ROTARY CONTROL DEVICE WITH RETRACTABLE KNOB, IN PARTICULAR FOR HOUSEHOLD APPLIANCES

Abstract: A rotary control knob with a first protruding work position and a second retracted rest position has no need that the support panel on which it is mounted, especially a dish-washing machine door, has a thickness such as re­ quired to allow housing a two-steps operated restraint device. The control knob is integral with an axially slidable control shaft, which does not rotate with respect to the rotating portion of the machine component to be controlled. The same shaft is connected at a point situated backward of the control knob, to the two-steps operated device which in a first embodiment is housed in a hollow part of the rotating portion of the machine component to be controlled and, according to a second embodiment, is linked to the rear end of the control shaft passing through the said component.

Description: The present invention deals with a rotatory control device having a control handle or knob movable from a work position in which it projects from a surrounding surface to a rest position, being retracted with respect to said surface. Such control devices are sometimes used in household appliances,such as for controlling cocks or switches of gas cookers or electric cookers, respectively, ovens and the like. Their purpose is that of providing an easy handling and working of the knob when this is in the projecting position, and its subsequent travel to the rest position, in which it does not project from the surrounding surface of the household apparatus, generally formed of a control panel, thus being protected from shocks and undesired strokes, and in addition the apparatus aspect is aesthetically improved. In these known control devices with retractable knob, the latter is mounted axially movable but not rotatable with respect to a shaft which is integral to the rotating portion of the component to be controlled, such as a cock or switch, and the knob includes a restraint device being operated two steps, which upon a first pressure on the knob allows its assuming the retracted position and keeps it there and upon a second pressure releases the knob and allows its reversed trip, under the action of a spring, to the protruding work position. However, the necessity of housing this device within the knob causes the latter to considerably extend itself in depth and requires a correspondingly deep seat to be completely housed under the external surface of the apparatus. Therefore the known devices cannot be adopted in those cases in which there is no sufficient available space in the depth direction. For example the known devices could not be used with the timer knob of a dishwashing machine, when it is mounted on the machine door and all the associated linkages, as well as the seat for the back stroke of the knob, must be contained in the restricted thickness available between the door and the inner screen-door of the machine. Additionally, the relatively short extension of the slide coupling between the knob and its shaft and the necessary clearance for a ready sliding cause the knob in the forward position to swing, thus giving the user the impression of an inadequate firmness or of a failure that has occurred. GB-A-2 088 639 intends to solve this problem by obtaining a push-push device of smooth and reliable operation without play, wherein said device is not housed in the knob, but in a box-shaped frame positioned at the rear of the component (a sound volume control mechanism). This solution however requires additional space behind the component, which often is not available. US-A-3 557 637 discloses a rotary control device according to the pre-characterizing part of claim 1. The aim of the present invention is to provide a rotary control device with a retractable knob, said device being of smaller dimensions than present known control devices. These types of control devices are sometimes used in household appliances and mounted in the frontwall thereof, where the available depth for such a control device is limited and therefore should be of small dimensions. The invention provides a control device where the restraint device operable in two steps to control the longitudinal movement of the control shaft is housed within a hollow central portion of the component to be controlled. With this construction the presence of the restraint device does not add to the depth size of the control device assembly, which is normally the case in known control devices, and the present invention consequently may have a particularly compact construction. Furthermore the shaft integral to the knob can be guided within the component to be controlled, or in relationship to parts integral therewith, much more efficiently than the way a slidable knob can be guided along its shaft, thus resulting in an improved stability of the knob in the "work" positions. Advantageously the control shaft, to the front end of which the control knob is fixedly mounted, is made integral in its back end portion to a piston-shaped member being axially slidable in the hollow central part of the rotating portion of the component to be controlled to which it is coupled for rotation movement by means of a key-type coupling, the piston--shaped member cooperating with a return spring biasing it to the position corresponding to the forward projecting knob and being formed with a shaped portion which is a part of the two-steps operated restraint device. Conveniently these configurations of the piston member, forming a part of the restraint device, comprise a recessed and shaped track co-operating with a coupling clip which is inserted in the rotating portion of the component to be cotrolled. In a typical and particularly advantageous application the control device of the invention is the actuation means for operating the programme timer of a household appliance such as a dishwasher, washing machine, cooker, oven or the like. The present invention will be better understood by means of the following description of a preferred embodiment, given by way of non-limiting example, relating to a control device for a dishwasher timer, and diagrammatically shown in the accompanying drawings, in which: FIGURE 1 shows in a side elevational view, partially in cross-section, a programme timer device for dishwashing machines, which is provided with a control device having a retractable knob according to the invention, the control knob being in the "work" position; FIGURE 2 shows the same parts of Fig. 1, but with the control knob in the rest back position; FIGURE 3 is a particular as viewed of the hollow central part of the timer rotating portion; FIGURE 4 shows a cross-section thereof; and FIGURE 5 shows a horizontal sectional view along a diameter thereof. With reference to the drawings numeral 1 represents a programme timer of a generally known type, but having a hollow central portion 2 which is integral to the rotating part of the component and formed of a multiplicity of cams, not shown. This hollow central portion 2 is provided with a key 3 extending longitudinally within its cavity. In addition the hollow portion 2 houses a coupling clip 4 with a bent free end 5. A piston-shaped member 6 is placed within the hollow portion 2 of the timer and shows a groove corresponding to the key 3 and co-operating therewith, so that the piston 6 can slide axially in the hollow portion 2 while rotates with the latter without relative motion. On the side opposite to the key 3 the piston 6 has a plane face with a shaped grooved track 7 adapted to co-operate with the bent free end 5 of the coupling clip 4 to form therewith a restraint device operable in two steps, which is well known per se. By means of this restraint device when the piston 6 is moved a first time toward the bottom of the hollow portion 2, it is kept in this position, whereas if it is brought a second time even more deeply to the bottom, it is released and can leave again the bottom. A return spring 8, partially inserted in a cavity of the piston 6 and resting against the bottom of the hollow portion 2, urges the piston 6 to move away from this bottom. A control shaft 9 projecting from the timer hollow portion 2 is fixed to the piston-shaped member 6 and a knob 10 is fixedly mounted at its outer end. The knob is placed in correspondence with a recess 12 formed in a surface 11, in this case a dishwasher door. The position of the knob 10 in relationship with the surface 11 is such that when the piston 6 is in its position far from the bottom of the hollow portion 2 (Fig. 1), the knob 10 protrudes from surface 11, whereas when the piston 6 is near the bottom of the hollow portion 2 (Fig. 2) the knob is within (in this case completely) the recess 12 which is the seat for its housing. The operation of the device is as follows. Supposing initially the rest position (Fig. 2), upon exerting a pressure on the knob 10 which is retracted in the seat 12, the restraint device to be operated in two steps is actuated to the effect that spring 8 is allowed to move piston 6 away from the bottom of the hollow portion 2: the knob 10 assumes the protruding position of Fig. 1. Then it can be grasped and caused to rotate in order to set the timer on the wished programme. The rotation of the knob 10 is rigidly transmitted to shaft 9 and piston 6 and from this to the rotating portion of the timer through the key 3. Upon setting, a further pressure on the knob 10 causes this to move back into the seat 12 while the restraint device operable in two steps holds the piston 6 in the vicinity of the hollow portion bottom. In this position the knob 10 does not protrude from the machine door surface 11, is protected from any accidental shock and cannot be inadvertently rotated such as by children. Furthermore in this not protruding condition it cooperates to a better aspect of the machine. However the knob 10 is still perfectly visible and its observation provides an indication of the progress of the pre-set working programme. The fitting between piston 6 and hollow portion 2 may be precise enough and the control shaft 9 in turn may be efficiently supported in that point where it projects from the hollow portion 2, so that any oscillation of the knob 10 in the "work" forward position can be efficiently prevented. Although the control device according to the invention has been described as applied to a dishwasher programme timer, it is obvious that such a device can be applied to timers for any different type of household apparatus, as well as to whichever else component to be rotatively controlled, and the knob of which can be advantageously retracted into a seat,provided that such a component allows for a hollow portion at the central zone of its rotating member or can be crossed throughout by an axially movable control shaft. The surface 11 may belong, instead of a door, to a control panel and the seat 12, which is entirely free in the represented embodiment, may be partially occupied by protruding elements adapted to be contained in the rear-side cavity 13 of the knob 10, between its mounting hub on the shaft 9 and its outer skirt, which in some cases may provide a further reduction of the dimensions required for the whole device in the depth direction. In any case the shape of the parts forming the device may be modified to conform to the various application requirements and the various components, especially the restraint device operable in two steps, may be replaced with their technical equivalents.

