TECHNICAL FIELD

The present teaching relates to a tyre testing device which checks the uniformity and/or geometric properties of manufactured tyres, and in particular to a method of clamping tyres tested in an inflated condition.

BACKGROUND

Testing devices for testing tyres in the inflated condition are designed in structural manner so that the tested tyre is mounted between a pair of detachable rims, where the tyre is inflated to a specified pressure and bring out into rotation. Various types of such devices are used in practice to test uniformity, geometry and balance of tyres.

When testing uniformity, a tyre tread is pressed against a load wheel that substitutes a road surface, and variation of forces acting between the tyre and the load wheel is measured by load sensors. When testing geometric properties, contactless measurement of a shape variation of a rotating tyre is performed. When testing the balance, dynamic effects of a rotating tyre caused by its unbalance are measured.

In the known and used solutions of the testing devices, a complete spindle of a machine consists of a fixed part that provides a drive for tyre rotation and a movable part that forms a necessary gap between the rims for accommodating the tested tyre. A rotational axis of the spindle is usually vertical. Depending on the type of a design of the testing device, the upper or lower spindle may be fixed. The free spindle, in addition to the rotational movement, allows movement of the respective rim in the manner parallel to the rotational axis, which is utilised for clamping or releasing the tested tyre.

Advanced testing devices also include a mechanism for automatic adjustment of a rim width, i.e., a distance between the detachable rims after clamping the tyre. The mechanism increases efficiency of the device, since it enables testing tyres of different design widths in succession, whereby the necessary adjustment of the rim position is carried out automatically.

It is a specific task to clamp tyres with collapsed sidewalls, the inflation of which is problematic due to leakage of the inflation air through a gap between the rim and the sidewall. The reason of the collapsed sidewall is primarily the effect of gravitational forces acting on a horizontally positioned non-inflated tyre. The phenomenon is more common for tyres having a higher sidewall and manufactured from softer compounds.

There are known solutions for a tyre clamping system capable of supporting inflation of tyres having narrow or collapsed sidewalls, so that the tyre is sealed and inflated at a smaller rim width, and afterwards the rim is opened to a specified width. A challenge in the process is to design a rim opening under the effect of forces of the inflated tyre.

Document U.S. Pat. No. 4,852,398A describes a machine for testing tyre uniformity and having a fixed spindle holding an upper rim and a vertically positioning lower rim. The machine comprises a conveyor belt, by means of which the tested tyre is transported above the lower rim. The lower rim together with the tyre are lifted by a hydraulic mechanism and connected concentrically to the upper spindle by means of a centring cone. Consequently, the tyre is inflated, spun and a measurement is performed under the action of a load wheel. The lifting of the lower rim and its lowering after completion of the measurement is performed by means of a hydraulic cylinder. The cylinder has to be capable to generate sufficient force to overcome the extension forces acting on the rims from the inflated tyre. The cylinder force has to be also sufficiently large for holding the centring cone to provide for the alignment of the rims and simultaneously to create necessary friction to transmit torque from the driven upper spindle onto the lower one. Adjustment of a rim width is provided by positioning the lower rim to a defined height using the hydraulic servo mechanism. Consequently, the centring cone is movable with respect to the lower rim in the direction of the rotational axis and the necessary force action is provided by a spring.

The described system having hydraulic positioning also allows, in principle, a support for inflation of tyres having collapsed sidewalls; its disadvantage, however, is the necessity of using hydraulic energy. It means, for the users, increased machine noise sourcing from the hydraulic power unit, a risk of environmental pollution, demanding maintenance as well as a danger due to high pressures.

There are known testing devices that, when clamping tyres, do not use hydraulic energy for mutual fixation of the positions of both rims/spindle parts, but they use mechanical locks. Such device is disclosed, for example, in document U.S. Pat. No. 5,257,561A, describing a clamping mechanism, which enables mechanical locking of the rims for different tyre widths. The solution, however, does not allow approximation of the rims when inflating the tyres having the collapsed sidewall. The solution for inflation of deformed tyres for such clamping mechanisms is disclosed in document US20110203362A1, but the described method is less effective than approximation of the rims, and it causes increased load on the conveyor in the machine.

