GB1561354A

GB1561354A - Device for the centering of an endless belt for a machine for the drying of hides or the like

Info

Publication number: GB1561354A
Application number: GB3223776A
Authority: GB
Original assignee: Luigi Rizzi and Co SpA
Current assignee: Luigi Rizzi and Co SpA
Priority date: 1975-09-03
Filing date: 1976-08-03
Publication date: 1980-02-20
Also published as: FR2322927B1; FR2322927A1; DE2635435A1; CS200191B2; DE2635435C2

Description

(54) DEVICE FOR THE CENTERING OF AN ENDLESS BELT FOR A MACHINE FOR THE DRYING OF HIDES OR THE LIKE (71) We, S.p.A. LUIGI RIZZI & C., of 88 Via M. Fanti, Modena, Italy, an Italian Joint-Stock Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a device to be applied to machines having one or more continuous belts in a closed ring, tensioned between return pulleys and tension pulleys, with said belts being, for example, of felt, for machines or continuous presses for drying hides or the like, or for belts of any type for conveyors or the like; said device providing automatic and continuous centering of the belt during the working movement thereof.

The technical problem of centering a continuous belt in movement becomes particularly complicated in machines or presses for drying hides and the like, since the endless belt is formed by felt of great thickness or easily deformable material and has a width normally greater than one metre.

During the operation of the drying machine, the two felts forming the rings are strongly pressed against each other including between them the soaked hide to be squeezed for drying. Under these operating conditions the strip of felt is continuously urged in an axial direction by forces resulting from variations of thickness and the conditions of the hide or the like.

The device according to the present invention when applied to the tension pulley of the continuous belt in machines of the said type, resolves the said technical problem by proceeding to effect automatic centering of the belt whilst said belt is in working motion. As is known in such machines, the belt in a closed ring of felt or the like, is tensioned between a return pulley and a tension pulley, the latter being initially manually tensioned by screw means or the like until the desired tension is achieved and so as to cause the axis of the tension pulley to assume a position parallel to that of the return pulley.

According to the present invention, there is provided a device for the adjustment centering on an endless belt for a machine for the drying of hides or the like, in which the belt is disposed between at least one return pulley and one tension pulley, characterised in that the means for positioning and tensioning the belt applied to the tension pulley are rotatably, but not axially displaceably associated with a double acting hydraulic unit disposed on one or both sides of the belt so as to be movable with the piston of the unit; the movement of each piston being controlled by a sensor disposed on each side of the belt and actuable by the deviation thereof and an electric valve and means for feeding fluid under pressure so that, during centering, movement of said piston in a required direction takes place in the hydraulic unit which is on the same side as the deviation of the belt and in a direction to incline the tension pulley outwardly relatively to the return pulley and thereby produce a convergence between the two pulleys adapted to urge the belt itself laterally.

When the belt, during operation and after initial centering, tends to become displaced on one of the sides and exceeds the admitted deviation, the belt presses on the sensor located on the same side, thus actuating the electric valve so as to feed fluid under pressure to the cylinder which is located on the side of the deviation so as to obtain greater traction and outwardly displacing the end of the tension pulley.

In this position, the two pulley axes (of the tension pulley and of the return pulley), become convergent with the apex on the side opposed to that of the deviation of the belt with the result that the belt itself tends to become displaced towards the said opposed side until it reaches the centered position again. The sensor is therefore left and both the axes become parallel again.

It has, however, become apparent that when the pulley which is inclined is not the driving one, and for not very rigid belts, such as those used in drying machines or presses which are formed by felts of appreciable thickness and extensible, the converging movement of the axis of the tension pulley did not lead to rapid resumption of the central position of the belt after the deviation.

This is due to the fact that the said incline of the tension pulley produces, along the angle of contact of the belt, an axial component tending to bring the belt into one direction for the first quarter of a turn and in the opposite direction for the other quarter of a turn. However, in view of the fact that the type of belt under consideration has considerable flexibility or suppleness under tension, as well as poor adhesion to or contact with the tension pulley, despite the use of devices to increase it, and in view of the fact that the difference in tension between the two lengths of the belt is not important, both the axial components which are developed by the effect of wear in the first and in the second portion of the arc of contact are not very different - with a slight prevalence of the component directed in the opposite direction to that of the deviation.It follows that the belt tends to resume the centre position very slowly, wearing itself out along the edges by contact with rollers or guides for containing it.

