GB2089927A - Device for converting rotary motion into reciprocating motion for driving vehicle headlamp wipers - Google Patents

Abstract

A device for converting rotary motion into linear motion, comprising a sprocket 2 mounted on a rotatable drive shaft 4, an endless chain 1 mounted on sprocket 2 and extending over a second, idler sprocket 3 or a tracking plate, one of the outer link plates of the chain comprising a link plate 7 which extends across the centre line of the sprockets 2,3 and an elongate member 9 pivotally secured to the link plate 7 and pivotable about an axis located on said centre line. Rotation of the drive shaft 4 will cause the sprocket 2 to rotate to drive the chain 1 and movement of the chain 1 will cause the elongate member 9 to reciprocate in accordance with movement of the link plate 7 along the chain path. The device is particularly intended for cleaning vehicle head lamps 22 and in that application the elongate member 9 carries a wiper-blade 20. <IMAGE>

Description

SPECIFICATION Device for converting rotary motion into reciprocating motion This invention relates to devices for converting rotary motion into reciprocating motion. The invention is primarily but not exclusively directed to devices for cleaning surfaces and is particularly concerned with devices for cleaning vehicle headlamps.

The cleaning of vehicle headlamps is executed, currently, by various methods one of which utilises the reciprocating-arc motion of a wiper-blade which is pivoted at one of its extremities, such pivot being driven via a spindle which reverses the direction of rotation at each limit of the predetermined arc. The system may be supplemented with a method of pumping a jet of water, or other liquid, onto the lens surface, to assist the cleaning action. This type of device requires an individual motor and associated accessories for each wiper and is, thereby, relatively expensive. The arcing motion leaves the unswept areas, outside the swept area, untouched, the saturated dirt from such areas flowing downwards across the cleaned area thus requiring subsequent wiping to achieve a reasonable degree of clarity.The wiper-blades and pivots remain fully exposed in both the operating and the idle positions and are highly vulnerable to damage by random objects and by malicious vandalism.

An altemative method of cleaning headlamps is to provide powerful jets of water or other suitable liquid, which impinge upon the surface of the lens with sufficient energy to disperse the dirt. This system demands considerable quantities of liquid to be carried in a reservoir, such liquid requiring a proportionately high quantity of inhibitor to assure functioning in sub-zero temperatures. The cost of this system is high and the jet-nozzle assemblies, being permanently exposed, are extremely vulnerable to misalignment and damage by random objects and by vandalism. The slightest misalignment negates efficiency.

A further system proposes the use of linearstroke wiper-blades operated from a rotating arm or cam, such arm or cam requiring a diametrical sweep in excess of the length of stroke required. A nine-inch stroke, for instance, could be generated only from the arm or cam occupying a sweeping diameter of some ten inches, unless further complicated linkages are introduced. In any event, this mechanism is of excessive bulk and proportionate instability.

The present invention aims to provide a device which provides a horizontal or vertical reciprocating stroke of any predetermined length and which eliminates the need for a bulky and unstable rotating arm or cam.

A further aim of the invention is to provide a device in which the wiper-blades can be stowed away unexposed when not required for use.

According to one aspect of the invention, there is provided a device for cleaning vehicle headlamps, which device comprises a sprocket adapted to be mounted on a rotary drive shaft, an endless chain mounted on the sprocket and extending over a second, idler sprocket or a tracking plate, one of the outer link plates of the chain comprising a link plate having an extension which extends across the centre line of the sprockets or sprocket and tracking plate, an elongate member pivotally secured to the said link plate extension and pivotable about an axis located on the said centre line and a wiper-blade connected to the elongate member.

The device may further include a mechanism for operating a pump for directing a spray of water or other cleaning liquid at the lens of a headlamp to be cleaned.

Preferably, means are provided for cleaning both the left-hand and right-hand headlamp or sets of headlamps of a motor vehicle simultaneously from a single drive source.

