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(11) | EP 4 459 650 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | MICROSWITCH AND RELATED PRODUCTION PROCESS |
| (57) A microswitch comprises a case (11) formed by at least two half-shells (35, 36) mutually joined at respective mutually facing and overlapping perimeter edges to
define a compartment (12) which houses a first electrical contact (15), a second electrical contact (16) and a contact element (19) movable with respect to the first electrical contact (15) and to the second electrical contact (16) and wherein the two half-shells (35, 36) are stably joined together by at least partial mutual welding of the respective
perimeter edges.
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Technical Field
[0001] The present invention refers to a microswitch and to the related manufacturing process, which can find application for the opening and closing of an electrical circuit of an industrial plant, or of any machine or device, in response to a pressure applied by the outside on the microswitch.
State of the art
[0002] Microswitches are known which normally comprise a case defining an inner compartment wherein a movable electrical contact and two fixed electrical contacts connected to respective outer electrical circuits are arranged.
[0003] Furthermore, the known microswitches also comprise a driving head, arranged outside the case, and suitable for receiving a mechanical pressure to be transmitted to the movable electrical contact and make it move between the fixed electrical contacts, opening or closing the electrical circuits to which the latter are connected. Generally, the case of known microswitches comprises two shells fixed to each other by means of screws, rivets, bolts, or other similar fastening elements, or by means of a joint obtained with a shape coupling.
[0004] In addition, in some cases it is required that the compartment inside the case is hermetically sealed to prevent water, dust or similar elements from reaching the electrical contacts located inside and causing their malfunction.
[0005] To this purpose, known microswitches usually comprise a gasket arranged between the two shells of the case to prevent water, dust or anything else from leaking into the inner compartment of the case, passing through the contact area between the two shells.
[0006] A drawback of known microswitches is represented by the fact that, although they include a gasket, perfect hermetic closure of the inner compartment of the case is not always guaranteed. As matter of fact, during the assembly operations of the microswitch, it is typical for the gasket not to be positioned perfectly in its seat, preventing the two shells of the case from being correctly fixed together.
[0007] Another drawback consists in the fact that the screws, rivets, bolts, or other fastening elements of the two shells, or even the shape coupling itself between the two shells, occupy a high volume and consequently limit the available volume of the compartment inside the case.
[0008] This drawback limits the dimensions of the electrical contacts housed in the inner compartment of the case and, therefore, also the electric currents to which they can be subjected, effectively limiting the applications of use of the microswitch.
[0009] This problem is aggravated in cases where the gasket is also provided between the two shells of the case. In fact, the housing for the gasket, and the gasket itself, occupy a portion of the volume of the inner compartment of the case, still limiting the available volume for housing the electrical contacts.
Scope of the invention
[0010] The object of the present invention is to realize a microswitch, and a related manufacturing process, which can overcome the above-mentioned drawbacks of the microswitches of the prior art.
[0011] A particular object of the present invention is to realize a microswitch having a ratio as close to unity between the volume of the inner compartment of the case and the overall volume of the microswitch.
[0012] Another object of the present invention is to realize a microswitch to be used for applications wherein very high electric currents are expected.
[0013] Another object of the present invention is to realize a microswitch simple to be manufactured, with compact dimensions and a high degree of sealing of the inner compartment of the case.
[0014] A further object of the present invention is to develop a process for manufacturing a microswitch which allows the reduction of fixing errors between the shells of the case. These objects, as well as others which become more apparent hereinafter, are obtained by a microswitch which, in accordance with claim 1, comprises a case formed by at least two half-shells mutually joined with each other at respective peripheral edges facing each other and overlapping for define a compartment which houses thereinside a first electrical contact, a second electrical contact and a contact element movable with respect to said first electrical contact and said second electrical contact and wherein said at least two half-shells are stably joined together by at least partial mutual welding of the respective perimeter edges.
