Parts for two-wheeled vehicles with improved sealing performance from the outside

Abstract: Two-wheeled vehicle parts in accordance with the present invention includes: a first cover (11) having a functional element therein and having a cross-section of a shape to cover the functional element, a second cover (13) corresponding to the first cover so that an end surface of the second cover can be engaged with that of the first cover, and having a cross-section of a shape to cover the functional element, and a projection (25) formed on either the end surface of the first cover or that of the second cover. The first cover and the second cover have respective end surfaces connected with each other through the projection by ultrasonic welding.

Description: The present invention relates to a bicycle speedometer according to the precharacterizing part of claim 1 and a method of manufacturing such a bicycle speedometer according to the precharacterizing part of claim 2. Such a bicycle speedometer and a method for producing such a bicycle speedometer are wellknown by prior use and will be described with reference to fig. 9 to 11. A display portion 3 in which a liquid crystal display (LCD) is made through a lens 4 is formed in a central portion of a front surface of the bicycle speedometer. A mode switch 5 for switching various types of measuring modes and a start/stop switch 7 for switching the start and the stop measurement are formed in a lower portion of the speedometer. Speedometer 1 comprises a lower cover 13 for covering a portion where such a functional element as a crystal oscillator 23 is attached to a base plate 21, and an upper cover 11 having display portion 3 attached thereto. In lower cover 13, a bracket groove 45 that is slidably engaged with a bracket (not shown) attached to component parts such as a handle or the like of a bicycle is formed. A battery cover 17 that is freely opened or closed for use in attachment of a battery 19 is formed in the center of lower cover 13. End surfaces of upper cover 11 and lower cover 13 correspond to each other over their entire circumferences. An O ring 39 attached to a groove formed in upper cover 11 allows an attachment of upper cover 11 and lower cover 13 by sealing. In this state, by fastening screws 41 set at four corners of lower cover 13, the inside of the speedometer is protected from being affected by water drops or the like from the outside by action of the O ring. In the above-described conventional two-wheeled parts, O rings 39 must be attached on the entire circumference, and screws 41 must be attached to the external four corners, as also shown in Fig. 11. Thus, a complicated manufacture is inevitably required to process attachment portions of the O rings, and two-wheeled vehicle parts must be unnecessarily larger in order to obtain attachment portions for screws 41 at the four corners. From Hoisenstamm Branson, Ultraschall für das Kunststoff-Fügen, 1985, page 15 it is wellknown in general to seal together two parts by ultrasonic welding through a projection provided for at one of the mating peripheral surfaces prior to welding. Said projection has a triangular cross-section. This technique however was not applied in the field of production of bicycle speedometers. It is an object of the invention to provide for an improved bicycle speedometer and a method for manufacturing such an improved bicycle speedometer. The speedometer solving the object is characterized in claim 1. The method of manufacturing such a bicycle speedometer is characterized in claim 2. As a result thereof a bicycle speedometer can be provided having a smaller size compared with traditional bicycle speedometers and having a higher sealing performance. Specific embodiments of the invention are described in the sub-claims. In the following an embodiment of the invention is described with reference to the drawings. Fig. 1 is a plan view of a bicycle speedometer; Fig. 2 is a sectional view taken along the line II-II of Fig. 1; Fig. 3 is an enlarged view of an "X" portion of Fig. 2; Fig. 4 is a front view of an ultrasonic welding machine employed in the one embodiment of the present invention; Fig. 5 is a side view of the ultrasonic welding machine of Fig. 4; Fig. 6 shows measurement data in ultrasonic welding in the elapsed time of 0-50ms, according to the one embodiment of the present invention; Fig. 7 shows measurement data in ultrasonic welding in the elapsed time of 50-100ms, according to the one embodiment of the present invention; Fig. 8 shows measurement data in ultrasonic welding in the elapsed time of 100-150ms, according to the one embodiment of the present invention; Fig. 9 is a plan view of a conventional bicycle speedometer; Fig. 10 is a sectional view taken along the line X-X of Fig. 9; and Fig. 11 is a rear view of the speedometer of Fig. 9. The structure of the bicycle speedometer will now be described with reference to Figs. 1-3. A plane structure of a bicycle speedometer 1 is basically the same as that of Fig. 9 shown in the conventional example. More specifically, in a central portion of speedometer 1 is formed a display portion 3 in which a liquid crystal display or the like is made through a lens 4. In a lower portion of the speedometer is formed a mode switch 5 for switching various types of measurement modes. In a right hand portion thereof is formed a start/stop switch 7 for controlling the start and the stop of measurement. A reset unit 9 for resetting a measurement display of the speedometer is provided between display portion 3 and mode switch 5 and start/stop switch 7. The speedometer 1 includes an upper cover 11 and a lower cover 13. A base plate 21 having such a functional element as a crystal oscillator 23 mounted thereon is attached to upper cover 11. A battery cover 17 that opens and closes when a battery 19 is entered and taken out is formed below lower cover 13. In this embodiment, however, there are provided neither screws for attaching upper cover 11 and lower cover 13 together nor O rings for allowing a sealed state of these covers. Instead, in order that the end surface of upper cover 11 and that of lower cover 13 are firmly connected to each other, a projection 25 with a triangular cross-section is formed on the end surface of lower cover 13. When upper cover 11 and lower cover 13 are provided with ultrasonic oscillation, with the end surface of upper cover 11 and projection 25 formed on the end surface of lower cover 13 being mutually pressed, projection 25 and the end surface of upper cover 11 are ultrasonic-welded. Referring to Figs. 4 and 5, a receiving jig 27 to which speedometer 1 is attached is formed on a top surface of the welding machine. A concavity conforming to the shape of lower cover 13 of the speedometer is formed in the receiving jig. An oscillation unit 31 for providing various types of oscillations is attached to an upper portion of the welding machine, and a tool horn 29 is attached to a tip end of oscillation unit 31. A concavity corresponding to the shape of upper cover 11 of speedometer 1 is formed in a lower portion of tool horn 29. A control panel 35 for setting values of various types of welding conditions is formed on a right side surface of the welding machine. An operation panel 33 for controlling the start of a vertical movement of tool horn 29 and controlling the start or the stop of oscillation applied by oscillation unit 31 is formed in an upper portion on the front side of the welding machine. An air control unit 37 for controlling pressure applied by oscillation unit 31 is attached to the left side of the front surface of a welding portion. As a specific welding operation, with the respective end surfaces of upper cover 11 and lower cover 13 constituting speedometer 1 being correspondent with each other, upper cover 11 facing downward is attached to the concavity of receiving jig 27. Tool horn 29 is fallen downward by operating operation panel 33 in such a state. Then, tool horn 29 is fallen down to a predetermined position. With the speedometer fixed between tool horn 29 and receiving jig 27, a predetermined oscillation is provided to speedometer 1 through oscillation unit 31. The oscillation provided to upper cover 11 and lower cover 13 causes projection 25 pressed to the end surface of upper cover 11 to be melted by a friction heat caused by the oscillation and then connected to the end surface of upper cover 11. Thus, welding is completed. According to the result of a test, appropriate sizes of the shapes of a connection 15 and projection 25 are: W = 2 - 3mm, H = 0.4 - 0.6mm and ϑ = 80° - 90°. A ratio a/b of a depth dimension a of upper cover 11 and that b of lower cover 13 from connection 15 shown in Fig. 3 is preferably smaller than "1". This is because the oscillation caused by tool horn 29 is applied from the lower cover side to the upper cover side having a functional element. Figs. 6-8 show measurement data provided by measuring the oscillation applied to speedometer 1 by the ultrasonic welding machine, according to the one embodiment of the present invention. This measurement data is data obtained by attaching an acceleration sensor onto base plate 21 mounted inside speedometer 1 and then measuring acceleration. Fig. 6 (1) shows acceleration data in the elapsed time of 0 - 50ms, and Fig. 6 (2) shows data obtained by frequency-analyzing an oscillation applied by the ultrasonic welding machine in the above elapsed time. Fig. 7 shows data of acceleration in the elapsed time of 50 - 100ms, and data obtained by frequency-analyzing the oscillation. Fig. 8 shows acceleration data in the elapsed time of 100-150ms, and data obtained by frequency-analyzing the oscillation in the elapsed time. The measurement data indicates one example of data provided in such a case that when an external ultrasonic oscillation is provided, such a functional element as crystal oscillator 23 in speedometer 1 is not damaged and upper cover 11 and lower cover 13 are ultrasonic-welded. If the crystal oscillator is fixed onto the base plate by adhesives or the like, an oscillation occurring during ultrasonic welding are liable to be transmitted through the base plate to the crystal oscillator, so that the crystal oscillator is sometimes damaged. It is thus desirable not to fix the crystal oscillator on the base plate by employing adhesives. In this example, while natural oscillation of the crystal oscillator is 32kHz, center frequency of the provided oscillation is 20kHz. Accordingly, it is considered that there are other conditions than that of such measurement data, on which no internal functional element or the like is damaged even by ultrasonic welding. While triangular projection 25 is formed on the end surface of lower cover 13 in the foregoing embodiment, such a projection may be formed on upper cover 11, and projection 25 may be of other shapes than triangle which allow ultrasonic welding.

