FR2843319A1 - Retractable centering pin for positioning motor vehicle parts comprises moving element connected to pin support having centering pin mounted on it, and axial translation driving and guide part for moving element - Google Patents

Abstract

The centering tool comprises a body connected to a machining or assembly post and a moving element solidly connected to a pin support (16) having a centering pin (18) mounted on it. The centering pin engages a centering hole (12) located in the part (10). There is a driving and guiding part (54) having a convex surface (58) engaging a concave surface (60) on the tool body for the axial translation of the moving element between an out position, where the pin penetrates the centering hole, and a retracted position in which the part is released. The guide means are able to ensure precise axial translation guidance of the mobile element only over a part of its travel (x). The mobile element floats with the possibility of lateral displacement over the rest of the travel.

Description

Retractable centering pilot tool for positioning parts,

  The invention relates in particular to the field of tools for positioning parts, in particular structural or body parts of a motor vehicle. 10 These tools are used in industry to position workpieces or to reference parts to be assembled. They find particular application in the machining and assembly lines of structural elements or bodywork of motor vehicles. These positioning tools can be mounted either on a machining or fixed assembly bench, or at the end of a robot arm, on a mobile pallet, on an overhead conveyor or on the ground, etc. More specifically, the invention relates to a tool for positioning a part having at least two centering holes for its referencing in a given plane, generally a horizontal plane. The tool then comprises "pilot carriers" 25 corresponding to the centering holes, each of the pilot carriers supporting a "pilot", that is to say a spindle which is housed in a corresponding hole in the part, and comprises means motors for driving the pilot in translation between an extended or deployed position, where the pilot 30 is fitted in the hole, and a position

  retracted or retracted, which leaves the workpiece clear to allow it to be set up or removed from the machining station.

  This maneuver is shown diagrammatically in FIG. 1, where there is shown at 10 the part to be referenced, with its two holes

  centering 12 placed opposite the pilot carriers 14.

  Each pilot holder is in the form of a body 16 from which the spindle or pilot 18 (arrow 20) can emerge, on command of an operator or an automaton, until it comes

place in the centering hole 12.

  Two operations are possible: the pilots 18 can be removed after the part has been placed on its machining or mounting support 5 (support not shown); or, alternatively, the pilots can be taken out before the part

  is not placed on this support.

  It will be noted that the pilots are only used for referencing the part in a plane perpendicular to the axis of the pilots, that is to say in the horizontal plane in the example of FIG. 1, the referencing in height of the part being provided by its machining or mounting support on which it rests, and not by the pilots. 15

  More specifically, the pilot is a cylindrical piece terminated by a conical end, with an apex angle typically of the order of 15, to facilitate the introduction of the pilot into the centering hole and its extraction from this hole.

  The pilot is guided precisely over its entire travel, which is generally the translation travel of the rod of a pneumatic or electric actuator. One of the difficulties encountered is that the pilots wear out quickly during the outgoing movements as well as during the withdrawal movements, by rubbing against the edges of the centering holes of the parts. This wear is accentuated by the fact that the piece to be centered, typically

  a body sheet, can work due for example to thermal expansions, or even have tolerances on the distance between the centering holes, phenomena which accentuate the friction of the pilots against the edges of these holes.

  To overcome these drawbacks, the pilot is made from a very resistant material; we can also "degrease"

  one of the pilots, that is to say locally forming flats on at least part of the pilot by removing material, in order to limit the contact in two regions of the circular centering hole, between this pilot and the hole. A certain degree of freedom is thus introduced into the radial plane, that is to say the plane perpendicular to the axis of translation of the pilot, without appreciably affecting the precision of the positioning of the part.

  However, these measures prove to be insufficient and the pilot remains a wearing part, which is removably mounted on the pilot holder and must be replaced frequently if one wishes to maintain good positioning accuracy of the part. The object of the invention is to remedy this drawback, by means making it possible to alleviate the phenomenon of friction between the pilot and the centering hole during the movements of introduction and withdrawal of the pilot. The basic idea of the invention is to float the pilot during most of the race and to guide him precisely only at the end of the exit movement - or, correspondingly, only at the start of the movement withdrawal. In this way, during most of the race, the pilot does not

  will not be guided precisely, thus allowing a certain lateral movement (in the radial plane), and thus significantly reducing friction and, consequently, wear and tear on the pilot.

