TW201511858A - Rolling mill laying head - Google Patents

Abstract

Aspects of the present invention relate to a rolling mill laying head. The rolling mill laying head comprises a quill rotatable about a central axis, said quill being equipped with a guide pathway configured and arranged to form a longitudinally moving product into a continuous series of rings; a stationary support structure; and axially spaced radial bearings supporting said quill for rotation about said axis, one of said bearings comprising a hydrostatic oil film bearing having an internal diameter of at least about 500 mm, and having a L/D ratio less than 0.25.

Description

Rolling mill application head

Embodiments of the present invention relate to an application head of the type used in a rolling mill for forming a hot rolled product into a helical loop.

In a conventional dispensing head, a static support structure includes a hollow core tube rotatably supported between axially spaced bearings. The central tube is provided with a guiding passage, which generally comprises: a curved conduit having an entry end aligned with the axis of rotation of the central tube; and a curved intermediate portion projecting from the central tube to the central portion in a cantilever manner The tube core is radially spaced apart from the outlet end. The central tube is rotatably driven by a known mechanism that is configured to receive the product at its entry end and form a helical loop of product output from its outlet end.

Roller bearings are commonly used to rotatably support a core tube. In the case of high speed operation, for example, when the processed product moves at a speed exceeding 100 m/sec, it has been empirically shown that the roller bearing is susceptible to vibration and interferes with the operation of the application head.

Many programs have been designed to try to eliminate or at least suppress such vibrations. The cantilever portion of the catheter has been shortened to increase the overall rigidity of the applicator head, as described in U.S. Patent No. 5,590,848. Moreover, as described in U.S. Patent No. 7,086,783, double preload roller bearings used to be Used to reduce the running clearance. Although this design improvement has proven to be advantageous, it is not sufficient to solve the vibration problem, since the application head is operated at an unprecedented high speed in a modern rolling mill, so that the vibration problem continues to jeopardize the application head.

Instead of a roller bearing, a hydrodynamic bearing has also been proposed as described in U.S. Patent No. 8,004,136 B2. In a typical hydrodynamic bearing, as illustrated in FIG. 4, a rotating member 10 is surrounded by a bushing 12. The rotating member is subject to a load applied and the low pressure oil 16 is introduced between the rotating member and the bushing via a recess 17 in the inner bushing surface.

The rotating member forms a single pressure field "P" due to a combination of parameters including the rotational speed of the rotating member, the applied load, the radial gap between the rotating member and the bushing, and the viscosity of the oil. The force combined by the pressure field is just balanced with the applied load, and the centerline 18 of the rotating member 10 is offset from the centerline 20 of the bushing 12, causing an eccentricity "E" that varies with the above parameters.

Dynamic hydraulic bearings are a mature technology and are developed by Raimondi & Boyd (AARaimindi and John Boyd, Lubrication Science and Technology, 1958, Pergamon, New York) "A Solution for the Finite Journal Bearing and Its Application to Analysis and Design, Parts I, II, III" in the journal ASLE (Literature and Environmental Society) in "vol.1, no.1, pp.159~209" The proposed graphic solution is still widely used in bearing designs. This design technique is effective for a specific range of Sommerfeld numbers and bearings with specific geometric relationships. For example, at 0.25, 0.50, 0.75 And the numerical solution of the specific length-diameter (L/D) ratio of 1.0 (as shown in Figures 5A and 5B), the solution of the bearing between these equivalents is interpolated.

There are many potential problems when operating a hydrodynamic oil film bearing under high speed and light load. E.g:

It is known that the bearing suffers from an unstable effect called "whirl" in which the rotating member rotates around the inside of the bushing in a mode that is not highly desired.

● Unusual application of the application head, depending on the operation, there is an additional temporary load at almost any angle when the hot rolled product is facing the application tube. Most hydrodynamic bearings are designed to withstand only one load in a major direction (usually vertical, as shown in Figure 4). Ideally, a well-adapted application head must be able to withstand the reaction forces of the rotating elements due to gravity, plus the temporary load being applied at any possible angle by the product entering the application head.