Another possibility of the rim width adjustment is the use of a helix for axial displacement of the rim on the fixed part of the spindle—an example is cited in document U.S. Pat. No. 5,107,702A. The rim is connected slidably to a nut, which, after locking its rotational movement with respect to the machine frame, moves axially along a helix machined on the spindle surface, when the fixed spindle is rotated. In these devices, the adjustment of the rim width is usually carried out in the no-load condition before locking the spindle and inflating the tyre, which again does not support inflation of the tyres with collapsed sidewalls.

The principle of the rim width adjustment according to document U.S. Pat. No. 5,107,702A is also used in machines having mechanical clamping and having support for inflation of deformed tyres. In this case, the rotational movement of the nut for the rim width adjustment is blocked by a controlled brake. The tyre is clamped at a reduced rim width, it is inflated, and then, with the nut being braked, the rim width is adjusted to a specified value by means of rotation of the spindle. However, due to the forces acting from the inflated tyre, high friction in the threads between the nut and the helix and simultaneously significant stress on the brake mechanism occur, which result in increased maintenance requirements and adversely affect machine reliability.

EP2244082A1 discloses automatic visual inspection equipment of a tire in which eccentricity of a rim-assembled fire due to deformation is prevented by preventing the tire from being burdened with the bad of an upper rim thereby preventing deformation of the tire due to the load of the upper rim. In the tire rim-assembling mechanism of the automatic visual inspection equipment of tire, an upper rim which is fixed to the upper surface of tire fixed horizontally onto a lower rim is previously pulled up to the side of a main shaft by means of an upper rim pull-up mechanism, which is fixed to the side of a main shaft.

SUMMARY

The subject of the present teaching includes a clamping mechanism for a tyre testing device enabling compensation of tyre sidewall collapse during testing, which comprises the following:A supporting bracket provided with a vertical guideA trolley fitted to the vertical guide provided with a first centring member,A vertically arranged spindle formed by a lower fixed spindle and an upper moveable spindle both arranged on one rotational axis A, whereBoth the lower fixed spindle and the upper moveable spindle are provided with rims facing each other, for clamping a tested tyre,The lower fixed spindle is adapted for rotational movement,The upper moveable spindle is positioned under the trolley and freely suspended in the supporting bracket in order to enable rotational movement as well as the movement in the direction of a rotational axis A,The lower fixed spindle as well as the upper moveable spindle are provided with a bayonet lock for their mutual locking,The upper moveable spindle is provided with the second centring member adapted to latch into the first centring member of the trolley,The upper moveable spindle is further provided with a compensation chamber enabling insertion of the lower fixed spindle for compensation of a collapse of a tyre sidewall,A pneumatic cylinder for controlling movement of the trolley in the supporting bracket along the vertical guide in the direction of the rotational axis A for centring the upper moveable spindle with respect to the rotational axis A through the first and second centring members,A servo drive for controlling movement of the supporting bracket in the direction of the rotational axis A between an open position enabling insertion of the tested tyre between the rim of the upper moveable spindle and the rim of the lower fixed spindle, and the locked position, where the tested tyre is clamped between the rims.

According to a preferred embodiment the clamping mechanism may further comprise a support of the moveable spindle located between the upper moveable spindle and the supporting bracket in order to provide parallelism of the rims when clamping the tyre.

The subject matter of the present teaching also includes a method of clamping a tested tyre into a clamping mechanism according to the present teaching. The method comprises the following steps:Positioning of an upper moveable spindle by means of a supporting bracket into an open position,Insertion of a tested tyre onto a rim of a lower fixed spindle,Centring the upper moveable spindle with respect to a rotational axis A by a force exerted by a pneumatic cylinder in the direction of the rotational axis A on the upper moveable spindle by means of a trolley and first and second centring members,Positioning of the upper moveable spindle and the lower fixed spindle for locking of a bayonet lock using a compensation chamber,Exerting a force of the pneumatic cylinder on the upper moveable spindle until complete sealing of the tested tyre having a collapsed sidewall between rims,Inflation of the sealed tested tyre until the force of the tyre sidewall exceeds the force exerted by the pneumatic cylinder and a distance between the rims reaches a specified value for a specific type of the tested tyre, wherein clamping of the tested tyre is completed when contact surfaces of the bayonet lock lean against each other and the bayonet lock is locked, wherein tyre inflation pressure and the force exerted by the pneumatic cylinder are coordinated,Lifting of the trolley by means of the pneumatic cylinder and its detachment from the upper moveable spindle.

