GB2120430A

GB2120430A - Zeroizing of counters

Info

Publication number: GB2120430A
Application number: GB08311722A
Authority: GB
Inventors: Rodolfo Bitetti
Original assignee: Fratelli Borletti SpA; Borletti SpA
Current assignee: Fratelli Borletti SpA; Borletti SpA
Priority date: 1982-05-21
Filing date: 1983-04-29
Publication date: 1983-11-30
Also published as: GB2120430B; AR231670A1; FR2527338A1; FR2527338B3; ES272365Y; IT8253316V0; GB8311722D0; ES272365U

Abstract

A device for zeroing the numerical indication given by an odometer cylinder of a speedometer, the said cylinder including a plurality of coaxial discs (2) disposed adjacent one another, and being rotatable on a spindle (5) under the action of transmission means operable to cause each said disc to rotate by a predetermined angle when one of the contiguous discs has performed a complete revolution is described; the rotation of the said spindle with respect to the disc is controlled by means of a rack (21) and pinion assembly (20, 25), and between one element of the said rack and pinion assembly and the said spindle there is located a clutch (30) operable to transmit movement from the rack to the said spindle when the rack is displaced axially in a first directional sense to effect rotation of the said spindle with respect to the disc and not to transmit movement from the said rack to the said spindle when the rack is displaced axially in a second directional sense opposite the first. <IMAGE>

Description

SPECIFICATION A device for zeroing the numerical indication given by an odometer barrel of a speedometer The present invention relates to a device for zeroing the numerical indication given by an odometer barrel of a speedometer, in which the operation is performed manually by axially displacing a rod which projects forwardly from the speedometer.

As is known, an odometer barrel or cylinder of a speedometer comprises a plurality of coaxial discs arranged alongside one another, on the outer surface of which there are provided symbols, and which are rotatable about a spindle by the action of transmission means operable to make each of the discs turn through a predetermined angle when one of the contiguous discs has performed a complete revolution, for the purpose of giving a numerical indication of the distance travelled by the vehicle.

Each of the said discs is freely rotatably mounted on the said spindle and between the disc and the spindle there is interposed a mechanism operable to transmit the movement of the spindle to the disc only when the spindle, upon relative rotation with respect to the disc, assumes a predetermined angular position with respect to this latter; in this way when the said spindle is made to turn, first the same symbols of the various contiguous discs are aligned on a single line and, subsequently, the discs with the thus aligned symbols are made to turn together to expose them behind the associated window in the speedometer dial.

The said mechanism can comprise, for example, a ratchet mechanism comprising a pivoting pawl urged by a spring towards the spindle, and an axial groove formed on the spindle itself; a tooth is formed on the free end of this pawl which can be located in the groove to transmit the movement of the spindle to the disc when the spindle turns in a predetermined direction with respect to the disc, whilst when the spindle turns in the opposite direction from that previously mentioned the pawl disengages from the groove and allows free rotation of the disc with respect to the spindle.

Devices are known for zeroing the numerical indication given by the odometer cylinder of a speedometer in which the drive for the rotation of the said spindle used in the manner described above for zeroing the numerical indication given by the various discs, is imparted by means of a rack and pinion gear the pinion of which is rigidly connected to the said spindle and the rack of which, which meshes with the pinion, is axially movable and has an end which projects from the speedometer dial; by acting manually on this end an axial displacement is imparted to the rack to make the pinion turn and therefore turn the spindle to which it is connected.

The return movement of the rack, necessary to return it to the initial axial position for the purpose of allowing a subsequent zeroing operation, is achieved by means of a biasing spring. Zeroing devices of the type described have various disadvantages.

First of all, for manual operation of the rack in the said working stroke, it is necessary for the operator to apply a significant axial force since the reaction force of the of the said spring has to be overcome, which force must be greater than the tangntial force which must be applied to the said pinion to make the spindle rotate with respect to the associated discs; since, during such rotation the tang'ential frictional forces between the spindle and the discs are not insignificant, above all because of the large number of points of sliding contact, the said reaction force of the spring must be rather high.

Moreover, during the relative rotation of the spindle with respect to the discs which takes place during the said return stroke of the rack, the alignment of the zeros of the various discs can become slightly altered from the alignment which they had achieved at the end of the working stroke of the rack effected by the previous opposite axial displacement thereof; in fact, the said tangential frictional forces between the spindle and discs can cause small rotations of discs even if these are usually held stationary in the symbol exposure positions by suitable resilient means.

The object of the present invention is that of providing a zeroing device for zeroing the numerical indication given by an odometer cylinder of a speedometer, which will be free from the disadvantages discussed above.

