GB2151915A

GB2151915A - Linkage member of windscreen wiper drive system

Info

Publication number: GB2151915A
Application number: GB08430973A
Authority: GB
Inventors: Alfred Kohler; Hans Prohaska; Werner Wohrle
Original assignee: SWF Auto Electric GmbH
Current assignee: SWF Auto Electric GmbH
Priority date: 1983-12-29
Filing date: 1984-12-07
Publication date: 1985-07-31
Also published as: BR8406356A; DE3347441A1; IT1181927B; IT8424202A0; JPS60179360A; GB8430973D0; FR2558426A1

Abstract

A linkage member of a windscreen wiper drive system such as crank 10 comprises a metallic rod 11 provided with a plastics coating 20 for protection against corrosion, the coating having been applied by an injection moulding process. Ball pin 15 may be formed by an injection moulding technique at the same time as the coating is produced. In modifications, a bearing sleeve (32, Figures) or ball socket (43, Figure 7) may also be formed by injection moulding at the opposite end of the crank to the end on which the ball pin is formed. <IMAGE>

Description

SPECIFICATION Gearing member for a windscreen wiper system on motor vehicles This invention relates to a gearing member, for a windscreen wiper system on motor vehicles, comprising a metallic rod coated with an anti-corrosive layer which layer, in comparison with the rod substance, is relatively thin, and elements for fastening and/or articulating a drive member and a driven member.

The gearing members of a windscreen wiper system, such as cranks and push rods, have to transmit relatively high forces and, on grounds of stability, are therefore mostly pressed from a metal blank. Because, owing to their position in a motor vehicle, they are exposed to heavy atmospheric influence, these metallic rods have to be coated with an anti-corrosive layer. Until now these rods have mostly been zinc coated (galvanised). The rods of wiper systems which are visible on the motor vehicle are mostly lacquered black. However this anticorrosive layer does not in any case meet the re quirements with regard to corrosion resistance which have risen recently. Moreover lacquering of such rods is relatively time consuming and expensive.Due to the fact that after lacquering elements for fastening and/or articulating a drive member and/or a driven member have to be fixed it is not completely impossible that this anti-corrosive layer is damaged during the mounting process. This is particularly the case if a metallic ball pin or a wiper shaft is to be riveted in a bore of a crank. The coat of lacquer could, however, also be damaged when a push rod is inserted in an injection mould for injection moulding a ball socket thereon.

The present invention is based on the problem of developing gearing members of this kind in such a way that they can be produced more eco nomically and meet increased requirements with regard to anti-corrosive properties.

According to the present invention there is provided a gearing member, for a windscreen wiper system on motor vehicles, comprising a metallic rod coated with an anti-corrosive layer which layer, in comparison with the rod substance, is relatively thin, and elements for fastening and/or articulating a drive member and a driven member, character ised in that the anti-corrosive layer consists of a plastics material which is injection-moulded around the rod.

Thus the hitherto customary coat of lacquer is substituted by an anti-corrosive layer from a plastics material, which is injection-moulded on the rod, or push rod or crank.

It is true that from the German specification OS 3,045,504 a crank is known as such, of which a metallic rod is on all sides covered by a plastics mate rial, however the crank of this known embodiment is predominantly made of a plastics material and the metal part only serves to reinforce the plastics part.Thereby the thickness of the plastics layer lies in the order of magnitude of this metallic reinforcement, while in the present invention, which is based on a rod with customary thickness of material, the plastics layer has a much lower thickness than the thickness of the rodl In the present invention this plastics layer only serves as an anti-corrosive layer, while in the embodiment according to the prior art this plastics coating must have such a stability that it is capable of transmitting the forces coming into existence in connection with the metallic insert.

Due to the fact that in order to be injectionmoulded around the rod has to be inserted in an injection mould, in order to reduce the costs further it is suggested according to an advantageous embodiment of the invention to injection-mould at least one element as a single piece with this anticorrosive layer on the rod, which element serves to fasten and a drive member and a driven member.

