GB2124667A

GB2124667A - Band-wheel withdrawal device

Info

Publication number: GB2124667A
Application number: GB08224003A
Authority: GB
Inventors: Gerhard Seibert
Original assignee: Rosendahl Maschinen GmbH
Current assignee: Rosendahl Maschinen GmbH
Priority date: 1982-04-26
Filing date: 1982-08-20
Publication date: 1984-02-22
Also published as: FR2525648B1; SE8302321D0; FR2525648A1; DE3314441A1; DE3314441C2; SE456085B; FI831357L; GB2124667B; FI831357A0; FI78886C; SE8302321L; ATA162282A; AT372715B; FI78886B

Abstract

A band-wheel withdrawal device is disclosed in which the withdrawal wheel (2) is freely rotatable. The rope or cable to be withdrawn is gripped between two bands, an inner band (3) and an outer counter-pressure band (4), each of which is driven by its own drive wheel (5 and 5' respectively). Since both bands are driven, higher forces can be imparted to the rope or cable to be withdrawn. <IMAGE>

Description

SPECIFICATION Band-wheel withdrawal device The invention relates to a band-wheel withdrawal device, particularly for ropes, cables or the like. More particularly it relates to that type of withdrawal device which has an endless inner band which can be driven and which passes around at least part of the circumference of a withdrawal wheel and a rotating counter-pressure band which presses against the withdrawal wheel over a portion of the periphery, is withdrawn tangentially from this and is guided by guide means.

In such known devices, the inner band is driven by means of the withdrawal wheel and the counterpressure band is guided over freely rotatable guide pulleys and is entrained by frictional connection with the inner band wrapped over the withdrawal wheel or the rope, cable or the like to be withdrawn and which is held between the inner band and the counter-pressure band. The inner band serves as a casing for the driven withdrawal wheel while the counter-pressure band pressed against it merely increases the friction between inner band and withdrawn material.

The disadvantage of these known devices lie in the fact that only the friction between inner band and rope is used for the often very high tensile forces which are necessary for braking or withdrawal, and the counter-pressure or outer band therefore has to be tensioned to a correspondingly great extent. The cable or rope is stressed thereby with a correspondingly great contact pressure. Since sufficiently strong materials suitable for use as an outer band are not available, the withdrawal forces of the known band withdrawal devices are generally limited to 30,000 to 40,000 N, while in the case of larger withdrawal forces, devices with very large withdrawal wheels, of diameter in the region of 3,000 to 4,000 mm, are needed. The drive torque necessary for the withdrawal wheel is also accordingly great.Because of the high frictional forces to be transmitted by the inner band, this is exposed to rapid wear. In addition, it has been found that the contact pressures which can be used in known devices, in many cases, for example during passage of damp or greasy ropes where the friction quotient between inner band and rope is very low, are not sufficient to reach the necessary tensile forces so that difficulties and interruptions in operation result. Afurther increase of the tensile force is not possible, however, because of the limited loading capacity of the outer counterpressure band.

It is an object of the invention to provide a band wheel withdrawal device which permits the achievement of higher withdrawal forces while retaining the usual band materials.

According to the present invention there is provided a band-wheel withdrawal device for ropes or cables, the device comprising a freely rotatable withdrawal wheel, an endless inner band which at least partially encircles the withdrawal wheel, a counter-pressure endless band which also encircles the withdrawal wheel over a portion of the periphery thereof, drive means for the inner band, and drive means for the counter-pressure band.

Preferably, the inner band and the counter press ure band are so driven that they travel around the withdrawal wheel in the same direction and at substantially the same angular velocity.

In this manner, the effect is achieved that both bands exert tensile forces on the rope, cable or the like to be withdrawn and so the application of the necessary frictional force is distributed over the two bands. As a result, it is possible, with a loading of the outer band which substantially corresponds to that in conventional band-wheel withdrawal devices, to be able to transmit forces which are twice as high than is possible with comparable conventional bandwheel withdrawal devices.