  More specifically, the invention provides for this purpose a tool for positioning parts of a known general type, comprising: a tool body, connected to the machining or assembly station; an assembly movable relative to this body, comprising a movable assembly capable of projecting from the body and integral with a pilot carrier on which is mounted a centering pilot capable of cooperating with a centering hole of the part to be positioned ; and drive means,

  to drive and guide in axial translation said movable assembly between an extended position, where the pilot enters the centering hole of the part, and a retracted position leaving the part free.

  According to the invention, this tool is characterized in that the drive means comprise guide means capable of ensuring precise guidance of the movable assembly only over part of its travel along the axial translation movement, at in the vicinity of said extended position, the moving assembly being on the remainder of the stroke mounted floating with the possibility of lateral movement, in a radial plane perpendicular to the drive direction, over the major part of the axial translation stroke. Very advantageously, the guide means are means also capable of immobilizing the crew in axial rotation.

  movable over the entire axial translation stroke.

  In a preferred implementation, the guide means comprise at least two guide parts housed inside the body, on either side of the movable assembly, these guide parts being driven in axial translation at the same time that the mobile assembly and being provided with these convex surfa25 able to cooperate, at the end of the race, with homologous fixed concave surfaces integral with the body of the tool.

  The surfaces of the guide parts may in particular be frustoconical, or cylindrical surfaces.

  In order to immobilize the mobile assembly in axial rotation, the guide pieces are advantageously further provided, in their region facing the mobile equipment, with a flat mete extending in a plane parallel to the axis of the tool and

  able to cooperate with a homologous flat formed on the mobile assembly.

  As a variant, the guide parts and the movable assembly can be housed together in a hole in the tool body having, in cross section, an oblong shape.

  In a preferred form of implementation, the drive means comprise motor means driving in rotation a threaded axis received in a nut mounted floating with transverse play in a cage secured in translation

of the moving crew.

  Finally, the drive means can advantageously include motor means mounted in a power stage, and in that the body with the mobile assembly and the guide means are mounted in a mechanical stage coupled in a separable manner to the power stage.

  Other characteristics and advantages of the invention will appear on reading the following description of two exemplary embodiments, given by way of illustration with reference to the appended figures, in which the same reference numerals designate identical or functionally similar elements. In these figures:

  FIG. 1, cited above, is a schematic view illustrating the way in which the part provided with its centering holes can be positioned by means of pilots cooperating with these holes; FIG. 2 is a sectional view of a pilot carrier and of a pilot according to the invention, the pilot being in the extended position, at the end of the race; - Figure 3 is a sectional view in a radial plane, according to III-III of Figure 2; - Figure 4 is a sectional view in a radial plane, according to IV-IV of Figure 2; - Figure 5 is a partial schematic plan view of the part marked V-V of Figure 2; FIG. 6 is homologous with FIG. 2, for a variant embodiment of the pilot carrier according to the invention; and

  FIGS. 7, 8 and 9 are views in radial section, respectively along VII-VII, VIII-VIII and IX-IX of FIG. 6.

  Figures 2 to 5 illustrate a first embodiment of the centering tool according to the invention. In these figures, the pilot 18, removably mounted on his pilot carrier 16, is shown in the extended position, namely the position in which it performs its referencing function, that is to say that its cylindrical part is entirely

  introduced into the orifice 12 of the part 10.

  Also shown at 22 is the relative position of the part 10 with respect to the pilot 18 when the latter is in

  partially extended position, where only the conical part of the pilot 18 has started to penetrate the centering hole 12.

  As indicated above, the pilot 18 is mounted amo25 vible on the pilot carrier 16, for example by positioning

  in an appropriate housing for the latter and tightening of a nut 24. This makes it easy to exchange the pilot independently of the rest of the tool, and to produce this pilot in a different material, much harder and resistant to friction.

  The pilot carrier 16 is integral with an assembly 26 movable in axial translation relative to a fixed body 28, this body 28 being for example integral with the work station where the part must be machined, or else mounted at the end the arm of a robot, etc. The body 28 with the moving assembly 26, the pilot carrier and the various parts contained in the body and which will be described later, constitute a mechanical stage 30 coupled to a power stage 32 provided with means making it possible to train the moving part in its translational movement.

  The power stage 32 is advantageously an electric stage, thus avoiding the problems inherent in pneumatic cylinders - although the latter solution can be envisaged as a means of driving the pilot carrier of the invention.

