FR2855263A1 - Electronic scales for personal or household use has top panel with rigid support covered with supple thermoformed plastic material - Google Patents

Abstract

The scales (1) consist of a panel (10) to receive the object being weighed, supported by a base with feet (4) and extensometric bars, and having a window for a display (6). The panel is in the form of a rigid support, e.g. for wood, metal or glass, and is covered at least partly with a supple thermoformed plastic material attached to it by adhesive.

Description

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  WEIGHING APPARATUS AND MANUFACTURING METHOD THEREOF

  The present invention relates to a weighing device of the weighing person, baby weighing scale or household scale type, in particular of the electronic type comprising strain gauges associated with an electronic measuring circuit delivering a signal which is a function of the weight to be measured. and it relates more particularly to the structure of such an apparatus.

  A weighing device in principle comprises a plate capable of receiving the weight to be measured, at least one test body comprising on one face of the strain gauges, one of the ends of this body being connected to the plate and the other to a base or a foot intended to rest on a flat surface. The two ends of this body are embedded in the plate and the base and they delimit a bar made of an elastic material supporting the strain gauges and deformable essentially by bending under the effect of the weight to be weighed.

  The gauges are connected to an electronic circuit to convert the deformations undergone by the gauges into electrical signals and transform the latter into digital values corresponding to the measured weight. The weighing plate is generally made of a rigid material, capable of supporting compression and tensile loads in order to resist without deformation to the load applied. Such a weighing pan material can be glass, wood, stone, steel, aluminum. Other devices have a rigid frame on which is mounted, by means of a screw, clip or glue attachment, a cover made of a plastic material of the ABS, PS, POM, etc. type. These trays or covers are sometimes covered with cloth or rubber mats which are fixed or removable mounted on the upper face of the tray or cover for the purpose of comfort or to facilitate cleaning. Such carpets of flexible material do not lend themselves well to the shapes and curves of the weighing plates or covers which, moreover, must have quality finishes.

  Document FR 2 417 756 describes a scale comprising a rigid plate, the upper surface of which is covered with a carpet of textile material or of a foam plastic which is fixed removably relative to the plate, the covering plate having openings. which fit into the projections provided for this purpose on the plate. Such a solution can only be applied to 5 flat or very slightly curved weighing plates, the coating being unable to follow pronounced curves corresponding to the shape of the arch of the foot. In addition, the protruding parts of the coating adversely affect the feeling of comfort of a user standing on such a tray.

  Document US Pat. No. 5,434,367 describes a household balance comprising a protective cover made of a flexible material which is removably mounted by means of adhesive disks on the platform of the balance. The protective cover comprises a body of a foam-like material wrapped in a plastic film. This cover provides a damping and protection role for the 15 fragile objects in contact with the rigid plate. Such a protective cover is of the disposable type, it does not resist humidity and it is not suitable for use with a device comprising a raised tray.

  The object of the present invention is to remedy, at least in part, the abovementioned drawbacks and to provide a scale with good weighing comfort and quality finishes for optimized manufacturing costs.

  Another object of the invention is a weighing apparatus comprising a rigid weight receiving plate, of complex shape, which has good weighing comfort over its entire surface, while being of simplified construction.

  Another object of the invention is a weighing device comprising a weight receiving tray having good weighing comfort, which withstands well the attacks of the external environment and which is capable of being easily cleaned.

  These purposes are achieved with a weighing device comprising a weight receiving plate supported by a weighing base or a base, said weight receiving plate comprising a rigid support covered on at least part of its surface by a coating, that said coating is a flexible plastic material shaped by thermoforming and deposited on said support.

  By weight receiving tray comprising a rigid support, it is understood that it is made of a material having good tensile and compression resistance, capable of supporting the maximum weight admitted by the device without deforming. This tray is supported by a weighing base comprising the 10 weight sensors or by a base containing the measuring device.

  More particularly according to the invention, this rigid support is covered by a coating of a flexible plastic material shaped by thermoforming on said support. Thermoforming consists in heating a sheet or a plate to a temperature allowing its deformation in a mold whose shape it takes on by the action of a pressure difference between its two faces.

  In a first embodiment of the invention, the rigid support and the covering, which is preferably in the form of a sheet of flexible plastic material, are placed together inside the chamber of a press. thermoforming where the coating is shaped by heating the coating sheet and creating an air depression on the latter.

