end of mill
Daman - April 1956 - 2743060
Ball mill discharge trommel
Velcheff - April 1965 - 3180581
MEDIA MILL
Mosby - December 1970 - 3545687
/1242423.html
Cover - October 1917 - 1242423
Ball mill with risers on liners to throw balls and oversize material towards feed end of mill and to progress smaller balls and fine material towards discharge end of mill
Daman - April 1956 - 2743060
Ball mill discharge trommel
Velcheff - April 1965 - 3180581
MEDIA MILL
Mosby - December 1970 - 3545687
Application Number:
05/356984
Publication Date:
01/28/1975
Filing Date:
05/03/1973
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
241/183, 241/DIG.010, 241/180
International Classes:
B22C5/04; B22C5/06; B22C5/00; B02C17/06; B07B1/24
Field of Search:
241/74,170-172,176,178-180,181,183,DIG.10 209/289,290,291,299,34 164/5
Primary Examiner:
Lake, Roy
Assistant Examiner:
Desmond E. F.
Attorney, Agent or Firm:
Collard, Allison C.
Claims:
I claim
1. A ball mill for recovering sand from a charge of used casting sand containing metallic residue comprising:
2. A ball mill as recited in claim 1 wherein the interior wall comprises a plurality of elongated inner bars disposed concentric to and about the central longitudinal axis of said drum, said plurality of inner bars disposed so as to define a plurality of slots disposed between adjacent edges of said inner bars for allowing the sand to pass therebetween.
3. A ball mill as recited in claim 3 wherein said means for longitudinally subdividing comprises a plurality of rings placed within the intermediate chamber formed between the interior and exterior walls and residing on the periphery of said plurality of inner bars, said rings subdividing the intermediate chamber into a plurality of intermediate screen chambers allowing the sand to pass therethrough.
4. A ball mill as recited in claim 4 and further comprising a plurality of helically-disposed guide pieces on the inside surfaces of said plurality of inner bars and wherein said drum is horizontally mounted so that as the drum rotates said plurality of helically-disposed guide pieces transport said charge towards said discharge means.
5. A ball mill as recited in claim 5 wherein said feeding means comprises a hollow shaft communicating with the interior of said drum and through which the used casting sand is fed.
6. A ball mill as recited in claim 5 wherein said plurality of inner bars is constructed and arranged to provide openings located within said discharge means and said openings are sized for passing said metallic residue while retaining said balls.
7. A ball mill as recited in claim 4 wherein said discharge means comprises:
1. A ball mill for recovering sand from a charge of used casting sand containing metallic residue comprising:
2. A ball mill as recited in claim 1 wherein the interior wall comprises a plurality of elongated inner bars disposed concentric to and about the central longitudinal axis of said drum, said plurality of inner bars disposed so as to define a plurality of slots disposed between adjacent edges of said inner bars for allowing the sand to pass therebetween.
3. A ball mill as recited in claim 3 wherein said means for longitudinally subdividing comprises a plurality of rings placed within the intermediate chamber formed between the interior and exterior walls and residing on the periphery of said plurality of inner bars, said rings subdividing the intermediate chamber into a plurality of intermediate screen chambers allowing the sand to pass therethrough.
4. A ball mill as recited in claim 4 and further comprising a plurality of helically-disposed guide pieces on the inside surfaces of said plurality of inner bars and wherein said drum is horizontally mounted so that as the drum rotates said plurality of helically-disposed guide pieces transport said charge towards said discharge means.
5. A ball mill as recited in claim 5 wherein said feeding means comprises a hollow shaft communicating with the interior of said drum and through which the used casting sand is fed.
6. A ball mill as recited in claim 5 wherein said plurality of inner bars is constructed and arranged to provide openings located within said discharge means and said openings are sized for passing said metallic residue while retaining said balls.
7. A ball mill as recited in claim 4 wherein said discharge means comprises:
Description:
This invention relates to a ball mill for treating or washing used casting sand. The ball mill essentially consists of a drum containing mill balls, whereby the jacket or casing of the drum has a double wall and is formed like a screen (sieve), and a feeding means for the material in the height of the drum axis.
