IMPROVED SNAP SWITCH

The present invention relates to a snap switch in accordance with the introduction to the main claim. Snap switches have been known for some time; those utilized in the motorcycle field are used to enable activation of a particular motorcycle member. For example, a switch releases start-enabling when the usual clutch lever is pressed or the known motorcycle stand is at rest.

These switches can operate under normally closed conditions (in which the electrical contact on which such a switch acts must be closed at rest) or normally open (contact open with switch at rest).

Known switches are of very different construction one from another and are preferably and advantageously liquid-tight to prevent water, braking system liquid, petrol, antifreeze used for winter roads, etc. from entering their body, depending on the switch position on the vehicle,. However these known constructions often comprise a large number of components and are therefore difficult and lengthy to assemble, thus making them uneconomical and resulting in a high-cost article.

Other known solutions for achieving long life and/or improved liquid tightness, use high-cost materials for their construction, resulting in high production costs.

Finally, other solutions present operational uncertainties, poor precision or large dimensions, which prevent their reliable use or easy mounting, for example on a motorcycle handlebar.

An object of the present invention is to provide an improved snap switch, in particular suitable for use on a motorcycle or the like.

A particular object of the invention is to provide a snap switch of the stated type having a small number of components, resulting in simple construction and low production costs.

Another object is to provide a snap switch of the stated type which is liquid- tight.

A further object is to provide a snap switch of the stated type which has a high intervention rate, a long life and reliability in use. These and other objects which will be apparent to the expert of the art are attained by a switch in accordance with the accompanying claims. The present invention will be more apparent from the accompanying drawing, which is provided by way of on-limiting example and in which: Figure 1 is a longitudinal section through a switch of the invention in a first working position with contacts open;

Figure 2 is a view similar to that of Figure 1 , but which the switch in a second working position with contacts closed;

Figure 3 is an exploded view of the switch of the invention;

Figure 4 is a perspective view of an internal part of the switch of Figures 1 -3; Figure 5 is an exploded view of a variant of the switch of the invention; and Figure 6 is a longitudinal section through the switch of Figure 5. With reference to said figures, a snap switch comprises a body 1 presenting two hollow portions 2 and 3 fixed together in any known manner (for example by snap coupling via respective coupling members 2A and 3A, by screwing, by gluing or the like). The first portion 2 comprises movable members enabling the fixed contacts 5 associated with the second portion 3 to close; the two portions 2 and 3 are fixed together mutually sealed, i.e. such that no communication is possible between the interior of the portion 2 and the interior of the portion 3. The body 1 is fixed to a suitable support seat, for example a motorcycle handlebar.

Specifically, the portion 2 presents an inner cavity 10 open at two opposing ends 11 and 12, the end 12 being the free end of the body 2, while the end 11 is coupled to an upper part 13 of the second portion 3. From the open end 12

of the cavity 10, a first end 15 of a cylindrical part 16, hollow at 17, can emerge, this part presenting a second end 18 at which said cavity 17 opens (closed at the other end 19). The cavity 17 presents an internal step 20 on which a first end 21 of a variable diameter compression spring 22 (of progressive action) rests, its other end 23 resting on a flat part 25 of a circular membrane 42 resting on a flat end part 43 of a slider 26 movable within the cavity 29 of a hollow cylindrical piece or portion 30 inserted into the cavity 10 of the portion 2 and part of the second portion 3. This portion or piece extends upwards from the upper end 13 of this latter and contains the fixed contacts 5. The slider 26 comprises a pin 33 projecting perpendicularly from said flat part 43 and inserted into a shaped part 42A of the circular membrane 42 (acting as the seal element), to hence form a liquid seal when the switch is in a working position in which the cylindrical part 16 has its end 15 emerging from the end 12 of said cavity 10. This liquid seal is always ensured, even when the switch is in the other working position in which said end 15 projects limitedly (or not at all) from the end 12 of the cavity 10. This is because of the fact that the membrane 42 rests against the circular end of the hollow cylindrical piece 30. The slider 26 presents, on a side 44 thereof, three projections 46, 47 and 48 positioned in different planes. A first and a second projection (46 and 47), those closer to the flat part 43, cooperate with first and second parts 50 and 61 of a strip element 53 carrying at least one (movable) contact 54 (two in the figures under examination) arranged to cooperate with said fixed contacts 5. The strip element 53 is disposed along the side 44 of the slider 26 and longitudinally within the switch. It acts as a contact element to close an electrical circuit to which the fixed contacts 5 are connected or to enable this circuit to be opened. This strip or contact element is elastically deformable by virtue of its lamellar shape. Specifically, the strip or contact element 53 comprises a body 55 in which a first

hole 52 is defined and in which a second hole 56 is provided defined by the transverse part (transverse to the longitudinal axis of the strip element) 51 and by a third transverse part 58 carrying the movable contacts 54. An arched elastic web 61 (as described more precisely hereinafter), movable within the second hole 56 and having a free end 62 inserted into a cavity or groove 63 provided in the second projection 47 of the slider 26, projects from the transverse part 58. This insertion into the groove 63 results in elastic deformation of the web 61 (which is arched, as stated). This elastic deformation enables the strip element to assume a stable shape in only two positions. The two stable positions of the strip element enable the fixed contacts 5 to be closed (contacts 54 pressed on the fixed contacts 5) or to be opened (strip element in contact with the slider 26 in the region 44). Depending on the circuit connected to the fixed contacts 5, these positions correspond to different states of use of a user (not shown) connected to the switch of the invention.