Another aspect of the invention provides a device for converting rotary motion into linear motion, said device comprising a sprocket adapted to be mounted on a rotary drive shaft, an endless chain mounted on said sprocket and extending over a second, idler sprocket or a tracking plate, one of the outer link plates of the chain comprising a link plate which extends across the centre line of the sprockets or the sprocket and tracking plate, and an elongate member pivotally secured to said link plate and pivotable about an axis located on said centre line, the arrangement being such that rotation of the drive shaft will cause the sprocket to rotate to drive the chain and movement of the chain will cause the elongate member to reciprocate in accordance with rnovement of the connected link plate along the chain path.

The invention will now be further described, by way of example, with reference to the drawings, in which: Figs. 1 and 2 show part of one embodiment of a device according to the invention illustrating the manner of operation; Fig. 3 is a side elevation of one embodiment of a wiper-blade operating mechanism according to the invention; Figs. 4 and 5 are views, corresponding to Fig. 3, but showing the mechanism in different operating positions; Fig. 6 is a side elevation of a second embodiment of a wiper-blade operating mechanism according to the invention; Fig. 7 is a cross-section through a mechanism according to the invention for operating two wiper-blades; Fig. 8 is an exploded perspective view of part of the mechanism shown in Fig. 7; Fig. 9 is a perspective view of the mechanism shown in Figs. 7 and 8 as fitted to a vehicle headlamp wiper-blade; and Fig. 10 is a perspective view of a motor car fitted with a headlamp wiper device according to the invention.

In the drawings, like parts are denoted by like reference numerals.

Reference will first be made to Figs. 1 and 2 of the drawings which show an endless chain 1 extending over a pair of sprockets 2 and 3 which are preferably made of plastics material. The sprocket 2 is mounted on a drive shaft 4 and is arranged to be driven by said shaft whereas the sprocket 3 is mounted on an idler shaft 5. When the sprocket 2 is rotated, the upper length of chain 1 travels in one direction with the lower length travelling in the opposite direction. Therefore, a given point on the chain will move the full operating distance of the two sprockets first one way and then, reversing along the full length, the opposite way. Thus, one complete reciprocation occurs during one complete revolution of the chain but this reciprocation is not true as it lies only parallel to the horizontal centre-line 6 of the assembly and not upon it.

To position the reciprocation upon the centre line, one of the chain outer-link-plates is removed and is replaced by a link plate 7 which has an extension which extends across the centre line 6 of the sprockets. A spigot 8 is provided on the extension of the link plate 7, the axis of the spigot being located on the centre line 6. Thus, true reciprocation of the spigot 8 occurs when the chain is driven.

As shown in Figs. 3 to 5, one end of an elongate member 9 in the form of a rod or tube is secured to the link plate 7 by providing said end with a bore adapted to receive the spigot 8 in a pivotal manner so that the member 9 is free to pivot with respect to the link plate 7. Fig. 3 shows that rotation of the sprocket 2 will cause the chain to move the elongate member 9 in the direction of the arrow, i.e. from right to left, until the link plate 7 reaches the sprocket 2 and begins to move around the sprocket, which position is shown in Fig. 4. After moving round the sprocket 2, the link plate 7 is effective to move the member 9 in the opposite direction as indicated by the arrow in Fig. 5, i.e. from left to right. Movement of the elongate member 9 is purely reciprocal and the velocity of motion is constant, assuming that the driven sprocket 2 is rotated at constant speed.

When the spigot 8 on the link plate 7 reaches alignment with the axis of the shaft 4 or 5, linear motion of the elongate member ceases while the link plate rotates the 1800 around the associated sprocket. This minor pause at the end of each travel is an important factor to ensure that no violent action occurs when the elongate member changes direction of travel. Thus, also, the high torque requirement at the moment of change is positive and assured.

The whole arrangement automatically embodies an integral and very convenient speed reduction. Assuming, for example, a motor speed of the order of 3,000 rpm and sprocket pitch-circle diameters of one and half inches, with the sprocket centres nine inches apart, it follows that the chain will rotate at approximately one-fifth that of the sprocket. Therefore a complete cycle of reciprocation every one-tenth of a second, without any supplementary reduction-gearing, at this stage, is involved. It is considered, however, that five reciprocations per second is desirable and this can be achieved by either lower motor speed or by suitable diameters of the driving mechanism wheels.

