A device for constraining a wheel and tyre assembly on a platform

Abstract: A tyre changing machine (2) having a self-centring platform (1) with a vertical axis (x) is provided with a safety device (5) for releasably locking on the platform (1) a wheel (4) with a tyre. The device is particularly useful during tyre-inflating operations to prevent an operator from suffering injury due to an explosion of the tyre. The device comprises a stem (8) which is vertically slidable with respect to a horizontal arm (7). the stem (8) inferiorly bearing a plate (9) interacting contactingly with the wheel placed on the platform (1). A retaining organ (11) exhibits a hole in which a vertical rod (13) which is solidly constrained to the arm (7) is inserted with a predetermined degree of play. The retaining organ is hinged to the stem (8) in such a way as to be able to assume at least one locked position in which it prevents the stem (8) from rising.

Description: Specifically, though not exclusively, the device of the invention can be applied on machines for mounting and dismounting tyres on wheels, which machines have a self-centring platform, which is equipped with means for gripping and centring the wheel and which is rotatable about a normally vertical axis. In tyre changing machines there is always the prime need to protect the operator against any tyre explosion during the inflating operation, which is usually done with the tyre mounted on the platform. Without appropriate safety systems keeping the wheel in its position on the platform, any explosion would have disastrous effects. The wheel would be projected violently away from the platform, causing great risk to the operator and to anyone else who found themselves in the vicinity of the machine. Known safety systems comprise a horizontal arm, situated above the platform and rotatable on command about a vertical rotation axis, to which it is slidably coupled, with a vertical axis, a stem bearing at an extremity thereof a plate that can be positioned in contact with a wheel placed (centred and blocked) on the platform. Before inflating the tyre, the operator secures the wheel to the platform by positioning the rotatable arm on the platform and setting the plate above the central part of the wheel rim, thus exploiting the arm's ability to slide vertically. Then, using a locking device, generally cam-activated, he constrains the stem to the arm so that the wheel is solidly anchored on the platform so as to be constrained thereon even when subjected to very violent solicitation, as in the case of an explosion. In known devices, usually the stem is immobilized to the arm by means of a manually-actuable clamp mounted on the arm and comprising a rotatable cam-type control organ. This clamp, however, is not secure and reliable enough, especially as the cam is subject to wear which might, after many anchoring and unblocking operations, lead to a deterioration in blocking effectiveness. EP 0 767 098 discloses a burst protection device for tire removing machines of the type having a platform on which a wheel can be located and an arm supporting a bead extractor. The burst protection device comprises a wheel locking member for centering and fixing a wheel on the platform according to the preamble of claim 1, and a clearance signal-producing device which is actuatable upon fixing of the wheel on the platform through the locking member the signal-producing device controls operation of the machine in only an active intervention stage of the wheel locking member The main aim of the present invention is to obviate the above-mentioned drawback in the known art by providing an extremely safe and efficient device which remains so even after many work cycles. An advantage of the invention is that it provides a device which is extremely simple and rapid to use, requiring only a minimum effort on the part of the operator. A further advantage is that it is structurally and functionally configured so as not to require any direct action (for example, clamping) on the part of the operator in order to block the stem in any safety position. Other advantages offered by the present invention are the low costs involved in its construction, which makes use of simple mechanisms, and its functional reliability. These aims and advantages and others besides are all attained by the invention as it is characterised in the appended claims. Further characteristics and advantages of the present invention will better emerge from the detailed description that follows of a preferred but non-exclusive embodiment of the invention, illustrated purely by way of a non-limiting example in the accompanying figures of the drawings, in which: Figure 1 shows a schematic lateral vertical elevation of the device applied to a tyre changing machine; figure 2 shows a schematic plan view from above of the device; figure 3 shows a section made according to line III-III of figure 2, with the retaining organ represented in two different operative configurations. With reference to the above-mentioned figures of the drawings, 1 denotes in its entirety a self-centring platform, with a vertical rotation axis x, applied on a frame of a tyre changing machine 2 of known type. The self-centring platform 1 is equipped with the usual fasteners for constraining vehicle wheel rims thereto. The tyred rim 3 of a motor vehicle wheel 4 can be positioned, centred and constrained on the