SNAP-ACTION FASTENING DEVICE FOR CONTROL AND/OR SIGNALLING UNITS

Abstract: A snap-action fastening device for control and/or signall­ ing unit comprises a sleeve (1) with a shape corresponding to and suitable for cooperating with a cantilevered rear portion (40) of an operating unit (4) equipped with shaped surface grooves (41), said sleeve having a shape complementary to that of said rear portion of the operating unit slipped as a bayonet into said sleeve, the internal surface of the latter being provided with ridges (10) making part of said bayonet coupling, the outer surface of the said sleeve being partially threaded, a ring nut (2) threaded to the outer surface of said sleeve, means for securing electrical elements (7) of the control and/or signalling unit to said sleeve, said securing means comprising a separated annular element (3) inter­ posed between said sleeve (1) and said electrical element (7), said annular element (3) being suitable for engaging, by snap-action means, some stop means (12, 13, 14, 15) provided on the sleeve, and being equipped with means for releasably securing said electrical elements.

Description: Snap-action fastening device for control and/or signalling units The present invention relates to a snap-action fastening device for control and/or signalling units, wherein the configuration and the arrangement of the elements shall confer on it some useful characteristics. Among the systems known in the art, for securing on a panel board control and/or signalling units, such as switches and warning and/ or signalling lights, those generally used consist of securing the operating unit of the control -unit to the panel board by means of a threaded ring nut: the ring nut is threaded frontally on the body ofthe control unit which is previously slipped into a proper seating of the panel board, in such a manner as to secure it to the latter. Another system commonly used for securing to the panel a control unit, consists of the use of securing and shimming screws which operate between the panel and the body of the control unit housed into a proper seat of said panel. However the above systems have some important drawbacks: for example, the first type of connection cannot prevent that a voluntary or fortuitous unscrewing of the ring nut from the outer side of the panel shall cause the resulting desactivation of the control unit; secondly, the system with shimming screws has the disadvantage of making very troblesome and difficult the centering of the control unit on the panel. With the purpose of solving said troubles, the italian application for utility model No. 21111-B/80 in the name of the same applicant, has proposed the use of a control unit with snap-action group having a threaded ring nut; said fastening group consists substantially of an operating unit at its rear portion with a shaped portion which can be introduced as a bayonet into a threaded sleeve, equipped with a ring nut, which latter is the intermediate element for securing the control unit to the panel (by means of the ring nut) and the element for securing the electric elements to said operating unit through proper securing means built in said sleeve. The operation for securing the control unit to the panel of a board or of an instrument is carried out by means of a proper tool acting on the ring nut of the threaded sleeve. The purpose of the present invention is that of improving the securing system illustrated in the above mentioned italian application, permitting in particular to simplify and to accelerate the operations for mounting the operating unit of the control unit to the panel, however preserving and improving the special effects and advantages of the snap-action fastening system. The above and other purposes and advantages are obtained with the fastening device of the present invention of the type consisting of a sleeve of a corresponding configuration and suitable to cooperate with a cantilevered rear portion of an operating unit equipped with shaped surface grooves, said sleeve having the shape which is complementary to that of said rear portion of the operat ing unit, bayonet slipped with snap-action into said sleeve, wherein the sleeve is featured by a partially threaded outer surface and some ridges on the inner surface, forming part of said snapaction device; a threaded ring nut on the outer surface of said sleeve; means for securing the electric element of the control and/or signalling unit to said sleeve, said fastener device being substantially characterized in that said securing means consist of an annualr element separated and interposed between the said sleeve and the said electric element, said annular element being suitable to engage, by snap-action means, some stop means present on said sleeve, and being equipped with means for releasably securing said electric element. Said annular element of the securing device according to the invention consists of a coupling flange with a stationary portion of frame, having a configuration corresponding to that of the sleeve, in which is installed and slides, on the plane of the said stationary portion, a guillotine element