FR2813430A1 - METHOD FOR MOUNTING A HELICOIDAL SPRING IN A MOLDED PART OF AN APPARATUS, IN PARTICULAR AN ELECTRIC APPARATUS, MACHINE FOR IMPLEMENTING THIS METHOD AND APPARATUS WITH CORRESPONDING MECHANISM - Google Patents

Abstract

Fixing a spring on a molded plastic part. According to the invention, the part has a cavity (31) whose bottom has a hollow shaft (35), the spring (15) is introduced into the cavity at the same time than a rod (38) forming a punch and said hollow barrel (35) is crushed until the latter forms a bead (40) retaining the spring.

Description

The invention relates to a method for mounting a helical spring.

  in a molded part, in particular a plastic part forming part of a mechanism device, in particular an electrical device of the type

switch or the like.

  It also relates to a machine for implementing this method and also relates to any mechanism device, in particular any electrical device of the switch type comprising a molded part to which a helical spring is attached, the mounting of which has been carried out by using the process. In the field of devices with a mechanism, in particular electrical devices of the switch type, it is frequent to have to install a helical spring in a cavity of a molded plastic part, said cavity

  being shaped and dimensioned accordingly.

  However, maintaining the helical spring in position, in particular during the various phases of assembling the components of the device, requires a certain number of precautions due to the very elasticity of the spring which tends to come out of its housing at the slightest shock or at the slightest request. From this point of view, it is desirable that the spring is fixed to the bottom

of the cavity.

  One solution which has been envisaged consists in reducing the diameter of the last turns of the spring so as to come, using a suitable tool, to press it together

  around a pawn projecting from the bottom of the cavity.

  Another solution envisaged consisted in providing a pin projecting from the bottom of the cavity, the diameter of the free end of the pin being smaller than the inside diameter of the turns of the spring, the diameter of the pin progressively increasing and being, near from the bottom of the cavity, larger than the inside diameter of the turns of the spring, to come, thanks to a tool

  adapted, snap the spring around the pin.

  However, these processes are difficult to implement and they introduce a certain amount of uncertainty into the number of turns actually active, once the spring has been mounted in this way. This uncertainty is detrimental when said spring is part of a precision mechanism, for example when it participates in the actuation of a movable contact element of a switch. It has also been proposed to immobilize the spring at the bottom of the dimensioned cylindrical cavity to accommodate it by depositing therein a drop of grease retaining the spring in the cavity, during all the operations of assembling the constituent elements of the apparatus. It has been found that such

  product had, in the long term, harmful effects on the plastic used.

  In addition, during assembly, it is necessary to turn the part in which the spring is to be mounted, to deposit the drop of grease in the cavity. This reversal operation is difficult to implement and costly, in a

  automated production process.

  The invention overcomes all these drawbacks.

  Firstly, the invention relates to a method of mounting a helical spring in a molded part of an apparatus such as for example an electrical appliance of the switch type, said molded part comprising a cylindrical cavity dimensioned to accommodate at least one part. of said spring and provided with a hollow barrel projecting from its bottom, characterized by the operations consisting of engaging the spring in said cavity so that its end surrounds said hollow barrel and crushing said hollow barrel using a rod forming punch engaged longitudinally in the space delimited by the turns of said

  spring, so as to form a bead retaining the end of said spring.

  According to a preferred embodiment, a said spring is positioned around a rod, which is provided with a shoulder on which the end of the spring comes to rest. Then, the tiger spring assembly is engaged in said cylindrical cavity by continuing this movement by force until the end of said rod causes the hollow barrel to be crushed. The engagement of the rod-spring assembly in the cavity is preferably done by lowering the plastic part provided with said cavity in the direction of said rod carrying the spring. The invention also relates to any machine for mounting a helical spring in a molded part of a mechanism device, said part comprising a cylindrical cavity dimensioned to accommodate at least part of said spring and provided with a hollow barrel projecting from its bottom, characterized in that it comprises at least one punch-forming rod, provided with a shoulder, capable of receiving such a spring and means for engaging the rod-spring assembly in said cylindrical cavity up to

crushing of said hollow barrel.

