FR2508579A1 - BALL JOINT FOR WINDSCREEN WIPER LINKAGE - Google Patents

Abstract

THIS BALL JOINT FOR WINDSCREEN WIPER LINKS INCLUDES A BALL JOINT PART 26 MADE OF A NON-METALLIC MOLDABLE SYNTHETIC MATERIAL SUCH AS A SYNTHETIC POLYAMIDE LOADED WITH GLASS FIBERS AND A BALL JOINT PART MOLDED BY INJECTION 'A MOVED PART 36 OF THE TAIL 34 OF A METAL AXIS 30 AN ACETAL COPOLYMER CONTAINING A LUBRICATING MATERIAL FOR DISPERSED REACH IN ITS MASS. AN APPROPRIATE ACETAL COPOLYMER, WHICH CONTAINS POLYTETRAFLUOROETHYLENE IN DISPERSION AS A LUBRICANT, IS MANUFACTURED BY THE HOECHST CHEMICALS FIRM UNDER THE COMMERCIAL DESIGNATION OF HOSTAFORM C9021 TF.

Description

The present invention relates to ball joints for linkages

  windscreen wiper and in particular ball joints for wiper linkages in which the ball joint box part of the seal is formed from a non-metallic, synthetic, moldable composition.

  It is usual for vehicle wipers.

  automobiles, to include at least two squeegees or wiper blades carried by swinging arms

  separated which are connected to a wiper motor

  provided by a linkage having a number of universal ball joints These linkages are almost invariably placed in vehicle locations such that the joints of these linkages are relatively inaccessible therefore it is essential that these linkages be able to operate for

  extended periods with minimal maintenance.

  Ball joints are known for linkages

  wipers with a long service life in

  which the ball joint box part of the joint is made of a non-metallic, synthetic moldable composition, such as a synthetic polyamide material reinforced with glass fibers. Such a material is, for example Nylon 12

  loaded with 30% fiberglass, sold by the firm Ves-

  tamid under the trade designation L-1930 Black 97503.

  The ball joint part usually used with such a non-metallic ball joint box is made of steel. It has been found that these non-metallic ball joint boxes are very hard and dimensionally very stable, but that during use the load composed of fiber of

  glass tends to wear out, forming a glass powder containing

  bare in the joint and which can heavily wear the ball-joint part in untreated steel To eliminate this effect, the steel ball-joint part is machined to a very fine surface state, a nickel coating is deposited, by a non-electric process, on the steel ball joint part, and then the coated ball joint part is subjected to a thorough burnishing to obtain a contact surface having the hardness of the glass. This process certainly solves the problem of the wear of the ball joint part but it makes the cost of the part

extremely high finished ball joint.

  A ball joint for wiper linkages

  glass according to the invention is a joint in which the

  ball joint boot part is made of a syn-

  nonmetallic moldable and the ball joint part is

  formed by injection molding around the mole tail

  tee of a metal rod an acetal copolymer containing in dispersion in its mass a lubricating material for bearings. The acetal copolymer used is preferably a

  acetal copolymer modified by polytetrafluoroethylene.

  An example of such a copolymer is manufactured by Hoechst Chemicals under the trade designation of Hostaform

C 9021 TF.

  The ball joint part can be produced in the form of a spherical volume around the metal rod, but the shape of the ball joint part is advantageously that of an annular torus which surrounds the tail of such a rod. The joint line of the molding by injection which forms the patella part is preferably arranged to be presented along two diametrically parts

  opposite of the annular torus which have a curvature of

  face less sharp than the curvature of the rest of the annulus

laire.

  Other features and advantages of the

  vention will appear during the description which goes

  follow In the accompanying drawings, given only as

example,

  Fig 1 is an elevational view of a rod

  wiper line including ball joints

before the invention;

  Fig 2 is a view of the wiper linkage

  glass shown in Fig l, taken along line 2-2 of Fig 1; Fig 3 is an enlarged sectional view of the ball joint part of a ball joint according to the invention;

  Fig 4 is a plan view of the ro-

  tule shown in Fig 3, taken along line 4-4 of Fig 3;

  Fig 5 is a sectional view of the ro-

  tule shown in Fig 3, taken in a direction perpendicular to that of the view shown in Fig 3; Fig 6 is a plan view of the ball joint part shown in Fig 5, taken along line 6-6 of Fig 5; and Fig 7 is a sectional view also at more

  large scale of one of the ball joints according to the

  vention, such as those shown in Figs 1 and 2.