properly shaped for a snap-action engagement, against the action of proper return springs, on said sleeve which , in turn, is provided with proper seatings into which engage some teeth of the guillotine element. According to the invention, the profiles of the portions of each other engaging sleeve and guillotine elements are properly shaped and slanting such as to form a mouth for the introduction of the sleeve into the guillotine. Moreover the guillotine shows some conventional means for the attachment of the electric element of the control and/or signaling unit. The above and other characteristics are illustrated in the follow ing specification with reference to the enclosed drawings which illustrate a preferred embodiment of the fastening device given as a not limitative example of the present invention. Fig. 1 is an exploded and partial section view of the control unit equipped with the fastening device in accordance with the present invention; Fig. 2 is a front detailed view of the coupling flange of the device of Fig. 1; Fig. 3 shows the detail of the engagement between the operating unit and sleeve; and Fig. 4 shows in transverse section the details of the flange of Fig. 2 coupled on the sleeve of the fasting device in accordance with the present invention. Now referring to the above figures, the instant control unit com- prises a snap-action fastening device consisting of a sleeve 1 with outer surface partially threaded, a threaded ring nut 2 which can be threaded on the threaded outer surface of the sleeve 1 and an annular element or coupling flange 3. Moreover, the control unit comprises the operating unit 4, secured to the panel board 5 through said fastening device and a gasket 6, and the electric unit 7. The operating unit 4, in which a movable push-buttom (dotted line in Fig. 1), is installed, is featured by a cantilevered rearpor- tion 40 cooperating with said fastener device, which can be introduced as a bayonet in a conventional manner firstly through a suitable hole in the panel 5, and secondly into the sleeve 1 of the fastening device. Advantageously, the outer surface the cantilevered portion 40 of the operating unit 4 is featured by L-shaped grooves 41 which slidingly engage proper ridges 10 integral with the internal surface of the sleeve 1: the relative rotation of the operating unit 4 with bayonet coupled portion 40 into the sleeve 1 causing the motion of the ridges 10 into the grooves 41, and a resulting engagement between the parts. The final securing of the unit 4 to the panel 5 is attained, with the gasket 6 slipped onto the rear portion 40, by screwing the ring nut 2 on the sleeve 1 until this tighten against the corresponding surface of the panel 5. According to the improvements of this invention, the mutual connection between the operating unit 4 and the electric element 7 is obtained through a coupling flange 3 (see Fig. 2) consisting of a frame 30, shaped substantially as the not threaded rear portion 11 of the sleeve 1, into which slides on the plane of said frame, a guillotine element 31; for the purpose, the frame 30, representing the stationary portion of the coupling flange 3, is featured onto the inner profile by a substantially periferal groove 32 (Fig. 1) which represents a guide to the motion of the guillotine 31 against the action of the return spring 33 properly mounted into said frame 30. The latter has on its upper portion a guide rib 34 and a seat 35 for the engagement of conventional means (screws or the like) suitable for securing the electric element 7 of the control unit to the coupling flange 3. The guillotine element 31 consists substantially of a U-member closed on the frame 30 and having an upper portion 36 extending from the frame 30, on which the guillotine can be rised up manually or by means of a screw driver when it is desired to disengage the flange 3 from the sleeve 1; the profile of the element 31 faced internally the frame 30 is properly shaped in such a manner to engage with a snap-action the rear portion 11 of the sleeve 1. More specifically, said profile is equipped with extending teeth 20, 21, 22 and 23, whose front surface (see Fig. 2) is properly slanting to form a mouth for introducing, against the action of the springs 33, the portion 11 of the sleeve 1 into said flange 3. In order to obtain the mutual engagement among said parts, the rear portion 11 (non threaded and uncovered by the ring nut 2) of the sleeve 1 has some suitable projections 12, 13, 14, 15 (the last two not visible) and a groove 16 respectively for the engagement with the teeth 20 to 23 of the guillotine 31, and with the guide rib 34 of the- frame 30 of the flange 3 (see Fig. 4). The front profile 18 of the portion 11 of the sleeve 1, including the projections 12 and 15, that is the portion of the sleeve enter ing first in contact with the coupling flange 3, has some properly slanting walls in correspondence with the coupling surfaces of the teeth of the guillotine, such as to promote the engagement. The coupling is obtained by pressing the guillotine 31 against the portion 11 of the sleeve 1: in this manner the guillotine 31 is raised