GB1574252A - Printing cylinder with means to mount a printing plate by vacuum power - Google Patents

Description

(54) PRINTING CYLINDER WITH MEANS TO MOUNT A PRINTING PLATE BY VACUUM POWER (71) We, LIVERMORE AND KNIGHT COMPANY, INC., a corporation organised and existing under the laws of the State of Florida, United States of America, having a place of business at 225 Seabreeze Avenue, Palm Beach, Florida, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following state ment:- The invention relates to an improved form of vacuum-printing cylinder for a printing press. providing a practical means for holding the printing plate on the cylinder by vacuum alone, without requiring separate adhesive means and/or supplementary mechanical devices for clamping the plate.

The cylinder includes a supporting shaft mounting, between its bearing portions, a plurality of cylinder supporting rings. A cylinder sleeve is supported by the rings and forms, together with the rings and the supporting shaft, a hollow cylinder structure having a pluralitv of vacuum chambers. The interior of the cylinder can be evacuated from one end of the shaft, and independently controllable valve means are built into the cylinder, to enable the several chambers thereof to be independently evacuated. The sleeve is provided with a plurality of axially spaced, continuous annular grooves, which communicate at one or more places with the interior of the cylinder. The continuous grooves are blocked off at one or more places around the circumference of the cylinder to avoid leakage at the end-to-end discontinuity in a printing plate supported on the cylinder.

A relatively continuous porous medium may be used around the exterior of the printing cylinder and about which the printing plate is wrapped and secured by vacuum. In some cases, the porous media is a filter paper material, which may be of various thicknesses to accommodate printing plates of different thicknesses. In other cases, the porous medium may be a sintered metal coating, permanently bonded about the exterior of the cylinder. In either case, the porous medium serves to diffuse and render more uniform the application of vacuum to the underside of the printing plate.

Rotary printing machines, such as rotary offset lithographic machines, for example, utilize printing cylinders to which printing plates are conformed and secured. The printing plates rotate with the cylinders and apply the desired impression to a rubber covered blanket cylinder, which then transfers the impression to a sheet or web passed between the blanket cylinder and an opposing roll or plate. Typically, means are provided on the printing cylinder for mechanically engaging one or both ends of the printing plate in order to keep the plate properly positioned on the cylinder. Commonly, this is done by providing means for clamping the ends of the printing plate. In some cases, adhesive is utilized, alone or in conjunction with other means, to hold the printing plates in position.

It has been proposed heretofor to utilize vacuum means to retain the printing plates in position on the printing cylinders. Representative of prior proposals for this purpose are United States Patents No. 2,060,082, No. 3,122,698, No. 3,380,381, and No, 3,463,476. The theoretical advantages of the vacuum cylinder are evident, in that it is expected to be able to more easily mount printing plates thereon. Changing of printing plates is also expected to be facilitated.

However, notwithstanding the expected advantages to be derived from the vacuum cylinder, its commercial acceptance has been extremely limited, because of the practical difficulties experienced in achiev ing an effective design of a vacuum cylinder suitable for use under conditions of day to day commercial production.

As its basic objective, the present invention seeks to provide a novel and improved design and construction of a vacuumprinting cylinder suitable for utilization under conditions of typical commercial production and which does not require the use, in conjunction with the vacuum holding means, of mechanical or other auxiliary holding means to assist in securing the printing plate on the face of the cylinder.

Accordingly we provide a printing cylinder for mounting a printing plate by vacuum power, comprising a shaft, a cylinder sleeve supported on said shaft and defining a vacuum chamber, means to evacuate said chamber, a plurality of generally continuous annular grooves formed on the outer surface of said cylinder sleeve, air passage means connecting each of said annular grooves with said vacuum chamber, said cylinder sleeve having at least one axially disposed groove intersecting said annular grooves and axially disposed sealing strip means tightly received in and completely filling said axial grooves to form a continuation of the outer surface of the sleeve in the circumferential direction and block said annular grooves to provide a predetermined circumferential discontinuity between adjacent ends of each annular groove, so that when a printing plate is mounted on the outer surface of said sleeve with its end edge portions overlapping said sealing strip means the plate is held on said cylinder by the vacuum power of said chamber and leakage adjacent to the ends of the vacuumheld printing plate is substantially avoided.