This can for example be a ball pin. As far as an embodiment of this kind is concerned it is a particular problem to chose the material. The material must have a good flowability so that, also with regard to longer rods, the thickness of the anti-corrosive layer can be made small. Because the ball pin consists of the same material it must also have satisfactory bearing properties. This means that the material must have a high stability, a good scuff resistance and very good gliding properties. It must be capable of co-operating with the material of the counterbearing. Of course the material must also be resistant to chemical substances and to grease, because the ball pin engaged in a ball socket is greased in most cases. Owing to all of these requirements most of the plastics materials usual in trade can be disregarded.It has been found by comprehensive experiments that optimal results can be achieved, if the anti-corrosive layer is made from a polyamide 66 with 30 per cent glass fibres and 15 per cent polytetrafluoroethylene.

Another production problem of such gearing members is that the rod has to be secured in an injection mould in such a way that there is on all sides a small spacing from the mould, which spacing has to be as uniform as possible. The longer the rod to be injection moulded around, the more difficult it is to solve this problem, because due to the necessary high injection moulding pressures deformations cannot be totally excluded. A first solution to this problem is that the rod is secured in the mould only in such points, in which later for example a ball pin or a ball socket is injectionmoulded on it. By this ball socket or ball pin areas of the rod are covered which originally were not covered because of mould parts resting against them.

If the same material is used for the anti-corrosive layer and the ball pin a satisfactory stability can also be achieved in the case of this embodiment.

However, the anti-corrosive layer of a particularly preferred embodiment is to be made of a material having a good flowability and a favourable price, while a plastics material of higher cost with good bearing properties is chosen for the ball pin or the ball socket. Then the difficulty appears that, for instance, the ball socket does not stick with the nec essary firmness on the rod entirely coated with an anti-corrosive layer. This disadvantage can however be cured, if by a suitable shape of the mould it is achieved that the anti-corrosive layer covers only part of the rod and the other areas of the rod are directly covered by the plastics material for the ball socket, for example. Thus the plastics material of higher cost sticks directly to the metallic rod.

Another solution to the problem of securing the rod in an injection mould is at first to injectionmould the elements for fastening and articulating of a drive member and a driven member on the rod and makes use of these elements to secure the rod in the injection-mould later on, where the anticorrosive layer is coated on the rod.

The problems of securing the rod in the injection mould in the right position are of smaller importance, if, for example, a wiper shaft is fastened on this rod, which wiper shaft has been coated with an anti-corrosive layer. In this case the wiper shaft can be used to secure the rod in the injection mould in a proper position.

The rod of all of these alternative examples can be additionally secured through small spacers of a non corrosive material which adhere to the rod after the injection-moulding process. These spacers determine the thickness of the anti-corrosive layer which, as a matter of fact, is also constant over the entire length of longer push rods.

Because ball pins injection-moulded on a crank usually engage in a ball socket on the push rod, there exists a possibility to secure the crank in the area of this ball pin in the mould by holding pins.

The portions, which are not covered with the anticorrosive layer if required, are in this case sufficiently protected against atmospheric influences by the ball socket when the push rod is mounted.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a section through a crank on an enlarged scale, Figure 2 is a lateral view of another crank, Figure 3 is a view in the direction of arrow A of Figure 2, Figure 4 is a view in the direction of arrow B of Figure 3, Figure 5 is a section through a further embodiment of a crank, Figure 6 is a view of two push rods and Figure 7 is a section through a push rod in the area of the ball socket on an enlarged scale.

Figure 1 shows a crank 10, which has a rod 11 having an end portion 14 bent at right angles. This rod is pressed from a metal blank having a thickness of, for example, 5mm. A wiper shaft 13 is pressed into an aperture 12 in a manner protected against twisting. On its other end the rod 11 has the perpendicular portion 14 which serves to stiffen a ball pin 15 injection-moulded thereon.

