Tappet, in particular for cooperating with camshafts in electrical switches

Abstract: A tappet (1), in particular for cooperating with camshafts (14) in electrical changeover switches (13), circuit breakers or the like, comprises a body (2) provided with a cavity (3) opening into two opposing faces (1A. 1B) of said body (2) and containing, mobile against a spring (6), a generally flat contact element (7) the opposing free ends (8, 9) of which project from said cavity (3) and from said body (2) so as to cooperate with fixed contacts (10, 11) generally arranged to the sides of said body (2) and rigid with the casing (12) of the changeover switch (13) or the like. The mobile contact (7) is subjected to the action of an element or slider (16) mobile within said cavity (3) and arranged to cooperate with the cams (15) of a usual camshaft (14). According to the invention, said slider (16) comprises projecting elements (20) slidable in a guided manner in guide slots or tracks (23) provided in the body (2) of the tappet (1) during its movement within the recess (3) of this latter, with consequent displacement of the mobile contact (7) from an inoperative position to a working position in which it cooperates with the fixed contacts (10, 11) of the changeover switch (13) or the like, said mobile contact (7) rocking relative to said slider (16) by rotating about an axis (A) on being displaced from its working position.

Description: This invention relates to a tappet, in particular for cooperating with camshafts in electrical changeover switches, circuit breakers or the like, of the type recited in the preamble of the attached main claim. Tappets of the type recited in the preamble have been known for some time and have been used for a number of years in the aforesaid electrical components. DE-A-1 33 27 675 discloses a tappet comprising a cage-like body, a slider slidingly mounted in said body, a contact member carried by the slider and protruding from apertures in said body, a reaction spring acting on the slider through the contact member. The reaction spring is located between the contact member and a separate closure means, which is fixable to the body either by snap-action or by welding. The body comprises a front abutment wall for the slider which has an operating nose portion of lower height projecting from the body. The assembly of the tappet is rather complicated. In fact the slider is mounted into the body by inserting it along a predetermined direction through an aperture in the body. The contact member and the spring are then separately inserted in a different direction through a different aperture and then the latter aperture has to be closed by applying the closure member. There is also the risk of the slider being removed from the cage-like body when a transverse force is applied on the slider nose portion. DD-A-259 711 discloses a rockable mobile contact member and means for rocking it for the purpose of imparting a rubbing action on the corresponding fixed contacts. Known tappet generally comprise a number of components such as to make it difficult to assemble, particularly in view of their small dimensions. Their construction is consequently lengthy and laborious, with resultant high cost of the finished electrical component (circuit breaker or changeover switch). An object of the present invention is therefore to provide a tappet of the type recited in the preamble which has lower construction time and cost than known tappets. A further object of the invention is to provide a tappet by which the removal of oxides, scum or the like from both the fixed and mobile contacts takes place during use. A further object is consequently to provide a tappet by which optimum connection is obtained between the fixed and mobile contacts and which is of reliable operation. These and further objects which will be apparent to the expert of the art are attained by a tappet according to the attached claims. The present invention will be more apparent from the accompanying drawings which are provided by way of non-limiting example only and in which: Figure 1 is an exploded perspective view of a tappet constructed in accordance with the invention for cooperating with a camshaft, which is only partially represented; Figure 2 is a perspective view of a tappet according to the invention in its non-operating position; Figure 3 is a partial cross-section through an electrical changeover switch using tappets according to the invention; and Figure 4 is a section on the line IV-IV of Figure 2. With reference to said figures, the tappet is indicated overall by 1 and comprises a body 2, of U-shape in the figures, provided with a cavity 3 which opens into two opposing faces 1A and 1B of said body 2. In the cavity 3 there is arranged a usual compression spring 6 against which a usual contact element (or more simply mobile contact) 7 moves within said cavity 3. Said mobile contact 7 is substantially of flat elongate shape with its opposing free ends 8, 9 arranged to cooperate with fixed contacts 10 and 11 (see Figure 3) rigid with the casing 12 of a changeover switch 13. A usual camshaft 14 comprising cams 15 with which the tappets 1 cooperate is arranged in said casing 12 and supported in known manner. A mobile element or slider 16 is associated with the body 2 of each tappet 1. In the example illustrated and described herein, said slider is substantially of U shape, comprising sides 17 and 18 joined together by a transverse element or headpiece 19, said slider headpiece 19 being arranged to cooperate with a cam 15 associated with the camshaft 14 and provided with a usual recess 15A. According to the invention, with the sides 17 and 18 there are associated projections 20, the region 21 in which they join to the sides 17 and 18 being of larger section than the free end 22, ie each projection 20 has a cross-section in the form of a right angled triangle which tapers towards the end 22 and has its oblique side facing away from said headpiece 19. Said projections 20 are arranged to slide in slots 23 provided in faces 1C and 1D of the body 2 of the tappet and acting as guide racks for the movement of the slider 16. This latter cooperates with the mobile contact 7 which is disposed in a seat 50 in said slider defined by its sides 17 and 18 and is urged by the spring 6 to rest against an inner part 24 of the slider headpiece 19. The outer end 25 of this latter is arranged to cooperate with the cams 15 and comprises inclined lateral ends 26 to facilitate the introduction of the headpiece 19 into the seat 15A of the respective cam 14 and its withdrawal from this latter when said headpiece is not in correspondence with said seat. The inner part 24 of the slider headpiece 19 is inclined (as shown in Figure 4) so that when in its inoperative position (shown in Figure 4 and assumed by the mobile contact 7 shown to the left in Figure 3) the mobile contact 7 is slightly inclined from a position parallel to the base 30 of the body 2 of the tappet 1 (or "vertical" position with reference to the figures). The tappet 1 is mounted easily and rapidly. To achieve this, the spring 6 and contact 7 are arranged in the cavity of the body such that the ends 8 and 9 of the contact project from said cavity. The slider 16 is then associated with said body 2. This is facilitated by the elasticity of the material of construction of these elements (generally plastics) and their U shape. Specifically, the slider 16 is placed at the entrance to the body 2 such that the sides 17 and 18 of the former correspond with the faces 1C and 1D of the latter. The slider is then pushed so that it penetrates into said body 2. Because of the tapered shape of the projections 20 on the slider 16, this insertion is simple and fast, aided also by the shape of the slider and body 2 and their constituent material. In this respect, during said introduction the sides 17 and 18 of the slider approach each other whereas the faces 1C and 1D of the body 2 diverge. This continues until the projections 20 on the slider 16 reach the slots 23. At this point the projections 20 snap-penetrate into the slots 23 and the body 2 returns to its original shape to retain the slider 16. As stated, during use the mobile contact 7 in the inoperative position is inclined to the "vertical" (with reference for example to Figure 3) but reaches "vertical" when in its working position (as represented by the mobile contact 7 on the right of the changeover switch 13 shown in Figure 3). This is due to the action of the cams 15 on each tappet head 16 and the subsequent movement of these latter. In such a situation, each contact 7 rocks relative to the corresponding headpiece 19 by rotating relative to this latter about an axis A passing through a particular line of contact between the inner part 24 of the slider headpiece and the mobile contact itself (line passing through the point K in Figure 4). By this means, each time a cam 15 urges the slider 16 to re-enter the body 2, the mobile contact 7 (arranged "vertically" in Figure 3) separates from the fixed contact by rotating about said axis A. A rubbing action therefore results between said contacts, to remove from them (and particularly from the fixed contact) any scum, impurities or oxides which have deposited on them during the use of the changeover switch. The dimensions of the end 25 of the slider headpiece 19 can vary according to the application of the tappet. A tappet constructed in accordance with the invention is simple and rapid to assemble, is of short construction time, is reliable in use and allows cleaning of the fixed and mobile contacts.

