PIVOT JOINT

Abstract: A pivot joint suitable for pivotally connecting two members (2,3), particularly yokes and/or levers of a windscreen wiper blade, comprises a joint body (4) of substantially channel shaped cross section having pivot means (15) in the opposite side walls of the channel for pivotal connection with the member (3) intended to lie within the channel of the joint body (4). A sprung element (10) is provided on the joint body (4) directed outwardly from the base of the channel for engagement with a cooperating device (17) on the member (2), which member (2) is intended to sit on and around more than three sides of the joint body (4), such that the joint body (4) is fixed in at least one longitudinal direction by the sprung element (10) and the cooperating device (17) on the member (2).

Description: This invention relates to a pivot joint which is particularly but not exclusively useful in the manufacture of windscreen wipers. In the manufacture of windscreen wipers, a number of pivot joints are used, particularly between the various yokes and/or levers of the windscreen wiper blade. Problems exist in the manufacture of windscreen wipers due to the necessity, very often, of pivoting metal parts together. These joints tend to be noisy and have a tendency to suffer from wear and corrosion. Various proposals have been made for overcoming these problems, for example, by the provision of plastics members between the metal parts of the joints, but these have not proved entirely satisfactory from a manufacturing standpoint although they have worked satisfactorily in use. The present invention seeks to provide a new and improved pivot joint which is relatively inexpensive to manufacture and use and which overcomes or reduces some or all of the above problems. According to a first aspect of the invention, a pivot joint comprises a joint body of substantially channel shaped cross section having pivot means in the opposite side walls of the channel for pivotal connection with one of the members to be pivoted which is intended to lie within the channel of the joint body, a sprung element directed outwardly from the base of the channel for engagement with a cooperating device on the other member to be pivoted, which other member is intended to sit on and around more than three sides of the joint body, such that the joint body is fixed in at least one longitudinal direction by the sprung element and the cooperating device on the said other member. An abutment surface may be provided on the joint body engageable with the end surface of the said other member whereby the joint body is fixed in the longitudinal direction between the sprung element and the abutment surface. According to a second aspect of the invention, a pivot joint comprises a first member which is of channel section at least at one end, a second member pivotable to said one end of the first member and adapted to sit within the channel section of the first member with clearance and a joint body of substantially channel section adapted to sit substantially within the first member and at least partially around the second member so as to separate the members, the joint body having pivot means in the opposite side walls of the channel cooperating with pivot means on the second member, a sprung element directed outwardly from the base of the channel engaging with a cooperating device on the first member and abutment means engageable with said one end of the first member such that the joint body is fixed longitudinally between the sprung element and the abutment means, the channel section of the first member being provided towards the said one end with inwardly directed lips such that the first member surrounds the joint body on more than three sides. Preferably, the inwardly directed lips of the first member define the mouth of the channel section at this point, the mouth of the channel section being at least as wide as the width of the second member whereby the second member can pass into the channel section of the first member through the mouth thereof. The sprung element of the joint body may comprise a detent carried by the end of a resilient tongue, the detent cooperating with an aperture in the base of the channel section of the first member. The pivot means on the joint body may comprise a recess which cooperates with a projection on the second member or vice versa . Alternatively, the pivot means on the joint body may comprise an aperture in the joint body through which a pivot pin passes, the pivot pin passing also through one or more apertures in the second member. In a preferred form of the invention, the first and second members comprise yokes of the blade harness of a windscreen wiper which are to be pivoted together. The invention will now be described in greater detail, by way of example, with reference to the drawings, in which:- Figure 1 is a perspective view of one form of pivot joint in accordance with the invention; Figure 2 is a perspective view of the joint body used in the pivot joint of figure 1; Figure 3 is a sectional view taken on the line III-III of figure 1; Figure 4 is a sectional view taken on the line IV-IV of figure 3; Figure 5 is a sectional view taken on the line V-V of figure 3, and Figure 6 is a sectional view similar to figure 4 but showing a variation in the pivotal connection. Referring firstly to figures 1 to 5, one form of pivot joint 1 is shown formed between two members 2 and 3, suitably a main and a secondary yoke respectively of a windscreen wiper blade harness. These yokes would normally be made of channel section metal, the secondary yoke usually being pivotally connected in its central region to one end of the main yoke. The pivot joint 1 comprises a joint body 4 of a suitably resilient plastics material. It is generally of channel section having an end portion 5 from which extend a base tongue 6 and two side tongues 7. The external dimensions of the channel formed by the tongues 6 and 7 are less than the external dimensions of the end portion 5 so