  The end of the rod is substantially frustoconical to allow the formation of a bead of regular shape coming to fall back on the turn

  spring terminal. This operation is known as the bouterollage.

  The invention will be better understood and other advantages thereof

  will appear more clearly in the light of the description which follows, given

  by way of example only and with reference to the accompanying drawings in which: - Figure 1 is an exploded perspective view of the main elements of an electrical appliance, one of the parts of which carries a helical spring installed by using the method according to the invention; - Figures 2A-2C schematically illustrate the method of the invention applied to the mounting of the spring in a cavity formed in the molded plastic part of Figure 1; - Figure 3 is a detail view on a larger scale of the box III of Figure 2; and Figure 4 is an enlarged view of Box IV of the

figure 2.

  Considering more particularly FIG. 1, an electrical apparatus with mechanism 11 has been represented, which is here a rocker-type switch constituted by the assembly of several parts, some made of molded plastic, the others made of metal, in particular copper. or copper alloy. There is thus a plastic key 12 coming to be mounted on the upper part of a driver 13 which constitutes the plastic part to which the method of the invention is applied. This driver carries at least one helical spring 15, metallic. The coach laterally comprises two pins 16 which are engaged in two holes 17 forming rotational bearings of a first support 19 of molded plastic. This first support is fitted onto a second support 20 made of molded plastic and is assembled therewith by screws and / or shaped connections. The assembly of these two supports makes it possible to trap and hold in position automatic clamping connection terminals 22, 23 extended by fixed contact elements. These metal terminals are kept at a distance from each other between the two supports. Such terminals are for example described in patent application FR 97.12416. Terminal 22 has an extension 25

  V-shaped profile in which a movable contact element 27 is pivotally mounted.

  Part of this movable contact element forms a stud 27a capable of coming into contact with a fixed stud 23a defined in an extension of the connection terminal 23. This movable contact element 27 comprises a small lug 29 on which is positioned the free end of the spring 15 carried by the tilting driver 13. It is understood that the tilting of the driver causes, via the spring, the pivoting of the contact element 27 and that this movement is capable of establishing or not a electrical connection between connection terminals

22, 23.

  Figures 2 to 4 show better the structure of the molded part constituting the driver 13. It includes a hollow column 30 defining a cylindrical cavity 31 shaped and dimensioned to accommodate part of the spring 15, the problem being to maintain the spring in this cavity. It should be noted that the cavity defined in the baluster receives the spring 15 which cooperates

  with the movable contact element 27 to control the tilting thereof.

  However, the molded part constituting said driver also comprises two other lateral cavities 32, 33, of the same type, capable of accommodating

each a different spring.

  The presence of such a spring in a lateral cavity 32 or 33 makes it possible to return the coach to the initial position relative to the first support 19. In

  in this case, the electrical device is a switch of the "push button" type.

  Of course, the method of the invention can be applied to the establishment

  of a spring in one or other of these lateral cavities 32, 33.

  Such a cylindrical cavity is provided with a hollow barrel 35 projecting from its bottom. It is the deformation of this barrel which will allow the fixing of the spring

in the cavity.

  To do this, the spring 15 is engaged in the cavity so that its end surrounds the hollow barrel 35 and the said hollow barrel is crushed using a rod 38 forming a punch itself engaged longitudinally in the space delimited by the turns of the spring 15. This forms a bead 40 (Figure 4) retaining

the end of the spring.