Such devices treat or wash sand from foundries, separate core pins, as well as metal pieces from the sand. As is known, the sand molds which are used in foundries cannot be used again after the mold or cast is finished. The sand molds are merely remotely stored. However, valuable material is lost because these sand molds contain metal pieces and useable core sand.
It has been suggested to treat the used cores in a wet washing treatment in order to retrieve the core sand. However, the suggested methods have failed because of the size of the installation required and the high costs involved.
Another device is known from U.S. Pat. No. 2,835,941 which crushes the agglomerate core sand by means of large balls. These balls are contained in a double walled rotating drum, whereby the face of the jacket or casing is provided with slots and partly with screens or sieves. While the sand drops into a container, the remaining core pins and residue are separately discharged at the periodic return movement of the drum. However, a disadvantage of this device is that it does not operate continuously, but must be interrupted periodically in order to discharge the residue.
A mold sand treatment or washing installation is known from German Pat. No. 425,713. In this disclosure screen or sieve drums are concentrically disposed one about the other. The screen drums are surrounded by a jacket or casing. These drums are formed in a polygon-like manner and are mounted eccentrically on a rotating shaft. The shaft rotates counterclock-wise with respect to the rotation of the jacket. On the outer circumference of the outer screen, oblique transport shovels, paddles and kneading means are provided. A ball mill having a screen type jacket is provided in the end of the inner screen drum and is larger in its diameter. However, this device is not really a ball mill in the conventional sense, but a device in which different operating steps for making mold sand are combined. The ball mill itself is in the shape of a cylinder and the balls are in the inside of the cylinder. This device does not permit a continuous mode of operation.
And, a mixing drum for sand treatment is known from German Petty Pat. No. 1,905,629. This patent teaches the use of a cylindrical body wherein heavy ball-like mill bodies are provided. The sand is fed into the device on one side together with the desired binder and drops through a screen on the opposite end. In this drum only sand, already milled, can be used and it must be separated from all residue. In order to pick up agglomerates, while simultaneously obtaining an even coating of the granules by the binder, this device merely crushes or kneads the sand in any suitable manner.
The present invention overcomes the disadvantages of the aforementioned devices by discharging the residue or remains in a continuous manner. This is achieved by utilizing a drum jacket or casing having an inclination with respect to the horizontal. The apparatus includes intermediate chambers which are longitudinally or axially subdivided. A continuously operating ring-like discharge opening for the noncrushable residue is provided opposite the feeding portion of the drum.
The ball mill according to the present invention is further characterized in that a hollow cylinder is provided as the discharge means for the residue.
In another embodiment of the inventive ball mill, the drum may be provided with its jacket or casing face disposed horizontally. In addition, the apparatus places a plurality of rings between the inner bars of the drum and the outer screen or sieve thus subdividing the drum intermediate screen chamber into a plurality of sections. A return transport bar is mounted for each section.
In the subject disclosure the material is fed through a hollow drum shaft. Guiding pieces are mounted on the inner bars of the drum. A double walled drum, partly containing a defined size of balls is charged at the feed opening through a funnel and hollow shaft. The drum is mounted with an inclination descending toward the discharge opening. A plate is provided at the front face of the discharge opening, leaving a ring-like opening between the inner walls of the drum and the edge of the plate. This ring-like opening is such that balls cannot pass through. Consequently, the drum has a drum end section or zone into which the residue and the core pins of the sand may enter, but in which no balls are present. In this end section or zone the jacket face has openings so that the residue falls out radially. This is particularly advantageous for the adjacent drive. The drum is subdivided into a number of sections, which reach to the end section of the drum, by a plurality of outer rings arranged over the inner jacket bars. Above this a screen jacket is mounted having defined screen mesh sizes. Sand and residue up to a defined size can fall through the slots of the inner jacket. Sand which is smaller in diameter than the mesh size of the screen falls through the screen for recycling. Larger parts are thrown back into the inner chamber of the drum through an opening at each rotation of the drum. The balls again crush these parts which then travel along the descending incline towards the discharge opening. Owing to repeated screening in the radial sections, increasing amounts of sand are screened out. Eventually the residue arrives at the last drum section or zone where they are discharged. Accordingly, sand clumps will be completely crushed and the metal parts will be freed from sand. Thus, continuous and economical sand recycling is assured. Owing to a link dust removal installation, the sand may be removed for immediate use.
