CA1210978A

CA1210978A - Roller with an elastic cover layer

Info

Publication number: CA1210978A
Application number: CA000418169A
Authority: CA
Inventors: Rudolf Graf
Original assignee: Huber and Suhner AG
Current assignee: Huber and Suhner AG
Priority date: 1981-12-23
Filing date: 1982-12-21
Publication date: 1986-09-09
Also published as: EP0083301B2; EP0083301B1; DE3268452D1; EP0083301A1

Abstract

ROLLER WITH AN ELASTIC COVER LAYER

Abstract of the Disclosure A steel roller core is covered with an elastic cover having a polyurethane jacket. On the inside of the cover is found a rigid, fluid-impermeable, inner reinforcing tube of fiberglass-reinforced polyester. The thermal coefficient of expansion of the polyester tube is similar to that of steel. A gap or space is provided between the tube and the roller core, which gap is completely filled with adhesive. Because the jacket is seated on the rigid sleeve with prestressing as a result of thermal contraction subsequent to cooling, the cover can not separate from the roller core even under heavy loads. The cover can be mounted on the roller core by the user within a very short time. It is not necessary to ship the roller core to the resurfacing plant to renew the roller cover.

Description

7~3 ~OLLER WITH AN ELASTIC COVER
. . _ BACKGROUND OF THE INVENTION
Field of the Invention The invention relates to a roller with an elastic cover layer in which the cover layer includes a jacket of an elastomeric material and a rigid, inner reinforcing tube that is impermeable to liquid~
Prior Art .
In industry/ for example, the paper, steel and te~tile industries, as well as in commercial graphics and the other arts, a great number of rollers are required, the steel cores of which are covered with a softer, usually elastic rubber or plastic cover layer. The cover layers are applied to the roller cores by being cast, rolled or sprayed thereon. In order to achieve a good adhesion with the roller core, the core must be cleaned (degreased), sandblasted and coated with a bonding agent which provides a good bond with the cover layer through the action of heat. With certain materials, such as polyurethane, the 2C roller core and tools mus~ be heated to temperatures as high as 80 to 100 C before the cover layer is applied.
After application, some cover layers, such as elastomers, must remain in the furnace at temperatures of up ~o 170 C
for perhaps several hours for the cross-linkage process.
Thereafter; curing at a constant temperature of 25 C is often necessary which, depending on quality and cover layer thickness, may take as much a~ three weeXs.
These expensive, apparatus-intensive methods r in wh ich the roller core is directly covered, make it necessary for the industry to deliver worn rollers to resurfacing plants.
This results in production losses, and significant transport costs, due to ~he generally very heavy weight of the cores, which may weigh as much as several tons and may be up to 6 m in length.