Claims: Bicycle speedometer comprising a housing made of a lower cover (13) and an upper cover (11), the upper cover having a display portion (3), housing a crystal oscillator, the lower cover and the upper cover having their circumferential end surfaces adjacent to each other, characterised by the two covers (11, 13) having been sealed together by ultrasonic welding, through a projection (25) provided for at one of the mating circumferential end surfaces prior to welding. Method of manufacturing a bicycle speedometer comprising a housing made of a lower cover (13) and an upper cover (11), the upper cover (11) having a display portion (3), housing a crystal oscillator, the lower cover and the upper cover having their circumferential end surfaces adjacent to each other, characterised by providing for a projection (25) at one of the mating circumferential end surfaces, and sealing together the two covers (11, 13) by ultrasonic welding. Method according to claim 2, wherein said projection (25) has a triangular cross-section. Method according to claim 3, wherein said triangle has a vertex angle of 80° to 90°. Method according to one of claims 2 to 4, wherein said projection is formed on the circumferential end surface of said lower cover (13). Method according to one of claims 2 to 5, wherein said upper cover (11) and said lower cover (13) are connected by welding through said projection (25) by ultrasonic welding in said connecting step.

Inventors: SAKURAI NOBUO, SAKURAI, NOBUO
Applicants: CATEYE CO LTD, CATEYE CO., LTD.
Application year: 1992
Main classification: B62J39
IPC codes: B23K20, G01P1, B29C65, B62J99