up, a motion which is facilitated by the slanting of the above described interacting surface, against the action of the springs 33; once the lifting up is completed, the teeth of the guillotine overcome the front shaped profile of the portion of sleeve 11 and of the projection 12 to 15, and they engage them. Moreover, the engagement of the rib 34 of the flange 3 into the groove 16 of the portion of sleeve 11, allows a correct mutual positioning of the parts (Fig. 4). As has been illustrated in Fig. 3, on the outer surface of the operating unit portion 40 corresponding to each groove 41, three in number in the illustrated example, a projecting small tooth 9 is provided, having substantially the object of preventing the return motion of the ridges 10 into said guide elements 41, thus ensuring a first provisional engagement of the sleeve 1 onto the operating unit portion 40. This is particularly useful for preventing in the course of tightening the ring nut 2 a possible motion and therefore the possible disengagement of the operating unit portion 40 from the sleeve 1. As stated, the assembling of the control unit is completed by securing the electric element 7 to the coupling flange 3, this operation being possible both before and after the engagement of the said flange 3 to the sleeve 1. In the example of Fig. 1, the securing of the electric element 7 to the flange 3 is carried out by means of a screw 70 threaded into the threaded seat 35 of said flange and/or through other not illustrated conventional means. It is to be understood that this invention is not limited to the disclosed embodiment and it is intended to cover all modifications coming within the spirit and scope thereof.

Claims: Claims 1. A snap-action fastening device for control and/or signalling unit comprising a sleeve (1) with a shape corresponding to and suitable for cooperating with a cantilevered rear portion (40) of an operating unit (4) equipped with shaped surface grooves (41), said sleeve having a shape complementary to that of said rear portion of the operating unit slipped as a bayonet into said sleeve, the internal surface of the latter being provided with ridges (10) making part of said bayonet coupling, the outer surface of the said sleeve being partially threaded; a ring nut (2) threaded to the outer surface of said sleeve; means for securing electrical elements (7) of the control and/or signalling unit to said sleeve, characterized in that said securing means comprise a separated annular element (3) interposed between said sleeve (1) and said electrical element (7), said annular element being suitable for engaging, by snap-action means, some stop means provided on the sleeve, and being equipped with means for releasably securing said electrical elements. 2. The fastening device of claim 1, characterized in that said annular element consists of a snap-action coupling flange (3) which has a stationary part or frame (30), having shape correspond ing to that of the said sleeve, into which is slidably installed1 on the plane of the said frame, a guillotine element (31), said snap-action means being formed by coupling teeth (20, 21, 22, 23), integrally mounted with said guillotine element, movable from a retracted position wherein said annular element is disengaged from said sleeve, to an operative position wherein said coupling teeth enter the stop means provided on said sleeve, spring means (33) being provided for urging said snap-action engaging means toward said operating position. 3. The fastening device of claim 1 and 2, characterized in that said stop means consist of shaped projections (12, 13, 14, 15) provided on the note threaded rear portion (11) of said sleeve, into said shaped projections engaging said teeth of the guillotine element of the coupling flange. 4. The fastening device of claims 1-3, characterized in that the front surface of the teeth of the guillotine and that of the front edge of the sleeve and of its projections interferring with the said teeth are slanting with respect to a transversal plane of the coupling flange and of the sleeve, respectively. 5. The fastening device of previous claims, characterized in that the stationary portion or frame of said coupling flange is moreover provided with a rib (34) suitable for guiding, through the engagement into a corresponding groove (16) provided on the portion of sleeve (11), the entering of said flange on the sleeve, (1), an internal periferal groove (32) for guiding the motion of the guillotine element, and moreover a threaded seat (35) which represents the securing releasable means of the electrical element (7) to said flange (3). 6. The fastening device of claim 1, characterized in that the outer surface of the cantilevered portion (40) of said operating unit (4), corresponding to the grooves (41) for the engagement with the internal projections (10) of the sleeve (1), is equipped with projecting teeth (9) for mounting in position said ridges into said grooves.

Inventors: FALCHI, FIORINO
Applicants: CGE- COMPAGNIA GENERALE ELETTROMECCANICA S.P.A.
Application year: 1983
Main classification: F16B2
IPC codes: F21V21, H02B1, F21S8