Process for the production of an apparatus or instrument by overmolding and apparatus or instrument thus obtained

A process for the production of measuring apparatus or instrument by total or partial overmolding of its functional elements, particularly of its components and electric and electronic circuits. The process consists in arranging a support structure (2) carrying the functional elements (3, 3') and being adapted to be present particularly in the form of one or several cards or plates, in an injection mold (4), the support structure (2) being positioned in the mold (4) particularly by at least one element (5) in the form of a cap or shell on the support structure (2) and of which at least one wall portion (5') rests directly against the internal surface (4') of the mold (4), then injecting, after closing the mold (4), the thermoplastic material adapted to form the body (6) or at least a portion of the body (6) of the apparatus or the instrument (1) in question and covering entirely or partially the element or elements (5) in the form of a cap or shell, except the wall or wall portions (5') in contact with the internal surface (4') of the mold (4) and, finally, after solidification of the thermoplastic material, removing the apparatus or instrument (1) from the mold (4).

FIELD OF THE INVENTION
 The present invention relates to the field of the production of apparatus
 and instruments, more particularly those subjected to extreme conditions
 of use and/or cleaning, and has for its object a process for the
 production of an apparatus or instrument, as well as an apparatus or
 instrument, particularly of the electronic thermometer type, obtained by
 this process.
 BACKGROUND OF THE INVENTION
 Certain apparatus or instruments enclosing electrical and/or electronic
 components can be used under conditions of shock, exposure to liquids,
 disinfection and strong chemical and physical aggression.
 Such is particularly the case with electronic thermometers, particularly
 those used in a hospital environment.
 However, these instruments are at present produced by assembly, for example
 by screwing, welding or snapping in, of two half shells or by assembly of
 a single shell body with a cap, the printed card or circuit supporting
 functional elements being first introduced into the body of these
 instruments.
 As a result, there are joint lines and surface discontinuities, which
 constitute regions of weakness in terms of sealing, which can give rise to
 damage to the instrument, particularly when it is immersed for a prolonged
 period into a liquid, for example a disinfectant. Such instrument requires
 a long cleaning and disinfection time, which is troublesome for personnel
 in charge of this operation and for this reason often shortened.
 There are known moreover techniques of production of pieces or elements by
 overmolding by injection of thermoplastic material, permitting creating
 pieces and elements resistant to shocks, compact and relatively sealed,
 without requiring recourse to fastidious and economically undesirable
 assembly processes.
 However, the present overmolding techniques use wedging elements opening on
 the external surface of the overmolded piece and constitute
 discontinuities at this point, not permitting the overmolding of pieces
 sensitive to heat, or pressure, nor permitting a passage extending from
 the element to be overmolded to the external surface of the overmolded
 product. These techniques give rise to a large consumption of
 thermoplastic material, increasing the cost of production and the weight
 of the finished product.
 SUMMARY OF THE INVENTION
 The present invention has particularly for its object to overcome at least
 certain of the mentioned drawbacks.
 To this end, the present invention has for its object a process for the
 production of a measuring apparatus or instrument by total or partial
 overmolding of its functional and/or constituent elements, particularly of
 its components and electrical or electronic circuits, which comprises
 positioning the support structure carrying said functional elements and
 which can be present particularly in the form of one or several cards or
 plates, in an injection mold, said support structure being positioned in
 the mold particularly by means of at least one element in the form of a
 cap or shell provided on said support structure and of which a portion of
 the wall at least rests directly against the internal surface of said
 mold, then in injecting, after closing the mold, the thermoplastic
 material adapted to form the body or at least a part of the body of the
 apparatus or of the instrument in question and covering entirely or
 partially the element or elements in the form of a cap or shell, except
 the wall or walls or portions thereof in contact with the internal surface
 of the mold of this latter and, finally, after solidification of the
 thermoplastic material, extracting said apparatus or instrument from said
 mold.
 The invention also has for its object an electronic thermometer comprising
 a card or printed circuit supporting the functional elements and connected
 to a module for detecting temperature terminating in a probe, obtained by
 the preceding process.