platform. A safety device 5 is associated to the platform 1 for constraining a wheel 4 placed thereon. The safety device 5 serves especially to prevent the wheel 4 from being unleashed violently away from the platform 1 following an explosion of the tyre during inflation thereof. The safety device 5 comprises an upright 6, vertically extending above the level of the self-centring platform 1, which might for example be one of the uprights normally present in the frame of the tyre-changing machine. A horizontal arm 7 is constrained to the upright 6, which arm 7 can perform a rotating movement about a vertical axis which is parallel and close to the axis of the upright 6, so that the arm 7 can be positioned along a horizontal plane situated above the self-centring platform 1. The arm 7 is constained to the upright 6 with a flag-type rotatable connection. A cylindrical stem 8 with a vertical sliding axis is slidably coupled to the arm 7. The arm 7 can assume a position in which the stem 8 is coaxial or nearly so with the platform 1. The lower end of the stem 8 exhibits a plate 9, usually circular but which could be any shape, destined to interact contactingly with the central part of the wheel rim 3 located on the platform 1. In the illustrated example the lower surface of the plate 9 exhibits a downwards-directed convexity; concave or flat plates could be used instead, however. The stem 8 can slide vertically in both directions with respect to the arm 7 (as indicated by arrows 10) and can be made solid to the arm 7 itself only in a case where the plate 9, placed at the lower end of the stem 8 and interacting contactingly with the wheel 4, is for any reason solicited to move upwards. When such a situation arises the stem 8 is made automatically solid to the arm 7 and the device 5 can prevent the wheel 4 from lifting from the platform 1, a situation which would in fact arise should a tyre explode. The stem 8 is freely slidable with respect to the arm 7 in a downwards direction. The means for immobilizing the stem 8 with respect to the arm 7 comprise a plate-shaped retaining organ 11, having a first hole 12 which, in the example illustrated is hexagonal, in which hole 12 a rod 13 solidly constrained to the arm 7 is inserted with a predetermined degree of play. The rod 13, which also exhibits a hexagonal straight section, extends in a parallel direction to the sliding axis of the stem 8, which in the illustrated example is vertical. The retaining organ 11 exhibits a first end which is constrained to the stem 8 and able to to assume a first and lower locking position A (indicated by an unbroken line in figure 3) in which it prevents the stem 8 from sliding uwards due to the contact between the rod 13 and the surface of the retaining organ 11 which surrounds the first hole 12. This position A is the characteristic locking position of a locking mechanism of the type achieved by what is commonly called a retaining lever. The retaining organ 11 is brought into locking position A thanks to its own weight. The retaining organ 11 can further assume, if lifted, at least one other position, an unlocking position or upper position B (shown in a broken line in figure 3), in which a free axial sliding of the stem 8 is allowed i.e. sliding of the stem in an upwards direction. A striker element 14, solidly constrained to the stem 8, is predisposed to limit the upwards rotations of the retaining organ 11 with respect to the stem 8. The striker element 14 serves in substance to prevent the retaining organ 11 from being tilted upwards to reach the locking position on the vertical rod 13 by a raising of the retaining organ 11 itself. The striker element 14, which in the illustrated case is constituted by a screw, is conformed and arranged so as to lock the retaining organ 11 in position B, i.e. the unlocked position. The position of the striker element 14 can be regulated by a simple screwing or unscrewing operation. In another embodiment, not illustrated, two striker elements could be provided, operatively associated with the retaining organ 11 and able to stop it in unlocked position B (horizontal or more or less so), which striker elements could be set side-by-side and spaced one from the other, and preferably arranged on opposite sides with respect to the vertical plane constituted by the axes of the stem 8 and the rod 13. The retaining organ 11 exhibits a second end, opposite to the first, which is associable to external movement means 1 with which the retaining organ 11 can be raised into the unlocking position B. In the illustrated case the retaining organ 11 is moved manually, the second end thereof exhibiting a grip 15. The retaining organ 11 exhibits a second hole 16, circular in shape, in which the stem 8 is inserted with ample play. In the embodiment illustrated, the retaining organ 11 is hinged to the stem 8 about a pivot 17, which is situated inside the second hole 16 and which is provided with a horizontal axis which is incident or nearly so with the axis of the stem 8. The retaining organ 11 might exhibit, in place of the second hole 16, a fork-shaped end. The retaining organ could be constrained to the stem 8 by means of different-type connections to the one illustrated in the accompanying figures, such as for example connections at present used for retaining lever mechanisms commonly in use. The safety device 5 is provided with an angular position sensor, of