US3668103A

US3668103A - Hanger bracket and driving apparatus for plating barrels

Info

Publication number: US3668103A
Application number: US91394A
Authority: US
Inventors: Albert Singleton
Original assignee: Albert Singleton
Current assignee: SINGLETON RAYMUND
Priority date: 1970-11-20
Filing date: 1970-11-20
Publication date: 1972-06-06
Anticipated expiration: 1989-06-06

Abstract

The specification and drawings disclose a plating barrel assembly which comprises a barrel member mounted for rotation about its longitudinal axis. The barrel is supported from generally vertically extending hangers formed from metal reinforced plastic and are carried by a horizontally extending frame adapted to removably rest on the upper edge of the plating tank. Means are provided for rotating the barrel and the means include a shaft rotatably carried on the horizontal frame and connected through a gear train with a gear connected to an end of the drum. At least one end of the horizontal shaft extends outwardly of the frame for releasable engagement with a drive assembly. The drive assembly is mounted on one end of the plating tank and includes a first support frame mounted for vertical adjustment and including a horizontally extending portion and an inclined portion. A motor is adjustably mounted on the inclined portion and is drivingly connected with a gear reducer unit carried on the horizontal portion. The gear reducer is positioned with its output shaft extending horizontally and carrying a gear adapted to releasably engage a gear on the shaft member. The entire drum assembly has a low total height so that it can be easily lifted from the plating tank.

Description

United States Patent Singleton [4 1 June 6,1972

[54] HANGER BRACKET AND DRIVING APPARATUS FOR PLATING BARRELS Albert Singleton, 7360 Brookside Parkway, Middleburg Heights, Ohio 44l 3O [22] Filed: Nov. 20, 1970 [21] Appl.No.: 91,394

[72] Inventor:

Primary Examiner-John H. Mack Assistant ExaminerW. l. Solomon Attorney-Fay, Sharpe and Mulholland [5 7] ABSTRACT The specification and drawings disclose a plating barrel assembly which comprises a barrel member mounted for rotation about its longitudinal axis. The barrel is supported from generally vertically extending hangers formed from metal reinforced plastic and are carried by a horizontally extending frame adapted to removably rest on the upper edge of the plating tank. Means are provided for rotating the barrel and the means include a shaft rotatably carried on the horizontal frame and connected through a gear train with a gear con nected to an end of the drum. At least one end of the horizontal shaft extends outwardly of the frame for releasable engagement with a drive assembly. The drive assembly is mounted on one end of the plating tank and includes a first support frame mounted for vertical adjustment and including a horizontally extending portion and an inclined portion. A motor is adjustably mounted on the inclined portion and is drivingly connected with a gear reducer unit carried on the horizontal portion. The gear reducer is positioned with its output shaft extending horizontally and carrying a gear adapted to releasably engage a gear on the shaft member. The entire drum assembly has a low total height so that it can be easily lifted from the plating tank.

10 Claims, 8 Drawing Figures PATENTEDJUH 6 I972 SHEET 1 OF 3 INVENTOR.

ALBERT SINGLETON BY 4 6,, 5 :2 MW

ATTORNEYS PATENTEDJUH 6 I972 SHEET 2 OF 3 FIG. 2

FIG. 3

INVENTOR.

ALBERT SINGLETON BY 4m 5 $44M ATTORNEYS PATENTEDJUN 6 I972 SHEET 3 BF 3 I: lllllllllliig INVENTOR.

ALBERT SINGLETON 4 a e a MW ATTORNEYS The present invention is directed toward the metal finishing art and, more particularly, to an improved plating barrel assembly for use in metal finishing operations.

The invention is especially suited for use as an electroplating barrel and will be described with particular reference thereto; however, it should be appreciated that apparatus of the type under consideration is used not only for plating but can also be used for cleaning, phosphating, and otherwise treating many types of parts. Hence, in the subject specification and claims, the terms plating barrel is used for convenience in referring to a barrel structure or apparatus for performing this general type of operation and is not to be considered as limited to only an apparatus for electroplating.

My US. Pat. No. 2,886,505, issued May 12, 1959 discloses a plating barrel assembly of the general type under consideration. In using plating barrels of this type, it is necessary to raise and lower the barrel assembly from the tank of electrolyte at frequent intervals during operation. In a typical plating operation, there may be 30 to 100 assemblies in use at any one time. Thus, it is important that the barrel assemblies be as compact as possible to minimize the vertical distance which the assemblies must be moved during the raising and lowering operation.