 The invention will be better understood from the following description,
 which relates to a preferred embodiment, given by way of non-limiting
 example, and explained with reference to the accompanying schematic
 drawings, in which:

DETAILED DESCRIPTION OF THE INVENTION
 As shown in FIGS. 1, 2 and 4 of the accompanying drawings, the process for
 production according to the invention consists essentially in positioning
 the support structure 2 carrying said functional elements 3, 3' which can
 particularly be in the form of one or several cards or plates, in an
 injection mold 4. The support structure 2 is positioned in the mold 4
 particularly by means of at least one element 5 in the form of a cap or
 shell on said support structure 2 and whose one wall portion 5' at least
 rests directly against the internal surface 4' of said mold 4. Then, after
 closing the mold 4, one injects the thermoplastic material adapted to form
 the body 6 or at least a portion of the body 6 of the apparatus or
 instrument 1 in question. One then covers entirely or partially the
 element or elements 5 in the form of a cap or a shell, except the wall or
 walls or portions of walls 5' in contact with the internal surface 4' of
 the mold 4 of these latter. Finally, solidifying the thermoplastic
 material solidifies, and the apparatus or instrument 1 is extracted from
 said mold 4.
 The element 5 can accordingly, in certain cases, all by itself ensure
 maintenance of the support structure 2 in the mold 4 and will thus form
 the only overmolded element opening on the external surface of the
 apparatus or of the instrument 1.
 The wall or wall portion 5' could perform several functions, if desired
 cumulative, both technical and aesthetic.
 Thus, the wall or wall portion 5' of the cap or shell 5 in contact with the
 internal surface 4' of the mold 4 could be transparent over at least a
 portion of its surface and/or have a flexible texture over at least a
 portion of its surface.
 The mentioned arrangements permit arranging under said wall or wall portion
 5' signal indicators or display means, for example of the LED or LCD type,
 as well as control means of the button type or the like, permitting
 effecting an interactive connection between the user and the instrument or
 apparatus 1, without compromising the sealing of this latter.
 Moreover, by forming hollow cavities, said at least one element 5 in the
 form of a cap or shell permits reducing the quantity of thermoplastic
 material necessary for overmolding.
 Still further, so as to avoid any damage to the functional elements 3, 3'
 in the course of overmolding, given the temperatures of condition,
 pressure and speed of injection connected to this operation, said at least
 one element 5 provided in the form of a cap or shell constitutes with the
 corresponding card or plate 2 a substantially closed structure, insulating
 the circuit or circuits or sensitive components 3', particularly those
 sensitive to heat, from the hot injected thermoplastic material.
 When supplemental support of the card or plate 2 in the mold 4 is required,
 this latter may also comprise at least one wedge member 7 adapted to rest
 against the internal surface 4' of the closed mold 4 by means of a point
 contact or quasi-point contact, or not, after it is provided that the end
 of said wedge member 7 be visible or not (see particularly FIG. 1 of the
 accompanying drawings).
 According to a first modification of the invention, shown in FIGS. 1 to 3
 of the accompanying drawings, the injected thermoplastic material 12 forms
 substantially all of the body 6 of monobloc construction of the apparatus
 or instrument 1 and covers entirely the support structure 2, the
 functional elements 3 and the element or elements 5 in the form of a cap
 or shell, except the wall or walls or wall portions 5' in contact with the
 internal surface 4' of the mold 4 of these latter.
 So as to lighten the instrument or apparatus in question, and to be able to
 define a substantially constant cladding or overmolding layer, even in the
 case of an external shape of a greatly variable cross section, and to be
 able to balance the distribution of the mass of said apparatus or
 instrument 1, the process can consist in giving to the card or cards 2
 several elements 5, 8 constituting hollow closed structures or forming
 with the card 2 hollow closed structures, of which at least one is in
 contact with the internal surface 4' of the mold 4 and/or of which at
 least one covers at least one sensitive circuit or component 3' by
 insulating it from any contact with the injected thermoplastic material,
 adapted to form the body 6.
 According to a second modification of the invention, shown in FIGS. 4 and 5
 of the accompanying drawings, the element 5 in the form of a hollow shell
 can enclose substantially all the support structure 2 and delimit
 substantially the volume and the external shape of the body 6, the
 over-molded thermoplastic material 12 covering only the regions of joining
 and assembly of said shell.
 This latter could, as shown in FIG. 5 of the accompanying drawings, be
 formed of two half shells (upper and lower parts) assembled together at
 the level of a circumferential assembly line 13 by means of a snap-in or
 zigzag connection.
 Preferably, the element 5 in the form of a shell has, at the level of its
 regions of joining and assembly, particularly at the level of the assembly
 lines 13 of these different constituent portions, a configuration that is
 reinforced or depressed relative to the external shape of the body 6 as
 defined by the mold 4, permitting obtaining perfect sealing and mechanical
 strength because of the thickness of the resulting overmolded material.
