METHOD FOR USING ULTRASOUND TO LOCK A PLASTIC PLUG THAT PLUGS A STEERING BOX

• US 20200130724A1
• Filed: 05/04/2018
• Published: 04/30/2020
• Est. Priority Date: 05/18/2017
• Status: Active Grant

• Current Assignee: Jtekt Europe (Toyota Motor Corporation)
• Original Assignee: Jtekt Europe (Toyota Motor Corporation)
• Inventors: VIZIER, Pascal, GOUJON, Bruno
• Granted Patent: US 11,679,799 B2
• Time in Patent Office: Days
• CPC Class Codes: B29C 65/08 using ultrasonic vibrations non-plastics element to plastics elements B29C65/645
• CPC Class Codes: B29C 65/561 using screw-threads being integral at least to one of the parts to be joined
• CPC Class Codes: B29C 65/567 using a tamping or a swaging operation, i.e. at least partially deforming the edge or the rim of a first part to be joined to clamp a second part to be joined
• CPC Class Codes: B29C 65/606 the rivets being integral with one of the parts to be joined, i.e. staking
• CPC Class Codes: B29C 65/64 Joining a non-plastics element to a plastics element, e.g. by force B29C65/44 takes precedence
• CPC Class Codes: B29C 65/645 using friction or ultrasonic vibrations
• CPC Class Codes: B29C 65/72 by combined operations or combined techniques, e.g. welding and stitching
• CPC Class Codes: B29C 66/21 said joint lines being formed by a single dot or dash or by several dots or dashes, i.e. spot joining or spot welding
• CPC Class Codes: B29C 66/30325 making use of cavities belonging to at least one of the parts to be joined
• CPC Class Codes: B29C 66/53245 said articles being hollow
• CPC Class Codes: B29C 66/61 Joining from or joining on the inside for making tubes by bending sheets and joining from the inside B29C53/387
• CPC Class Codes: B29C 66/71 characterised by the composition of the plastics material of the parts to be joined welding bar compositions B29C65/125
• CPC Class Codes: B29C 66/721 Fibre-reinforced materials B29C66/729 takes precedence
• CPC Class Codes: B29C 66/7212 characterised by the composition of the fibres
• CPC Class Codes: B29C 66/7392 characterised by the material of at least one of the parts being a thermoplastic
• CPC Class Codes: B29C 66/742 to metals or their alloys
• CPC Class Codes: B29C 66/7422 Aluminium or alloys of aluminium
• CPC Class Codes: B29C 66/81431 comprising a single cavity, e.g. a groove
• CPC Class Codes: B29C 66/81463 comprising a plurality of single pressing elements, e.g. a plurality of sonotrodes, or comprising a plurality of single counter-pressing elements, e.g. a plurality of anvils, said plurality of said single elements being suitable for making a single joint
• CPC Class Codes: B29C 66/8322 Joining or pressing tools reciprocating along one axis
• CPC Class Codes: B29C 66/8432 : Machines for making separate joints at the same time mounted in parallel or in series
• CPC Class Codes: B29C 66/9513 : characterised by specific vibration frequency values or ranges
• CPC Class Codes: B29K 2059/00 : Use of polyacetals , e.g. POM, i.e. polyoxymethylene or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2077/00 : Use of PA, i.e. polyamides, e.g. polyesteramides or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2077/10 : Aromatic polyamides [polyaramides] or derivatives thereof
• CPC Class Codes: B29K 2309/08 : Glass
• CPC Class Codes: B29L 2031/30 : Vehicles, e.g. ships or aircraft, or body parts thereof vanes or blades B29L2031/08, air bags B29L2022/027
• CPC Class Codes: B62D 3/12 : of rack-and-pinion type
• CPC Class Codes: B62D 3/123 : characterised by pressure yokes

Abstract

A method includes a rotation locking step during which the rotation of the threaded hub about the central axis is blocked by heating a portion of the plug to soften, then by forcing the softened thermoplastic material to penetrate into, and then solidify in, a female cavity hollowed in the wall of the orifice to constitute a male member which fits into the female cavity. The female cavity forms, against the action of the male member, a guiding end stop preventing the male member, and therefore the hub, from rotating about the central axis to oppose any rotary screwing/unscrewing of the plug and maintaining a degree of freedom in axial translation along the central axis of the male member within the female cavity, so as not to impede a sliding of the hub and of its screw thread along the central axis against the wall.

Claims

1. A plugging method allowing plugging an orifice with a central axis pierced in a wall by means of a plug having a threaded hub provided with at least one thread, said method comprising a screwing step during which the threaded hub of the plug is screwed into the orifice by fitting the thread of said hub against the wall, then a rotational locking step, during which the rotation of the threaded hub about the central axis is blocked in order to resist the screwing and unscrewing of the plug, wherein, at said rotational locking step, a portion of the plug made of a thermoplastic material is heated up so as to soften said thermoplastic material, the softened thermoplastic material is forced to penetrate, and then to solidify, into a female cavity drilled in the wall of the orifice in order to constitute a male member which nests into said female cavity, the female cavity being arranged such that it forms against the male member a guide stop which, on the one hand, prevents the rotation of the male member, and therefore of the hub, about the central axis, so as to resist a screwing or unscrewing rotational movement of the plug, but which on the other hand keeps a degree of freedom in axial translation, along said central axis, of said male member within said female cavity, so as not to hinder a sliding of the hub and of its thread along the central axis, against the wall, in that there is provided, in the wall, a female cavity formed by at least one notch which opens onto the orifice and which is delimited in azimuth around the central axis by surfaces, called bearing surfaces surfaces, which are substantially parallel to said central axis, and in that, at the rotational locking step, the softened thermoplastic material is pushed radially into said notch so as to form at least one lug which forms a male member projecting radially with respect to the hub and which slidably bears against said bearing surface, so as to be blocked in rotation about the central axis but free to axially slide along the central axis.