For material having a relatively high temperature the drum may be mounted on rollers. The rollers of the bearing at the discharge opening are supported by an axial pressure bearing. However, the rollers at the charge openings are not provided with axial pressure bearings. This type of bearing can be adjusted to the desired requirements.
In another embodiment of the invention the drum is mounted horizontally and the guide sheet metal is mounted on the inner wall bars, for guiding the material in the direction of the drum end section (zone). This sheet metal is mounted helically on these inner wall bars.
In a further embodiment of the inventive ball mill, the inner wall bars in the end section of the drum have openings. These are sized so that the residue will be discharged but not the mill balls. In this embodiment, material is fed through a hopper and a hollow shaft into the inner drum chamber. The inner drum chamber is mounted without an incline but has a double wall and is cylindrical and partly filled with balls.
The material is crushed by the balls until it falls through the slots of the inner screen jacket upon reaching the proper mesh size. Or, the material is transported by the sheet metal guides in the direction of the drum end section. In this end section an additional section or zone is provided having no outer screen, but has openings through which the residue may fall. The openings are of smaller size to block the balls. Consequently, sand is screened out of the material and the residue is discharged at the end of the drum. Mounting the drum horizontally avoids special incline mounts for its support bearings. Construction and assembly of the drum according to the invention is substantially facilitated.
It is therefore an object of the present invention to provide an apparatus for treating sand molds used in sand castings.
It is another object of the present invention to provide an apparatus for continually discharging the separated materials and to provide an apparatus that is efficient in operation and simple in design.
Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings which disclose the embodiments of the invention. It is to be understood, however, that the drawings are designed for the purpose of illustration only and not as a definition of the limits of the invention.
In the drawings wherein similar reference characters denote similar elements throughout the several views:
FIG. 1 is a broken side view of the inventive apparatus;
FIG. 2 is a sectional view of the device of FIG. 1 taken on the line I--I of FIG. 1 through the last chamber from the discharge opening to the charge opening;
FIG. 3 is a roller bearing in a side view;
FIG. 4 is a simplified roller bearing in a front view;
FIG. 5 is a broken side view of another embodiment of the invention having a horizontally mounted drum; and
FIG. 6 is the device taken along section A-B of FIG. 5.
Referring now to FIGS. 1 and 2, a drive 1, shown in part, revolves the drum in direction D. The outer periphery of the drum forms a screen casing 2 which encompasses drum rings 3 up to a discharge chamber 8. An inner casing comprises inner bars 13 and the return guide bars 15. These are mounted within drum rings 3 as shown. Discharge chamber 8 does not have a screen drum and also lacks two inner wall bars 13 and the return bar 15, so that large metal parts and large materials may be discharged.
Free spaces are provided between the inner jacket bars 13 to form slots 14 through which material falls when having a diameter which is smaller than the width of slots 14. The material which falls through the mesh of screen drum 2 falls into sand funnel 16a with a discharge opening 16. Larger material is thrown back into the inner chamber of the drum by return guide bars 15 as the drum revolves. The material is further crushed by balls 12 and travels slowly toward the discharge chamber 8 due to drum inclination angle A as seen in FIG. 1. While traveling in the direction B, the material falls into ring-like screen chambers 4. Consequently, more and more sand is removed, and finally only the larger pieces and the desired metal pieces reach discharge chamber 8.
Material 7 which at the beginning is contaminated with sand is poured into hopper 6. It is fed through the hollow shaft 5 and into the drum.
After the material travels as above-described from the drum center in direction B it reaches intermediate annular gap C formed by annular plate 9. Brackets 9a support plate 9 as shown. Gap C is of a size small enough for preventing balls 12 from passing through. In discharge chamber 8 material 10 falls through annular gap C defined by plate 9 and out through chute 11. By combining dust removal chamber 16a with the sand hopper 16, reusable sand may be continuously removed. It is obvious that efficient separation of sand from the residue is realized. The inventive apparatus achieves high capacity and continuously discharges the sand and residue. Accordingly the invention meets the requirement that it operate continuously and need not be stopped for emptying the residue.