The clamping mechanism for the tyre testing device according to the present teaching enables compensation of the tyre sidewall collapse during testing, so that it is also possible to provide for inflation of deformed tyres. The present teaching does not need hydraulic energy and it enables adjustment of the sidewall collapse compensation to a large extent for individual tyre types according to a recipe. The process of the collapse compensation and mutual fixation of the fixed and movable parts of the spindle is coordinated in such a manner that there is no need to adjust the rim width after inflation of the tyre, thus reducing wear-out of the clamping mechanism.

The clamping mechanism according to the present teaching comprises the vertical spindle consisting of two mutually separable parts—the lower fixed spindle and the upper moveable spindle. Both spindles have an identical rotational axis and are provided with the rims facing each, between which the tested tyre is clamped. The bayonet lock having conical contact surfaces serves for mutual connection of the lower fixed spindle and the upper movable spindle during clamping.

The lower fixed spindle is firmly connected to a supporting frame of the device and performs only a rotational movement. The lower fixed spindle comprises a mechanism for adjusting the rim width for a particular tested tyre. The adjustment is performed automatically in unloaded state between measurements by means of changing the fixed spindle rim position along its axis. The rim width adjustment mechanism does not form part of the present teaching.

The upper movable spindle is enabled also to move in the direction of the rotational axis and comprises the compensation chamber for compensation of the sidewall collapse. The upper movable spindle assembly is fixed to the frame of the device through the supporting bracket by means of the vertical guide and is further connected to the servo drive. The supporting bracket with the vertical guide and with the servo drive form a positioning axis that enables changing the mutual vertical position of the supporting bracket and the lower fixed spindle. The supporting bracket may contain a support for the upper moveable spindle in order to provide for the parallelism of the rims when clamping the tyre.

The upper movable spindle assembly further comprises the trolley for compensation of the tyre sidewall collapse, where the trolley is connected to the supporting bracket by the vertical guide. There is the centring member on the trolley, preferably of a conical shape, which counterpart is part of the upper moveable spindle. A mutual position of the trolley and the supporting bracket is controlled by means of the pneumatic cylinder, preferably a double-action pneumatic cylinder.

In order to clamp the tyre having the collapsed sidewall, the bracket of the upper moveable spindle assembly is positioned by means of the servo drive to such height so that sufficient space between individual spindles is made in order to accommodate the tested tyre. The pneumatic cylinder is pressurized in the extended state, while the upper movable spindle is leaning against the support to provide for parallelism of the rims and at the same time centred with respect to the lower fixed spindle by the action of force of the first and second centring members.

After loading the tested tyre into the machine by means of a conveyor, the conveyor is lowered thus placing the tyre on the rim of the lower fixed spindle. Consequently, the supporting bracket of the upper moveable spindle is positioned so that the teeth of the bayonet lock of the lower fixed spindle engage between the teeth of the bayonet lock in the upper moveable spindle into the compensation chamber until the desired reduced rim width for sealing the collapsed sidewall is reached. After rotating the bayonet lock of the lower fixed spindle into the locking position the sealed tyre is inflated. When the action of force of the tyre sidewall during inflation overcomes the force of the pneumatic cylinder, the upper moveable spindle starts shifting and the rims are opening. The movement is axially guided, because the pneumatic cylinder maintains the effect of the first and second centring members by the applied force, and simultaneously it is damped, since at the same time said force regulates the opening speed of the rims. For this purpose, the tyre inflation and the magnitude of the force of the pneumatic cylinder are coordinated by means of the pressure regulation in the pneumatic cylinder. The tyre clamping is completed when the contact surfaces of the bayonet lock lean against each other, at which moment the specified rim width for the specific tyre test is reached.

Subsequently, the pneumatic cylinder is retracted, thereby separating the trolley from the upper moveable spindle (detaching the first and second centring members from each other). Thereby the locked spindle with the clamped tyre stops touching the elements of the upper moveable spindle assembly and is ready for rotation and measurement execution.