The contact or strip element 53 presents an arched projecting portion 66 jutting from the second transverse part 51 and arranged to cooperate with a fixed abutment 67 on the hollow cylindrical piece 30, to hence deform the elastic web 61 , with consequent passage of the movable contacts 54 from a position in which they cooperate with the fixed contacts 5 and one in which they are separated therefrom (or vice versa). This is achieved via the movement of the third transverse part 58 of the strip element 53 relative to the projection 48 which determines only a sort of "protection" for the slider-strip assembly, preventing its disassembly. It should be noted that the first transverse part 50 of the contact or strip element 53 cooperates with a groove 70 provided in an upper side 71 of the first projection 46 of the slider 26 (Figure 3). It will be assumed that the snap switch 1 is mounted on a motorcycle handlebar

and that it cooperates with the clutch lever usually present on this latter such as to enable the vehicle to start only with the clutch lever pressed. The lever acts as an external actuator of the switch of the invention. It will also be assumed that the switch rest position is "normally closed" (Figure 2), this configuration pertaining when the clutch lever is pressed to enable engine start, to hence provide an enabling state (known per se) for vehicle start. To obtain passage from the first working position (in the example, with the contacts 5 closed) to the second working position (contacts 5 opened), the action of the lever on the end 15 of the part 16 causes this latter to move within the cavity 10 of the portion 2 towards the portion 3 against the spring 22. This spring, of variable diameter, acts by utilizing its "two rigidities", i.e. the different rigidities of its two parts 22A and 22B of different diameter: it firstly opposes this movement to ensure return of the part 16 (greater diameter part 22B), then in order to cause the strip element 53 to snap it applies a gauged force to the slider 26 (by the part 22A with lesser diameter turns).

The slider movement drags the strip or contact element 53 into movement, its projecting portion 66 sliding on the fixed abutment 67. This action causes the strip or contact element 53 to bend such that its transverse third part 58 withdraws from the fixed contacts 5 and moves towards the part 25 of the slider 26 (Figure 2). The movement of the strip element 53 is a snap movement.

When the action of the lever terminates, the spring 22 urges the part 16 towards the end 12 of the cavity 10 while simultaneously, as the thrust on the slider 26 decreases, this latter rises within the piece 30 (urged by the contact or strip element 53 which acts as a spring), its projecting portion 66 withdrawing from the fixed abutment, while the elasticity of the strip element 53 causes this latter to again deform such as to move the movable contacts 54 towards the fixed contacts 5 (Figure 2). The snap switch can evidently operate in opposite manner to that described,

i.e. be normally closed when at rest, and open (to enable the electrical circuit connected to the fixed contacts 5) when the part 16 moves towards the portion 3. This opposite solution to the aforedescribed is achieved by simply rotating the slider 26 through 180° about the switch longitudinal axis W and using a strip element with contacts located on the opposite side. The switch operation in this configuration (of Figure 4) is clear in the light of the aforegoing and will therefore not be further described.

Figures 5 and 6, in which parts corresponding to those of the already described figures are indicated by the same reference numerals, show a variant of the invention. This variant differs from that described in relation to the preceding figures in that the cylindrical part 16 cooperates with a first spring 100 inserted in a seat 101 of a cup-shaped part 102 arranged to cooperate with a spring 105 resting on the membrane 42. The cylindrical part 16 has opposing lugs 110 on which an end 111 of the first spring 100 rests, this part presenting a second end 113, opposing the first 15, which projects from the lugs 110 and is inserted into the spring 100.

A second end 115 of this latter is inserted into the cup-shaped part 102; this latter presents a collar 120 on which a first end 121 of the spring 105 rests, a second end 122 of this latter resting on the membrane 42 which is flat and presents an annular boss 42K (whereas the shaped part 42A present in Figures 1 -4 has disappeared).

The cup-shaped part 102 presents elongate lateral windows 126 into which the lugs 110 of the cylindrical part 16 are inserted and slidably guided such that this can guidedly move relative to the cup against the action of the spring 100. Finally, compared with Figures 1 -4, the slider 26 lacks the bent end 60.

In the variant of Figures 5 and 6, two springs (100 and 105) are present having different characteristics and hence different responses to axial stresses (due to the movement of the parts 16 and 102). In this manner the switch intervention

can be suitably adjusted and its operation made more progressive. In particular, the spring 100 is more yieldable than the spring 105 so that, during switch intervention, the spring 105 opposes movement of the part 102 and of the part 16 to ensure that this latter returns to its rest position (Figure 6). On exceeding a preset elastic limit, the spring 105 is compressed to cause movement of the slider 26 and (in the case shown in the figures) activation of the electrical contact between the contacts 5 and 54.

This variant hence enables the switch intervention to be more easily adjusted than in the embodiment of Figures 1 -4. The switch of the invention is simple to construct, is sealed and comprises a small number of components, so facilitating its assembly and limiting construction costs.

It also enables very rapid passage from the condition in which the contacts 5 are closed to the condition in which the contacts 5 are open, preventing electric arcs arising between the fixed contacts 5 and the movable contacts 54. The switch hence has a longer life. The movable contacts 54 applied to the strip element are of sintered material, so further reducing electric arc generation. The closure rate of the fixed contacts 5 (and of their opening) is advantageously determined by the force of the spring 22. By suitably choosing the rigidity of the spring 22 (or of its parts 2A, 2B) and that of the strip element 53, a suitable time-controlled intervention of the switch is achieved and any undesirable movement of the slider 26 within the portion 2 of the switch body 1 is avoided. A preferred embodiment of the invention has been described. Others can however be deduced from the aforegoing description, while remaining within the scope of the ensuing claims.