Additionally, the power source and drive train for the barrel assembly should preferably be arranged so that the barrel assembly can be easily separated from the power source.

In addition to being compact and of relatively light weight, the barrel assembly must also be capable of operating in extremely corrosive environments.

In accordance with one aspect of the invention, there is provided a plating barrel assembly which comprises a barrel member mounted for rotation about is longitudinal axis. The barrel is supported from generally vertically extending hangers which are carried by a horizontally extending frame adapted to rest on a plating tank. Means are provided for rotating the barrel and the means include a shaft rotatably carried on the horizontal frame with a first gear fixed near one end. A second gear is engaged with the first gear and rotatably carried by a hanger member. A third gear is connected to the drum for driving engagement with the second gear. At least one end of the horizontal shaft extends outwardly of the first gear and is provided with means for releasably engaging a drive means. Preferably, the drive means is mounted on one end of the plating tank and includes a first support frame mounted for vertical adjustment and including a horizontally extending portion and an inclined portion. A motor is adjustably mounted on the inclined portion and is drivingly connected with a gear reducer unit carried on the horizontal portion. The gear reducer is positioned with its output shaft extending horizontally and carrying a gear adapted to releasably engage a gear on the shaft member.

Preferably, the hanger members comprise at least one plastic bar member having a metal reinforcing rod sealed therein. The drum is carried on a pair of hubs, one hub projecting from each hanger. Bearings mounted between the hubs and the drum comprise split rings, preferably formed from polypropylene filled with graphite, which minimize friction and galling between the stationary hub and the rotating drum.

A further aspect of the invention concerns a method of reinforcing plastic with metal by a welding operation.

Accordingly, a primary object of the invention is the provision of the improved barrel assembly and barrel mounting arrangement which allows the total assembly to have a short vertical height and to withstand relatively rough usage in corrosive environments.

A still further object of the invention is the provision of a barrel assembly of the general type described which has a drive assembly that is trouble-free and which automatically engages upon location of the barrel over the plating tank.

A further object is the provision of a bearing assembly for plating barrels which can operate in extremely corrosive environments without galling, seizing, or the like.

A still further object is the provision of a method of fonning metal reinforced polypropylene members.

These and other objects and advantages will become apparent from the following description when read in conjunction with the accompanying drawings wherein:

FIG. 1 is a longitudinal cross-sectional view through a plating tank and barrel assembly formed in accordance with the preferred embodiment of the invention;

FIG. 2 is an end view taken on line 2-2 of FIG. 1;

FIG. 3 is a view taken on line 3-3 of FIG. 2 showing the motor, gear reducer, and drive trail in detail;

FIG. 4 is a cross-sectional view taken on line 4-4 of FIG. 1 and showing the gear train and barrel support bracket in detail;

FIG. 5 is a cross-sectional view taken on line 55 of FIG. 4;

FIG. 6 is a cross-sectional view taken on line 6-6 of FIG. 4 and showing the mounting arrangement for the idler gear;

FIG. 7 is a cross-sectional view taken on line 7-7 of FIG. 4 and showing in detail the bearing and drum mounting assembly; and,

FIG. 8 is a cross-sectional view taken on line 8-8 of FIG. 4 and showing the reinforcing arrangement utilized in the barrel hanger arms.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more particularly to FIG. 1, the overall assembly is shown in some detail and comprises an open topped tank 10 which functions to hold the electrolyte solution and supports the removable plating barrel assembly 12. The particular structural details of the tank 10 form no part of the present invention and could vary widely; however, in the preferred embodiment, the tank 10 is of generally rectangular shape having a flat bottom wall and vertically extending side and end walls and is formed, for example, from metal and lined or covered with a relatively heavy corrosion resistant and non-electrically conductive material such as a suitable rubber or plastic material. Outwardly extending

flanges

14 and 16 are joined to the upper edges of the side and end walls.