[0015] In this way, as there are no external fastening elements or shape couplings, there will also be no elements that will occupy the inner space of the compartment, allowing for more space available for the contacts.
[0016] As a consequence, the contacts may have sections of increased width compared to known solutions but without it being necessary to increase the overall dimensions of the microswitch.
[0017] Therefore, the microswitch, while maintaining relatively small dimensions and high construction simplicity, may also be used in applications involving electrical currents of relatively high amperage.
[0018] Advantageous embodiments of the microswitch are obtained in accordance with the dependent claims.
Brief disclosure of the drawings
[0019] Further features and advantages of the invention will become more apparent in light of the detailed description of a preferred but not exclusive embodiment of a microswitch, shown by way of non-limiting example with the aid of the attached drawing tables in which:
Fig. 1 is an axonometric view of a microswitch according to an embodiment of the present invention;
Fig. 2 is a view of a portion of the microswitch of Fig. 1;
Figs. 3, 4 and 5 are sectional views of the microswitch of Fig. 1 according to section planes III, IV and V, respectively;
Fig. 6 is a sectional view of a detail of the microswitch of Fig. 1;
Fig. 7 is an axonometric view of a microswitch in accordance with an embodiment of the present invention;
Fig. 8 is a view of a portion of the microswitch of fig. 7.
Best mode of carrying pout the invention
[0020] A microswitch according to the present invention, generally referred as 10, is designed to be connected to one or more outer electric circuits and to open or close the latter in response to a pressure received from an external member.
[0021] In particular, with reference to Fig. 1, the microswitch 10 comprises a case 11 defining inside a compartment 12 wherein two or more electrical contacts 15, 16, adapted to be connected to the above one or more electrical circuits, are arranged.
[0022] In the present example, the microswitch 10 comprises a first electrical contact 15 and a second electrical contact 16, which in the illustrated configuration are fixed inside the compartment 12.
[0023] Each electrical contact 15, 16 is associated with a respective connection terminal 15', 16' to allow the connection thereof to respective outer electrical circuits.
[0024] By way of example, the connection terminals 15', 16' may be of the faston type, screw type, cable lug type, or other similar types.
[0025] Inside the compartment 12 there is also a contact element 19, movable with respect to the electrical contacts 15,16 between a first position and a second position and adapted to operate on the electrical contacts 15, 16 to open or close the electrical circuits connected thereto.
[0026] The movable contact element 19 is also associated with a connection terminal 19' to electrically connect it to outer electrical circuits.
[0027] In the example of Fig. 3 the movable contact element 19 comprises a lamella 20 having a first end 21 fixed to the connection terminal 19' and a second cantilevered end 22 arranged between the first electrical contact 15 and the second electrical contact 16. In this case, in the first position the second end 22 is in contact with the first electrical contact 15 and in the second position the second end 22 is in contact with the second electrical contact 16.
[0028] The lamella 20 comprises two lateral portions 25 which connect the first end 21 to the second end 22 and a central portion 26 which extends from the second end 22 and is blocked against an abutment element 23 integral with the case 11. The central portion 26 is deformed elastically with respect to the lateral portions 25 to promote a snap movement of the second end 22 between the first electrical contact 15 and the second electrical contact 16 when pressure is exerted on the lamella 20.
[0029] Furthermore, in this configuration, it is possible to hold the second end 22 of the lamella 20 stably against one of the two electrical contacts 15, 16 when no pressure is exerted on the lamella 20. In the present example, when no pressure is exerted on the lamella 20 its second end 22 is held against the first electrical contact 15.
[0030] The microswitch 10 also comprises driving means 30 adapted to receive pressure from a member external to the microswitch 10 and operate on the movable contact element 19 to make it move from the first to the second position, or vice versa.
[0031] In this case, the driving means 30 comprise an operating head 31 external to the case 11 and an actuator pin 32, associated with the driving head 31, and adapted to exert pressure on the lamella 20 so as to move its second end 22 from the first position to the second position.