  Figs 1 and 2 of the accompanying drawings are two

  views of a typical 10 wiper linkage

  single and double outlet train, fitted with seals

  ball joint 24 according to the invention An electric motor for

  drag (not shown) is coupled to a first end of a drive rod 12 by means of a rotary drive crank (not shown) and a ball joint according to the invention, of which only the boot part of ball joint 26 is shown in FIGS.

1 and 2.

  The other end of the connecting rod 12 is articulated on a first end of the transverse bar of a plate 14 forming a T-shaped connecting rod, by means of a second ball joint 24 The end of the

  foot of the T-shaped plate 14 is connected to the rear

  drive bre 16 of a first wiper arm and its squeegee (the arm and the squeegee not being shown) while the other end of the bar

  transverse of the T-shaped plate 14 is articulated

  abutment on a first end of a connecting rod 18 of

  training mission by means of a third joint

  24 The other end of the connecting rod

  mission of training 18 is based on a pre-

  first end of a crank 20 by means of a

  third ball joint 24, the other end of the ammi-

  velle 20 being connected to a drive shaft 22 of a second wiper arm provided with its squeegee (So shown).

  The operation of the electric motor

  drag produces an alternating movement of the drive rod 12, movement which is transmitted by the ball joints 24, interposed, to the format plate

  rod 14 and crank 20 to generate a Du-

  corresponding oscillatory movement of the drive arms

16 and 22.

  We will now refer to Figs 3 to 6 of

  drawings These figures show views in section, partly

  vation and in plan on an enlarged scale, of the ro-

  tule 28 of a ball joint 24, taken in two directions

  perpendicular to each other The ball joint part 2 B shown in FIG. 3 is composed of an acetal copolymer containing in its mass a lubricating material for bearings, and which is injection molded around a

  axis 30 in zinc-plated mild steel Axle 30 has a collar

  leriette 32 coming from material, formed near its end 33 and a tail 34, of which Ane part 36 of the

  surface, located between the collar 32 and the other end

  mity 38 of this tail is provided with a precut knurling.

  The acetal copolymer forming the ball joint part 28 is injection molded around the knurled part 36 of the shank 34 and it is thus securely locked in position on the axis 30 in a way which prevents it from moving.

relative to axis 30.

  In a preferred embodiment of the invention,

  note, the ball joint part is made of an acetal copolymer

  containing as lubricant for litters, polyty-

  trafluoroethylene dispersed throughout its mass and which is fa-

  bricked and sold by Hoechst Chemicals under the

  Commercial designation of Hostaform C 9021 TF Qn for-

  should use instead of polytetrafluoroethylene other lubricants for bearings such as

molybdenum disulfide.

  The physical properties of Hostaform C 9021 TF are as follows: Density l Water absorption after 24 hours Water absorption after 96 hours Melting index MF 1 190 / 2.16 Elastic limit 5: Elongation at break 2 C Limit stress of bending 9 z Torsional rigidity at 23 C 75 (Torsional rigidity at 120 C Bending creep module, value 1 mm 26 (Ball hardness, index 30 S 1: Shore hardness Impact resistance Impact resistance on notch at 23 C 4 Dynamic coefficient of friction on a rotating steel shaft (roughness depth 2.5 u) 0, Dimensional hot stability (Martens method) Dimensional hot stability (heat deformation temperature) Vicat softening point VSP / B Interval of crystalline melting Coefficient of linear expansion 20-100 C Heat capacity Specific heat at 20 C Volume resistivity Surface resistance Dielectric constant 1.52 g / cm 3 mg mg 8 g / 10 min 3 N / mm 2

0-25%

  4 N / min 2 N / min 2 N / mm 0 O N / mm 2 33 N / mm 2 m J / mm 2 4.5 m J / mm 2

2 0.25

76 C C C

L 150 C

164-167 C

  1.1 x 104 1.31 W / m K 1.47 k J / kg K 1015 cm 3.6 The injection molding of the ball part 28 around the axis 30 is carried out in a core mold

  precisely formed which is designed to mold the

  tie ball joint 28 in the form of an annular torus, one of which

  main part has a predeter curved surface-

  mined 40 which corresponds exactly to the surface 41 of the ball joint portion 26 shown in Figs 1,2 and 7 of the drawings Two smaller parts of the annular torus which are diametrically opposed to each other have a curved surface 42 which is less curved that the curved surface 40, as we can

  see it clearly in Figs 3, 4,5 and 6 of the drawings.