  Under the influence of heat and pressure during thermoforming, the coating material then undergoes progressive stretching following the shape of the mold or that of the rigid support whose profile it follows. After cooling, a coating is obtained which can envelop, preferably, the upper surface and the lateral edge of the rigid support for a very precise finish, defined by the precision of the mold surface. As will be described later, in this embodiment, the surfaces of the tray and of the plastic coating which are in contact are preferably coated beforehand with an adhesive (generally a hot-reactivatable adhesive) which will ensure cohesion between the two elements after shaping. In addition, by such a thermoforming technique, it is possible to adhere a plastic coating to a rigid support of complex shape, even if the latter comprises a negative draft or a lower re-entrant edge. For example, the general shape of the plate can be other than rectangular: pseudo rectangular with convex or concave edges, oval, octagonal, or even in double lobe.

  In a second embodiment, the coating is produced by thermoforming in a mold adapted to the profile of the weighing pan and it is then transferred to a rigid support, for example using an adhesive support.

  Thus, particular finishes can be obtained giving a specific grain to the coating and desired aesthetic aspects, by machining in conformity the internal surface of the mold. Above all, whatever the general shape of the tray, thermoforming makes it possible to protect the edge of the tray by not letting appear any creases, potential seat of dirt. 15 A plate is thus obtained having a rigid support and covered with a thermoformed plastic coating on said support which is capable of ensuring both the rigidity necessary for weighing and the comfort of weighing, resistance to external agents, as well as good cleanability. The weighing comfort qualitatively results in a contact surface that is pleasant to the touch and, for a scale, in an ability of this material to conform to the arch of the foot. Such a plastic material therefore gives a pleasant surface to the touch, while conforming to the arch of the foot, for example, as defined by the configuration of the rigid support. Preferably, said coating is applied to said support by a thermoforming technique with the interposition of a deposit of adhesive.

  During the tests carried out, it was found that a deposit of adhesive on the surface 30 of the rigid support intended to receive the coating sheet, allowed better adhesion of the coating to the support during thermoforming. Such an adhesive can be, for example a polyurethane adhesive in the aqueous phase.

  Thus, the heating which takes place inside the thermoforming mold has the effect of reactivating the adhesive present on the rigid support, the coating therefore being first glued to the rigid support, the geometry of which it then follows.

  Advantageously, the material of said coating is chosen from the group comprising: thermoplastic olefin and polyvinyl chloride.

  Such a material of amorphous structure is sufficiently flexible to have a contact surface pleasant to the touch, good resistance to wear and to the external environment, while easily lending itself to shaping by thermoforming on a rigid support, c that is, it can provide the required thermoforming depth and a good production rate. However, the olefin thermoplastic is preferred for its more pleasant tangential touch properties.

  Such a material is preferably deposited in the form of a sheet on the rigid support, the thickness of this sheet possibly being between 0.1 mm and 3 mm.

  The heating temperature of such a coating is high enough to soften it so that it can be formed by vacuum, but low enough to prevent pouring or deterioration of the coating material. This temperature can advantageously be between 80 and 150 C.

  In an advantageous variant of the invention, the plate of the device comprises at least one layer of damping material arranged between said support and said coating over all or part of its surface. Such a damping material deforms elastically under the action of the weight applied to the platform, which gives even more comfort or protects more fragile objects placed on the platform of the weighing device.

  Usefully, said layer of damping material forms a support sole.

  Such a support sole constitutes a seat part of the feet of an individual when he stands upright on the platform of the weighing device. It is therefore possible to provide only two damping zones on the pan and not a continuous layer, which makes it possible to maintain a thin profile of the weighing pan.

  Advantageously, said sole is made of a material chosen from the group comprising: silicone gels, neoprene foams or polyethylene foams.

  Such a material has good flexibility for relatively small thicknesses subjected to forces such as generated by the weight of a person.

  In a second embodiment of the invention, said coating has a multilayer structure, comprising a first and at least a second layer, two adjacent layers being separated by a binder.