• Dynamic hydraulic oil film bearings require a high starting torque to overcome the static friction of the rotating member that is stopped on the bushing. Once the rotation begins, the required torque drops dramatically. The application of the head drive motor and gear set must be sized to handle higher starting torques.

Dynamic hydraulic oil film bearings have the above problems in the application of the application head. However, when given the operating speed, the convolution is a particularly critical issue because the high speed and low load do cause the bearing to always operate in an unstable situation.

For example, a typical application for a dispensing head may require a bearing of 600 mm diameter. Conventional hydro-hydraulic bearings have an L/D ratio of not less than 0.25 and a gap of typically 0.60 mm. Assuming a rotational mass of 40kN or less and a typical oil viscosity of 100cSt, the bearing will have the predicted maximum oil film temperature as a function of speed:

In a wire rod rolling mill, the spiral loops output from the applicator head are typically stored in an overlapping manner on the conveyor belt. The loops are controlled to cool as they are transported by the conveyor belt to the transfer station and gathered into a coiled shape.

During the normal rolling operation, the speed of the application head can be controlled to perform the so-called "wobble" and "tail acceleration" functions. The swing control function is generally used in larger product sizes such as 10.0 mm and larger, and is used to periodically change the speed of the application head to above the normal speed to produce a difference in the inside of the transition chamber. The size of the loop forms a denser coil with a reduced height. The end acceleration function is achieved by increasing the rotational speed of the application head once the tail end of the product is output, and is no longer driven by the application head nip roller.

The overall system stability of the hydro-hydraulic bearing is severely compromised when the swing function is performed at a lower operating speed when handling larger product sizes because the load zone continuously continually moves from the bearing in response to interactive acceleration and deceleration. Move one side to the other side. The rapid acceleration during the acceleration of the tail end is equally detrimental to the stability of the bearing.

Although hydrodynamic oil film bearings have been introduced into the rolling mill application head, they may not be widely accepted due to the above problems.

It is an object of the present invention to provide a roll mill application head incorporating a novel and improved hydrostatic oil film bearing that overcomes or at least reduces the problems associated with mechanical roller bearings and hydrodynamic oil film bearings.

In an embodiment of the invention, the core tube of the applicator head is rotatably supported by a plurality of bearings, wherein at least the bearing at the output end of the applicator head is a hydrostatic oil film bearing. Instead of a single pressure field formed passively in response to the rotation of the core tube in the case of a hydrodynamic oil film bearing, the hydrostatic oil film bearing of the present invention provides a recess that is actively pumped into the bushing at angular intervals The plurality of independent pressure fields formed by the high pressure oil. The recesses are configured such that their associated pressure fields will compress the concentric tubes in concentric alignment with the bushings held during continuous operation of the applicator head, thereby reducing and ideally eliminating vibrations caused by eccentricity. A plurality of pressure fields are also used to separate the core tube from the surface of the bushing prior to the rotational start of the core tube, so that it does not require a higher starting torque to provide the drive gear set.

The overall stability of a hydrostatic bearing does not vary with the speed of the bearing, ie the hydrostatic bearing does not rely on the speed/geometry of the wedge to lift and the centering of the rotating mass. Because the inherent design of hydrostatic bearings allows the centering of the rotating mass regardless of the applied load or speed, this bearing has significant operational advantages over dynamic hydraulic bearings, especially during the swinging cycle.

10‧‧‧Rotating components

12‧‧‧ Bushing

16‧‧‧Low-pressure oil

17‧‧‧ recess

18‧‧‧ center line

20‧‧‧ center line

22‧‧‧Stop head

24‧‧‧ 通心管

26‧‧‧ catheter

26a‧‧‧Enter

26b‧‧‧Bending middle section

26c‧‧‧export end

28‧‧‧Standing support structure

30, 32‧‧‧ bearing

34, 36‧‧‧ gears

38‧‧‧ Bushing

40‧‧‧ recess

42‧‧‧Supply conduit

44‧‧‧Distribution header

46‧‧‧High pressure pump

50‧‧‧ oil storage tank

52‧‧‧ check valve

54‧‧‧ valve

48‧‧‧Independent pressure field

D‧‧‧ Inner diameter of the bushing

E‧‧‧eccentricity

P‧‧‧ single pressure field

X‧‧‧Central Axis

These and other features and their additional advantages will be described in detail with reference to the drawings in which: Fig. 1 is a partially cutaway view of a dispensing head having a hydrostatic oil film bearing in accordance with an embodiment of the present invention.