Claims: A tappet (1), in particular for cooperating with camshafts (14) in electrical changeovers (13), circuit breakers or the like, comprising a body (2) provided with a cavity (3) opening into a first pair of opposing face portions (1A, 1B) of the body (2) and containing, mobile against a spring (6), a generally flat contact element (7) the opposing free ends of which (8, 9) project from said cavity (3) and from said body (2) so as to cooperate with fixed contacts (10, 11) generally arranged to the sides of said body (2) and rigid with the casing (12) of the changeover switch (13) or the like, the mobile contact (7) being subjected to the action of a slider (16) mobile within said cavity (3) and arranged to cooperate with the cams (15) of a usual camshaft (14) characterized in that: a) each of the opposing face portions (1A, 1B) of the first pair defining an aperture which opens towards the camshaft (14); b) the body (2) comprises an integrally formed end portion (30) and a second pair of opposing face portions (1D, 1C) extending at right angles from the end portion (30) and each provided with an axially extending and peripherally closed aperture (23); c) the slider (16) comprises integral projections (20) on two opposite faces (17, 19) to snap fit into the peripherally closed apertures (23) wherein said projections (20) are slidable in a guided manner during the movement of the slider (16) within the recess of the body (2), with consequent displacement of the mobile contact element (7) from an inoperative position to a working position in which it cooperates with the fixed contacts (11) of the changeover switch (13) or the like, said mobile contact (7) rocking relative to the slider (16) by rotating about an axis (A) on being displaced from its working position. A tappet according to claim 1, wherein the integral projections (20) of the slider (16) are saw-tooth shaped. A tappet as claimed in claim 1 or 1 and 2 characterized in that the slider (16) comprises an inclined inner wall (24) against which the mobile contact (7) is urged by the spring (6), said contact (7) remaining in an inclined position when not cooperating with the fixed contacts (10, 11) of the changeover switch (13) or the like, i.e. when in its inoperative position, whereas it attains a position parallel to the end portion (30) of the body (2) or non-inclined position when cooperating with said fixed contacts (10, 11) i.e. when in a working position, passage from the non-inclined to the inclined position occurring as a result of the movement of the slider (16) towards the interior of the body (2) when the slider cooperates with a camshaft (14).

Inventors: SPANIO MARINO, SPANIO, MARINO
Applicants: BREMAS SPA, BREMAS S.P.A.
Application year: 1990
Main classification: H01H19
IPC codes: H01H1, H01H19