The plating barrel assembly 12 is releasably and removably carried on the outwardly extending

flanges

14 and 16 at the upper end of tank 10 by a pair of straight cylindrical, low-resistance

copper cathode rods

18 and 20 of circular cross-section. As best shown in FIGS. 1 and 2, the

rods

18 and 20 are supported on the respective flanges by generally rectangular mounting blocks 21 joined to the flanges by vertically extending machine screws 22. Inthe embodiment under consideration, the blocks 21 are formed from polypropylene; however, it should be appreciated that other types of mounting blocks could be used. It will be noted in FIG. 2 that the upper surfaces M of the blocks 21 are inclined downwardly toward the center of the tank. As will be described more fully hereafter, this arrangement of the blocks produces a centering action on the barrel assembly when it is positioned on the tank.

Of particular importance to the invention is the overall arrangement of the plating barrel assembly 12. The assembly 12 includes a support frame 26 which extends across the upper end of the tank and carries the barrel 28. The support frame 26 is comprised of a transversely extending channel member 29 which extends the length of the tank with its channel legs facing downwardly. Connected to the ends of the channel member 29 are plates 30 [See FIGS. 1 and 3]. In the embodiment shown, the plates 30 are welded to the channel ends and extend vertically and horizontally of the channel. A pair of angle members 32 are releasably connected to the plates 30 at each end of the channel by bolts 34. Electrical conduit or saddle blocks 36 of large cross-sectional area and low electrical resistance are connected to the lower faces of angles 32. Suitable insulation is positioned between the angles 32 and the saddle blocks 36 to prevent the flow of electricity therebetween. It will be noted that each of the saddle blocks 36 has a generally V-shaped recess formed in its lower surface which is arranged to engage a

corresponding cathode rod

18 or 20. Connected to the bars 36 are flexible electrodes or

conduits

38 and 40 which will subsequently be described in more detail.

The barrel 28 is' supported from the channel member 29 by two pairs of hangers 41, each having upwardly extending

arms

42 and 44. The

arms

42 and 44 are adjustably joined to the channel by short anglemembers 46 and 48 respectively [See FIG. 4]. Each of the

angles

46 and 48 is welded to a lateral face of the channel 29 and has elongated

bolt receiving slots

47 and 49 formed therein. Suitable machine screws pass through the slots into engagement with the respective hanger arms. By releasing the screws, the vertical position of the hangers 41 can be readily adjusted.

As best shown in FIGS. 1 and 4, the hangers extend vertically downward from the channel 29 and support the drum within the electrolyte solution. The construction of the hangers is of particular importance to the invention. As can be appreciated, because of the corrosive nature of the electrolyte or cleaning solutions used, the hangers, as well as the remaining elements of the drum assembly, must be capable of withstanding a particularly corrosive atmosphere. Further, the hangers must have suitable strength to resist the forces exerted thereon during operation and use of the assembly. In the subject embodiment, the

hanger'arms

42 and 44 are formed from a corrosion resistant plastic such as polypropylene with an internal reinforcing bar of steel or other suitable metal. FIG. 8 is a cross-section through one of the-arms or bars 44 showing the internal reinforcing member 50 which is, in this instance, a flat steelbar. The construction of each of the

hanger arms

42 and 44 are identical and, accordingly, only one will be described in detail.

Referring again to FIG. 8, it will be seen that the arm 44 is formed from a rectangular, elongated section of polypropylene provided with a longitudinally extending slot 52 which is of a width sufficient to closely receive the metal bar 50. The slot 52 extends into the main body of polypropylene a depth greater than the width of bar 50. Positioned over the outer edge of the bar and within the slot 52 is a strip 54 of plastic or similar material having heat insulating each pair of the hanger arms and, in turn, supports a cylindrical hub member 60. The hub members 60 are removably connected to their respective block 58 by machine screws 62 which extend inwardly through the blocks 58 into threaded openings in the cylindrical hubs 60. It is obvious that the two

arms

42, 44 and the block 58 could be integral and could be formed by merely cutting a slot in one end of a rectangular block of plastic to accommodate the channel 29 et al, if

desired.

As noted in FIG. 1, electrode 40 extends through an opention and includes the end walls 66 and 68 joined by flat,

properties. The strip 54 preferably extends throughout the length of the bar and is of a thickness sufficient to provide a groove inwardly from the outer edge of the slot 52. A second strip of plastic 56 is welded to the main block over the strip 54. The welding is accomplished by a conventional plastic welding gun which extrudes a strip of heated plastic into the groove for bonding with the side walls of the groove and the insert 54. Insert 54 serves to prevent the metal reinforcing bar from acting as a heat sink and conducting heat away from the heated weld strip. Without strip 54, the weld bead 56 will deposit in the slot against the. bar 50 without bonding to either side wall. This layered arrangement assures a good fluid tight weld joint between the strip 56 and the main body of the block. Thus, the metal reinforcing strip is totally encased in the plastic and is not exposed to the corrosive environment.

