US1096199A - Screw-press. - Google Patents

Description

T. 0. SOHUYLER. SCREW PRESS.

APPLICATION FILED P113127. 1913.

1,096,199. Patented May12,1914.

2 SHEETS-SHEET 1.

um/Mo's IE TATE ATENT FFIC,

THOMAS C. SGHUYLER, OF BROOKLYN, NEW YORK, ASSIGNOR TO LOG-AN IRON WORKS, OF BROOKLYN, NEW YORK, A CORPORATION OF NEW YORK.

SCREW-PRESS.

Specification of Letters Patent.

Patented May 12, 1914:-

Application filed February 27, 1913. Serial No. 751,119.

time prevent the jamming of the material passing through the press, at the section of high pressure. Second, to properly devise and arrange the different parts of the press,- so that the frictional forces are so applied and related to each other with respect to the change of condition of the material, as it passes through the press, to permit the said material to be sub ected to greater pressures,

a larger range of drainage conditions, and at the same time enable material to be successfully operated upon and ethciently passed through machines, heretofore found impos-' sible in a screw press. Third, to devise means so as to create a difference of friction between the surface of the screw and sur-- rounding barrel in such a manner as to dispose and utilize this preponderance of friction on the surface where it will be correct as to the requirements of the material and ensuing conditions, and result in an improved and most efiicient screw pressing machine.

Other objects and advantages of the invention will appear from the detailed description.

The invention consists of structural features and relative arrangements of the several parts which will be hereinafter more fully described and particularly pointed out in the appended claims.

In the drawings in which similar reference characters indicate the same parts in the several figures of the drawings :F'igure 1 is a plan view of the press; Fi 2 is a longitudinal central section with a part of the helicoid broken away to show in sections, the stationary barrel; Fig. 3 is an end view, half in section on line III-III of Fig. 2, and the other half in elevation; Fig. i is a longitudinal section on an enlarged scale of a portion of the outer barrel or casing; Fig.

5 is an enlarged cross section of a portion of barrel at joint rib; and Fig. 6 is an enlarged perspective view of a strainer bar.

In screw presses as generally designed, the machine depends principally upon friction for the proper operation of its purpose. There have been introduced in the construction of presses auxiliary and extraneous mechanical means such as internal grooves, slots, ad ustable bars, to change or assist the actlon of the press from that of indefinite and uncertain friction action to one or more positive means which have been found detrimental to the proper drainage of the mate rial passing through the press.

In screw presses, many varieties are found to exist, depending upon the nature of the material operated upon. Under changed conditions and after careful consideration and experimentation with many different kinds of material, it has been found that all fibrous, semi-granular, or any moisture containing materials, when under pressure in a mass, retain one important feature, that is,

that of equal unit pressure on any contact surface at right angles to that surface, similar to that of any true fluid, and this feature, under mechanical consideration of friction, indicates that if the coefiicient of friction of the material be taken at various pressures, certain frictional unit values will be obtained.

The amount of frictional adhesion to surfaces is directly proportional to the areas of surfaces considered, unit friction value being the same throughout, and to bring said friction to bear properly to the revealed relative frictional adhesive value of the different surfaces in a frictional machine of the type considered, and to use these values properly through correctly devised means, to the end of improved action in the machine on the material, will result in an improvement in preferably have its shortest dimension perpendicular to the drainage surfaces and the material is better drained when. not sheared over the drainage openings. It has been found that these conditions are incorporated in presses heretofore constructed only at a sacrifice of correct frictional eifort neces sary for the proper conveyance of the mate rial through the press, especially in the high pressure zone, and resulting in almost every case in a complete failure of efficient press action.

