MORETTO, Maurizio (Piazza Araceli 2, Vicenza, I-36100, IT)
| CLAIMS 1. Personal weighing scales comprising a base and a platform for the body to be weighed, an electrically activated weighing and display device interposed between said base and said platform, and at least one capacitive proximity switch connected to the weighing and display device for controlling at least one function of the latter in operation, said switch including an electrode designed to monitor the capacitance in its environment, characterized in that said electrode is mounted on said base, is structurally separate from said load platform and is spaced apart from it. 2. Scales according to Claim 1, in which said proximity switch is designed to activate the scales. 3. Scales according to Claim 1 or 2, in which said electrode is mounted on an appendage projecting upwards from said base towards said platform. 4. Scales according to Claim 3, in which said appendage coincides with a support for fixing the weighing device. 5. Scales according to any one or more of the preceding claims, in which said electrode is mounted on the printed circuit base board of an electronic controller of said weighing and display device. 6. Scales according to any one or more of the preceding claims, in which said electrode is integrated on a surface of said proximity switch. 7. Scales according to any one or more of the preceding claims, in which a mark is applied to the platform, in the area immediately above the electrode, to indicate the position of the underlying electrode. |
DESCRIPTION
The present invention relates to personal weighing scales of the type having the features mentioned in the preamble of the principal claim.
An example of known scales including the aforesaid features is described in EP 1 371 954.
These scales use a capacitive proximity switch which activates the scales when a change of capacitance occurs in the proximity of an electrode of the switch.
These scales have the advantage of a simple system for cutting off and/or activating the power supply to the weighing and display device, which limits the electricity consumption of the scales. This appreciably increases the service life of any batteries which are used for the power supply.
However, the scales described in the aforesaid document have a considerable drawback in that, according to the patent, the electrode is fixed to either the upper or the lower surface of the platform.
This positioning results in two possible major drawbacks.
If the electrode is fixed to the upper surface of the platform, the cable which connects it electrically to the weighing and display device has to pass through the platform itself. However thin this connection may be, it will still be exposed to impact, abrasion and similar "external" effects which may degrade the electrical continuity of the connection.
It is also necessary to make a hole, even if it is very small, in the platform to pass the cable through it.
In the second case, both the electrode and its connecting cable are more effectively protected and the problem of passing the cable through the platform is avoided. However, the scales still present problems in respect of construction, particularly when the display device is fixed to the base of the scales rather than to the platform. This is because the electrode, which is located on the platform, has to be electrically connected to the weighing and display device, which is located on the base. In practice, the possibility of pre-assembling the whole of the electrical circuit part of the scales on to the base is substantially precluded, since further electrical connections to the electrodes of the platform are required. Since these connections are generally of the type known as "capillary", the difficulty is compounded by the capillary dimensions of the connection.
The invention is based on the discovery that, by contrast with the teachings of EP 1 371 954, it is possible to capture changes of capacitance in the vicinity of the electrode by increasing the capacitive sensitivity of the electrode, even if the latter is fixed to the base instead of the platform. Since the signal is inevitably attenuated by the greater distance between the electrode and the foreign body which perturbs the capacitance in the vicinity of the electrode, it is preferable to provide a marking on the part of the platform positioned immediately above the electrode, to identify the area in which the "perturbing" effect has to be created, in order to ensure that the change in capacitance is actually captured by the electrode so as to activate the desired function of the balance.
The technical problem which arises and which is tackled by the invention is therefore that of providing improved personal weighing scales which are structurally designed to overcome all the drawbacks mentioned with reference to the cited prior art.
This problem is resolved according to the invention by means of scales made in accordance with the appended claims.
The features and advantages of the invention will become clear from the following detailed description of some preferred examples of embodiment thereof, illustrated, for the purposes of guidance and in a non-limiting way, with reference to the appended drawings, in which :
Fig. 1 is a plan view from above of scales according to the invention;
Fig. 2 is a schematic sectional view taken along the line II- II of the scales of Fig. 1;
Figs. 3 to 6 are sectional views corresponding to Figure 2 of four other variant embodiments of the scales according to this invention. In the figures, the number 1 indicates, as a whole, personal weighing scales made according to the invention, including a base 2 and a platform 3 for the body to be weighed . Both the base 2 and the platform 3 are preferably made from a material which is not electrically conductive.
