GB2331349A

GB2331349A - Gear-wheel for tachograph housing backlash reducing slip spring held by cover plate

Info

Publication number: GB2331349A
Application number: GB9818876A
Authority: GB
Inventors: Benjamin Saeger
Original assignee: Mannesmann VDO AG
Current assignee: Mannesmann VDO AG
Priority date: 1997-08-30
Filing date: 1998-08-28
Publication date: 1999-05-19
Anticipated expiration: 2018-08-28
Also published as: GB2331349B; DE29715630U1; JPH11144107A; GB9818876D0

Abstract

An injection moulded gearwheel 1 provides a spring barrel 4 for accommodating a slip spring 15 used to compensate for tooth play in the driving gear of a tachograph. A cover plate 16 is provided to prevent axial escape of the slip spring 15 from the spring barrel 4. The cover plate 16 is fastened by resilient catch hooks 7, 9 moulded on a base 2 of the component 4 around a band 5 providing a pocket and sliding surface 6 for the spring 15. Preferably a washer is used as the cover plate 16.

Description

1 2331349 Component with a spring barrel for a slip spring used to

compensate for tooth play in the running gear of a tachograph The invention relates to a component providing a spring barrel for accommodating a slip spring serving to compensate for tooth play in the running gear of a tachograph.

It is known that the intermeshing gear-wheels of such running gear should be provided with a certain degree of play to permit disturbance- free rolling of the co-operating tooth flanks. Due to the large number of cooperating gear-wheels normally used, this play adds up to an idling rotational angle which cannot be neglected. Such play can also cause unacceptable noise due to resonance with a stepping motor drive. The usual practice is to provide an energy store in the form of a slip spring arrangement which compensates for the play by acting against the drive of the running gear.

The slip spring is usually a spiral spring, which has its internal end fixed, preferably on an axle of the running gear, and with its outer end resting on the cylindrical internal wa'Ll of a socket or pot-shaped spring barrel. The spring barrel is generally arranged on a gear-wheel which is mounted on this axle and engaged with a gear-wheel of the running gear, preferably with the last gear-wheel in the drive train. A gear-wheel with a spring barrel of this type is generally produced from injection moulded plastics material. The sliding face associated with the outer end of the slip spring is not cylindrical but slightly conical due to the demoulding bevel. This means there is a risk that the outer end of the s-,)ring will run out of the spring barrel. Potentially the slip spring will spring open or the outer end will cut into a cover plate of the running gear covering the spring barrel thus impairing operation. This would be of particular concern if the plate is 2 produced from plastics material. The running gear which is arranged, for example, in the base of a tachograph drawer is extremely flat in construction. This flat construction can also cause the outer end of the spring to run out of the spring barrel. The axles for the gearwheels of the running gear are moulded on the drawer base with a relatively thin cover sheet being provided to secure the gear wheels axially. In this case, manufacturing tolerances and bending or distortion of the cover sheet can allow the slip spring to break out of the barrel.

It is an object of the invention to provide an improved construction which will prevent the sli-p spring from running out of the spring barrel with minimum expenditure while maintaining a form which is as flat as possible.

According to the invention there is provided a moulded component providing a spring barrel for a slip spring serving to compensate tooth play in the running gear of a tachograph, said component comprising a base, a set of driving teeth and a concentric sliding face associated with the outer end of the slip spring, wherein a circular band whose interior forms the sliding face of the barrel is formed on the base and resilient catch hooks extending in the direction of the band are also formed on the base in such a way that a cover plate c-an be fastened on the end face of the band to secure the sli-P spring in the barrel.

The component may have the drive teeth in the form of a ring gear surrounding the component and a central hub for fitting on a bearing journal or axle. The component may have the base, the band, the catch hooks and the hub provided substantially within a space determined by the axial dimension of the ring gear.

In a preferred embodiment a simple washer is used as the cover plate.

3 The decisive advantage of the invention is that it allows a constructional unit to be created with very low expenditure for production and assembly, in which the slip spring is already prevented from breaking out. This constructional unit can be handled and stored in pre-assembled form without the need for special care and can also be supplied, for example, mechanically to a running gear assembly room. The low expenditure is due to the fact that the catch hooks for fastening the cover plate are injection moulded on the component or gear-wheel and a conventional commercial washer which is fitted by catching with the gear- wheel can be used as cover plate.