Claims: A rotary control device of the type provided with a control knob movable between a working position, protruding from the surrounding surface, and a rest position, retracted with respect to said surface, wherein the control knob (10) is fixed to a control shaft (9) mounted axially movable but not turnable to the rotating portion of a component (1) to be controlled, and said control shaft (9) is connected at a point behind the control knob (10) to a restraint device (4, 7) to be operated in two steps, which upon a first pressure impressed on said shaft (9) through the knob (10) provides for its movement to a position where the knob (10) is retracted from the surrounding surface (11), and upon a second pressure releases a return spring (8) urging the shaft to a position having the knob in the protruding working position, characterized in that the restraint device (4, 7) operable in two steps to control the shaft (9) is housed in a hollow central portion (2) of the rotating part of the component (1) to be controlled. A device according to claim 1, wherein the control shaft (9) at the outer end of which there is fixed said control knob (10), is connected at the inner rear end thereof to a piston-shaped member (6) axially slidable in said hollow central portion (2) and coupled thereto for rotation movement by means of a key-type coupling (3), said piston-shaped member (6) cooperating with said return spring (8) to urge said member to a position corresponding to the protruding knob (10), and being formed with a shaped portion (7) which is a part of said restraint device. A device according to claim 2, wherein said shaped portions (7) of the piston member (6), being a part of said restraint device operable in two steps, comprise a recessed and shaped track cooperating with a coupling clip (4) inserted in the rotating portion (2) of the component (1) to be controlled. A device according to claim 2, wherein said return spring (8) is partially housed in a cavity of the piston-shaped member (6). A device according to claim 1, being the actuating means to control a programme timer (1) of a household appliance such as a dishwasher, a washing machine, a cooker, an oven or the like.

Inventors: BERTAZZONI, ROBERTO
Applicants: SMEG S.P.A.
Application year: 1983
Main classification: H01H25
IPC codes: G05G1, H01H43, H01H25, H01H13