According to a preferred embodiment of the present invention it is proposed that the movement of the axis of the tension pulley on which the belt is wound is effected in a plane perpendicular to the plane containing the two axes in the starting position by the displacement of only one end of the said pulley upwardly or downwardly according to the deviation assumed by the belt.

The lowering or raising of one end of the pulley relative to the original plane of the two axes, produces in the deviated belt an axial component directed oppositely to that of deviation, which is developed over the entire arc of contact and therefore much more effective than the difference between the said two opposing components which are produced by a displacement outwardly and co-planar with the end of the axis towards which the deviation has occurred.

According to the modification, by lowering only one end of the axis of the tension pulley, the belt which starts from the driving pulley comes into contact with the tension pulley with each line according to the warp, i.e. parallel to the long side of the belt at a specific point of each generatrix of the pulley and whilst the same point travels over the semi-circle of contact with the pulley, executes a trajectory which is displaced in one direction or the other relatively to the starting projectory according to whether the end of the pulley has been lowered or raised and in relation to the direction of rotation.In fact, the other end of the tension pulley remaining in the starting position, causes each point of the generatrices to travel over an arc of a circle upwardly or downwardly when the opposite end is raised or lowered; said arc of a circle becoming diposed in a plane perpendicular to the plane containing the axes of the two rollers when they are in the parallel and centre position.

It follows that the axial component, due to the incline, acts on the belt over the entire angle of contact of the belt with the pulley itself.

It is also possible, for special cases, to combine the two movements so that one end of the tension pulley can be displaced in the same plane containing the axes and also in a plane perpendicular thereto.

The device according to the modification comprises said screw means to place the belt initially under tension and being associated with a swinging frame pivoted on an axix lying in the plane containing the axis of the two pulleys when they are in an initial position intermediate thereto; said frame or the like being raised or lowered at the other end by means of hydraulic means similar to those already described and operating under the control of lateral sensors sensitive to the deviations of the belt.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a schematic illustration of a device applied to a tension pulley with a belt in the normal position tensioned between said pulley and the return pulley; Fig. 2 shows the device of Fig. 1 actuated by the sensor following left-hand deviation; Fig. 3 shows the same device operating following deviation of the belt in the righthand direction; Fig. 4 is a schematic side view of a belt tensioned between pulleys and with a modified embodiment of the device for the displacement of one end of the pulley in the lowered position; and Fig. 5 is a schematic front view of the device with the return pulley of Fig. 4 with a greatly increased displacement.

A continuous belt machine is shown schematically in Fig. 1 and has a centering device according to the invention applied thereto and includes a return pulley 1 and a tension drum or pulley 2 between which there is diposed a continuous belt 3 made of, for example, felt or the like. The tension pulley 2 is supported by a shaft 4 on the ends of which are disposed nuts 5 and 6 in which respective threaded spindles 7, 8, are screwed and also connected to the handwheels 7a, 8a. Each threaded spindle 7, 8, is associated with a piston rod 9, 10, respectively, so as to rotate but not to be axially displaced; the said rod being axially locked between the associated handwheel 7a, 8a and a ring 7b, 8b. Each piston 9, 10, is contained within a cylinder 11, 12, respectively.

The cylinder 11 is connected to the opening 11a adjacent the tension pulley 2 and by means of the pipe or tube 13 connected to the opening 12b in a side of the cylinder 12 remote from the tension pulley 2. The cylinder 12, however, is connected to the opening 12a adjacent the tension pulley 2 and by means of the pipe or tube 14 connected to the opening 1 lib in a side of the cylinder 11 remote from the pulley 2. The tubes 13 and 14 are connected by way of ducts 15, 16, to an electric valve, generally indicated by 17, in turn connected to an exhaust tank 18 and to a pressure source 19, the fluid of which arrives in the direction of the arrow P.The said electric valve 17 is of the type in three sections, a central section 17a communicating with the exhaust, an end section 17b having two opposed and parallel passages, and the other end section 1 7c having two intersecting passages. The electric valve is controlled by two solenoids S1 and S2 of which S1 puts the section 17b in circuit and the S2 puts the section 17c into circuit. Disposed at the sides of the continuous belt are two sensors of known type, indicated by M1 on the lefthand side and M2 on the right-hand side; and having contact levers which may be spaced from the edges of the belt 3 by the amount of tolerated deviation. The sensor M1 controls the solenoid S1 and the sensor M2 controls the solenoid S2.

