On-board vehicle instrument comprising a dial and an operating mechanism

Abstract: The device consists of a bayonet connector (34) located between the dial (31) and the body (11) of the operating mechanism (10), and comprising at least two appendixes (21, 22) projecting radially from the body (11) of the mechanism (10), and two upside down L-shaped elements (36) formed in one piece with the dial (31). The connector (34) is rendered active by simply rotating the body (11) and the dial (31) in relation to each other. The device also comprises guide means (42, 43) for enabling foolproof fitment of the body (11) to the dial (31); and stop means (44, 46) for arresting the aforementioned rotation.

Description: The present invention relates to an on-board vehicle instrument comprising a dial and an operating mechanism. Vehicle cabs and particularly the dashpanels of automobiles are fitted with various on-board instruments, such as speedometers, odometers, clocks, temperature gauges, etc., the operating mechanism of which normally presents a substantially cylindrical body terminating at one end with a shaft fitted through the dial and connected to the pointer. The body presents at least two assembly appendices projecting laterally in relation to the end fitted with the through shaft. The automobile industry demands increasing output of increasingly low-cost instruments, which therefore means maximizing automation in terms of both component manufacture and assembly. As yet, the dial and operating mechanism of known on-board instruments are normally assembled using screws, which do not permit fully automated assembly by handing devices or robots. Consequently, assembly is relatively time-consuming, and the finished instruments invariably expensive. It is known from the document US-A-4 753 112 a gauge, such as a pressure gauge, having a visible indicator for rotation about a central axis, and an internal gauge mechanism housed in a substantially cylindrical case. The indicator is protected by a glass assembled on the case by means of a bayonet ring. This latter comprises embossments defining cam surfaces, which can be engaged by corresponding cam followers secured to the exterior surface of the case. It is an object of the present invention to provide a straightforward, low-cost on-board instrument of the aforementioned type. According to the present invention, there is provided an on-board vehicle instrument comprising a dial and an operating mechanism, wherein said mechanism comprises a substantially cylindrical body terminating at one end with a shaft fitted through said dial and connected to a pointer of the instrument; said body comprising at least two assembly appendices projecting radially from said end; and said dial comprising an opening for said shaft; characterized in that said dial comprises at least two L-shaped elements projecting axially from said dial, and that said appendices and said two L-shaped elements form part of a bayonet connector for connecting said dial to said body. A preferred, non limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which: Fig. 1 shows a partially sectioned side view of an on-board vehicle instrument according to the present invention; Fig. 2 shows a view of the instrument along line II-II in Fig. 1; Fig. 3 shows a view of the instrument operating mechanism along line III-III in Fig. 1; Fig. 4 shows a view of the instrument dial along line IV-IV in Fig.1; Fig. 5 shows a section along line V-V in Fig. 4; Fig. 6 shows a section along line VI-VI in Fig. 4; Fig. 7 shows the Fig. 2 view in the preassembly position. Number 10 in Fig.1 indicates the operating mechanism of an on-board vehicle instrument, such as a speedometer. Mechanism 10 may consist of an electric motor or electromagnet, and is housed inside a cylindrical body 11 terminating at one end with a crosspiece 12 (Fig.3) having a central hole 13 through which is fitted a shaft 14 rotated in known manner by mechanism 10. Body 11 terminates at the other end with a plate 16 (Fig.2) in the form of an irregular polygon, and having a portion 17 with at least three sides 18 projecting in relation to cylindrical body 11. From plate 16 there extend three pins 19 (Fig.1) which are connected in known manner to an electrical receptacle on the dashpanel. Crosspiece 12 (Fig.3) presents two substantially diametrically-opposed appendices 21 and 22 for fitting the instrument to the dashpanel and projecting radially from body 11. In particular, appendices 21 and 22 are symmetrical in relation to plane S and therefore of different shapes. Appendices 21 and 22 present respective locating holes 23, and respective depressions 24 extending angularly from respective holes 23 in opposite directions, so that appendices 21 and 22 are symmetrical. Each depression 24 presents a further hole 26 for fitment to the dashpanel, and is defined by a lateral wall 27 concentric with hole 26. Finally, each appendix 21 and 22 presents a lateral wall 28 opposite depression 24. The instrument also comprises a circular dial 31 (Fig.s 1 and 2) molded from thermoplastic material and having a central opening 32 (Fig.s 4-6) through which shaft 14 is fitted. The outer surface 33 of dial 31 presents the usual markings for the pointer, which is fitted to shaft 14. According to the present invention, dial 31 is assembled to mechanism 10 by means of a bayonet connector indicated as a whole by 34. In particular, dial 31 comprises two flexible, L-shaped elements 36 projecting axially from inner surface 37 of dial 31, and located angularly so as to correspond with appendices 21 and 22 of crosspiece 12. Elements 36 are formed in one piece with dial 31, and, at each element 36, dial 31 presents a recess 38 for achieving greater flexibility. The end of each element 36 presents a pin 39 parallel to the axis of dial 31 and having a curved or preferably semispherical end 41 designed to engage hole 23 in appendix 21, 22 of crosspiece 12. Dial 31 also presents guide means for foolproof fitting of body 11 on to dial 31. Said guide means comprise a locating pin 42 designed to laterally engage wall 28 of appendix 21 of crosspiece 12, opposite to depression 24 (Fig.s 4-7); and a pin 43 shorter than pin 42, and the end of which frontally engages depression 24 of the other appendix 22 of crosspiece 12. Pins 42 and 43 are so located that any attempt to fit or preassemble mechanism 10 to dial 31 in a position wherein they are mutually rotated 180° results in the longer pin 42 frontally engaging appendix 22 outside depression 24, which error is communicated to the operator or handling device. Dial 31 also presents means for arresting rotation (clockwise in Fig, 7) of bayonet connector 34, which means comprise two pins 44 and 46 arranged in such a manner that pin 44 arrests wall 27 of appendix 21, adjacent to depression 24, while pin 46 arrests wall 28 of appendix 22, opposite to depression 24. Finally, inner surface 37 of dial 31 presents a rib 47 of the same shape as at least the three sides 18 of projecting portion 17 of plate 16, which sides 18 are so arranged as to remain permanently within rib 47 when rotated from the Fig.7 to the Fig.2 position, and are only aligned with rib 47 upon completion of the assembly operation, of which rib 47 thus acts as an optical reference. To assemble dial 31 and mechanism 10, mechanism 10 is first brought frontally up to surface 37 of dial 31, so that depression 24 of appendix 22 rests on the end of pin 43, and wall 28 of appendix 21 rests laterally on pin 42. Though mechanism 10 is thus slightly offset in relation to dial 31 (as shown in Fig.7), the diameter of opening 32 in dial 31 is such as to still enable insertion of shaft 14. At this point, dial 31 and mechanism 10 are rotated in relation to each other, so that mechanism 10 turns clockwise in relation to dial 31, and so that appendices 21 and 22 engage the semispherical ends 41 of pins 39 by flexing the two L-shaped elements 36, and are eventually arrested against respective pins 44 and 46. In this position, holes 23 of appendixes 21 and 22 at least partially engage ends 41 of pins 39, despite shaft 14 being offset in relation to opening 32. When mechanism 10 is then released, the elastic force exerted by elements 36 via semispherical ends 41 aligns holes 23 perfectly with pins 39 so as to form a certain amount of clearance between appendices 21 and 22 and pins 44 and 46, as shown in Fig.2. The advantages, as compared with the known technique, of the assembly device according to the present invention will be clear from the foregoing description. In particular, it requires no screws or additional fastening elements; assembly may be effected easily by means of a handling device involving only a minimum number of movements and control members; and the dial may be mass produced easily on a high-output thermoplastic molding press. To those skilled in the art it will be clear that changes may be made to the device as described and illustrated herein, for example, changes may be made to the number and design of appendices 21 and 22, elements 36, locators 42 and 43, and stops 44 and 46; and rib 47 may either be dispensed with or replaced by any other type of reference element.