  A multilayer structure is obtained by combining at least two layers of different materials separated by a layer of binder. The laminating of such a set of materials, called lamination, makes it possible to combine several materials with different properties and to obtain a wider range of properties for the set. The thermoforming temperature of the assembly should then take account of the individual temperatures of each component, in particular it should be slightly higher than that of melting or glass transition of each of the materials constituting the multilayer. Preferably, the first layer of said coating is made of a material chosen from the group comprising: the thermoplastic olefin and polyvinyl chloride.

  Thus, this first layer, by its aforementioned properties, could advantageously form the outer layer of the coating applied to said rigid support.

  Advantageously, the second layer of said coating is made of a material chosen from the group comprising: polyethylene foams, polyurethane foams, polypropylene foam.

  Such materials have good properties of flexibility, suppleness, which further increases the feeling of weighing comfort, while guaranteeing a thin profile of the platform of the weighing device, these materials being advantageously made of sheets of thickness. between 2 and 30 mm.

  In an advantageous variant of this embodiment, the platform of the weighing device comprises at least one layer of damping material arranged between said support and said coating.

  Such a damping material elastically deforms under the action of the weight applied to the platform, which gives even more comfort or protects more fragile objects placed on the platform of the weighing device.

  Advantageously, said layer of damping material can be associated with another layer of damping material forming a support sole.

  Such a support sole constitutes a seat part of the feet of an individual when he stands upright on the platform of the weighing device. It is therefore possible to provide only two damping zones on the pan and not a continuous layer, which makes it possible to maintain a thin profile of the weighing pan.

  Preferably, said sole is made of a material chosen from the group comprising: silicone gels, neoprene foams or polyethylene foams.

  Such a material has good flexibility for relatively small thicknesses subjected to forces such as generated by the weight of a person. The feeling of comfort can be declined by varying the density or the hardness of such a material.

  Usefully, the material of said rigid support is chosen from the group comprising: plastic, wood, aluminum, steel and glass.

  Such a material provides the rigidity necessary for weighing, for a fairly thin profile of the rigid support and easily lends itself to the deposition by thermoforming of a coating of a plastic material.

  Preferably, said rigid support has a plate shape and said coating covers the upper face and at least partly the peripheral edge of said support.

  This makes it possible to have a weighing pan with pleasant contact to the touch over the entire weighing surface formed by the upper face of the rigid support, or even on the peripheral border which is sometimes used as a means of gripping the device.

  In a variant, the peripheral edge of said support includes a re-entrant edge also covered by said coating.

  This provides a high finish of the weighing pan on its visible parts. In addition, by affixing it to a base comprising a lower cover fixed to the weighing pan, lateral continuity of the pan is ensured thereby protecting the measuring device located inside and avoiding a deposit of dust over time.

  In another variant, the periphery of said covering is folded and fixed on a side not covered with covering of said support.

  In this variant, as in the previous one, lateral continuity of the platform of the weighing device is ensured, with reinforced protection of the latter and of the measurement device against attack by the external environment.

  Another object of the invention is also a first advantageous method of manufacturing a weight receiving plate for a weighing device, comprising the following steps: - producing a rigid plate support comprising an upper face, a lower face and an edge peripheral; - apply a layer of glue over the entire surface which will be in contact with the flexible material; - placing a covering sheet on said upper face; - Place the support and covering sheet assembly inside the chamber of a thermoforming press, said lower face being oriented in the direction of exit of the sucked air; - Thermoforming by heating the coating and creating a vacuum inside the mold.

  In a variant, it is possible to envisage an additional step residing in leveling the periphery of said coating which protrudes relative to said peripheral border.

  In a second embodiment, the manufacturing process comprises the following steps: - producing a rigid tray support comprising an upper face, a lower face and a peripheral edge; placing the covering sheet inside a vacuum mold of a shape adapted to that of said upper face; - thermoforming by heating inside the mold; - Transfer by sewing a cable around the periphery of said covering which protrudes relative to said peripheral border; - Place said coating on the rigid support; tensioning said cable; - staple said cable to the underside of said support.

  An additional step of applying a layer of adhesive on at least said upper face of said rigid support can also be envisaged before placing the coating on the rigid plate.

  The invention also relates to a weighing apparatus comprising a weight receiving plate produced according to the method described and supplemented with a weighing base or a base.