Cranks with such a basic construction are known.

In windscreen wiper systems they serve, for exampie, to drive a wiper arm which is fastened on the wiper shaft, whereby a drive element in the shape of a push rod acts upon the ball pin. Thus the ball pin 15 of this example has to be seen as an element for articulating a drive member and the wiper shaft as an element for fastening a driven member.

It is significant for the present invention that the rod 11 is coated with an anti-corrosive layer 20 of a plastics material. In the embodiment according to Figure 1 the plastics material is injection-moulded around the rod and the ball pin 15 is injectionmoulded on it at the same time. The thickness of the anti corrosive layer 20 is about lmm or less and is thus substantially smaller than the thickness of the rod 11. In this case a polyamide 66 with 30 per cent glass fibres and 15 per cent polytetrafluoroethylene serves as the plastics material. This plastics material has a sufficient flowability and the necessary bearing properties.

This gearing member is manufactured as described below.

After the rod has been pressed the wiper shaft 13 is fixed and this structural unit is then secured in an injection mould. Here it can be ensured solely by an appropriate shape of the injection moulds by means of bore sections for the wiper shaft 13 that the rod 11 has on all sides a uniform spacing from the injection moulds. In particular if the anti-corrosive layer has to be thin it seems to be suitable to secure the rod 11 also in the other end of the injection mould. For this purpose the perpendicular portion 14 is provided with a bore 21 into which a mould holding pin 22 can be inserted.

The structural unit of rod 11 and wiper blade 13 secured in proper position in the injection mould in this manner is now injection-moulded around with a suitable plastics material, whereby at the same time the anti-corrosive layer and as a single piece with it the ball pin 15 is formed. Furthermore it can be seen in Figure 1 that the anti-corrosive layer 20 covers also the wiper shaft partially, at least in the area of its supporting flanges. The thickness could, of course, be also increased in this area, so that an additional holding function for the connection between wiper shaft and rod 11 is achieved by the plastics material.

When the plastics material is cooled, the structural unit is removed from the mould and can be directly processed thereafter. A recess 23 has been created by the mould holding pin 22, so that the rod 11 in this area is at first not protected against corrosion. When this gearing member is mounted the gearing 23 is however covered by a ball socket, as it is shown for example in Figure 7. Figures 2 to 4 show views on another crank which has two ball pins 15a and 15b which are anchored on associated portions 14a and 14b which are bent from the rod 11 on opposite sides. Also in this case the anticorrosive layer 20 and the ball pins 15 are injection-moulded from the same material as a single piece. However in contrast to the example of Figure 1 holding pins 22a and 22b act upon the front faces 24a and 24b of the perpendicular portions 14.

The recesses 23a and 23b in the ball pins 15a and 15b are therefore located in an area which is not loaded, when the forces from the push rod or from the ball socket on the push rod are transmitted.

However with regard to Figure lit has to be added that also in this case the recess 23 hardly affects the transmission of force disadvantageously, because in the longitudinal direction of the crank no high forces appear. The recess 23 is utilised as a grease chamber later.

Figure 5 shows an example, in which the fastening member 30 of a wiper arm is not anchored on a wiper shaft, but directly on the crank 10 via a holding screw 31. In this example the wiper shaft is replaced by a bearing sleeve 32, which is injection-moulded on the rod 11 as a single piece with the anti-corrosive layer 20 and the ball pin 15. In this bearing sleeve 31 is inserted a stud bolt, which is fastened on the motor vehicle body. The holding screw 31 is screwed into a bore 33 which is concentric relative to the bearing sleeve 32. In order to fix the fastening member on the crank in a manner protected against twisting teeth can be provided at the lower front face of the fastening member, which teeth engage in the anti-corrosive layer 20.