2. The plugging method according to claim 1, characterized wherein, at the screwing step, the threaded hub is screwed into the orifice in a direction called «

penetration direction»

, against an elastic member which exerts on said hub a biasing force oriented in an opposite direction, called «

extraction direction»

, such that said elastic member tends to urge the thread of the hub so as to bear at the rear against the wall, and the screwing is continued until the hub reaches a desired axial position, called «

calibration position»

, in which the thread of the hub is pressed so as to bear at the rear against the wall by the elastic member, in that, at the rotational locking step, a forming tool which exerts an insertion force in the penetration direction is applied on the plug, to soften and push the thermoplastic material into the female cavity, said insertion force thus tending to peel off the thread of the hub from its back bearing, and to displace the plug in the penetration direction relative to the calibration position, and then in that, once the male member is formed, the forming tool is removed so as to release the insertion force and to enable the hub and the male member to perform, under the action of the elastic member, a return movement in the extraction direction, until the plug recovers its initial calibration position, with the thread of the hub pressed so as to bear at the rear against the wall.

3. The plugging method according to claim 1, wherein the female cavity includes a plurality of distinct notches, distributed around the central axis, and in that, at the rotational locking step, there are simultaneously formed a plurality of distinct male lugs each penetrating into one of said notches and each cooperating by sliding bearing against the bearing surfaces of their respective notch.

4. The plugging method according to claim 3, during which, at the rotational locking step, a forming tool which is split, around the central axis, into as many arms as there are male lugs to be made, each arm covering an angular sector which corresponds to the notch that is assigned to said arm, is applied against the plug, to soften and then push the thermoplastic material.

5. The plugging method according to claim 1, wherein the hub of the plug has a peripheral crown made of a thermoplastic material, which forms a hollow cylinder centered on the central axis and which has a radially outer face which carries at least partially the thread of the hub, as well as a radially inner face which is accessible from the outside when the hub is screwed into the orifice, and in that, at the rotational locking step, the crown is partially softened, in each area located angularly with respect to a notch, and then, in each area thus softened, the thermoplastic material constitutive of the crown is pushed at least according to a centrifugal radial direction to make said softened thermoplastic material penetrate into the notch corresponding thereto, and thus constitute a male lug integral with the crown.

6. The plugging method according to claim 4, wherein each arm has one end which is intended to come into contact with the edge of the crown which extends radially between an inner radius, corresponding to the radially inner face of the crown, and a radially outer radius corresponding to the radially outer face of said crown, and to fit into said crown according to an axial penetration movement to progressively push the softened thermoplastic material into the female cavity, said end having an imprint which comprises, in a section in a longitudinal sectional plane containing the central axis,

a first flange, arranged to be the first to bear against a radially outer portion of the edge of the crown, and which extends to this end in a centrifugal radial manner from an intermediate radius strictly comprised between the inner radius and the outer radius up to, or beyond, the outer radius of said crown, in order to initially concentrate the energy supply outwardly and thus promote the softening and the centrifugal radial migration of the thermoplastic material,

an inclined deflector, which extends the first flange both radially, in the centrifugal radial direction, and axially in the direction of the penetration movement, and which forms a draft with respect to the central axis so as to be able to guide radially outwards and compact the softened thermoplastic material in order to form the projecting lug on the radially outer face of the crown, during the axial insertion of the tool into the crown.

7. The plugging method according to claim 1, wherein the angular coverage of each lug, in azimuth around the central axis, and considered at the base of said lug at the radial limit between the plug and the notch, is smaller than or equal to 30 degrees.

8. The plugging method according to claim 1, wherein it comprises a forced unlocking step, during which a manipulating member provided on the plug is engaged and the rotation of the hub about the central axis is forced by breaking the male member, and then a setting step, during which the hub is screwed or unscrewed in order to modify its axial position with respect to the orifice, and then a new rotational locking step during which are formed, by softening and by pushing into the female cavity, a new portion made of a thermoplastic material of the same plug, a new male member which is angularly shifted with respect to the original male member, in order to block the hub in rotation about the central axis while keeping a degree of freedom in axial translation relative to said central axis.

9. The plugging method according to claim 1, wherein an ultrasonic apparatus, called «

sonotrode»

, whose frequency is higher than 20 kHz, is used, as a forming tool to soften by heat-up a portion of the plug made of a thermoplastic material and then push the softened thermoplastic material into the female cavity.

10. A power steering system comprising at least one mechanism housed within a steering casing which is plugged by a plug in accordance with the plugging method according to claim 1.

11. An ultrasonic forming tool intended to lock in rotation a plug screwed beforehand into an orifice, said forming tool comprising a body which extends according to a central axis and which carries a plurality of distinct arms, distributed around the axis, said arms being arranged to transmit ultrasonic waves to the plug, at the level of the periphery of said plug, in order to be able to locally heat up and soften, in a simultaneous manner, different peripheral portions of the plug, located in distinct angular sectors around the central axis and made of a thermoplastic material, and in order to be able to push, according to at least one centrifugal radial direction the thermoplastic material softened in this manner in each concerned angular sector, when the tool is pressed axially against the plug to exert an insertion force, so as to make project on said plug, in said angular sector, a lug which fits into a corresponding notch provided in a wall of the orifice, according to an arrangement such that the lug rotatably abuts against the bearing surfaces delimiting said notch while keeping a freedom to axially slide against said bearing surfaces.