Value .

The present invention is related to an adjustable control valve for flow regulation of gas or liquid, in particular for use for the control of the quantity of paint and air supply in spray painting.

Control of paint quantity and air supply for atomizing and jet formation with manual as well as robot controlled spray painting has up to now usually been performed by means of air pressure regulated mechanical controllers. Regarding the paint quantity control, these controllers have the disadvantage that they are substantially temperature and viscosity dependent and thus require cost and energy demanding regulation of the prevailing conditions in the spray boxes and paint flow circulation.

Another disadvantage of the present technical equipments is the difficult cleaning when the colour of the paint is to be changed.

Consequently, it is an object of the present invention to provide an adjustable control valve of the initially indicated type, in which the disadvantages indicated above are essentially overcome.

Thus, the inventions concerns an adjustable control valve for flow regulation of gas or liquid by compressing a hose at a site between two clamping members of a hose clamp device, thereby adjusting selectively the flow cross-section of the hose, one of said clamping members being operatively disposed in engagement with a movable cam disk, e.g. a rotatable eccentric sheave, operated by a shifting mechanism and mounted for actuating the clamp device to exert varying compression of said hose in accordance with the setting of the cam disk or eccentric sheave. On this background of prior art known in principle from GB-A-2.187.535 for a different field of application, the unique feature of the control valve according

to the invention is then that said one of the clamping members in engagement with the cam disk or eccentric sheave is disposed on a pivot arm, which is pivotably hinged on a pivot pin substantially spaced from said compression site.

When used for the supply of paint for spray painting, this technical solution has the advantage that no mechanical valve parts are in contact with the flow of liquid, and cleaning in connection with change of paint would then be simple and devoid of problems, and it is evident that this solution would have corresponding advantages in many other cases.

The engagement of the clamping member with the eccentric sheave is preferably effected through ^' a ball or roll bearing, and the shifting mechanism is preferably a step motor having the eccentric sheave mounted on the motor shaft, and may advantageously be arranged to be controlled from flow measuring means mounted for gauging the flow in the hose downstream of the compression site.

The cam disk or eccentric sheave has preferably a cam profile shaped to provide a linear relation between the shift position or rotational angle of the cam and the flow cross- section of the hose at the compression site, but alternatively a data processing unit may be inserted in the controlling connection between the flow measuring means and the shifting mechanism and programmed to provide linear relation between the shift position or rotational angle of the cam and the flow cross-section of the hose at the compression site.

The invention is also related to use of one or more adjustable control valves as indicated above, for the control of the supply of paint and/or air to an atomizing gun for spray painting, preferably for the purpose of controlling the quantity ratios between the supplies of paint, jet formation air and atomizing air, respectively, to the gun.

In practice such a quality ratio control is preferably

performed by means of a common data processing unit connected between control valve and said measuring means in all control loops for the supplies of paint, jet formation air and atomizing air, respectively, to the atomizing gun.

The invention is now to be explained in more detail by means of exemplified embodiments with reference to the accompanying drawings, whereon:

Fig. 1 shows schematically a control valve according to the invention in a side view, and

Fig. 2 shows in principle a circuit diagram for use of the control valve according to the invention in installations for the supply of paint, atomizing air and jet formation air in controlled mutual quantity ratios to an atomizing gun.

In Fig. 1 it is shown a favourable embodiment of the present invention, in which a hose clamping device KI, K2 is mounted on a supporting plate B for controlled clamping of a hose A, through which flows a gas or liquid, at a compression site As. The hose clamp device comprises two cylindrical clamping members on respective sides of the hose at the compression site. One of the clamping members KI is then disposed on a pivot arm R, which is pivotably hinged on a pivot pin T spaced from the compression site As, whereas the other clamping member K2 is stationary mounted on the bottom side of the hose directly opposite the above mentioned, pivotably movable clamping member KI. This clamping member KI is in engagement with an eccentric sheave E via a ball bearing LI, which is mounted in the interior of the clamping member KI and extends outside towards the eccentric sheave through an opening on the top side of the clamping member. In this way friction inhibited and hose wearing sliding motion between the clamping member and the hose is avoided, as well as between the clamping member and eccentric sheave.

The eccentric sheave E is mounted on the shaft of a step motor (not shown) serving as a shift mechanism for the setting of the

eccentric sheave E in various angular positions with respect to the top clamping member KI. In accordance with the rotational angular setting the external cam profile of the eccentric sheave would then move the clamping member KI through the ball bearing to a greater or smaller extent in a direction towards the lower clamping member K2, the clamping member KI by means of the pivot arm R being pivoted about its pivot pin T, which in turn is supported in a ball or roll bearing L2.

By means of the setting mechanism, which in the present case is constituted by a step motor, and the cam profile of the eccentric sheave the distance between the clamping members KI, K2 at the compression site As of the hose may be selectively varied in accordance with the rotational position of the eccentric sheave. In this manner the flow cross-section of the hose may be adjusted to the desired value for flow regulation of the gas or liquid which passes through the hose A. The flow regulation may then in practice be performed automatically in closed loop by controlling the step motor from a measuring device mounted for gauging the liquid or gas flow in the hose downstream of the compression site As.

A practical embodiment of such a favourable regulation is illustrated in Fig. 2, where control valves according to the invention are shown included in equipment for controlled supply of paint, atomizing air and jet formation air to an atomizing gun for spray painting. Three control valves are then connected into individually associated supply channels Qa, Qp and Qf for the supply of atomizing air, spray paint and jet formation air, respectively, to the painting gun P. Downstream of the control valves a measuring element, Ma, Mp and Mf respectively, is included in each of the supply channels Qa, Qp and Qf respectively, for gauging the flow value of gas or liquid in the respective channels. The values gauged by the measuring elements are fed back as analogue adjusting signals to the individually associated shifting mechanisms of the respecitve control valves Sa, Sp and Sf. As shown in Fig. 2, all feedbacks of adjusting analogue signals take place through

a computer D, which is programmed for regulating the quantity ratios between the supplies of paint, jet formation air and atomizing air to the spray gun in accordance with the painting to be performed. The computer may in addition also be programmed for providing a linear relation between the angular position of the eccentric sheave and the flow cross-section of the hose at the compression site As. The last mentioned programmed control is, however, not necessary in the cases the eccentric sheave E has a calibrated cam profile which is empirically shaped to provide the desired linear relation between the angular position of the eccentric sheave and the flow cross-section of the hose at the compression site.