Furthermore a partially circumferential collar 34 can be moulded thereon, which encompasses the fastening member 30 laterally. Figures 6 and 7 relate to a push rod of a windscreen wiper system. It is intended to illustrate by means of Figure 6 that several push rods 40 are pressed as a single piece from a blank at first, whereby two each of the push rods are interconnected by a narrow separating web 41. Before being separated these push rods can be coated with an anti-corrosive layer 20 in a multiple mould. Thereby these rods are held in the injection mould in the area of the receiving bore 42 for a ball socket 43 each. The ball socket 43 is injection-moulded onto the rod 40 in a separate injection-moulding operation.

In Figure 7 can be seen that the anti-corrosive layer 20 only covers partial areas of the push rod 40.

In particular the area in which the ball socket is fixed later must not be covered by the anti-corrosive layer 20, because if so the ball socket 43 could not be secured sufficiently stably.

In this embodiment the element for fastening and/or articulating a drive member and/or a driven member, which in the present case is the ball socket 43, is made from a plastics material which is different from that of the anti-corrosive layer 20.

A polyamide 12 with 30 per cent glass fibres and an admixed lubricant is preferably used.

Furthermore small spacers 45 are indicated in Figure 7 which consist of an anti-corrosive material and are secured in the injection mould. After the rod has been injection-moulded around these spacers 45 stick to the anti-corrosive layer 20. In particular these spacers are suitably employed in the case of long push rods, because otherwise, due to unavoidable tolerances, it could not be ensured that the spacing of the rod from the injection mould is the same on all sides. Moreover it is essential in the example of Figure 7 that the end areas of the separating webs 41 are covered by a stud 46 on the ball socket 43.

In the embodiment according to Figure 7 thus two injection-moulding operations are to be carried out, one after the other. At first the anti-corrosive layer 20 is coated and thereafter the ball socket is moulded on. Of course the two ball sockets on a push rod 40 will be injection-moulded simultaneously. The material of the anti-corrosive layer could also be used as the ball socket material, if it has satisfactory bearing properties. However in most cases a less expensive material will be used for the anti-corrosive layer 20.

The two separate operations of injection-moulding around and injection-moulding on the rod could also be carried out in the opposite order. So one could at first injection-mould matching ball sockets in the receiving bore 42 and then the entire structural unit could be supported in an injection mould by these ball sockets in such a way that on all sides a uniform spacing is ensured between the injection mould and the hitherto free part of the rod. Thereby the anti corrosive layer could also cover the ball socket partially.

Finally it is pointed out that in the embodiment according to Figure 5 also a wiper shaft could be injection-moulded thereon instead of a bearing sleeve, insofar as the plastics material used is capable of transmitting the high torques. Thus in this case only the rod would be inserted in the injection mould and simultaneously or in successive injection-moulding operations the anti-corrosive layer, a ball socket or a ball pin and a wiper shaft are injection-moulded on it.

On the whole gearing members for windscreen wiper systems can be produced in this manner at favourable costs. The anti-corrosion property necessary is ensured even under most unfavourable circumstances.

Claims

1. A gearing member, for a windscreen wiper system on motor vehicles, comprising a metallic rod coated with an anti-corrosive layer which layer, in comparison with the rod substance, is relatively thin, and elements for fastening and/or articulating a drive member and a driven member, characterised in that the anti-corrosive layer (20) consists of a plastics material which is injection-moulded around the rod (11).

2. A gearing member according to claim 1, characterised in that the anti-corrosive layer consists of a polyamide 66 with 30 per cent glass fibres and 15 per cent polytetrafluoro ethylene.

3. A gearing member according to claim 1 or claim 2, characterised in that at least one element (ball pin 15) for fastening and/or articulating a drive member and/or a driven member is as a single piece injection-moulded on the rod (11) with the anti-corrosive layer (20).

4. A gearing member according to claim 1 or claim 2, characterised in that at least one element (ball socket 43) for fastening and/or articulating a drive member and/or a driven member is injectionmoulded on the rod (11) which is previously coated with an anti corrosive layer (20).