that a shoulder 9 is formed at this point for a purpose to be described. The base tongue 6 is formed at its free end with a projection or detent 10 which effectively enlarges the overall dimensions of the joint body 4 at this point so that the upper surface 12 of the projection or detent 10 lies generally in the same plane as the upper surface 14 of the end portion 5. Each of the side tongues 7 is provided with an inwardly facing recess 15 of circular tapered shape. Because of the use of a suitably resilient plastics material for the joint body 4, the tongues 6 and 7 are resilient. The member 2 or main yoke has its pivot end 16 specially formed to cooperate with the joint body 4. Thus it is provided with an aperture 17 for cooperation with the projection or detent 10 on the joint body 4. The member 2 also has depending flanges 18 which are bent inwardly at their ends 19 so as to form inwardly directed lips so that, when assembled together, the member 2 extends around more than three sides of the joint body 4 but the lips do not extend further inwardly than the inner edges of the tongues 7. The member 3 or secondary yoke is provided with a pair of outwardly projecting trunnions 20 in the form of raised projections produced by forming or by half shears punched in its sidewalls during its formation. The assembly of the joint shown in figures 1 to 5 will now be described:- The member 3 or secondary yoke is first pushed up into the channel of the joint body 4 at a position in which, when fully inserted, the trunnions 20 will be aligned with the recesses 15. The maximum dimensions of the member 3 across the trunnions is greater than the interior spaces of the two tongues 7 so that, to insert the member 3, the tongues 7 are splayed apart. This may happen automatically if the trunnions 20 are of a suitable conical form. Once the trunnions 20 have reached alignment with the recesses 15, the trunnions will enter the recesses 15 allowing the tongues 7 to snap back into their original position. The joint body 4 is now pivotally secured to the member 3. In order to connect the joint body 4 together with the member 3 to the member 2 or main yoke, the member 3 is offered up to the member 2 and passes between the opposed lips 19 of the flanges 18, care being taken to ensure that the part of the member 3 carrying the joint body 4 remains away from the member 2 but with the tongues 6 and 7 of the joint body 4 directed towards the end of the member 2. It will be appreciated that while the main part of the member 3 can pass between the opposed lips 19, the joint body is too large to do this. With the appropriate part of the member 3 inside the member 2, the two members can be slid relative to each other so that the tongues 6 and 7 of the joint body 4 approach the free end of the member 2. If the projection 10 is now depressed, and this can happen automatically if the end face of the projection 10 is suitably inclined, it is possible to slide the joint body 4, together with the member 3, into the member 2. As soon as the projection 10 registers with the aperture 17 in the base of the member 2, it will snap thereinto. At this time, the shoulder 9 of the joint body 4 will be in substantial engagement with the end of the member 2. In this way, the joint body 4 will be fixed longitudinally with respect to the member 2 and will be prevented from leaving the member 2 downwardly since it cannot pass between the opposed lips 19. However the member 3 can still pivot with respect to the joint body 4, and thus with respect to the member 2 by a small angle α (figure 3) made possible by the clearance β. This angle is normally sufficient when the joint is used in a windscreen wiper blade harness. The possibility of pivotal movement is restricted by engagement between the members 2 and 3 and it is for this reason that the clearance β is left. The amount of pivotal movement available can be varied for different applications by using different sizes of clearance. While in the particular application to windscreen wipers, there is no necessity for the joint to be able to be dissassembled, nevertheless it is possible to dissassemble the above described joint as follows:- The projection 10 is depressed to bring it clear of the aperture 17, whereupon it is possible to slide the two members 2 and 3 relative to each other so as to remove the joint body 4 from the member 2. Once this has been achieved, the member 3 can readily be extracted from the member 2 through the gap between the opposed lips 19. Then the tongues 7 can be splayed apart to enable the trunnions 20 to be removed from the recesses 15 and the joint body 4 can be pulled off the member 3. Figure 6 shows a modification in which the arrangement of the trunnions 20 and the recesses 15 is replaced by a pivot pin 25 which passes both through the member 3 and the joint body 4. There is no necessity for the pin 25 to be headed since, once the joint has been assembled, the pin will be retained by the side walls of the member 2. It will be appreciated that various modifications may be made to the above described embodiments without departing from the scope of the invention. For example, the roles of the trunnions 20 and recesses 15 may be reversed by providing trunnions on the joint body and recesses or even apertures in the member 3. A further modification can be made by providing a certain amount of longitudinal play at the pivot point and an additional shoulder or shoulders on the member 3 facing the joint. In this way, end forces applied to the joint will be taken up by the shoulder 9 and the end face of the joint body and will prevent the transmission of stress to the pivot itself as this is the weaker part. In the case of the windscreen wipers, this will reduce the possibility of damage to the wiper blades if they should be dropped on their ends. Although the invention has been described with particular reference to windscreen wipers, the invention is equally applicable to other applications where this type of pivot joint may be useful.