The mode of operation is as follows: In Fig. 1 it is assumed that the belt 3 is located in the centre whereby the axes of the tension pulley and the return pulley are parallel. The tension on the belt 3 is initially provided by operating the handwheels 7a, 8a, so that the respective screws 7 and 8 act on the ends of the shaft 4 to tension the belt 3. The pistons 9 and 10 are disposed at the end of their travel towards the belt as may be seen schematically in Fig. 1. In this position neither of the two solenoids S1 and S2 is energised and therefore the valve 17 is dis posed with its centre section 17a connected on one side with the exhaust 18 and on the other with both the tubes 13 and 14 by way of the ducts 15 and 16 whereby the cylinders 11 and 12 are connected to the exhaust 18. The opening of the duct of supply pressure P is closed.

Fig. 2 shows the situation when the belt 3 is displaced to the left-hand side to a position where it is in contact with the sensor M1 whereupon the said sensor M1 energises the solenoid S1 which in turn actuates the elec tric valve 17 which centres the section 17b so as to cause the pressurised fluid to be fed by way of the tube 15 to the tube 13 - tube 14 leading to the exhaust. It follows that the cylinder 11 which receives pressure from the opening 1 1a, urges the piston 9 outwardly (arrow A) and the latter displaces the lefthand end of the tension pulley 2 in the same direction thereby inclining the axis of the shaft 4.At the same time the cylinder 12, which receives pressure from the opening 12b, urges the piston 10 inwardly and the latter displace the right-hand end of the tension pulley 2 in the opposite direction of the left-hand end. In this manner convergence of the two pulleys is produced with the apex on the right-hand side and associated displacement of the belt 3 in the same direction so as to cause such to leave the sensor M1 and thereby to cause the solenoid S1 to be deenergised, the section 17a of the electric valve returning to the centre position and connecting both the cylinders 11, 12, to the exhaust 18 as shown m Fig. 1.

Fig. 3 shows the situation resulting from a displacement of the belt 3 to the right-hand side. In this position the sensor M2 which energises the solenoid S2 is shown activating the section 17c of the electric valve. The pressure fluid in the direction P thus passes by way of the tubes 16 and 14 to the openings 1 lib of the cylinder 11 and 1 2a of the cylinder 12, displacing respectively the piston inwardly and the piston 10 outwardly in the direction of the arrow B with the tube 13, 15, leading to exhaust. The axis of the pulley 2 is also inclined in direction of arrow B thus producing a convergence towards the left with the axis of the roller 1 and hence displacement of the belt 3 to the left until the initial conditions are resumed.

With reference to the embodiment shown in Figs. 4 and 5, the driving pulley 1 and the return pulley 2 between which belt 3 is tensioned, are shown in side and front views and the same reference numbers are used in respect of similar parts.

The tension pulley 2 is supported by shaft 4 on the ends of which are disposed the nuts 5, 6, and in which threaded spindles 7 and 8 respectively are screwed and connected to the handwheels 7a, 8a. By means of these handwheels and the respective screws, the continuous belt 3 is tensioned between the said two pulleys 1 and 2 as described above.

One of the nuts for controlling the shaft 4, for example the nut 5, is mounted on a slide block or the like member 20 sliding in a frame 21 which is pivotally mounted on a pivot 22 parallel to the axis 1 and lying in the plane containing the two pulleys 1, 2, with the belt centered. The frame 21 is also supported or connected to a piston 23 which is slidable in a cylinder 24 and the tubes 13 and 14 communicate therewith and carry the pressurised fluid controlled by the sensors M1 and M2 as already described.