5. A gearing member according to claim 4, characterised in that the anti-corrosive layer (20) covers only partial areas of the rod (11) and the other areas of the rod (11) are covered when the element (ball pin 43) is injection-moulded on it.

6. A gearing member according to claim 1 or claim 2, characterised in that at least one element for fastening and/or articulating a drive member and/or a driven member are injection-moulded on the rod, and the rod (11),and if required, partial areas of the said element, are coated with the anticorrosive layer thereafter.

7. A gearing member according to any one of claims 4 to 6, characterised in that the element for fastening and/or articulating a drive member and/ or a driven member consists of the same plastics material as the anti-corrosive layer (20).

8. A gearing member according to any one of claims 4 to 6, characterised in that the element for fastening and/or articulating a drive member and/ or a driven member consists of a plastics material different from that of the anti-corrosive layer (20).

9. A gearing member according to claim 8, characterised in that the element (ball socket) is injection-moulded from a polyamide 12 with 30 per cent glass fibres and an admixed lubricant.

10. A gearing member according to any one of the preceding claims, characterised in that an element (wiper shaft 13) for fastening and/or articulating a drive member and/or a driven member consists of metal and that this metal part is fixed on the rod (11) before the rod (11) is injectionmoulded around with an anti-corrosive layer (20).

11. A gearing member according to claim 10, characterised in that the anti-corrosive layer (20) covers the metallic element (wiper shaft 13) at least in sections.

12. A gearing member according to claim 11, characterised in that the area of the anti-corrosive layer (20) covering the metallic element is reinforced and contributes to fix this element on the rod (11).

13. A gearing member according to any one of the preceding claims, characterised in that for said injection moulding the rod (11) is secured in an injection mould by small spacers (45) of an anti-corrosive material which determine the thickness of the anti-corrosive layer (20).

14. A gearing member according to any one of the preceding claims, characterised in that the metallic rod (11) is part of a crank, which has at least one perpendicular portion (14), and that the element for articulating a drive member and/or a driven member is a ball pin (15), into which this perpendicular portion (14) projects approximately centrally.

15. A gearing member according to claim 14, characterised in that a partial area of this perpendicular portion (14) serves as a supporting surface for a tool holding pin (22) during said injection moulding.

16. A gearing member according to claim 15, characterised in that this perpendicular portion (14) has a bore (21) for inserting a tool holding pin (22).

17. A gearing member according to claim 16, characterised in that a recess (23) formed in the ball pin (15) by the tool holding pin (22) serves as a grease chamber.

18. A gearing member according to any one of claims 14 to 17, characterised in that the other element on the crank (10) is a wiper shaft (13).

19. A gearing member according to any one of claims 14 to 17, characterised in that a cylindrical bearing sleeve (32) is injection-moulded on the crank (10).

20. A gearing member according to claim 19, characterised in that the rod (11) has a bore (33) for a holding screw (31), which bore is centrally arranged relative to the bearing sleeve (32), and through which holding screw a driven member, such as the fastening member (30) of a wiper arm, can be clamped on the crank (10).

21. A gearing member according to any one of claims 1 to 13, characterised in that the metallic rod (11) is a push rod, which in the area of its ends has ball sockets (43) injection-moulded thereon.

22. A gearing member according to claim 20, characterised in that several push rods (40) are at first formed out of a blank as a single piece, whereby two each of the push rods (40) are interconnected through a narrow separating web (41), and that the end areas of the said separating webs (41) not covered with an anti corrosive layer (20) are covered by a plastics material when the ball sockets (42) are injection-moulded thereon.

23. A gearing member, for a windscreen wiper system on motor vehicles, substantially as herein described with reference to and as illustrated in Figure 1, Figures 2 to 4, Figure 5 or Figures 6 and 7, of the accompanying drawings.