If we will take a section. of the screw press under high pressure, it will be found with material of uniform texture that said ma terial is exerting pressure on every section of the press surfaces and normal to such surfaces, some of the surfaces in the press being stationary and others movable relative to its longitudinal axis. Considering a section or mass of material for the length of one pitch of the screw, the outer surface of the material lies against the outer stationary conveying or drainage barrel and the annular surfaces and inner surfaces of material are in contact with the rotary screw. The material. under pressure according to the principle hereinbefore explained exerting equal unit pressure on all contact surfaces and therefore subject to the same coefficient of friction, thus giving for each unit of surface an equal frictional or ad hesive unit value. \Vith this assumption, it now remains to be determined whether the material when the screw is rotated, will have a greater adhesive or frictional effect in rotative direction on either the outer stationary barrel or on the rotary screw surface contained in the section of press length considered. For this purpose we may consider the mass of material acting as a whole, as experiment proves, except. in rare cases, that material under pressure presents greater resistance to internal shearing. Furthermore, the effect of each unit of frictional resistance on the stationary and movable surfaces in a press of the present type must be compared according to its distance from the axis of rotation of the moving part, and hence due to this fact, it will be seen that all does not depend entirely on relative friction area. when comparing effective adhesive values between the stationary and rotative surfaces of a screw press. In View of this condition and relation, it is possible to arrange the rotative surfaces so as to increase or diminish the frictional value in relation to that of the stationary surface friction value. and as will be described hereafter with. reference to the detailed description. This deduction of effective relative frictional values for part or whole of the press clearly points out that a decreased frictional effect on a rotative screw as compared to that on the barrel is the natural and only method to determine correctly the design of a screw press, and at the same time eliminate as much as is practical, all movable surfaces, particularly at the high pressure Zone. Conditions otherwise than cited in a screw pressare detrimental, for the reason that material will adhere to that surface having preponderance in effective frictional value, and when this is integral with the rotary screw in presses of the present type, the material relinquishes whatever frictional effect it has from the stationary part, is picked up by the rotary screw and made a. part of it, so to speak, thus forming the obstruction or jamming of the press, and furthermore the reason that presses of ordinary design happen to operate sometimes without jamming is due to the fact that they have at some part of their length, previous to the high pressure zone, enough preponderance in barrel frictional effect, to force the material beyond the jamming point under indeterminate conditions, and as the pressure of the material increases, this frictional preponderance in the barrel decreases. until such point is reached where it is more than balanced by screw frictional effect, which again results in jamming the press.

To include all the herewith described ad vantages and effect the operation recited, l have evolved a helicoidal rotary conveyer which operates around a stationary barrel. so that the frictional effect of the inner stationary barrel is added to the frictional effect of an. outer stationary barrel, whereby at each and every stage of progression, the material through the press is subjected to a proper conveyance force independent of the action or help from the material progrossing through at any other part of the press at the same instant, which action onables the material to be pressed to a degree depending entirely upon the strength of the press to withstand. it, and materially greater than. in a press where imperfect control is had.

Referring to the drawings, '1. represents a base frame and driving gear support, made of steel which supports in any suitable man nor an outer barrel made in halves, 2, 2', preferably internally tapered. composed of a series of circular ribs 3, and longitudinal tie bars 41-, said ribs 3 being spaced at intervals longitudinally best adapted to provide strength. 5, 5, are separated strainer bars made of metal. and of such a length as to span between two adjacent ribs 3, and each end of each bar is provided, as shown in Fig. 6, with a projecting face 6, and a notch or recess 7, said face 6 being set at a proper radial bevel so that the ends of each bar 5 will bear perfectly against the projecting face of the adjacent bar 5, when the projecting faces 6, are set circumferentially in the ribs 3, 3, after the manner of radial bricks in arch construction as shown in Fig. 4. To securely hold the bars 5, 5, to the ribs 3, there is provided a circular clamping band 8, made in section and secured to the ribs 3, 3, by radial bolts 9 which engage the notch or recess 7 as shown. The bolts 9 pass through registering holes in the band 8 and ribs 3, or between two dovetailed sections 3 and 3 secured together by a series of bolts 10, as shown in Fig. 4. The bars 5, 5, throughout their length except at ends where provided with projecting faces 6, are trapezoidal in section and hence when set up between the ribs 3, form expanding drainage slots as shown in Fig. 5, continuous for the length of the press, and the projecting faces 6 are of such outline and so disposed as not to present any obstruction to free passage of the expressed moisture from the material within the press. The bars 5 may be strengthened against disturbing effects due to internal pressure by adding to their radial depth between their ends, as shown in Fig. 6.

The numeral 12 is av feed neck and chamber provided with the usual feed opening 13, and substantially the same construction as that described with reference to the outer barrel 2.

14 is a reaction or feed end having a stepped circular opening 15, for purposes to be presently described. lVithin the barrel 2 is supported a conveying and compressing screw 16 surrounding and preferably made integral with the hollow shaft 17, having holes 18, for the passage of steam to warm up the material within the press.