  The invention will be better understood from the study of the embodiments taken by way of no limitation and illustrated in the appended figures in which: - Figures la to lc show, in perspective views, different stages of the assembly process a weighing device comprising a weight receiving plate according to the invention; FIGS. 2a to 2d show, in perspective views, different steps of the process for manufacturing a weight receiving plate of the weighing apparatus according to a first embodiment of the invention; Figures 3a to 3d show, in partial sectional views, different stages of the manufacturing process of the plate shown in Figures la to 1d and its assembly with a lower cover; - Figures 4a to 4d illustrate, in perspective views, a manufacturing variant of the plate shown in Figures la to 1 d; - Figure 5 shows an alternative embodiment of the coating before its shaping for deposition on the platform of the weighing device; - Figures 6a to 6c show, in perspective views, the different stages of the process for manufacturing the weighing pan of a weight receiving pan of the weighing apparatus according to a second embodiment of the invention ; - Figures 7a to 7f show, in perspective views, different additional steps of the manufacturing process according to the second embodiment of the invention; - Figures 8a to 8d show, by partial sectional views, different stages of the manufacturing process of the plate shown in Figures 7a to 7f and its assembly with a lower cover.

  The weighing apparatus 1 of the invention, as shown in FIGS. 1 a and 1 b, comprises a plate 10 capable of receiving the weight to be measured, plate 10 which is supported by a weighing base 3 comprising four feet 4 5 each containing a weight sensor. Such a weight sensor generally comprises a flexion bar with strain gauges, flexion bar mounted cantilevered between a part of the foot 4 coming into contact with the plate 10 and another part of the foot 4 bearing on the ground. . The strain gauges are mounted on one of the faces of the flexion bar and are connected by a Wheatstone bridge assembly to the electronic control circuit of the apparatus to convert the deformations undergone by the gauges into electrical signals, transform these into numerical values corresponding to the measured weight and display them. In this example, the weighing base 3 comprises four feet 4 connected in pairs by two rigid crosspieces 5, 15 parallel, crosspieces 5 containing the connections between the weight sensors and between them and the central control unit of the device . The two pairs of sensors are connected on one side by a box 8 containing a display device 6 and the rest of the connections. Such a construction tightly and compactly encloses all the electrical and electronic components of the device in a weighing base assembly 3.

  FIG. 1c shows the assembly of the plate 10 with the weighing base by bonding the upper surface of the legs 4 to the underside of the plate 10 to thereby obtain the weighing device assembly 1. As a variant, the weighing base or 25 the measuring device can be included inside a base comprising a cover 9 (fig.3d and 8d) fixed to the plate 10 by a fixing of the screw type or by clipping.

  In an advantageous embodiment of the invention, the plate 10 for receiving the weight of the weighing apparatus comprises a rigid support 12 (fig.2a) made, for example of wood or steel or aluminum or glass, by cutting and machining on a numerically controlled machine. The support 12 can also be made of molded wood or metal in order to simplify the machining of complex shapes. Such a support has the general form of a plate of thickness preferably between 4 mm and 35 mm. A window 7 is made in said support to reveal the display device 6 located below. To simplify assembly, the support may not have a window, the display system is then removed from the weighing pan.

  The coating used to cover the rigid support is a flexible plastic material, preferably olefin thermoplastic or polyvinyl chloride, in the form of a pre-cut sheet or in the form of a film roll, with a thickness of approximately 0.1 to 3 mm.

  Figures 2a to 2d show a method of manufacturing a tray 10 of the scale of the invention according to a first embodiment. Thus, in FIG. 2a, there is a first step which consists in making the support 12 15 as previously described and in applying to it a layer of adhesive on the upper face 17 and on the periphery of the peripheral border 18, or even on all the surfaces will receive the coating. FIG. 2b shows a second step consisting in cutting, from a roll 15 of coating material 14, a sheet having dimensions greater than the surface of the support which it must cover. The covering sheet 14 is placed on the upper face 17 of the support 12. In FIG. 2c is shown the step in which the thermoforming of the covering 14 takes place on the rigid support 12 and the reactivation of the adhesive. For this, the assembly formed by the support 12 and the coating 14 is placed inside a thermoforming press. A vacuum and heating system are activated, or the vacuum at the rear of the support plate allows atmospheric pressure to act on the coating 14, which has the effect of pressing the flexible material of the coating on the support 12 rigid by deforming it progressively and continuously around the periphery of the support 12. FIG. 2d shows the finished plate 10, covered on its upper face, including on the walls of the window 7, as well as on its peripheral edge 18 by the coating 14 (the coating 14 formed by thermoforming on the support 12 has been highlighted by hatching in Figures 2c and 2d, as well as in Figures 3a to 3d).