According to the invention there is provided a device for zeroing the numerical indication given by an odometer cylinder of a speedometer, the said cylinder comprising a plurality of coaxial discs disposed adjacent one another and having symbols formed on their outer surfaces, and which are rotatable on a spindle by the action of transmission means operable to cause each disc to turn through a predetermined angle when one of the contiguous discs has performed a complete revolution, there being interposed, between each said disc and the said spindle a mechanism operable to transmit the movement of the said spindle to the said disc only when the spindle assumes a predetermined angular position with respect to the disc upon rotation of the spindle in a predetermined directional sense with respect to the disc, in such a way as to substantially align the same symbols of the said discs on a single line, the said rotation of the said spindle with respect to the said discs being controlled by means of a rack and pinion assembly actuated by manual axial displacement of the said rack, characterised by the fact that between one element of the said rack and pinion assembly and the said spindle there is interposed a clutch operable to transmit the movement of the said rack to the said spindle when the rack is displaced axially in a first directional sense to effect the said rotation of the said spindle and not to transmit the movement from the said rack to the said spindle when the rack is displaced axially in a second directional sense opposite to the first.

For a better understanding of the device of the present invention a detailed description of it will now be given, by way of example, with reference to the attached drawings, in which: - Figure 1 is a perspective view from the front of a speedometer provided with a zeroing device according to the invention; - Figure 2 is a longitudinal section through the speedometer taken through the zeroing device of the invention; - Figures 3 and 4 are sections of the device taken on the lines Ill-Ill and IV--IV of Figure 4; - Figure 5 is a side view of the device; and - Figure 6 is a section through the odometer cylinder of the speedometer taken on the line VI--VI of Figure 3 to show the ratchet mechanism for driving the discs of the odometer cylinder upon rotation of the spindle of the cylinder.

With reference to the drawings, a speedometer, generally indicated with the reference numeral 1, includes an odometer cylinder 2 provided with a plurality of discs 3 disposed alongside one another, having symbols on the outer surface 4, and being rotatable on a spindle 5 under the action of transmission means of known type (not illustrated) operable to make each of the discs turn through a predetermined angle when one of the contiguous discs has performed a complete revolution, for the purpose of giving a numerical indication of the distance travelled by the vehicle; the drive for such rotation of the discs 3 is provided through the toothed pinion 6 which forms part of the said transmission means.

As can be seen from the section of Figure 6, each of the discs 3 is mounted freely rotatably on the associated spindle 5 and between each disc and the spindle there is interposed a ratchet mechanism generally indicated 10, also of known type, which includes a pivoted pawl 11 thrust by a spring 12 towards the spindle 5 and one end 13 of which can be introduced into an axial groove 14 in the spindle for the purpose of transmitting rotation from the spindle to the associated disc; in the configuration of Figure 6 this end 13 has just been inserted in the associated groove 14. When the ends 13 of the previous discs 3 are inserted in the groove 14 the same symbols carried on the outer surfaces of these discs are aligned.

A further pivoted pawl 1 5 is urged by the action of the spring 12 towards the inner surface of the associated disc, and its end 1 6 can be introduced into a corresponding recess 1 7 formed in the surface itself for the purpose of maintaining a predetermined angular position reached by the disc itself and thus correctly to expose the associated numerical indication behind the display window 18 (Figure 1 ) of the dial 19 of the speedometer.

The zeroing device of the invention includes a rack and pinion device comprising a pinion 20 (Figure 2) and a rack 21, the pinion 20 of which is rigidly connected to the spindle 5 and the rack 21 of which is slidable in a suitable seat in a sleeve 22 which forms part of a casing 23 fixed to the housing 24 of the speedometer. The rack 21 meshes with a further pinion 25 freely rotatable on a pin 26 (Figure 4) of the casing 23 and this latter pinion meshes in turn with the pinion 20.

The rack 21 could however be coupled directly to the pinion 20 without the necessity of interposing the further pinion 25 between these two elements; the utilisation of this further pinion, as shown in the embodiment illustrated in the drawings, can be preferable in order to be able to make the shaft 5 rotate in an anti-clockwise direction as viewed in Figure 2 when the rack 21 is displaced towards the right in Figure 2 and therefore towards the speedometer. This rotational movement of the spindle 5 and displacement of the rack 21 allows the device of the invention to be disposed on the left hand side of the speedometer (Figure 1) and beneath the spindle 5.

The sleeve 22 of the casing 23 is provided with a slot (not visible in the drawings) through which a projection 27 of the rack 21 extends, and between this and a further projection 28 of the casing there is located a spring 29 operable to hold the rack 21 in its rest position illustrated in the drawings.

Between the pinion 20 and the spindle 5 there is located a clutch, generally indicated 30, which is operable to transmit movement from the pinion to the spindle when the rack 21 is displaced axially towards the speedometer, and not to transmit movement from the pinion to the spindle when the rack is displaced in the opposite direction under the action of the spring 29.

The clutch 30 is conveniently a dog tooth clutch and includes a bush 31 keyed onto one end 32 of the spindle 5 and turnable with the spindle itself, for example by inserting a small tooth formed in the axial bore of this bush into the groove 14 of the spindle; on the front face of this bush, facing towards the pinion 20, there is formed a first clutch tooth 33, (Figure 3). The clutch further includes a second clutch tooth 34 formed on the face of the clutch 20 which faces towards the bush 31, as is clearly seen in Figure 3 and Figure 4. Conveniently, each of the said teeth is obtained by delimiting both the pinion and the bush with a helical front surface.