g7~3 For many years it has been attempted to manufacture covers, also known as sleeves, which can be kept in storage, thus permitting defective cover layers to be replaced quickly. In ~arious tests it was examined whether 5 i~ is possible to glue elastomer or plastic sleeves to the roller cores. The differences between ~he materials, plastic/steel, and the heavy loads p~aced on the rollers during use (fulling stress and/or high rpms~ resulted in unsatisfactory bonds. The mounting under pressure of the soft and some~hat elastic sleeve on ~o the cores soon led to a weakening of the contact pressure, so that the bond to the steel core was entirely lost. Completely aside from these factors, however, it is only possible to force relatively short sleeves onto the steel cores.
For this reason it was attempted to manufacture reinforced sleeves by embedding fabric or a metal screen cylinder in the cover material. In this case the co~Jer material permeates the reinforcement, 50 that the inner layer of the ~leeve is made of the same material as the cover~ The weakening of the prestress experienced in forcing on the cover was thus avoided in part/ but problems were experienced in maintaining proper tolerances.
Difficulty was also experienced in forcing the sleeve onto long cylinders.
Prior art development has been primarily directed toward the textile industr~, where short and small diameter spindles and rollers must be covered. However, as soon as rollers longer than 100 mm were provided with the known sleeves, severe difficulties developed. It turned out, for example, that under the heavy loads involved (linear compression of up to 100 N/mm) due to the resulting fulling stress, the sleeves became greatly heated (up to 80~ C) and the different thermal expansion coefficients caused a separa~ion of the sleeve from the roller core. In direct vulcaniza~ion of the cover to the roller core this problem does not occur, because subsequent to the vulcanization a tnermal contraction takes place which leads to a prestressing that compensates Eor even the greatest thermal expansion during operation.
SUMMARY OF THE INVENTION
An object of this invention is ~o create an elastic cover for a roller, which cover is reinforced for added strength and has an inner layer ~hat makes possible a proper bonding to the roller while simultaneously being able to accommodate close~ tolerances than known covers.
The cover should be able to be stored at the site of the user industry and te able to be quickly mounted on the rollers, without these rollers having to be sent in to the resurfacing factory. The importan~ fac~or is proper adhesion of the cover layer to the roller, even under extreme loads.
Thi~ is achieved by having the thermal coefficient of expansion of the tube approximately correspond to that of the core with an adhesive-filled annular gap between the tube and the core.
BRIEF DESCRIPTION OF T~E DRAWINGS
.
Fig~ 1 is a schematic part-sectional view of a first exemplary embodiment for the manufacture of the elastic cover, Fig. 2 is a view similar to Fig. 1 showing the mounting of the cover according to Fig. 1 on a roller core~
Fig. 3 is a perspective view of a roller with the cover in place thereon, Fig. 4 is a schematic part-sectional view of a further exemplary embodimen~ for the manufacture of the cover, Fig. 5 is a view similar to Fig. 4 showing the cover according to Fig. 4 being mounted onto a roller core, Fig. 6 is a cross section through the band like original material for a third exemplary embodiment of an elastic cover, 7~3 Figs. 7 and 8 schematically show the manufacture of a cover made from the band according to Fig. 6, and Fig. 9 is a cover rnanufactured from the band material.
DETAILED DE~CRIPTION OF THE PREFERRED EMBODIMENTS
_ .
According to Fig. 1, the first step in the manufacture of the cover, also called a sleeve, is the casting of a polyurethane ring base 1. The outer circumference of the ring base 1 has offset steps, whereby three ring steps 2, 3, 4 of different diameters are provided.
A tube 5 of fiberglass-reinforced polyester serves as inner reinforcement for the sleeve. The inner diameter d1 f this tube is about 1 to 5 mm larger than the outside diameter d2 f the steel ro1ler 6 to be covered.
The polyester tube is thermally stable and absolutely rigid up to temperatures of 120 C. It is impermeable to liquids and bonds completely with the material of jacket 7 of the sleeve. Its thermal coefficient of expansion is comparable to that of steel ~thermal coefficient of steel: approx.
12.0 x 10-6/C)o The thermal coefficient of expansion of the polyester tube should be ~ 15.0 x 10-6/C. The thickness of the tube is 1.5 to 4 mm.
Other rigid materials could also be used in place of the fiberglass-reinforced polyester tube~ or example a sheet metal sleeve. The manufacture and preparation of a metal sleevet however, is relatively expensive and the bond with the polyurethane material and the adhesive can only be achieved through expensive pretreatments, which is not necessary with the polyester tube 5. The end of the polyester tube 5 is then fitted onto the second ring step 3 of the ring base 1, whereby the polyester tube serves as a break mold or hidden casing. It can be tightly bonded to the ring base 1 for example with an epoxy adhesive 9.

~Uql~

The end of a steel tube 8 is fitted onto the outside ring step 2 as an outer casing for the polyurethane jacket material~ which is hot cast at a temperature of ao to 120~ C and bonds with the ring base 1. After the casting and cross-linkage, ~hich takes about 8 to 10 hours, the finished sleeve, consis~ing of the jacket 7, the reinforcement 5 and the ring base 1, can be pulled frorn the outer casing 8. As a result of the hot casting~ a thermal contraction takes place due to cooling, which leads to a prestressing of the jacket onto the reinforcement.
The sleeve is then delivered to a user operation and stored there until used~ If necessary, the sleeve can be mounted immediately onto the roller core, as shown schematically in Fig. 2.
The sleeve is pushed onto the roller core 6 until the ring base 1 meets the face surface 10 of the roller~ The clearance S between ~he roller surface and the inner surface of the sleeve is 0.5 to 2.5 mm. For purposes of the invention ~he sIeeve is also centered on the roller core, so that the clearance, i.e. the gap 13, is equalized all around. The sleeve can then be placed in a vertical position.
A hole 12 is then drilled through the sleeve in the vicinity of the annular space 11, which is bounded by the third step 4 of the ring base 1 and the face surface 10 of the roller. A solvent-free adhesive with a polyester, epoxy or polyurethane base is then forced through this bore 12 into the annular space 11 under a pressure o up to 10 atm. The adhesive should not be overly viscous. A
viscosity of under 2500 cp has been shown to be most satisfactoryO The adhesive then flows into the gap 13, completely filling sameO
Extensive tests have shown that the sleeve does not separate frGm the roller ccre even under heavy loads and heating. Because the polyurethane ~acket 7 is arranged on '7~