A plurality of cylinder supporting rings may be secured in axially spaced relation on the shaft to support the cylinder sleeve and divide the interior of the printing cylinder into a plurality of vacuum chambers. The supporting shaft and rings are provided with internal passages for the evacuation of the internal chambers. Independent valve means are provided for selectively evacuating all or less than all of the plurality of chambers of the cylinder, so that small size printing plates may be readily utilised andl or so that printing plates may be removed and replaced from part of the cylinder surface, without disturbing other plates secured by a vacuum in adjacent areas. An effective balance is therefore provided with respect to the amount and distribution of exposed vacuum area on the outer surface of the cylinder, such that adequately distributed vacuum-holding power is available to secure the printing plates, while at the same time minimizing leakage which would reduce the overall holding effectiveness of the cylinder. If only a portion of the surface of the cylinder is to be covered by the printing plate, the otherwise exposed portion of the cylinder surface may be isolated from the cylinder source to prevent excessive leakage.

The plurality of axially spaced support rings which are provided may each be of a slightly increasing diameter from one end to the other of the cylinder assembly. The outer cylinder sleeve member, which is supported by the rings, is in turn provided with shouldered bearing areas of progressively increasing diameter. The arrangement is such that the outer cylinder sleeve may be applied axially over the preassembled shaft and support rings, achieving a force fit therewith only over the last inch or so of axial assembly. Thus, the final assembly of the principal elements is relatively convenient and straightforward. At the same time, however, the airtight integrity of the various chambers is easily maintained.

In accordance with the invention a novel arrangement is provided for blocking off or dead ending the annular grooves to avoid leakage adjacent the ends of a vacuum-held printing plate. In this respect, after first forming continuous annular grooves in the printing cylinder, the cylinder is provided with a longitudinally extending surface groove, which is continuous from one end to the other of the cylinder. A soft metal strip is then tightly received in the longitudinal groove, to effectively block off all of the annular grooves and provide a predetermined circumferential discontinuity between adjacent ends of each groove. While it is known in the prior art to provide means for individually dead ending the annular grooves (United States Patent No.

3,112,698), the arrangement of the invention is more simplified and versatile than the prior art proposals.

The vacuum-printing cylinders, otherwise as described above, may additionally be provided with vacuum diffusion means over the outer surface areas, in the form of porous filter media or sintered, porous surface coatings. The use of porous filter media is particularly advantageous for some applications in that coverings of filter paper may be provided in various thicknesses, to compensate for different thicknesses of the printing plates which may be utilized by the printer. When using vacuum diffusion means, less consideration need be given to minimizing or avoiding leakage beyond the edges of the printing plate, because the diffusing mediums easily limit such leakage to amounts within the capacity of vacuum pumps typically used for the purpose.

For a better understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description and the accompanying drawings.

Figure 1 is a perspective view of a vacuum-operated printing cylinder illustrating features of the invention.

Figure 2 is a greatly enlarged, fragmentary cross sectional view taken generally along the line 2-2 of Figure 1, illustrating details of the internal construction of the new vacuum-printing cylinder.

Figures 3 and 4 are cross sectional views taken generally on lines 3-3, 4-4 respectively of Figure 2.

Figure 5 is an end elevational view of the cylindrical outer section only of the new printing cylinder, illustrating vacuum distribution is provided by annular grooves.

Figure 6 is a cross sectional view taken generally on line 7-7 of Figure 5, and Figure 7 is a fragmentary side view of the cylinder section of Figure 5.

Referring now to the drawings, and initially to Figures 1-4 thereof, there is illustrated a preferred internal construction for the printing cylinder in accordance with this invention. The reference numeral 10 designates generally an elongated shaft of a length suitable to extend through an entire cylinder sleeve 11 and project somewhat beyond either end thereof. Adjacent each end of the cylinder sleeve, the shaft 10 is provided with bearing areas 12, 13, by means of which the shaft is supported in the printing machine (not shown) in a conventional and well known manner. One end of the shaft is provided with a key way 14, by means of which the shaft may be driven in properly timed relation with the printing equipment.

In one form. the shaft 10 is provided in its mid region with a plurality of axially spaced supporting rings 15-17. While it is to be understood that the present invention is not in any way limited to specific dimensions, a typical printing cylinder assembly in accordance with the invention may have a working length of, for example, around 90 cm between the outer surfaces of the support rings 15, 17 at opposite ends, with the center supporting ring 16 being located approximately midway between the end rings.