  The core mold of the ball joint part is studied

  niere that the joint line produced on the surface of the gross ball joint part 28 is placed in said small parts of the annular torus Since the curved surface 42 is smaller than the curved surface 40, this joint line will not enter not in contact with the corresponding curved surface 41 of the part

  ball joint box 26 during use of seal 24.

  Therefore, it is not necessary to burnish or otherwise machine the rough ball portion 28

  molding to eliminate the joint line.

  The ball joint 24 is assembled

  by direct insertion of the ball joint part 28, by

  latching, in the ball joint box part 26, which is made of a moldable non-metallic composition

  such as, for example, a synthetic polymer

  titrated with Nylon 12 loaded with glass fiber

  from 30% by weight such compounds can be obtained

  with manufacturers such as H Uils (U K) limited and Vestamid Alternatively,

  the ball joint part 26 can be made of a poly-

  synthetic mother Nylon 6 containing molyb disulphide

  dene as filler Such a composition is sold under the commercial designation "Nylotron GS" by a firm known as Polypenco A sectional view of the assembled ball joint 24 is shown in Fig 7 It shows the fourth ball joint 24 of Fig 1 and 2 As can be seen in Fig 7, to fix the ball joint part 28 of the ball joint 24 to the crank 20, the end 33 of the pin 30 is threaded through an appropriate opening in the end of the crank 20, until the flange 32 of the axis 30 is in contact with the crank 20 and then the end 33 is shored to block the axis 30

in position on the crank 20.

  The ball joint according to the invention shows

  feels a remarkable improvement compared to

  ball joints already known for wiper linkages

  ice in terms of ease of manufacture, the

  manufacturing cost and useful life.

  The axis which carries the ball joint part is made of a relatively inexpensive material and it is easy to manufacture, being made of mild galvanized steel which is shaped by hot pressing and not by turning, and the ball joint part is injection molded

  on the axis in a rapid and reproducible manner, at

  correct work terms without further processing

  surface The acetal copolymer of the pre-ball joint part

  feels dimensional stability and strength superior to that of synthetic polyamides such as Nylon, without exhibiting significant water absorption or shrinkage In addition, a useful feature

  of the present invention resides in the fact that the ma-

  the ball joint has sufficient flexibility

  health to compensate for the tendency of the box part

  molded ball joint to deform from a circular shape

  cular to an oval shape at the time of demolding This in turn has the effect of giving a better torque

  outlet at such a joint, compared to ro-

already known tule -

Claims (6)

  1 Ball joint for wiper linkages   lens comprising a ball joint box part made of a moldable non-metallic synthetic composition and a ball joint part, characterized in that said ball joint part (28) is made by injection molding around the knurled tail (34) of a metal axle (30) a copolymer   acetal containing a lubricating material for spans persisted in its mass.   2 Ball joint for wiper linkages   glass according to claim 1, characterized in that the acetal copolymer contains polytetrafluoroethylene dispersed in its mass.   3 Ball joint for wiper linkages   glass according to claim 1 or 2, characterized in that the shape of the ball joint part (28) is that of a torus   annular surrounding the tail (34) of said axis (30).   4 Ball joint for wiper linkages   lens according to claim 2, characterized in that two small diametrically opposite parts of the annular torus each have a curved surface (42) which is less curved than the remaining curved surface (40) of the annular torus and in that the joint line of the injection molding of the ball joint part (28) is placed in   the area of the surface of these two small parts.   5 Ball joint for wiper linkages   ice cream according to any one of the preceding claims   cédentes, characterized in that the ball joint box part (26) is made of a synthetic material constituted by   a polymer loaded with glass fiber.   6 Ball joint for wiper linkages   glass according to any one of claims 1 to 4,   characterized in that the ball joint box part (26) is made of a synthetic material of the polyamide type which contains molybdenum disulphide as a filler.