19 is a hollow, stationary, central conveying barrel tapered toward the inlet end and having drainage openings 20 and fixed to uprights of the base frame 1 and projecting into the barrel 2 at the exhaust end, which is formed atits inner face with a bearing 21, to receive the rotary and reduced end 22 of the hollow rotary shaft 17, said end 22 being preferably closed by a plug 6 to retain the steam in the hollow shaft 17. Surrounding the inner portion of the fixed inner barrel 19 and snugly fitted and freely rotating about the same is a helicoidal compression spiral 23 preferably tapered toward the outlet end and which is a continuation of the compression screw 16, at a point a. short distance in advance of the zone of maximum compression. This spiral 23 is preferably made of increasing longitudinal cross section and supported at one end by the screw 16, by being cast as an integral part of the screw, or rigidly attached to the thread of the screw in any suitable manner. The helicoidal spiral 23 also extends outwardly and is fitted and secured by means of bolts 30, to a cylindrically formed tongue or projection 24 extending inwardly from a ro tary spider 24, made in halves connected together, and surrounding the outer section of the stationary barrel 19.

25 is a drive gear secured to the spider for the purposes which will be hereinafter described. The outer portion of the barrel 19 is made with a thrust flange 26 to be engaged by the spider, as shown.

Interposed between the end of the outer press barrel 2 and the rotating spider 24 is a shell 27 receiving the reaction during the operation of the press, and may be provided with observation openings 28, and the thrust washers 29. I

31 are openings in the end of the fixed central barrel 19 for purposes of drainage, to be later described.

Abutting against washers 32 in the opening 15 is snugly fitted a thrust collar 33 which is attached to the hollow shaft 17 and receives reaction from the thrust of the compressing screw 16 during the operation of pressing. Surrounding the outer end of the rotary shaft 17 is provided a stationary steam head 34 suitably supported on the frame 1, to which is attached a pipe 35 connected to any suitable source of steam for the purpose of conveying steam into the hollow shaft 17.

36 is a gland for making a steam tight joint between the head 34 and shaft 17 37 is a spur gear keyed or fastened on the outer end of the screw shaft 17 for rotating the same and which is engaged by the gear 38 on the counter-shaft 39, extending the full length of the press and supported in suitable bearings 40, as shown.

41 and 42 are other gears fastened to said countershaft 39, said gear 42 engaging the gear 25 for rotating the spider 24 and compression spiral 23. A main drive shaft 43 is provided with a gear 44 properly spaced, along its length to engage the gear 41 on shaft 39. At the other end of shaft 43 is a bevel gear engaged by a corresponding gear 46 on shaft 47 rotated by any suitable motor, not shown. Drainage boards 48 are provided extending over the shafts 39 and 43, and gears 41, 44, for the purpose of preventing any of the fluid pressed from the material within the press from dropping on the same.

I wish it to be distinctly understood that while I have shown and described a helicoidal compression member 23 with a stationary shaft 19, for a section of the press length, at the discharge end, I do not limit myself to this exact arrangement and proportion herein shown and described, but find. that the press will operate satisfactorily should the helicoid 23 be increased and extend substantially the entire length of the press, Or a greater or less length than that shown, depending upon the form of press, the material to be operated upon, and results obtained from experiments and data deterall mined from frictional values and effects herein referred to.