Likewise. for a typical such printing cylinder, the overall outside diameter of the cylinder sleeve 11 may be on the order of 18 cm. in which case it may be convenient to construct the shaft 10 to have a diameter on the order of, say, 9 cm in its center region.

To advantage. the support rings 15-17 are welded to the shaft 10, as shown at 18.

The shaft 10 is provided at one end with an elongated axial bore 19, which is arranged to be connected at the outer end of the shaft by an appropriate rotary coupling (not shown), to a vacuum pump. In the region of the shaft 10 on which the support ing ring 17 is mounted, the shaft and ring are provided with a transverse bore 20-21 intersecting with the axial bore 19. The bore 20-21 may be formed after assembly of the supporting ring 17 onto the shaft. The bore 20-21 thus enters the support ring 17 at one side 22 and is dead ended at the other side 23. The open end 22 may be plugged, if desired, but typically will be effectively sealed off by the inner wall of the cylinder sleeve 11.

At one side, the bore 20-21 is connected to a longitudinal through bore 24, extending from one end to the other of the support ring 17. On its outer or right hand side, the bore 24 is enlarged and threaded, as at 25.

At its opposite end the axial through bore 24 is provided with a conical seat 26 arranged for cooperation with a corresponding conical surface 27 on a threaded valve plug 28.

The valve plug 28 is threadedly received in the threaded portion 25 of the through bore 24, and typically may be provided with a socket 29 for the reception of an Allen wrench. When the valve plug 28 is in a retracted position, as shown at the right hand side of Figure 2, communication is provided between the axial passage 19, the transverse bore 20-21, and the upstream or left hand extremity of the longitudinal through bore 24. When the valve plug 28 is screwed to a closed position, with the conical seats 26, 27 in engagement, the upstream end of the passage 24 is isolated from the main passage 19.

At the diametrically opposite side of the support ring 17, a blind bore 30 is provided, communicating with the bore 20-21 and opening at the left side of the support ring.

This bore is threaded to receive a union fitting 31 within the annular chamber 32 formed between the shaft 10, the support rings 16, 17 and the cylinder sleeve 11. The union fitting 31 is connected to a section of tubing 33, preferably of a semi-rigid material, such as copper. The tubing 33 is bent in a configuration to extend within the annular chamber 32 over an arc of about 180 passing around the center shaft 10 and connecting at the opposite side of the shaft to a second union fitting 34. The union fitting 34, and a similar union fitting 34a are secured within a threaded through bore in the center support ring 16, providing communication through the ring 16, which otherwise is maintained in air tight relation to the shaft 10 and to the cylinder sleeve 11.

A second section 36 of semi-rigid tubing extends around the center shaft 10 within an annular chamber 37 defined by the supporting rings 15, 16 and the shaft 10 and the cylinder sleeve 11.

The tubing 36 extends around the shaft 10 on the opposite side from the tubing 33, so that the respective tubing sections counter balance each other, and the tubing 36 connects at the opposite side of the assembly to a union fitting 35.

The union fitting 35 is secured in a threaded, dead end bore 38, which intersects with a bore 39-40 extending transversly through the support ring 15 and shaft 10. At the opposite end of the bore 39-40, is a longitudinal through bore 41, similar to the bore 24, which receives a threaded valve plug 42 similar to the valve plug 28 at the opposite end. The valve plug 42 is shown in its closed position, in which the annular chamber 37 is isolated from the bore 39-40.

Opening of the valve plug places the chamber 37 in communication with the main axial passage 19, at the other end of the shaft, through the spirally disposed tubing sections 33, 36, as will be understood.

As shown in Figure 2 in particular, the cylinder sleeve 11 is formed with internal cylindrical surfaces 43-45 which engage tightly with and are supported by the respective supporting rings 15-17. Desirably, the cylinder sleeve 11 is arranged to form an interference fit with the respective supporting rings 15-17, to assure substantial airtight integrity of the annular chambers 32, 37.

The several supporting rings 15-17 are of progressively slightly increasing diameter from one end to the other of the assembly.