[0032] In this case, the elastic energy stored in the deformed central portion 26 of the lamella 20 allows a rapid snap movement of the second end 22 when the lamella 20 is pressed by the actuator pin 32.
[0033] The driving head 31 is slidably fixed to the case 11 and, preferably, between the driving head 31 and the case 11 there are first sealing means adapted to prevent the infiltration of water or dirt, or in general of liquids or external bodies, inside the case 11 and in particular inside the compartment 12. Preferably, the driving means are movable along an operating direction X. Even more preferably, the driving head 31 slides along the operating direction X.
[0034] By way of example, the first sealing means may comprise a collar 33 fixed to the case 11 by means of screws, joints or the like and which surrounds the driving head 31, also acting as a guide therefor.
[0035] Similarly, second sealing means are preferably also present between the actuator pin 32 and the case 11. By way of example, the second sealing means may comprise a flexible bellows 34 fixed to the case 11 and to the actuator pin 32.
[0036] The case 11 comprises at least two half-shells 35, 36 each provided with respective perimeter edges 37 and designed to be arranged in a mutually facing and overlapping position to delimit the compartment 12.
[0037] Preferably, the two half-shells 35, 36 are arranged in a mutually facing and overlapping position with respect to a joining plane P perpendicular to the operating direction X. Even more preferably, the peripheral edges 37 of the two half-shells 35, 36 lie substantially on the joining plane P or in a plane parallel to the joining plane P.
[0038] In this way the ultrasonic welding is more effective for joining the two half-shells 35, 36 as the energy of the ultrasonic vibrations transmitted to the two half-shells 35, 36 during the welding operation is constant throughout the development of the perimeter edges 27 of the two half-shells 35, 36.
[0039] Furthermore, even more preferably, each half-shell 35, 36 comprises an outer surface 53, 54 (Figs. 7 and 8) substantially parallel to the joining plane P. In this way, the distance between each point of this outer surface 53, 54 and the joining plane P is substantially constant for every point of the outer surfaces 53, 54. This feature also facilitates the ultrasonic welding operation of the two half-shells 35, 36 as it allows an arrangement of the welding member at ultrasound (sonotrode) parallel to the joining plane P and therefore to the perimeter edges 27.
[0040] In accordance with a peculiar aspect of the present invention, the two half-shells 35, 36 will be stably joined together by welding, which will preferably be ultrasonic welding.
[0041] In a particularly preferable manner, the welding of the perimeter edges 37 will be carried out throughout their entire development.
[0042] Advantageously, this allows for a hermetic coupling between the two half-shells 35, 36 even without the presence of a gasket or other additional sealing means.
[0043] In addition, this conformation allows the two half-shells 35, 36 to be joined without using fixing elements such as screws, rivets or others, and without providing for a specific shape or interlocking coupling therebetween.
[0044] In the preferred embodiments, each of the first and second electrical contacts 15, 16 comprises at least two contact areas independent of each other. In particular, said contact areas are distinct and physically separated from each other.
[0045] This conformation is possible thanks to the fact that the two half-shells 35, 36 are joined by ultrasonic welding.
[0046] In fact, the absence of fastening elements between the two half-shells 35, 36 and of gaskets allows for a compartment 12 inside the case 11 having a very large volume, suitable for containing large electrical contacts 15, 16.
[0047] Furthermore, thanks to this conformation the reliability of the contact between the lamellae 20 and the electrical contacts 15, 16 is also improved.
[0048] In particular, the presence of two distinct and separate contact areas for each electrical contact 15, 16 reduces the risk of an unstable, or not perfectly aligned, contact with the contact element 19.
[0049] Advantageously, in this way the microswitch 10 of the present invention may have compact dimensions and, at the same time, transmit currents of high values even higher than 5 A, either DC and AC.