  FIGS. 2A to 2C illustrate the process as well as the main elements of a machine implementing this process. Thus, a conveyor 45 (with rectilinear or rotary movement) comprises a certain number of rods 38 forming punches, each provided with a shoulder 46 on which the end of a spring 15 can come to rest. Each rod forming punch is kept upright vertically with said shoulder at the bottom and, when a rod is at a predetermined location, at a spring loading station, a spring 15 of this kind is engaged around the rod until its lower end rests on the shoulder. At the same time, the molded parts 13 are brought into a press, the movable part 48 of which moves to a location where the cylindrical cavity is located above the rod carrying the spring and along the axis thereof. The lowering of the movable part 48 carrying the molded part 13 causes the engagement of the rod-spring assembly in the cylindrical cavity 31 and this movement continues until the end of the rod 38 causes the crushing of the hollow barrel 35 at the bottom of this cavity. This is the situation illustrated in FIG. 2B and in FIG. 3. It is therefore the relative displacement between the molded part carried by the press and the rod integral with the conveyor, in the axial direction of said rod, which causes the crushing of said hollow barrel. In other words, the part is lowered after positioning it above the rod-spring assembly so that said

  cavity covers the spring installed on the rod.

  At another machine station (Figure 2C) the punch rod is removed from the cavity 31 and the plastic part can be routed, with the spring, to another assembly station where it will be assembled with other

  components of the electrical appliance.

  As seen in Figure 3, the end 38a of said rod is substantially frustoconical, which is favorable for the formation of a regular bead 40 trapping the last turn of the spring. One could however foresee that the end 38a is trunk-pyramidal. The bead 40 would then be less regular, but the impact more effective for the benefit of the deformation of the material.

Claims (8)

  1- Method of mounting a helical spring in a molded part (13) of an apparatus such as for example an electrical appliance of the switch type, said molded part comprising a cylindrical cavity (31) dimensioned to accommodate at least part of said spring and provided with a hollow barrel (35) projecting from its bottom, characterized by the operations consisting of engaging the spring in said cavity so that its end surrounds said hollow barrel and crushing said hollow barrel using a rod (38) forming a punch engaged longitudinally in the space delimited by the turns of said spring, so as to   forming a bead retaining the end of said spring.   2- A method according to claim 1, characterized in that a spring (15) is positioned around a rod (38) above provided with a shoulder (46) and in that one engages the rod-spring assembly in said cylindrical cavity by continuing this movement by force until the end (38a) of said rod   causes said hollow barrel to be crushed.   3- A method according to claim 1 or 2, characterized in that said rod (38) is held upright with said shoulder at the bottom, in that one engages a spring (15) above around said rod until that its lower end rests on said shoulder and in that one positions   said part (13) so that said cylindrical cavity (31) thereof is located   above said rod along the axis thereof and in that it causes a relative displacement between said part and said rod in the axial direction of   the latter until said hollow barrel is crushed.   4- A method according to claim 3, characterized in that said molded part is lowered (13) after positioning thereof, so that said cavity (31)   come over said spring (15) installed on said rod.   - Machine for mounting a helical spring in a molded part of a mechanism device, said part comprising a cylindrical cavity (31) dimensioned to accommodate at least part of said spring and provided with a hollow barrel projecting from its bottom , characterized in that it comprises at least one rod (38) forming a punch, provided with a shoulder, capable of   receive such a spring and means (45, 48) for engaging the rod assembly   spring in said cylindrical cavity until said hollow barrel is crushed.   6- Machine according to claim 5, characterized in that the end   (38a) of said rod is substantially frustoconical.   7- Apparatus according to claim 6, characterized in that the end   (38a) of said rod is substantially truncated pyramid.   8- Mechanism device, in particular an electrical device of the switch type comprising a spring (15) assembled to a molded part (13), the latter being provided with a cylindrical cavity (31) dimensioned to accommodate at least part of said spring (15 ), characterized in that said spring is fixed to the bottom of said cavity by means of a bead (40) resulting from the crushing of a hollow barrel (35) integral with the bottom of the cavity, by implementing the method   according to one of claims 1 to 4.   9- Apparatus according to claim 8, characterized in that said molded part (13) constitutes a drive of an electric switch, said spring (15) cooperating with a pivoting metal element (27) forming movable contact, for   cause it to tip over.