the rigid reinforcing tube 5 prestressed, an increase in temperature leads at ~ost ~o a reduction of the prestress, not to a separation from the reinorcing tube 5~ This tube, which possesses a thermal coefficient of expansion comparable to the steel core, expands a~ an eg~al rate with this core and can therefore also not separate fro~ the core~ The pressure injected adhesive produces a secure bond between the reinforcemer1t and the roller core.
The advantages of the above-described sleeve are again summarized below:
- The sleeve can be mounted on the roller core on site by the user, can be bonded at room temperature and subsequently externally turned and/or ground. The hardening of the adhesive takés place within a few hours. The troublesome shipment of rollers back to a resurfacing plant can be avoided.
- The sleeve is suitable for rapid re~covering of both small and even the largest roller cores.
- It has a superior bond with the steel core and withstands the hiqhest linear pressures and fulling stresses.
- It can be manufactured in advance and stored at the user's site, whereby the lost production time due to the re-covering process is decreased and the cost of transportation is reduced.
- Expensive preparation processes such as sandblasting, bonding agent application, etc.~
are eliminated. The surface of the roller core requires no special structure; it is sufficient if the surface is ~urned and subsequently degreased. Small variations in diameter are compensated for by the adhesive layer.

9~

- The sleeve can be manufactured extremely economi~ally, both with regard to quality and price.
- Because of a large clearance of between 0.5 to

2.5 mm beiween the rol1er core and the sleeve, the requirements with respect to manufacturing tolerances are relatively small.
The s~eel cores do not need to he heated to temperatures of from 80 to 170 C during the cross-linking of the cover layer.
- The sleeves do not need to be forced onto the rollers, but can simply be pushed thereon without the exertion of force.
- If a colorless p3lyester material is used for the reinforcing tube, the adhesion of the polyurethane jacket to the reinforcing tube can be checked. This type of simple visual checking is not possible with direct casting of the cover layer onto the roller core.
- In rollers used in intaglio printing, the reinforcing tube and the adhesive form an electrically insulating layer between the polyurethane jacket and the roller core. As is well known, in intaglio printing electrostatic 2S printing assists are employed to improve the printing quality. Until now~ the outer, conductive layer of the polyurethane cover (the conductivity is achieved, for example, by adding carbon black) had to be cast on an inner, insulating polyure~hane layer. This expensive, double casting process can now be avoided.
In a further exemplary embodiment according to Figs. 4 and 5, the reinforcing tube 5 and the steel tu~e 8 are inserted vertically into the annular groQve 14 of a steel plate 15~ whereby an additional sealing ring 16 is arranged :~2~ 7~