In special cases guide pieces 17 or 18 or a combination thereof (shown in outline) may be mounted on the inner casing bars 13 in order to obtain the desired openings or rotational characteristics, or both.
Referring now to FIGS. 5 and 6 a ball mill is shown having the drum in a horizontal position. Additional sheet metal guide pieces 21 are mounted helically on the inner casing bars 13 so that material 7 is moved from hopper 6 in direction C as shown. The material 7 is crushed by balls 12 until one part falls through screen 2 into hopper 16. The part which does not fall into the funnel 16, but remains on screen 2, is thrown back into the inner chamber of the drum by means of return guides 15 and is again crushed. Material which cannot be crushed, for example, core pins or metal parts 10 are moved by the guide bars 21 in the direction of C and fall downwardly through recesses 20 into hopper 11. The openings 20 are sized so that only residue parts 10 can fall through. Mill balls 12 are too large to pass through apertures 20 and remain in the drum.
Referring now to FIGS. 3 and 4 there is shown the bearing mount used for supporting end shaft 22. The mount is used if the material entering the apparatus is at a high temperature.
Bearings 25 disposed on frame 26a and supporting shaft 22 would be placed on the apparatus of FIGS. 1, 2, 5, and 6. In use, frame 26a would replace frame 26 and associated bearings of FIGS. 1 and 6 so that a shaft neck 23 of shaft 22 would ride the periphery of roller bearings 25 as seen in FIG. 3. To prevent axial movement of shaft 22 and, consequently, the inventive ball mill, shoulder 23a of shaft 22 thrusts against a side of bearing 25 as shown. Axial pressure bearing 24 engages the other side of bearing 25, so that bearing 24 acts as a rotatable thrust support. As shown the entire bearing apparatus is supported on frame 26a.
While only several embodiments of the present invention have been shown and described, it will be apparent to those persons skilled in the art that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention.
Such devices treat or wash sand from foundries, separate core pins, as well as metal pieces from the sand. As is known, the sand molds which are used in foundries cannot be used again after the mold or cast is finished. The sand molds are merely remotely stored. However, valuable material is lost because these sand molds contain metal pieces and useable core sand.
It has been suggested to treat the used cores in a wet washing treatment in order to retrieve the core sand. However, the suggested methods have failed because of the size of the installation required and the high costs involved.
Another device is known from U.S. Pat. No. 2,835,941 which crushes the agglomerate core sand by means of large balls. These balls are contained in a double walled rotating drum, whereby the face of the jacket or casing is provided with slots and partly with screens or sieves. While the sand drops into a container, the remaining core pins and residue are separately discharged at the periodic return movement of the drum. However, a disadvantage of this device is that it does not operate continuously, but must be interrupted periodically in order to discharge the residue.
A mold sand treatment or washing installation is known from German Pat. No. 425,713. In this disclosure screen or sieve drums are concentrically disposed one about the other. The screen drums are surrounded by a jacket or casing. These drums are formed in a polygon-like manner and are mounted eccentrically on a rotating shaft. The shaft rotates counterclock-wise with respect to the rotation of the jacket. On the outer circumference of the outer screen, oblique transport shovels, paddles and kneading means are provided. A ball mill having a screen type jacket is provided in the end of the inner screen drum and is larger in its diameter. However, this device is not really a ball mill in the conventional sense, but a device in which different operating steps for making mold sand are combined. The ball mill itself is in the shape of a cylinder and the balls are in the inside of the cylinder. This device does not permit a continuous mode of operation.
And, a mixing drum for sand treatment is known from German Petty Pat. No. 1,905,629. This patent teaches the use of a cylindrical body wherein heavy ball-like mill bodies are provided. The sand is fed into the device on one side together with the desired binder and drops through a screen on the opposite end. In this drum only sand, already milled, can be used and it must be separated from all residue. In order to pick up agglomerates, while simultaneously obtaining an even coating of the granules by the binder, this device merely crushes or kneads the sand in any suitable manner.
