ELECTRICAL GEAR CHANGER FOR CHAIN
SUMMARY OF THE INVENTION 5
The instant invention relates to an electrically operated derailleur gear changer for a multi-speed chain driven vehicle. The means for initiating a change of gears is an electrical switch, which is located for convenient operation. Upon activation of the switch, the de- 10 railleur is operated by an axle which is driven by a motor driven gear box. Therefore, the instant example derailleur is operated by a direct drive in either direction. The motor's operation is controlled by an angular velocity and rotational direction detector which assures 15 that the motor does not operate unless the sprocket and the chain have attained proper velocity and direction.
The invention also provides for use of a front and rear derailleur system, each of which may be selectively engaged. 20
Cycle gear changes up to the present time have utilized the well known mechanically operated derailleur gear changer, which is activated through a shift lever device attached to the derailleur by means of a cable and operating against spring tension. This prior art op- 25 eration provides numerous shortcomings, chief of which are difficulty of operation, lack of safety, failure of positive shifting between gears, and unreliable operation.
The prior art mechanical derailleur shifting tech- 30 nique is deemed inconvenient in view of the location of the shift lever which is conventionally located on the horizontal leg bar, for example, on a multi-speed racing bicycle for men. Accordingly, the rider of such a vehicle must remove one hand from the handle bar for 35 placement on the shift lever in order to change gears. This must also be accomplished while the rider is in a hunched position. This prior art arrangement is not only inconvenient, but is recognized as being unsafe to all but the very skilled rider. 40
Thus, when a cyclist is pedaling and desires a gear change, he must adopt an unbalanced position to simultaneously apply pressure to the shift lever in order to move the derailleur, and keep a firm grip on the handle bar in order to keep the vehicle on course. In view of 45 the speed of the vehicle, the posture of the operator, and the removal of one hand from the handle bar, an unsafe condition ensues.
Another recognized shortcoming of the prior art gear changer has been the tendency of the chain to jump or 50 skip over several sprockets during the shifting operation. In other words, when there is a need to change from a lower to a higher gear ratio or vice versa, the change does not always occur in an orderly progression. This is an undesirable aspect of the prior art be- 55 cause the cyclist normally selects a sprocket by correct feel and therefore, when there is sprocket skipping, the operator has to labor to find the correct gear or sprocket.
The object of this invention is to remedy the above 60 stated drawbacks. Therefore, it is the purpose of this invention to employ a new type of motor operated derailleur which provides direct drive in either direction and without the need for the shift lever, cable, and tension mechanisms of the prior art. Accordingly, the 65 present invention utilizes a derailleur which can be readily activated for gear changing purposes by an electrical actuator which may be conveniently located on
the handle bars whereby the operator can easily activate the switch.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a perspective view of a cycle rear derailleur gear changer, used in this invention in conjunction with an electrical-mechanical gear box for a chain driven vehicle.
FIG. 2 depicts a top view of a front derailleur gear changer as used in this invention.
FIG. 3 shows the overall circuit schematic employed with the derailleur assemblies shown in FIGS. 1 and 2.
FIG. 4 is a detailed schematic of the angular velocity and rotational direction detector of FIG. 3.
FIG. 5 is a timing diagram showing the sequence of events of FIG. 4.
DESCRIPTION OF THE PREFERRED
Referring now to FIG. 1, there is depicted in general a chain-and-sprocket drive assembly. The change-gear control device depicted is a type well known to the prior art, consisting of a coaxial sprocket group often having a plurality of individual sprockets 10', 102, 103, 104, and 105. Several teeth of the sprockets are shown by way of example. The sprocket group 10 may represent the five rear sprockets, for example, of a tenspeed chain driven bicycle. The chain (not shown) is in engagement with the sprocket 103 as illustrated by: way of a dotted line representing the chain path. The chain also engages a set of idler wheels 18 and a second wheel which is not shown. These idler wheels provide constant chain tension and guidance for movement between sprockets. The sprockets group 10 is shown in FIG. 1 as being connected to the frame 14 by an axle/nut assembly, 26 and 27 respectively.
The derailleur gear changer assembly is connected to the frame 14 by means of the same axle/nut assembly 26, 27 passing through a mounting bracket 29 and is used to transfer the chain from one sprocket to another while pedaling. The derailleur in the well known manner basically comprises two movable arms 21 and 22 which are maintained in a parallel orientation by two derailleur frame members 23 and 24. The members 23 and 24 are attached to the arms 21 and 22 by the pins 2, 3 and 4 and the axle 1. The axle 1 pivots in the derailleur frame 23 so as to drive arm 21 to which it is permanently attached by suitable means. The parallel arms 21, 22 and the frames 23, 24 together comprise a distortable parallelogram. The parallelogram operates to translate its lower end and the pin 25 in the directions shown by the arrow. This action is accomplished in the following manner.
The axle 1 is coupled into a gear reduction box 20, (shown cut away) comprising the gears 31, 32, 33, 34, and 35. The gear 31 is connected to the end of a shaft of a low voltage D.C. motor 30. The gear 35 is connected to the axle 1 so that the latter may be made to rotate upon energization of the motor 30. Also connected to the axle 1 are the cams 40 and 42 which operate in conjunction with the limit switches Li and L2. This aspect of the invention will be discussed in greater detail hereinafter.
In operation, the energizing of the D.C. motor causes the axle 1 to rotate in either the clockwise or counterclockwise direction. A clockwise rotation of the axle 1 causes the parallelogram to distort such that the pin 25 moves outwardly to the drawing such that the idler 18,