The purpose of the encapsulated steel bars 50 is to strengthen the

arms

42, 44 in shear, bending and torsion. The plastic is of sufficient strength in tension to carry the load in the drum but without the steel bars the arms fail rather quickly due to the bending moments resulting from the drum rotation and the sway imparted by the tumbling parts therein.

In addition to reinforcing the hanger rods 41, the transversely extending rods or bars 70 are also reinforced with steel strips 51 (seeFIG. 4). I

The barrel is rotatably supported from the lower end of the hangers by the assembly best shown in FIG. 7. It will be noted that a rectangular block of polypropylene 58 is welded between the lower ends of the

hanger arms

42, 44. Referring again to FIG. 1, one of the members 58 is carried between rectangular side walls 69. The side walls are joined along their mating longitudinal edges by suitable parallel reinforcing bars 70 (see FIG. 4). Each of the side walls is preferably heavily perforated to allow free flow of the plating solution through the interior of the tank. Additionally, one of the side walls is removable and serves as an access opening. The access opening is held in position by suitable clamps or the like such as shown, for example, in my previously mentioned U.S.'Pat. No. 2,886,505.

One important aspect of the invention is the bearing arrangement for the barrels. As can be seen, the cylindrical hub members 60 extend into central openings formed in the end walls 66, 68. A sleeve bearing 71 is positioned about the right hand hub 60 [as viewed in FIG. 1] while a similar sleeve bearing 72 surrounds the left hand hub 60. The sleeve bearing is a polypropylene bushing which is filled with graphite. This greatly reduces friction and tends to eliminate freezing or galling between the surfaces; however, it has been found that the use of the graphite filled polypropylene alone does not completely eliminate freezing and galling problems. For this reason, as best shown in FIGS. 4 and 7, the

bearings

71 and 72 are each provided with a longitudinal slot 74. The bushing is maintained in position by a suitable pin 76 which extends from the end plate 78 through the bearing 71. This causes the bearing 71 to rotate with the drum about the stationary hub 60. Should any seizing occur between the internal surface of the sleeve 71 and the outer surface of the hub 60, the groove or split 74 allows the bearing 71 to expand radially thereby relieving the tension and allowing a quick slippage, thus minimizing any possibility of galling.

The drive assembly for the drum 28 includes a standard electric motor carried at the right hand end of the tank 10. The motor is connected through a three-step pulley 92, V-belt 94, and a second three-step pulley 96 with the input shaft of a right angle gear reducer 98. The motor 90 and the gear reducer 98 are carried from an angle bracket or frame assembly 100 which is arranged for vertical adjustment to vary the elevation of the output shaft 102 of the gear reducer 98. The mounting bracket 100 includes a horizontal support plate 102 which is welded to a vertically extending slide plate 104. An angle member 106 is connected between the outer end of plate 102 and the lower end of slide plate 104. It will be noted that the gear reducer 98 is affixed to the surface of plate 102 through the use of machine screws 108. In order to provide for adjustment of the mounting bracket in the vertical direction, it will be noted that the slide plate 104 is received within a guideway formed by a pair of spaced members 110 [see FIG. 2] which have overlapping edge portions that engage the slide plate at is opposite lateral edges. The slide plate is suspended from the flange 16 of tank 10 by an elongated stud bolt 112 that extends through openings in the support plate 102. Suitable nuts 114 allow the position of the angle bracket to be adjusted on the bolt 112. This arrangement permits the output shaft 102 to be positioned precisely relative to the drive train to insure proper mating between the drive gears. Additionally, the motor mounting arrangement is such that the belt 94 can be readily adjusted in tension. Also, the belt 94 can be shifted between various steps of the pulleys to change the drive speed of the drum 28.

Referring to FIG. 2, it will be seen that the motor 90 has its support plate 116 slidably engaged with a pair of guideway forming members 118 welded to the inclined plate 106. As mentioned, the motor mounting plate 116 is freely slidable within the guideway forming members 118. To lock it in a desired position of adjustment, there is a thumb screw or the 7 like 120 which passes through a threaded opening or nut member carried on the plate 116. By tightening the nut or the screw member 120, the end of the screw engages the surface of the inclined bracket member 106.

