WO2010146021A1

WO2010146021A1 - Electric capstan for drawing machines or for other machines for processing rod, wire, strip or rope, of any material

Info

Publication number: WO2010146021A1
Application number: PCT/EP2010/058316
Authority: WO
Inventors: Enrico Conte; Roberto Conte; Valentino Grandi; Alessandro Poma
Original assignee: Samp S.P.A.
Priority date: 2009-06-17
Filing date: 2010-06-14
Publication date: 2010-12-23
Also published as: IT1394276B1; ITBO20090392A1

Abstract

Electric capstan for drawing machines or for other machines for processing metal or nonmetal rod, wire or strip, said capstan (C) being characterized in that it is mounted directly on the shaft (103) of an electric torque motor or similar motor (3), of suitable characteristics, with internal support bearings (9, 22) suitable for the purpose, with a stator (203, 503, 403) mounted at a right angle on the rear face of a vertical support shoulder (1), on the front face of which said capstan is located, this shoulder having a hole (2) for the passage of said shaft (103) which passes through at least one cover (4) with sealing means (5, 105), which closes said hole (2) to protect the motor (3), for example to prevent the cooling and lubricating liquid surrounding the capstans and dies from leaking through towards the motor.

Description

TITLE:

"ELECTRIC CAPSTAN FOR DRAWING MACHINES OR FOR OTHER MACHINES FOR PROCESSING ROD, WIRE, STRIP OR ROPE, OF ANY MATERIAL"

DESCRIPTION

The invention refers particularly to machines for drawing metal rod, strip or wire, which have a series of dies through which the wire is pulled by successive pulleys or drums, known as capstans, in the process undergoing a progressive reduction in its cross section. Both the dies and the capstans run in a liquid bath which is continuously renewed, for both cooling and lubrication. In this process it is important to maintain a predetermined tension on the wire between one capstan and the next because the wire itself becomes longer as it passes through each die, so that, for the same diameter of these capstans, the capstans must rotate at progressively increasing speeds in order to maintain the tension of the wire and ensure correct contact pressure between the wires and the capstan. This tension, which must never be so great as to make the wire yield and start to break, is ensured by adequate contact pressure between the wire and the capstan which, if maintained at optimal values, generally improves the quality of the wire, prolongs the service life of the dies, reduces the friction and the heat given off, and generally allows drawing to be carried out at high speed. Maintaining this contact pressure at optimal values also in certain cases reduces the motive force used to turn the capstans.

The technique employed to drive the successive capstans in a multi-stage drawing bench initially involved using a single motor with a positive drive which transmitted the motion to the successive capstans via speed reducers of differing characteristics which turned the capstans at progressively higher speeds in the forward direction of the wire. This technique, which suffered from many difficulties, because the chemical and physical properties of the starting material can differ, so that it elongates the wire to a different extent between one die and the next, leading to the use of always excessive speeds, and also because of problems to do with using a single motor, has given way to more recent techniques in which each capstan is driven by a separate electric motor via a positive drive using gears or sprockets and a belt, with the correct increasing transmission ratio. In other cases the capstans, each still supported by its own spindle, are connected by this spindle to an electric motor by a coupling joint. Means are provided to detect the current draw of the various electric motors and regulate their performance according to preset programs controlled by an electronic processor, so that the wire proceeds from die to die with optimum contact pressure between the wire and the capstans and therefore with optimum pulling force. This technique is technologically reliable but is expensive because of the presence of the spindles of the capstans, the coupling joint or the drive transmission, which among other things is noisy and requires periodic maintenance.