The present invention overcomes the disadvantages of the aforementioned devices by discharging the residue or remains in a continuous manner. This is achieved by utilizing a drum jacket or casing having an inclination with respect to the horizontal. The apparatus includes intermediate chambers which are longitudinally or axially subdivided. A continuously operating ring-like discharge opening for the noncrushable residue is provided opposite the feeding portion of the drum.
The ball mill according to the present invention is further characterized in that a hollow cylinder is provided as the discharge means for the residue.
In another embodiment of the inventive ball mill, the drum may be provided with its jacket or casing face disposed horizontally. In addition, the apparatus places a plurality of rings between the inner bars of the drum and the outer screen or sieve thus subdividing the drum intermediate screen chamber into a plurality of sections. A return transport bar is mounted for each section.
In the subject disclosure the material is fed through a hollow drum shaft. Guiding pieces are mounted on the inner bars of the drum. A double walled drum, partly containing a defined size of balls is charged at the feed opening through a funnel and hollow shaft. The drum is mounted with an inclination descending toward the discharge opening. A plate is provided at the front face of the discharge opening, leaving a ring-like opening between the inner walls of the drum and the edge of the plate. This ring-like opening is such that balls cannot pass through. Consequently, the drum has a drum end section or zone into which the residue and the core pins of the sand may enter, but in which no balls are present. In this end section or zone the jacket face has openings so that the residue falls out radially. This is particularly advantageous for the adjacent drive. The drum is subdivided into a number of sections, which reach to the end section of the drum, by a plurality of outer rings arranged over the inner jacket bars. Above this a screen jacket is mounted having defined screen mesh sizes. Sand and residue up to a defined size can fall through the slots of the inner jacket. Sand which is smaller in diameter than the mesh size of the screen falls through the screen for recycling. Larger parts are thrown back into the inner chamber of the drum through an opening at each rotation of the drum. The balls again crush these parts which then travel along the descending incline towards the discharge opening. Owing to repeated screening in the radial sections, increasing amounts of sand are screened out. Eventually the residue arrives at the last drum section or zone where they are discharged. Accordingly, sand clumps will be completely crushed and the metal parts will be freed from sand. Thus, continuous and economical sand recycling is assured. Owing to a link dust removal installation, the sand may be removed for immediate use.
For material having a relatively high temperature the drum may be mounted on rollers. The rollers of the bearing at the discharge opening are supported by an axial pressure bearing. However, the rollers at the charge openings are not provided with axial pressure bearings. This type of bearing can be adjusted to the desired requirements.
In another embodiment of the invention the drum is mounted horizontally and the guide sheet metal is mounted on the inner wall bars, for guiding the material in the direction of the drum end section (zone). This sheet metal is mounted helically on these inner wall bars.
In a further embodiment of the inventive ball mill, the inner wall bars in the end section of the drum have openings. These are sized so that the residue will be discharged but not the mill balls. In this embodiment, material is fed through a hopper and a hollow shaft into the inner drum chamber. The inner drum chamber is mounted without an incline but has a double wall and is cylindrical and partly filled with balls.
The material is crushed by the balls until it falls through the slots of the inner screen jacket upon reaching the proper mesh size. Or, the material is transported by the sheet metal guides in the direction of the drum end section. In this end section an additional section or zone is provided having no outer screen, but has openings through which the residue may fall. The openings are of smaller size to block the balls. Consequently, sand is screened out of the material and the residue is discharged at the end of the drum. Mounting the drum horizontally avoids special incline mounts for its support bearings. Construction and assembly of the drum according to the invention is substantially facilitated.
It is therefore an object of the present invention to provide an apparatus for treating sand molds used in sand castings.
It is another object of the present invention to provide an apparatus for continually discharging the separated materials and to provide an apparatus that is efficient in operation and simple in design.
Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings which disclose the embodiments of the invention. It is to be understood, however, that the drawings are designed for the purpose of illustration only and not as a definition of the limits of the invention.