An important feature of the invention is the construction of the drive train and its relationship to the frame and hanger assemblies. As shown, the drive train from the output shaft of the gear reducer 98 to the barrel 28 includes a first pinion gear 130 which is formed from a suitable corrosion resistant plastic, preferably a thermoplastic ABS Polymer or polypropylene such as Seilon S3HT sold by Seiberling Rubber Co. The gear 130 is connected to the shaft 102 by a set screw or other suitable means. It will be noted that the gear 130 is positioned so as to be closely adjacent the end wall of the tank 10 and approximately at the level of the flange 16. The flange 16 is cut out in the vicinity of the gear 103 to provide access to the pinion 130 by a driven pinion gear 132.

In the aforementioned Singleton patent, it will be noted that the driving gear projecting from the gear box is located wholly above the top flange on the tank of fluid. With the improvement of the instant invention, the driving gear 130 extending from the gear reducer 98 is almost completely below the flange 16. This improvement allows the shortening of the distance between the barrel 28 and the frame 12 by about 4 inches. While this may seem, relatively insignificant to the average man, to one of ordinary skill in the art, it will loom as a substantial breakthrough in cost reduction. The costs in labor, time and power involved in lifting a hundred loaded drums an extra 4 inches an hour, 24 hours a day is not inconsequential.

Note that the gear 132 is carried on the end of a horizontally extending drive shaft 134 which extends parallel to the channel 29. The shaft 134 is carried in bearing blocks 136 which are formed from polypropylene or the like and extend downwardly from the underface of channel 29. As best shown in FIGS. 2 and 3, the bearing blocks 136 are supported from channel 29 by adjustable machine screws 138 which extend through openings in the channel. This allows the bearing blocks to be adjusted vertically with spacer washers and also permits them to be somewhat self-aligning.

Carried on the shaft intermediate the bearing blocks 136 is a pinion gear 140. The gear 140 is drivingly engaged with an intermediate idler gear 142. As best shown in FIG. 4, the gear 142 is pinned to a stub shaft 144 carried from a support block 146. As shown in FIG. 6, the support block 146 is welded to the

hanger arms

42, 44.

The gear 142 is engaged with a large diameter gear 148 connected to the end of the drum for producing rotation of the drum. As best shown in FIG. 1, the gear 148 is formed from plastic and is bolted to the end plate 78.

The arrangement described allows substantially the entire drive train to be removed with the barrel assembly. Note that in FIG. 1 there is shown a U-bolt 150 which is centrally positioned on the channel 29. In lifting the barrel assembly, the barrel and the support frame are raised upwardly causing the gear 132 to disengage gear 130. After the necessary steps have been taken, such as filling the barrel and the like, replacement of the drum assembly is facilitated by the inclined surfaces of the blocks 21 [see FIG. 2]. The

gears

132 and 130 are automatically re-engaged in their proper relationship upon replacement of the drum assembly in the tank 10.

Because of the torsional forces imparted to the idler gear 142 by the driving pinion and the heavy loaded drum, special assembling techniques are employed. The stub shaft 144 includes a hole 152 threaded tranversely of its axis. A screw 154 projects through an aperture in the gullet of one of the gear teeth and into the hole. This locks the shah and gear together with the gear substantially flush with the side of support block 146. Thus, torsional forces imparted to the gear 142 will immediately be transferred to the stronger block 146 due to the face-to-face contact, rather than tending to twist the gear out of alignment. The driving gear 140 is similarly attached to shaft 134.

Friction between the polypropylene block and gear is at a minimum and the shaft 144 is joumalled in a Teflon bushing 156. Because of the corrosive nature of the environment, it is preferred that the screws for locking the

gears

140, 142 to the

shafts

134, 144, respectively, be of stainless steel, titanium, Carpenter No. 2OCB or of suitable plastic.

The invention has been described in great detail sufiicient to enable one of ordinary skill in the metal treating art to make and use the same. Obviously, modifications and alterations of the preferred embodiment will occur upon a reading and understanding of the specification and it is my intention to include all such modifications and alterations as part of my invention insofar as they come within the scope of the appended claims.