known type and not illustrated, for reading the angular position of the horizontal rotating arm 7, and which sends a consent signal to the tyre inflating means only when the stem 8 is substantially coaxial with the rotation axis x of the platform 1. The above-mentioned sensor has the task of guaranteeing that the inflation operation is carried out only when the safety device 5 has effectively locked the wheel 4 in position. As mentioned above, the safety device 5 is useful when a tyre of a wheel 4 placed on the platform 1 is to be inflated; otherwise the rotating arm 7 of the device 5 is normally positioned away from the platform 1 of the tyre-changing machine 2, so as not to get in the way during other operations which have be performed on the wheel. The safety device 5 is now described. Before inflating the tyre, the operator grips the second end of the retaining organ 11, pulling it upwards so as to bring the organ 11 into unlocked position B in which the stem 8 can be slid upwards. Then the operator rotates the arm 7 of the device 5, with the stem 8 raised, up until the stem 8 itself and the relative plate 9 are positioned above the central zone of the rim 3 of the wheel to be inflated. Then the operator lets go of the grip 15 and the retaining organ 11 falls into position A by virtue of its own weight. In this configuration, any upwards solicitation on the stem 8, due for example to an explosion of the tyre, would be contrasted by the vertical rod 13 on the arm 7, which rod 13 prevents clockwise movements (see figure 3) of the retaining organ 11. The safety device 5 in substance functions as a mechanism commonly known as a retaining lever. The unlocking of the device 5 is simply achieved by gripping the retaining organ 11 by the grip 15 and lifting it into unlocked position B.

Claims: A device for constraining a wheel (4) and tyre assembly on a platform (1), comprising: an upright (6), vertically extending above the platform (1); an arm (7), constrained to the upright (6) and able to make a rotation movement on to a horizontal plane situated above the platform (1); a stem (8) coupled slidingly to the arm (7) and having a vertical sliding axis, said arm (7) being able to assume a position in which the stem (8) is coaxial with the platform (1), a lower end of the stem (8) being destined to interact contactingly with the wheel (4); means for immobilizing the stem (8) in a releasable fixed position with respect to the arm (7), said fixed position being such that the lower end of the stem (8) interacts with the wheel (4), in order to prevent the wheel (4) from lifting from the platform (1); characterised in that said means for immobilizing comprise a retaining organ (11) provided with a first hole (12) in which a rod (13) is inserted with a predetermined degree of play, said rod (13) being solidly constrained to the arm (7) and being lengthwise arranged parallel to the sliding axis of the stem (8); said retaining organ (11) exhibiting a first end which is constrained to the stem (8) in such a way as to be able to assume at least a lower locked position (A), in which the retaining organ (11) prevents an upwards sliding of the stem (8), and an upper unlocked position (B), in which the stem (8) can move upwards; this being achieved through contact between the rod (13) and the surface of the retaining organ (11) which surrounds the first hole (12); said retaining organ (11) exhibiting a second end, opposite to the first end, which second end is associable to external movement means with which the retaining organ (11) is raised into the unlocked position (B). The device of claim I, characterised in that it comprises at least one striker element (14), solidly constrained to the stem (8) and predisposed to limit the upwards rotations of the retaining organ (11) with respect to the stem (8), conformed and arranged in such a way as to lock the retaining organ (11) in the unlocking position (B). The device of claim 2, characterised in that a position of the striker element (14) can be regulated. The device of any one of the preceding claims, characterised in that it is applied to a self-centring platform (1) having a vertical axis of a tyre changing machine (2). The device of any one of the preceding claims, characterised in that it comprises a sensor for reading an angular position of the arm (7) and for providing a consent signal to means for inflating the tyre only when the stem (8) is coaxial to the platform (1). The device of any one of the preceding claims, characterised in that the retaining organ (11) is hinged to the stem (8) and can rotate about a horizontal axis. The device of claim 6, characterised in that the rotation axis is incident to an axis of the stem (8). The device of any one of the preceding claims, characterised in that the retaining organ (11) can be manually raised by means of a grip (15) associated to the second end of the retaining organ (11). The device of any one of the preceding claims, characterised in that said arm (7) is rotatably constrained to the upright (6) through a flag-type connection. The device of any one of the preceding claims, characterised in that the stem (8) is freely slidable with respect to the arm (7) for downwards-directed movements.

Inventors: SPAGGIARI RINO, SPAGGIARI, RINO
Applicants: SNAP ON EQUIPMENT S R L, SNAP-ON EQUIPMENT S.R.L.
Application year: 1998
Main classification: B60C25
IPC codes: B60C25