By way of example only, in an assembly in which the support rings 15-17 are nominally around 15-16 cm in diameter, the rings 16, 17 may progressively increase in diameter by. for example, around 0.25 mm. In a similar manner. the inside diameter of the respective supporting surfaces 43-45 of the cylinder sleeve increase correspondingly in diameter.

In assembling the vacuum cylinder, a pre-assembly is made of the shaft 10, support rings 15-17, the tubing sections 33, 36, and the various union fittings. The premachined cylinder sleeve 11 is then applied axially over the described pre-assembly, from right to left as viewed in Figure 2. The left hand end of the cylinder sleeve. being of the largest diameter, readily clears the support rings 17 and 16, enabling the sleeve to be slid easily into position, until the last inch or so of the assembly, where interference commences between the surfaces 43-45 and the rings 15-17. Thereafter, adequate axial force, accompanied if necessary by heating the cylinder sleeve and/or cooling of the pre-assembly, is utilized to force the sleeve axially into its final, assembled position, as shown in Figure 2. Desirably, the outer joint between the end most support rings 15-17 and the cylinder sleeve 11 may be welded, as shown at 46, to secure the assembly.

Consistent with conventional printing practice, the printing cylinder is provided at each end with bearer rings 47, 48, secured adjacent the ends of the printing cylinder and having an outside diameter slightly greater than that of the cylinder sleeve 11 to provide a predetermined clearance space underneath the cylinder to accommodate the printing plate. The bearer rings 47, 48 may be secured to the support rings 15, 17 by suitable bolts 49 (Figure 1). In addition, each of the bearer rings is provided with an opening 50, aligned with the respective valve plugs 28, 42, providing access for an Allen wrench or similar tool, for manipulating the valve plugs between their opened and closed positions.

In the operation of the cylinder assembly of vacuum is applied to the cylinder surface by connecting a vacuum pump to the axial passage 19 in the shaft and opening one or both of the valve plugs 28, 42 to evacuate either or both of the chambers 32, 37. In a typical case, a flexible printing plate will be cut to a size suitable to cover the entire operating surface of the cylinder. Thus, the plate could extend axially over substantially the entire area between the inside surfaces of the supporting rings 15, 17. Where appropriate, the printing cylinder may be activated or de-activated incrementally, by means of the valve plugs 28, 42. This may be utilized to significant advantage and convenience when utilizing printing plates of less than full size. In this respect, it will be understood that, while the assembly illustrated in Figures 1-4 is provided with two independently activated chambers 32. 37, by appropriate internal piping of the assembly, any number of independently usable chambers could be provided.

Sleeve 11 is further illustrated in Figures 5-7 and is provided with a series of annular grooves 61, spaced across the working length of the cylinder sleeve. to provide vacuum communication to the underside of the printing plate.

In a vacuum printing cylinder of the proportions heretofor mentioned, the cylinder sleeve 11 may have about 40-45 annular grooves of a typical width of about .75 mm.

The grooves 61 initially are formed by machining continuous annular grooves in the surface of the cylinder sleeve. In conjunction with these annular grooves 61, the sleeve is provided with one, and preferably a pair, of axially extending surface grooves 62. Ideally, a pair of grooves 62 is provided, located diametrically opposite on the surface of the cylinder, as shown in Figure 5.

The axial grooves 62 are cut somewhat deeper than the annular grooves 61, and also have a somewhat greater width. Thus, typically, the axial grooves 62 may have a width of around 6.4 mm and a depth of about 3.1 mm. The annular grooves, on the other hand, may have a typical depth of about .9 mm.

Received in the axial grooves 62 are soft metal strips 63, which extend the full length of the cylinder sleeve 60 and typically are segmented. These strips are secured to the cylinder by a plurality of recessed screws 64, and are machined flush with the outer surface of the cylinder sleeve. The soft metal strips 63 are sufficiently tightly received in the grooves 62 to seal off the end areas 65 of the annular grooves 61, so that the grooves extend effectively over somewhat less than 1800 of the cylinder surface.

At some point along each semi-annular groove segment, typically and advantageously halfway between its ends, a radial bore 66 is provided, placing the grooves in communication with the interior annular chambers 32, or 37 of the cylinder assembly.

The bore 66 typically may be about 1.6 mm in diameter.