The operation of the press is as follows Assuming the material to be pressed entering the feed opening 13 in sufficient quan tity to keep the opening filled up, by rotation of the shaft e7, gears 46, 45, 4e, 38 and 37, the hollow shaft 17 with its screw 16 is rotated, which conveys the material through the barrel 2 and compressing it at the same time, due to the diminishing pitch of the screw, enlargement of the shaft 17 and contraction of the barrel 2. In order to facilitatethe action of the screw on the material to be pressed, steam passed from any suitable source, not shown, through the pipe 35 into the hollow shaft 17 and forced through the openings 18 into the material being conveyed and compressed by said screw 16. During the compressing of the material the moisture expressed. therefrom at its outer surface is d 'ained through the narrow longitudinal passages between the bars 5, forming the barrel and as the press operates, the material is continuously conveyed toward the discharge openings :49, and being meanwhile distorted in shape and compressed, to most effectively and e'tficiently express and drain the greatest amount of moisture therefrom. The material in its progress through the press, reaches and enters a relatively high pressure zone, where, unless proper means are provided, the material when in shape best for drainage, discontinues to travel forward, which is due to the friction caused by the compression exerting a greater clinging effort to the screw 16 and shaft 17 than to the outer barrel and will cause jamming conditions due to the material revolving with the screw and acting as an obstruction for the material advancing. Just before this zone of high pressure is reached by the material, the screw 16 and shaft 17 are eliminated and the material is acted upon by the compressing and conveying action of a compression member in the shape of the heavy rotary helicoidal spiral 23, thereby greatly reducing the friction on such member and at the same time putting the clinging and conveying action on. the outside of the inner stationary barrel 19. which necessarily adds to the conveying action of material inside of stationary barrel 2. at this high pressure point. As the helicoidal spiral and barrel 19 are a continuation of the surface of the screw 16. and shaft 17 in form, no complications are to be met with, while the press action relative to conveyance of the material is being changed. The additional openings 20, 20, in the inner stationary barrel 19, insures the material being properly and fully drained under conditions best suited and most practical.

From the foregoing disclosure of construction and mode of operation, the advantages of the helicoidal construction of the compression member and stationary barrel will be clearly comprehended.

It is to be understood that the helicoidal spiral 23, at its discharge end is developed in shape'best suited for connection with the projection or tongue 24 of spider 24;, and at the same time permit an easy discharge of the material through the opening 4L9 of the press. By the means described, by having the spider 24 and gear ring 25 attached, a powerful drive to the helicoidal spiral 23 is effected, and the thrust resulting from the action of the helicoidal spiral when operating upon material, is transmitted through the spider 2%. and distributed by means of the shell 27 and flange 26 to the outer end of the barrel 2, and inner barrel 19, respectively, and the bronze washers insure the repair and renewal of all wearing parts.

By providing separate thrust collar 33 and washers in conjunction with reaction head. let, and having the screw 16 rigidly attached to or cast integral with the shaft 17. assures a strong and firinconstruction, and hence rotative speed of the screw will be uniform and operation on the material smooth and regular.

The arrangement of shafting, bearings, gears. barrel and base, provide for easy egress of the pressed material and allows the drain board to be of simple construction and permits the entire press apparatus to be self contained and entirely above the floor.

Vi hat I claim is 1, A press comprising a tapered and perforated barrel having an inlet and an outlet, and a rotary helicoidal compression and conveying spiral of increasing longitudinal cross-section to 'ard. the outlet in said barrel tapered from the inlet toward the outlet for sinniltaueously expressing and advancing material within the barrel.

2. A press comprising a barrel having an inlet and an outlet, a fixed shaftin said barrel, and a rotary helicoidal compression and conveying spiral in said barrel of decreasing pitch and surrounding said fixed shaft, said spiral sin'mltancously expressing and advancing material within the barrel.

3. A press comprising a perforated barrel having an inlet and an outlet, a fixed shaft in said barrel. and a rotary helicoidal compression and conveying spiral in said barrel and surrounding said fixed shaft. said helicoidal spiral being of increasing longitudinal cross section toward the outlet and simultaneously expressing and advancing ma terial within the barrel.

t. A press comprising a barrel having an inlet and an outlet, a hollow and perforated fixed shaft in said barrel, and a rotary heli coidal compression and conveying spiral in said barrel and surrounding said fixed shaft, said spiral simultaneously expressing and advancing material within the barrel.

5. A press comprising a perforated barrel having an inlet and an outlet, a fixed shaft in said barrel tapered toward the inlet, and a rotary helicoidal compression and conveying spiral in said barrel and surrounding said fixed shaft.

6. A press comprising a barrel having an inlet and an outlet, a solid rotary compression screw within said barrel, a fixed shaft in said barrel, and a rotary helicoidal compression and conveying spiral surrounding said fixed shaft and being a continuation of said compression screw.

7. A press comprising a tapered and perforated barrel having an inlet and an outlet, a solid rotary compression screw of de creasing pitch within said barrel, a fixed shaft in said barrel, a rotary helicoidal compression and conveying spiral of decreasing pitch surrounding said fixed shaft and being a continuation of said compression screw.