A weighing device indicated as a whole by 4 is interposed between the base 2 and the platform 3. The weighing device 4 comprises a load cell 5 whose opposite ends are fixed, by means of a support 6 and screws 7 at each end, to the base plate and to the platform respectively.
The weighing device 4 also comprises an electronic controller 8 connected to the load cell 5 in order to process the signal emitted by the load cell in relation to the deformation of the cell caused by the body placed on the platform, and a display 9 for displaying the value of the resulting measurement. A capacitive proximity switch 10 is connected by an electrical connection schematically indicated by 10a to the weighing device 4, and in particular to the controller 8, for the operational control of at least one function of the device. Preferably, the function which is controlled is the function of activating (switching on) and inactivating (switching off) the scales 1 for the purpose of inactivating them when they are not in use. In practice, the switch 10 can be used to control the activation function of the scales only, since their inactivation can be controlled either by means of a timer control device in the controller 8 or by means of a control device sensitive to a sudden decrease in the weight detected on the platform 3 due to the fact that a person has stepped off the scales.
The proximity switch 10 has an electrode 12, preferably incorporated in a surface of the switch which, after assembly, faces the platform 3. The proximity switch is designed to monitor the capacitance in the area surrounding the electrode.
Provision is made for the scales to incorporate a plurality of switches and/or a plurality of electrodes to control various functions of the scales. The proximity switch 10 and the electrode 12 are mounted on the base 2, are structurally separate from the platform 3, and are spaced apart from the latter.
A mark 12 is provided on the platform 3 at a point corresponding to the position of the electrode 12 (or of each electrode if a plurality of these is provided), in order to identify the position of the underlying electrode and indicate to the user the position of the electrode 12 if the latter is not visible through the platform 3. In the example in Figure 2, the electrode 12 is placed, together with the proximity switch, on a perimetric rib structure 13 of the base 2 in such a way that it is well protected against impact, accidental contact with foreign bodies and splashes of water. Alternatively, the mounting can be on the lower flat member 14 of the base 2 (Fig . 3).
In the example of Figure 4, the electrode 12 is mounted on an appendage which rises from the base 2 towards the platform 3, and which, in this case, is formed by the support 6 by means of which the load cell 5 is fixed to the base. It is also possible for the appendage to be formed separately on the base 2.
In a preferable variant of the invention, the switch 10 and the electrode 12 are mounted on the printed circuit board 15 which supports the electronic components of the controller 8 and/or of the display 9. This provides a further advantageous saving in the form of a radical simplification of the mechanical and electronic assembly of the scales 1, with the evident practical and economic advantages and the greater capacity for error prevention resulting therefrom.
In a final variant of the invention (Fig. 6), the base 2 is fixed to and suspended from the platform 3, and the scales bear on the ground with the load cells 5. In this case also, the switch 10 and the corresponding electrode 12 are fixed to the base 2.
The scales according to the invention operate in the following way. In electrical terms, the proximity switch 10 forms an open circuit and therefore it neither draws nor dissipates electrical energy. However, when a foreign body, such as part of the user's body (a foot, for example) approaches the electrode 12, there is a perturbation of the capacitance of the surrounding dielectric, which is detected by the electrode 12 and is measured in the switch 10 and/or the controller 8. As a result, the weighing system of the scales and the corresponding display are switched on. The scales can be designed in such a way that they can be switched off by means of a programmable timer or as a result of a sudden decrease in the load detected on the platform 3, due to the user's stepping off the platform, which is interpreted by the controller 8 as a control signal for switching off the scales.
Thus the invention resolves the aforementioned problem and offers numerous advantages by comparison with the prior art, including greater protection of the capacitive switch and of the corresponding electrode, and of its electronic connecting parts. Furthermore, the possibility of assembling the switch and/or its electrode directly on to the printed circuit board of the controller 8 makes the assembly of the scales even easier, safer and less error-prone.
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