The chambers 32, 37 may- be independently activated, by means of the valve plugs 28, 42 (see Figure 2), so that different axial sections of the printing cylinder may be utilized, The printing plate is cut to extend around the full circumference of the cylinder, with one end being initially placed in alignment with a scribed axial line 67 and the other end ideally overlying the longitudinal sealing strip 63 with a slight clearance space from the scribed line 67, so that the two ends do not overlap, By providing for the sealing strip 63 to have a reasonable width (e.g., 6.3 mm) small margins of the printing plate, at each end, may overlap on the sealing strip, substantially avoiding air leakage in the regions of the end areas 65 of the annular grooves.

The invention provides a highly effective and entirely practical vacuum printing cylinder, which meets the day-to-day practical needs of the printer. The specifics of the design of the cylinder are such as to permit the printing plates to be held by vacuum alone. without requiring auxiliary adhesive means, mechanical clamps, or the like. In part, this is realized by an effective configuration and arrangement of flow passages through the cylinder sleeve, to achieve effective distribution of the vacuum effect while avoiding problems from excessive leakage. Important advantages are derived from the utilization of independently controllable vacuum chambers within the cylinder, which permit the application of vacuum to be confined more effectively to the size of the printing plate. This accommodates the use of smaller printing plates, as well as of multiple plates on a side-by-side basis. In the latter case, some of the plates can be removed and replaced without affecting the alignment of other plates, by maintaining the vacuum in certain chambers while removing it from others, as will be appreciated.

In any of the forms of the new printing cylinder in which the interior of the cylinder sleeve is subdivided into a plurality of chambers, it is advantageous to use a stepped construction, including a preassembly of shaft and supporting rings, with successive supporting rings increasing slightly in diameter from one end to the other.

This arrangement, in conjunction with a correspondingly stepped internal configuration of the cylinder sleeve, provides a highly practical and effective arrangement for achieving a multi-chambered cylinder construction at a practical level of manufacturing cost, The arrangement further facilitates the provision of weight-balanced internal plumbing leading to the respective chambers, in conjunction with independently operated valve elements accessible from the end areas of the cylinder.

WHAT WE CLAIM IS: 1. A printing cylinder for mounting a printing plate by vacuum power, comprising a shaft, a cylinder sleeve supported on said shaft and defining a vacuum chamber, means to evacuate said chamber, a plurality of generally continuous grooves formed on the outer surface of said cylinder sleeve, air passage means connecting each of said annular grooves with said vacuum chamber, said cylinder sleeve having at least one axially disposed groove intersecting said annular grooves and axially disposed sealing strip means tightly received in and completely filling said axial grooves to form a continuation of the outer surface of the sleeve in the circumferential direction and block said annular grooves to provide a predetermined circumferential discontinuity between adjacent ends of each annular groove, so that when a printing plate is mounted on the outer surface of said sleeve with its end edge portions overlapping said sealing strip means the plate is held on said cylinder by the vacuum power of said chamber and leakage adjacent to the ends of the vacuum-held printing plate is substantially avoided.

2. The apparatus of Claim 1, wherein said cylinder sleeve has a pair of axially disposed grooves spaced about 1800 apart, said sealing strip means being tightly received in and completely filling each of said axial grooves to divide said annular grooves into semi-annular configuration, and wherein said air passage means connects each semi-angular segment of said annular grooves with the interior of said cylinder.