8. A press comprising a barrel having an inlet and an outlet, a rotary shaft having a compression screw fixed thereto and within said barrel, a hollow and perforated fixed shaft in said barrel supporting the end of said rotary shaft, a rotary helicoidal compression and conveying spiral surrounding said fixed shaft and fixed to and being a continuation of said compression screw.

9. A press comprising a tapered and perforated barrel having an inlet and an outlet, a perforated hollow shaft having a rotary compression screw of decreasing pitch fixed thereto and within said barrel, a hollow and perforated fixed shaft in said barrel supporting the end of said rotary shaft, and a.

rotary helicoidal compression and conveying spiral of decreasing pitch surrounding said fixed shaft and fixed to and being a continuat-ion of said compression screw.

10. A press comprising a barrel having an inlet and an outlet, a solid rotary compression screw within said barrel and at the inlet section of said barrel, a hollow and perforated fixed shaft at the outlet section of said barrel, and a rotary helicoidal compression and conveying spiral surrounding said fixed shaft and being a continuation of said compression screw.

11. A press comprising a perforated bar rel having an inlet at one end and an outlet at the other end, a rotary compression screw within said barrel of decreasing pitch, a hollow and perforated fixed shaft at the outlet section and tapering toward the inlet and a rotary helicoidal compression and conveying spiral surrounding said fixed shaft and being a continuation of said compression screw.

12. A press comprising a barrel having an inlet and an outlet, a rotary shaft within and at the inlet section of said barrel, a compression screw of decreasing pitch fixed to and surrounding said rotary shaft, a hollow perforated fixed shaft at the outlet section of said barrel and supporting the outlet end of the rotary shaft, and a rotary helicoidal compression and conveying spiral surrounding said fixed shaft and being a continuation of said compression screw.

13. A press comprising a barrel having an inlet at one end and an outlet at the other end, a rotary shaft within said barrel, a compression screw at the inlet section of the barrel and fixed to and surrounding said rotary shaft, a fixed shaft at the outlet section, a rotary helicoidal compression and conveying spiral surrounding said fixed shaft and being a continuation of said compression screw, and means for simultaneously rotating the rotary shaft and screw and helicoidal spiral in the same direction.

14. A press comprising a perforated barrel having an inlet and an outlet, a hollow perforated rotary shaft within and at the inlet section of said barrel, means for passing steam into said hollow shaft, a compression screw fixed to and surrounding said rotary shaft, a fixed shaft at the outlet section of said barrel, and a rotary helicoidal compression and conveying spiral surrounding said fixed shaft and being a continuation of said compression screw.

15. A press comprising a perforated barrel having an inlet at one end and an outlet at the other end, a rotary shaft within said barrel and tapering from the inlet toward the outlet, a compression screw of decreasing pitch at the inlet section of the barrel and fixed to and surrounding said rotary shaft, a hollow perforated fixed shaft at the outlet section, and a rotary helicoidal compression and conveying spiral surrounding said fixed shaft and being a continuation of said compression screw.

16. A press comprising a perforated barrel of decreasing diameter having an inlet at one end and an outlet at the other or smaller end, a rotary shaft within said barrel and of increasing diameter toward the outlet end, a compression screw at the inlet section of the barrel and fixed to and surrounding said rotary shaft, a hollow perforated fixed shaft at the outlet section and a rotary helicoidal compression and conveying spiral surrounding said fixed shaft and being a continuation of said compression screw.

17. A press comprising a perforated barrel of decreasing diameter having an inlet at one end and an outlet at the other end, a hollow perforated rotary shaft within said barrel and of increasing diameter toward the outlet, a compression screw at the inlet section of the barrel and fixed to and surrounoing said rotary shaft, means for admitting steam, into said hollow rotary shaft, a hollow perforated fixed shaft at the outlet section, and a rotary helicoidal compression and conveying spiral surrounding said fixed shaft and being a continuation of said compression screw.

18. A press comprising a perforated barrel of decreasing diameter having an inlet at one end and an outlet at the other end, a hollow perforated rotary shaft within said barrel and of increasing diameter toward the outlet, a compression screw of decreasing pitch from the inlet toward the outlet at the inlet section of the barrel and fixed to and surrounding said rotarv shaft, a hollow and perforated fixed shaft at the outlet section, and a rotary helicoidal compression and conveying spiral of increasing width surrounding said fixed shaft and being a continuation of said compression screw.