Figure 2 is a cross-sectional view taken through the hydrostatic oil film bearing of Figure 1.

Fig. 3 is a graph comparing the measured operating temperature of a hydrostatic oil film bearing according to an embodiment of the present invention with a predicted operating temperature of a hydrodynamic oil film bearing of a comparable size.

Figure 4 is a cross-sectional view of a prior art hydrodynamic oil film bearing.

5A and 5B are respectively an end view and a side view of the bushing in the hydrodynamic oil film bearing shown in Fig. 4.

The gap between the rotating member and the bushing in Figures 2 and 4 is exaggerated for the sake of explanation.

Referring first to Figure 1, the dispensing head 22 includes a core tube 24 that is rotatable about a central axis "X". The central tube is provided with a guiding passage, one non-limiting example being a conduit 26. The conduit has an entry end 26a aligned with the axis X, a curved intermediate portion 26b, and is directed to an exit end 26c that is radially spaced from the axis X. The core tube is contained in a stationary support structure 28 and is rotated about the axis X by axially spaced bearings 30, 32. The bearing 30 can include two back-to-back tapered roller bearings, and the bearing 32 at the output end of the dispensing head is a hydrostatic oil film bearing in accordance with an embodiment of the present invention. The core tube is rotatably driven by a conventional drive gear set containing the twisted gears 34, 36 and driven by a gearbox and motor (not shown).

Referring additionally to Figure 2, the hydrostatic oil film bearing includes a bushing 38 that encloses the journal surface of the core tube 24. A plurality of angularly spaced recesses 40 are provided on the inner surface of the bushing. Referring again to Figure 2, the recess 40 is coupled to the distribution header 44 via a supply conduit 42 which is coupled to the distribution header 44 and then to a primary supply that may include a high pressure pump 46. The high pressure oil supplied to the recess 40 forms an independent pressure field 48 that acts during static conditions prior to starting to raise the journal surface of the core tube from the surface of the bushing and subsequently operate at the application head. During this time, regardless of the speed at which the heart tube is driven, the heart tube can be forced to be concentrically aligned with the bushing and held there. Thus the eccentricity is eliminated or at least reduced to a tolerable level. By raising the journal surface of the core tube from the surface of the bushing prior to starting, the friction is reduced thereby eliminating the need to increase the starting torque.

In the application of the application head, the inner diameter D of the bushing 38 is large, typically ranging from about 500 mm to 1000 mm. The load is very light and has a rotating mass of 40kw or less. In accordance with embodiments of the present invention, and in order to increase a particular load, the length L of the bearing is intentionally shortened such that the L/D ratio is less than 0.25, while tests have shown to be particularly advantageous when the L/D ratio is as low as 0.15.

Although the use of such large diameter and narrow hydrostatic oil film bearings is theoretically unfounded, tests have shown that such bearings advantageously reduce the heating of the bearings. For example, the bearing temperature is measured during the test in which the application head of the hydrostatic oil film bearing is mounted in accordance with an embodiment of the present invention. The hydrostatic oil film bearing has a size comparable to that of the aforementioned hydrodynamic oil film bearing. The design is similar to that shown in Figure 2 except that the bushing has 8 Instead of 5 equally spaced pressure pads. As can be seen from Fig. 3, the measured temperature of the hydrostatic oil film bearing is greatly lowered as compared with the predicted temperature of the hydrodynamic oil film bearing.

An advantageous reduction in fuel consumption and power loss can also be expected when a dispensing head equipped with a hydrostatic oil film bearing in accordance with an embodiment of the present invention is provided.

