Oil siphon

A shoe roll of a shoe press for use in a papermaking machine, the shoe roll including a blanket, or endless belt, which houses a shoe assembly that, in cooperation with an external backing roll, forms an extended nip proper. The shoe press includes an oil circulation piping system for removing the oil from the interior of the shoe roll and transferring the oil to an oil trap during the running of the machine, whereby the piping system also includes a suction fan connected thereto. The device is implemented by way of connecting an oil siphon to the oil circulation piping system, the oil siphon adapted to move towards and away from the blanket in the interior of the shoe roll so that, when the roll is stopped, the siphon removes the excess oil from the interior of the blanket by a pressure differential generated by of the suction fan.

This nonprovisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 20012083 filed in Finland on Oct. 26, 2001, which is herein incorporated by reference.

The present invention relates to a shoe roll of a shoe press used in a papermaking machine, the shoe roll comprising an endless belt, or a blanket; which houses a shoe assembly that in cooperation with an external backing roll forms an extended nip proper and the shoe press including an oil circulation piping system performing the removal of oil from the interior of the shoe roll to an oil trap during the running of the machine, whereby the piping system also comprises a suction fan connected thereto.

During its operation, the blanket of the shoe roll of the shoe press requires a copious volume of oil for lubrication and cooling. Hence, stopping of the roll rotation leaves in its interior a large volume of oil that cannot be removed by conventional arrangements.

In fact, prior shoe presses have lacked a separate oil removal system to cope with situations in which the roll is stopped. The greatest problem herein has especially arisen from the oil that remains in the interior of the roll and obviously lands on the bottom of the blanket. This has resulted in bagging of the blanket, whereby in worst situations it has been necessary to attempt a remedy to the problem by providing external support to the blanket. Since the oil quantity in the interior of the roll blanket may be amounted to hundreds of liters, complications have arisen in the replacement of the blanket so that the blanket replacement becomes tardy.

It is an object of the present invention to solve the removal of oil from the interior of the shoe roll of a shoe press in a papermaking machine in a simple fashion. The goal of the invention is achieved by an arrangement characterized in that to the oil circulation piping is connected an oil siphon adapted movable along the blanket in the interior of the shoe roll so that the excess oil can be removed by means of the siphon during the time the roll is stopped from the interior of the blanket by a pressure differential generated by of the suction fan.

A preferred embodiment of the invention is characterized in that the oil siphon is provided with an actuator adapted to elevate the oil siphon into an upper position when the papermaking machine is running and then to sink the siphon operational into a lower position when the machine is stopped.

Another preferred embodiment of the invention is characterized in that the actuator comprises a single-stroke hydraulic cylinder that implements the siphon elevation movement by spring force and the operational siphon sink movement by hydraulic force.

A still another preferred embodiment of the invention is characterized in that, when the machine is stopped, the shut-off valve of the oil siphon piping is driven open, whereby the pressure differential generated by the suction fan vacuums oil out from the interior of the shoe roll blanket.

The arrangement needs a very simple construction inasmuch as it operates without a separate oil suction pump, but instead, its operation is based on the existing oil removal system that can be found in any shoe press.

InFIG. 1is generally shown a shoe press. Reference numeral1denotes a shoe roll incorporating in the interior of an endless belt, or blanket4, a shoe assembly3that forms the extended-nip proper. Respectively, reference numeral2denotes a backing roll against which the shoe roll1presses a paper web W. Herein, the present invention relates to oil removal in a stopped papermaking machine from the interior of shoe roll1with the help of existing oil removal piping.

InFIG. 2is shown diagrammatically a layout of the entire oil removal system. Also in this diagram, reference numeral1denotes the shoe roll. Oil removal takes place with the help of a pressure differential generated by means of a suction fan14. Reference numeral15denotes an oil trap, while reference numerals16and7denote the removal of oil from the system. In a running machine, fixed piping11carries oil from the trough located in the upper portion of the shoe roll interior into an oil discharge pipe7. Respectively, oil is removed from the bottom of the blanket via fixed siphon pipes10into a second oil discharge pipe6. The discharge flow of oil is accomplished by means a pressure differential generated with the help of a suction fan. The flow paths can be controlled by means of shut-off valves8band8cmounted on the piping10and11. During the running of the papermaking machine, a constant level of overpressure and pressure differential is maintained between the oil discharge pipes6and7as indicated below.Δp1=vacuum contribution by suction fan14in pressure differential ΔpΔp2=overpressure contribution in pressure differential Δp, or in other terms, the overpressure in the interior of blanket4.

The present invention proper is directed to the oil siphon denoted by reference numeral9that during the running of the papermaking machine is kept apart from the roll blanket in an elevated home position (FIG. 6). In this state, shut-off valve8ais closed, whereby the pressure in the suction pipe leaving the oil siphon is unperturbed and the spring of single-stroke hydraulic cylinder13(13binFIG. 6) elevates the siphon pipe home into its upper position. Valves8band8care kept in their open positions.

After the machine is stopped, to the rod side of hydraulic cylinder13is applied a hydraulic pressure sufficiently high to overcome the spring force, whereby the oil siphon9is lowered onto the bottom of the blanket so deep that it meets the inner surface of the blanket12(FIG. 5). Herein, the hydraulic cylinder is in its retracted position13a. Next, the shut-off valve8aof the piping connected to the oil siphon9is opened and, with the help of the pressure differential generated in the piping by the suction fan14, excess oil is removed from the interior of the shoe roll blanket. During this operation, valves8band8cclose automatically.

When the papermaking machine is again started, shut-off valve8ais closed, fluid pressure to the hydraulic cylinder is shut off and the spring force of the cylinder elevates the oil siphon into its upper position. Hence, the arrangement is implemented in a very simple fashion, since oil siphon9does not need a separate suction pump, but rather, its operation is based on an existing oil discharge system normally used during the running of the papermaking machine. Reference numeral5in the diagram refers to a breather.

To a person versed in the art it is obvious that the invention is not limited to the above-described exemplary embodiment, but rather, may be modified within the scope and spirit of the appended claims.