If the belt 3 is displaced to the left, it actuates the sensor M1 and the already described device feeds fluid under pressure to the tube 13, lowering the free end of the frame 21 and hence the left-hand end of the tension roller 2, rotating around the other end of the said pulley. Conversely, if the belt 3 is displaced to the right, it actuates the sensor M2, which in turn controls the supply of fluid to the tube 14 to cause raising of the piston 23 and hence the frame 21 with the end of the pulley 2.

Fig. 5 shows on a greatly enlarged scale the pulley 2 in a downwardly displaced position effected by the piston 23 to cause lowering of the free end of the swinging frame 21 following a control command of the sensor M1 due to a displacement of the belt 3 to the lefthand side into contact with said sensor.

As may be seen from Fig. 5 because of rotation in the direction of arrow C, the side edges of the belt 3 leave the driving pulley 1 at the points 25 and 26 and reach the tension pulley 2 at the points 27 and 28 and are urged by forces perpendicular to the axis of the pulley 1, that is, in the direction of the arrow F1.

Upon contact with the tension pulley 2, the various points of the belt 3 would tend to follow the straight trajectory already travelled along the free portion formed between the two rollers but, due to the contact of the belt with the surface of the pulley 2, the pulley tends to cause the belt itself to travel along an arc of contact, a trajectory inclined relatively to the preceding one and directed in the direction of the arrow F2 perpendicular to the axis of the pulley 2 which is now inclined.

Each point of the belt 3 is urged simultaneously by the said two forces F1 and F2, it has to follow a movement according to the component F3 of the said two forces, thus engaging each point of the belt 3 after it has touched the pulley 2. The presence of the force F3 is then apparent in the direction of the axis of the pulley 2 and tends to displace the belt to the right-hand side, i.e. in a direction against that of the deviation. This compound F3 is developed over the entire arc of contact constituted, for example, by a semicircle in the case of pulleys 1 and 2 of the same diameter.

According to the variant, the action tending to displace the belt in a direction opposite to that of deviation, meets no opposition and is developed with rapidity even under normal conditions of contact between the continuous belt and the tension roller.

According to the invention it is possible to make one, or other end of the tension rollers alternatively displaceable in a vertical direction or to combine the two movements of one end or of both - not only in the plane containing the axes, but also in a plane substantially perpendicular thereto.

It will be understood that numerous modifications of a constructional nature may be applied to the above arrangements particularly with regard to the mechanisms and/or the means of traction and adjustment, without thereby departing from the scope of the present invention.

WHAT WE CLAIM IS: 1. A device for the adjustment or centering of an endless belt for a machine for the drying of hides or the like, in which the belt is disposed between at least one return pulley and one tension pulley, characterised in that the means for positioning and tensioning the belt applied to the tension pulley are rotatably, but not axially displaceably associated with a double acting hydraulic unit disposed on one or both sides of the belt so as to be movable with the piston of the unit; the movement of each piston being controlled by a sensor disposed on each side of the belt and actuable by the deviation thereof and an electric valve and means for feeding fluid under pressure so that, during centering, movement of said piston in a required direction takes place in the hydraulic unit which is on the same side as the deviation of the belt and in a direction to incline the tension pulley outwardly relatively to the return pulley and thereby produce a convergence between the two pulleys adapted to urge the belt itself laterally.

2. A device as claimed in claim 1 in which the sensors disposed at the sides of the belt actuate the said electric valve by way of the solenoids thereof the solenoid valve being adjustable for connecting the hydraulic unit selectively to the pressure fluid source in response to the actuation of a respective one sensors and the solenoid valve connecting the hydraulic unit to the exhaust when the belt is centred and neither one of the sensors is actuated; the central resting position of said electric valve being such as to connect both the hydraulic units with the exhaust.

3. A device as claimed in claim 1 or 2, in which the initial positioning means of the belt are formed by threaded spindles axially locked within the rod of said pistons and controlled externally by handwheels or the like; said threaded spindles being associated with nuts connected to the ends of the support shaft of said tension pulley.

4. A device as claimed in claim 1, in which means are provided to effect the movement of one or both ends of the tension pulley substantially in a plane perpendicular to the plane containing the axes of both pulleys when they are located in the initial starting position with the belt centred.