  FIG. 3a shows a sectional view of the edge of the support 12 comprising a lower re-entrant edge 19, the support 12 being coated with glue on its upper face 17, on the periphery of the peripheral edge 18 and on the periphery 5 of the lower re-entrant edge 19. When the coating 14 is thermoformed (fig. 3b), a vacuum and heating system is activated, which has the effect of pressing the flexible coating optimally on the rigid support by deforming gradually and continuously on said support. The flexible covering 14 has thus perfectly matched the geometry of the rigid support 12. In FIG. 3c is represented an additional step consisting in leveling, with the aid of a cutting tool 11, the periphery of said covering which protrudes with respect to said border peripheral 18 and the lower reentrant edge 19. FIG. 3d shows a step of assembling the cover 9, enclosing the measuring device, with the plate 10, making it possible to obtain lateral continuity of the device avoiding dirty deposits.

  FIGS. 4a to 4d show an alternative embodiment of the invention o the rigid support 12 comprises two elongated cavities 23 which are parallel to each other, capable of receiving two support flanges 22. The support flanges 22 are made in one cushioning material such as silicone gel, neoprene foam or polyethylene foam with a thickness of approximately 10 mm. These soles are advantageously embedded inside the support in order to preserve its thin profile (fig.4a). FIG. 4b shows a covering sheet 14 which is affixed to the support 12 comprising the soles 22, after having previously glued the surfaces intended for contact with the covering 14 of the support 12.

  The assembly is then shaped by thermoforming (fig. 4c) as previously described, the finished product being visible in FIG. 4d (the coating 14 formed by thermoforming on the support 12 has been highlighted by hatching on the Figures 4c and 4d).

  Figure 5 shows a coating material having a multilayer structure.

  Such a structure is obtained by complexing several different flexible materials. Thus, the roll 15 of flexible coating forms a first layer 14 ′, in particular of olefin thermoplastic, this roll being unrolled and assembled in a sandwich and by gluing, as it takes place, with a first film of a polyethylene foam forming a second layer 25 and / or with a second film of polyurethane foam forming a third layer 26.

  Such a coating with a multilayer or complexed structure is formed by thermoforming in a mold of a shape adapted to that of the support 12, according to a second embodiment of the invention (a shaping by thermoforming inside the chamber of a thermoforming press according to the first embodiment of the invention can also be envisaged for such a coating with a multilayer structure). Such a method according to the second embodiment of the invention is shown in Figures 6a to 6c. The cover sheet 27 is placed in a thermoforming mold having a cavity for receiving said assembly which conforms to the negative of the shape of the tray when it is finished. The internal surface of the mold cavity includes a precision finishing which can be a smooth surface, or even grained or textured according to a particular pattern with advantageous aesthetics. The thermoforming step is represented in FIG. 6a, FIG. 20 6b showing a cutting of the edges of the coating 27 which protrude laterally with respect to the limits of the receiving support of the weighing device tray, and FIG. 6c shows a coating 27 obtained by thermoforming with a view to transferring it to a rigid support of the weighing device.

  Figures 7a to 7f and Figures 8a to 8d show additional steps to fold and fix the edges of the covering 27 of Figure 6c, on the underside 20, not covered with coating, of the support 12. In Figure 7a we find the coating 27 shaped by thermoforming of FIG. 6c 30 to which is applied, by sewing (FIG. 7b), in particular on the periphery of the edges 28 of the latter, a border 29 which incorporates a cable 30 which can withstand a fairly high tension. The covering 27 is then placed with or without bonding on a rigid support 12 (FIG. 7c), in particular on the upper face 17 of the latter. The cable 30 is then tensioned (fig. 7d), which has the effect of pressing the coating 27 on the rigid support 12. The two ends of the cable 30 are then stapled to the underside 20 of the support 12 (fig. 7e and 8c). A cover 9 is then fixed in the lower part of the plate 10 thus obtained (fig.7f) and hides the border and the cable (fig. 8d).

  Such a coating deposit 27 based on complexed material makes it possible to obtain comfortable weighing platforms on all of their surfaces.