It is an object of the invention to obviate these limits of the prior art by means of the solution set out in the appended Claim 1 ) and succeeding dependent claims, which is based on the following idea concept. The capstan, of any type, is mounted directly on the shaft of an electric torque or similar motor, making use of the internal bearings of the rotor of this motor which for this purpose are suitably designed and this motor is flanged with the stator on the rear wall of the shoulder, the front face of which defines the chamber occupied by the lubricating and cooling liquid, in which the capstans and dies operate. First sealing means are provided in the hole in said shoulder through which the motor shaft rotatably passes and which partly houses one of the sets of bearings of the motor, upstream of which bearings, and therefore towards said first sealing means, are second sealing means provided outwardly with a gasket designed to be pneumatically pressurizable in such a way as to prevent the infiltration of liquid towards said bearing set. The electric motor has a forced liquid cooling circuit for the stator, while its rotor, which is hollow, is designed for the circulation of a continuous flow of ambient or cooled air. Mounted on the non-capstan end of the motor shaft is an encoder which supplies the speed and phase signals. If necessary, the same end of the motor shaft which is connected to the encoder may be connected to a rotating distributor which allows the cooling liquid to be circulated through the capstan, especially through the last capstan which works dry and is outside of said chamber. The flange closing the rear of the motor has leaktight penetrations for the electrical power cables, for the encoder cable and for the cables of the internal motor temperature sensors, and all the cables are connected to a supply and control board which operates the motor in such a way that the wire advances with a capstan contact pressure and traction which are within a predetermined optimal range of values for the type of wire being drawn. Together with the two sets of bearings, one upstream and one downstream of the rotor, which provide the rotating support for the motor shaft, there is also at least one one-way wheel which prevents rotation of the motor shaft if such rotation is due to the wire pulling elastically on the capstan, as for example if the electrically driven capstan is stopped, in such a way that the assembly can be restarted completely safely without dangerous slippage between the wire and the capstan and without the risk of the wire coming off the sheave, which can happen in the prior art. It will be obvious that the novel solution eliminates all the problems which in the prior art are caused by the mechanical motion drives which are usually located between the electric motor and the capstan. It will also be obvious how it greatly simplifies the entire mechanical and kinematic part in that the capstan is mounted directly on the shaft of the electric motor which drives it.

Other features of the invention, and the advantages procured thereby, will be made clearer by the following description of a preferred embodiment thereof, illustrated purely by way of non-restrictive example in the figures of the two appended sheets of drawings, in which:

Figure 1 shows an electrically driven capstan partly sectioned on a vertical plane containing the axis of rotation of the assembly;

Figure 2 shows the axial part of the same electrically driven capstan of a drawing machine which works dry on the wire and requires means for cooling the interior of the capstan.

In the figure, reference 1 denotes the shoulder of the supporting structure, the right- hand surface of which defines a wall of the chamber V containing the capstans C and the dies, which may operate immersed or in some other known condition such as sprayed or dry. The wall has horizontal through holes 2 carrying the shaft 103 of a torque or other type of electric motor 3 whose characteristics are suitable for the present use, and whose front stator flange 203 is mounted on the rear face of the shoulder 1 , by a plurality of screws (not shown) suitably distributed around the circumference. This mounting solution is preferred to that which could involve for this purpose the stator 503 because the latter component becomes very hot and could cause problems with thermal dilation, even though these problems are minimized by the presence of the aforementioned cooling means. Nonetheless, it will be understood that any other suitable method of attaching the motor 3 directly or indirectly to the shoulder 1 is within the scope of the invention.

A capstan C, which may be of any suitable type and not necessarily of the same type as the two-groove capstan illustrated by way of example in the drawing, is mounted in any suitable way, replaceably, on the section of the shaft 103 which projects into the chamber V. Before the capstan is mounted on the motor shaft 103, a cover 4 with gaskets 5 is placed on this shaft and the cover is fixed in a sealed manner in a seat provided on the front of the shoulder 1 , coaxially with the hole 2, as indicated by the seal 105 and screws 6. The purpose here is to provide a first barrier against the ingress of liquid towards the motor 3 through the hole 2.