A rolling mill that produces a hot rolled small diameter product such as a 5.5 mm round bar operates at a very high speed. In the event of a power outage, and due to the inertia of the rotating element, the rolling opportunity needs to be "coast down" to zero speed down to 45 seconds or more. In accordance with another embodiment of the present invention and in order to ensure that the hydrostatic oil film bearing of the present invention maintains the supply of high pressure oil during this deceleration, an auxiliary supply mechanism is used to store the high pressure oil in a standby mode. As shown in Fig. 2, the auxiliary supply mechanism includes an oil reservoir 50 for supplying high pressure oil for filling by the high pressure pump 46. The check valve 52 is installed between the oil reservoir 50 and the high pressure pump 46, and a normally open valve 54 is installed between the oil reservoir 50 and the header tank 44. The solenoid valve is actuated to close the valve 54 during normal operation. In the event of a power outage, the solenoid valve automatically opens the valve 54 to connect the sump 50 to the header tank 44, thereby ensuring that the bearing 32 maintains its hydrostatic pressure during the downward reduction.

As can be appreciated from the foregoing, the skilled artisan can maintain a substantially constant concentric alignment with the bushing by using a hydrostatic oil film bearing in accordance with an embodiment of the present invention, and this is when the dispensing head is operated. Speed can be achieved regardless of speed. Thus, the vibration problems caused by the whirling in the hydrodynamic bearing and the mechanical roller bearing can be eliminated or at least significantly reduced to the extent that the high speed operation of the applicator head is no longer hindered. Here at the same At the same time, additional advantages such as low operating temperature, reduced fuel consumption and power loss, and low starting torque can be generated.

The foregoing description has been used to illustrate the invention but is not intended to be limiting. Since the above embodiments of the present invention can be further modified by those skilled in the art, the scope of the present invention is limited only by the accompanying claims and their equivalents.

22‧‧‧Stop head

X‧‧‧Central Axis

24‧‧‧ 通心管

26‧‧‧ catheter

26a‧‧‧Enter

26b‧‧‧Bending middle section

26c‧‧‧export end

28‧‧‧Standing support structure

30, 32‧‧‧ bearing

34, 36‧‧‧ fit gear

Claims (8)

A roll mill application head comprising: a core tube rotatable about a central axis, the core tube having a guiding passage configured to be configured to form a longitudinally moving product into a continuous series of loops; a support structure; and an axially spaced radial bearing for supporting the centripetal tube to rotate about the axis, one of the bearings comprising a hydrostatic oil film bearing having at least about 500 mm Inner diameter, and has an L/D ratio of less than 0.25. The application head of claim 1, wherein the L/D ratio is between 0.25 and 0.15. The application head of claim 1, wherein the hydrostatic oil film bearing comprises a bushing surrounding a journal surface of the core tube; a plurality of angularly spaced recesses disposed in the bushing; and a main supply mechanism Providing oil to the recess via a supply header under high pressure, thereby forming a separate pressure field acting on the journal surface for forcing the core tube to be concentrically aligned with the bushing. The application head of claim 3, wherein at least three of the recesses and associated pressure fields are provided in the bushing. A dispensing head according to claim 3 or 4, wherein the recesses are equally spaced along the circumference of the bushing. The application head of claim 3, further comprising an auxiliary supply mechanism for supplying high-pressure oil to the hydrostatic bearing in the event that the supply of oil from the supply mechanism is interrupted. The application head of claim 6, wherein the auxiliary supply mechanism comprises an oil reservoir filled with high pressure oil supplied by the main supply mechanism. A roll mill application head comprising: a core tube rotatable about a central axis, the core tube having a guiding passage configured to be configured to form a longitudinally moving product into a continuous series of loops; a support structure; and axially spaced radial bearings for supporting the centripetal tube to rotate about the axis, one of the bearings comprising a hydrostatic oil film bearing having a diameter of at least about 500 mm a diameter having an L/D ratio of less than 0.25, the hydrostatic oil film bearing comprising a bushing surrounding a journal surface of the core tube, having at least three angularly spaced recesses in the bushing; a main supply mechanism for supplying oil to the recess via a supply header under high pressure, thereby forming an independent pressure field acting on the surface of the journal for forcing the core tube to be concentric with the bushing Alignment; and an auxiliary supply mechanism for supplying high-pressure oil to the hydrostatic bearing when the supply of oil from the supply mechanism is interrupted.