5. A device as claimed in claim 4 in which the said movement means comprise a swinging frame on which a slide block or the like member slides and is associated with the tensioning means; said frame being inclinable in

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. If the belt 3 is displaced to the left, it actuates the sensor M1 and the already described device feeds fluid under pressure to the tube 13, lowering the free end of the frame 21 and hence the left-hand end of the tension roller 2, rotating around the other end of the said pulley. Conversely, if the belt 3 is displaced to the right, it actuates the sensor M2, which in turn controls the supply of fluid to the tube 14 to cause raising of the piston 23 and hence the frame 21 with the end of the pulley 2. Fig. 5 shows on a greatly enlarged scale the pulley 2 in a downwardly displaced position effected by the piston 23 to cause lowering of the free end of the swinging frame 21 following a control command of the sensor M1 due to a displacement of the belt 3 to the lefthand side into contact with said sensor. As may be seen from Fig. 5 because of rotation in the direction of arrow C, the side edges of the belt 3 leave the driving pulley 1 at the points 25 and 26 and reach the tension pulley 2 at the points 27 and 28 and are urged by forces perpendicular to the axis of the pulley 1, that is, in the direction of the arrow F1. Upon contact with the tension pulley 2, the various points of the belt 3 would tend to follow the straight trajectory already travelled along the free portion formed between the two rollers but, due to the contact of the belt with the surface of the pulley 2, the pulley tends to cause the belt itself to travel along an arc of contact, a trajectory inclined relatively to the preceding one and directed in the direction of the arrow F2 perpendicular to the axis of the pulley 2 which is now inclined. Each point of the belt 3 is urged simultaneously by the said two forces F1 and F2, it has to follow a movement according to the component F3 of the said two forces, thus engaging each point of the belt 3 after it has touched the pulley 2. The presence of the force F3 is then apparent in the direction of the axis of the pulley 2 and tends to displace the belt to the right-hand side, i.e. in a direction against that of the deviation. This compound F3 is developed over the entire arc of contact constituted, for example, by a semicircle in the case of pulleys 1 and 2 of the same diameter. According to the variant, the action tending to displace the belt in a direction opposite to that of deviation, meets no opposition and is developed with rapidity even under normal conditions of contact between the continuous belt and the tension roller. According to the invention it is possible to make one, or other end of the tension rollers alternatively displaceable in a vertical direction or to combine the two movements of one end or of both - not only in the plane containing the axes, but also in a plane substantially perpendicular thereto. It will be understood that numerous modifications of a constructional nature may be applied to the above arrangements particularly with regard to the mechanisms and/or the means of traction and adjustment, without thereby departing from the scope of the present invention. WHAT WE CLAIM IS:

1. A device for the adjustment or centering of an endless belt for a machine for the drying of hides or the like, in which the belt is disposed between at least one return pulley and one tension pulley, characterised in that the means for positioning and tensioning the belt applied to the tension pulley are rotatably, but not axially displaceably associated with a double acting hydraulic unit disposed on one or both sides of the belt so as to be movable with the piston of the unit; the movement of each piston being controlled by a sensor disposed on each side of the belt and actuable by the deviation thereof and an electric valve and means for feeding fluid under pressure so that, during centering, movement of said piston in a required direction takes place in the hydraulic unit which is on the same side as the deviation of the belt and in a direction to incline the tension pulley outwardly relatively to the return pulley and thereby produce a convergence between the two pulleys adapted to urge the belt itself laterally.

both directions by means of a piston and cylinder fluid unit under the control of sensors and by the said hydraulic or the like means.

6. A device as claimed in claims 4 and 5 in which the said means for moving in the plane perpendicular to the starting plane may be applied to both ends of the tension or return pulley and actuated alternately.

7. A device according to claims 4 to 6, in which the said means for moving one or both ends of the tension pulley in the plane per pendicular to the plane containing the axes of the two pulleys, may be combined with the said means for moving the same tension pulley in the plane containing the axes of the said two pulleys.

8. A device for centering an endless belt constructed and arranged to operate substantially as herein described with reference to and as illustrated in the accompanying drawing. ~