A bush 7, which may be integral with, or preferably, as in the present example, attached to, the front flange 203 of the housing of the motor 3, has at least one flange 107 for attachment by means of screws. It also has at least one seal 8 on the outside diameter, in which it houses at least one bearing 9 of any type, not necessarily the bearing illustrated with two races of rollers. This bearing 9 has high resistance to both radial and axial loads and provides rotational support to the motor shaft 103. The same bush 7 contains, upstream of the bearing 9, and inside a supporting flange 10, a gasket 11 , while downstream of the same bearing 9, in a flange 12, is a double barrier of sealing means 13, 13', between which air is supplied at suitable pressures so that in the event of failure of the seals 5 and ingress of liquid towards the motor, the liquid cannot enter said bearing 9. The seals 13, 13' are pressurized via ducts 114 inside the bush 7 and through ducts 14 inside the stator flange 203. The ducts have an inlet port 15 for connection to a source of filtered compressed air and have vent openings 16 suitably distributed around the circumference on the inside face of the flange 203, through which a continuous flow of air travels for the internal cooling of both the hollow rotor 303 and the air gap of the motor. This air then passes out through openings 17 suitably distributed around the outermost part of the stator rear flange 403 of the motor 3. It should be understood that the port 15 mentioned above may alternatively open into a chamber (not shown) formed within the shoulder 1 and connected to said compressed air source via dedicated ducts, obviating the need to connect supply ducts physically to said port 15.

Another variant may relate to the fact that the ducts 16 for cooling the motor 3 may be connected to an air supply line independent of the line supplying the ducts 114, so that the latter can be monitored by a pressure sensor and/or other suitable means for remotely detecting anomalies in the seals 13, 13'.

The motor rotor 303 can be mounted on the shaft 103 by any suitable means, not necessarily as shown at 18 in the drawing. Because torque motors generate large amounts of heat, their stator 503 includes an internal labyrinth seal 19 through which the cooling liquid is passed and which for this purpose is provided with end attachments 119, 219 for connection to the cooling liquid pumping means (not shown).

Both of the stator flanges 203 and 403 are mounted on the stator 503 via sealing means 20, 20'.

A bush 21 may be formed integrally with the rear flange 403, especially in the case of low-power motors, or be made as a separate component screwed to it by means of its own flange 121 , as in the present example. This bush 21 has a gasket 221 on its outside diameter and, by means of at least one bearing 22, supports rotationally the rear end of the shaft 103 of the motor 3 while on the inner end face of this bush a flange 23 is fixed with a gasket 123 to hold in the lubricant of this bearing. On the outer end face of the bush 21 is a seat into which there projects a tapering end section of the shaft 103 of the motor, onto which the internal bush of a freewheel or one-way wheel 24 (see later) is mounted, with its external bush fixed in said seat and held in the latter by a cover 26 with a removable cap 126. Housed inside this is an encoder 27 whose moving part is fixed by suitable means 28 to the shaft 103. A gasket 30 prevents the lubricant of the bearings 22, 25 and of the freewheel 24 from leaking out or leaking towards the encoder.

On the rear flange 403 of the motor 3 stator are a suitable number of cable penetrations 31 for the electrical power supply to the motor 3, an optional cable penetration 32 for the cable of the encoder 27, if this cable penetration is not provided on the cover 26, and cable penetrations 33 are provided for the cables connected to the internal sensors (indicated diagrammatically at 133) of the temperature of the motor 3 stator. Said cables are all connected to a supply and control panel (not shown) which has a processor which, depending on the power consumption of the motor and the data relating to its speed of rotation calculated from the encoder 27 signals, ensures that the motor operates with torque and speed values which are maintained within parameters written into software executed by said processor.

Said freewheel 24 is such as to prevent the motor shaft 103 from rotating due to the elastic drawing action of the wire on the capstan C, whenever the motor is temporarily stopped, so that when restarted the wire interacts correctly with the capstan, preventing the wire becoming slack and possibly coming off the sheave, as can occur in the prior art.

Figure 2 illustrates an alternative form of the electrically driven capstan which is particularly suitable for the last capstan, positioned outside of the chamber V of the drawing machine, which requires cooling because it is not immersed in the liquid during operation. This alternative uses an encoder located on the side of the rear end of the shaft 103 of the motor, which passes through the cover 26 and projects from it for connection to the moving part of a rotating collector 34 fixed with the stator and by means of a bracket 37 to any part of the rear flange 403 of the stator of the motor 3, and provided with attachments 134 and 234 for the entrance and exit of the cooling liquid which passes along pipes and ducts 35 arranged axially inside the shaft 103 to arrive at and leave from an internal pipe 36 provided in a suitable way in the housing, which may be composite, of the capstan, in such a way as to carry away from this component the heat generated in it by its contact with the wire being drawn.