It will be noted that the spigot 8 of the chainlink-plate 7, and its associated bearing-bore in the elongate member 9 are subject to virtually no wear as the spigot rotates only one-half of one revolution at the end of each stroke at which point, also, no load of any description is present.

A wiper sub-assembly (not shown) is connected to the free end of the elongate member 9.

In the embodiment shown in Fig. 6, the idler sprocket 3, complete with the shaft 5 and associated bearings, is replaced by a tracking plate 11 which is preferably made of plastics material.

The width of the tracking plate is arranged to be substantially identical to the dedendum-circle diameter of the sprocket 2. The end of the plate nearest the sprocket 2 may be radiused or squared to ensure clearance for the sprocket teeth while the opposite end is radiused to conform with one half of the diameter of the sprocket dedendumcircle. Thus the rollers of the chain 1 ride along the peripheral edge of the tracking-plate 1 , the sideplates of the chain-links preventing the chain from riding off the truck provided the chain is mounted at the correct tension. For this reason, the tracking-plate 11 is made capable of horizontally linear adjustment by the provision of two elongated slots 12 through which two fixing screws 13 locate to mount the plate 1 1 on an assembly housing (not shown in Fig. 6).

The mechanisms so far described provide for only one wiper action and normally two wiper actions are required. Although it is possible to mount a second link plate on the chain at a point opposite to the link plate 7 and to mount a further elongate member on this second link plate, this arrangement is not preferred since it is then necessary to ensure that the two chain link plates do not collide at the cross-over points half way along the runs of the chain. The preferred arrangement, according to the invention, is to provide a precise duplication of the assembly shown in Figs. 3 to 5 or Fig. 6, the pairs of components being mounted in a housing asymmetrically opposite to one another, i.e. as mirrored.

Such an arrangement is shown in Figs. 7 and 8 in which two drive sprockets 2, 2' are mounted on respective shafts 4, 4' in a housing 14. Also mounted on each shaft 4, 4' is a respective gear 15, 15' which is arranged to mesh with a respective gear 16, 16'. The two gears 16, 16' are mounted on the drive shaft 17 of an electric motor 18 which shaft is mounted in bearings in the side walls of the housing 14. The gears 1 6, 1 6' preferably each comprise a bobbin-type moulded gear and the gears 15, 15' are desirably integrally moulded with the sprocket wheels 2, 2' respectively. The diameters of the bobbin-type gears 1 6, 1 6' relative to the diameter of the gears 15, 15' is such as to develop the speed reduction required to produce a desired stroke-reciprocation frequency. The gears therefore become a function of the type of motor chosen.

The housing 14 is normally closed except for slots in its end faces to allow the passage of the elongate members 9, 9' respectively mounted on the link plates 7 and 7'. The housing may be moulded from plastics material in which case the end slots may be so moulded as to provide a rubbing seal to resist the ingress of moisture. The housing may take the form of an open-topped box or suitable channel section, either type being closed with a lid or cover which may be suitably moulded to provide simplicity of fitting and to provide also protection against ingress of undesirable moisture and foreign material.

A further advantage of the sprockets 2, 2' and associated gears 15, 15', as well as the bobbintype gears 16, 16', being moulded in a lowfriction plastics material such as nylon, is that no conventional type bearings are required and therefore the spindles for the gears 1 5, 1 5' would be so formed as to fit flush with the link-plate sides of the sprocket faces, passing through the bore of the sprockets 2, 2' and the wall of the housing 14, to which they can be secured by a male section 19, 19' of the two-part shafts 4, 4'.

The same method is applicable to the spindle which carries the bobbin-type gears 1 6, 1 6', although, in this case, the motor-shaft 17 itself would satisfy the requirement.

Figs. 9 and 10 show the mechanism installed in a motor vehicle with wiper heads 20, 20' mounted respectively on the other ends of the elongate members 9, 9' via respective extension members 21, 21'. The extension members 21, 21' may be cranked or offset to suit headlamps 22 the lenses of which are located other than on the common centre-line of the mechanism.

The headlamp fairing, or bezel-frame, should be formed to provide a pocket or recess 23 in its inboard wall to accept the wiper head 20, 20' in the fully retracted position, thus providing the protection desired. Such a pocket may also be produced as a separate moulding if necessary or desired.