[0050] In the current example, each electrical contact 15, 16 comprise a respective plate 40, 41 on which at least one conductive pad is fixed.
[0051] Preferably, two or more independent conductive pads 42, 43 are fixed to each plate 40, 41. In this way each electrical contact 15, 16 comprises at least two independent contact areas, defined by the conductive pads 42, 43.
[0052] Furthermore, the contact end 22 of the lamella 20 also comprises at least two contact areas independent of each other.
[0053] This feature also contributes to transmitting high value currents, even exceeding 5 A, either DC and AC.
[0054] As matter of fact, the two contact areas independent of each other reduce the risk of unstable contact or sticking between the lamellae 20 and the electrical contacts 15, 16. In this case, the contact end 22 of the lamellae 20 comprises at least two pairs of conductive pads 44, 45. In particular, two upper conductive pads 44 are designed to contact the pair of conductive pads 42 of the first electrical contact 15 and two lower conductive pads 45 are designed to contact the pair of conductive pads 43 of the second electrical contact 16.
[0055] Preferably, but not necessarily, the surface of the cross section S (Fig. 6) of each conductive pad 42, 43, 44, 45 is greater than 3.5 mm2.
[0056] It should be noted that the cross section S is the maximum cross section of a conductive pad 42, 43, 44, 45 with respect to a sectional plane parallel to the surface of the lamella 20 on which the conductive pad 42, 43, 44, 45 lies.
[0057] This configuration is also possible thanks to the fact that the two half-shells 35, 36 are joined by ultrasonic welding.
[0058] As matter of fact, the absence of fastening elements between the two half-shells 35, 36 and of gaskets allows to have a compartment 12 inside the case 11 having a very large volume, suitable for containing a contact end 22 of the lamella 20 of high dimensions. Advantageously, this feature also allows the microswitch 10 of the present invention to have compact dimensions and, at the same time, to transmit currents of high values even greater than 5 A, either DC and AC.
[0059] The person skilled in the art easily understands that the cross section S of the conductive pads 42, 43, 44, 45, which in the current example is circular in shape, may be of a different shape, for example square, polygonal, or defined by any combination of straight or curved sections, without thereby departing from the scope of protection of the present invention.
[0060] Preferably, the microswitch 10 further comprises fixing means 51, 52 adapted to allow the fixing of the microswitch 10 to an industrial machine or plant. In the example of Figs. 7 and 8 the fixing means are through fixing holes 51, 52.
[0061] The through fixing holes 51, 52 are advantageously obtained on one of the two half-shells 35, 36. Preferably, the through fixing holes 51, 52 are advantageously obtained only on one of the two half-shells 35, 36. In particular, the through fixing holes 51, 52 pass only through a single half-shell 36 and have a respective central axis parallel to the joining plane P. This is advantageous because, in use, a fixing screw inserted into a through fixing hole 51, 52 passes only through a single half-shell 36 and is never in contact with a perimeter edge 27 designed to be welded. This increases the resistance of the microswitch 10 of the present invention since the forces transmitted by the fixing screw to the half-shell 36 are applied in an area of the half-shell 36 having no solution of continuity.
1. A microswitch (10) comprising a case (11) formed by at least two half-shells (35, 36) mutually joined at respective perimeter edges (37) mutually facing and overlapping to define a compartment (12) which houses thereinside a first electrical contact (15), a second electrical contact (16) and a contact element (19) movable with respect to said first electrical contact (15) and to said second electrical contact (16); characterized in that said at least two half-shells (35, 36) are stably joined together by at least partial mutual welding of said respective
perimeter edges (37).
2. Microswitch as claimed in claim 1, characterized in that said at least two half-shells (35, 36) are stably joined together, along the entire development of said perimeter edges
(37) by said welding and in the absence of further fixing and/or joints and/or shape couplings
between said perimeter edges (37).
3. Microswitch as claimed in claim 1 or 2, characterized in that the perimeter edges (37) of said at least two half-shells (35, 36) are in direct mutual contact in the absence of gaskets placed therebetween.