Claims: 1. A pivot joint for pivotally connecting two members comprising a joint body (4) of substantially channel shaped cross section characterised in that the joint body (4) has pivot means (15) in the opposite side walls (7) of the channel for pivotal connection with one (3) of the members (2,3) to be pivoted which is intended to lie within the channel of the joint body (4), a sprung element (10) directed outwardly from the base of the channel of the joint body (4) for engagement with a cooperating device (17) on the other member (2) to be pivoted, which other member (2) is intended to sit on and around more than three sides of the joint body (4), such that the joint body (4) is fixed in at least one longitudinal direction by the sprung element (10) and the cooperating device (17) on the said other member (2). 2. A pivot joint as claimed in claim 1, characterised in that an abutment surface (9) is provided on the joint body (4) engageable with the end surface of the said other member (2) whereby the joint body (4) is fixed in the longitudinal direction between the sprung element (10) and the abutment surface (9). 3. A pivot joint comprising a first member (2) which is of channel section at least at one end, a second member (3) pivotable to said one end of the first member (2) and adapted to sit within the channel section of the first member (2) with clearance and a joint body (4) of substantially channel section adapted to sit substantially within the first member (2) and at least partially around the second member (3) so as to separate the members (2,3), characterised in that the joint body (4) has pivot means (15) in the opposite side walls (7) of the channel cooperating with pivot means (20) on the second member (3), a sprung element (10) directed outwardly from the base of the channel engaging with a cooperating device (17) on the first member (2) and abutment means (9) engageable with said one end of the first member (2) such that the joint body (4) is fixed longitudinally between the sprung element (10) and the abutment means (9), the channel section of the first member (2) being provided towards the said one end with inwardly directed lips (19) such that the first member (2) surrounds the joint body (4) on more than three sides. 4. A pivot joint as claimed in claim 3, characterised in that the inwardly directed lips (19) of the first member (2) define the mouth of the channel section at this point, the mouth of the channel section being at least as wide as the width of the second member (3) whereby the second member (3) can pass into the channel section of the first member (2) through the mouth thereof. 5. A pivot joint as claimed in claim 3 or 4, characterised in that the sprung element (10) of the joint body (4) comprises a detent (12) carried by the end of a resilient tongue, (6) the detent (12) cooperating with an aperture (17) in the base of the channel section of the first member (2). 6. A pivot joint as claimed in claim 5, characterised in that the detent (12) has two abutment surfaces facing in longitudinally opposite directions cooperating with complementary abutment surfaces formed by longitudinally oppositely facing edges of the aperture (17) in the first member (2). 7. A pivot joint as claimed in any one of claims 3 to 6, characterised in that the pivot means (15) on the joint body (4) comprises a recess which cooperates with a projection on the second member (3). 8. A pivot joint as claimed in any one of claims 3 to 6, characterised in that the pivot means (15) on the joint body (4) comprises a projection which cooperates with a recess on the second member (3). 9. A pivot joint as claimed in any one of claims 3 to 6, characterised in that the pivot means (15) on the joint body comprises an aperture in the joint body (4) through which a pivot pin (25) passes, the pivot pin (25) passing also through one or more apertures in the second member (3). 10. A pivot joint as claimed in any one of claims 3 to 9,characterised in that the first and second members (2,3) comprise yokes or levers of the blade harness of a windscreen wiper which are to be pivoted together. 11. A pivot joint as claimed in claim 10, characterised in that the first member (2) comprises the main yoke of a windscreen wiper blade and the second member (3) comprises a secondary yoke or lever.

Inventors: FRIMLEY, CHARLES HENRY
Applicants: TRICO-FOLBERTH LIMITED
Application year: 1987
Main classification: B60S1
IPC codes: F16B7, B60S1