between the end of the steel tube 8 and the base of the annular groove 14. The annular groove 14 and the inner surface of the steel tube 8 are coa~ed w-th silicone, in order to facilitate the later removal of the sleeve.
The casting of jacket 7 in ~he space between ~he two tubes 5,8 takes place from the bottom toward the top through the opening 17 in the lower portion of the steel tube 8. This has the advantage that the casting process can be precisely guided and performed in a controlled manner, which is particularly important with exacting qualities of polyurethaneO The cross-linking then also takes place from the bottom ~oward the top.
This demQnstates one of the ad~antages of the new method. In the known process of casting the jacket directly onto the roller core, the danger existed that cracks would form and the bond would be lost beca~se of thermal and contraction tensions due to nonuniform cooling.
A different thermal potential of the roller core also had to be taken into consideration, depending on the size and volume of the roller core, which strongly influenced the cross-linking process. These influences could only be determined to some extent after several casting attempts, on a trial and error basis, with corresponding losses.
With a thin reinforcing tube, however, the thermal potential is small and can be well controlled during the casting process.
To mount the finished sleeve 5,7 on the roller core 6, the roller core 6 is placed in the vertical on a plate 18, whereby a polyurethane support ring 19 is arranged between the plate and the end 10 of the roller core 6. The outside diameter of this polyurethane support ring 19 is smaller than the core diameter of the sleeve. A seal 20 made of felt is located on the plate 18.
To center the sleeve, plastic spacers 21 are bonded to the surface of the roller core 6 with an epoxy-based adhesive. Three to six such spacers are placed at the top and at the bottom~ With longer rollers it may be necessary to place an additional three to six such spacers near the center.
The sleeve is then slipped over the roller core 6 and is again rigidly connected therewith by the injectlon of adhesive. In order to prevent the sleeve from separating from the base plate during the bonding process, the sleeve is best strapped down on the plate 18. After the ~lue has set, the roller with the sleeve is externally turned and/or groundO The overflow is removed at both bottom and top, so that the sleeve is flush with ~he end 10 Gf the roller. By means of the spacers 21, a proper centering of the sleeve on the roller core is assured.
In renewing the cover layer, the old layer is first removed from the roller by being turned down to the roller core, whereby a shaving is usually al50 removed from the roller core. For this reason the roller cores of older rollers have increasingly smaller diameters which, however, does not matter in renewing the cover layers with the present method. The somewhat enlarged annular gap 13 simply requires somewbat more adhesive and correspondingly higher spacers to be glued in place in centering the sleeve.
With smaller rollers, under certain conditions the injection of ~he adhesive can be dispensed with. The sleeve can be covered on the inside with a layer of an absorbent, compressible material, for example a felt material or a fabric. To cover the roller, the absorbent layer of the sleeve is saturated with adhesive and the sleeve is forced onto the roller, so that the adhesive serves as a lubricant during forcing of the sleeve on the roller.
The manufacture of a sleeve will be described below, in accordance with Figs. 6 and 9, said sleeve having an absorbent layer. In the manufacture of the sleeve, one starts with a band-like reinforcing material 22, which consists of a polyester felt 23, a screen fabric 24 and a cover layer 25 of polyurethane coated on the sc~een fabric ~4. The reinforcing band 22, which is about 2 to

3 mm thick depending on the roller diameter, is wound onto a mandrel, such as a steel tube 26, whereby the felt is on the inside and the coating is on the outside.
The abutting edges 27 are covered with a narrow band of polyurethane foil 28 and welded together. In this manner the felt is protected from absorbing the sleeve material during the casting, mounting and duri~g the cross-linking process of the sleeve material. Penetration in such a case would jeopardize the sub~equent bonding.
In another process according to Fig. 8, a wider band 22 is placed about the mandrel 29 and the abutting edges 27 are also covered, glued or welded.
The covered mandrel 26 is then placed in a tube 29 of larger dia~eter, and the intermediate space 30 is filled with polyurethane by casting. For purposes of this invention, the larger tube 29 stands in a furnace, so that the casting can take ~lace directly in the furnace. After the casting and cross-linking, which lasts for about 8 to 10 hours, the finished sleeve 31, consisting of the jacket 32 and the reinforcing layer 22, can be re~oved.
The jacket material can also be sprayed on. In place of polyurethane, the jacket can also consist of rubber, which is rolled on and then vulcanized~
The finished sleeve achieves a perfect bond with the roller and accepts wider tolerance differences. Prior to mounting the sleeve, the absorbent, compressible inner layer is completely saturated with adhesive. The liquid adhesive acts as a lubricant, so that the sleeve can be mounted on the roller core without great exertion of force.
The compressible polyester layer makes possible a certain amount of play, which is necess~ry during mounting. The setting of the glue takes place at room temperature within a few hours.

9~

As with the first exemplary embodiments according to Figs~ 1 through 5, also this cover layer is made from the elastic jacket material 32, the adhesive-saturated felt as reinforcement, and a thin adhesive layer between the reinforcement and the roller core r The reinforcement, which is rigid after the hardeniny of the glue, has a thermal coefficient of expansion which at least approximates that of the roller core~

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In combination: a sleeve member and a core member, said sleeve member having at least one rigid inner reinforcing tube and an elastic cover layer united integrally with the outer surface of the tube, the internal wall of said reinforcing tube telescopically receiving the core member and defining thereby an annular gap to receive an adhesive, said adhesive prior to setting, having a viscosity sufficiently low to fill substantially the entire gap if applied under pressure and the thermal coefficient of expansion of said reinforcing tube substantially corresponds to that of the core member, that upon setting of the adhesive the sleeve member and core member define an integrated roller with substantially constant thickness of the annular gap under varying working temperatures.

2. The combination according to claim 1, characterized in that the core member is made of steel and that the reinforcing tube is a fiberglass-reinforced polyester tube, the thermal coefficient of expansion of which is ? 15.0 x 10-6/°C.