An embodiment of the invention will now be described in more detail hereinafter, by way of example only, with reference to the accompanying drawings, wherein:

Figure 1 is a plan view of a gear-wheel component provided with a spring barrel constructed in accordance with the invention; Figure 2 is a section of the gear-wheel along the section line A in Figure 1; Figure 3 is an enlarged sectional view of the detail Z in Figure 2; Figure 4 is a section through the fitted spring barrel and Figure 5 is a sectional view of the bearing position of the gear-wheel on the base of a tachograph drawer.

The plan view and the section in Fig. 1 and Fig. 2 show an integrally moulded gear-wheel 1 which comprises a base 2 and a ring gear 3 moulded on the outside of a peripheral wall. Also on the base 2 there is a circular band 5 extending in the same 4 direction as the peripheral wall with the ring gear 3. The band 5 forms a spring barrel 4. Reference numeral 6 designates an internal face in the barrel 4 representing the sliding face for a slip spring 15 (Figures 4 and 5). it can also be seen that radially resilient catch hooks 7, 8, 9 partly surround the band 5 and extend in the direction of the band 5. Reference numeral 10 designates the hub of the gear-wheel 1 which is provided with a bearing bore 11 and corresponds at least to the width of the ring gear 3 in order to achieve a bearing which is as long as possible. A running band 12 is provided on the opposite side of the base 2. An orifice 13 in the base 2 is used for observing the position of the inner end 14 of the slip spring 15 inserted in the spring barrel 4 (see Figure 4) The interior of the spring barrel 4, not designated in detail, is axially covered by an annular cover plate 16 at least sufficiently to prevent axial travel of the slip spring 15. A conventional commercial washer which is fitted by catching with the catch hooks 7, 8, 9 can advantageously be used as cover plate 16.

Fig. 5 shows that a bearing journal 18 associated with the gearwheel 1 and a collar 19 surrounding it are moulded on the base 17 of a drawer carrying t-he running gear, for example of a tachograph. A slot 20 formed in the collar 19 is used for fixing the angled inner end of the slip spring 15. Reference numeral 21 designates an annular depression which is provided as a bay for the cover plate 16 and the peripheral catch hooks 7, 8, 9.

It can be seen from the partial view of the gear-wheel 1 in Fig. 5 that the hub 10 engages in the annular gap 22 between the bearing journal 18 and the collar 19 and the gear-wheel 1 is supported on the end face 23 of the collar 19. Reference numeral 24 designates a cover sheet which is associated with the running gear as common axial security, rests on ribs 25 moulded on the base 17 and is suitably fastened on the drawer.

Claims

1. A component (1) providing a spring barrel for a slip spring serving to compensate tooth play in the running gear of a tachograph with said component comprising a base (2), a set of driving teeth (3) and a concentric sliding face (6) associated with the outer end of the slip spring, wherein a circular band (5) whose interior forms the sliding face (6) of the barrel is formed on the base (2), and catch hooks (7, 8, 9) extending in the direction of the band (5) are formed on the base (2) in such a way that a cover plate (16) can be fastened on the end face of the band (5) to secure the slip spring (15) in the barrel.

2. A component according to claim 1, wherein the component has a hub (10) for location on a journal or axle, the set of teeth take the form of an external ring gear (3) and the base (2), the band (5), the catch hooks (7, 8, 9) and the hub (10) are provided substantially within a space determined by the axial dimension of the ring gear (3).

3. A component according to claim 1 or 2, wherein a washer is used as the cover plate (16).

4. A component according to any one of claims 1 to 3 and produced by injection moulding.

5. A component substantially as described with reference to, and as illustrated in, Figures 1 to 2 of the accompanying drawings.

6. A component according to any one or more of the preceding claims when fitted in the running gear of a tachograph.

6

7. A tachograph drawer carrying running gear and incorporating a comnonent according to any one of claims 1 to 5.

8. A tachograph drawer and running gear substantially as described with reference to, and as illustrated in, Figures 4 and 5 of the accompanying drawings.