  Other variants and embodiment of the invention can be envisaged

  without going beyond the scope of its claims.

  Thus, it is possible to integrate a layer of damping material, in particular an additional layer of foam between the complex covering and the rigid support to further improve the feeling of comfort.

  This layer of additional foam can cover the entire surface of the rigid support or can be applied in the form of two support flanges.

Claims (20)

B.0609 CLAIMS   1. Weighing apparatus comprising a plate (10) for receiving weight supported by a weighing base (3) or a base, said plate (10) for receiving weight comprising a rigid support (12) covered on at least one part of its surface by a coating (14,27), characterized in that said coating (14,27) is a flexible plastic material shaped by thermoforming and deposited on said support.   2. Weighing apparatus according to claim 1, characterized in that said coating (14) is applied to said support (12) by a thermoforming technique with the interposition of a deposit of adhesive. 15 3. Weighing device according to one of the preceding claims, characterized in that the material of said coating (14) is chosen from the group comprising: thermoplastic olefin and polyvinyl chloride.   4. Weighing device according to one of the preceding claims, characterized in that it comprises at least one layer of damping material arranged between said support (12) and said coating (14) over all or part of its surface. .   5. Weighing apparatus according to claim 4, characterized in that said layer of damping material forms a support sole (22).   6. Weighing device according to claim 5, characterized in that said sole (22) is made of a material chosen from the group comprising silicone gels, neoprene foams or polyethylene foams.   7. Weighing device according to one of claims 1 or 2, characterized in that said coating (27) has a multilayer structure, comprising a first layer (14 ') and at least a second layer (25, 26), two adjacent layers being separated by a binder.   8. Weighing device according to claim 7, characterized in that the first layer (14 ') of said coating is made of a material chosen from the group comprising: the thermoplastic olefin and polyvinyl chloride.   9. Weighing apparatus according to claim 7, characterized in that the second layer (25, 26) of said coating is made of a material chosen from the group comprising: polyethylene foams, polyurethane foams, polypropylene foams.   10. Weighing apparatus according to one of claims 7 to 9, characterized in that it comprises at least one layer of damping material arranged between said support and said coating.   11. Weighing apparatus according to claim 10, characterized in that said layer of damping material can be associated with another layer of damping material forming a support sole. 20 12. Weighing device according to claim 11, characterized in that said sole is made of a material chosen from the group comprising: silicone gels, neoprene foams or polyethylene foams.   13. Weighing device according to one of the preceding claims, characterized in that the material of said rigid support (12) is chosen from the group comprising: plastic, wood, aluminum, steel, glass.   14. Weighing device according to one of the preceding claims, characterized in that said rigid support (12) has a plate shape and that said coating (14,27) covers the upper face (17) and at least in part the peripheral edge (18) of said support.   15. Weighing device according to claim 14, characterized in that the peripheral edge (18) of said support comprises a lower re-entrant edge (19) also covered by said coating (14,27).   16. Weighing apparatus according to claim 14, characterized in that the periphery of said coating is folded and fixed on a side not covered with coating of said support.   17. Method for manufacturing a weight receiving tray for a weighing device, characterized in that it comprises the following steps: - producing a rigid tray support comprising an upper face, a lower face and a peripheral border ; - apply a layer of glue over the entire surface which will be in contact with the flexible material; - placing a covering sheet on said upper face; - Place the support and covering sheet assembly inside the chamber of a thermoforming press, said lower face being oriented in the direction of exit of the sucked air; thermoforming by heating the coating and creating a depression inside the mold.   18. The manufacturing method according to claim 17, characterized in that it comprises an additional step residing in leveling the periphery of said coating which protrudes relative to said peripheral border. 25 19. A method of manufacturing a weight receiving tray for a weighing device, characterized in that it comprises the following steps: - producing a rigid tray support comprising an upper face, a lower face and a peripheral edge; - Place the covering sheet inside a vacuum mold of a shape adapted to that of said upper face; - thermoforming by heating inside the mold; - Transfer by sewing a cable around the periphery of said covering which protrudes relative to said peripheral border; placing said coating on the rigid support; - tensioning said cable; - staple said cable to the underside of said support.   20. Weighing device characterized in that it comprises a weight receiving plate produced according to the method of one of claims 17 to 19 supplemented with a weighing base (3) or a base.