4. Microswitch as claimed in any preceding claim, characterized in that said welding is ultrasonic welding.
5. Microswitch as claimed in any preceding claim, characterized in that said contact element (19) is movable in said compartment (12), and wherein said microswitch comprises driving means (30) adapted to move said contact element (19) between at least one first position wherein it is in electrical continuity with said
first electrical contact (15) and a second position wherein it is in electrical continuity with said second electrical
contact (16), and vice versa.
6. Microswitch as claimed in claim 5 and wherein said driving means (30) are movable along an operating direction (X) characterized in that said half-shells (35, 36) are arranged in a mutually facing and overlapping position with respect to a joining
plane (P) perpendicular to said operating direction (X).
7. Microswitch as claimed in any preceding claim, characterized in that at least one of said electrical contacts (15, 16) comprises at least two distinct and separate contact areas, adapted to be placed
in electrical continuity with each other by means of said contact element (19).
8. Microswitch as claimed in claim 7, characterized in that each of said electrical contacts (15, 16) comprises two contact areas.
9. Microswitch as claimed in claim 8, characterized in that each of said electrical contacts (15,16) comprises a respective plate (40, 41) on each of which two conductive pads (42, 43) are fixed, defining said contact areas.
10. Microswitch as claimed in claims 5 and 9, characterized in that said contact element (19) comprises a lamella (20) having a first end (21) fixed to said case (11) and a second cantilevered end (22) on which two upper conductive pads (44) are arranged, positioned to come into contact with the conductive pads (42) of said first electrical contact (15) when said contact element (19) is in said first position and two lower conductive pads (45) positioned to contact the conductive pads (43) of said second electrical contact (16) when said contact element (19) is in said second position.
11. Microswitch as claimed in claim 10, characterized in that said contact element (19) also comprises an abutment element (23) integral with said case (11), said lamella (20) comprising two lateral portions (25) connected to said first and second ends (21, 22) and an inner portion (26) which develops from said second end (22) and is held in a deformed configuration by said abutment element (23).
12. Microswitch as claimed in claim 11, characterized in that said driving means (30) comprise a driving head (31) external to said case (11) and an actuator pin (32) associated with said operating head (31) and adapted to exert a pressure on said lamella (20) suitable to move said second
end (22) of said lamella (20) from said first position to said second position.
13. Microswitch as claimed in claim 12, characterized by comprising sealing means (33, 34) associated with said driving means (30) and with said case (11) and adapted to avoid the infiltration of liquids or external bodies inside said compartment
(12).
14. Microswitch as claimed in any claim 10 to 13, characterized in that the surface of the cross section (S) of each of said conductive pads (42, 43, 44, 45) is greater than 3.5 mm2.
15. Microswitch as claimed in any claim 6 to 14 characterized in that at least one of said two half-shells (35, 36) comprises at least one through fixing hole (51, 52) passing through and having a central axis parallel to said joining plane (P).
16. Microswitch as claimed in any claim 6 to 15 characterized in that at least one of said two half-shells (35, 36) comprises at least one outer surface (53, 54) substantially parallel to said joining plane (P).
17. Process for manufacturing a microswitch (10) comprising a case (11) formed by at least two half-shells (35, 36) having respective perimeter edges (37) and suitable for defining a compartment (12) which houses at its inside a first electrical contact (15), a second electrical contact (16) and a contact element (19) movable with respect to said first electrical contact (15) and to said second electrical contact (16);
characterized by comprising a step of stable coupling of said half-shells (35, 36) wherein said half-shells (35, 36) are stably joined with each other by at least partial mutual welding of the respective perimeter edges (37).
characterized by comprising a step of stable coupling of said half-shells (35, 36) wherein said half-shells (35, 36) are stably joined with each other by at least partial mutual welding of the respective perimeter edges (37).