Electrical switching should embody circuitry to ensure that if the cleaning operation is switched to the OFF condition before a wiper head reaches the fully retracted position, current would remain in the circuit to ensure continuation of the stroke to the fully retracted position, at which point the circuit would be broken by the mechanism itself.

The speed of reciprocation should be sufficient to ensure that continuity of the light beam is obstructed to the absolute minimum by the wiper passing through it and to be sufficiently imperceptible as to create no hazard.

The linear stroking motion can be arranged to provide an adapted stroke to a diaphragm in a small cylinder, fed with water, or suitable liquid, from a reservoir, this liquid being passed, as required, through the hollow stem of the wiper head onto the lens, thereby assisting the cleaning action.

For a nine-inch stroke, it is estimated that the body of the mechanism would be in the order of eleven inches long by two inches square in section. This is not an impediment, to any critical degree, to the air-flow passing through a cooling radiator.

The normal tendency for a chain, suspended between two sprockets, to sag, is eliminated by the substitution of the tracking-plate 11 in place of the idler sprocket 3.

In the case of multiple sets of headlamps, the wiper head could be in the form of a frame carrying two wiper-blades per side, and connected to the associated elongate member 9 or 9' in such a fashion as to ensure that no part of the associated extension member 21 or 21' lies across the path of the light beam in either the operating or the idle positions. Such a frame type of wiper head may be used for a single pair of headlamp installations.

Although the invention has been described with reference to cleaning vehicle headlamps by means of horizontally reciprocating wipers, it should be noted that the invention is not so restricted and may be used, for example, for the vertical wiping of headlamps or windscreens. The invention is also applicable to other uses requiring the conversion of rotary motion into reciprocating motto,1.

Claims (8)

1. A device for converting rotary motion into linear motion, comprising a sprocket arranged to be mounted on a rotatable drive shaft, an endless chain mounted on said sprocket and extending over a second, idler sprocket or a tracking plate, one of the outer link plates of the chain comprising a link plate which extends across the centre line of the sprockets or the sprocket and tracking plate, and an elongate member pivotally secured to said link plate and pivotable about an axis located on said centre line, the arrangement being such that rotation of the drive shaft will cause the sprocket to rotate to drive the chain and movement of the chain will cause the elongate member to reciprocate in accordance with movement of the connected link plate along the chain path.

2. A device according to Claim 1 for cleaning vehicle headlamps, said elongate member carrying or connected to a wiper-blade arranged to wipe against the outer surface of the lens of the headlamp during the reciprocation of said elongate member as a result of rotation of the drive shaft.

3. A pair of devices according to Claim 1 for cleaning both near-side and off-side headlamps of a vehicle simultaneously, said devices having a common drive shaft, or individual drive shafts driven from a common drive source, and said elongate member of one device carrying or connected to a wiper-blade arranged to wipe against the outer surface of the lens of one of the headlamps during the reciprocation of said elongate member as a result of rotation of said common drive shaft, or the respective drive shaft, and said elongate member of said other device carrying or connected to a wiper blade arranged to wipe against the outer surface of the lens of the other of the headlamps during the reciprocation of said elongate member as a result of rotation of said common drive shaft, or the respective drive shaft.

4. A device according to Claim 2, or a pair of devices according to Claim 3, in which the or each elongate member carries or is connected to a plurality of wiper-blades, each said wiper-blade arranged to wipe against the outer surface of the lens of a respective headlamp of a set of headlamps of a vehicle.

5. A device according to any one of Claims 2-4 including, in association with the or each headlamp, means for ejecting a spray of water or other cleaning liquid at the lens and a pump and associated piping for supplying the water or other liquid to the spraying means.

6. A device according to any one of Claims 2-5 including an electric motor arranged to rotate the drive shaft or said pair of drive shafts.

7. A device for converting rotary motion into linear motion constructed and arranged substantially as described herein and shown in Figs. 1-5 or Fig. 6 of the drawings.

8. A device for cleaning vehicle headlamps constructed and arranged substantially as described herein and shown in Figs. 6-8 or Figs.

9 and 10 of the drawings.