What is claimed is:

1. A plating barrel assembly for finishing parts adapted for use in electroplating in combination with electrodes compris mg:

a barrel member mounted for rotation about is longitudinal axis;

hanger members supporting said barrel and extending downwardly from a horizontally extending frame adapted to rest on a plating tank;

means for rotating said barrel comprising a shaft member rotatably supported from said frame and having a first gear member carried thereon;

a second gear carried from one of said hangers and engaging said first gear, said second gear including a flat side in constant direct contact with a flat surface on one of said hangers of a size at least equal to the size of the gear, a third gear connected to said drum and engaging said second gear;

said shaft having at least one end extending outwardly from said first gear for engagement with drive means; and

means on the ends of said frame for locating said assembly on a plating tank.

2. The apparatus of claim 1 wherein said hanger members comprise at least one plastic bar member having a metal reinforcing rod sealed therein.

3. The apparatus of claim 1 wherein all of said gears are formed from plastic.

4. The apparatus of claim 1 including a plating tank having a drive assembly carried on one end thereof;

said drive assembly including a first support frame mounted for vertical adjustment and including a horizontally extending portion and an inclined portion;

a motor adjustably mounted on said inclined portion and drivingly connected with a gear reducer unit carried on said horizontal portion, said gear reducer having a horizontally extending output shaft provided with a gear adapted to engage a gear on the shaft which carries said first gear.

5. The apparatus of claim 4 wherein the means for adjusting the drive assembly support plate comprise a threaded member extending downwardly from a peripheral flange on said tank.

6. The apparatus of claim 4 wherein said motor is adapted for adjusting movement along said inclined portion.

7. The apparatus of claim 4 including a flange extending about the upper end of said tank and wherein the gear on said gear reducer output shaft extends upwardly through an opening formed in said flange.

8. The apparatus of claim 4 including cooperating inclined surfaces on said frame and said tank for aligning said drum assembly with said tank.

9. In the combination of a foraminous hollow barrel enclosing metallic articles to be treated by fluid which penetrates said barrel from without,

hanger brackets for supporting said barrel for rotation about its axis in a substantially horizontal plane,

a support frame for supporting said brackets,

gear and motor means for rotating said drum, and

electrode means for passing electric current through said fluid, the improvement comprising:

hubs extending through apertures in each end of said barrel along its axis, said hubs being rigidly fixed to said brackets,

locked for rotation with said barrel while said hub remains stationary.

Claims

1. A plating barrel assembly for finishing parts adapted for use in electroplating in combination with electrodes comprising: a barrel member mounted for rotation about is longitudinal axis; hanger members supporting said barrel and extending downwardly from a horizontally extending frame adapted to rest on a plating tank; means for rotating said barrel comprising a shaft member rotatably supported from said frame and having a first gear member carried thereon; a second gear carried from one of said hangers and engaging said first gear, said second gear including a flat side in constant direct contact with a flat surface on one of said hangers of a size at least equal to the size of the gear, a third gear connected to said drum and engaging said second gear; said shaft having at least one end extending outwardly from said first gear for engagement with drive means; and means on the ends of said frame for locating said assembly on a plating tank.

3. The apparatus of claim 1 wherein all of said gears are formed from plastic.

4. The apparatus of claim 1 including a plating tank having a drive assembly carried on one end thereof; said drive assembly including a first support frame mounted for vertical adjustment and including a horizontally extending portion and an inclined portion; a motor adjustably mounted on said inclined portion and drivingly connected with a gear reducer unit carried on said horizontal portion, said gear reducer having a horizontally extending output shaft provided with a gear adapted to engage a gear on the shaft which carries said first gear.

9. In the combination of a foraminous hollow barrel enclosing metallic articles to be treated by fluid which penetrates said barrel from without, hanger brackets for supporting said barrel for rotation about its axis in a substantially horizontal plane, a support frame for supporting said brackets, gear and motor means for rotating said drum, and electrode means for passing electric current through said fluid, the improvement comprising: hubs extending through apertures in each end of said barrel along its axis, said hubs being rigidly fixed to said brackets, openings through said hubs, said electrode means extending through said openings, one of said openings being inclined downwardly from outside the barrel toward the inside, a cylindrical bearing disposed between each hub and the barrel to support the barrel in sliding rotary movement, said bearing being formed from a mixture of polypropylene and graphite, saId bearing including a longitudinal slit extending for its full length to allow the bearing to expand radially to relieve tension and minimize galling during rotary movement of said barrel.

10. The combination of claim 9 wherein the bearing is locked for rotation with said barrel while said hub remains stationary.