3. The combination according to claim 1, characterized in that spacers which project into the annular gap are bonded to the core member, the height of which spacers corresponds to the thickness of the annular gap for the purpose of centering the cover on the core member.

4. The combination according to claim 1, characterized in that the thickness of the reinforcing tube is 1 to 4 mm and that the inner diameter of the tube is larger than the diameter of the core member by 1 to 5 mm.

5. The combination according to claim 1, characterized in that the adhesive is a solvent-free adhesive based on polyester, epoxy or polyurethane.

6. The combination according to claim 1, characterized in that the cover layer is provided with a ring base on which the face surface of the core member lies, where by an annular space is formed between the ring base and the face surface to receive and distribute the adhesive to the annular gap.

7. The combination according to claim 6, characterized in that at least one bore opening into the annular space is provided in the cover, through which bore the adhesive can be introduced into the annular space.

8. The combination according to claim 1, characterized in that the elastomeric jacket material is polyurethane.

9. The combination according to claim 1, characterized in that the jacket material is seated on the tube, prestressed, due to thermal contraction.

10. The combination according to claim 1, characterized in that the reinforcing tube includes an inner layer of an absorbent, compressible material, as well as an outer cover layer adjacent the jacket material, which cover layer is made of a material that is impermeable to liquids.

11. The combination according to claim 10, characterized in that a screen fabric is arranged between the cover layer and the material, and the cover layer is coated on this screen fabric.

12. The combination according to claim 10, characterized in that the compressible material is a felt, and that the cover layer consists of a thermoplastically bondable material, which undergoes a complete bonding with the jacket material.

13. The combination according to claim 12, characterized in that the felt is a polyester felt, and that the cover layer is made of polyurethane.

14. Method for the manufacture of a roller core and an elastic cover layer arranged thereon, whereby the cover layer includes a jacket of an elastomeric material and a rigid, inner reinforcing tube that is impermeable to liquid, characterized in that the thermal coefficient of expansion of the tube at least approximately corresponds to that of the roller core, and that an adhesive-filled annular gap is arranged between the tube and the roller core, said method being characterized in that the cover is premanufactured and is subsequently mounted on the roller core and that the adhesive is pressed into the annular gap under pressure through at least one bore in the cover, and from this annular gap the adhesive is uniformly distributed between the tube and the roller core.

15. Method according to claim 14, characterized in that a plurality of cover-centering spacers are glued to the roller core at least at the top and bottom thereof before the cover is mounted.

16. Method according to claim 14, characterized in that the adhesive is pressed into the annular gap with up to 10 atmospheres of pressure, whereby its viscosity lies below 2500 cp.

17. Method according to claim 14, characterized in that the adhesive is pressed into an annular space arranged beneath the annular gap and communicates therewith, whereby the adhesive flows in the annular gap from the bottom toward the top.

18. Method according to claim 14, characterized in that in the premanufacturing of the cover, the jacket material is cast in a mold formed by an inner fiberglass-reinforced polyester tube serving as a hidden casing in an outer casing tube, and that after the cross-linking and cooling of the jacket material, the cover, consisting of the jacket and the tube, is removed from the outer casing.

19. Method according to claim 18, characterized in that to form the mold a polyurethane ring base having offset steps on its outer circumference is manufactured, that the end of the fiberglass-reinforced polyester tube is placed over an inner step of the ring base and that the end of the tube serving as the outer casing is pushed onto the outermost step of the ring base.

20. Method according to claim 18, characterized in that the inner polyester tube and the outer casing tube are inserted in an annular groove of a base plate to form the vertical mold, and that subsequently the polyurethane jacket material is introduced through a lower lateral opening in the outer casing tube, so that the casting process takes place from the bottom toward the top.

21. Method according to claim 14, characterized in that the polyester tube is provided on the inside with a layer of an absorbent, compressible material, that this layer is saturated with adhesive, and that the cover is then mounted on the roller.

22. A roller comprising a premanufactured sleeve member having at least one inner reinforcing tube and an elastic cover layer united integrally with the outer surface of the tube, which tube is telescopically disposed about a core member defining an annular area therebetween, and a concentric tubular adhesive coat filling said annular area, and the thermal coefficient of expansion of said reinforcing tube substantially corresponds to that of the core member as to define an integrated roller with substantially constant thickness of the concentric tubular adhesive coat under varying working temperatures.