In the drawings wherein similar reference characters denote similar elements throughout the several views:
FIG. 1 is a broken side view of the inventive apparatus;
FIG. 2 is a sectional view of the device of FIG. 1 taken on the line I--I of FIG. 1 through the last chamber from the discharge opening to the charge opening;
FIG. 3 is a roller bearing in a side view;
FIG. 4 is a simplified roller bearing in a front view;
FIG. 5 is a broken side view of another embodiment of the invention having a horizontally mounted drum; and
FIG. 6 is the device taken along section A-B of FIG. 5.
Referring now to FIGS. 1 and 2, a drive 1, shown in part, revolves the drum in direction D. The outer periphery of the drum forms a screen casing 2 which encompasses drum rings 3 up to a discharge chamber 8. An inner casing comprises inner bars 13 and the return guide bars 15. These are mounted within drum rings 3 as shown. Discharge chamber 8 does not have a screen drum and also lacks two inner wall bars 13 and the return bar 15, so that large metal parts and large materials may be discharged.
Free spaces are provided between the inner jacket bars 13 to form slots 14 through which material falls when having a diameter which is smaller than the width of slots 14. The material which falls through the mesh of screen drum 2 falls into sand funnel 16a with a discharge opening 16. Larger material is thrown back into the inner chamber of the drum by return guide bars 15 as the drum revolves. The material is further crushed by balls 12 and travels slowly toward the discharge chamber 8 due to drum inclination angle A as seen in FIG. 1. While traveling in the direction B, the material falls into ring-like screen chambers 4. Consequently, more and more sand is removed, and finally only the larger pieces and the desired metal pieces reach discharge chamber 8.
Material 7 which at the beginning is contaminated with sand is poured into hopper 6. It is fed through the hollow shaft 5 and into the drum.
After the material travels as above-described from the drum center in direction B it reaches intermediate annular gap C formed by annular plate 9. Brackets 9a support plate 9 as shown. Gap C is of a size small enough for preventing balls 12 from passing through. In discharge chamber 8 material 10 falls through annular gap C defined by plate 9 and out through chute 11. By combining dust removal chamber 16a with the sand hopper 16, reusable sand may be continuously removed. It is obvious that efficient separation of sand from the residue is realized. The inventive apparatus achieves high capacity and continuously discharges the sand and residue. Accordingly the invention meets the requirement that it operate continuously and need not be stopped for emptying the residue.
In special cases guide pieces 17 or 18 or a combination thereof (shown in outline) may be mounted on the inner casing bars 13 in order to obtain the desired openings or rotational characteristics, or both.
Referring now to FIGS. 5 and 6 a ball mill is shown having the drum in a horizontal position. Additional sheet metal guide pieces 21 are mounted helically on the inner casing bars 13 so that material 7 is moved from hopper 6 in direction C as shown. The material 7 is crushed by balls 12 until one part falls through screen 2 into hopper 16. The part which does not fall into the funnel 16, but remains on screen 2, is thrown back into the inner chamber of the drum by means of return guides 15 and is again crushed. Material which cannot be crushed, for example, core pins or metal parts 10 are moved by the guide bars 21 in the direction of C and fall downwardly through recesses 20 into hopper 11. The openings 20 are sized so that only residue parts 10 can fall through. Mill balls 12 are too large to pass through apertures 20 and remain in the drum.
Referring now to FIGS. 3 and 4 there is shown the bearing mount used for supporting end shaft 22. The mount is used if the material entering the apparatus is at a high temperature.
Bearings 25 disposed on frame 26a and supporting shaft 22 would be placed on the apparatus of FIGS. 1, 2, 5, and 6. In use, frame 26a would replace frame 26 and associated bearings of FIGS. 1 and 6 so that a shaft neck 23 of shaft 22 would ride the periphery of roller bearings 25 as seen in FIG. 3. To prevent axial movement of shaft 22 and, consequently, the inventive ball mill, shoulder 23a of shaft 22 thrusts against a side of bearing 25 as shown. Axial pressure bearing 24 engages the other side of bearing 25, so that bearing 24 acts as a rotatable thrust support. As shown the entire bearing apparatus is supported on frame 26a.
While only several embodiments of the present invention have been shown and described, it will be apparent to those persons skilled in the art that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention.