US3533574A - Tensioning device - Google Patents

Description

Oct. 13, 1970 BN1. COOPER ETAL 3,533,574

TENSIONING DEVICE Filed March 25, 1968 3 Sheets-Sheet 1 III FIG.2

Oct. 13, 1970 B, J, COOPER ETAL 3,533,574

TENS IONING DEVI GE 3 Sheets-Sheet 2 Filed March 25, 1968 FIG.3

Oct. 13, 1970 COOPER ETAL 3,533,574

TENSIONING DEVICE Filed March 25, 1968 3 Sheets-Sheet 5 /l/ l I -FIG.4

nited States atent Qfice 3,533,574 Patented Oct. 13, 1970 US. Cl. 242-450 3 Claims ABSTRACT OF THE DISCLOSURE A tensioning device for yarns, threads, wires cables, etc., is operated by fluid pressure and controlled by a feedback arrangement responsive to changes in back pressure in an open nozzle induced by the thread tension.

This invention relates to tensioning devices.

The term tensioning device is to be understood to mean a device for imparting tension to a thread and for maintaining a predetermined tension in the thread. The term thread is used herein for convenience, but it is to be taken to include any flexible elongate member consisting of one or more threads of textile and fibrous material, whether natural or synthetic; metallic threads or wires, and so on; and includes twisted threads, metallic and partly-metallic cables, insulated wires and cables, spun and unspun fibres and yarns, and the like.

According to the invention, a tensioning device includes fluid-pressure operated variable tensioning means ar ranged to impart tension to a thread, and feedback means responsive to changes in the output tension in the thread for varying the fluid pressure so as to adjust the tensioning means in a manner tending to cancel said changes.

According to a preferred feature of the invention, said feedback means include a nozzle arranged to be supplied with pressurized fluid, resilient means arranged for resilient movement resiliently in response to changes in the output tension, the resilient means being in front of the nozzle so that said movement changes the back pressure at the nozzle, and the nozzle being connected to the tensioning means so that changes in said back pressure can be transmitted to the tensioning means whereby to adjust the tensioning means in said manner.

There may be provided between the nozzle and the tensioning means a fluidic amplifier arranged to control the input pressure to the tensioning means in response to said back pressure.

Said resilient means may for example be a leaf spring or diaphragm.

Tensioning devices according to the invention are applicable, in various appropriate forms, to such apparatus as (for example) spinning machinery, machinery for making synthetic textile fibres, coil-winding machinery, wire-winding machinery, rope-making apparatus (whether for wire or fibre ropes), cable-making machinery for electrical and other cables including heavy wire cables and hawsers, submarine cable laying apparatus, and apparatus for winding prestressing wires into position during the building of a prestressed concrete structure or fabrication of prestressed concrete components.

In adapting devices according to the invention for use with threads of such widely-differing sizes and mechanical properties, the tensioning means, and the means by which the feedback means is made responsive to the output tension, will be designed so as to suit the particular thread to be tensioned.

According to a preferred feature of the invention in one aspect, the tensioning means includes first threadengaging means moveable with a resilient fluid-pressure sensitive member towards and away from second threadengaging means arranged so that the thread is pinched between said first and second thread-engaging means.

The pressure-sensitive member is preferably a bellows.

Tensioning means of this kind are more suitable for small threads such as textiles (e.g. wool) and thin wires, having a fairly high degree of flexibility.

According to a preferred feature of the invention in another aspect, the tensioning means include a capstan drum, arranged for the thread to pass therearound, and a fluid-pressure operated brake coupled to the capstan drum.

Tensioning means of this kind are suitable for heavy threads such as prestressing cables, wire ropes and large electric cables, though they can readily be adapted for smaller threads as well.

The larger the thread to be tensioned, the greater will be the tension required, as a general rule. Thus tensioning devices according to the invention, where they are designed for use with the larger types of thread such as prestressing cables, etc., may require substantial fluid pressures to operate the tensioning means. The size of the components of the feedback equipment can be kept to a minimum by the use of a fluidic amplifier as mentioned above: where a very large amplification is required, for supplying relatively high pressures to the tensioning means, the amplifier may be in several stages. A cascade or series of separate fluidic amplifiers, giving progressively greater amplification, is to be taken as included within the scope of the term fluidic amplifier.

Various devices according to the invention will now be described by way of example and with reference to the accompanying drawings, of which:

FIG. 1 is a diagrammatic view showing such a device in one form;

FIG. 2 is a diagrammatic view showing a modified form of the device;

FIG. 3 is a diagrammatic view showing another form of the device;

FIG. 4 is a sectional view taken on the line IV-IV of FIG. 5, showing an alternative form of tensioner to that used in the devices shown in FIGS. 1 and 2;

FIG. 5 is a sectional view taken on the line VV of FIG. 4; and

FIG. 6 is a sectional view showing a modification of the tensioner shown in FIGS. 4 and 5.

With reference to FIG. 10, a woolen thread 10, passes in the direction indicated by the adjacent arrow through a tensioner 11 including two successive fixed bars 12 spaced apart in the direction of motion of the thread (which passes over them and is in contact with them). vA third bar 13 is situated between the bars 12 and engages the opposite side of the thread. The bar 13 is mounted in the tensioner 11 by means of a bellows 14. Expansion of the bellows 14 kinks the thread so as to increase its tension, and contraction of the bellows decreases the tension.

Expansion andcontraction of the bellows 14 is controlled by a pressurised fluid supplied from a source (not shown) through an orifice 15 and a pipe 16 communicating with the interior of the bellows.

Beyond the tensioner 11, the thread 10 passes through a loop 17 supported from the free end of a cantilevered leaf spring 18. The spring 18 serves as a tension-sensing device, in that it is deflected by any increase in the tension of the thread 10. A nozzle 19 is arranged adjacent the spring 18, in a position in which it is closed, or most nearly closed by the spring 18 when the output tension in the thread 10 (i.e. the tension after passing through the bars 12 and 13) is zero. The nozzle 19 is supplied with pressurised fluid through the same orifice 15 as in the bellows 14.

In operation, the output tension in the thread is preset to a predetermined value by setting the fiuid pressure at a corresponding value. This may be done either at its source, or for example by varying the size of the orifice 15, which may be made adjustable for this purpose.

If the output tension is increased for any reason (such as an increase in the diameter of the thread 10 as it passes through the tensioner 11), or an increase in input tension of the thread, the spring 18 is deflected away from the nozzle 19 by a corresponding amount, so reducing the back pressure in the nozzle. Since this back pressure is also the pressure in the bellows 14, the bellows contract, so restoring the original output tension in the thread and enabling the spring 18 at the same time to move back to where it was. Thus the spring 18 and nozzle 19 together act as a negative feedback device, tending always to maintain the fluid pressure in the bellows 14 at a value corresponding to the required output tension in the thread.

The device shown in FIG. 2 is similar to that shown in FIG. 1, but it incorporates a fluidic proportional amplifier shown diagrammatically at 20. In this case the pipe 16 is connected to the output of the amplifier 20, the input of which is supplied with pressurized fluid from an input 21. The output pressure of fluid from the amplifier to the bellows is controlled by the pressure of fluid in a branch pipe 22 which is in direct communication with the nozzle 19. The output pressure may also be controlled by fluid pressure in a pipe 23, which is supplied from the same source as are the inlet 21 and nozzle 19. The pipe 23 incorporates a variable fluid resistor 24 to give fine control of the amplifier output pressure in the pipe 16.

The pressure in the pipes 22 and 23 may be substantially less than that at the inlet 21.

FIG. 3 shows a form of tensioning device especially suitable for use in connection with steel prestressing cables or other wires of substantial stiffness. In this case the wire, shown at 30, is passed around a capstan drum shown diagrammatically at 31, having a shaft 32 which is freely rotatable in bearings 33 on a fixed structure 34. The shaft 32 carries the disc 35 of a disc brake which is operated by the pressurized fluid in the pipe 16.

In place of the spring 18 shown in FIGS. 1 and 2, the loop 17 is suspended from a resilient diaphragm 3'6 mounted peripherally on the fixed structure 34 adjacent the nozzle 19.

An increase in pressure in the pipe 16 tends to apply the brake, while a decrease tends to release it.

In other respects the arrangement shown in FIG. 3 is generally similar to that in FIG. 2, movement of the diaphragm 36 in response to changes in output tension of the wire 30 producing a feedback effect which causes the brake to be operated in a manner such as to tend to cancel the change in output tension.

A pneumo-hydraulic or other valve may if necessary be incorporated in the pipe 16 in FIG. 3.

A drum brake may be used instead of a disc brake.

The diaphragm 36 may be substituted for the spring 18 in devices such as those shown in FIGS. 1 and 2; and in FIG. 3 the spring 18 may be used in place of the diaphragm. However, any other suitable device may be employed for varying the back pressure in the nozzle 19 in response to changes in output tension of the thread.

FIGS. 4 and show one form of tensioner 40 which may be substituted for the tensioner 11 in devices according to the invention for use with textile threads and threads of similar size.

The tensioner 40 includes two dished washers 41 and 42 which are freely rotatable about a fixed post 43. The lower washer 42 is constrained against axial movement. The bellows 44, connected with the pipe 16, bears on the upper washer -41. The thread passes between the washers and makes a partial turn around the post 43.

Variation in the fluid pressure within the bellows 44 4 varies the force applied to the thread by the washers 41 and 42, and thus varies the tension.

In the modified version of tensioner 60 shown in FIG. 6, a collapsible bag 61 is substituted for the bellows 44. The mode of operation of the tensioners 44 and 60 is otherwise the same.

Many other variations are possible on the arrangements described above: some of these will now be briefly mentioned by way of example.

In the tensioner 11 (FIGS. 1 and 2), the bars 12 and 13 may be notched to provide guides for the thread. They may be in the form of posts or pulleys, or any other device suitable for kinking the thread so as to apply a predetermined tension as described.

There may in some cases only need to be one bar 12.

The bellows in the tensioner 11 may be replaced by a bag such as the bag 61 (FIG. 6). Any other suitable expandable fluid-tight device may however be used in the tensioners 11, 40, 60.

The tensioner 11, 40 or 60, the spring 18 (or equivalent device) and nozzle 19 may all be incorporated together in a single unit, for example a compact plastics moulding. If a fluid amplifier is included, this may also be incorporated in the same unit.

The fluid used may be a liquid or a gas. Especially in the absence of means for preventing loss of gas to the atmosphere from the nozzle, or for collecting for re-use a liquid ejected from the nozzle, a very suitable fluid is compressed air. This may for example be supplied from a small auxiliary compressor driven by a main drive motor of the machine in which the tensioning device is incor porated.

The fiuidic amplifier may if desired be a multi-stage, instead of a single-stage amplifier.

Devices according to the invention may be adapted to control the tension of a number of threads simultaneously. For example the separate threads in a group of threads may each pass through a separate tensioner, and be associated with a separate spring 18 and nozzle 19, all the tensioners being controlled by fluid in a common feedback pipe, to which all the pipes 16 are connected, and which communicates with all the nozzles 19 so as to be responsive to the mean tension of the threads in the group.

It will be understood that the mode of operation of the control system may be inverted, that is to say the spring 18 or diaphragm 36- (or equivalent device) may be so arranged as to increase the back pressure at the nozzle 19 in response to an increase in output tension in the thread; the tensioner, or the brake ('FIG. 3), or equivalent device is then made to decrease the tension in response to increases in the back pressure. This may be done in the case of the tensioners 11, 40 and '60 by modifying the design of the tensioner so that expansion of the bellows 14 or 44 or bag 61 decreases the tension. In the case of a brake, this may be modified by arranging for the brake to be applied by a decrease in fluid pressure.

Alternatively, where a fluidic amplifier is incorporated it may be of the negative type, i.e. one in which an increase in the control pressure in pipe 22 produces a decrease in the output pressure in pipe 16.

We claim:

1. A tensioning device for interposition between material supply and receiving devices between which a flexible elongate material passes, comprising:

controllable retarding means engaging the material as it passes between the supply and receiving devices to apply a variable retarding force to the material, said means including an expansible resilient fluid receiver having a fluid inlet duct for admitting thereto fluid under pressure and a movable output part engaging the retarding means to vary the retarding force applied by the retarding means to the material in dependence upon the fluid pressure in the receiver,

a tension sensing device having a sensing member engaged by the material as it passes from the said retarding means towards the receiving device and a resilient biasing means biasing the sensing member to a bias position, the sensing member being deflected by the material from the bias position as the tension in the material increases,

a fluid supply conduit having a flow restrictor, downstream thereof a fluid escape nozzle disposed adjacent a part of the tension sensing device whereby movement of that part varies the rate of escape of fluid through the nozzle,

an outlet conduit located between the nozzle and the flow restrictor,

a fluid pressure amplifying device having: a control inlet duct connected with the said outlet conduit; a supply inlet duct for receiving fluid under constant pressure from a source of such fluid; an outlet duct connecting with the fluid inlet duct of the fluid receiver; the control inlet duct, the supply inlet duct and the outlet duct communicating with one another in the amplifying device so that the flow of fluid in the control inlet duct interacts with the flo-w of fluid from the supply inlet duct so as to vary the flow of fluid from the supply inlet duct to the outlet duct and hence to the fluid receiver.

2. A tensioning device according to claim 1, wherein the fluid pressure amplifying device has a second control inlet duct communicating with the other ducts in the amplifying device and being connected with an adjustable source of fluid under pressure for providing in the amplifying device a constant flow of fluid acting in opposition to that provided by the first-mentioned control inlet duct whereby to vary the pressure in the outlet duct in proportion to the difference in the fluid pressures in the two control inlet ducts.

3. A tensioning device according to claim 1, wherein the retarding means comprises a pair of washers having raised rims which face one another and which engage on opposite sides of the material passing to the receiving device,

the retarding means and the expansible fluid receiver being mounted adjacent one another between opposed spaced surfaces of a fixed frame member, the frame member having projecting from one of its surfaces a fixed pin on which the washers are freely carried for rotation, the expansible fluid receiver being positioned to press the washers together whereby to cause them to exert the retarding force on the material passing to the receiving device.

References Cited UNITED STATES PATENTS 2,098,422 11/1937 Keen et al 242156.2 2,343,181 2/1944 Heinz 24275.43 2,610,813 9/1952 Campbell 242 2,642,236 6/1953 Heizer 242 2,667,311 1/1954 Packer et a1 24275.43 2,714,494 8/1955 Wentz 242155 2,964,440 12/ 1960 Stevens 24275.43 X 3,072,360 1/1963 Cruz 242154 FOREIGN PATENTS 1,241,232- 8/1960 France.

STANLEY N. GILREATH, Primary Examiner U.S. Cl. X.R. 242-154, 155

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