19. A press comprising a barrel having an inlet and outlet, arotary compression member in said barrel for advancing and conr pressing the material in said barrel, a fixed cylindrical thrust shell at the outlet and abutting against the end of the barrel, a. rotary cylindrical spider onnected with said compression member and abutting against the outer end of the shell, and means for rotating said spider and compression member.

20. A. press comprising a barrel having an inlet and outlet, a rotary compression mcmher in said barrel for advancing and compressing the material in said barrel, a fixed cylindrical thrust shell at the outlet and abutting against the end of the barrel, a fixed shaft projecting into the end of the shell and rotatably supporting the end of the compression member, a rotary cylindrical spider connected with said compres sion member, said spider surrounding the fixed shaft and abutting against the outer end of the shell, and means for rotating said spider and compression member.

21. A press comprising a barrel having an inlet and outlet, a cylindrical thrust shell at the outlet and abutting against the end of the barrel, a fixed shaft in said barrel and shell, a rotary helicoidal spiral for advancing and compressing the material in said barrel and surrounding said fixed shaft, a rotary cylindrical spider connected with said spiral, said spider surrounding the shaft and abutting against the outer end of the shell, and means for rotating said spider and spiral.

22. A press comprising a perforated barrel having an inlet and outlet and decreasing in diameter from said inlet to the outlet, a rotary compression member in said barrel for advancing and compressnig the material in said barrel, a fixed cylindrical thrust shell at the outlet provided with observation openings and abutting against the end of the barrel, a. fixed shaft projecting into the end of the shell and rotatably supporting the end of the compression member, a rotary cylindrical spider connected with said compression member, said spider surrounding the fixed shaft and abutting against the outer end of the shell, and means for rotating said spider and compression member.

23. A press comprising a barrel having an inlet and outlet, a rotary compression screw in said barrel for advancing and compressing the material in said barrel, a cylindrical thrust shell at the outlet and abutting against the end of the barrel, a fixed shaft projecting into the end of the shell and supporting the end of the compression screw, a rotary helicoidal spiral surrounding said fixed shaft and forming a continuation of the compression screw, a rotary cylindrical spider connected with said spiral, said spider surrounding the fixed shaft and abutting against the outer end of the shell, and means for rotating said spider and helicoidal. spiral.

24. A press comprising a perforated barrel having an inlet and outlet and decreasing in diameter from said inlet to the outlet, a rotary shaft having a compression screw fixed thereto and in said barrel for advanc ing and compressing the material in said barrel, a cylindrical thrust shell at the outlet provided with observation openings and abutting against the end of the barrel, a fixed shaft projecting into the end of the shell and supporting the end of the compression screw, a rotary helicoidal spiral surrounding said fixed shaft and forming a continuation of said compression screw, a

.rotary cylindrical spider connected with said helicoidal spiral, said spider surrounding the fixed shaft and abutting against the outer end of the shell, and means for rotating said spider and spiral.

25. A screw press comprising a drainage barrel having a series of circular rib members spaced at intervals along the longitudinal axis of said barrel, a clamping band removably connected to the inner periphery of each of said circular members, a series of longitudinal and separated strainer bars provided with notched ends engaging the edges of the clamping bands, and means for rigidly holding said series of circular members in proper relation to each other.

26. A screw press comprising a drainage barrel having a series of circular rib members spaced at intervals along the longitudinal axis of said barrel, a clamping band removably connected to the inner periphery of each of said circular members, a series of longitudinal and separated strainer bars provided at their ends with notches engaging the edges of the clamping bands, and

side projecting faces 0r cheeks for retaining said bars in separated relation to each other,

and means for rigidly holding said series of circular rib members in proper relation to each other.

27. A screw press comprising a drainage barrel having a series of circular rib members spaced at intervals along the longitudinal axis of said barrel, a clamping band removably connected to the inner periphery of each of said circular members, a series of longitudinal and separated strainer bars provided at their ends with notches engaging the edges of the clamping bands, and side projecting faces or checks for retaining said bars in separated relation to each other, said projecting faces being disposed under the rib members, and means for rigidly holding said series of circular members in proper relation to each other.

In testimony whereof I atfix my signature in presence of two Witnesses.

THOMAS C. SCHUYLER. Witnesses:

JEREMIAH V. RYAN, WM. C. PETTIT.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. C.

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