 So as to ensure total sealing between the element 5 or the elements 5 and
 the thermoplastic material forming the body 6 nearest the external surface
 6' of the apparatus or instrument 1, each element 5 in the form of a cap
 or shell can have at the level of its side walls 5", for example, in the
 first modification, adjacent its wall or its wall portion 5' in contact
 with the internal surface 4, of the mold 4, at least one non-planar
 peripheral surface strip 9, comprising for example configurations in the
 form of ribs and grooves, forming sealing zigzag structure.
 Although the process of production can be used for the manufacture of
 various apparatus or instruments 1, it is particularly well adapted for
 the production of instruments or apparatus for measurement, particularly
 electronic thermometers or devices for similar measurements.
 Such an electronic thermometer will comprise a card 2 supporting the
 electrical and electronic components 3, 3' and a temperature detection
 module 10, connected to said card 2 and integrating a corresponding probe.
 This module 10 is encapsulated, first by overmolding the body 6 of the
 thermometer 1, in a shell 11 of suitable material, only a rear portion 11'
 of said shell 11, directed toward the card 2, being overmolded by the
 thermoplastic material forming the body 6.
 The temperature detecting module 10 could preferably be mounted on or
 connected to the card or plate 2 by rigid connection and thereby serve as
 a holding and wedging member of said card or plate 2 in the mold 4, its
 portion uncovered by the thermoplastic material being adapted to rest
 directly against the internal surface of said mold 4 and to be if desired
 pinched between the constituent portions of this latter or rest on the
 lower portion of the element 5 of shell shape.
 The present invention also has for its object an electrical or electronic
 apparatus or instrument having a body resulting from partial or total
 overmolding of its functional elements obtained by means of the process
 for production described above.
 Finally, the invention relates, moreover, as shown in FIG. 3 of the
 accompanying drawings, to an electronic thermometer 1 comprising a card or
 printed circuit 2 supporting its functional elements 3, 3' and connected
 to a temperature detecting module 10 integrating at least one probe. The
 body 6 of the thermometer 1 is formed by overmolding a thermoplastic
 material of a bio-compatible nature. The body 6 comprises at least one
 hollow cavity 6' each delimited, on the one hand, by the card or the
 printed circuit 2 and, on the other hand, by an element 5 in the form of a
 cap or shell disposed on said card or said printed circuit 2 and of which
 at least one wall portion 5' is not covered by the thermoplastic material
 and is flush with the external surface 6" of said body 6.
 The wall or wall portion 5' flush and uncovered by the thermoplastic
 material forming the body 6 is at least partially flexible and/or at least
 partially transparent. The element 5 in the form of a cap or shell extends
 from above at least one component or circuit 3' sensitive particularly to
 heat and/or at least one component or circuit of luminous or sonar
 signaling, such as indicators, a display screen, a vibrator, a beeper or
 the like.
 As a modification, and as shown in FIG. 5 of the accompanying drawings, the
 body 6 of said thermometer 1 is essentially constituted by an element 5 in
 the form of a hollow shell, overmolded at the level of the lines of
 assembly of its constituent portions and of its joint zones with the
 detector module 10 with a thermoplastic material 12. These regions or
 lines are as the case may be located set back relative to the external
 surface or body 6 or to the bottom of a groove. The thermoplastic material
 12 covers these zones or lines in a manner to constitute an external
 surface contiguous with the external surface of the adjacent portions of
 the element 5 in the form of a shell.
 According to one characteristic of the invention, shown in FIG. 3 of the
 accompanying drawings, the temperature detecting module 10 is encapsulated
 in a shell 11 of a suitable material of which only one rear end portion
 11' is covered by the thermoplastic material of overmolding.
 The rear end portion 11' could also comprise configurations of grooves and
 ribs, adapted to permit a solid and sealed connection by imbrication
 between the overmolded body 6 and the shell 11 covering and enclosing the
 module 10, the thermoplastic material being preferably able to form a
 joint with an external lip.
 The shell 11 could itself be of the overmolded type and made of a material
 which is a good conductor of heat.
 As already indicated above, the overmolded body 6 could preferably comprise
 several hollow cavities 6' delimited by hollow closed elements 8 and/or in
 the form of a shell or cap 5 provided on the card or printed circuit 2, of
 which at least one is flush at the level of its external surface 6" with
 the body 6 and/or encapsulates at least one sensitive component 3'.
 Preferably, the electronic thermometer 1 described above is obtained by
 means of the process of production described above, as well as the
 finished product made by molding and having a rounded outer shape,
 substantially without reinforcement and without crevices.
 Of course, the invention is not limited to the embodiments described and
 shown in the accompanying drawings. Modifications remain possible,
 particularly as to the construction of the various elements or by
 substitution of technical equivalents, without thereby departing from the
 scope of protection of the invention.