As a result of driving the inner band through a separate small guide wheel, it is possible to impart sufficient tensile forces without special expenditure and with relatively small drive units working in a range of comparatively low torques.

The two bands are preferably driven with a difference in speed depending on the particular diameter of the material to be withdrawn. For example, a mechanical differential gear between a drive motor and two drive wheels is suitable for this.

Alternatively, the drive of the two bands is effected by means of two motors both of which deliver substantially the same power and one of which, preferably the motor driving the inner band, is regulated in its speed.

In this case, the effect is achieved that the second motor is always adjusted in its speed to the value determined by the geometrical conditions which are influenced by the diameter of the rope, cable or the like to be withdrawn, while the power supplied by each motor corresponds to half the power necessary for applying the required tensile force at a required withdrawal speed.

An embodiment of the invention will now be more particularly described by way of example and with reference to the accompanying drawing, which shows a band-wheel withdrawal device embodying the invention, of the type which is generally used, for example in cable production lines.

Referring now to the drawing, a withdrawal wheel 2 is journalled for free rotation in a stand 1. The withdrawal wheel 2 is partially encircled by an inner band 3 which is guided in an encircling groove in the withdrawal wheel 2. The inner endless band 3 is further guided over a drive wheel 5 and a tensioning wheel 6 which is held adjustably in the stand 1. The drive wheel 5 can be driven by means of a motor 15 via a gear 16.

An outer counter-pressure band 4 is guided over a portion of the periphery of the withdrawal wheel 2, in its groove, and presses against the inner band 3.

The counter-pressure endless band 4 is so guided over a guide pulley 7 and a second drive wheel 5' that it is withdrawn tangentially from the withdrawal wheel 2. On its return path the counter-pressure band 4 passes over two tensioning wheels 6' held adjustably in the stand 1.

The second drive wheel 5' is driven by a separate motor 17 via a gear 18.

The two motors 15 and 17 each deliver the same power, this power corresponding to about half the power necessary to achieve the required withdrawal force at the required withdrawal speed. One of the two motors 15, 17 is regulated in its speed whereas the second motor adapts its speed to that of the other.

If a rope or cable is introduced between the inner band 3 and the counter-pressure band 4, it becomes entrained as a result of the pressure between the bands and the frictional connection between each of the bands 3 and 4 of the rope or cable. Thereby it can be withdrawn from a preceding device, for example a stranding device. Both bands 3 and 4 contribute to this and each band transmits about half the tensile force to the rope or cable to be withdrawn. This is possible because both bands 3 and 4 are separately driven and there is a frictional connection between each band and the rope or cable to be withdrawn because of the contact pressure of the counter-pressure band 4. This is an improvement over known devices with only the withdrawl wheel driven, whereby the entire tensile force has to be applied by the one frictional connection between inner band and rope.

Claims

1. A band-wheel withdrawal device for ropes or cables, the device comprising a freely rotatable withdrawal wheel, an endless inner band which at least partially encircles the withdrawal wheel, a counter-pressure endless band which also encircles the withdrawal wheel over a portion of the periphery thereof, drive means for the inner band, and drive means for the counter-pressure band.

2. A band-wheel withdrawal device as claimed in claim 1, wherein the drive means for each of the two bands comprises a respective motor, each motor delivering substantially identical power and one motor being regulated in its speed.

3. A band-wheel withdrawal device as claimed in claim 2, wherein the motor regulated in its speed is the motor driving the inner band.

4. A band-wheel withdrawal device as claimed in claim 1, wherein the drive means for both bands comprises a single motor and a differential gear which can be driven thereby.

5. A band-wheel withdrawal device as claimed in any one of the preceding claims, wherein the inner band and the counter-pressure band are so driven that they travel around the withdrawal wheel in the same direction and at substantially the same angular velocity.

6. A band-wheel withdrawal device substantially as described herein with reference to the accompanying drawing.