  The power stage 32 is assembled at 34 to the mechanical stage 30, in a removable manner in order to be able to ensure the non-changeability of one or the other of the mechanical stages 30 or of the power stage 32: in the event of failure of any of these stages, it is sufficient to dismantle it to replace it with a new stage. This minimizes downtime during replacement operations, which is particularly advantageous in the

  motor vehicle assembly line, which cannot be stopped to replace defective tools.

  The power stage 32 includes an electric motor 36

  whose output axis is coaxial with the general axis of the tool.

  The motor 36 is preferably a brushless motor, supplied with direct current and at low voltage; it is controlled according to a predetermined law making it possible to precisely define the movement of the pilot carrier and therefore of the pilot by

  report to the part to be referenced.

  The motor 36 is connected to the mechanical stage 30 by a coupling 38, advantageously a dismountable coupling 35 with elastic connection to allow easy separation of the two power 32 and mechanical stages 30. The coupling 38 can moreover be provided with a torque limiter making it possible in particular to avoid damage to the motor 36 in the event of blockage or forcing of the parts of the mechanical stage 30

driven by this motor.

  The coupling 30 rotates a wheel in the form of a wheel 42, which can be manually actuated if necessary by lateral openings 44 formed in the body 28 in the event of an operating incident, in particular to allow the hand to retract the pilot carrier in the event of failure of the power stage 32. 10 The thumb wheel 40 is integral in rotation with a threaded axis 46, which it drives in axial rotation, in one direction or in

  the other, when the motor 36 is supplied.

  This threaded axis 46 is received in a nut 48 mounted floating in a cage 50 integral in translation with the movable assembly 26 but allowing a certain transverse play (that is to say in a plane perpendicular to the axis of rotation) between l 'rod assembly 46-nut 48, on the one hand, and the cage assembly 50 50-moving element 26 on the other hand. Furthermore, the cage 48, linked to the crew 26, prevents any rotation of the nut

48 on himself.

  Thanks to this configuration, the rotational movement of the motor 36, transmitted to the wheel 40 and to the threaded axis 46, is

  transformed into an axial translational movement of the nut 48 (whose rotation is prevented by the cage 50), therefore into an axial translational movement of the moving element 26, and finally of the pilot carrier 16 and of the pilot 18 on a total stroke x.

  There are also provided guide pieces 54, specific to the invention, which will now be described in more detail. These parts, two in number in the example illus35 very, are housed inside the body 28, on either side of the rear part 52 of the movable assembly, that is to say the part located axially between the cage 50 and the part projecting from the body 28 and connected to the holder

pilot 16.

  These guide pieces 54 are linked to the mobile assembly 26, in the vicinity of the cage 50, by pins 56 generally extending in a radial plane (see in particular FIG. 3) and coupling the two guide pieces 54 to the rear part 52 of the moving part 26 traversed right through

by these pins 56.

  The guide pieces 54 have, in the embodiment illustrated in FIGS. 2 to 5, a partially frustoconical shape, the conical convex surfaces 58 of these guide pieces 54 being capable of cooperating, when the movable assembly is close to its entirely position outlet with homologous conical concave faces 60 machined on a cover 62 made integral with the body 28, for example by means of

locking screws such as 64.

  These parts 54 are further provided, in their region at 20 with respect to the rear part 52 of the mobile assembly 26,

  a flat 59 extending in a plane parallel to the axis of the tool and intended to come into abutment against a homologous flat 61 formed on this part 52 to prevent any movement of rotation of the movable assembly 26 and therefore of the pilot 25 holder 16 and of the pilot 18.

  Furthermore, the seal between the body 28 and the emerging part of the movable assembly 26 is ensured by a scraper seal 66, with lateral play at this location. In addition, a bellows 68 advantageously isolates from the external environment the pilot carrier 16 and the emerging part of

the moving part 26.

  When the pilot carrier is in the fully retracted position, the cage 50 is in the position illustrated in phantom at 70, the guide pieces 54 then being at 72, set back from the conical surfaces

concaves 60.

  During a first phase corresponding to the major part of the exit stroke x of the moving element 26, due to the absence of contact between the guide parts 54 and the 5 concave homologous surfaces 60, the moving element 26 will himself

  find displaced in translation with a certain degree of lateral freedom (that is to say in a radial plane relative to the central axis corresponding to the translational movement), due to the floating mounting of the nut 48 in the cage 50 and 10 of the natural clearance existing at the scraper seal 66.