3. The apparatus of Claim 1 including means subdividing said vacuum chamber into a plurality of evacuatable chambers, a primary evacuation passage extending internally of said shaft from adjacent one end thereof to a point adjacent to one end of the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. about .9 mm. Received in the axial grooves 62 are soft metal strips 63, which extend the full length of the cylinder sleeve 60 and typically are segmented. These strips are secured to the cylinder by a plurality of recessed screws 64, and are machined flush with the outer surface of the cylinder sleeve. The soft metal strips 63 are sufficiently tightly received in the grooves 62 to seal off the end areas 65 of the annular grooves 61, so that the grooves extend effectively over somewhat less than 1800 of the cylinder surface. At some point along each semi-annular groove segment, typically and advantageously halfway between its ends, a radial bore 66 is provided, placing the grooves in communication with the interior annular chambers 32, or 37 of the cylinder assembly. The bore 66 typically may be about 1.6 mm in diameter. The chambers 32, 37 may- be independently activated, by means of the valve plugs 28, 42 (see Figure 2), so that different axial sections of the printing cylinder may be utilized, The printing plate is cut to extend around the full circumference of the cylinder, with one end being initially placed in alignment with a scribed axial line 67 and the other end ideally overlying the longitudinal sealing strip 63 with a slight clearance space from the scribed line 67, so that the two ends do not overlap, By providing for the sealing strip 63 to have a reasonable width (e.g., 6.3 mm) small margins of the printing plate, at each end, may overlap on the sealing strip, substantially avoiding air leakage in the regions of the end areas 65 of the annular grooves. The invention provides a highly effective and entirely practical vacuum printing cylinder, which meets the day-to-day practical needs of the printer. The specifics of the design of the cylinder are such as to permit the printing plates to be held by vacuum alone. without requiring auxiliary adhesive means, mechanical clamps, or the like. In part, this is realized by an effective configuration and arrangement of flow passages through the cylinder sleeve, to achieve effective distribution of the vacuum effect while avoiding problems from excessive leakage. Important advantages are derived from the utilization of independently controllable vacuum chambers within the cylinder, which permit the application of vacuum to be confined more effectively to the size of the printing plate. This accommodates the use of smaller printing plates, as well as of multiple plates on a side-by-side basis. In the latter case, some of the plates can be removed and replaced without affecting the alignment of other plates, by maintaining the vacuum in certain chambers while removing it from others, as will be appreciated. In any of the forms of the new printing cylinder in which the interior of the cylinder sleeve is subdivided into a plurality of chambers, it is advantageous to use a stepped construction, including a preassembly of shaft and supporting rings, with successive supporting rings increasing slightly in diameter from one end to the other. This arrangement, in conjunction with a correspondingly stepped internal configuration of the cylinder sleeve, provides a highly practical and effective arrangement for achieving a multi-chambered cylinder construction at a practical level of manufacturing cost, The arrangement further facilitates the provision of weight-balanced internal plumbing leading to the respective chambers, in conjunction with independently operated valve elements accessible from the end areas of the cylinder. WHAT WE CLAIM IS:

1. A printing cylinder for mounting a printing plate by vacuum power, comprising a shaft, a cylinder sleeve supported on said shaft and defining a vacuum chamber, means to evacuate said chamber, a plurality of generally continuous grooves formed on the outer surface of said cylinder sleeve, air passage means connecting each of said annular grooves with said vacuum chamber, said cylinder sleeve having at least one axially disposed groove intersecting said annular grooves and axially disposed sealing strip means tightly received in and completely filling said axial grooves to form a continuation of the outer surface of the sleeve in the circumferential direction and block said annular grooves to provide a predetermined circumferential discontinuity between adjacent ends of each annular groove, so that when a printing plate is mounted on the outer surface of said sleeve with its end edge portions overlapping said sealing strip means the plate is held on said cylinder by the vacuum power of said chamber and leakage adjacent to the ends of the vacuum-held printing plate is substantially avoided.

2. The apparatus of Claim 1, wherein said cylinder sleeve has a pair of axially disposed grooves spaced about 1800 apart, said sealing strip means being tightly received in and completely filling each of said axial grooves to divide said annular grooves into semi-annular configuration, and wherein said air passage means connects each semi-angular segment of said annular grooves with the interior of said cylinder.

3. The apparatus of Claim 1 including means subdividing said vacuum chamber into a plurality of evacuatable chambers, a primary evacuation passage extending internally of said shaft from adjacent one end thereof to a point adjacent to one end of the

sleeve and spaced substantially from the other end of the sleeve, first valved passage means connecting said primary passage means to one of said chambers and including a first valve element accessible from said one end of the sleeve, second valved passage means external of said shaft but within the confines of said sleeve for connecting said primary passage means to another of said chambers and including a second valve accessible from the other end of said sleeve, and said chambers each including passage means providing flow commiinication between said chambers and the exterior surface of said cylinder sleeve.

4. The apparatus of Claim 3, wherein said second valve passage means includes a section of substantially rigid tubing extending spirally around said shaft from one end to the other of said cylinder sleeve.

5. The apparatus of Claim 4, wherein said subdividing means comprises at least three sleeve supporting elements including at least one intermediate sleeve supporting element, having an air passage transverselv therethrough. said tubing being connected to said last mentioned air passage at opposite sides of said intermediate sleeve supporting element.