The pinion 20 is freely rotatably mounted on the end 32 of the spindle 5 and is urged towards the bush 31 by the action of a helical spring 35.

The operation of the zeroing device described above is as follows.

When a predetermined numerical indication has been reached on the odometer cylinder of the speedometer each of the discs 3 is turned on the associated spindle 5 (Figure 6) to a predetermined angular position with respect to this latter; in this configuration (unless the numerical indication given by a disc 3 is zero) the relative angular position between the disc and the spindle is different from that illustrated in Figure 6, and therefore the end 1 3 of the pawl 11 is outside the groove 14.

To zero the odometer cylinder the rod 36 rigidly connected to the rack 21 is pushed towards the speedometer thereby causing the rotation of the pinion 20 in an anti-clockwise sense as viewed in Figure 2; in this sense of rotation the clutch 30 is engaged since the two clutch teeth 33 and 34 are held in contact and the movement is transmitted to the spindle 5. During the rotation of the spindle 5 the ends 1 3 of the pawls 11 engage into the groove 14 causing alignment of all the numbers carried on the surfaces of the discs 3; by continuing the rotation all the discs are made to turn together with the spindle until the line of zeros is exposed through the window 1 8 of the dial 19.

At this point the rod 36 is released and the rack 21 is returned by the spring 29. During this movement the pinion 20 is caused to rotate in a clockwise sense as viewed in Figure 2, but this rotation is not transmitted from the pinion 20 to the bush 31 since in this directional sense of relative rotation the two elements of the clutch disengage (the teeth 33 and 34 become separated and are no longer in contact with one another).

It is therefore apparent that with the device of the invention the force necessary to actuate the rack 21, which is equal to the sum of the force necessary for zeroing the odometer cylinder and the force necessary to overcome the resilient reaction of the spring, can be reduced since the value of this resilient reaction can be only that necessary to overcome the friction upon displacement of the rack 21 in the associated seat of the sleeve and for rotation of the pinions 20 and 25; in the prior art devices described, on the other hand, the value of this resilient reaction had to be much higher since it had to be able to overcome not only the first mentioned friction, but also that between the spindle 5 and the discs 3 upon relative rotation between these elements.

Further, with the device of the invention the zeroing obtained at the end of the operation described is without question not changed since during the return stroke the rack 21 does not impart any rotation to the spindle 5.

In the prior art devices in which this rotation did take place, because of the tangential frictional forces between the spindle 5 and the discs 3, small turning moments were transmitted to these, which could be greater than the braking moment generated by the action of the pawls 1 5 (Figure 6) and thus an imperfect alignment of the symbols of the display could occur.

It is apparent that the embodiment of the present invention described can be modified and varied without departing from the scope of the present invention.

Claims

1. A device for zeroing the numerical indication given by an odometer cylinder of a speedometer, the said cylinder including a plurality of coaxial discs disposed adjacent one another, having symbols on the outer surfaces thereof, and being rotatable on a spindle under the action of transmission means operable to cause each said disc to rotate by a predetermined angle when one of the contiguous discs has performed a complete revolution, there being interposed between each of the said discs and the said spindle a mechanism operable to transmit movement from the said spindle to the said disc only when the spindle, turning in a predetermined directional sense with respect to the disc, has reached an angular position with respect to the disc, such as substantially to align the same symbols of the discs on a single line, the said rotation of the said spindle with respect to the disc being controlled by means of a rack and pinion assembly under the action of a manual axial displacement of the said rack, characterised by the fact that between one element of the said rack and pinion assembly and the said spindle there is located a clutch operable to transmit movement from the rack to the said spindle when the rack is displaced axially in a first directional sense to effect rotation of the said spindle with respect to the disc and not to transmit movement from the said rack to the said spindle when the rack is displaced axially in a second directional sense opposite the first.

2. A device according to Claim 1, characterised by the fact that the said clutch is a dog tooth clutch located between the said pinion and the said spindle.

3. A device according to Claim 1 or Claim 2, characterised by the fact that the said clutch includes a bush keyed onto one end of the said spindle and turnable with the spindle itself, at least a first clutch tooth being formed on a front face of the said bush, the said pinion being freely rotatably mounted on the said end of the said spindle and being provided on a front face with at least a second clutch tooth and being urged by resilient means towards the said bush, the form of the said first and second teeth being such as to transmit movement from the pinion to the bush when the pinion is turned in such a directional sense as to cause said rotation of the said spindle and to release the connection between the spindle and the bush when turned in a directional sense opposite the first.

4. A device according to any preceding Claim, characterised by the fact that between the said rack and the said pinion there is located a second pinion meshing with both.

5. A device for zeroing the numerical indication given by an odometer cylinder of a speedometer, substantially as described and illustrated in the attached drawings.