It should be understood that the description has referred to a preferred embodiment of the invention, omitting the constructional details of the torque motor 3 as these are within the scope of any person skilled in the art once given the diameters of the capstans and the pulling force which these must exert on the wire in order to draw it.

Claims

1 ) Electric capstan for drawing machines or for other machines for processing metal or nonmetal rod, wire or strip, said capstan (C) being characterized in that it is mounted directly on the shaft (103) of an electric torque motor or similar motor (3), of suitable characteristics, with internal support bearings (9, 22) suitable for the purpose, with a stator (203, 503, 403) mounted on the rear face of a vertical support shoulder (1 ), on the front face of which said capstan is located, this shoulder having a hole (2) for the passage of said shaft (103) which passes through at least one cover (4) with sealing means (5, 105), which closes said hole (2) to protect the motor (3), for example to prevent the cooling and lubricating liquid surrounding the capstans and dies from leaking through towards the motor.

2) Capstan according to Claim 1 ), characterized in that said electric motor (3) is mounted on said supporting shoulder (1 ) by means of attachments suitably distributed around its front flange (203), which contains channels (14) provided externally with at least one port (15) for connection to a source supplying filtered air at ambient or cooled temperature, and provided with one or more vent openings (16) on the inner end face of said flange (203), to provide a continuous flow of cooling air through the hollow rotor (303) of the motor, holes (17) being provided on the rear flange (403) of said motor, in the appropriate positions and suitably distributed, to vent the air after it has removed heat from the internal parts of the motor, the stator (503) of which is provided with its own line (19, 119, 219) for the forced circulation of a cooling liquid.

3) Capstan according to claim 1 ), characterized in that the front flange (203) of the electric motor (3) has, either as an integral part or attached to it, a projecting axial bush (7) which partly engages with said hole (2) and which houses at least one bearing (9) with characteristics of high resistance to both radial and axial loads, which is protected at the motor end by a flange (10) with a seal (11 ) and at the capstan end by a flange (12) with a pair of seals (13, 13') between which air pressure is maintained at suitable values, the air being bled from the line (14) supplying air for internal cooling of the rotor of the motor (3).

4) Capstan according to claim 1 ), characterized in that the rear flange (403) of the motor (3) has, either formed integrally with it or attached axially to it, a bush (21 ) which by means of at least one bearing (22) rotatably supports the rear section of the shaft (103) of said motor (3), a flange (23) being fixed to the inner end face of this bush, with a gasket (123), while the outer end face of said bush (21 ) has a seat into which there projects a tapering end section of the shaft (103) of the motor, mounted on which section is the inner bush of a freewheel (24) while its outer bush is fixed in said seat and is held in it by a cover (26) containing an encoder (27) whose moving part is mounted on said shaft (103); sealing means (30) being provided to prevent leakage, towards the encoder, of the lubricant of the bearings (22, 25) and of the freewheel (24) which prevents rotation of the motor shaft if such rotation is due to the wire pulling on the capstan, as for example if the electrically driven capstan is stopped, in such a way that the assembly can be restarted completely safely without dangerous slippage between the wire and the capstan and without the risk of the wire coming off the sheave.

5) Capstan according to claim 1 ), characterized in that if said capstan operates outside of the chamber (V) of the drawing machine and requires cooling, use is made of an encoder (27) located on the side of the rear end of the shaft (103) of the motor so that said rear end can pass through said cover (26) and can project from it for connection to the moving part of a rotating collector (34) fixed with the stator to any part of the rear flange (403) of the stator of the motor (3) and provided with attachments (134, 234) for the entrance and exit of the cooling liquid which passes along pipes and ducts (35) arranged axially inside said shaft (103) to arrive at and leave from an internal pipe (36) provided in a suitable way in the housing, which may be composite, of the capstan, in such a way as to carry away from this component the heat generated in it by its contact with the wire being drawn.

6) Capstan according to claim 1 ), characterized in that a suitable number of cable penetrations (31 ) are provided on the rear flange (403) of the stator of the motor (3) for the three-phase supply of said motor, an optional cable penetration (32) is provided for the cable of the encoder (27), and cable penetrations (33) are provided for the cables connected to the internal temperature sensors (133) of the stator of said motor (3).