  In other words, a certain lateral movement is authorized during most of the phase of penetration of the pilot 18 into the centering hole 12 of the part 10, which has the effect of significantly reducing the friction between the pilot 18 and the centering hole 12 during this phase

of implementation of the tool.

  On the other hand, at the end of the race, when the crew is close to its fully extended position, the convex conical surfaces 58 of the guide parts 54 come progressively into contact with the concave conical surfaces 60 homologous to the parts 62 integral with the fixed body 28 , providing precise guidance of the moving assembly and, consequently, of the pilot 18, during the terminal phase of the movement, thus ensuring optimal referencing of the

  part for its machining or assembly.

  Conversely, after machining or assembly, during the stroke 30 to return to the retracted position, the lateral movement will allow the pilot to be removed from the centering hole while minimizing the friction forces and therefore the wear of the tool.

  during most of this withdrawal phase.

  Various implementation variants can of course

be considered.

  Thus, as illustrated in FIGS. 6 to 9, the pilot carrier and

  the moving element can be made in the form of a single piece 74. On the other hand, the guide pieces 54 can be pieces whose guide surfaces 76 are no longer conical but cylindrical surfaces, cooperating with surfaces concave cylindrical counterparts 78 formed in the cover 62 integral with the fixed body 28. To prevent any movement of rotation of the crew 74, this is housed with the cylindrical parts 54 in a hole 80 having, in cross section, an oblong shape as il10 particularly glossy in FIG. 8.

  In addition, as in the previous embodiment, the parts 54 are connected by pins 56 to the movable member 74, so as to immobilize the latter in rotation while allowing the transmission of the axial translational movement of the nut 48 under the effect of the rotation of the threaded axis 46. The mounting of this nut 48 on the threaded axis 46 is made with sufficient clearance to allow the desired lateral movement, at the level of the scraper seal 66, during the 20 major part of the moving crew exit race

carrying the pilot.

Claims (9)

claims   1. Tool for positioning parts, in particular for a machining or assembly station for structural parts or bodywork of a motor vehicle, comprising: - a tool body (28), connected to the machining or assembly, - an assembly movable relative to this body, comprising a movable assembly (26) capable of projecting from the body and integral with a pilot carrier (16) on which is mounted a centering pilot (18) capable of cooperating with a centering hole (12) of the part (10) to be positioned, and - drive means, for driving and guiding said movable assembly (26) in axial translation between an extended position, o the pilot enters the centering hole of the part, and a retracted position leaving the part clear, a tool characterized in that the drive means include guide means capable of ensuring precise guidance of the moving assembly (26 ) only for part of its course (x) along the axial translational movement, in the vicinity of said extended position, the moving assembly being 25 on the remainder of the stroke mounted floating with the possibility of lateral movement, in a radial plane perpendicular to the drive direction, over most of the axial translation stroke.   2. Tool according to claim 1, characterized in that the guide means are means also capable of immobilizing in axial rotation the movable assembly (26) over the entire axial translation stroke.   3. Tool according to claim 1, characterized in that the   guide means comprise at least two guide parts (54) housed inside the body, on either side of the movable assembly (26), these guide parts being   dragged in axial translation at the same time as the moving assembly and being provided with convex surfaces (58; 76) capable of cooperating, at the end of the race, with concave surfaces   counterparts (60; 78) fixed integral with the body of the tool.   4. Tool according to claim 3, characterized in that the surfaces of the guide parts are frustoconical surfaces (58).   5. Tool according to claim 3, characterized in that the   surfaces of the guide pieces are cylindrical surfaces (76).   6. Tool according to claims 2 and 3 taken in combination with sound, characterized in that the guide parts are further provided, in their region (52) vis-à-vis the movable assembly (26), with a flat part (59) extending in a plane parallel to the axis of the tool and able to cooperate with a homologous flat part (61) formed on the movable assembly (26). 20   7. Tool according to claims 2 and 3 taken in combination, characterized in that the guide parts (54) and the movable assembly (26) are housed together in a hole (80) of the tool body having in cross section an oblong shape.   8. Tool according to claim 1, characterized in that the drive means comprise motor means (36) driving in rotation a threaded axis (46) received in a nut 30 (48) mounted floating with transverse play in a cage ( 50)   integral in translation with the movable assembly (26).   9. Tool according to claim 1, characterized in that the drive means comprise motor means (36) 35 mounted in a power stage (32), and in that the body (28) with the movable assembly ( 12, 16, 26) and the guide means are mounted in a coupled mechanical stage (30)   separably (34, 38) on the power stage.