Claims: On board vehicle instrument comprising a dial and an operating mechanism, where in said mechanism (10) comprises a substantially cylindrical body (11) terminating at one end with a shaft (14) fitted through said dial (31) and connected to a pointer of the instrument; said body (11) comprising at least two assembly appendices (21, 22) projecting radially from said end; and said dial (31) comprising an opening (32) for said shaft (14); characterized in that said dial (31) comprises at least two L-shaped elements (36) projecting axially from said dial (31), and that said appendices (21, 22) and said two L-shaped elements (36) form part of a bayonet connector (34) for connecting said dial (31) to said body (11). An instrument as claimed in Claim 1, characterized in that it presents guide means (42, 43) for foolproof fitting of said body (11) to said dial (31); and stop means (44, 46) for arresting the rotation of said body (11) relatively to said dial (31). An instrument as claimed in Claim 2, wherein each of said appendices (21, 22) comprises a locating hole (23) and a depression (24), each depression (24) extending angularly from its associated hole (23) in opposite directions, so that said appendices (21, 22) are symmetrical to each other with respect to a plane (S) through the longitudinal axis of said cylindrical body (11); characterized in that said guide means (42, 43) comprise a first pin (42) so designed that upon insertion of said body (11) in said dial (31) it engages a wall (28) of a first of said appendices (21, 22) opposite to its depression (24); and a locating member (43) shorter than said first pin (42) and designed to frontally engage said depression (24) of the other of said appendices (21, 22). An instrument as claimed in Claim 3, characterized in that the end of each said element (36) presents a second pin (39) parallel to said first pin (42) and terminating in a curved end (41); the curved ends (41) of each of said appendices (21, 22) being engaged by said locating holes (23) for correctly positioning said cylindrical body (11) upon rotation of said body (11) relative to said dial (31). An instrument as claimed in Claim 3 or 4, characterized in that said opening (32) is large enough to enable said body (11) to be prepositioned noncoaxially in relation to said opening (32); said elements (36) being so arranged that said curved ends (41) at least partially engage said locating holes (23) following said rotation. An instrument as claimed in Claim 5, characterized in that said elements (36) are formed in one piece with said dial (31), which presents a recess (38) associated with each element (36); said elements (36) and said recesses (38) being so sized as to render said elements (36) flexible enough to align said locating holds (23) with respective said curved ends (41). An instrument as claimed in one of the foregoing Claims 2 to 6, characterized in that said stop means comprise first and second stop pins (44, 46) arranged in such a manner that one of said first or second stop pins (44, 46) arrests a wall (27) of said first appendix (21) adjacent to its depression (24), and the other of said first or second stop pins (44, 46) arrests a wall (28) of said second appendix (22) opposite to its depression (24). An instrument as claimed in one of the foregoing Claims 2 to 7, wherein said body (11) presents a polygonal end plate (16); characterized in that said dial (31) presents a rib (47) of the same shape as at least three sides (18) of said polygon, and which serves to optically indicate correct assembly.

Inventors: PAGANINI RICCARDO, PAGANINI, RICCARDO
Applicants: MAGNETI MARELLI SPA, MAGNETI MARELLI S.p.A.
Application year: 1993
Main classification: B60K35
IPC codes: B60K35, G01D11